EP3465244A1 - Magneto-optical detecting apparatus and methods - Google Patents

Magneto-optical detecting apparatus and methods

Info

Publication number
EP3465244A1
EP3465244A1 EP17807444.9A EP17807444A EP3465244A1 EP 3465244 A1 EP3465244 A1 EP 3465244A1 EP 17807444 A EP17807444 A EP 17807444A EP 3465244 A1 EP3465244 A1 EP 3465244A1
Authority
EP
European Patent Office
Prior art keywords
optical
magneto
magnetic field
magnetic
rf
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP17807444.9A
Other languages
German (de)
French (fr)
Inventor
John B. Stetson
Arul Manickam
Peter G. Kaup
Gregory Scott Bruce
Wilbur Lew
Joseph W. Hahn
Nicholas Mauriello LUZOD
Kenneth Michael JACKSON
Jacob Louis SWETT
Peter V. Bedworth
Steven W. Sinton
Duc Huynh
Michael John DIMARIO
Jay T. HANSEN
Andrew Raymond MANDEVILLE
Bryan Neal FISK
Joseph A. VILLANI
Jon C. Russo
David Nelson COAR
Julie Lynne Miller
Anjaney Pramod KOTTAPALLI
Gary Edward MONTGOMERY
Margaret Miller SHAW
Stephen Sekelsky
James Michael Krause
Thomas J. Meyer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lockheed Corp
Lockheed Martin Corp
Original Assignee
Lockheed Corp
Lockheed Martin Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US201662343843P priority Critical
Priority to US201662343750P priority
Priority to US201662343839P priority
Priority to US201662343746P priority
Priority to US201662343602P priority
Priority to US201662343758P priority
Priority to US201662343842P priority
Priority to US201662343492P priority
Priority to US201662343818P priority
Priority to US201662343600P priority
Priority to US15/207,457 priority patent/US10338163B2/en
Priority to US201662360940P priority
Priority to US15/350,303 priority patent/US10281550B2/en
Priority to US15/376,244 priority patent/US10345395B2/en
Priority to US15/380,419 priority patent/US10345396B2/en
Priority to US15/380,691 priority patent/US20170343618A1/en
Priority to US15/382,045 priority patent/US20170343619A1/en
Priority to US15/437,222 priority patent/US10371765B2/en
Priority to US15/437,038 priority patent/US10359479B2/en
Priority to US15/440,194 priority patent/US20170343620A1/en
Priority to US15/443,422 priority patent/US20180348393A1/en
Priority to US15/446,373 priority patent/US20170343699A1/en
Priority to US15/454,162 priority patent/US10317279B2/en
Priority to US15/456,913 priority patent/US20170343621A1/en
Priority to US15/468,410 priority patent/US20180275224A1/en
Priority to US15/468,641 priority patent/US10330744B2/en
Priority to US15/468,397 priority patent/US10274550B2/en
Priority to US15/468,303 priority patent/US20180275206A1/en
Priority to US15/468,386 priority patent/US10145910B2/en
Priority to US15/468,289 priority patent/US10228429B2/en
Priority to US15/468,356 priority patent/US10408890B2/en
Application filed by Lockheed Corp, Lockheed Martin Corp filed Critical Lockheed Corp
Priority to PCT/US2017/035315 priority patent/WO2017210365A1/en
Publication of EP3465244A1 publication Critical patent/EP3465244A1/en
Application status is Pending legal-status Critical

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C39/00Aircraft not otherwise provided for
    • B64C39/02Aircraft not otherwise provided for characterised by special use
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00Arrangements or instruments for measuring magnetic variables
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00Arrangements or instruments for measuring magnetic variables
    • G01R33/02Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/032Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday, Cotton-Mouton effect

Abstract

A system for magnetic detection includes a magneto-optical defect center material including at least one magneto-optical defect center that emits an optical signal when excited by an excitation light; a radio frequency (RF) exciter system configured to provide RF excitation to the magneto-optical defect center material; an optical light source configured to direct the excitation light to the magneto-optical defect center material; and an optical detector configured to receive the optical signal emitted by the magneto-optical defect center material.

Description

MAGNETO-OPTICAL DETECTING APPARATUS AND METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/456,913 (Atty. Docket No. 111423-1537), filed March 13, 2017, entitled "Magneto-Optical Defect Center Magnetometer," which claims the benefit of priority to U.S. Provisional Patent Application No. 62/343,843 (Atty. Docket No. 111423-1144), filed May 31, 2016, entitled "DIAMOND NITROGEN VACANCY MAGNETOMETER," U.S. Provisional Patent Application No. 62/343,492 (Atty. Docket No. 111423-0119), filed May 31, 2016, entitled "LAYERED RF COIL FOR MAGNETOMETER", U.S. Non-Provisional Patent Application No. 15/380,691 (Atty. Docket No. 111423-1411), filed December 15, 2016, entitled "LAYERED RF COIL FOR MAGNETOMETER," U.S. Provisional Patent Application No. 62/343,746 (Atty. Docket No. 111423-1138), filed May 31, 2016, entitled "DNV DEVICE INCLUDING LIGHT PIPE WITH OPTICAL COATINGS", U.S. Provisional Patent Application No. 62/343,750 (Atty. Docket No. 111423-1139), filed May 31, 2016, entitled "DNV DEVICE INCLUDING LIGHT PIPE", U.S. Provisional Patent Application No. 62/343,758 (Atty. Docket No. 111423-1140), filed May 31, 2016, entitled "OPTICAL FILTRATION SYSTEM FOR DIAMOND MATERIAL WITH NITROGEN VACANCY CENTERS", U.S. Provisional Patent Application No. 62/343,818 (Atty. Docket No. 111423-1141), filed May 31, 2016, entitled "DIAMOND NITROGEN VACANCY MAGNETOMETER INTEGRATED STRUCTURE", U.S. Provisional Patent Application No. 62/343,600 (Atty. Docket No. 111423-1142), filed May 31, 2016, entitled "TWO-STAGE OPTICAL DNV EXCITATION", U.S. Non-Provisional Patent Application No. 15/382,045 (Atty. Docket No. 111423-1412), filed December 16, 2016, entitled "TWO-STAGE OPTICAL DNV EXCITATION," U.S. Provisional Patent Application No. 62/343,602 (Atty. Docket No. 111423-1143), filed May 31, 2016, entitled "SELECTED VOLUME CONTINUOUS ILLUMINATION MAGNETOMETER", and U.S. Non-Provisional Patent Application No. 15/380,419 (Atty. Docket No. 111423-1413), filed December 15, 2016, entitled "SELECTED VOLUME CONTINUOUS ILLUMINATION MAGNETOMETER," which are incorporated by reference herein in their entirety. This application is a continuation- in-part and claims the benefit of priority of U.S. Application No. 15/468,303 (Atty. Docket No. 111423-1496), filed March 24, 2017, entitled "Precision Adjustability of Optical Components in a Magnetometer Sensor," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/440,194 (Atty. Docket No. 111423-1611), filed February 23, 2017, entitled "Magneto-optical Defect Center Device Including Light Pipe with Optical Coatings," which claims the benefit of priority to U.S. Provisional Patent Application No. 62/343,750 (Atty. Docket No. 111423-1139), filed May 31, 2016, entitled "DNV DEVICE INCLUDING LIGHT PIPE," U.S. Provisional Patent Application No. 62/343,746 (Atty. Docket No. 111423-1138), filed May 31, 2016, entitled "DNV DEVICE INCLUDING LIGHT PIPE WITH OPTICAL COATINGS," and U.S. Provisional Patent Application No. 62/343,758 (Atty. Docket No. 111423-1140), filed May 31, 2016, entitled "OPTICAL FILTRATION SYSTEM FOR DIAMOND MATERIAL WITH NITROGEN VACANCY CENTERS," which are incorporated by reference herein in their entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/454,162 (Atty. Docket No. 111423-1420), filed March 9, 2017, entitled "Optical Filtration System for Diamond Material with Nitrogen Vacancy Centers," which claims the benefit of priority to U.S. Provisional Patent Application No. 62/343,758 (Atty. Docket No. 111423-1140), filed May 31, 2016, entitled "OPTICAL FILTRATION SYSTEM FOR

DIAMOND MATERIAL WITH NITROGEN VACANCY CENTERS," which are incorporated by reference herein in their entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/468,641 (Atty. Docket No. 111423-1654), filed March 24, 2017, entitled "Magnetometer with a Waveguide," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/207,457 (Atty. Docket No. 111423-1152), filed July 11, 2016, entitled "Multi-Frequency Excitation Schemes for High Sensitivity Magnetometry Measurement with Drift Error Compensation," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/437,038 (Atty. Docket No. 111423-1622), filed February 20, 2017, entitled "Efficient Thermal Drift Compensation in DNV Vector Magnetometry," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/468,356 (Atty. Docket No. 111423-1179), filed March 24, 2017, entitled "Pulsed RF Methods for Optimization of CW Measurements," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/468,397 (Atty. Docket No. 111423-1617), filed March 24, 2017, entitled "High Speed Sequential Cancellation for Pulsed Mode," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/468,386 (Atty. Docket No. 111423-1177), filed March 24, 2017, entitled "Photodetector Circuit Saturation Mitigation for Magneto-Optical High Intensity Pulses," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/468,289 (Atty. Docket No. 111423-1178), filed March 24, 2017, entitled "Apparatus and Method for Resonance Magneto-Optical Defect Center Material Pulsed Mode Referencing," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/468,410 (Atty. Docket No. 111423-1195), filed March 24, 2017, entitled "Generation of Magnetic Field Proxy Through RF Frequency Dithering," which is incorporated by reference herein in its entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/350,303 (Atty. Docket No. 111423- 1136), filed November 14, 2016, entitled "Spin Relaxometry Based Molecular Sequencing," which is incorporated by reference herein in its entirety. This application is a continuation-in- part and claims the benefit of priority of U.S. Application No. 15/443,422 (Atty. Docket No. 111423-1501), filed February 27, 2017, entitled "Array of UAVs with Magnetometers," which claims the benefit of priority to U.S. Provisional Application No. 62/343,842 (Atty. Docket No. 111423-1112), filed May 31, 2016, entitled "Array of UAVs with Magnetometers," U.S.

Provisional Application No. 62/343,839 (Atty. Docket No. 11 1423-1114), filed May 31, 2016, entitled "Buoy Array of Magnetometers," and of U.S. Provisional Application No. 62/343,600 (Atty. Docket No. 111423-1114), filed May 31, 2016, entitled "TWO-STAGE OPTICAL DNV EXCITATION," which are incorporated by reference herein in their entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/446,373 (Atty. Docket No. 111423-1502), filed March 1, 2017, entitled "Buoy Array of Magnetometers," which claims the benefit of priority to U.S. Provisional Application No. 62/343,842 (Atty.

Docket No. 111423-1112), filed May 31, 2016, entitled "Array of UAVs with Magnetometers," U.S. Provisional Application No. 62/343,839 (Atty. Docket No. 111423-1114), filed May 31, 2016, entitled "Buoy Array of Magnetometers," and of U.S. Provisional Application No. 62/343,600 (Atty. Docket No. 111423-1114), filed May 31, 2016, entitled "TWO-STAGE OPTICAL DNV EXCITATION," which are incorporated by reference herein in their entirety. This application is a continuation-in-part and claims the benefit of priority of U.S. Application No. 15/437,222 (Atty. Docket No. 111423-1619), filed February 20, 2017, entitled "Geolocation of Magnetic Sources Using Vector Magnetometer Sensors," which claims the benefit of priority to U.S. Provisional Patent Application No. 62/360,940 (Atty. Docket No. 111423-1156), filed July 11, 2016, entitled "Geolocation of Magnetic Sources Using Vector Magnetometer Sensors," which are incorporated by reference herein in their entirety. This application is a continuation- in-part and claims the benefit of priority of U.S. Application No. 15/376,244 (Atty. Docket No. 111423-1135), filed December 12, 2016, entitled "Vector Magnetometry Localization of Subsurface Liquids," which is incorporated by reference herein in its entirety.

FIELD

[0002] The present disclosure generally relates to magnetometers, and more particularly, to magneto-optical defect center magnetometers, such as diamond nitrogen vacancy (DNV) magnetometers.

BACKGROUND

[0003] A number of industrial applications, as well as scientific areas such as physics and chemistry can benefit from magnetic detection and imaging with a device that has extraordinary sensitivity, ability to capture signals that fluctuate very rapidly (bandwidth) all with a substantive package that is extraordinarily small in size, efficient in power and infinitesimal in volume.

[0004] Atomic-sized magneto-optical defect center elements, such as nitrogen-vacancy (NV) centers in diamond lattices, have excellent sensitivity for magnetic field measurement and enable fabrication of small magnetic sensors that can readily replace existing-technology (e.g., Hall- effect) systems and devices. The DNV sensors are maintained in room temperature and atmospheric pressure and can be even used in liquid environments. A green optical source (e.g., a micro-LED) can optically excite NV centers of the DNV sensor and cause emission of fluorescence radiation (e.g., red light) under off-resonant optical excitation. A magnetic field generated, for example, by a microwave coil can probe degenerate triplet spin states (e.g., with ms = -1, 0, +1) of the NV centers to split proportional to an external magnetic field projected along the NV axis, resulting in two spin resonance frequencies. The distance between the two spin resonance frequencies is a measure of the strength of the external magnetic field. A photo detector can measure the fluorescence (red light) emitted by the optically excited NV centers.

SUMMARY

[0005] Methods and systems are described for, among other things, a magneto-optical defect center magnetometer.

Magneto-Optical Defect Center Systems and Magnetometers

[0006] Some embodiments relate to a magneto-optical defect center magnetometer that includes an excitation source, a magneto-optical defect center element, a collection device, a top plate, a bottom plate, and a printed circuit board. The excitation source, the magneto-optical defect center element, and the collection device are each mounted to the printed circuit board.

[0007] In some implementations, the excitation source is positioned along a first axis relative to the printed circuit board and the collection device is positioned along a second axis relative to the printed circuit board. In some implementations, the magneto-optical defect center

magnetometer includes excitation source circuitry mounted to the printed circuit board proximate to the excitation source. In some implementations, the magneto-optical defect center

magnetometer includes collection device circuitry mounted to the printed circuit board proximate to the collection device. In some implementations, the magneto-optical defect center

magnetometer includes an RF element mounted to the printed circuit board and RF amplifier circuitry mounted to the printed circuit board proximate to the RF device. In some

implementations, the magneto-optical defect center magnetometer includes an optical waveguide assembly that includes an optical waveguide and at least one optical filter coating, and the optical waveguide assembly is configured to transmit light emitted from the diamond having nitrogen vacancies to the collection device. In some implementations, the optical waveguide comprises a light pipe. In some implementations, the optical filter coating transmits greater than about 99% of light with a wavelength of about 650 nm to about 850 nm. In some implementations, the optical filter coating transmits less than 0.1% of light with a wavelength of less than about 600 nm. In some implementations, the optical filter coating transmits greater than about 99% of light with a wavelength of about 650 nm to about 850 nm, and transmits less than 0.1% of light with a wavelength of less than about 600 nm. In some implementations, the optical filter coating is disposed on an end surface of the optical waveguide adjacent the collection device. In some implementations, a first optical filter coating is disposed on an end surface of the optical waveguide adjacent the collection device and a second optical filter coating is disposed on an end surface of the optical waveguide adjacent the diamond having nitrogen vacancies. In some implementations, the light pipe has an aperture with a size that is smaller than a size of the collection device. In some implementations, the light pipe has an aperture with a size greater than a size of a surface of the magneto-optical defect center element adjacent to the light pipe. In some implementations, the light pipe has an aperture with a size that is smaller than a size of the collection device and greater than a size of a surface of the magneto-optical defect center element adjacent the light pipe. In some implementations, the optical waveguide assembly further comprises an optical coupling material disposed between the light pipe and the magneto- optical defect center element, and the optical coupling material is configured to optically couple the light pipe to the magneto-optical defect center element. In some implementations, the optical waveguide assembly further comprises an optical coupling material disposed between the light pipe and the collection device, and the optical coupling material is configured to optically couple the light pipe to the collection device. In some implementations, an end surface of the light pipe adjacent to the magneto-optical defect center element extends in a plane parallel to a surface of the magneto-optical defect center element adjacent to the light pipe. In some implementations, the magneto-optical defect center magnetometer includes a second optical waveguide assembly and a second collection device, and the second optical waveguide assembly is configured to transmit light emitted from the magneto-optical defect center element to the second collection device. In some implementations, the magneto-optical defect center magnetometer includes an optical filter and the magneto-optical defect center element receives optical excitation based, at least in part, on generation of light corresponding to a first wavelength from the excitation source. The collection device is configured to receive at least a first portion of light

corresponding to a second wavelength and the optical filter is configured to provide at least a portion of light corresponding to the second wavelength to the collection device. In some implementations, the optical filter is further configured to transmit light corresponding to the first wavelength. In some implementations, light corresponding to the first wavelength comprises green and light corresponding to the second wavelength comprises red. In some

implementations, the optical filter comprises an optical coating, and wherein the optical coating comprises one or more layers configured to at least one of transmit or reflect light. In some implementations, the optical filter is disposed at least one of above, beneath, behind, or in front of the collection device. In some implementations, the optical filter is configured to enclose the magneto-optical defect center element. In some implementations, the optical filter is disposed at least one of above, beneath, behind, or in front of the magneto-optical defect center element. In some implementations, the collection device comprises a receiving ends, and wherein the receiving ends are disposed proximate to the magneto-optical defect center element. In some implementations, the collection device forms a gap, and wherein a predetermined dimension corresponding to the optical filter is configured to extend beyond a predetermined dimension corresponding to the gap. In some implementations, the magneto-optical defect center element is disposed between the receiving ends. In some implementations, the magneto-optical defect center magnetometer includes a RF excitation source configured to provide RF excitation to the magneto-optical defect center element. In some implementations, the optical filter comprises a dichroic filter. In some implementations, the excitation source, the magneto-optical defect center element, and the collection device are each aligned and positioned relative to the top plate, bottom plate, and printed circuit board by a corresponding two-point orientation system. In some implementations, the excitation source, the magneto-optical defect center element, and the collection device are positioned in a single plane. In some implementations, the magneto-optical defect center magnetometer includes a support element for the excitation source. In some implementations, the support element comprises one or more alignment pins for the two-point orientation system and wherein the top plate comprises one or more alignment openings for the two-point orientation system. In some implementations, the excitation source comprises one or more of a laser diode or a focusing lens. In some implementations, the support element comprises an asymmetrical alignment pin for the two-point orientation system and wherein the top plate comprises an asymmetrical alignment opening for the two-point orientation system. In some implementations, the excitation source comprises one or more of a laser diode or a focusing lens. In some implementations, the support element is formed of stainless steel, titanium, aluminum, carbon fiber, plastic, or a composite. In some implementations, the magneto-optical defect center magnetometer includes a support element for the collection device. In some implementations, the support element comprises one or more alignment pins for the two-point orientation system and wherein the top plate comprises one or more alignment openings for the two-point orientation system. In some implementations, the collection device comprises one or more of a light pipe or a photo diode. In some implementations, the support element comprises an asymmetrical alignment pin for the two-point orientation system and wherein the top plate comprises an asymmetrical alignment opening for the two-point orientation system. In some implementations, the collection device comprises one or more of a light pipe or a photo diode. In some implementations, the support element is formed of stainless steel, titanium, aluminum, carbon fiber, plastic, or a composite. In some implementations, the top plate is formed of stainless steel, titanium, aluminum, carbon fiber, or a composite. In some implementations, the bottom plate is formed of stainless steel, titanium, aluminum, carbon fiber, or a composite. In some implementations, the excitation source comprises an optical light source including a readout optical light source configured to provide optical excitation to the magneto- optical defect center element to transition relevant magneto-optical defect electrons to excited spin states in the magneto-optical defect center element and a reset optical light source configured to provide optical light to the magneto-optical defect center element to reset spin states in the magneto-optical defect center element to a ground state. The reset optical light source provides a higher power light than the readout optical light source. In some

implementations, the readout optical light source is a laser and the reset optical light source is a bank of LED flash-bulbs. In some implementations, the readout optical light source is an LED and the reset optical light source is a bank of LED flash-bulbs. In some implementations, the readout optical light source has a higher duty cycle than the reset optical light source. In some implementations, the excitation source comprises an optical light source including a readout optical light source configured to illuminate light in a first illumination volume of the magneto- optical defect center element and a reset optical light source configured to illuminate light in a second illumination volume of the magneto-optical defect center element The second illumination volume is larger than and encompassing the first illumination volume, and the reset optical light source provides a higher power light than the readout optical light source. In some implementations, the readout optical light source is a laser and the reset optical light source is a bank of LED flash-bulbs. In some implementations, the readout optical light source is an LED and the reset optical light source is a bank of LED flash-bulbs. In some implementations, the readout optical light source has a higher duty cycle than the reset optical light source. In some implementations, the magneto-optical defect center magnetometer includes a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center element, the RF excitation source including an RF feed connector and a plurality of coils, each connected to the RF feed connector, and adjacent the magneto-optical defect center element, the coils each having a spiral shape. In some implementations, the coils are arranged in layers one above another. In some implementations, the magneto-optical defect center magnetometer includes a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center element, the RF excitation source including an RF feed connector and a plurality of coils, each connected to the RF feed connector, and adjacent the magneto- optical defect center element, the coils arranged in layers one above another and to have a uniform spacing between each other. In some implementations, the coils each have a spiral shape. In some implementations, the magneto-optical defect center element is a diamond having nitrogen vacancies.

[0008] Some embodiments relate to a magneto-optical defect center magnetometer that includes a magneto-optical defect center element, an excitation source, a collection device, a top plate, a bottom plate, a printed circuit board, excitation source circuitry mounted to the printed circuit board proximate to the excitation source, and collection device circuitry mounted to the printed circuit board proximate to the collection device. The excitation source, the magneto- optical defect center element, and the collection device are each mounted to the printed circuit board.

[0009] In some implementations, the excitation source is positioned along a first axis relative to the printed circuit board and wherein the collection device is positioned along a second axis relative to the printed circuit board. In some implementations, the magneto-optical defect center magnetometer includes an RF element mounted to the printed circuit board and RF amplifier circuitry mounted to the printed circuit board proximate to the RF device. In some

implementations, the magneto-optical defect center magnetometer includes an optical waveguide assembly that includes an optical waveguide and at least one optical filter coating, wherein the optical waveguide assembly is configured to transmit light emitted from the diamond having nitrogen vacancies to the collection device. In some implementations, the magneto-optical defect center magnetometer includes an optical filter, and the magneto-optical defect center element receives optical excitation based, at least in part, on generation of light corresponding to a first wavelength from the excitation source. The collection device is configured to receive at least a first portion of light corresponding to a second wavelength, and the optical filter is configured to provide at least a portion of light corresponding to the second wavelength to the collection device. In some implementations, the excitation source, the magneto-optical defect center element, and the collection device are each aligned and positioned relative to the top plate, bottom plate, and printed circuit board by a corresponding two-point orientation system. In some implementations, the excitation source comprises an optical light source including a readout optical light source configured to provide optical excitation to the magneto-optical defect center element to transition relevant magneto-optical defect electrons to excited spin states in the magneto-optical defect center element and a reset optical light source configured to provide optical light to the magneto-optical defect center element to reset spin states in the magneto- optical defect center element to a ground state. The reset optical light source provides a higher power light than the readout optical light source. In some implementations, the excitation source comprises an optical light source including a readout optical light source configured to illuminate light in a first illumination volume of the magneto-optical defect center element and a reset optical light source configured to illuminate light in a second illumination volume of the magneto-optical defect center element. The second illumination volume is larger than and encompassing the first illumination volume, and the reset optical light source provides a higher power light than the readout optical light source. In some implementations, the magneto-optical defect center magnetometer includes a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center element, the RF excitation source including an RF feed connector and a plurality of coils, each connected to the RF feed connector, and adjacent the magneto-optical defect center element, the coils each having a spiral shape. In some implementations, the magneto-optical defect center magnetometer includes a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center element, the RF excitation source including an RF feed connector and a plurality of coils, each connected to the RF feed connector, and adjacent the magneto-optical defect center element, the coils arranged in layers one above another and to have a uniform spacing between each other. In some implementations, the magneto-optical defect center element is a diamond having nitrogen vacancies.

[0010] Some embodiments relate to a magneto-optical defect center magnetometer having a magneto-optical defect center element, an excitation source, a collection device, an RF element, a top plate, a bottom plate, a printed circuit board, excitation source circuitry mounted to the printed circuit board proximate to the excitation source, collection device circuitry mounted to the printed circuit board proximate to the collection device, and RF amplifier circuitry mounted to the printed circuit board proximate to the RF device. The excitation source, the magneto- optical defect center element, the collection device, and the RF element are each mounted to the printed circuit board and the excitation source is positioned along a first axis relative to the printed circuit board and the collection device is positioned along a second axis relative to the printed circuit board.

[0011] In some implementations, the magneto-optical defect center magnetometer includes an optical waveguide assembly that includes an optical waveguide and at least one optical filter coating, and the optical waveguide assembly is configured to transmit light emitted from the diamond having nitrogen vacancies to the collection device. In some implementations, the magneto-optical defect center magnetometer includes an optical filter. The magneto-optical defect center element receives optical excitation based, at least in part, on generation of light corresponding to a first wavelength from the excitation source, the collection device is configured to receive at least a first portion of light corresponding to a second wavelength, and the optical filter is configured to provide at least a portion of light corresponding to the second wavelength to the collection device. In some implementations, the excitation source, the magneto-optical defect center element, and the collection device are each aligned and positioned relative to the top plate, bottom plate, and printed circuit board by a corresponding two-point orientation system. In some implementations, the excitation source comprises an optical light source including a readout optical light source configured to provide optical excitation to the magneto-optical defect center element to transition relevant magneto-optical defect electrons to excited spin states in the magneto-optical defect center element and a reset optical light source configured to provide optical light to the magneto-optical defect center element to reset spin states in the magneto-optical defect center element to a ground state. The reset optical light source provides a higher power light than the readout optical light source. In some

implementations, the excitation source comprises an optical light source including a readout optical light source configured to illuminate light in a first illumination volume of the magneto- optical defect center element and a reset optical light source configured to illuminate light in a second illumination volume of the magneto-optical defect center element. The second illumination volume is larger than and encompassing the first illumination volume, and the reset optical light source provides a higher power light than the readout optical light source. In some implementations, the magneto-optical defect center magnetometer includes a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center element, the RF excitation source including an RF feed connector and a plurality of coils, each connected to the RF feed connector, and adjacent the magneto-optical defect center element, the coils each having a spiral shape. In some implementations, the magneto-optical defect center magnetometer includes a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center element, the RF excitation source including an RF feed connector and a plurality of coils, each connected to the RF feed connector, and adjacent the magneto-optical defect center element, the coils arranged in layers one above another and to have a uniform spacing between each other. In some implementations, the magneto-optical defect center element is a diamond having nitrogen vacancies.

[0012] According to some embodiments, there is a system for magnetic detection that can include a housing, a magneto-optical defect center material including at least one magneto- optical defect center that emits an optical signal when excited by an excitation light, a radio frequency (RF) exciter system configured to provide RF excitation to the magneto-optical defect center material, an optical light source configured to direct the excitation light to the magneto- optical defect center material, and an optical detector configured to receive the optical signal emitted by the magneto-optical defect center material based on the excitation light and the RF excitation. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0013] According to some embodiments, the housing further comprises: a top plate; a bottom plate; and at least one side plate. The top plate, the bottom plate, and the at least one side plate form an enclosure that contains the magneto-optical defect center material, the RF exciter system, the optical light source, and the optical detector.

[0014] According to some embodiments, the top plate is made from Noryl, the bottom plate is made from copper, stainless steel, aluminum or copper, and the at least one side plate is made from Noryl.

[0015] According to some embodiments, the housing further comprises one or more separation plates configured to isolate at least one of the magneto-optical defect center material, the RF exciter system, the optical light source, and the optical detector within the housing. [0016] According to some embodiments, the housing further comprises a main plate provided between the side plate and the bottom plate. The magneto-optical defect center material, the RF exciter system, the optical light source, and the optical detector are mounted to the main plate.

[0017] According to some embodiments, the main plate is made from Noryl.

[0018] According to some embodiments, the main plate can include a plurality of holes positioned to allow the magneto-optical defect center material, the RF exciter system, the optical light source, and the optical detector to be mounted to the main plate in a plurality of locations on the main plate.

[0019] According to some embodiments, the system for magnetic detection can further include a gasket configured to hermetically seal the top plate, the bottom plate, the at least one side plate, and the main plate together.

[0020] According to some embodiments, the system for magnetic detection can further include a hydrogen absorber positioned within the housing, the hydrogen absorber configured to absorb hydrogen released by materials used in the system for magnetic detection.

[0021] According to some embodiments, the system for magnetic detection can further include a nitrogen cooling system configured to cool or otherwise reduce thermal loading on components of the system for magnetic detection. The nitrogen cooling system may be in thermal

communication with the at least one of the top plate or the bottom plate including the cooling fins such that heat removed by the nitrogen cooling system is convectively dissipated to atmosphere via the cooling fins.

[0022] According to some embodiments, at least one of the top plate or the bottom plate include cooling fins can be configured to thermally dissipate heat transferred to the at least one of the top plate or the bottom plate.

[0023] According to some embodiments, the system for magnetic detection can further include a nitrogen cooling system configured to cool or otherwise reduce thermal loading on components of the system for magnetic detection. The nitrogen cooling system is in thermal communication with the at least one of the top plate or the bottom plate including the cooling fins such that heat removed by the nitrogen cooling system is convectively dissipated to atmosphere via the cooling fins.

[0024] According to some embodiments, the system for magnetic detection can further include a controller programmed to: receive an indication of a frequency of the excitation light; receive an indication of a frequency of the optical signal emitted by the magneto-optical defect center material; and determine a magnitude of an external magnetic field based at least in part on a comparison between the frequency of the excitation light and the frequency of the optical signal emitted by the magneto-optical defect center material. The controller may be further

programmed to determine a direction of the external magnetic field based at least in part on a comparison between the frequency of the excitation light and the frequency of the optical signal emitted by the magneto-optical defect center material.

[0025] According to some embodiments, the RF exciter system can include a radio frequency (RF) source; a radio frequency (RF) input; a radio frequency (RF) ground; and a microstrip line electrically connected to the RF input and short circuited to the RF ground adjacent the magneto- optical defect center material. The controller is further programmed to control the RF source such that a standing wave RF field is created in the magneto-optical defect center material.

[0026] According to some embodiments, the RF exciter system can include an RF feed connector; and a metallic material coated on the magneto-optical defect center material and electrically connected to the RF feed material.

[0027] According to some embodiments, the RF exciter system can further include a circuit board comprising an insulating board and conductive traces formed on the insulating board, the conductive traces electrically connecting the RF feed connector to the metallic material.

[0028] According to some embodiments, the system for magnetic detection can further include a plurality of magnets configured to provide a bias magnetic field to the magneto-optical defect center material; a ring magnet holder comprising: an outer ring with an outside surface, and a plurality of holders extending from the ring, wherein the plurality of holders are configured to hold the plurality of magnets in a same orientation with respect to one another; and a mount comprising an inside surface, wherein the outside surface of the outer ring slides along the inside surface of the mount.

[0029] According to some embodiments, the ring magnet holder can further include a fixation member configured to secure the ring magnet holder in a location within the mount.

[0030] According to some embodiments, the mount can include a through-hole configured to allow the excitation light to pass through the through-hole of the mount.

[0031] According to some embodiments, the system for magnetic detection can further include a slot configured to adjust the optical light source in a respective linear direction relative to the main plate; a lens; and a drive screw mechanism configured to adjust a position of the lens relative to the optical light source.

[0032] According to some embodiments, the system for magnetic detection can further include a plurality of drive screw mechanisms configured to adjust a position of the lens relative to the optical light source, each of the plurality of drive screw mechanisms configured to adjust in a direction orthogonal to the other drive screw mechanisms.

[0033] According to some embodiments, the system for magnetic detection can further include a waveplate assembly comprising: a waveplate, a mounting disk adhered to the waveplate, and a mounting base configured such that the mounting disk can rotate relative to the mounting base around an axis of the waveplate. The excitation light emitted by the optical light source can be directed through the waveplate before the excitation light is directed to the magneto-optical defect center material.

[0034] According to some embodiments, the optical light source can emit green light, and the magneto-optical defect center material can include a plurality of defect centers in a plurality of orientations. According to some embodiments, the system for magnetic detection can further include a half-wave plate, through which at least some of the green light passes, rotating a polarization of such green light to thereby provide an orientation to light waves emitted from the half-wave plate, the half-wave plate capable of being orientated relative to the defect centers in a plurality of orientations. The orientation of the light waves can coincide with an orientation of the defect centers, thereby imparting substantially increased energy transfer to the defect center with coincident orientation while imparting substantially decreased energy transfer to the defect centers that are not coincident. The excitation light emitted by the optical light source can be directed through the half-wave plate before the excitation light is directed to the magneto-optical defect center material.

[0035] According to some embodiments, the system for magnetic detection can further include a beam former in electrical communication with the RF excitation source; and an array of Vivaldi antenna elements in electrical communication with the beam former. The magneto- optical defect center material can be positioned in a far field of the array of Vivaldi antenna elements. The array of Vivaldi antenna elements can generate a RF magnetic field that is uniform over the magneto-optical defect center material, wherein the optical light source transmits excitation light at a first wavelength to the magneto-optical defect center material to detect a magnetic field based on a measurement of excitation light at a second wavelength that is different from the first wavelength.

[0036] According to some embodiments, the system for magnetic detection can further include a mount base. The RF exciter system can include a radio frequency circuit board configured to generate a radio frequency field around the magneto-optical defect center material. The magneto-optical defect center material and the radio frequency circuit board can be mounted to the mount base. The mount base can be configured to be fixed to the housing in a plurality of orientations.

[0037] According to some embodiments, in each of the plurality of orientations, the excitation light can enter the magneto-optical defect center material in a respective side of the magneto- optical defect center material.

[0038] According to some embodiments, the excitation light can be injected into a first side of the magneto-optical defect center material when the mount base is fixed in a first orientation in the plurality of orientations, and the excitation light can be injected into a second side of the magneto-optical defect center material when the mount base is fixed in a second orientation in the plurality of orientations.

[0039] According to some embodiments, when the mount base is fixed in the first orientation, a portion of the excitation light can pass through the magneto-optical defect center material and can be detected by a second light sensor, and when the mount base is fixed in the second orientation, a portion of the excitation light cannot detected by the second light sensor.

Precision Adjustability of Optical Components in a Magnetometer Sensor

[0040] In order to adjust optical excitation through a plurality of lenses to magneto-optical defect center materials, the relative position of an optical excitation assembly material can be controlled. During manufacture of a sensor system, there may be small variations in how a magneto-optical defect center material is mounted or in the tolerances of sensor components including the lenses and spacers such that adjustment is needed after assembly to adjust and focus the generated optical excitation. In some implementations, the generated optical excitation is laser light from a laser diode. In some implementations, an initial calibration is done on the sensor system to adjust the relative position of the optical excitation assembly to a base structure to benefit the final intended purpose of the sensor. [0041] According to some embodiments, there is an optical excitation assembly for attachment to a base structure that can include a defect center in a magneto-optical defect center material in a fixed position relative to the base structure, a slot configured to adjust the optical excitation assembly in a respective linear direction relative to the base structure, an optical excitation source, a lens, and a drive screw mechanism. The drive screw mechanism can be configured to adjust a position of the lens relative to the optical excitation source. In some implementations, the optical excitation assembly can further include a plurality of drive screw mechanisms, where the plurality of drive screw mechanisms are configured to adjust a position of the lens relative to the optical excitation source. In some implementations, each of the plurality of drive screw mechanisms may be configured to adjust in a direction orthogonal to the other drive screw mechanisms. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0042] According to some embodiments, the optical excitation assembly can further include a shim configured to adjust the optical excitation assembly in a linear direction relative to the base structure. In some embodiments, the optical excitation assembly can further include a magneto- optical defect center material with defect centers. The light from the optical excitation source can be directed through the lens into the magneto-optical defect center material with defect centers.

[0043] According to some embodiments, the optical excitation assembly can further include a half-wave plate assembly. The half-wave plate assembly can include a half-wave plate, a mounting disk adhered to the half-wave plate, and a mounting base configured such that the mounting disk can rotate relative to the mounting base around an axis of the half-wave plate. In some embodiments, the lens can be configured to direct light from the optical excitation source through the half-wave plate before the light is directed to the magneto-optical defect center material. In some implementations, the optical excitation assembly can further include a pin adhered to the mounting disk. The mounting base can include a mounting slot configured to receive the pin. The pin can slide along the mounting slot and the mounting disk can rotate relative to the mounting base around the axis of the half-wave plate, with the axis perpendicular to a length of the mounting slot.

[0044] According to some embodiments, the optical excitation assembly can further include a screw lock inserted through the slot and configured to prevent relative motion of the optical excitation assembly to the base structure when tightened. [0045] According to some embodiments, there is an assembly for attachment to a base structure that can include a slot configured to adjust the assembly in a respective linear direction relative to the base structure, an optical excitation source, a plurality of lenses, an adjustment mechanism, and a magneto-optical defect center material with defect centers. The adjustment mechanism can be configured to adjust a position of the plurality of lenses relative to the optical excitation source. The light from the optical excitation source can be directed through the plurality of lenses into the magneto-optical defect center material with defect centers. In some embodiments, the assembly can be configured to direct light from the optical excitation source through a half-wave plate before the light is directed to the magneto-optical defect center material.

[0046] According to some embodiments, the assembly can further include a mounting disk adhered to the half-wave plate. The mounting disk can be configured to rotate relative to the mounting base around the axis of the half-wave plate. In some embodiments, the assembly can further include a pin adhered to the mounting disk. The mounting base can include a mounting slot configured to receive the pin. The pin can slide along the slot and the mounting disk can rotate relative to the mounting base around the axis of the half-wave plate, the axis perpendicular to a length of the slot.

[0047] According to some embodiments, the optical excitation source can be one of a laser diode or a light emitting diode.

[0048] According to some embodiments, the assembly may further include a screw lock inserted through the slot. The screw lock can be configured to prevent relative motion of the optical excitation assembly to the base structure when tightened. A second screw lock attached to the mounting disk can be configured to prevent rotation of the mounting disk relative to the mounting base when tightened.

[0049] According to some embodiments, the lens of the assembly can be configured to direct light from the optical excitation source through the half-wave plate before the light is directed to the magneto-optical defect center material.

[0050] According to some embodiments, a sensor assembly can include a base structure and an optical excitation assembly. The optical excitation assembly can include an optical excitation means, for providing optical excitation through a plurality of lenses, magneto-optical defect center material comprising a plurality of magneto-optical defect centers, and an adjustment means, for adjusting the location of the provided optical excitation where it reaches the magneto- optical defect center material.

[0051] According to some embodiments, there is a method of adjusting an optical excitation assembly relative to a base structure that can include adjusting an optical excitation source in a respective linear direction relative to the base structure using a slot and adjusting a position of a lens in the optical excitation assembly relative to the optical excitation source using a drive screw mechanism. The adjusting the optical excitation source and adjusting the position of a lens may direct light from the optical excitation source to a defect center in a magneto-optical defect center that is in a fixed position relative to the base structure. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0052] According to some embodiments, the method can further include adjusting the position of the lens in the optical excitation assembly using a plurality of drive screw mechanisms. Each of the plurality of drive screw mechanisms may adjust in a direction orthogonal to the other drive screw mechanisms. In some embodiments, the method may further include adjusting the optical excitation assembly in a linear direction relative to the base structure using a shim. In some implementations, the method may direct the light from the optical excitation source through the lens to the defect center.

[0053] According to some embodiments, the method can further include rotating a half-wave plate attached to the optical excitation assembly around an axis of the half-wave plate using a half-wave plate assembly. The half-wave plate assembly can include a mounting disk adhered to the half-wave plate. In some embodiments, the method may further include sliding a pin adhered to the mounting disk along a mounting slot in the mounting disk, the axis of the half-wave plate perpendicular to a length of the mounting slot when rotating the half-wave plate. In some embodiments, the method may further include tightening a screw lock inserted through the slot to prevent relative motion of the optical excitation assembly to the base structure.

Use of Waveplates in a Magnetometer Sensor

[0054] In order to tune the magnetic field measurement for certain axes of the magneto-optical defect center materials the polarization of light entering the magneto-optical defect center material may be controlled. During manufacture of a sensor system, there may be small variations in how a magneto-optical defect center material is mounted to the sensor such that axes have deviation in orientation as well as inherent differences between different magneto- optical defect center materials. In such manufacturing, a calibration can be conducted by adjusting the polarization of the light to benefit the final intended purpose of the sensor.

[0055] According to some embodiments, there is a sensor that can include an optical excitation source emitting green light, a magneto-optical defect center material with defect centers in a plurality of orientations, and a half-wave plate. At least some of the green light may pass through the half-wave plate, rotating a polarization of such green light to thereby provide an orientation to the light waves emitted from the half-wave plate. The half-wave plate may be capable of being orientated relative to the defect centers in a plurality of orientations, wherein the orientation of the light waves coincides with an orientation of the defect centers, thereby imparting

substantially increased energy transfer to the defect center with coincident orientation while imparting substantially decreased energy transfer to the defect centers that are not coincident. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0056] According to some embodiments, there is a sensor that can include a waveplate assembly, an optical excitation source and a magneto-optical defect center material with defect centers. The waveplate assembly can include a waveplate, mounting base, and a mounting disk. The mounting disk can be adhered to the waveplate. The mounting base can be configured such that the mounting disk can rotate relative to the mounting base around an axis of the waveplate. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0057] According to some embodiments, the sensor can be configured to direct light from the optical excitation source through the waveplate before the light is directed to the magneto-optical defect center material. In some embodiments, the sensor can further comprise a pin adhered to the mounting disk. The mounting base can comprise a slot configured to receive the pin, the pin can slide along the slot and the mounting disk can rotate relative to the mounting base around the axis of the waveplate with the axis perpendicular to a length of the slot. In some embodiments, the magneto-optical defect center material with defect centers can be comprised of a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers. In some embodiments, the optical excitation source can be one of a laser (e.g., a laser diode) or a light emitting diode. In some embodiments, the sensor can further comprise a screw lock attached to the mounting disk. The screw lock can be configured to prevent rotation of the mounting disk relative to the mounting base when tightened. In some embodiments, the sensor can further comprise a controller electrically coupled to the waveplate assembly. The controller can be configured to control an angle of the rotation of the waveplate relative to the mounting base.

[0058] According to some embodiments, there is an assembly that can include a half-wave plate, a mounting base, an optical excitation source, and a magneto-optical defect center material with defect centers. The mounting base can be configured such that the half-wave plate can rotate relative to the mounting base around an axis of the half-wave plate. In some embodiments, the assembly can further comprise a pin adhered to the mounting disk. The mounting base can comprise a slot configured to receive the pin, the pin can slide along the slot and the mounting disk can rotate relative to the mounting base around the axis of the half-wave plate with the axis perpendicular to a length of the slot. In some embodiments, the magneto-optical defect center material with defect centers can be comprised of a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers. In some embodiments, the optical excitation source can be one of a laser (e.g., a laser diode) or a light emitting diode. In some embodiments, the assembly can further comprise a screw lock attached to the mounting disk. The screw lock can be configured to prevent rotation of the mounting disk relative to the mounting base when tightened. In some embodiments, the assembly can further comprise a controller electrically coupled to the half-wave plate assembly. The controller can be configured to control an angle of the rotation of the half-wave plate relative to the mounting base. According to some

embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0059] According to some embodiments, there is a sensor assembly that can include a mounting base and a half-wave plate assembly. The half-wave plate assembly can further comprise a half-wave plate, an optical excitation means for providing optical excitation through the half-wave plate, a magneto-optical defect center material comprising a plurality of magneto- optical defect centers, and a detector means, for detecting optical radiation. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0060] According to some embodiments, there is a sensor assembly that can include a half- wave plate, a mounting base, an optical excitation source, and a magneto-optical defect center material with defect centers. The mounting base can be configured such that the half-wave plate can rotate relative to the mounting base around an axis of the half-wave plate. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0061] According to some embodiments, there is a sensor that can include an optical excitation source emitting light, a magneto-optical defect center material with defect centers in a plurality of orientations, and a polarization controller. The polarization controller may control the polarization orientation of the light emitted from the optical excitation source, wherein the polarization orientation coincides with an orientation of the defect centers, thereby imparting substantially increased energy transfer to the defect center with coincident orientation while imparting substantially decreased energy transfer to the defect centers that are not coincident. In some embodiments, the magneto-optical defect center material with defect centers comprises a nitrogen vacancy (NV) diamond material comprising one or more NV centers. In some embodiments, the optical excitation source is one of a laser diode or a light emitting diode.

[0062] According to some embodiments, there is a sensor assembly that can include a mounting base and an optical excitation transmission assembly. The optical excitation transmission assembly may further comprise an optical excitation means for providing optical excitation, a polarization means, for changing a polarization of light received from the optical excitation means, a magneto-optical defect center material comprising one or more magneto- optical defect centers, and a detector means, for detecting optical radiation. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material.

Magneto-Optical Defect Center Material Holder

[0063] According to some embodiments, there is a magnetometer that can include a housing; a light source configured to provide excitation light; a magneto-optical defect center material with at least one defect center that emits light when excited by the excitation light; a light sensor configured to receive the emitted light; a radio frequency circuit board configured to generate a radio frequency field around the magneto-optical defect center material; and a mount base, wherein the magneto-optical defect center material and the radio frequency circuit board are mounted to the mount base, and wherein the mount base is configured to be fixed to the housing in a plurality of orientations. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0064] According to some embodiments, in each of the plurality of orientations, the excitation light can enter the magneto-optical defect center material in a respective side of the magneto- optical defect center material.

[0065] According to some embodiments, the excitation light can be injected into a first side of the magneto-optical defect center material when the mount base is fixed in a first orientation in the plurality of orientations, and the excitation light can be injected into a second side of the magneto-optical defect center material when the mount base is fixed in a second orientation in the plurality of orientations.

[0066] According to some embodiments, when the mount base is fixed in the first orientation, a portion of the excitation light can pass through the magneto-optical defect center material and is detected by a second light sensor, and when the mount base is fixed in the second orientation, a portion of the excitation light cannot detected by the second light sensor.

[0067] According to some embodiments, the mount base can be configured to be fixed to the housing in the plurality of orientations via a plurality of sets of fixation holes.

[0068] According to some embodiments, each of the fixation holes of the sets of fixation holes can include a threaded hole.

[0069] According to some embodiments, the mount base can be configured to be fixed to the housing via at least one threaded shaft.

[0070] According to some embodiments, each set of the plurality of sets of fixation holes can include two fixation holes.

[0071] According to some embodiments, each set of the plurality of sets of fixation holes can be two fixation holes.

[0072] According to some embodiments, the light source and the light sensor can be fixed to the housing.

[0073] According to some embodiments, the magnetometer can further include a processor configured to: receive an indication of a frequency of the excitation light; receive an indication of a frequency of the emitted light; and determine a magnitude of an external magnetic field based at least in part on a comparison between the frequency of the excitation light and the frequency of the emitted light. [0074] According to some embodiments, the processor can be further configured to determine a direction of the external magnetic field based at least in part on a comparison between the frequency of the excitation light and the frequency of the emitted light.

[0075] According to some embodiments, the processor can be further configured to determine the magnitude of the external magnetic field based in part on the radio frequency field.

[0076] According to some embodiments, the radio frequency field can have a frequency that is time-varying.

[0077] According to some embodiments, a frequency of the excitation light can be different than a frequency of the emitted light.

[0078] According to some device embodiments, the magneto-optical defect center material can include at least one defect center that transmits emitted light when excited by excitation light. The devices may also include a radio frequency circuit board that can be configured to generate a radio frequency field around the magneto-optical defect center material. The devices may further include a mount base. The magneto-optical defect center material and the radio frequency circuit board can be mounted to the mount base. The mount base may be configured to be fixed to a housing in a plurality of orientations.

Vacancy Center Material with Highly Efficient RF Excitation

[0079] According to some embodiments, there is a system for magnetic detection that can include a magneto-optical defect center material comprising a plurality of magneto-optical defect centers; an optical light source configured to provide optical excitation to the magneto-optical defect center material; an optical detector configured to receive an optical signal emitted by the magneto-optical defect center material; and a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center material, the RF excitation source comprising: an RF feed connector; and a metallic material coated on the magneto-optical defect center material and electrically connected to the RF feed connecter. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0080] According to some embodiments, the RF excitation source can further include a circuit board comprising an insulating board and conductive traces formed on the insulating board, the conductive traces electrically connecting the RF feed connector to the metallic material. [0081] According to some embodiments, the conductive traces can include a first trace having a first width and a first length, and a second trace contacting the first trace, the second trace having a second width and a second length different from the first width and the first length.

[0082] According to some embodiments, the second width can match the width of the magneto-optical defect center material.

[0083] According to some embodiments, the metallic material can be at least one of gold, copper, silver, or aluminum.

[0084] According to some embodiments, the RF excitations source can further include metallic material is coated at least over a top surface and a bottom surface of the magneto-optical defect center material.

[0085] According to some embodiments, there is a system for magnetic detection that can include a magneto-optical defect center material comprising a plurality of magneto-optical defect centers; a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center material; an optical detector configured to receive an optical signal emitted by the magneto-optical defect center material; and an optical light source comprising: a readout optical light source configured to provide optical excitation to the magneto-optical defect center material to transition relevant magneto-optical defect center electrons to excited spin states in the magneto-optical defect center material; and a reset optical light source configured to provide optical light to the magneto-optical defect center material to reset spin states in the magneto-optical defect center material to a ground state, wherein the RF excitation light source comprises a block portion having a support portion which supports the magneto-optical defect center material, the block portion having a first wall portion adjacent to and on one side of the support portion and a second wall portion adjacent to and on another side of the support portion opposite to the first side, a face of the second wall portion being slanted with respect to a face of the first wall portion so as to allow light emitted by the readout optical light source and the reset optical light source to be directed to the magneto-optical defect center material. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0086] According to some embodiments, the block portion can be formed of an electrically and thermally conductive material. [0087] According to some embodiments, the block portion can be formed of one of copper or aluminum.

[0088] According to some embodiments, the block portion can be a heat sink.

[0089] According to some embodiments, the block portion can have side holes and bottom holes to allow for side mounting and bottom mounting, respectively, of the block portion.

[0090] According to some embodiments, the RF excitation source can include an RF feed connector; and a metallic material coated on the magneto-optical defect center material and electrically connected to the RF feed connecter.

[0091] According to some embodiments, upon the RF feed connector can be driven by an RF signal, the metallic material shorts to the block portion.

Standing-Wave Radio Frequency Exciter

[0092] According to some embodiments, there is a system for magnetic detection that can include a magneto-optical defect center material comprising a plurality of magneto-optical defect centers; a radio frequency (RF) exciter system configured to provide RF excitation to the magneto-optical defect center material; an optical light source configured to direct excitation light to the magneto-optical defect center material; and an optical detector configured to receive an optical signal emitted by the magneto-optical defect center material based on the excitation light and the RF excitation. The RF exciter system can include a RF source; a controller configured to control the RF source; the RF input; a RF ground; and a microstrip line electrically connected to the RF input and short circuited to the RF ground adjacent the magneto-optical defect center material. The controller is configured to control the RF source such that a standing wave RF field is created in the magneto-optical defect center material.

[0093] According to some embodiments, the microstrip line can include conductive traces comprising a first trace having a first width and a first length, and a second trace contacting the first trace, the second trace having a second width and a second length different from the first width and the first length.

[0094] According to some embodiments, the second trace can have an impedance of less than 10 Ω.

[0095] According to some embodiments, the impedance of the first trace can match a system impedance.

[0096] According to some embodiments, the first trace can have an impedance of about 50 Ω. [0097] According to some embodiments, the microstrip line can include a metallic material coated at least over a top surface, a bottom surface, and a side surface of the magneto-optical defect center material, and is short circuited to the RF ground adjacent the magneto-optical defect center material.

[0098] According to some embodiments, the microstrip line can further include a metallic material coated at least over a top surface, a bottom surface, and a side surface of the magneto- optical defect center material, and short circuited to the RF ground adjacent the magneto-optical defect center material.

[0099] According to some embodiments, the microstrip line can have a wavelength of about a quarter wavelength of an RF carrier frequency.

[0100] According to some embodiments, there is radio frequency (RF) exciter system that can provide RF excitation to a magneto-optical defect center material comprising a plurality of magneto-optical defect centers. The RF exciter system include a RF input; a controller configured to control an RF source to apply a RF signal to the RF input; a RF ground; and a microstrip line electrically connected to the RF input and short circuited to the RF ground adjacent a magneto-optical defect center material; wherein the controller is configured to control the RF source to apply an RF signal to the RF input such that a standing wave RF field is created in the magneto-optical defect center material. According to some embodiments, the magneto- optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0101] According to some embodiments, the microstrip line can include conductive traces comprising a first trace having a first width and a first length, and a second trace contacting the first trace, the second trace having a second width and a second length different from the first width and the first length.

[0102] According to some embodiments, the microstrip line can include a metallic material coated at least over a top surface, a bottom surface, and a side surface of the magneto-optical defect center material, and is short circuited to the RF ground adjacent the magneto-optical defect center material.

[0103] According to some embodiments, the microstrip line can have a wavelength of about a quarter wavelength of an RF carrier frequency. [0104] According to some embodiments, there is a radio frequency (RF) exciter system that can include a RF exciter circuit for providing RF excitation to a magneto-optical defect center material comprising a plurality of magneto-optical defect centers, the RF exciter circuit comprising: a RF input; a RF ground; and a microstrip line electrically connected to the RF input and short circuited to the ground adjacent a magneto-optical defect center material; a controller configured to control an RF source to apply an RF signal to the RF input; wherein the controller is configured to control the RF source to apply an RF signal to the RF input such that a standing wave RF field is created in the magneto-optical defect center material; and a RF termination component configured to reduce back reflection of a RF signal from the short circuit. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0105] According to some embodiments, the RF termination component can include one of a non-reciprocal isolator device, or a balanced amplifier configuration.

[0106] According to some embodiments, the microstrip line can include a metallic material coated at least over a top surface, a bottom surface, and a side surface of the magneto-optical defect center material, and is short circuited to the RF ground adjacent the magneto-optical defect center material.

[0107] According to some embodiments, the microstrip line can have a wavelength of about a quarter wavelength of an RF carrier frequency.

[0108] According to some embodiments, the polarization of light entering the magneto-optical defect center material can be changed through other ways such as free space phase modulators, fiber coupled phase modulators, and/or other ways known by persons of skill in the art. In some embodiments, the change of polarization may be affected by an applied electric field on the index of refraction of a crystal in the modulator. In some embodiments, the change of polarization is affected by phase modulation such that an electric field is applied along a principal axis of a crystal in the modulator and light polarized along any other principal axis experiences an index of refraction change that is proportional to the applied electric field. In some embodiments, an electro-optic amplitude modulator allows the crystal in the modulator to act as a variable waveplate, allowing linear polarization to change to circular polarization, as well as circular polarization to change to linear polarization, as an applied voltage is increased. In some embodiments, modulators allowing for polarization control may be in a fiber-coupled form in an optical fiber cable or other waveguide.

Bias Magnetic Array

[0109] According to some embodiments, there is a magnetometer that can include a light source configured to provide excitation light; a magneto-optical defect center material with at least one defect center that transmits emitted light when excited by the excitation light; a light sensor configured to receive the emitted light; a plurality of magnets configured to provide a bias magnetic field to the magneto-optical defect center material; a ring magnet holder; and a mount comprising an inside surface, wherein the outside surface of the outer ring slides along the inside surface of the mount. The ring magnet holder can include an outer ring with an outside surface; and a plurality of holders extending from the ring, wherein the plurality of holders are configured to hold the plurality of magnets in a same orientation with respect to one another. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0110] According to some embodiments, the magnetometer can further include a processor configured to: receive an indication of a frequency of the excitation light; receive an indication of a frequency of the emitted light; and determine a magnitude of an external magnetic field based at least in part on a comparison between the frequency of the excitation light and the frequency of the emitted light.

[0111] According to some embodiments, the processor can be further configured to determine a direction of the external magnetic field based at least in part on a comparison between the frequency of the excitation light and the frequency of the emitted light.

[0112] According to some embodiments, the magnet holder can further include a fixation member configured to secure the ring magnet holder in a location within the mount. The fixation member may comprise a set screw.

[0113] According to some embodiments, the mount can include a through-hole configured to allow the excitation light to pass through the through-hole of the mount.

[0114] According to some embodiments, the inside surface of the mount can have a shape that is semi -spherical.

[0115] According to some embodiments, the outside surface of the mount can have a shape that is semi-spherical. [0116] According to some embodiments, the mount can include a first portion and a second portion that are secured together with a plurality of fasteners.

[0117] According to some embodiments, the first portion can include half of the inside surface.

[0118] According to some embodiments, the plurality of magnets can be permanent magnets.

[0119] According to some embodiments, the plurality of holders can each comprise at least one magnet hole, wherein each of the at least one magnet hole can be configured to hold one of the plurality of magnets.

[0120] According to some embodiments, the ring magnet holder can further include at least one mounting tab, and the at least one mounting tab can include a fixation member configured to secure the ring magnet holder in a location within the mount.

[0121] According to some embodiments, the mounting tab can further include at least one through-hole, wherein the at least one through-hole can include a central axis that is coaxial to a central axis of one of the at least one magnet hole.

[0122] According to some embodiments, the bias magnetic field can be substantially uniform through the magneto-optical defect center material.

[0123] According to some embodiments, the magneto-optical material can be capable of fluorescing upon the application of certain light and providing different fluorescence depending upon applied magnetic fields.

[0124] According to some embodiments, a plurality of magnets that can be configured to provide a bias magnetic field to a magneto-optical defect center material. The devices may also include a ring magnet holder that has an outer ring with an outside surface and a plurality of holders extending from the ring. The plurality of holders may be configured to hold a plurality of magnets in a same orientation with respect to one another. The devices may further include a mount that has an inside surface. The outside surface of the outer ring may slide along the inside surface of the mount.

Magneto-Optical Defect Center Sensor with Vivaldi RF Antenna Array

[0125] According to some embodiments, there is a magnetic field sensor assembly that can include an optical excitation source; a radio frequency (RF) generator; a beam former in electrical communication with the RF generator; an array of Vivaldi antenna elements in electrical communication with the beam former; and a magneto-optical defect center material positioned in a far field of the array of Vivaldi antenna elements, wherein the array of Vivaldi antenna elements generate a RF magnetic field that is uniform over the magneto-optical defect center material, wherein the optical excitation source transmits optical light at a first wavelength to the magneto-optical defect center material to detect a magnetic field based on a measurement of optical light at a second wavelength that is different from the first wavelength. According to some embodiments, the magneto-optical defect center material can include a nitrogen vacancy (NV) diamond material having one or more NV centers.

[0126] According to some embodiments, the array of Vivaldi antenna elements can be configured to operate in a range from 2 gigahertz (GHz) to 50 GHz.

[0127] According to some embodiments, the array of Vivaldi antenna elements can include a plurality of Vivaldi antenna elements and an array lattice.

[0128] According to some embodiments, the beam former can be configured to operate the array of Vivaldi antenna elements at 2 GHz.

[0129] According to some embodiments, the beam former can be configured to operate the array of Vivaldi antenna elements at 2.8-2.9 GHz.

[0130] According to some embodiments, the beam former can be configured to spatially oversample the array of Vivaldi antenna elements.

[0131] According to some embodiments, the array of Vivaldi antenna elements can be adjacent the magneto-optical defect center material.

[0132] According to some embodiments, the magneto-optical defect center material can be a diamond having nitrogen vacancies.

Magneto-Optical Defect Center Material with Integrated Waveguide

[0133] Some embodiments relate to a magneto-optical defect center material that may include a first portion comprising a plurality of defect centers dispersed throughout the first portion. The magneto-optical material also may include a second portion adjacent to the first portion. The second portion may not contain significant defect centers. The second portion may be configured to facilitate transmission of light generated by the defect centers of the first portion away from the first portion.

[0134] Some illustrative magneto-optical defect center materials may include a first portion that can have a plurality of defect centers dispersed throughout the first portion. The materials may also include a second portion adjacent to the first portion. The second portion may not contain defect centers. The second portion may be configured to facilitate transmission of light generated by the defect centers of the first portion away from the first portion.

[0135] Some illustrative magnetometers may include a diamond. The diamond may include a first portion and a second portion. The first portion may include a plurality of nitrogen vacancy (NV) centers, and the second portion may not have substantial NV centers. The second portion may be configured to facilitate transmission of light generated from the NV centers of the first portion away from the first portion. The magnetometer may further include a light source that may be configured to transmit light into the first portion of the diamond. The magnetometer may further include a photo detector configured to detect light transmitted through at least one side of the second portion of the diamond. The magnetometer may also include a processor operatively coupled to the photo detector. The processor may be configured to determine a strength of a magnetic field based at least in part on the light detected by the photo detector.

[0136] Some illustrative magneto-optical defect center materials include means for absorbing first light with a first frequency and transmitting second light with a second frequency. The materials may also include means for directing the second light that may be adjacent to the means for absorbing the first light and transmitting the second light. The means for directing the second light may not absorb the first light. The means for directing the second light may be configured to facilitate transmission of the second light away from the means for absorbing the first light and transmitting the second light.

[0137] Some illustrative methods include receiving, at a plurality of defect centers of a first portion of a magneto-optical defect center material, first light with a first frequency. The plurality of defect centers may be dispersed throughout the first portion. The method can also include transmitting, from the plurality of defect centers, second light with a second frequency. The method may further include facilitating, via a second portion of the magneto-optical defect center material, the second light away from the first portion. The second portion may be adjacent to the first portion. The second portion may not contain defect centers.

Drift Error Compensation

[0138] According to some embodiments, a system for magnetic detection may include a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers, a radio frequency (RF) excitation source configured to provide RF excitation to the NV diamond material, an optical excitation source configured to provide optical excitation to the NV diamond material, an optical detector configured to receive an optical signal emitted by the NV diamond material, a magnetic field generator configured to generate a magnetic field applied to the NV diamond material, and a controller. The controller may be configured to control the optical excitation source to apply optical excitation to the NV diamond material, control the RF excitation source to apply a first RF excitation to the NV diamond material, the first RF excitation having a first frequency, and control the RF excitation source to apply a second RF excitation to the NV diamond material, the second RF excitation having a second frequency. The first frequency may be a frequency associated with a first slope point of a fluorescence intensity response of an NV center orientation of a first spin state due to the optical excitation, the first slope point being a positive slope point, and the second frequency may be a frequency associated with a second slope point of the fluorescence intensity response of the NV center orientation of the first spin state due to the optical excitation, the second slope point being a negative slope point.

[0139] In some aspects, the controller may be configured to control the RF excitation source to alternately apply the first RF excitation as a single RF pulse and apply the second RF excitation as a single RF pulse.

[0140] In some aspects, the controller may be configured to control the RF excitation source to alternately apply the first RF excitation as two or more RF pulses in sequence and apply the second RF excitation as two or more RF pulses in sequence.

[0141] In some aspects, the controller may be configured to measure a first fluorescence intensity based on an average of a fluorescence intensity associated with each of the two or more RF pulses of the first RF excitation and measure a second fluorescence intensity based on an average of a fluorescence intensity associated with each of the two or more RF pulses of the second RF excitation.

[0142] In some aspects, the controller may be configured to control the RF excitation source to alternately apply the first RF excitation as three or more RF pulses in sequence and apply the second RF excitation as three or more RF pulses in sequence, measure a first fluorescence intensity based on an average of a fluorescence intensity associated with each of two or more RF pulses of the three or more RF pulses of the first RF excitation, measure a second fluorescence intensity based on an average of a fluorescence intensity associated with each of two or more RF pulses of the three or more RF pulses of the second RF excitation. [0143] In some aspects, the two or more RF pulses of the first RF excitation may be applied last in the sequence of the three or more pulses, and wherein the two or more RF pulses of the second RF excitation are applied last in the sequence of the three or more pulses.

[0144] In some aspects, the positive slope point may be a maximum positive slope point of the fluorescence intensity response of the NV center orientation of the first spin state and the negative slope point may be a maximum negative slope point of the fluorescence intensity response of the NV center orientation of the first spin state.

[0145] In some aspects, the positive slope point and the negative slope point may be set as an average of a maximum positive slope point and a maximum negative slope point of the fluorescence intensity response of the NV center orientation of the first spin state due to the optical excitation.

[0146] In some aspects, the controller may be configured to measure a first fluorescence intensity at the positive slope point, measure a second fluorescence intensity at the negative slope point, and calculate a compensated fluorescence intensity based on a difference between the measured first fluorescence intensity and the measured second fluorescence intensity divided by a difference between the slope of the positive slope point and the slope of the negative slope point.

[0147] In some aspects, the controller may be configured to control the RF excitation source to apply a third RF excitation to the NV diamond material, the third RF excitation having a third frequency. The third frequency may be a frequency associated with a third slope point of the fluorescence intensity response of the NV center orientation of a second spin state due to the optical excitation.

[0148] In some aspects, the third slope point may be a positive slope point.

[0149] In some aspects, the third slope point may be a negative slope point.

[0150] According to some embodiments, a system for magnetic detection may include a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers, a radio frequency (RF) excitation source configured to provide RF excitation to the NV diamond material, an optical excitation source configured to provide optical excitation to the NV diamond material, an optical detector configured to receive an optical signal emitted by the NV diamond material, a magnetic field generator configured to generate a magnetic field applied to the NV diamond material, and a controller. The controller may be configured to control the optical excitation source to apply optical excitation to the NV diamond material, control the RF excitation source to apply a first RF excitation to the NV diamond material, the first RF excitation having a first frequency, and control the RF excitation source to apply a second RF excitation to the NV diamond material, the second RF excitation having a second frequency. The first frequency may be a frequency associated with a first slope point of a fluorescence intensity response of an NV center orientation of a first spin state due to the optical excitation, and the second frequency may be a frequency associated with a second slope point of the fluorescence intensity response of the NV center orientation of a second spin state due to the optical excitation.

[0151] In some aspects, the first slope point may be a positive slope point.

[0152] In some aspects, the second slope point may be a negative slope point.

[0153] In some aspects, the first slope point may be a negative slope point.

[0154] In some aspects, the second slope point may be a negative slope point.

[0155] In some aspects, the controller may be configured to control the RF excitation source to alternately apply the first RF excitation as two or more RF pulses in sequence and apply the second RF excitation as two or more RF pulses in sequence.

[0156] In some aspects, the controller may be configured to measure a first fluorescence intensity based on an average of a fluorescence intensity associated with each of the two or more RF pulses of the first RF excitation and measure a second fluorescence intensity based on an average of a fluorescence intensity associated with each of the two or more RF pulses of the second RF excitation.

[0157] In some aspects, the controller may be configured to control the RF excitation source to alternately apply the first RF excitation as three or more RF pulses in sequence and apply the second RF excitation as three or more RF pulses in sequence, measure a first fluorescence intensity based on an average of a fluorescence intensity associated with each of two or more RF pulses of the three or more RF pulses of the first RF excitation, and measure a second fluorescence intensity based on an average of a fluorescence intensity associated with each of two or more RF pulses of the three or more RF pulses of the second RF excitation.

[0158] In some aspects, the two or more RF pulses of the first RF excitation may be applied last in the sequence of the three or more pulses, and wherein the two or more RF pulses of the second RF excitation are applied last in the sequence of the three or more pulses. [0159] In some aspects, the controller may be configured to control the RF excitation source to apply a third RF excitation to the NV diamond material, the third RF excitation having a third frequency, and control the RF excitation source to apply a fourth RF excitation to the NV diamond material, the fourth RF excitation having a fourth frequency. The third frequency may be a frequency associated with a third slope point of the fluorescence intensity response of the NV center orientation of the first spin state due to the optical excitation, and the fourth frequency may be a frequency associated with a fourth slope point of the fluorescence intensity response of the NV center orientation of the second spin state due to the optical excitation.

[0160] According to some embodiments, a method for compensating for drift error in a magnetic detection system may include applying optical excitation to a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers, applying a first RF excitation to the NV diamond material, the first RF excitation having a first frequency, applying a second RF excitation to the NV diamond material, the second RF excitation having a second frequency, applying a third RF excitation to the NV diamond material, the third RF excitation having a third frequency, and applying a fourth RF excitation to the NV diamond material, the third RF excitation having a fourth frequency. The first frequency may be a frequency associated with a first slope point of a fluorescence intensity response of an NV center orientation of a first spin state due to the optical excitation, the first slope point being a positive slope point. The second frequency may be a frequency associated with a second slope point of the fluorescence intensity response of the NV center orientation of the first spin state due to the optical excitation, the second slope point being a negative slope point. The third frequency may be a frequency associated with a third slope point of the fluorescence intensity response of the NV center orientation of a second spin state due to the optical excitation. The fourth frequency may be a frequency associated with a fourth slope point of the fluorescence intensity response of the NV center orientation of the second spin state due to the optical excitation.

[0161] In some aspects, the method may further include applying each of the steps to each of four NV center orientations of the NV diamond material.

[0162] According to some embodiments, a system for magnetic detection may include a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers, a radio frequency (RF) excitation source configured to provide RF excitation to the NV diamond material, an optical excitation source configured to provide optical excitation to the NV diamond material, an optical detector configured to receive an optical signal emitted by the NV diamond material, a magnetic field generator configured to generate a magnetic field applied to the NV diamond material, a means for controlling the optical excitation source to apply optical excitation to the NV diamond material, controlling the RF excitation source to apply a first RF excitation to the NV diamond material, the first RF excitation having a first frequency, and controlling the RF excitation source to apply a second RF excitation to the NV diamond material, the second RF excitation having a second frequency. The first frequency may be a frequency associated with a first slope point of a fluorescence intensity response of an NV center orientation of a first spin state due to the optical excitation, the first slope point being a positive slope point, and the second frequency may be a frequency associated with a second slope point of the fluorescence intensity response of the NV center orientation of the first spin state due to the optical excitation, the second slope point being a negative slope point.

Thermal Drift Error Compensation

[0163] According to some embodiments, there is a system for magnetic detection of an external magnetic field, comprising: a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers, the diamond material having a plurality of crystallographic axes each directed in different directions, the NV centers each corresponding to a respective one of the plurality of crystallographic axes; a radio frequency (RF) excitation source configured to provide RF excitations to the NV diamond material to excite electron spin resonances corresponding to the RF excitations, each crystallographic axis corresponding to a different electron spin resonance; an optical excitation source configured to provide optical excitation to the NV diamond material; an optical detector configured to receive an optical signal based on light emitted by the NV diamond material, the optical signal having a plurality of intensity changes corresponding respectively to electron spin resonances of the NV centers; and a controller configured to: receive a light detection signal from the optical detector based on the optical signal; determine the spectral position corresponding to some of the electron spin resonances based on the light detection signal; determine a measured four-dimensional projection of a magnetic field based on the determined spectral positions of a subset of all of the plurality of spin resonances, where the number of spin resonances in the subset is one half of a total number of the spin resonances; and determine an estimated three-dimensional magnetic field based on the measured four-dimensional magnetic field projections. [0164] According to some embodiments, there are two different electron spin resonances for each of the crystallographic axes.

[0165] According to some embodiments, the total number of spin resonances is eight and the number of spin resonances in the subset of spin resonances is four.

[0166] According to some embodiments, the subset of spin resonances includes spin resonances corresponding to each of the crystallographic axes.

[0167] According to some embodiments, the controller is configured to determine the measured four-dimensional projected field based on a least squares fit.

[0168] According to some embodiments, spin resonances in the subset of spin resonances are selected to reduce thermal drift.

[0169] According to some embodiments, there is a system for magnetic detection of an external magnetic field, comprising: a magneto-optical defect center material comprising a plurality of magneto-optical defect centers, the magneto-optical defect center material having a plurality of crystallographic axes each directed in different directions, the magneto-optical defect centers each corresponding to a respective one of the plurality of crystallographic axes; a radio frequency (RF) excitation source configured to provide RF excitations to the magneto-optical defect center material to excite electron spin resonances corresponding to the RF excitations, each crystallographic axis corresponding to a different spin resonance; an optical excitation source configured to provide optical excitation to the magneto-optical defect center material; an optical detector configured to receive an optical signal based on light emitted by the magneto- optical defect center material, the optical signal having a plurality of intensity changes corresponding respectively to electron spin resonances of the magneto-optical defect centers; and a controller configured to: receive a light detection signal from the optical detector based on the optical signal; determine the spectral position corresponding to some of the electron spin resonances based on the light detection signal; determine a measured four-dimensional projection of a magnetic field based on the determined spectral positions of a subset of all of the plurality of spin resonances, where the number of spin resonances in the subset is one half of a total number of the spin resonances; and determine an estimated three-dimensional magnetic field based on the measured four-dimensional magnetic field projections.

[0170] According to some embodiments, the magneto-optical defect center material may comprise one of diamond, silicon carbide, or silicon. [0171] According to some embodiments, there is a system for magnetic detection of an external magnetic field, comprising: a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers, the diamond material having a plurality of crystallographic axes each directed in different directions, the NV centers each corresponding to a respective one of the plurality of crystallographic axes; a radio frequency (RF) excitation source configured to provide RF excitations to the NV diamond material to excite electron spin resonances corresponding to the RF excitations, each crystallographic axis corresponding to a different spin resonance; an optical excitation source configured to provide optical excitation to the NV diamond material; an optical detector configured to receive an optical signal based on light emitted by the NV diamond material, the optical signal having a plurality of intensity changes corresponding respectively to electron spin resonances of the NV centers; and a controller configured to:

receive a light detection signal from the optical detector based on the optical signal; determine the spectral position corresponding to some of the electron spin resonances based on the light detection signal; determine a measured four-dimensional projection of a magnetic field based on some of the spectral positions of the plurality of spin resonances; determine an estimated three- dimensional magnetic field based on the measured four-dimensional magnetic field projection; and determine a shift in the estimated three-dimensional magnetic field due to thermal drift based on the estimated three-dimensional magnetic field and the measured four-dimensional magnetic field projection.

[0172] According to some embodiments, there is a method for determining an external magnetic field, comprising: applying RF excitations to nitrogen vacancy (NV) diamond material to excite electron spin resonances corresponding to the RF excitations, the NV diamond material comprising a plurality of NV centers, the NV diamond material having a plurality of

crystallographic axes each directed in different directions, the NV centers each corresponding to a respective one of the plurality of crystallographic axes, each crystallographic axis

corresponding to a different spin resonance; applying optical excitation to the NV diamond material; detecting an optical signal based on light emitted by the NV diamond material, the optical signal having a plurality of intensity changes corresponding respectively to electron spin resonances of the NV centers; receiving a light detection signal based on the detected optical signal; determining the spectral position corresponding to some of the electron spin resonances based on the light detection signal; determining a measured four-dimensional projection of a magnetic field based on the determined spectral positions of a subset of all of the plurality of spin resonances, where the number of spin resonances in the subset is one half of a total number of the spin resonances; and determining an estimated three-dimensional magnetic field based on the measured four-dimensional magnetic field projections.

[0173] According to some embodiments, there is a method for determining an external magnetic field, comprising: applying RF excitations to magneto-optical defect center material to excite electron spin resonances corresponding to the RF excitations, the magneto-optical defect center material comprising a plurality of magneto-optical defect centers, the magneto-optical defect center material having a plurality of crystallographic axes each directed in different directions, the magneto-optical defect centers each corresponding to a respective one of the plurality of crystallographic axes, each crystallographic axis corresponding to a different spin resonance; applying optical excitation to the magneto-optical defect center material; detecting an optical signal based on light emitted by the magneto-optical defect center material, the optical signal having a plurality of intensity changes corresponding respectively to electron spin resonances of the magneto-optical defect centers; receiving a light detection signal based on the detected optical signal; determining the spectral position corresponding to some of the electron spin resonances based on the light detection signal; determining a measured four-dimensional projection of a magnetic field based on the determined spectral positions of a subset of all of the plurality of spin resonances, where the number of spin resonances in the subset is one half of a total number of the spin resonances; and determining an estimated three-dimensional magnetic field based on the measured four-dimensional magnetic field projections.

[0174] According to some embodiments, there is a method for determining an external magnetic field, comprising: applying RF excitations to nitrogen vacancy (NV) diamond material to excite electron spin resonances corresponding to the RF excitations, the NV diamond material comprising a plurality of NV centers, the NV diamond material having a plurality of

crystallographic axes each directed in different directions, the NV centers each corresponding to a respective one of the plurality of crystallographic axes, each crystallographic axis

corresponding to a different spin resonance; applying optical excitation to the NV diamond material; detecting an optical signal based on light emitted by the NV diamond material, the optical signal having a plurality of intensity changes corresponding respectively to electron spin resonances of the NV centers; receiving a light detection signal based on the detected optical signal; determining the spectral position corresponding to some of the electron spin resonances based on the light detection signal; determining a measured four-dimensional projection of a magnetic field based on some of the spectral positions of the plurality of spin resonances;

determining an estimated three-dimensional magnetic field based on the measured four- dimensional magnetic field projections; and determining a shift in the estimated three- dimensional magnetic field due to thermal drift based on the estimated three-dimensional magnetic field and the measured four-dimensional magnetic field projections.

[0175] According to some embodiments, there is a method for determining an external magnetic field, comprising: applying RF excitations to magneto-optical defect center material to excite electron spin resonances corresponding to the RF excitations, the magneto-optical defect center material comprising a plurality of magneto-optical defect centers, the magneto-optical defect center material having a plurality of crystallographic axes each directed in different directions, the magneto-optical defect centers each corresponding to a respective one of the plurality of crystallographic axes, each crystallographic axis corresponding to a different spin resonance; applying optical excitation to the magneto-optical defect center material; detecting an optical signal based on light emitted by the magneto-optical defect center material, the optical signal having a plurality of intensity changes corresponding respectively to electron spin resonances of the magneto-optical defect centers; receiving a light detection signal based on the detected optical signal; determining the spectral position corresponding to some of the electron spin resonances based on the light detection signal; determining a measured four-dimensional projection of a magnetic field based on some of the spectral positions of the plurality of spin resonances; determining an estimated three-dimensional magnetic field based on the measured four-dimensional magnetic field projections; and determining a shift in the estimated three- dimensional magnetic field due to thermal drift based on the estimated three-dimensional magnetic field and the measured four-dimensional magnetic field projections.

Pulsed RF Methods for Optimization of Continuous Wave Measurements

[0176] According to some embodiments, a method for magnetic detection comprises (a) providing optical excitation to a magneto-optical defect center material using an optical light source, (b) providing pulsed radio frequency (RF) excitation to the magneto-optical defect center material using a pulsed RF excitation source, and (c) receiving an optical signal emitted by the magneto-optical defect center material using an optical detector, wherein the magneto-optical defect center material comprises a plurality of magneto-optical defect centers, and wherein (a) and (c) occur during (b).

[0177] According to some embodiments, the step of providing pulsed RF excitation comprises at least one pulse sequence, the at least one pulse sequence including at least one period of idle time followed by at least one period of RF pulse. According to some embodiments, the at least one period of idle time comprises at least one period of reference collection time. According to some embodiments, the at least one period of reference collection time occurs during (a) and (c), but not during (b). According to some embodiments, the at least one period of RF pulse comprises at least one period of settling time and at least one period of collection time.

According to some embodiments, the at least one pulse sequence is for a time ranging between

[0178] According to some embodiments, the at least one period of idle time is shorter than the at least one period of RF pulse. According to some embodiments, the pulsed RF excitation occurs at a single frequency. According to some embodiments, a different single frequency is selected for each diamond lattice vector and associated ms = ±1 spin state.

[0179] According to some embodiments, the at least one period of idle time is longer than the at least one period of RF pulse. According to some embodiments, the pulsed RF excitation frequency is swept.

[0180] According to some embodiments, the method further comprises, following the step of receiving an optical signal, suppressing the optical detector and the pulsed RF source. According to some embodiments, the method further comprises repolarizing the optical light source to set the magneto-optical defect center material for subsequent measurement. According to some embodiments, the optical light source is continuously applied throughout the method for magnetic detection.

[0181] According to some embodiments, a system for magnetic detection comprises a controller configured to (a) provide optical excitation to a magneto-optical defect center material using an optical light source, (b) provide pulsed radio frequency (RF) excitation to the magneto- optical defect center material using a pulsed RF excitation source, and (c) receive an optical signal emitted by the magneto-optical defect center material using an optical detector, wherein the magneto-optical defect center material comprises a plurality of magneto-optical defect centers, and wherein (a) and (c) occur during (b). High Speed Sequential Cancellation for Pulsed Mode

[0182] Some embodiments provide methods and systems for high bandwidth acquisition of magnetometer data with increased sensitivity. In some implementations, a reference signal may be utilized prior to acquisition of a measured signal for a magnetometer. This reference signal may provide a full repolarization of a magneto-optical defect center material prior to acquiring the reference signal. The reference signal may then be used to adjust the measured signal to correct for potential fluctuations in optical excitation power levels, which can cause a

proportional fluctuation in the measured signal. However, such a full repolarization and added reference signal before each measured signal may reduce the bandwidth of the magnetometer and may also increase measurement noise, and therefore decrease sensitivity, by including noise from the reference signal when calculating the resulting processed signal. To increase bandwidth and sensitivity, the reference signal may be omitted such that only a radiofrequency (RF) pulse excitation sequence is included between measurements. In some implementations, a fixed "system rail" photo measurement may be obtained initially and used as a fixed reference signal for subsequent measured signals. The fixed, nominal reference signal can substantially compensate for intensity shifts for the magnetometer without decreasing bandwidth or sensitivity. In other implementations, additional signal processing may be utilized to adjust for drift, jitter, or other variations in intensity levels.

[0183] Some embodiments may include a magnetometer and a controller. The magnetometer may include a magneto-optical defect center material, an optical excitation source, a

radiofrequency (RF) excitation source, and an optical sensor. The controller may be configured to activate a radiofrequency (RF) pulse sequence for the RF excitation source to apply a RF field to the magneto-optical defect center material, acquire a nominal ground reference signal for the magneto-optical defect center material, and acquire a magnetic field measurement from the magneto-optical defect center material using the optical sensor. The magnetic field measurement may be acquired independent of a reference magnetic field measurement.

[0184] In some implementations, acquiring the repetitive magnetic field measurement can include a polarization pulse length. In some implementations, the controller may processes the repetitive magnetic field measurement directly to obtain magnetometry measurements. In some implementations, the controller may further be configured to determine a vector of the repetitive magnetic field measurement. In some implementations, the controller may use a fixed system rail photo measurement as a nominal reference value. The magneto-optical defect center material may be a diamond having nitrogen vacancies. The controller may be further configured to process the magnetic field measurement.

[0185] Other implementations may relate to a method for operating a magnetometer having a magneto-optical defect center material. The method may include activating a radiofrequency (RF) pulse sequence to apply an RF field to the magneto-optical defect center material, acquiring a nominal ground reference signal for the magneto-optical defect center material, and acquiring a magnetic field measurement using the magneto-optical defect center material. The magnetic field measurement may be acquired independent of a reference magnetic field measurement.

[0186] In some implementations, acquiring the magnetic field measurement can include a polarization pulse length. In some implementations, acquiring a magnetic field measurement may include processing the magnetic field measurement directly to obtain magnetometry measurements. In some implementations, the method may further include determining a vector of the repetitive magnetic field measurement. In some implementations, acquiring a magnetic field measurement may include using a fixed system rail photo measurement as a nominal reference value. The magneto-optical defect center material may be a diamond having nitrogen vacancies. The method can further include processing the magnetic field measurement using a controller.

[0187] Yet other implementations relate to a sensor that may include a magneto-optical defect center material, a radiofrequency (RF) excitation source, and a controller. The controller may be configured to activate a radiofrequency (RF) pulse sequence for the RF excitation source to apply a RF field to the magneto-optical defect center material, acquire a nominal ground reference signal for the magneto-optical defect center material, and acquire a magnetic field measurement from the magneto-optical defect center material. The magnetic field measurement may be acquired independent of a reference magnetic field measurement.

[0188] In some implementations, acquiring the magnetic field measurement can include a polarization pulse length. In some implementations, the controller may processes the magnetic field measurement directly to obtain magnetometry measurements. In some implementations, the controller may further be configured to determine a vector of the magnetic field measurement. In some implementations, the controller may use a fixed system rail photo measurement as a nominal reference value. The magneto-optical defect center material may be a diamond having nitrogen vacancies. The controller may be further configured to process the magnetic field measurement.

Photodetector Circuit Saturation Mitigation

[0189] Some embodiments relate to a system that may comprise: a magneto-optical defect center material, a first optical excitation source configured to provide a first optical excitation to the magneto-optical defect center material, a second optical excitation source configured to provide a second optical excitation to the magneto-optical defect center material, and an optical detection circuit comprising a photocomponent, the optical detection circuit configured to activate a switch between a disengaged state and an engaged state, receive, via the second optical excitation source, a light signal comprising a high intensity signal provided by the second optical excitation source, and cause at least one of the photocomponent or the optical detection circuit to operate in a non-saturated state responsive to the activation of the switch.

[0190] Some embodiments relate to an apparatus that may comprise at least one processor and at least one memory storing computer program code, the at least one memory and the computer program code configured to, with the processor, cause the apparatus to at least: activate a switch between a disengaged state and an engaged state, receive, via a second optical excitation source, a light signal comprising a high intensity signal provided by the second optical excitation source, wherein the second optical excitation source is configured to provide optical excitation to a magneto-optical defect center material, and cause at least one of a photocomponent or an optical detection circuit to operate in a non-saturated state responsive to the activation of the switch.

[0191] Some embodiments relate to a controller. The controller may be configured to: activate a switch between a disengaged state and an engaged state, and activate an optical excitation source configured to provide optical excitation to a magneto-optical defect center material responsive to the activation of the switch, wherein the switch is configured to cause at least one of a photocomponent or an optical detection circuit to operate in a non-saturated state.

[0192] Some embodiments relate to a method that may comprise: activating a switch between a disengaged state and an engaged state, receiving, via a second optical excitation source, a light signal comprising a high intensity signal provided by the second optical excitation source, wherein the second optical excitation source is configured to provide optical excitation to a magneto-optical defect center material, and causing at least one of a photocomponent or an optical detection circuit to operate in a non-saturated state responsive to the activation of the switch.

Shifted Magnetometry Adapted Cancellation for Pulse Sequence

[0193] According to some embodiments, a system for magnetic detection may include a magneto-optical defect center material comprising a plurality of defect centers, a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center material, an optical excitation source configured to provide optical excitation to the magneto- optical defect center material, an optical detector configured to receive an optical signal emitted by the magneto-optical defect center material, a bias magnet configured to separate RF resonance responses of the lattice oriented subsets of the magneto-optical defect center material, and a controller. The controller may be configured to control the optical excitation source and the RF excitation source to apply a first pulse sequence to the magneto-optical defect center material, the first pulse sequence comprising a first optical excitation pulse, a first pair of RF excitation pulses separated by a first time period, and a second optical excitation pulse to the magneto- optical defect center material. The controller may be configured to control the optical excitation source and the RF excitation source to further apply a second pulse sequence to the magneto- optical defect center material, the second pulse sequence comprising a third optical excitation pulse, a second pair of RF excitation pulses separated by a second time period, and a fourth optical excitation pulse to the magneto-optical defect center material. In some embodiments, a pulse width of the first pair of RF excitation pulses may be different than a pulse width of the second pair of RF excitation pulses, and the first time period may be different than the second time period. The controller may be further configured to receive a first light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the first pulse sequence and may be configured to receive a second light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the second pulse sequence. The controller may be further configured to compute a combined measurement based on a difference between a measured value of the first light detection signal and a measured value of the second light detection signal wherein the slope of the combined measurement is greater that the slope of the first light detection signal and the second light detection signal. The controller may be further configured to compute a combined measurement based on a difference between a measured value of the first light detection signal and a measured value of the second light detection signal wherein the slope of the combined measurement is greater than the slope of the measured value of the first and second light detection signals.

[0194] According to some embodiments, a method for magnetic detection using a magneto- optical defect center material comprising a plurality of defect centers may comprise applying a first pulse sequence to the magneto-optical defect center material, applying a second pulse sequence to the magneto-optical defect center material, receiving a first light detection signal using an optical detector, receiving a second light detection signal using the optical detector, and computing a combined measurement based on a difference between a measured value of the first light detection signal and a measured value of the second light detection signal. The first pulse sequence may comprise a first optical excitation pulse using an optical excitation source, a first pair of RF excitation pulses separated by a first time period using a radio frequency (RF) excitation source, and a second optical excitation pulse to the magneto-optical defect center material using the optical excitation source. The second pulse sequence may comprise a third optical excitation pulse using the optical excitation source, a second pair of RF excitation pulses separated by a second time period using the RF excitation source, and a fourth optical excitation pulse to the magneto-optical defect center material using the optical excitation source. In some embodiments, a pulse width of the first pair of RF excitation pulses is different than a pulse width of the second pair of RF excitation pulses. In some embodiments, the first time period is different than the second time period. Receiving the first light detection signal may be based on an optical signal emitted by the magneto-optical defect center material due to the first pulse sequence. The second light detection signal, may be based on an optical signal emitted by the magneto-optical defect center material due to the second pulse sequence.

[0195] In some embodiments, an RF excitation frequency used for the first pair of RF excitation pulses and the second pair of RF excitation pulses in a system for magnetic detection may be associated with an axis of a defect center of the magneto-optical defect center material. In some embodiments, the controller may be further configured to compute a change in an external magnetic field acting on the magneto-optical defect center material based on the combined measurement. In some embodiments, a method for magnetic detection using a magneto-optical defect center material has the RF excitation frequency used for the first pair of RF excitation pulses and the second pair of RF excitation pulses is associated with an axis of a defect center of the magneto-optical defect center material. In some embodiments, a method for magnetic detection using a magneto-optical defect center material further comprises computing a change in an external magnetic field acting on the magneto-optical defect center material based on the combined measurement. In some embodiments, the second pair of RF excitation pulses of the first pulse sequence may be applied at a frequency detuned from a resonance frequency of the magneto-optical defect center material. The pulse width of the second pair of RF excitation pulses may be associated with a null at center frequency representing a lack of dimming in the fluorescence of the magneto-optical defect center material. The second time period may be associated with a null at a center frequency representing a lack of dimming in the fluorescence of the magneto-optical defect center material. The pulse width of the second pair of RF excitation pulses and the second time period may be associated with a null at a center frequency

representing a lack of dimming in the fluorescence of the magneto-optical defect center material. The RF excitation source may be a microwave antenna. In some embodiments, of a system for magnetic detection, the controller may be configured to apply the first pair of RF excitation pulses followed by the second pair of RF excitation pulses. In some embodiments, the pulse width of the first pair of RF excitation pulses and the first time period is associated with a high point at a center frequency representing dimming in the fluorescence of the magneto-optical defect center material. In some embodiments, a method for magnetic detection using a magneto- optical defect center material may have the first pair of RF excitation pulses applied followed by the second pair of RF excitation pulses. In some embodiments, the bias magnet is one of a permanent magnet, a magnet field generator, or a Halbach set of permanent magnets.

[0196] In some embodiments, computing the change in an external magnetic field acting on the magneto-optical defect center material based on the combined measurement comprise a plurality of pairs of RF excitation pulses. In some embodiments, once the magnetometry curves have been obtained for the pairs of RF excitation pulses at different frequencies, a SMAC measurement may be performed at a chosen frequency (e.g. at a frequency with a maximum slope for the curve) and the intensity of the SMAC measurement is monitored to provide an estimate of the magnetic field. In some embodiments, the maximum slope, positive and negative, may be determined from the curve obtained by the SMAC pairing and the corresponding frequencies. In some embodiments, the curve may be first smoothed and fit to a cubic spline. In some embodiments, only the corresponding frequencies may be stored for use in magnetic field measurements. In some implementations, the entire curve may be stored.

[0197] According to some embodiments, a magnetic detection system may comprise a defect center material responsive to an applied magnetic field, a radio frequency (RF) emitter operational to provide a first RF pulse sequence separated by at least one pause, a detector operational to measure the fluorescence of the defect center material in conjunction with the first RF pulse sequence and the second RF pulse sequence, thereby providing a first measurement curve and a second measurement curve affected by the applied magnetic field, respectfully, and a control circuit connected to the detector and operational to determine a difference between the first measurement curve and the second measurement curve to obtain greater sensitivity to variations in the applied magnetic field. The RF emitter may be operational to provide a second RF pulse sequence that is different from the first RF pulse sequence. The RF emitter may be operational to provide a second RF pulse sequence that is different from the first RF pulse sequence.

[0198] In some embodiments, the first RF pulse sequence and the second RF pulse sequence are applied at a frequencies detuned from a resonance frequency of the defect center material. In some embodiments, the first RF pulse sequence is applied followed by the second RF pulse sequence. The defect center material may be a nitrogen vacancy diamond. The defect center material may be Silicon Carbide (SiC).

[0199] According to some embodiments, a method for magnetic detection or a method for detecting a magnetic field, comprises emitting a first RF pulse sequence separated by at least one pause, using an RF emitter to a defect center material, emitting a second RF pulse sequence that is different from the first RF pulse sequence, using the RF emitter, to the defect center material, measure the fluorescence of the defect center material in conjunction with the first RF pulse sequence and the second RF pulse sequence, using a detector, providing a first measurement curve and a second measurement curve of the measured fluorescence of the defect center material affected by the applied magnetic field, respectfully for the first RF pulse sequence and the second RF pulse sequence, and determining a difference between the first measurement curve and the second measurement curve to obtain greater sensitivity to variations in the applied magnetic field. [0200] In some embodiments of a method for magnetic detection, determining the difference between the first measurement curve and the second measurement curve may be performed by a control circuit. In some embodiments, the first RF pulse sequence and the second RF pulse sequence may be applied at a frequency detuned from a resonance frequency of the defect center material. In some embodiments, the first RF pulse sequence may be emitted followed by the second RF pulse sequence. In some embodiments, the defect center material may be a nitrogen vacancy diamond. In some embodiments, the defect center material is Silicon Carbide (SiC).

[0201] According to some embodiments, a system for magnetic detection may comprise, a magneto-optical defect center material comprising a plurality of defect centers, a means of providing RF excitation to the magneto-optical defect center material, a means of providing optical excitation to the magneto-optical defect center material, a means of receiving an optical signal emitted by the magneto-optical defect center material, and a means of controlling the provided RF excitation and provided optical excitation. The means of controlling the provided RF excitation and provided optical excitation may apply a first pulse sequence to the magneto- optical defect center material, the first pulse sequence comprising a first optical excitation pulse, a first pair of RF excitation pulses separated by a first time period, and a second optical excitation pulse to the magneto-optical defect center material, control the optical excitation source and the RF excitation source to apply a second pulse sequence to the magneto-optical defect center material, the second pulse sequence comprising a third optical excitation pulse, a second pair of RF excitation pulses separated by a second time period, and a fourth optical excitation pulse to the magneto-optical defect center material, receive a first light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the first pulse sequence, receive a second light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the second pulse sequence, and compute a combined measurement based on a difference between a measured value of the first light detection signal and a measured value of the second light detection signal. The pulse width of the first pair of RF excitation pulses may be different than the pulse width of the second pair of RF excitation pulses, and the first time period may be different than the second time period.

Magnetic Field Proxy Through RF Frequency Dithering [0202] Some embodiments may include a system having a magnetometer and a controller. The magnetometer may include a magneto-optical defect center material, an optical excitation source, a radiofrequency (RF) excitation source, and an optical sensor. The controller may be configured to activate a radiofrequency (RF) pulse sequence for the RF excitation source to apply a RF field to the magneto-optical defect center material. The RF pulse sequence may be based on a magnetic field proxy modulation and a base RF wave, and the magnetic field proxy modulation may be indicative of a proxy magnetic field. The controller may be further configured to activate an optical pulse sequence for the optical excitation source to apply a laser pulse to the magneto- optical defect center material and acquire in conjunction with the optical pulse sequence a magnetic field measurement from the magneto-optical defect center material using the optical sensor. The magnetic field measurement comprises a proxy magnetic field based on the magnetic field proxy modulation.

[0203] In some implementations, the magnetic field proxy modulation may be a sinusoidal magnetic field proxy modulation. In some implementations, the sinusoidal magnetic field proxy modulation may be calculated based on ybi sin(27i it), where γ is the electron gyromagnetic ratio for the magneto-optical defect center material, bi is a selected projected magnitude for the proxy magnetic field, and f\ is selected frequency for the proxy magnetic field. In some

implementations, the selected projected magnitude for the proxy magnetic field may be between 100 picoTeslas and 1 microTesla. In some implementations, the selected frequency for the proxy magnetic field may be between 0 Hz and 100 kHz. In some implementations, the magnetic field measurement may include magnetic communication data. In some implementations, the magnetic field measurement may include magnetic navigation data. In some implementations, the magnetic field measurement may include magnetic location data. In some implementations, the magneto-optical defect center material may include a diamond having nitrogen vacancies.

[0204] Other implementations may relate to a method for operating a magnetometer having a magneto-optical defect center material. The method may include activating a radiofrequency (RF) pulse sequence to apply an RF field to the magneto-optical defect center material and acquiring a magnetic field measurement using the magneto-optical defect center material. The RF pulse sequence may be based on a magnetic field proxy modulation and a base RF wave, and the magnetic field proxy modulation is indicative of a proxy magnetic field. The magnetic field measurement may include a proxy magnetic field based on the magnetic field proxy modulation. [0205] In some implementations, the magnetic field proxy modulation may be a sinusoidal magnetic field proxy modulation. In some implementations, the sinusoidal magnetic field proxy modulation may be calculated based on ybi sin(27i it), where γ is the electron gyromagnetic ratio for the magneto-optical defect center material, bi is a selected projected magnitude for the proxy magnetic field, is a selected frequency for the proxy magnetic field. In some

implementations, the selected projected magnitude for the proxy magnetic field may be between 100 picoTeslas and 1 microTesla. In some implementations, the selected frequency for the proxy magnetic field may be between 0 Hz and 100 kHz. In some implementations, the magnetic field measurement may include magnetic communication data. In some implementations, the magnetic field measurement may include magnetic navigation data. In some implementations, the magnetic field measurement may include magnetic location data. In some implementations, the magneto-optical defect center material may include a diamond having nitrogen vacancies.

[0206] Yet other implementations may relate to a sensor that includes a magneto-optical defect center material, a radiofrequency (RF) excitation source, and a controller. The controller is configured to activate a radiofrequency (RF) pulse sequence for the RF excitation source to apply a RF field to the magneto-optical defect center material and acquire a magnetic field measurement from the magneto-optical defect center material. The RF pulse sequence may be based on a magnetic field proxy modulation and a base RF wave, and the magnetic field proxy modulation is indicative of a proxy magnetic field. The magnetic field measurement may include a proxy magnetic field based on the magnetic field proxy modulation.

[0207] In some implementations, the magnetic field proxy modulation may be a sinusoidal magnetic field proxy modulation. In some implementations, the sinusoidal magnetic field proxy modulation may be calculated based on ybi sin(27i it), where γ is the electron gyromagnetic ratio for the magneto-optical defect center material, bi is a selected projected magnitude for the proxy magnetic field, and f\ is selected frequency for the proxy magnetic field. In some

implementations, the selected projected magnitude for the proxy magnetic field may be between 100 picoTeslas and 1 microTesla. In some implementations, the selected frequency for the proxy magnetic field may be between 0 Hz and 100 kHz.

[0208] Some embodiments relate to a magnetometer that includes a magneto-optical defect center material, a radiofrequency (RF) excitation source, an optical sensor, and a controller. The controller may be configured to activate a radiofrequency (RF) pulse sequence for the RF excitation source to apply a RF field to the magneto-optical defect center material and acquire a magnetic field measurement from the magneto-optical defect center material using the optical sensor. The RF pulse sequence may be based on a magnetic field proxy modulation and a base RF wave, and the magnetic field proxy modulation may be indicative of a proxy magnetic field. The magnetic field measurement may include a proxy magnetic field based on the magnetic field proxy modulation. The controller may be further configured to set a value for a flag indicative of passing an initial pass/fail test based on a processed proxy magnetic reference signal determined from the magnetic field measurement.

[0209] In some implementations, the magnetic field proxy modulation may be a sinusoidal magnetic field proxy modulation. In some implementations, the sinusoidal magnetic field proxy modulation may be calculated based on ybi sin(27i it), where γ is the electron gyromagnetic ratio for the magneto-optical defect center material, bi is a selected projected magnitude for the proxy magnetic field, is selected frequency for the proxy magnetic field. In some

implementations, the selected projected magnitude for the proxy magnetic field may be between 100 picoTeslas and 1 microTesla. In some implementations, the selected frequency for the proxy magnetic field may be between 0 Hz and 100 kHz.

[0210] Some embodiments relate to a magnetometer that includes a magneto-optical defect center material, a radiofrequency (RF) excitation source, an optical sensor, and a controller. The controller may be configured to activate a radiofrequency (RF) pulse sequence for the RF excitation source to apply a RF field to the magneto-optical defect center material and acquire a magnetic field measurement from the magneto-optical defect center material using the optical sensor. The RF pulse sequence may be based on a magnetic field proxy modulation and a base RF wave, and the magnetic field proxy modulation may be indicative of a proxy magnetic field. The magnetic field measurement may include a proxy magnetic field based on the magnetic field proxy modulation. The controller may be further configured to determine an attenuation value based on a processed proxy magnetic reference signal determined from the magnetic field measurement.

[0211] In some implementations, the magnetic field proxy modulation may be a sinusoidal magnetic field proxy modulation. In some implementations, the sinusoidal magnetic field proxy modulation may be calculated based on ybi sin(27i it), where γ is an electron gyromagnetic ratio for the magneto-optical defect center material, bi is a selected projected magnitude for the proxy magnetic field, is selected frequency for the proxy magnetic field. In some

implementations, the selected projected magnitude for the proxy magnetic field may be between 100 picoTeslas and 1 microTesla. In some implementations, the selected frequency for the proxy magnetic field may be between 0 Hz and 100 kHz.

[0212] Some embodiments relate to a magnetometer that includes a magneto-optical defect center material, a radiofrequency (RF) excitation source, an optical sensor, and a controller. The controller may be configured to activate a radiofrequency (RF) pulse sequence for the RF excitation source to apply a RF field to the magneto-optical defect center material and acquire a magnetic field measurement from the magneto-optical defect center material using the optical sensor. The RF pulse sequence may be based on a magnetic field proxy modulation and a base RF wave, and the bia magnetic field proxy modulation may be indicative of a proxy magnetic field. The magnetic field measurement may include a proxy magnetic field based on the magnetic field proxy modulation. The controller may be further configured to determine an estimated calibrated noise floor value based on a processed proxy magnetic reference signal determined from the magnetic field measurement.

[0213] In some implementations, the magnetic field proxy modulation may be a sinusoidal magnetic field proxy modulation. In some implementations, the sinusoidal magnetic field proxy modulation may be calculated based on ybi sin(27i it), where γ is an electron gyromagnetic ratio for the magneto-optical defect center material, bi is a selected projected magnitude for the proxy magnetic field, is selected frequency for the proxy magnetic field. In some

implementations, the selected projected magnitude for the proxy magnetic field may be between 100 picoTeslas and 1 microTesla. In some implementations, the selected frequency for the proxy magnetic field may be between 0 Hz and 100 kHz.

[0214] Other implementations relate to a magnetometer that includes a magneto-optical defect center material, an excitation source, an optical sensor, and a controller. The controller may be configured to activate an energy pulse sequence for the excitation source to apply an energy field to the magneto-optical defect center material and acquire a magnetic field measurement from the magneto-optical defect center material using the optical sensor. The energy pulse sequence may be based on a magnetic field proxy modulation and a base signal, and the magnetic field proxy modulation may be indicative of a proxy magnetic field. The magnetic field measurement may include a proxy magnetic field based on the magnetic field proxy modulation. [0215] In some other implementations, a magnetic field proxy modulation may be a sinusoidal magnetic field proxy modulation. In some implementations, the sinusoidal magnetic field proxy modulation may be calculated based on ybi sin(27i it), where γ is the electron gyromagnetic ratio for the magneto-optical defect center material, bi is a selected projected magnitude for the proxy magnetic field, is selected frequency for the proxy magnetic field. In some

implementations, the selected projected magnitude for the proxy magnetic field may be between 100 picoTeslas and 1 microTesla. In some implementations, the selected frequency for the proxy magnetic field may be between 0 Hz and 100 kHz.

Spin Relaxometry Based Molecular Sequencing

[0216] According to some embodiments, a method for detecting a target molecule may comprise: allowing a fluid containing the target molecule to pass by a complementary moiety attached to a paramagnetic ion so as to cause the complementary moiety and the paramagnetic ion to change a position; detecting a magnetic effect change caused by the change in position of the paramagnetic ion; and identifying the target molecule based on the identity of the

complementary moiety and the detected magnetic effect change.

[0217] According to some embodiments, the detecting a magnetic effect change comprises detecting a change in spin relaxation of an electron spin center.

[0218] According to some embodiments, the electron spin center comprises one or more of diamond nitrogen vacancy (DNV) centers, defect centers in silicon carbide, or defect centers in silicon.

[0219] According to some embodiments, the detecting a magnetic effect change comprises detecting a change in the spin relaxation time of the electron spin center.

[0220] According to some embodiments, the detecting a magnetic effect change comprises detecting a change in photoluminescence from the electron spin center.

[0221] According to some embodiments, the detecting a magnetic effect change is performed by detecting a change in an electrical read out.

[0222] According to some embodiments, the magnetic effect change is detected based on the fluid containing the target molecule passing through a pore of a substrate.

[0223] According to some embodiments, the method further comprises detecting a change in ionic current as the target molecule is in the pore, wherein the identifying the target molecule is further based on the detected change in the ionic current. [0224] According to some embodiments, the substrate comprises an electron spin center, and the detecting a magnetic effect change comprises detecting a change in spin relaxation of the electron spin center.

[0225] According to some embodiments, the substrate comprises diamond, and the electron spin center comprises one or more diamond nitrogen vacancy (DNV) centers.

[0226] According to some embodiments, the substrate comprises DNV centers arranged in a band surrounding the pore.

[0227] According to some embodiments, the paramagnetic ion is attached to an inner surface of the pore via a ligand attachment of the paramagnetic ion.

[0228] According to some embodiments, the paramagnetic ion is attached to the

complementary molecule. According to some embodiments, the paramagnetic ion is one of Gd3+, another Lathanide series ion, or Manganese.

[0229] According to some embodiments, the target molecule is part of a DNA molecule.

[0230] According to some embodiments, the identifying the target molecule is further based on a second effect detecting technique other than the magnetic effect change.

[0231] According to some embodiments, a method for detecting target moieties of a target molecule may comprise: allowing a fluid containing the target molecule to pass by a plurality of complementary moieties, each of the plurality of complementary moieties attached to a different respective paramagnetic ion and specific to a respective of the target moieties, so as to cause a respective complementary moiety and paramagnetic ion to change a position; detecting a magnetic effect change caused by the change in position of a respective of the paramagnetic ions for each of the plurality of target moieties; and identifying the target moieties based on the identities of the complementary moieties and the detected magnetic effect changes.

[0232] According to some embodiments, the detecting a magnetic effect change for each of the plurality of target moieties comprises detecting a change in spin relaxation of an electron spin center.

[0233] According to some embodiments, a system for detecting a target molecule comprises: a substrate comprising an electron spin center; a complementary moiety attached to a paramagnetic ion, which is attached to the substrate; a magnetic effect detector arranged to detect a magnetic effect change of the electron spin center caused by a change in position of the paramagnetic ion due to the target molecule passing by the complementary moiety; and a processor configured to identify the target molecule based on the identity of the complementary moiety and the detected magnetic effect change.

[0234] According to some embodiments, the magnetic effect detector may comprise a light source arranged to direct excitation light onto the electron spin center; and a light detector arranged to receive photoluminescence light from the electron spin center based on the excitation light.

[0235] According to some embodiments, the system for detecting target moieties of a target molecule comprises: a substrate comprising a plurality of electron spin centers; a plurality of complementary moieties attached to respective of a plurality of paramagnetic ions, which are attached to the substrate, each of the plurality of complementary moieties attached to a different respective paramagnetic ion and specific to a respective of the target moieties; a magnetic effect detector arranged to detect, for each of the target moieties, a magnetic effect change of a respective electron spin center caused by a change in position of a respective of the paramagnetic ions due to the target moieties passing by a respective of the complementary moieties; and a processor configured to identify the target moieties based on the identities of the complementary moieties and detected magnetic effect changes.

[0236] According to some embodiments, a method for detecting target moieties of a target molecule may comprise: allowing a fluid containing the target molecule to pass by a plurality of complementary moieties, each of the plurality of target moieties attached to a different respective paramagnetic ion and specific to a respective of the complementary moieties, so as to cause a respective target moiety and paramagnetic ion to change a position; detecting a magnetic effect change caused by the change in position of a respective of the paramagnetic ions for each of the plurality of target moieties; and identifying the target moieties based on the identities of the complementary moieties and the detected magnetic effect changes.

Micro Air Vehicle Implementation of Magnetometers

[0237] Some embodiments relate to a system that includes a plurality of unmanned aerial systems (UASs) and a plurality of magnetometers each attached to a respective one of the UASs. Each of the magnetometers are configured to generate a vector measurement of a magnetic field. Some systems also include a central processing unit in communication with each of the plurality of magnetometers. The central processing unit can be configured to receive, from each of the plurality of magnetometers, a first set of vector measurements and corresponding locations. The corresponding locations can indicate where a respective magnetometer was when the respective vector measurement of the first set of vector measurements was taken. The central processing unit can also configured to generate a magnetic baseline map using the first set of vector measurements and receive, from a first magnetometer of the plurality of magnetometers, a first vector measurement and a first corresponding location. The central processing unit can further configured to compare the first vector measurement with the magnetic baseline map using the first corresponding location to determine a first difference vector and determine that a magnetic object is in an area corresponding to the area of the magnetic baseline map based on the first difference vector.

[0238] Some embodiments relate to a method that includes receiving, from each of a plurality of magnetometers, a first set of vector measurements and corresponding locations. Each of the magnetometers can be attached to one of a plurality of unmanned aerial systems (UASs). Each of the magnetometers can be configured to generate a vector measurement of a magnetic field. The corresponding locations indicate where a respective magnetometer was when the respective vector measurement of the first set of vector measurements was taken. Some methods also include generating a magnetic baseline map using the first set of vector measurements and receiving, from a first magnetometer of the plurality of magnetometers, a first vector

measurement and a first corresponding location. Some methods further include comparing the first vector measurement with the magnetic baseline map using the first corresponding location to determine a first difference vector. Some methods also include determining that a magnetic object is in an area corresponding to the area of the magnetic baseline map based on the first difference vector.

[0239] Some embodiments relate to a system that includes a plurality of magnetometers that are each configured to generate a vector measurement of a magnetic field. Some systems also include a central processing unit that can be communicatively coupled to each of the

magnetometers. The central processing unit can be configured to receive from each of the plurality of magnetometers the respective vector measurement of the magnetic field. The central processing unit can be further configured to compare each of the vector measurements to determine differences in the vector measurements and to determine, based on the differences in the vector measurements, that a magnetic object is near the plurality of magnetometers. [0240] Some embodiments relate to a method that includes receiving, from each of a plurality of magnetometers, a respective vector measurement of a magnetic field. Some methods also include comparing each of the vector measurements to determine differences in the vector measurements. Some methods further include determining, based on the differences in the vector measurements, that a magnetic object is near the plurality of magnetometers.

[0241] Some embodiments relate to a system that includes a first magnetometer configured to detect a first vector measurement of a magnetic field. The magnetic field can be generated by a magnetic device. Some systems also include a second magnetometer configured to detect a second vector measurement of the magnetic field. The first magnetometer and the second magnetometer can be spaced apart from one another. Some systems further include a processor in communication with the first magnetometer and the second magnetometer. The processor can be configured to determine a location of the magnetic device in a three-dimensional space based on the first vector measurement and the second vector measurement.

Buoy Implementation of Magnetometers

[0242] Some embodiments relate to systems that include a plurality of unmanned aerial systems (UASs) and a plurality of magnetometers each attached to a respective one of the UASs. Each of the magnetometers are configured to generate a vector measurement of a magnetic field. Some systems also include a central processing unit in communication with each of the plurality of magnetometers. The central processing unit can be configured to receive, from each of the plurality of magnetometers, a first set of vector measurements and corresponding locations. The corresponding locations may indicate where a respective magnetometer was when the respective vector measurement of the first set of vector measurements was taken. The central processing unit can also be configured to generate a magnetic baseline map using the first set of vector measurements and receive, from a first magnetometer of the plurality of magnetometers, a first vector measurement and a first corresponding location. The central processing unit can be further configured to compare the first vector measurement with the magnetic baseline map using the first corresponding location to determine a first difference vector and determine that a magnetic object is in an area corresponding to the area of the magnetic baseline map based on the first difference vector.

[0243] Some embodiments relate to methods that include receiving, from each of a plurality of magnetometers, a first set of vector measurements and corresponding locations. Each of the magnetometers can be attached to one of a plurality of unmanned aerial systems (UASs). Each of the magnetometers can be configured to generate a vector measurement of a magnetic field. The corresponding locations can indicate where a respective magnetometer was when the respective vector measurement of the first set of vector measurements was taken. Some embodiments relate to methods that also include generating a magnetic baseline map using the first set of vector measurements and receiving, from a first magnetometer of the plurality of magnetometers, a first vector measurement and a first corresponding location. Some embodiments relate to methods that further include comparing the first vector measurement with the magnetic baseline map using the first corresponding location to determine a first difference vector. Some embodiments relate to methods that also include determining that a magnetic object is in an area corresponding to the area of the magnetic baseline map based on the first difference vector.

[0244] Some embodiments relate to systems that include a plurality of magnetometers that are each configured to generate a vector measurement of a magnetic field. Some systems also include a central processing unit that is communicatively coupled to each of the magnetometers. The central processing unit can be configured to receive from each of the plurality of magnetometers the respective vector measurement of the magnetic field. The central processing unit can be further configured to compare each of the vector measurements to determine differences in the vector measurements and to determine, based on the differences in the vector measurements, that a magnetic object is near the plurality of magnetometers.

[0245] Some embodiments relate to methods that include receiving, from each of a plurality of magnetometers, a respective vector measurement of a magnetic field. Some methods also include comparing each of the vector measurements to determine differences in the vector measurements. Some methods further include determining, based on the differences in the vector measurements, that a magnetic object is near the plurality of magnetometers.

[0246] Some embodiments relate to systems that include a first magnetometer configured to detect a first vector measurement of a magnetic field. The magnetic field can be generated by a magnetic device. Some systems also include a second magnetometer configured to detect a second vector measurement of the magnetic field. The first magnetometer and the second magnetometer can be spaced apart from one another. Some systems can further include a processor in communication with the first magnetometer and the second magnetometer. The processor can be configured to determine a location of the magnetic device in a three- dimensional space based on the first vector measurement and the second vector measurement.

Di-Lateration Using Magnetometers

[0247] Some embodiments relate to systems that include a plurality of unmanned aerial systems (UASs) and a plurality of magnetometers each attached to a respective one of the UASs. Each of the magnetometers are configured to generate a vector measurement of a magnetic field. Some systems also include a central processing unit in communication with each of the plurality of magnetometers. The central processing unit can be configured to receive, from each of the plurality of magnetometers, a first set of vector measurements and corresponding locations. The corresponding locations can indicate where a respective magnetometer was when the respective vector measurement of the first set of vector measurements was taken. The central processing unit can also be configured to generate a magnetic baseline map using the first set of vector measurements and receive, from a first magnetometer of the plurality of magnetometers, a first vector measurement and a first corresponding location. The central processing unit can be further configured to compare the first vector measurement with the magnetic baseline map using the first corresponding location to determine a first difference vector and determine that a magnetic object is in an area corresponding to the area of the magnetic baseline map based on the first difference vector.

[0248] Some embodiments relate to methods that include receiving, from each of a plurality of magnetometers, a first set of vector measurements and corresponding locations. Each of the magnetometers can be attached to one of a plurality of unmanned aerial systems (UASs). Each of the magnetometers can be configured to generate a vector measurement of a magnetic field. The corresponding locations can indicate where a respective magnetometer was when the respective vector measurement of the first set of vector measurements was taken. Some methods also include generating a magnetic baseline map using the first set of vector measurements and receiving, from a first magnetometer of the plurality of magnetometers, a first vector

measurement and a first corresponding location. Some methods further include comparing the first vector measurement with the magnetic baseline map using the first corresponding location to determine a first difference vector. Some methods also include determining that a magnetic object is in an area corresponding to the area of the magnetic baseline map based on the first difference vector. [0249] Some embodiments relate to systems that include a plurality of magnetometers that are each configured to generate a vector measurement of a magnetic field. Some systems also include a central processing unit that is communicatively coupled to each of the magnetometers. The central processing unit can be configured to receive from each of the plurality of magnetometers the respective vector measurement of the magnetic field. The central processing unit can be further configured to compare each of the vector measurements to determine differences in the vector measurements and to determine, based on the differences in the vector measurements, that a magnetic object is near the plurality of magnetometers.

[0250] Some embodiments relate to methods that include receiving, from each of a plurality of magnetometers, a respective vector measurement of a magnetic field. Some methods also include comparing each of the vector measurements to determine differences in the vector measurements. Some methods further include determining, based on the differences in the vector measurements, that a magnetic object is near the plurality of magnetometers.

[0251] Some embodiments relate to systems that include a first magnetometer configured to detect a first vector measurement of a magnetic field. The magnetic field can be generated by a magnetic device. Some systems also include a second magnetometer configured to detect a second vector measurement of the magnetic field. The first magnetometer and the second magnetometer can be spaced apart from one another. Some systems further include a processor in communication with the first magnetometer and the second magnetometer. The processor can be configured to determine a location of the magnetic device in a three-dimensional space based on the first vector measurement and the second vector measurement.

Geolocation of Magnetic Sources Using Magnetometers

[0252] Some embodiments relate to a system including one or more diamond nitrogen vacancy (DNV) sensors and a controller. The controller can be configured to activate the DNV sensors, receive a set of vector measurements from the DNV sensors, and determine an angle of a magnetic source relative to the one or more DNV sensors based on the received set of vector measurements from the DNV sensors. In other implementations, the controller may be configured to determine geolocation of a magnetic source relative to the one or more DNV sensors based on the received set of vector measurements from the DNV sensors.

[0253] Some embodiments relate to a geolocating device that includes one or more diamond nitrogen vacancy (DNV) sensors and means for activating the DNV sensors, receiving a set of vector measurements from the DNV sensors, and determining an angle of a magnetic source relative to the one or more DNV sensors based on the received set of vector measurements from the DNV sensors.

Localization of Subsurface Liquids Using Magnetometers

[0254] Some embodiments relate to a system for locating a subsurface liquid. The system includes an excitation coil configured to induce a magnetic resonance in a subsurface liquid, an array of magnetometers associated with the excitation coil and configured to detect a magnetic vector of the magnetic resonance excited subsurface liquid, and a controller in communication with the array of magnetometers and configured to locate the subsurface liquid based on magnetic signals output from the array of magnetometers.

[0255] In some implementations, the array of magnetometers is an array of DNV

magnetometers. In some implementations, the array of magnetometers is an array of SQUIDs. In some implementations, the excitation coil is a proton spin resonance excitation coil. In some implementations, the excitation coil and the array of magnetometers are mounted to a

substructure. In some implementations, the controller is configured to deactivate the array of magnetometers during adiabatic passage preparation of the magnetic resonance signal. In some implementations, deactivating the array of magnetometers comprises deactivating an optical excitation source. In some implementations, deactivating the array of magnetometers comprises deactivating a RF excitation source. In some implementations, deactivating the array of magnetometers comprises deactivating an optical excitation source and a RF excitation source. In some implementations, the controller is configured to record an oscillatory proton (lH) magnetic resonance (MR) Larmor precession in Earth's field by the array of magnetometers. In some implementations, the controller is configured to filter a local Earth field from a magnetic signal detected by the array of magnetometers. In some implementations, the filtering comprises periodic filtering ("AC") pulse sequence operation of the magnetometers. In some

implementations, the filtering comprises reversal of XH magnetization in alternating signal co- additions. In some implementations, locating the subsurface liquid includes the controller generating a numerical location of the subsurface liquid. In some implementations, locating the subsurface liquid includes the controller generating a two-dimensional reconstruction of the subsurface liquid. In some implementations, locating the subsurface liquid includes the controller generating a three-dimensional reconstruction of the subsurface liquid. In some implementations, the subsurface liquid is oil. In some implementations, the subsurface liquid is water.

[0256] Some embodiments relate to methods for locating a subsurface liquid. Some methods include activating a proton spin resonance excitation coil, activating an array of magnetometers, recording an oscillatory XH MR precession in Earth's field by the array of magnetometers, and generating a location of the subsurface liquid based on the recorded oscillatory XH MR precession.

[0257] In some implementations, the array of magnetometers is an array of DNV

magnetometers. In some implementations, the array of magnetometers is an array of SQUIDs. In some implementations, the proton spin resonance excitation coil and the array of magnetometers are mounted to a substructure. In some implementations, the method further includes

deactivating the array of magnetometers during adiabatic passage preparation. In some implementations, deactivating the array of magnetometers comprises deactivating an optical excitation source. In some implementations, deactivating the array of magnetometers comprises deactivating a RF excitation source. In some implementations, deactivating the array of magnetometers comprises deactivating an optical excitation source and a RF excitation source. In some implementations, the method further includes filtering a local Earth field from a magnetic signal detected by the array of magnetometers. In some implementations, the filtering includes AC filtering pulse sequence. In some implementations, the filtering includes reversal of 1H magnetization in alternating signal co-additions. In some implementations, generating a location of the subsurface liquid includes generating a numerical location of the subsurface liquid. In some implementations, generating a location of the subsurface liquid includes generating a two-dimensional reconstruction of the subsurface liquid. In some implementations, generating a location of the subsurface liquid includes generating a three-dimensional reconstruction of the subsurface liquid. In some implementations, the subsurface liquid is oil .In some implementations, the subsurface liquid is water.

[0258] Some embodiments relate to an apparatus. The apparatus includes a substructure, a proton spin resonance excitation coil mounted to the substructure and configured to induce a magnetic resonance in a subsurface liquid, an array of DNV magnetometers mounted to the substructure and configured to detect a magnetic vector of the magnetic resonance excited subsurface liquid, and a controller in communication with the array of magnetometers. The controller is configured to record an oscillatory XH MR precession in Earth's field by the array of magnetometers and locate the subsurface liquid based on magnetic signals output from the array of magnetometers.

[0259] In some implementations, the controller is configured to deactivate the array of DNV magnetometers during adiabatic passage preparation. In some implementations, deactivating the array of magnetometers comprises deactivating an optical excitation source. In some

implementations, deactivating the array of magnetometers comprises deactivating a RF excitation source. In some implementations, deactivating the array of magnetometers comprises deactivating an optical excitation source and a RF excitation source. In some implementations, the controller is further configured to filter a local Earth field from a magnetic signal detected by the array of magnetometers. In some implementations, the filtering comprises AC filtering pulse sequence. In some implementations, the filtering comprises reversal of 1H magnetization in alternating signal co-additions. In some implementations locating the subsurface liquid includes the controller generating a numerical location of the subsurface liquid. In some implementations, locating the subsurface liquid includes the controller generating a two-dimensional

reconstruction of the subsurface liquid. In some implementations, locating the subsurface liquid includes the controller generating a three-dimensional reconstruction of the subsurface liquid. In some implementations, the subsurface liquid is oil. In some implementations, the subsurface liquid is water.

[0260] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the following drawings and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0261] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims, in which:

[0262] FIG. 1 illustrates one orientation of an Nitrogen- Vacancy (NV) center in a diamond lattice;

[0263] FIG. 2 illustrates an energy level diagram showing energy levels of spin states for the NV center; [0264] FIG. 3 A is a schematic diagram illustrating a NV center magnetic sensor system;

[0265] FIG. 3B is a schematic diagram illustrating a NV center magnetic sensor system with a waveplate in accordance with some illustrative embodiments;

[0266] FIG. 4A is a graph illustrating the fluorescence as a function of an applied RF frequency of an NV center along a given direction for a zero magnetic field, and also for a nonzero magnetic field having a component along the NV axis;

[0267] FIG. 4B is a graph illustrating the fluorescence as a function of an applied RF frequency for four different NV center orientations for a non-zero magnetic field;

[0268] FIG. 5 is a schematic illustrating a Ramsey sequence of optical excitation pulses and RF excitation pulses;

[0269] FIG. 6A is a schematic diagram illustrating some embodiments of a magnetic field detection system;

[0270] FIG. 6B is another schematic diagram illustrating some embodiments of a magnetic field detection system;

[0271] FIG. 6C is another schematic diagram illustrating some embodiments of a magnetic field detection system;

Example Magnetometer

[0272] FIG. 7 is an illustrative a perspective view depicting some embodiments of a magneto- optical defect center magnetometer;

[0273] FIG. 8 is an illustrative perspective view of the magneto-optical defect center magnetometer of FIG. 7 with a top plate removed;

[0274] FIG. 9 is an illustrative top view depicting the magneto-optical defect center magnetometer of FIG. 7 with the top plate removed;

[0275] FIG. 10 is an illustrative cross-sectional view taken along line A-A and depicting the magneto-optical defect center magnetometer of FIG. 7 with the top plate removed;

[0276] FIG. 11 is an illustrative cross-sectional view taken along line B-B and depicting the magneto-optical defect center magnetometer of FIG. 7 with the top plate attached;

[0277] FIG. 12 is an illustrative perspective cross-sectional view taken along line B-B and depicting the DNV magnetometer of FIG. 7 with the top plate attached;

[0278] FIG. 13 is a perspective view of a RF excitation source with a plurality of coils according to some embodiments; [0279] FIG. 14A is a side view of the coils and a RF feed connector of the RF excitation source of FIG. 13;

[0280] FIG. 14B is a top view of the coils and a RF feed connector of the RF excitation source of FIG. 13;

[0281] FIG. 15A is a graph illustrating the magnetic field generated by the RF excitation source at 2GHz in the region of the NV diamond material for a five spiral shaped coil arrangement;

[0282] FIG. 15B is a graph illustrating the magnetic field generated by the RF excitation source at 3 GHz in the region of the NV diamond material for the five spiral shaped coil arrangement;

[0283] FIG. 15C is a graph illustrating the magnetic field generated by the RF excitation source at 4GHz in the region of the NV diamond material for the five spiral shaped coil arrangement;

[0284] FIG. 16 is a table illustrating the electric field and magnetic field generated by the RF excitation source in a region of the NV diamond material at frequencies from 2.0 to 4.0 GHz for the five layer coil arrangement with spiral shaped coils;

[0285] FIG. 17 is a side-view illustrating details of the optical waveguide assembly of a magnetic field sensor system according to some embodiments;

[0286] FIG. 18 is a depiction of a cross-section of a light pipe and an associated mount according to some embodiments;

[0287] FIG. 19 is a top-down view of an optical waveguide assembly of a magnetic field sensor system according to some embodiments;

[0288] FIG. 20 is a schematic diagram illustrating a dichroic optical filter and the behavior of light interacting therewith according to some embodiments;

[0289] FIG 21 is a schematic block diagram of some embodiments of an optical filtration system;

[0290] FIG. 22 is a schematic block diagram of some embodiments of an optical filtration system;

[0291] FIG. 23 is a diagram of an optical filter according to some embodiments;

[0292] FIG. 24 is a diagram of an optical filter according to some embodiments; [0293] FIG. 25 is an illustrative perspective view depicting some embodiments of a magneto- optical defect center magnetometer;

[0294] FIG. 26 is an illustrative perspective view of the magneto-optical defect center magnetometer of FIG. 25 with a top plate removed;

[0295] FIG. 27 is an illustrative top view depicting the magneto-optical defect center magnetometer of FIG. 25 with the top plate removed;

[0296] FIG. 28 is an illustrative cross-sectional view taken along line A-A and depicting the magneto-optical defect center magnetometer of FIG. 25 with the top plate removed;

[0297] FIG. 29 is an illustrative cross-sectional view taken along line B-B and depicting the magneto-optical defect center magnetometer of FIG. 25 with the top plate attached;

[0298] FIG. 30 is an illustrative perspective cross-sectional view taken along line B-B and depicting the magneto-optical defect center magnetometer of FIG. 25 with the top plate attached;

[0299] FIG. 31 is an illustrative top view depicting the top plate of the magneto-optical defect center magnetometer of FIG. 25;

[0300] FIG. 32 is an illustrative perspective view of support elements for one or more components of the magneto-optical defect center magnetometer of FIG. 25;

[0301] FIG. 33 is a schematic illustrating details of the optical light source of the magnetic field detection system according to some embodiments;

[0302] FIG. 34 illustrates the illumination volume in NV diamond material for a readout optical light source and a reset optical light source of the optical light source of the magnetic field detection system according to an embodiment;

[0303] FIG. 35 illustrates a RF sequence according to some embodiments;

[0304] FIG. 36 is a magnetometry curve in the case of a continuous optical excitation RF pulse sequence according to some embodiments;

[0305] FIG. 37 is a magnetometry curve in the case of a continuous optical excitation RF pulse sequence where the waveform has been optimized for collection intervals according to some embodiments;

[0306] FIG. 38 is magnetometry curve for the left most resonance frequency of FIG. 37 according to some embodiments;

[0307] FIG. 39 is a graph illustrating the dimmed luminescence intensity as a function of time for the region of maximum slope of FIG. 38; [0308] FIG. 40 is a graph illustrating the normalized intensity of the luminescence as a function of time for diamond NV material for a continuous optical illumination of the diamond

NV material in a RF sequence measurement;

[0309] FIG. 41 is a graph of a zoomed in region of FIG. 40;

Example Magnetometer with Additional Features

[0310] FIG. 42A illustrates an inside view of a magnetic field detection system in accordance with some illustrative embodiments;

[0311] FIG. 42B illustrates an inside view of a magnetic field detection system in accordance with some illustrative embodiments in which the NV diamond material is provided in a different orientation than in FIG. 42A;

[0312] FIG. 43 A illustrates a housing of the magnetic field detection system of FIG. 42 A, which includes a top plate, a bottom plate, one or more side plates, a main plate and a gasket;

[0313] FIG. 43B illustrates a bottom view of the housing of FIG. 43 A in which the bottom plate includes cooling fins;

[0314] FIG. 44A illustrates the top plate of the housing of FIG. 43 A;

[0315] FIG. 44B illustrates the bottom plate of the housing of FIG. 43 A;

[0316] FIG. 44C illustrates the side plate of the housing of FIG. 43 A;

[0317] FIG. 44D illustrates a top view of the main plate of the housing of FIG. 43 A;

[0318] FIG. 44E illustrates a bottom view of the main plate of the housing of FIG. 43 A;

[0319] FIG. 45 illustrates components fixed to a bottom side of the main plate of the housing of FIG. 44 A, where the components are provided between the bottom side of the main plate and a top side of the bottom plate;

[0320] FIG. 46A is a schematic diagram illustrating some embodiments of a portion of a magnetic field detection system;

[0321] FIG. 46B is a schematic diagram illustrating some embodiments of a portion of a magnetic field detection system with a different arrangement of the light sources than in FIG. 46A;

[0322] FIG. 47 illustrates some embodiments of an RF excitation source of a magnetic field detection system;

[0323] FIG. 48 illustrates some embodiments of an RF excitation source oriented on its side;

[0324] FIG. 49 illustrates some embodiments of a circuit board of an RF excitation source; [0325] FIG. 50A illustrates some embodiments of a diamond material coated with a metallic material from a top perspective view;

[0326] FIG. 50B illustrates some embodiments of a diamond material coated with a metallic material from a bottom perspective view;

[0327] FIG. 51 illustrates some embodiments of a standing-wave RF exciter system;

[0328] FIG. 52A illustrates some embodiments of a circuit diagram of a RF exciter system;

[0329] FIG. 52B illustrates some embodiments of a circuit diagram of another RF exciter system;

[0330] FIG. 53 A is a graph illustrating an applied RF field as a function of frequency for a prior exciter;

[0331] FIG. 53B is a graph illustrating an applied RF field as a function of frequency for some embodiments of an exciter;

[0332] FIG. 54 illustrates an optical light source with adjustable spacing features in accordance with some illustrative embodiments;

[0333] FIG. 55 illustrates a cross section as viewed from above of a portion of the optical light source in accordance with some illustrative embodiments;

[0334] FIG. 56 is a schematic diagram illustrating a waveplate assembly in accordance with some illustrative embodiments;

[0335] FIG. 57 is a half-wave plate schematic diagram illustrating a change in polarization of light when the waveplate of FIG. 56 is a half-wave plate;

[0336] FIG. 58 is a quarter-wave plate schematic diagram illustrating a change in polarization of light when the waveplate of FIG. 56 is a quarter-wave plate;

[0337] FIGS. 59A-59C are three-dimensional views of an element holder assembly in accordance with some illustrative embodiments;

[0338] FIG. 60 is a circuit outline of a radio frequency element circuit board in accordance with some illustrative embodiments;

[0339] FIGS. 61 A and 61B are three-dimensional views of an element holder base in accordance with some illustrative embodiments;

[0340] FIG. 62 is a schematic illustrating some implementations of a Vivaldi antenna;

[0341] FIG. 63 is a schematic illustrating some implementations of an array of Vivaldi antennae; [0342] FIG. 64 is a block diagram of some RF systems for the magneto-defect center sensor;

[0343] FIG. 65 illustrates a magnet mount assembly in accordance with some illustrative embodiments;

[0344] FIG. 66 illustrates parts of a disassembled magnet ring mount in accordance with some illustrative embodiments;

[0345] FIG. 67 illustrates parts of a disassembled magnet ring mount in accordance with some illustrative embodiments;

[0346] FIG. 68 illustrates a magnet ring mount showing locations of magnets in accordance with some illustrative embodiments;

[0347] FIG. 69 illustrates a bias magnet ring mount in accordance with some illustrative embodiments;

[0348] FIG. 70 illustrates a bias magnet ring mount in accordance with some illustrative embodiments;

Magneto-Optical Defect Center with Waveguide

[0349] FIG. 71 is a diagram illustrating possible paths of light emitted from a material with defect centers in accordance with some illustrative embodiments;

[0350] FIG. 72A is a diagram illustrating possible paths of light emitted from a material with defect centers and a rectangular waveguide in accordance with some illustrative embodiments;

[0351] FIG. 72B is a three-dimensional view of the material and rectangular waveguide of FIG. 72A in accordance with some illustrative embodiments;

[0352] FIG. 73 A is a diagram illustrating possible paths of light emitted from a material with defect centers and an angled waveguide in accordance with some illustrative embodiments;

[0353] FIG. 73B is a three-dimensional view of the material and angular waveguide of FIG. 73 A in accordance with some illustrative embodiments;

[0354] FIG. 74A is a diagram illustrating possible paths of light emitted from a material with defect centers and a three-dimensional waveguide in accordance with some illustrative embodiments;

[0355] FIG. 74B is a three-dimensional view of the material and a three-dimensional waveguide of FIG. 74 A in accordance with some illustrative embodiments;

[0356] FIG. 74C-74F are two-dimensional cross-sectional drawings of a three-dimensional waveguide in accordance with some illustrative embodiments; [0357] FIG. 75 is a diagram illustrating a material attached to a waveguide in accordance with some illustrative embodiments;

[0358] FIG. 76 is a flow chart of a method of forming a material with a waveguide in accordance with some illustrative embodiments;

[0359] FIG. 77 is a flow chart of a method of forming a material with a waveguide in accordance with some illustrative embodiments;

Drift Error Compensation

[0360] FIG. 78A is a graph illustrating fluorescence reduction as a function of an applied RF frequency for a positive spin state of an NV center orientation;

[0361] FIG. 78B is a graph illustrating fluorescence reduction as a function of an applied RF frequency for a negative spin state of the NV center orientation of FIG. 78 A;

[0362] FIG. 79A illustrates a measurement collection scheme for vertical drift error compensation according to some embodiments;

[0363] FIG. 79B shows a measurement collection scheme for vertical drift error compensation according to some embodiments;

[0364] FIG. 79C shows a measurement collection scheme for horizontal drift error compensation according to some embodiments;

Thermal Drift Error Compensation

[0365] FIG. 80 is a unit cell diagram of the crystal structure of a diamond lattice having a standard orientation;

[0366] FIG. 81A is a graph illustrating two fluorescence curves as a function of RF frequency for two different temperatures where electron spin resonances 1, 4, 6 and 7 are selected in the case where the external magnetic field is aligned with the bias magnetic field;

[0367] FIG. 8 IB is a graph illustrating two fluorescence curves as a function of RF frequency for two different magnetic fields where electron spin resonances 1, 4, 6 and 7 are selected in the case where the external magnetic field is aligned with the bias magnetic field;

[0368] FIG. 81C is a graph illustrating two fluorescence curves as a function of RF frequency for two different magnetic fields where electron spin resonances 1, 4, 6 and 7 are selected in the case of a general external magnetic field;

Pulsed RF Methods of Continuous Wave Measurement [0369] FIG. 82 illustrates a magneto-optical defect center material excitation scheme operating in CW Sit mode using a CW laser functioning throughout and a pulsed RF excitation source operating at a single frequency having a pulse repetition period of approximately 110 μβ;

[0370] FIG. 83 illustrates a magneto-optical defect center material excitation scheme operating in CW Sweep mode using a CW laser functioning throughout and a pulsed RF excitation source swept at different frequencies having a pulse repetition period of approximately 1100 μβ;

High Speed Sequential Cancellation for Pulsed Mode

[0371] FIG. 84 is a graphical diagram of a magnetometer system using a reference signal acquisition prior to RF pulse excitation sequence and measured signal acquisition;

[0372] FIG. 85 is a graphical diagram of a magnetometer system omitting the reference signal acquisition of FIG. 5 prior to RF pulse excitation sequence and measured signal acquisition;

[0373] FIG. 86 is a graphical diagram depicting a reference signal intensity relative to detune frequency and a measured signal intensity relative to detune frequency;

[0374] FIG. 87 is a graphical diagram depicting a slope relative to laser pulse width for a system implementing a reference signal and a system omitting the reference signal;

[0375] FIG. 88 is a graphical diagram depicting a sensitivity relative to polarization pulse length for a system implementing a reference signal and a system omitting the reference signal;

[0376] FIG. 89 is a process diagram for operating a magnetometer without using a reference signal;

Photodetector Circuit Saturation Mitigation

[0377] FIG. 90 is a schematic block diagram of some embodiments of a circuit saturation mitigation system;

[0378] FIG. 91 is a schematic block diagram of some embodiments of an optical detection circuit;

[0379] FIG. 92 is a schematic block diagram of some embodiments of system for a circuit saturation mitigation system;

[0380] FIG. 93 A is a diagram of the power output of a low intensity light signal according to some embodiments;

[0381] FIG. 93B is a diagram of the power output of a high intensity light signal according to some embodiments;

[0382] FIG. 93C is a diagram of the voltage output according to some embodiments; [0383] FIG. 93D is a diagram of the voltage output according to some embodiments;

[0384] FIG. 94 is a diagram of the voltage output of an optical detection circuit according to some embodiments;

[0385] FIG. 95 is a diagram of the voltage output of an optical detection circuit according to some embodiments;

Shifted Magnetometry Adapted Cancellation for Pulse Sequence

[0386] FIG. 96 is a schematic illustrating a Ramsey sequence of optical excitation pulses and RF excitation pulses according to an operation of the system in some embodiments;

[0387] FIG. 97A is a free induction decay curve where a free precession time τ is varied using a Ramsey sequence in some embodiments;

[0388] FIG. 97B is a magnetometry curve where a RF detuning frequency Δ is varied using a Ramsey sequence in some embodiments;

[0389] FIG. 98 is a graphical diagram depicting a reference signal intensity relative to detune frequency and a measured signal intensity relative to detune frequency in accordance with some embodiments;

[0390] FIG. 99 is a plot showing a traditional magnetometry curve using a Ramsey sequence in accordance with some embodiments;

[0391] FIG. 100 is a plot showing an invented magnetometry curve using a Ramsey sequence in accordance with some embodiments;

[0392] FIG. 101 is a plot showing a combined magnetometry curve of a traditional and inverted curve in accordance with some embodiments;

Generation of Magnetic Field Proxy Through RF Dithering

[0393] FIG. 102 is a magnetometry curve for an example resonance frequency;

[0394] FIG. 103 is a process diagram depicting a process for generating a proxy magnetic reference signal;

[0395] FIG. 104 is a process diagram depicting a process for determining a processed proxy magnetic reference signal;

[0396] FIG. 105 is a process diagram depicting a process for generating a sensor attenuation curve of external magnetic fields as a function of frequency using proxy magnetic reference signals; [0397] FIG. 106 is a process diagram depicting a process for generating a calibrated noise floor as a function of frequency using proxy magnetic reference signals;

Spin Relaxometry Based Molecular Sequencing

[0398] FIG. 107 is a schematic diagram illustrating a system for detecting a target molecule according to embodiments;

[0399] FIG. 108 is a top view of a pore of the substrate shown in FIG. 107;

[0400] FIG. 109 is a magnified cross-sectional view of a portion of the side wall of a pore of the substrate shown in FIG. 107;

[0401] FIG. 11 OA is a graph illustrating the photoluminescence of a spin center as a function of time in the case where the paramagnetic ion is relatively far from the spin center;

[0402] FIG. 110B is a graph illustrating the photoluminescence of a spin center as a function of time in the case where the paramagnetic ion is relatively close to the spin center;

[0403] FIG. I l l illustrates a target molecule with individual target moities passing through a pore of the substrate;

[0404] FIG. 112 is a graph illustrating the magnetic effect signal as a function of time for four different spin centers;

[0405] FIG. 113 is a schematic diagram illustrating a system for detecting a target molecule according to embodiments using both a magnetic effect detector and a second effect detector;

[0406] FIG. 114 illustrates embodiments of the substrate of the system which includes electronic read out of the magnetic spin change;

Micro Air Vehicle and Buoy Arrays of Magnetometer Sensors

[0407] FIGS. 115A and 115B are graphs illustrating the frequency response of a DNV sensor in accordance with some illustrative embodiments;

[0408] FIG. 116A is a diagram of NV center spin states in accordance with some illustrative embodiments;

[0409] FIG. 116B is a graph illustrating the frequency response of a DNV sensor in response to a changed magnetic field in accordance with some illustrative embodiments;

[0410] FIGS. 117A and 117B are diagrams of a buoy-based DNV sensor array in accordance with some illustrative embodiments;

[0411] FIG. 118 is a flow chart of a method for monitoring for magnetic objects in accordance with some illustrative embodiments; [0412] FIG. 119 is a diagram of a buoy -based DNV sensor array in accordance with some illustrative embodiments;

[0413] FIG. 120 is a diagram of an aerial DNV sensor array in accordance with some illustrative embodiments;

[0414] FIG. 121 is a flow chart of a method for monitoring for magnetic objects in accordance with some illustrative embodiments;

Di-Lateration Using Magnetometers

[0415] FIGS. 122A-122C are diagrams illustrating di-lateration techniques in accordance with some illustrative embodiments;

Geolocation of Magnetic Sources Using Magnetometers

[0416] FIG. 123 is a schematic illustrating a controller and several DNV sensors for detecting an angle and/or position of a magnetic source relative to the DNV sensors;

Localization of Subsurface Liquids Using Magnetometers

[0417] FIG. 124 is an illustrative overview of a system for localization of a subsurface liquid using a proton spin resonance excitation coil for inducing a magnetization in the subsurface liquid and an array of vector magnetometers to detect the location of the subsurface liquid;

[0418] FIG. 125 is an illustrative overview of sets of magnetometers of FIG. 124 outputting detection signals from the magnetized subsurface liquid;

[0419] FIG. 126 is an illustrative view depicting the detected location of the subsurface liquid based on the detection signals from the sets of magnetometers of FIG. 125;

[0420] FIG. 127 is a process diagram for an illustrative process for detecting the location of the subsurface liquid using the array of magnetometers;

System to Map and/or Monitor Hydraulic Fractures Using Magnetometers

[0421] FIGS. 128A-128B are diagrams illustrating examples of a high-level architecture of a system for mapping and monitoring of hydraulic fracture and an environment where the system operates, according to certain embodiments;

[0422] FIG. 129 is a high-level diagram illustrating an example of implementation of hydraulic fracturing of a well to release gas reserves, according to certain embodiments;

[0423] FIG. 130A is a diagram illustrating an example background magnetic signature of a well, according to certain embodiments; [0424] FIG. 130B is a diagram illustrating an example implementation of a mapping system for hydraulic fracturing of the well shown in FIG. 130A, according to certain embodiments;

[0425] FIG. 131 is a diagram illustrating an example of a method for mapping and monitoring of hydraulic fracture, according to certain embodiments;

[0426] FIG. 132 is a diagram illustrating examples of primary and secondary magnetic fields in the presence of a doped proppant, according to certain embodiments;

High Bit-Rate Magnetic Communication Using Magnetometers

[0427] FIGS. 133A-133B are diagrams illustrating examples of a high-level architecture of a magnetic communication transmitter and a schematic of a circuit of a controller, according to certain embodiments;

[0428] FIGS. 134A-134B are diagrams illustrating examples of a high-level architecture of a magnetic communication receiver and a set of amplitude modulated waveforms, according to certain embodiments;

[0429] FIG. 135 is a diagram illustrating an example of a method for providing a magnetic communication transmitter, according to certain embodiments;

[0430] FIG. 136 is a diagram illustrating an example of a data frame of a magnetic

communication transmitter, according to certain embodiments;

[0431] FIG. 137 is a diagram illustrating an example of motion compensation scheme, according to certain embodiments;

[0432] FIGS. 138A-138B are diagrams illustrating examples of throughput results with turning, rolling and low-frequency compensation, according to certain embodiments;

[0433] FIG. 139 is a diagram illustrating an example adaptive modulation scheme, according to certain embodiments;

[0434] FIGS. 140 A through 140C are diagrams illustrating components for implementing an example technique for multiple channel resolution, according to certain embodiments;

[0435] FIGS. 141 A-141B are diagrams illustrating single channel throughput variations versus transmitter-receiver distance, according to certain embodiments;

[0436] FIGS. 142A-142B are diagrams illustrating simulated performance results, according to certain embodiments;

Communication by Magnio Using Magnetometers [0437] FIG. 143 is a block diagram of a magnetic communication system in accordance with an illustrative embodiment;

[0438] FIGS. 144 A and 144B show the strength of a magnetic field versus frequency in accordance with an illustrative embodiment;

Navigation System Using Power Transmission and/or Communication System Using Magnetometers

[0439] FIG. 145 illustrates a low altitude flying object in accordance with some illustrative implementations;

[0440] FIG. 146 A illustrates a ratio of signal strength of two magnetic sensors, A and B, attached to wings of the UAS 102 as a function of distance, x, from a center line of a power in accordance with some illustrative implementations;

[0441] FIG. 146B illustrates a composite magnetic field (B-field) in accordance with some illustrative implementations;

[0442] FIG. 147 illustrates a high-level block diagram of an example UAS navigation system in accordance with some illustrative implementations;

[0443] FIG. 148 illustrates an example of a power line infrastructure;

[0444] FIGS. 149A and 149B illustrate examples of magnetic field distribution for overhead power lines and underground power cables;

[0445] FIG. 150 illustrates examples of magnetic field strength of power lines as a function of distance from the centerline;

[0446] FIG. 151 illustrates an example of a UAS equipped with DNV sensors in accordance with some illustrative implementations;

[0447] FIG. 152 illustrates a plot of a measured differential magnetic field sensed by the DNV sensors when in close proximity of the power lines in accordance with some illustrative implementations;

[0448] FIG. 153 illustrates an example of a measured magnetic field distribution for normal power lines and power lines with anomalies according to some implementations;

Defect Detection in Power Transmission Lines Using Magnetometers

[0449] FIGS. 154A and 154B are block diagrams of a system for detecting deformities in transmission lines in accordance with an illustrative embodiment; [0450] FIG. 155 illustrates current paths through a transmission line with a deformity in accordance with an illustrative embodiment;

[0451] FIG. 156 illustrates power transmission line sag between transmission towers in accordance with an illustrative embodiment;

[0452] FIG. 157 illustrates vector measurements indicating power transmission line sag in accordance with an illustrative embodiment;

[0453] FIG. 158 illustrates vector measurements along a path between adjacent towers in accordance with an illustrative embodiment;

In-Situ Power Charging Using Magnetometers

[0454] FIG. 159 is a block diagram of a vehicular system in accordance with an illustrative embodiment;

[0455] FIG. 160 is a flow chart of a method for charging a power source in accordance with an illustrative embodiment;

[0456] FIG. 161 is a graph of the strength of a magnetic field versus distance from the conductor in accordance with an illustrative embodiment;

Position Encoder Using Magnetometers

[0457] FIG. 162 is a schematic illustrating a position sensor system according to some embodiments;

[0458] FIG. 163 is a schematic illustrating a position sensor system including a rotary position encoder;

[0459] FIG. 164 is a schematic illustrating a top down view of a rotary position encoder;

[0460] FIG. 165 is a schematic illustrating a position sensor system including a linear position encoder;

[0461] FIG. 166 is a schematic illustrating a magnetic element arrangement of a position encoder according to some embodiments;

[0462] FIG. 167 is a schematic illustrating a magnetic element arrangement of a position encoder according to other embodiments;

[0463] FIG. 168 is a schematic illustrating a magnetic element arrangement of a position encoder according to other embodiments;

[0464] FIG. 169 is a schematic illustrating the relationship of a position sensor head and the magnetic elements of a position encoder; [0465] FIG. 170 is a graph of measured magnetic field intensity attributable to magnetic elements of a position encoder for a first magnetic field sensor and a second magnetic field sensor of a position sensor head;

[0466] FIG. 171 is a flow chart illustrating the process of determining a position utilizing a position sensor system according to some embodiments;

Wake Detector Using Magnetometers

[0467] FIG. 172 illustrates a low altitude flying object in accordance with some illustrative implementations;

[0468] FIG. 173 illustrates a magnetic field detector in accordance with some illustrative implementations;

[0469] FIGS. 174 A and 174B illustrate a portion of a detector array in accordance with some illustrative implementations;

Defect Detector Using Magnetometers

[0470] FIGS. 175 A and 175B are block diagrams of a system for detecting deformities in a material in accordance with an illustrative embodiment;

[0471] FIG. 176 illustrates current paths through a conductor with a deformity in accordance with an illustrative embodiment;

[0472] FIG. 177 is a flow diagram of a method for detecting deformities in accordance with an illustrative embodiment;

Ferro-Fluid Hydrophone Using Magnetometers

[0473] FIG. 178 is a schematic illustrating a hydrophone in accordance with some illustrative implementations;

[0474] FIG. 179 is a schematic illustrating a portion of a vehicle with a hydrophone in accordance with some illustrative implementations;

[0475] FIG. 180 is a schematic illustrating a portion of a vehicle with a hydrophone with a containing membrane in accordance with some illustrative implementations;

[0476] FIG. 181 is a schematic illustrating a portion of a vehicle with a hydrophone in accordance with some illustrative implementations;

[0477] FIG. 182 is a schematic illustrating a portion of a vehicle with a hydrophone with a containing membrane in accordance with some illustrative implementations;

Dissolved Ion Hydrophone Using Magnetometers [0478] FIGS. 183 A and 183B are diagrams illustrating hydrophone systems in accordance with illustrative embodiments; and

[0479] FIG. 184 is a diagram illustrating an example of a computing system for implementing some aspects of the subject technology.

[0480] It will be recognized that some or all of the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating embodiments with the explicit understanding that they will not be used to limit the scope or the meaning of the claims.

DETAILED DESCRIPTION

[0481] Atomic-sized magneto-optical defect centers, such as nitrogen-vacancy (NV) centers in diamond lattices, can have excellent sensitivity for magnetic field measurement and enable fabrication of small magnetic sensors. Magneto-optical defect center materials include but are not be limited to diamonds, Silicon Carbide (SiC), Phosphorous, and other materials with nitrogen, boron, carbon, silicon, or other defect centers. Diamond nitrogen vacancy (DNV) sensors may be maintained in room temperature and atmospheric pressure and can be even used in liquid environments. A green optical source (e.g., a micro-LED) can optically excite NV centers of the DNV sensor and cause emission of fluorescence radiation (e.g., red light) under off-resonant optical excitation. A magnetic field generated, for example, by a microwave coil can probe triplet spin states (e.g., with ms = -1, 0, +1) of the NV centers to split based upon an external magnetic field projected along the NV axis, resulting in two spin resonance frequencies. The distance between the two spin resonance frequencies is a measure of the strength of the external magnetic field. A photo detector can measure the fluorescence (red light) emitted by the optically excited NV centers.

[0482] Magneto-optical defect center materials are those that can modify an optical wavelength of light directed at the defect center based on a magnetic field in which the magneto-defect center material is exposed. In some implementations, the magneto-optical defect center material may utilize nitrogen vacancy centers. Nitrogen-vacancy (NV) centers are defects in a diamond's crystal structure. Synthetic diamonds can be created that have these NV centers. NV centers generate red light when excited by a light source, such as a green light source, and microwave radiation. When an excited NV center diamond is exposed to an external magnetic field, the frequency of the microwave radiation at which the diamond generates red light and the intensity of the generated red light change. By measuring this change and comparing the change to the microwave frequency that the diamond generates red light at when not in the presence of the external magnetic field, the external magnetic field strength can be determined. Accordingly,

NV centers can be used as part of a magnetic field sensor.

The NV Center, Its Electronic Structure, and Optical and RF Interaction

[0483] The NV center in a diamond comprises a substitutional nitrogen atom in a lattice site adjacent a carbon vacancy as shown in FIG. 1. The NV center may have four orientations, each corresponding to a different crystallographic orientation of the diamond lattice.

[0484] The NV center may exist in a neutral charge state or a negative charge state. The neutral charge state uses the nomenclature NV°, while the negative charge state uses the nomenclature NV, which is adopted in this description.

[0485] The NV center has a number of electrons, including three unpaired electrons, each one from the vacancy to a respective of the three carbon atoms adjacent to the vacancy, and a pair of electrons between the nitrogen and the vacancy. The NV center, which is in the negatively charged state, also includes an extra electron.

[0486] The NV center has rotational symmetry, and as shown in FIG. 2, has a ground state, which is a spin triplet with 3A2 symmetry with one spin state ms = 0, and two further spin states ms = +1, and ms = -1. In the absence of an external magnetic field, the ms = ±1 energy levels are offset from the ms = 0 due to spin-spin interactions, and the ms = ±1 energy levels are degenerate, i.e., they have the same energy. The ms = 0 spin state energy level is split from the ms = ±1 energy levels by an energy of approximately 2.87 GHz for a zero external magnetic field.

[0487] Introducing an external magnetic field with a component along the NV axis lifts the degeneracy of the ms = ±1 energy levels, splitting the energy levels ms = ±1 by an amount 2gμBBz, where g is the g-factor, μΒ is the Bohr magneton, and Bz is the component of the external magnetic field along the NV axis. This relationship is correct to a first order and inclusion of higher order corrections is a straightforward matter and will not affect the computational and logic steps in the systems and methods described below.

[0488] The NV center electronic structure further includes an excited triplet state 3E with corresponding ms = 0 and ms = ±1 spin states. The optical transitions between the ground state 3A2 and the excited triplet 3E are predominantly spin conserving, meaning that the optical transitions are between initial and final states that have the same spin. For a direct transition between the excited triplet 3E and the ground state 3A2, a photon of red light is emitted with a photon energy corresponding to the energy difference between the energy levels of the transitions.

[0489] There is, however, an alternative non-radiative decay route from the triplet 3E to the ground state 3A2 via intermediate electron states, which are thought to be intermediate singlet states A, E with intermediate energy levels. Significantly, the transition rate from the ms = ±1 spin states of the excited triplet 3E to the intermediate energy levels is significantly greater than the transition rate from the ms = 0 spin state of the excited triplet 3E to the intermediate energy levels. The transition from the singlet states A, E to the ground state triplet 3A2 predominantly decays to the ms = 0 spin state over the ms = ±1 spins states. These features of the decay from the excited triplet 3E state via the intermediate singlet states A, E to the ground state triplet 3A2 allows that if optical excitation is provided to the system, the optical excitation will eventually pump the NV center into the ms = 0 spin state of the ground state 3A2. In this way, the population of the ms = 0 spin state of the ground state 3A2 may be "reset" to a maximum polarization determined by the decay rates from the triplet 3E to the intermediate singlet states.

[0490] Another feature of the decay is that the fluorescence intensity due to optically stimulating the excited triplet 3E state is less for the ms = ±1 states than for the ms = 0 spin state. This is so because the decay via the intermediate states does not result in a photon emitted in the fluorescence band, and because of the greater probability that the ms = ±1 states of the excited triplet 3E state will decay via the non-radiative decay path. The lower fluorescence intensity for the ms = ±1 states than for the ms = 0 spin state allows the fluorescence intensity to be used to determine the spin state. As the population of the ms = ±1 states increases relative to the ms = 0 spin, the overall fluorescence intensity will be reduced.

The NV Center, or Magneto-Optical Defect Center, Magnetic Sensor System

[0491] FIG. 3 A is a schematic diagram illustrating a NV center magnetic sensor system 300A that uses fluorescence intensity to distinguish the ms = ±1 states, and to measure the magnetic field based on the energy difference between the ms = +1 state and the ms = -1 state, as manifested by the RF frequencies corresponding to each state. The system 300 A includes an optical excitation source 310, which directs optical excitation to an NV diamond material 320 with NV centers. The system further includes an RF excitation source 330, which provides RF radiation to the NV diamond material 320. Light from the NV diamond may be directed through an optical filter 350 to an optical detector 340.

[0492] The RF excitation source 330 may be a microwave coil, for example. The RF excitation source 330, when emitting RF radiation with a photon energy resonant with the transition energy between ground ms = 0 spin state and the ms = +1 spin state, excites a transition between those spin states. For such a resonance, the spin state cycles between ground ms = 0 spin state and the ms = +1 spin state, reducing the population in the ms = 0 spin state and reducing the overall fluorescence at resonances. Similarly, resonance and a subsequent decrease in fluorescence intensity occurs between the ms = 0 spin state and the ms = -1 spin state of the ground state when the photon energy of the RF radiation emitted by the RF excitation source is the difference in energies of the ms = 0 spin state and the ms = -1 spin state.

[0493] The optical excitation source 310 may be a laser or a light emitting diode, for example, which emits light in the green (light having a wavelength such that the color is green), for example. The optical excitation source 310 induces fluorescence in the red, which corresponds to an electronic transition from the excited state to the ground state. Light from the NV diamond material 320 is directed through the optical filter 350 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 340. The optical excitation source 310, in addition to exciting

fluorescence in the NV diamond material 320, also serves to reset the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired polarization.

[0494] For continuous wave excitation, the optical excitation source 310 continuously pumps the NV centers, and the RF excitation source 330 sweeps across a frequency range that includes the zero splitting (when the ms = ±1 spin states have the same energy) photon energy of approximately 2.87 GHz. The fluorescence for an RF sweep corresponding to a NV diamond material 320 with NV centers aligned along a single direction is shown in FIG. 4A for different magnetic field components Bz along the NV axis, where the energy splitting between the ms = -1 spin state and the ms = +1 spin state increases with Bz. Thus, the component Bz may be determined. Optical excitation schemes other than continuous wave excitation are contemplated, such as excitation schemes involving pulsed optical excitation, and pulsed RF excitation.

Examples of pulsed excitation schemes include Ramsey pulse sequence, and spin echo pulse sequence. [0495] The Ramsey pulse sequence is a pulsed RF-pulsed laser scheme that measures the free precession of the magnetic moment in the NV diamond material 320 with NV centers, and is a technique that quantum mechanically prepares and samples the electron spin state. FIG. 5 is a schematic diagram illustrating the Ramsey pulse sequence. As shown in FIG. 5, a Ramsey pulse sequence includes optical excitation pulses and RF excitation pulses over a five-step period. In a first step, during a period 0, a first optical excitation pulse 510 is applied to the system to optically pump electrons into the ground state (i.e., ms = 0 spin state). This is followed by a first RF excitation pulse 520 (in the form of, for example, a microwave (MW) π/2 pulse) during a period 1. The first RF excitation pulse 520 sets the system into superposition of the ms = 0 and ms = +1 spin states (or, alternatively, the ms = 0 and ms = -1 spin states, depending on the choice of resonance location). During a period 2, the system is allowed to freely precess (and dephase) over a time period referred to as tau (τ). During this free precession time period, the system measures the local magnetic field and serves as a coherent integration. Next, a second RF excitation pulse 540 (in the form of, for example, a MW π/2 pulse) is applied during a period 3 to project the system back to the ms = 0 and ms = +1 basis. Finally, during a period 4, a second optical pulse 530 is applied to optically sample the system and a measurement basis is obtained by detecting the fluorescence intensity of the system. The RF excitation pulses applied are provided at a given RF frequency, which correspond to a given NV center orientation.

[0496] In general, the NV diamond material 320 will have NV centers aligned along directions of four different orientation classes. FIG. 4B illustrates fluorescence as a function of RF frequency for the case where the NV diamond material 320 has NV centers aligned along directions of four different orientation classes. In this case, the component Bz along each of the different orientations may be determined. These results, along with the known orientation of crystallographic planes of a diamond lattice, allow not only the magnitude of the external magnetic field to be determined, but also the direction of the magnetic field.

[0497] FIG. 3B is a schematic diagram illustrating a NV center magnetic sensor system 300B with a waveplate 315. The NV center magnetic sensor system 300B uses fluorescence intensity to distinguish the ms = ±1 states, and to measure the magnetic field based on the energy difference between the ms = +1 state and the ms = -1 state. The system 300B includes an optical excitation source 310, which directs optical excitation through a waveplate 315 to a NV diamond material 320 with defect centers (e.g, NV diamond material). The system further includes an RF excitation source 330, which provides RF radiation to the NV diamond material 320. Light from the NV diamond may be directed through an optical filter 350 to an optical detector 340.

[0498] In some implementations, the RF excitation source 330 may be a microwave coil. The RF excitation source 330, when emitting RF radiation with a photon energy resonant with the transition energy between ground ms = 0 spin state and the ms = +1 spin state, excites a transition between those spin states. For such a resonance, the spin state cycles between ground ms = 0 spin state and the ms = +1 spin state, reducing the population in the ms = 0 spin state and reducing the overall fluorescence at resonances. Similarly, resonance occurs between the ms = 0 spin state and the ms = -1 spin state of the ground state when the photon energy of the RF radiation emitted by the RF excitation source is the difference in energies of the ms = 0 spin state and the ms = -1 spin state, or between the ms = 0 spin state and the ms = +1 spin state, there is a decrease in the fluorescence intensity.

[0499] In some implementations, the optical excitation source 310 may be a laser or a light emitting diode which emits light in the green. In some implementations, the optical excitation source 310 induces fluorescence in the red, which corresponds to an electronic transition from the excited state to the ground state. In some implementations, the light from the optical excitation source 310 is directed through a waveplate 315. In some implementations, light from the NV diamond material 320 is directed through the optical filter 350 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 340. The optical excitation source 310, in addition to exciting fluorescence in the NV diamond material 320, also serves to reset the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired

polarization.

[0500] In some implementations, the light is directed through a waveplate 315. In some implementations, the waveplate 315 may be in a shape analogous to a cylinder solid with an axis, height, and a base. In some implementations, the performance of the system is affected by the polarization of the light (e.g., light from a laser) as it is lined up with a crystal structure of the NV diamond material 320. In some implementations, a waveplate 315 may be mounted to allow for rotation of the waveplate 315 with the ability to stop and/or lock the waveplate 315 in to position at a specific rotation orientation. This allows the tuning of the polarization relative to the NV diamond material 320. Affecting the polarization of the system allows for the affecting the responsive Lorentzian curves. In some implementations where the waveplate 315 is a half-wave plate such that, when a laser polarization is lined up with the orientation of a given lattice of the NV diamond material 320, the contrast of the dimming Lorentzian, the portion of the light sensitive to magnetic fields, is deepest and narrowest so that the slope of each side of the Lorentzian is steepest. In some implementations where the waveplate 315 is a half-wave plate, a laser polarization lined up with the orientation of a given lattice of the NV diamond material 320 allows extraction of maximum sensitivity for the measurement of an external magnetic field component aligned with the given lattice. In some implementations, four positions of the waveplate 315 are determined to maximize the sensitivity to different lattices of the NV diamond material 320. In some implementations, a position of the waveplate 315 is determined to get similar sensitivities or contrasts to the four Lorentzians corresponding to lattices of the NV diamond material 320.

[0501] In some implementations where the waveplate 315 is a half-wave plate, a position of the waveplate 315 is determined as an initial calibration for a light directed through a waveplate 315. In some implementations, the performance of the system is affected by the polarization of the light (e.g., light from a laser) as it is lined up with a crystal structure of the NV diamond material 320. In some implementations, a waveplate 315 is mounted to allow for rotation of the waveplate 315 with the ability to stop and/or lock the half-wave after an initial calibration determines the eight Lorentzians associated with a given lattice with each pair of Lorentzians associated with a given lattice plane symmetric around the carrier frequency. In some implementations, the initial calibration is set to allow for high contrast with steep Lorentzians for a particular lattice plane. In some implementations, the initial calibration is set to create similar contrast and steepness of the Lorentzians for each of the four lattice planes. The structural details of the waveplate 315 will be discussed in further detail below

[0502] While FIGS. 3A-3B illustrate an NV center magnetic sensor system 300 A, 300B with NV diamond material 320 with a plurality of NV centers, in general, the magnetic sensor system may instead employ a different magneto-optical defect center material, with a plurality of magneto-optical defect centers. The electronic spin state energies of the magneto-optical defect centers shift with magnetic field, and the optical response, such as fluorescence, for the different spin states is not the same for all of the different spin states. In this way, the magnetic field may be determined based on optical excitation, and possibly RF excitation, in a corresponding way to that described above with NV diamond material. Magneto-optical defect center materials include but are not limited to diamonds, Silicon Carbide (SiC) and other materials with nitrogen, boron, or other chemical defect centers. Our references to diamond-nitrogen vacancies and diamonds are applicable to magneto-optical defect center materials and variations thereof.

[0503] FIG. 6A illustrates a magnetic field detection system 600A according to some embodiments. The system 600A includes an optical light source 610 (i.e., the optical light source 310 of FIGS. 3A and 3B), which directs optical light to an NV diamond material 620 (i.e., the NV diamond material 320 of FIGS. 3 A and 3B) with NV centers, or another magneto-optical defect center material with magneto-optical defect centers. An RF excitation source 630 (i.e., the RF excitation source 330 of FIGS. 3A and 3B) provides RF radiation to the NV diamond material 620. The system 600A may include a magnetic field generator 670 which generates a magnetic field, which may be detected at the NV diamond material 620, or the magnetic field generator 670 may be external to the system 600A. The magnetic field generator 670 may provide a biasing magnetic field.

[0504] FIG. 6B is another schematic diagram of a magnetic field detection system 600B according to some embodiments. The system 600B includes an optical excitation source 610 (i.e., the optical excitation source 310 of FIGS. 3 A and 3B), which directs optical excitation to a NV diamond material 620 (i.e., the NV diamond material 320 of FIGS. 3A and 3B) with defect centers. An RF excitation source 630 (i.e., the RF excitation source 330 of FIGS. 3A and 3B) provides RF radiation to the NV diamond material 620. A magnetic field generator 670 generates a magnetic field, which is detected at the NV diamond material 620.

[0505] Referring to both FIGS. 6A and 6B, the system 600A, 600B further includes a controller 680 arranged to receive a light detection signal from the optical detector 640 (i.e., the optical detector 340 of FIGS. 3A and 3B) and to control the optical light source 610, the RF excitation source 630, and the magnetic field generator 670. The controller 680 may be a single controller, or multiple controllers. For a controller 680 including multiple controllers, each of the controllers may perform different functions, such as controlling different components of the system 600 A, 600B. The magnetic field generator 670 may be controlled by the controller 680 via an amplifier 660, for example.

[0506] The RF excitation source 630 may be controlled to emit RF radiation with a photon energy resonant with the transition energy between the ground ms = 0 spin state and the ms = ±1 spin states as discussed above with respect to FIGS. 3 A or 3B, or to emit RF radiation at other nonresonant photon energies.

[0507] The controller 680 is arranged to receive a light detection signal from the optical detector 640 and to control the optical light source 610, the RF excitation source 630, and the magnetic field generator 670. The controller 680 may include a processor 682 and a memory 684, in order to control the operation of the optical light source 610, the RF excitation source 630, and the magnetic field generator 670. The memory 684, which may include a nontransitory computer readable medium, may store instructions to allow the operation of the optical light source 610, the RF excitation source 630, and the magnetic field generator 670 to be controlled. That is, the controller 680 may be programmed to provide control.

[0508] The magnetic field generator 670 may generate magnetic fields with orthogonal polarizations, for example. In this regard, the magnetic field generator 670 may include two or more magnetic field generators, such as two or more Helmholtz coils. The two or more magnetic field generators may be configured to provide a magnetic field having a predetermined direction, each of which provide a relatively uniform magnetic field at the NV diamond material 620. The predetermined directions may be orthogonal to one another. In addition, the two or more magnetic field generators of the magnetic field generator 670 may be disposed at the same position, or may be separated from each other. In the case that the two or more magnetic field generators are separated from each other, the two or more magnetic field generators may be arranged in an array, such as a one-dimensional or two-dimensional array, for example.

[0509] The system 600A may be arranged to include one or more optical detection systems 605, where each of the optical detection systems 605 includes the optical detector 640, optical excitation source 610, and NV diamond material 620. Similarly, the system 600B also includes the optical detector 640, optical excitation source 610, and NV diamond material 620. The magnetic field generator 670 may have a relatively high power as compared to the optical detection systems 605. In this way, the optical systems 605 may be deployed in an environment that requires a relatively lower power for the optical systems 605, while the magnetic field generator 670 may be deployed in an environment that has a relatively high power available for the magnetic field generator 670 so as to apply a relatively strong magnetic field.

[0510] The RF excitation source 630 may be a microwave coil, for example behind the light of the optical excitation source 610. The RF excitation source 630 is controlled to emit RF radiation with a photon energy resonant with the transition energy between the ground ms = 0 spin state and the ms = ±1 spin states as discussed above with respect to FIGS. 3A and 3B.

[0511] The optical excitation source 610 may be a laser or a light emitting diode, for example, which emits light in the green, for example. The optical excitation source 610 induces fluorescence in the red from the NV diamond material 620, where the fluorescence corresponds to an electronic transition from the excited state to the ground state. Light from the NV diamond material 620 is directed through the optical filter 650 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 640. The optical excitation light source 610, in addition to exciting fluorescence in the NV diamond material 620, also serves to reset the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired polarization.

[0512] The controller 680 is arranged to receive a light detection signal from the optical detector 640 and to control the optical excitation source 610, the RF excitation source 630, and a second magnetic field generator (not illustrated). The controller may include a processor 682 and a memory 684, in order to control the operation of the optical excitation source 610, the RF excitation source 630, and the second magnetic field generator. The memory 684, which may include a nontransitory computer readable medium, may store instructions to allow the operation of the optical excitation source 610, the RF excitation source 630, and the second magnetic field generator to be controlled. That is, the controller 680 may be programmed to provide control.

[0513] FIG. 6C is a schematic of an NV center magnetic sensor system 600C, according to an embodiment. The sensor system 600C includes an optical excitation source 610, which directs optical excitation to an NV diamond material 620 with NV centers, or another magneto-optical defect center material with magneto-optical defect centers. An RF excitation source 630 provides RF radiation to the NV diamond material 620. The NV center magnetic sensor system 600C may include a bias magnet (bias magnetic field generator 670) applying a bias magnetic field to the NV diamond material 620. Unlike FIGS. 6A and 6B, the sensor system 600C of FIG. 6C does not include the amplifier 660. However, in some implementations of the NV center magnetic sensor system 600C, an amplifier 660 may be utilized. Light from the NV diamond material 620 may be directed through an optical filter 650 and optionally, an electromagnetic interference (EMI) filter (not illustrated), which suppresses conducted interference, to an optical detector 640. The sensor system 600C further includes a controller 680 arranged to receive a light detection signal from the optical detector 640 and to control the optical excitation source 610 and the RF excitation source 630.

[0514] The optical excitation source 610 may be a laser or a light emitting diode, for example, which emits light in the green, for example. The optical excitation source 610 induces fluorescence in the red, which corresponds to an electronic transition from the excited state to the ground state. Light from the NV diamond material 620 is directed through the optical filter 650 to filter out light in the excitation band (in the green for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 640. In implementations including the EMI filter, the EMI filter is arranged between the optical filter 650 and the optical detector 640 and suppresses conducted interference. The optical excitation light source 610, in addition to exciting fluorescence in the NV diamond material 620, also serves to reset the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired polarization.

MAGNETIC DETECTION SYSTEMS

Example Magneto-Optical Defect Center System

[0515] As shown in FIG. 7, the magneto-optical defect center magnetometer 700 has several components mounted between top plate 710, the bottom plate 720, and the PCB 722. The components of the magneto-optical defect center magnetometer 700 include a green laser diode 711, laser diode circuitry 712, a magneto-optical defect center element, such as diamond having nitrogen vacancies (DNV), RF amplifier circuitry 714, an RF element 716, one or more photo diodes 718, and photo diode circuitry 770. In operation ,the green laser diode 711 emits green wavelength light toward the magneto-optical defect center element based on a control signal from the laser diode circuitry 712. The RF amplifier circuitry 714 receives an RF input signal via an RF connector 715. In some implementations, the RF signal is generated by a separate controller, such as an external RF wave form generator circuit. In other implementations, the RF waveform generator may be included with the magneto-optical defect center magnetometer 700. The RF amplifier circuitry 714 uses the RF input signal to control the RF element 716. The RF element 716 may include a microwave coil or coils. The RF element 716 emits RF radiation to control the spin of the magneto-optical defect centers of the magneto-optical defect center element to be aligned along a single direction, such as prior to a measurement by the magneto- optical defect center magnetometer 700. The magneto-optical defect center element, when excited by the green laser light, emits red wavelength based on external magnet fields and the emitted red light is detected by the one or more photo diodes 718. The detected red light by the photo diodes 718 may be processed by the photo diode circuitry 720 and/or may be outputted to an external circuit for processing. Based on the detected red light, the magneto-optical defect center magnetometer 700 can detect the directionality and intensity (e.g., vector) of the external magnetic field. Such a vector magnetometer may be used to detect other objects that generate magnetic fields. Power for the components and/or circuits of the magneto-optical defect center magnetometer 700 and data transmission to and/or from the magneto-optical defect center magnetometer 700 may be provided via a digital signal and power connector 724.

[0516] In some implementations, the magneto-optical defect center magnetometer 700 may include several other components to be mounted via the top plate 710, bottom plate 720, and PCB 722. Such components may include one or more focusing lenses 726, a flash laser 728 and/or flash laser focusing lenses, flash bulb driver circuitry 730, a mirror and/or filtering element 732, and/or one or more light pipes 734. The focusing lenses 726 may focus the emitted green wavelength light from the green laser diode 711 towards the magneto-optical defect center element. The flash laser 728 and/or flash laser focusing lenses may provide additional excitation green wavelength light to the magneto-optical defect center element, and the flash bulb driver circuitry 730 may control the operation of the flash laser 728. The mirror and/or filtering element 732 may be an element that is reflective for red wavelength light, but permits green wavelength light to pass through. In some implementations, the mirror and/or filtering element 732 may be applied to the magneto-optical defect center element, such as a coating, to reflect red wavelength light towards the photo diodes 718. In other implementations, the mirror and/or filtering element 732 may be a separate component that substantially surrounds or encases the magneto-optical defect center element. The one or more light pipes 734 transports red wavelength light emitted from the magneto-optical defect center element to the one or more photo diodes 718 such that the one or more photo diodes 718 may be positioned remote from the magneto-optical defect center element. Additional description may include the applications incorporated by reference.

[0517] As shown in FIG. 7, the components of the magneto-optical defect center magnetometer 700 are mounted to a single PCB 722 such that a compact magneto-optical defect center magnetometer 700 is constructed. In some current magneto-optical defect center magnetometry systems, separate components are assembled on to large stainless steel plates in laboratories for individual experimentation. Such configurations are large, cumbersome, and heavy, which limits the useful applications. Indeed, for certain configurations of magneto-optical defect center magnetometry systems with resolutions of approximately 300 picoteslas, the size of the system may be a meter or more in one or more directions. In contrast to such magneto-optical defect center magnetometry systems, the magneto-optical defect center magnetometer 700 of FIGS. 7- 12 may have a weight of less than 0.5 kilograms, a power range of 1-5 watts, and a size of approximately 7.62 centimeters in the x-direction by 10.16 centimeters in the y-direction by 1.905 centimeters in the z-direction. The magneto-optical defect center magnetometer 700 may have a resolution of approximately 300 picoteslas, a bandwidth of 1 MHz, .and a measurement range of 1000 microteslas. Such a compact magneto-optical defect center magnetometer 700 expands the range of potential applications for vector magneto-optical defect center

magnetometry by providing a small weight, size and power magneto-optical defect center magnetometer 700. Such applications may include magneto-optical defect center vector magnetometry in aircraft, submersibles, vehicles, satellites, etc.

[0518] In the implementation shown in FIGS. 7-8, the excitation source components of the magneto-optical defect center magnetometer 700, such as the green laser diode 711 and one or more focusing lenses 726 are aligned along a first axis 750 and are mounted to the PCB 722. The collection components of the magneto-optical defect center magnetometer 700, such as the one or more photo diodes 718, mirror and/or filtering element 732, and/or one or more light pipes 734 are aligned along a second axis 760 and are mounted to the PCB 722. The second axis 760 is in the same plane as the first axis 750 and perpendicular to the first axis 750 such that the z-dimension of the magneto-optical defect center magnetometer 700 may be reduced to a minimum that is based on the z-dimensions of the components. Furthermore, by providing the excitation source components of the magneto-optical defect center magnetometer 700 along the first axis 750 perpendicular to the collection components of the magneto-optical defect center magnetometer 700 along the second axis 760, interference (e.g., magnetic, electrical, etc.) between the components may be reduced.

[0519] As shown in FIG. 7, the corresponding circuitry (e.g., the laser diode circuitry 712, RF amplifier circuitry 714, photo diode circuitry 720, etc.) for each component of the excitation and collection components are also mounted to the single PCB 722. Thus, electrical contact etchings on the PCB 722 can be used electrically couples the corresponding circuitry to each corresponding component, thereby eliminating any unnecessary connections and/or wiring between components. Furthermore, the corresponding circuitry is positioned on the PCB 722 near each corresponding component in open portions of the PCB 722 where the optical components of the excitation source components and/or collection components are not located. Such positioning reduces the x- and y-dimensional size of the magneto-optical defect center magnetometer while also reducing the length of any electrical contact etchings to electrically couple the corresponding circuitry to a corresponding component.

[0520] Referring generally to FIGS. 7-12, the components of the magneto-optical defect center magnetometer 700 also include a planar arrangement to reduce a z-direction size of the magneto- optical defect center magnetometer 700. The reduced z-direction size may be useful for positioning the magneto-optical defect center magnetometer 700 in a vehicle or other device to control for any vibratory influences and/or space constraints. Moreover, in some

implementations, the size and/or weight of the magneto-optical defect center magnetometer 700 may be important. For instance, in aircraft, size and weight may be tightly controlled, so a small z-directional size may permit the magneto-optical defect center magnetometer to be positioned on a bulkhead and/or within a cockpit with minimal space impact. Moreover, the high stiffness and low mass of the top plate 710 and bottom plate 720 limit the weight of the magneto-optical defect center magnetometer 700.

[0521] The planar arrangement of the components of the magneto-optical defect center magnetometer 700 may also be useful. The planar arrangement allows for the excitation source, such as the green laser diode 711, and the collection device, such as the one or more photo diodes 718, to be positioned anywhere in the plane, thereby permitting varying configurations for the magneto-optical defect center magnetometer 700 to accommodate space constraints. Further still, the planar configuration also permits multiple excitation sources and/or collection devices to be utilized by the magneto-optical defect center magnetometer 700. As shown in FIGS. 7-12, a primary green laser diode 711 and a flash laser 728 can be used as excitation sources, while two light pipes 734 and photo diodes 718 are utilized for collection devices. Of course additional excitation sources and/or collection devices may be used as well. The planar arrangement of the components of the magneto-optical defect center magnetometer 700 is also beneficial for the mounting of optical components, such as the laser diodes, focusing lenses, light pipes, etc. on the PCB 722 because the planar arrangement limits any z-direction variability such that alignment using the pins and alignment openings positions the optical components in a known position relative to the other components of the magneto-optical defect center magnetometer 700. Further still, the planar arrangement of the components of the magneto-optical defect center

magnetometer 700 provides a controlled reference plane for determining the vector of the detected external magnetic field. Still further, the planar arrangement permits usage of the mirror and/or filtering element 732 that can be configured to confine any and/or substantially all of the emitted red light from the magneto-optical defect center element to within a small z-direction area to be directed toward the one or more photo diodes 718. That is, the mirror and/or filtering element 732 can be configured to direct any emitted red wavelength light from the magneto- optical defect center element to within the plane defined by the planar arrangement.

[0522] By providing a magneto-optical defect center magnetometer 700 with the excitation source components and collection device components mounted to a single PCB 722, a small form factor magneto-optical defect center vector magnetometer may be provided for a range of applications.

[0523] In some implementations, the RF element 716 may be constructed in accordance with the teachings of U.S. Provisional Patent Application No. 62/343,492, filed May 31, 2016, entitled "LAYERED RF COIL FOR MAGNETOMETER", attorney docket no. 111423-0119, and U.S. Non-Provisional Patent Application No. 15/380,691, filed December 15, 2016, entitled "LAYERED RF COIL FOR MAGNETOMETER," the entire contents of which are incorporated by reference herein in their entirety. In some implementations, the one or more light pipes 734 may be constructed in accordance with the teachings of U.S. Provisional Patent Application No. 62/343,746, filed May 31, 2016, entitled "DNV DEVICE INCLUDING LIGHT PIPE WITH OPTICAL COATINGS", attorney docket no. 111423-1138, U.S. Provisional Patent Application No. 62/343,750, filed May 31, 2016, entitled "DNV DEVICE INCLUDING LIGHT PIPE", attorney docket no. 111423-1139, the entire contents of each are incorporated by reference herein in their entirety. In some implementations, the mirror and/or filtering element 732 may be constructed in accordance with the teachings of U.S. Provisional Patent Application No.

62/343,758, filed May 31, 2016, entitled "OPTICAL FILTRATION SYSTEM FOR DIAMOND MATERIAL WITH NITROGEN VACANCY CENTERS", attorney docket no. 111423-1140, the entire contents of each are incorporated by reference herein in its entirety. In some implementations, the magneto-optical defect center magnetometer 700 may be constructed in accordance with the teachings of U.S. Provisional Patent Application No. 62/343,818, filed May 31, 2016, entitled "DIAMOND NITROGEN VACANCY MAGNETOMETER INTEGRATED STRUCTURE", attorney docket no. 111423-1141, U.S. Provisional Patent Application No. 62/343,600, filed May 31, 2016, entitled "TWO-STAGE OPTICAL DNV EXCITATION", attorney docket no. 111423-1142, U.S. Non-Provisional Patent Application No. 15/382,045, filed December 16, 2016, entitled "TWO-STAGE OPTICAL DNV EXCITATION," U.S. Provisional Patent Application No. 62/343,602, filed May 31, 2016, entitled "SELECTED VOLUME CONTINUOUS ILLUMINATION MAGNETOMETER", attorney docket no. 111423-1143, the entire contents of each are incorporated by reference herein in their entirety.

[0524] FIG. 13 illustrates the RF element 716 with an arrangement of coils 1710 and an NV diamond material 1200. The RF element 716 includes a plurality of coils 1710a, 1710b, 1710c, 1710d and 1710e which may be arranged around the NV diamond material 1200, where the coils 1710 are in a layered arrangement one above the other. While the number of coils shown in FIG. 13 is five, the number may be more or less than five. The coils 1710 may be formed in a substrate 1720. The coils 1710 may be connected to an RF feed connector 1730 to allow power to be provided to the coils. The coils 1710 may be connected in parallel to the RF feed connector 1730.

[0525] While FIG. 13 illustrates the coils 1710 to be arranged around the NV diamond material 1200, the NV diamond material 1200 may have other arrangements relative to the coils 1710. For example, the NV diamond material 1200 may be arranged above or below the coils 1710. The NV diamond material 1200 may be arranged normal to the coils 1710, or at some other angle relative to the coils 1710.

[0526] The substrate 1720 may be a printed circuit board (PCB), for example, and the coils 1710 may be layered in the PCB and separated from each other by dielectric material. The coils 1710 may be formed of a conducting material such as a metal, such as copper, for example.

[0527] FIG. 14A is a side view of the coils 1710 and the RF connector 1730. The coils 1710 are spaced from each other in the layered arrangement, and may be spaced by a uniform spacing. The coils may have any shape, such as square or spiral. Preferably, the coils may have a spiral shape, as shown in FIG. 13 and in FIG. 14B, which is a top view of the coils 1710 and the RF connector 1730. In FIG. 14B, only the top coil 1710a can be seen, because the coils 1710b, 1710c, 1710d and 1710e are below the top coil 1710b.

[0528] The uniform spacing of the coils 1710 and uniform spacing between the spiral shape coils allow the RF element 716 to provide a uniform RF field in the NV diamond material 1200 over the frequency range needed for magnetic measurement of the NV diamond material 1200, which may enclosed by the coils 1710. This arrangement provides both uniformity in phase and gain of the RF signal throughout the needed frequency range, and throughout the different regions of the NV diamond material 1200. Further, the layered coils may be operated in a pulsed manner and in this arrangement in order to avoid unnecessary overlap interference. The interference is reduced in pulsed operation of the coils 1710.

[0529] FIGS, 15 A, 15B and 15C illustrate the magnetic field H generated by the RF excitation source 716 in a plane parallel to the plane of the coils 1710 in the region of the NV diamond material 1200 at frequencies of 2GHz, 3GHz and 4GHz, respectively. The arrangement is for a five layer coil with spiral shaped coils. FIG. 16 is a table illustrating the electric field E and magnetic field H generated by the RF element 716 in the region of the NV diamond material 1200 at frequencies from 2.0 to 4.0 GHz for the five layer coil arrangement with spiral shaped coils. Thus, FIGS. 15 A, 15B and 15C illustrate the uniformity of the magnetic field, and FIG. 16 illustrates the uniformity of the electric field E and magnetic field H in the NV diamond material 1200 over the needed frequency range, and throughout the different regions of the NV diamond material 1200.

Optical Waveguide or Light Pipe

[0530] FIG. 17 is a schematic illustrating details of an optical waveguide assembly 1800 that transmits light from the NV diamond material 1200 to an optical detector 640, such as photo diodes 718 of FIG. 8, in some embodiments. The optical waveguide assembly 1800 may include an optical waveguide 1810 and an optical filter 1850 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 640.

[0531] The optical waveguide 734 may be any appropriate optical waveguide. In some embodiments, the optical waveguide is a light pipe. The light pipe may have any appropriate geometry. In some embodiments, the light pipe may have a circular cross-section, square cross- section, rectangular cross-section, hexagonal cross-section, or octagonal cross-section. A hexagonal cross-section may be preferred, as a light pipe with a hexagonal cross-section exhibits less light loss than a light pipe with a square cross-section and is capable of being mounted with less contact area than a light pipe with a circular cross-section.

[0532] The light pipe 1810 may be formed from any appropriate material. In some

embodiments, the light pipe may be formed from a borosilicate glass material. The light pipe may be formed of a material capable of transmitting light in the wavelength range of about 350 nm to about 2,200 nm. In some embodiments, the light pipe may be a commercially available light pipe.

[0533] The optical filter 1850 may be any appropriate optical filter capable of transmitting red light and reflecting other light, such as green light. In some embodiments, the optical filter 1850 may be a coating applied to an end surface of the light pipe 1810. The coating may be any appropriate anti-reflection coating for red light. In some embodiments, the anti-reflective coating may exhibit greater than 99% transmittance for light in the wavelength range of about 650 nm to about 850 nm. Preferably, the anti -reflective coating may exhibit greater than 99.9%

transmittance for light in the wavelength range of about 650 nm to about 850 nm. The optical filter 1850 may be disposed on an end surface of the light pipe 1810 adjacent to the optical detector 640.

[0534] In some embodiments, the optical filter 1850 may also be highly reflective for light other than red light, such as green light. Such an optical filter may be a dichroic coating or multiple coatings with the desired cumulative optical properties. The optical filter may exhibit less than about 0.1% transmittance for light with a wavelength of less than about 600 nm.

Preferably, the optical filter may exhibit less than about 0.01% transmittance for light with a wavelength of less than about 600 nm. FIG. 20 is a schematic illustrating the behavior of an optical filter 1900 with respect to green light 1910 and red light 1920 according to some embodiments. The optical filter 1900 can be anti -reflective for the red light 1920, resulting in at least some of the red light 1912 transmitted through the optical filter 1900. The optical filter 1900 can be highly reflective for the green light 1910, resulting in green light 1922 being reflected by the optical filter 1900 and at least most of the green light 1922 not transmitted therethrough.

[0535] The optical filter 1850 may be a coating formed by any appropriate method. In some embodiments, the optical filter 1850 may be formed by an ion beam sputtering (IBS) process. The coating may be a single-layer coating or a multi-layer coating. The coating may include any appropriate material, such as magnesium fluoride, silica, hafnia, or tantalum pentoxide. The material for the coating may be selected based on the light pipe material and the material which the coating will be in contact with, such as an optical coupling material, to produce the desired optical properties. The coating may have a hardness that approximately matches the hardness of the light pipe. The coating may have a high density, and exhibit good stability with respect to humidity and temperature.

[0536] The optical waveguide assembly 1800 may optionally include a second optical filter 1852. The second optical filter 1852 may be a coating disposed on an end surface of the light pipe 1810 adjacent to the diamond material 1200. The second optical filter 1852 may be any of the coatings described above with respect to the optical filter 1850. The inclusion of a second optical filter 1852 may improve the performance of the optical waveguide assembly by about 10%, in comparison to an optical waveguide assembly with a single optical filter.

[0537] As shown in FIG. 17, the optical waveguide assembly 1800 may include an optical coupling material 1834 disposed between the light pipe 1810 or second optical filter 1852 and the diamond material 1200. An optical coupling material 1832 may also be disposed between the light pipe 1810 or optical filter 1850 and the optical detector 640. The optical coupling material may be any appropriate optical coupling material, such as a gel or epoxy. In some embodiments, the optical coupling material may be selected to have optical properties, such as an index of refraction, that improves the light transmission between the coupled components. The coupling material may be in the form of a layer formed between the components to be coupled. In some embodiments, the coupling material layer may have a thickness of about 1 microns to about 5 microns. The coupling material may serve to eliminate air gaps between the components to be coupled, increasing the light transmission efficiency. As shown in FIG. 17, the coupling materials 1832 and 1834 may also account for size mismatches between the components to be coupled. The coupling material may be selected such that an efficiency of the optical waveguide assembly is increased by about 10%. The coupling material may produce a light transmission between the components to be coupled that is functionally equivalent to direct contact between the components to be coupled. In some embodiments, an epoxy coupling material may also serve to mount the diamond material to the optical waveguide assembly, such that other supports for the diamond material are not required. In some embodiments, a coupling material may not be necessary where direct contact between the optical filter or light pipe and the optical detector is achieved. Similarly, a coupling material may not be necessary where direct contact between the light pipe or second optical filter and the diamond material is achieved.

[0538] FIG. 18 shows a light pipe 1810 with a hexagonal cross-section and the interaction with a mount 1820 securing the light pipe 1810 within the device in some embodiments. The light pipe 1810 may be mounted such that only the vertices 1812 of the light pipe 1810 contact the mount 1820. Such an arrangement allows the light pipe to be securely and rigidly supported by the mount 1820, while also reducing the contact area between the mount 1820 and the surface of the light pipe 1810. Contact between the light pipe and the mount may result in a reduction in the efficiency of the optical waveguide assembly 1800. As shown in FIG. 18, a mount 1820 with a circular support opening may be successfully employed to support a light pipe 1810 with a hexagonal cross-section.

[0539] FIG. 19 shows a top down schematic of an arrangement of optical waveguide assemblies according to some embodiments. The optical filters and optical coupling materials are not shown in FIG. 19 for the sake of clarity. As shown in FIG. 19, more than one optical waveguide assembly may be included in the magnetic sensor system, such as two or more optical waveguide assemblies. The inclusion of more than one optical waveguide assemblies allows more than one optical detector 640 to be included in the magnetic sensor device, increasing the amount of light collected and measured by the optical detectors 640. The inclusion of additional optical detectors 640 also increases the amount of noise in the system, which may negatively impact the sensitivity or accuracy of the system. The use of two optical waveguide assemblies may provide a compromise between increased light collection and increased noise. Each optical waveguide assembly in the magnetic sensor system may be associated with a different optical detector, but the same diamond material.

[0540] The light pipe 1810 may be mounted to the magnetic sensor system by at least one mount 1820. In some embodiments, two mounts 1820 may support each light pipe 1810 in the magnetic sensor system. The light pipe may be mounted to the device rigidly, such that the alignment of the light pipe 1810, the optical detector 640, and the diamond material 1200 is maintained during operation of the system. The mounting of the light pipe to the magnetic sensor system may be sufficiently rigid to prevent a mechanical response of the light pipe in the region that would affect the measurement of light by the optical detector. [0541] The light pipe can be selected to have an appropriate aperture size. The aperture of the light pipe can be selected to be matched to or smaller than the optical detector. This size relationship allows the optical detector to capture the highest possible percentage of the light emitted by the light pipe. The aperture of the light pipe can be also selected to be larger than the surface of the diamond material to which it is coupled. This size relationship allows the light pipe to capture the highest possible percentage of light emitted by the diamond material. In some embodiments, the light pipe may have an aperture of about 4 mm. In some other embodiments, the light pipe may have an aperture of about 2 mm. In some embodiments, the light pipe may have an aperture of 4 mm, and the diamond material may have a coupled surface with a height of 0.6 mm and a length of 2 mm, or less. The light pipe may have any appropriate length, such as about 25 mm.

[0542] As shown in FIG. 19, the light pipe can be positioned such that the end surface of the light pipe adjacent the diamond material is parallel, or substantially parallel, to the associated surface of the diamond material. This arrangement allows the light pipe to capture an increased amount of the light emitted by the diamond material. The alignment of the surfaces of the light pipe and the diamond material ensures that a maximum amount of the light emitted by the diamond material will intersect the end surface of the light pipe, thereby being captured by the light pipe.

Optical Filtration System

[0543] With reference to FIG. 21, some embodiments of an optical filtration system 2100 is illustrated. In these embodiments, the optical filtration system 2100 includes an optical excitation source 2110, a vacancy material 2105 with vacancy centers, a RF excitation source 2120, optical guide 2130, and an optical filter 2150.

[0544] The optical filter 2150 is configured to provide at least a second portion of light corresponding to a second wavelength W2 to a plurality of optical collectors 2130 as described herein.

[0545] The optical excitation source 2110 may be a laser or a light emitting diode. The optical excitation source may be configured to generate light corresponding to a first wavelength Wl . For example, the optical excitation source 2110 may emit light corresponding to green.

[0546] The vacancy material 2105 may be configured to receive optical excitation based, at least in part, on the generation of light corresponding to a first wavelength Wl . In some further embodiments, the NV diamond material 2105 may be configured to receive radio frequency (RF) excitation provided via the RF excitation source as described herein above.

[0547] In turn, the vacancy material 2105 may be configured to generate light corresponding to a second wavelength W2 (e.g., a wavelength corresponding to red) responsive to the RF excitation and the optical excitation received. In this regard, the optical excitation source 2110 induces fluorescence by the vacancy material 2105 corresponding to the second wavelength W2. The inducement of fluorescence causes an electronic transition from the excited state to the ground state. The optical excitation source 2110, in addition to exciting fluorescence in the NV diamond material 2105, also serves to reset the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired polarization.

[0548] The optical filtration system 2100 includes a plurality of optical collectors 2130 configured to receive at least a first portion of light corresponding to the second wavelength W2. The optical collectors may take the form of light pipes, light tubes, lenses, optical fibers, optical waveguides, etc. For example, as the vacancy material 2105 generates light corresponding to the second wavelength W2 (e.g., red light), a first portion of the light corresponding to the second wavelength W2 may enter or is otherwise received by the optical collectors 2130. The light corresponding to the wavelength W2 may be received by the receiving ends 2132 of each respective optical collector 2130. In some embodiments, the receiving ends 2132 may be disposed proximate to (e.g., adjacent to or otherwise near) the vacancy material 2105. Although a plurality of optical collectors 2130 is depicted, in some embodiments, one optical collector 2130 (as depicted in FIG. 22) may be configured to receive at least a first portion of light corresponding to the second wavelength W2.

[0549] As illustrated in FIG. 21, the NV diamond material 2105 is disposed between the receiving ends 2132 such that the optical collectors 2130 are configured to form a gap G. A second portion of the light corresponding to the wavelength W2 may be directed beyond the gap G and/or the optical collectors 2130. For example, the light directed beyond the gap G may not enter or otherwise be received by the optical collectors 2130. The gap G may include an adhesive material such as a gel or an epoxy. Although a gap G is depicted, the gap G may be filled or otherwise inexistent such that the NV diamond material 2105 may generate light without the gap G as described herein. [0550] The optical filtration system 2100 further includes the optical filter 2150. The optical filter 2150 is configured to provide at least a second portion of light corresponding to the second wavelength W2 to the plurality of optical collectors 2130. As used herein, the term "optical filter" may be used to refer to a filter configured to transmit (e.g. pass) light corresponding to one or more predetermined wavelengths (e.g., a first wavelength corresponding to green) while reflecting light corresponding to other predetermined wavelengths (e.g., a second wavelength corresponding to red). In some embodiments, the optical filter 2150 may take the form of a dichroic filter, interference filter, thin-film filter, dichroic mirror, dichroic reflector, or a combination thereof. The optical filter 2150 (e.g., a dichroic filter) may be configured to reflect light corresponding to the second wavelength W2 (e.g., light in the red fluorescence band) from the vacancy material 2105 which, in turn, is received by the optical collectors 2130. For example, the optical filter 2150 may reflect the light directed beyond the gap G to the optical collectors 2130 that would otherwise not enter or be received by the optical collectors 2130.

[0551] Alternatively or additionally, light corresponding to the first wavelength Wl from the vacancy material 2105 may be directed through the optical filter 2150 to filter out the light corresponding to the first wavelength Wl (e.g., in the green fluorescence band). Although a single optical filter 2150 is depicted, in some embodiments, a plurality of optical filters 2150 (as depicted in FIG. 22) may be configured to provide at least a second portion of light

corresponding to a second wavelength W2 to one or more optical collectors 2130.

[0552] In some embodiments, the optical filter 2150 includes an optical coating (e.g., an anti- reflection coating, high reflective coating, filter coating, beamsplitter coating, etc.) configured to facilitate transmission of light corresponding to the first wavelength Wl (e.g., light

corresponding to green) through the optical filter 2150. The optical coating may include at least one of a soft coating (e.g., one or more layers of thin film) or a hard coating. The optical coating may be made of a material such as zinc sulfide, cryolyte, silver, and/or any other like suitable material, or a combination thereof.

[0553] The optical coating (e.g., the anti-reflective coating) is further configured to facilitate the provision of the light corresponding to the second wavelength W2 to the optical collectors 2130. For example, the optical coating facilitates the reflection of the light corresponding to the second wavelength W2 from the vacancy material 2105 to the optical collectors 2130. [0554] As illustrated in FIG. 23, the optical coating may include a substrate S and one or more layers Ln configured to at least one of transmit or reflect light according to at least one refractive index which describes how light propagates through the optical filter 2150. In this regard, the phase shift between the light corresponding to the second wavelength W2 reflected, for example, at the first and second points PI, P2 of the layer Ln is 180°. In turn, the reflections Rl, R2 (e.g., the reflected rays) are cancelled responsive to interference such as, but not limited to, destructive interference. Advantageously, the optical coating increases transmission, efficiency by which the light corresponding to the second wavelength W2 is received by the optical collectors 2130 and resists environmental damage to the optical filter 2150.

[0555] With reference back to FIG. 21, the optical filter 2150 may be disposed at least one of above, beneath, behind, or in front of the vacancy material 2105 to receive and, in turn, provide the light corresponding to the second wavelength W2 (e.g., light in the red fluorescence band) to the optical collectors 2130. As illustrated, the optical filter 2150 is disposed behind the NV diamond material 2105 such that the optical filter 2150 reflects light corresponding to the second wavelength W2 from the vacancy material 2105. In some embodiments, the optical filter 2150 may be configured to enclose or otherwise surround the vacancy material 2105. The enclosing of the vacancy material 2105 increases the reflection of light corresponding to the second wavelength W2 from the vacancy material 2105 to the optical collectors 2130.

[0556] In some embodiments, the optical filter 2150 is disposed proximate to the plurality of optical collectors 2130. The optical filter 2150 may be disposed within a predetermined distance to the optical collectors 2130. For example, the optical filter 2150 may be disposed next to the optical collectors 2130 as depicted. The optical filter 2150 may be disposed at least one of above, beneath, behind, or in front of the plurality of optical collectors 2130. As depicted, the optical filter 2150 is disposed behind the plurality of optical collectors 2130. Advantageously, disposing the optical filter 2150 behind the plurality of optical collectors 2130 facilitates the removal of light corresponding to the first wavelength Wl (e.g., light corresponding to green) by the optical filter 2150 which reduces noise and/or other errors introduced by Wl .

[0557] In further embodiments, a predetermined dimension (e.g., length, width, height, etc.) corresponding to the optical filter 2150 may be configured to extend beyond a predetermined dimension (e.g., length, width, height, etc.) corresponding to the gap G and/or the optical collectors 2130. For example, the width of the optical filter 2150 may be configured to be greater than the width of the gap G to compensate for over tolerances in manufacturing such that the optical filter 2150 covers the gap G. As the light corresponding to the second wavelength W2 makes contact C with or otherwise hits the optical filter 2150, the light W2 is reflected (as illustrated in FIG. 24) from the optical filter 2150 to the optical collectors 2130. The light ray W2 R is reflected at an angle of incidence a and an angle of reflection β as depicted across the normal N. The angle of incidence may equal the angle of reflection. Each respective angle may measure between 0 degrees and 180 degrees based on one or more refractive indices

corresponding to the optical filter 2150. Alternatively or additionally, the height of the optical filter 2150 may be configured to be greater than the height of the optical collectors 2130 to compensate for over tolerances in manufacturing such that the optical filter 2150 receives light (e.g., light corresponding to the second wavelength W2) directed beyond the optical collectors 2130. In turn, the optical filter 2150 reflects or otherwise provides the light corresponding to the second wavelength W2 to the optical collectors 2130.

Magneto-Optical Defect Center Magnetometer Integrated Structure

[0558] Referring generally to FIG. 25, a magneto-optical defect center magnetometer 2500 may be provided that includes a top plate 2510 and a bottom plate 2520. The bottom plate 2520 may include a printed circuit board (PCB) 2522 that is configured to mount the components of the magneto-optical defect center magnetometer 2500 thereto. The top plate 2510 and bottom plate 2520 may be formed of a material with a high stiffness and a low mass, such as stainless steel, titanium, aluminum, carbon fiber, a composite material, etc. The high stiffness of the top plate 2510 and bottom plate 2520 is such that any vibration modes occur outside of the range of frequencies that may negatively affect the magneto-optical defect center magnetometer 2500 sensor performance. The top plate 2510, bottom plate 2520, and PCB 2522 includes alignment holes into which pins for one or more components of the magneto-optical defect center magnetometer 2500 may be inserted to align the one or more components and, when the top plate and bottom plate 2520 are pressed together, the pins lock the components in place to maintain alignment of the one or more components after assembly of the magneto-optical defect center magnetometer 2500.

[0559] As shown in FIG. 26, the magneto-optical defect center magnetometer 2500 has several components mounted between top plate 2510, the bottom plate 2520, and the PCB 2522. The components of the magneto-optical defect center magnetometer 2500 include a green laser diode 2610, laser diode circuitry 2612, a magneto-optical defect center element, such as a diamond having nitrogen vacancies (DNV), RF amplifier circuitry 2614, an RF element 2616, one or more photo diodes 2618, and photo diode circuitry 2620. In operation, the green laser diode 2610 emits green wavelength light toward the magneto-optical defect center element based on a control signal from the laser diode circuitry 2612. The RF amplifier circuitry 2614 receives an RF input signal via an RF connector 2622. In some implementations, the RF signal is generated by a separate controller, such as an external RF wave form generator circuit. In other implementations, the RF waveform generator may be included with the magneto-optical defect center magnetometer 2500. The RF amplifier circuitry 2614 uses the RF input signal to control the RF element 2616. The RF element 2616 may include a microwave coil or coils. The RF element 2616 emits RF radiation to control the spin of the centers of the magneto-optical defect center element to be aligned along a single direction, such as prior to a measurement by the magneto-optical defect center magnetometer 2500 . The magneto-optical defect center element, when excited by the green laser light, emits red wavelength based on external magnet fields and the emitted red light is detected by the one or more photo diodes 2618. The detected red light by the photo diodes 2618 may be processed by the photo diode circuitry 220 and/or may be outputted to an external circuit for processing. Based on the detected red light, the magneto- optical defect center magnetometer 2500 can detect the directionality and intensity (e.g., vector) of the external magnetic field. Such a vector magnetometer may be used to detect other objects that generate or distort magnetic fields. Power for the components and/or circuits of the magneto-optical defect center magnetometer 2500 and data transmission to and/or from the magneto-optical defect center magnetometer 2500 may be provided via a digital signal and power connector 2624.

[0560] In some implementations, the magneto-optical defect center magnetometer 2500 may include several other components to be mounted via the top plate 2510, bottom plate 2520, and PCB 2522. Such components may include one or more focusing lenses 2626, a flash laser 2628 and/or flash laser focusing lenses, excitation driver circuitry 2630, a mirror and/or filtering element 2632, and/or one or more light pipes 2634. The focusing lenses 2626 may focus the emitted green wavelength light from the green laser diode 2610 towards the magneto-optical defect center element. The flash laser 2628 and/or flash laser focusing lenses may provide additional excitation green wavelength light to the magneto-optical defect center element, and the excitation driver circuitry 2630 may control the operation of the flash laser 2628. The mirror and/or filtering element 2632 may be an element that is reflective for red wavelength light, but permits green wavelength light to pass through. In some implementations, the mirror and/or filtering element 2632 may be applied to the magneto-optical defect center element, such as a coating, to reflect red wavelength light towards the photo diodes 2618. In other implementations, the mirror and/or filtering element 2632 may be a separate component that substantially surrounds or encases the magneto-optical defect center element. The one or more light pipes 2634 transports red wavelength light emitted from the magneto-optical defect center element to the one or more photo diodes 2618 such that the one or more photo diodes 2618 may be positioned remote from the magneto-optical defect center element. Additional description may include the applications incorporated by reference.

[0561] As can be seen in FIG. 26, the elements of the magneto-optical defect center magnetometer 2500 need to be aligned such that the emitted green light from the green laser diode 2610 is directed towards the magneto-optical defect center element and the emitted red wavelength light from the magneto-optical defect center element is directed toward the one or more photo diodes 2618 to be detected. Thus, the various elements must be mounted to the magneto-optical defect center magnetometer 2500 in a manner that aligns and holds the elements in position both during assembly and operation. In some implementations, the elements to be aligned include the green laser diode 2610, any focusing lenses 2626, any flash laser 2628, the RF element 2616, any mirror and/or filtering element 2632, any support elements for any light pipes 2634, and the one or more photo diodes 2618. In some implementations, a two-point orientation system may be implemented to align and secure the elements to be mounted for the magneto-optical defect center magnetometer 2500. That is, the components to be aligned and mounted, or a support or mounting element for each component, includes two points to be aligned relative to the top plate 2510 and two points to be aligned relative to the bottom plate 2520 and PCB 2522. When the two points are aligned and secured relative to the top plate 2510, then the component and/or support or mounting element is rotationally and translationally fixed relative to the top plate 2510. Similarly, when the two points are aligned and secured relative to the bottom plate 2520 and PCB 2522, then the component and/or support or mounting element is rotationally and translationally fixed relative to the bottom plate 2520 and PCB 2522. When the component and/or support or mounting element is positioned between the top plate 2510 and the bottom plate 2520 and PCB 2522, then the component and/or support or mounting element is secured such that the component and/or support or mounting element has a fixed orientation and position for the magneto-optical defect center magnetometer 2500. In some implementations, the two-point orientation system can include two separate components, such as two top pins and two bottom pins. In other implementations, the two-point orientation system may include two surfaces of a single component, such as two different surfaces of a single top pin and single bottom pin. In still other implementations, additional alignment and/or securing points may be used, such as three pins and/or surfaces, four pins and/or surfaces, etc.

[0562] In the implementations shown, the top plate 2510, bottom plate 2520, and PCB 2522 are manufactured and/or machined to include one or more alignment openings, such as alignment openings of the top plate 2510 shown in FIG. 31. In some implementations, the alignment openings may be circular, triangular, square, ovular, ellipsoidal, pentagonal, hexagonal, star shaped, etc. Two or more alignment openings may be provided for the two-point orientation system for each component, such as two circular alignment openings. In other implementations, the alignment openings may be asymmetric openings such that a corresponding pin can only be inserted in a particular orientation. For instance, the alignment openings may be semicircular, etc. The asymmetrical alignment openings may provide two surfaces for the two-point orientation system to align and secure each component and/or a support or mounting element for each component.

[0563] Each support or mounting element, such as the supports or mounting elements shown in FIG. 32, for each of the components to be aligned for the magneto-optical defect center magnetometer 2500 may include one or more corresponding pins, such as pin 2692 shown in FIG. 26. In some implementations, the one or more corresponding pins may have an

asymmetrical cross-sectional geometry to provide two surfaces for the two-point orientation system to align the components relative to the top plate 2510, bottom plate 2520, and PCB 2522. In some implementations, each support or mounting element for each component of the DNV magnetometer 2500 may include two top pins and two bottom pins to align each component relative to the top plate 2510, bottom plate 2520, and PCB 2522. The two top pins and two bottom pins may further limit misalignment. In some implementations, the support or mounting elements may be formed of a plastic, aluminum, titanium, stainless steel, carbon fiber, a composite material, etc. In some implementations, the pins of the support or mounting elements may be configured to be press-fit pins such that the pins compress and form an interference fit with the corresponding alignment openings of the top plate 2510, bottom plate 2520, and PCB 2522. In some implementations, the components may be affixed, such as by an adhesive, mechanical attachment, etc., to a corresponding support or mounting element. For instance, as shown in FIG. 32, support or mounting elements for a laser diode and/or focusing lens, photo diode, and light pipe are shown.

[0564] When the magneto-optical defect center magnetometer 2500 is assembled, a bottom pin for each component is inserted through an alignment opening of the PCB 2522 and bottom plate 2520 to initially mount the component. The top plate 2510 may then be aligned with the top pins for each component and the top plate 2510 and bottom plate 2520 are pressed together to secure and maintain alignment of the components of the magneto-optical defect center magnetometer 2500. In some implementations, the pins may be soldered to the top plate 2510 and/or bottom plate 2520 to fix the components in position. In some implementations, standoffs 2530 are provided to mechanically couple the top plate 2510 to the bottom plate 2520 and PCB 2522. The standoffs 2530 may be formed with the bottom plate 2520 and extend through the PCB 2522 and/or may be separate components attached to the bottom plate 2520 and PCB 2522. In the implementation shown, the standoffs 2530 include threading for a screw, bolt, or other attachment component to be inserted through an opening of the top plate 2510 and secured to the standoff 2530. In other implementations, the standoffs 2530 may be welded or otherwise secured to the top plate 2510.

[0565] By providing alignment pins for the various components of the magneto-optical defect center magnetometer 2500, the components can be secured in a preset position during assembly and operation of the magneto-optical defect center magnetometer 2500. Moreover, by providing a high stiffness and low mass material for the top plate 2510 and bottom plate 2520, any low frequency vibrations can be transmitted through the magneto-optical defect center magnetometer 2500 without affecting the higher frequency operations of the magneto-optical defect center magnetometer 2500.

[0566] Referring generally to FIGS. 25-32, the components of the magneto-optical defect center magnetometer 2500 also include a planar arrangement to reduce a z-direction size of the magneto-optical defect center magnetometer 2500. The reduced z-direction size may be useful for positioning the magneto-optical defect center magnetometer 2500 in a vehicle or other device to control for any vibratory influences and/or space constraints. Moreover, in some implementations, the size and/or weight of the magneto-optical defect center magnetometer 2500 may be important. For instance, magneto-optical defect center aircraft, size and weight may be tightly controlled, so a small z-directional size may permit the magneto-optical defect center magnetometer to be positioned on a bulkhead and/or within a cockpit with minimal space impact. Moreover, the high stiffness and low mass of the top plate 2510 and bottom plate 2520 limit the weight of the magneto-optical defect center magnetometer 2500.

[0567] The planar arrangement of the components of the magneto-optical defect center magnetometer 2500 may also be useful. The planar arrangement allows for the excitation source, such as the green laser diode 2610, and the collection device, such as the one or more photo diodes 2618, to be positioned anywhere in the plane, thereby permitting varying configurations for the magneto-optical defect center magnetometer 2500 to accommodate space constraints. Further still, the planar configuration also permits multiple excitation sources and/or collection devices to be utilized by the magneto-optical defect center magnetometer 2500. As shown in FIGS. 25-31, a primary green laser diode 2610 and a flash laser 2628 can be used as excitation sources, while two light pipes 2634 and photo diodes 2618 are utilized for collection devices. Of course additional excitation sources and/or collection devices may be used as well. The planar arrangement of the components of the magneto-optical defect center magnetometer 2500 is also beneficial for the mounting of optical components, such as the laser diodes, focusing lenses, light pipes, etc. on the PCB 2522 because the planar arrangement limits any z-direction variability such that alignment using the pins and alignment openings positions the optical components in a known position relative to the other components of the magneto-optical defect center

magnetometer 2500. Further still, the planar arrangement of the components of the magneto- optical defect center magnetometer 2500 provides a controlled reference plane for determining the vector of the detected external magnetic field. Still further, the planar arrangement permits usage of the mirror and/or filtering element 2632 that can be configured to confine any and/or substantially all of the emitted red light from the magneto-optical defect center element to within a small z-direction area to be directed toward the one or more photo diodes 2618. That is, the mirror and/or filtering element 2632 can be configured to direct any emitted red wavelength light from the magneto-optical defect center element to within the plane defined by the planar arrangement. [0568] In some implementations, the magneto-optical defect center magnetometer 2500 may have a weight of less than 0.5 kilograms, a range of power of 1-5 watts, and a size of approximately 7.62 centimeters in the x-direction by 10.16 centimeters in the y-direction by 1.905 centimeters in the z-direction. The magneto-optical defect center magnetometer 2500 may have a resolution of approximately 300 picoteslas, a bandwidth of 1 MHz, .and a measurement range of 1000 microteslas.

Two- Stage Optical Excitation

[0569] FIG. 33 is a schematic illustrating details of an optical light source 610, such as the green laser diode 711 of FIG. 8. The optical light source 610 may include a readout optical light source 3310 and reset optical light source 3320. The readout optical light source 3310 may be a laser or a light emitting diode, for example, which emits light in the green, for example. The readout optical light source 3310 induces fluorescence in the red from the NV diamond material 1200, where the fluorescence corresponds to an electronic transition of the NV electron pair from the excited state to the ground state. Light from the NV diamond material 1200 can be directed through an optical filter to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by an optical detector. Thus, the readout optical light source 3310 induces fluorescence which is then detected by the optical detector, such as optical detector 640 and/or photo diodes 718, i.e., the fluorescence induced by the readout optical light source 3310 is read out.

[0570] The reset optical light source 3320 of the optical light source 610 serves to reset the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired polarization. In general, it may be desired in a reset stage to reset the spin population to the desired spin state relatively quickly to reduce the reset time, and thus to increase sensor bandwidth. In this case the reset optical light source 3320 provides light of a relatively high power. Further, the reset optical light source 3320 may have a lower duty cycle than readout optical light source 3310, thus providing reduced heating of the system.

[0571] On the other hand, a relatively lower power may be desired for the readout optical light source 3310 to provide a higher accuracy readout. The relatively lower power readout optical light source 3310 beneficially allows for easier control of the spectral purity, a slower readout time with lower noise, reduced laser heating, and may be light weight and compact. Thus, the reset optical light source 3320 may provide light of a higher power than that of the readout optical light source 3310. The readout optical light source 3310 does provide some amount of a reset function. However, a lower powered light source takes longer to provide a reset and thus is tolerable.

[0572] Thus, the higher powered reset optical light source 3320 provides advantages such as decreasing the time required for reset. Moreover, the higher powered reset optical light source 3320 clears the previous polarization of the spin states of the NV centers. This may be important particularly in the case where the previous polarization is at another frequency pertaining to a different NV center crystallographic orientation. This is applicable to both pulse excitation schemes such as RF pulse sequence or spin-echo pulse sequence, as well as for continuous wave excitation where the RF field is scanned during the continuous wave excitation. For example, for continuous wave excitation where the RF field is scanned, the reset optical light source 3320 may reduce the time required to jump between Lorentzians, and clears out prior residual RF information, for, for example, vector magnetometry or thermally compensated scalar

magnetometry. This reduction of time allows for better vector estimation and/or increased sampling bandwidth. Thus the benefits of a higher power reset optical light source of lower duty cycle, wider beamwidth, and stronger power apply to either pulsed or continuous wave applications.

[0573] This combination of two optical light sources, one with a relatively high power to provide reset of the spin polarization and another to induce fluorescence for the readout provides a system with shorter reset times, while at the same time providing a high accuracy readout. The ratio of the power of the reset optical light source 3320 to the readout optical light source 3310 may be 10 to 1 or 20 to 1, or greater, for example.

[0574] Further the two optical light source magnetometer systems described herein improve the efficiency of the magnetometer by allowing for sensitive optical collection to be performed over a longer period using a low light density, low noise, light source while maintaining reasonable repolarization and reset times with a higher power light source when measurements are not critical. These two optical light source magnetometer systems allow for optimization of sensitivity via full excitation power versus collection integration time trade space, and further improves SWaP-C (size, weight, power and cost) design space by tailoring excitation source performance to specific needs. [0575] The readout optical light source 3310 may be a laser or an LED, for example, while the reset optical light source 3320 may a laser, or an LED. Exemplary arrangements are as follows. The readout optical light source 3310 may be a lower powered laser, and the reset optical light source 3320 may be a higher powered laser with a lower duty cycle. The readout optical light source 3310 may be a lower powered laser, and the reset optical light source 3320 may be a bank of LED flash-bulbs. The readout optical light source 3310 may be an LED, and the reset optical light source 3320 may be a bank of LED flash-bulbs.

Reset and read out illumination volumes

[0576] Referring to FIG. 33, the optical light source 610 may include a focusing lens 3322 to focus light from the reset optical light source 3320 onto the NV diamond material 1200.

Similarly, the optical light source 610 may include focusing optics 3312 to focus light from the readout optical light source 3310 onto the NV diamond material 1200. For example, the focusing optics 3312 may include lenses 3314, 3316, and 3318.

[0577] FIG. 34 illustrates the illumination volume 3410 of the light beam from the readout optical light source 3310 and the illumination volume 3420 of the light beam from the reset optical light source 3320 in the diamond material 1200. The illumination volume 3410 is shown between solid lines in FIG. 34, while the illumination volume 3420 is shown between the dashed lines. The focusing optics 3312 reduces the size of the illumination volume 3410 of the diamond material 1200, which is illuminated with the excitation beam from the readout optical light source 3310. In general, the illumination volume depends on the spot size of the focused light beam in the diamond material 1200. By reducing the illumination volume 3410 in the diamond material 1200, a higher light density for a given readout optical light source 3310 power is achieved, and further magnetic bias field inhomogeneities and RF field variations over the optically excited region of the diamond material can be reduced.

[0578] On the other hand, the illumination volume 3420 of the diamond material 1200, which is illuminated by the reset optical light source 3320 does not need to be as small as that for the readout optical light source 3310. The illumination volume 3420 of the diamond material 1200, which is illuminated by the reset optical light source 3320 should encompass the illumination volume 3410 of the diamond material 1200, which is illuminated by the readout optical light source 3310. In this way the reset optical light source 3320 will act to reset the NV spin states in the region of the diamond material 1200, which will be illuminated with the readout optical light source 3310.

Continuous Wave/RF Pulse Sequence Example

[0579] The present system may be used for continuous optical excitation, or pulsed excitation, such as modified Ramsey pulse sequence, modified Hahn-Echo, or modified spin echo pulse sequence. This section describes an exemplary continuous wave/pulse (cw-pulse) sequence. According to certain embodiments, a controller, such as controller 680 of FIGS. 6A-6C, controls the operation of the optical light source 610, the RF excitation source 630, and the magnetic field generator 670 to perform Optically Detected Magnetic Resonance (ODMR). The component of the magnetic field Bz along the NV axis of NV centers aligned along directions of the four different orientation classes of the NV centers may be determined by ODMR, for example, by using an ODMR pulse sequence according to a pulse sequence. The pulse sequence is a pulsed RF scheme that measures the free precession of the magnetic moment in the NV diamond material 620 and is a technique that quantum mechanically prepares and samples the electron spin state.

[0580] FIG. 35 is a timing diagram illustrating the continuous wave/pulse sequence. As shown in FIG. 35, a cw-pulse sequence includes optical excitation pulses and RF excitation pulses over a five-step period. In a first step, during a period 0, a first optical reset pulse 3510 from the reset optical light source 3320 is applied to the system to optically pump electrons into the ground state (i.e., ms = 0 spin state). This is followed by a first RF excitation pulse 3520 (in the form of, for example, a microwave (MW) π/2 pulse), provided by the RF excitation source 630, during a period 1. The first RF excitation pulse 3520 sets the system into superposition of the ms = 0 and ms = +1 spin states (or, alternatively, the ms = 0 and ms = -1 spin states, depending on the choice of resonance location). During a period 2, the system is allowed to freely precess (and accumulate phase) over a time period referred to as tau (τ). Next, a second RF excitation pulse 3540 (in the form of, for example, a MW π/2 pulse) is applied during a period 3 to project the system back to the ms = 0 and ms = +1 basis. During period 4 which corresponds to readout, optical light 3530 is provided by the readout optical light source 3310, to optically sample the system and a measurement basis is obtained by detecting the fluorescence intensity of the system. The optical light 3530 may be provided as an optical pulse, or as discussed further below, in a continuous manner throughout periods 0 through 4. Finally, the first optical reset pulse 3510 from the reset optical light source 3320 is applied again to begin another cycle of the cw-pulse sequence.

[0581] When the first optical reset pulse 3510 is applied again to reset to the ground state at the beginning of another sequence, the readout stage is ended. The cw-pulse sequence shown in FIG. 35 may be performed multiple times, wherein each of the MW pulses applied to the system during a given cw-pulse sequence includes a different frequency over a frequency range that includes RF frequencies corresponds to different NV center orientations. The magnetic field may be then be determined based on the readout values of the fluorescence change correlated to unknown magnetic fields.

Low power continuous optical excitation for RF pulse sequence

[0582] Still referring to FIG. 35, the optical light 3530 is provided by the readout optical light source 3310 in a continuous optical excitation manner. This provides a number of advantages over systems which turn on and off the light source providing light for optical readout during a RF sequence. Such systems which turn on and off the light source are susceptible to jitter noise interfering with the RF excitation source, and address this issue by increasing the laser light path length using optics so as to not be close to the RF excitation source, or by including a digital current source for the laser, for example.

[0583] By operating the readout optical light source 3310 in a continuous optical excitation manner, the system provides a number of advantages. The system does not need extra components such as an acousto-optic modulator (AOM), or a digital current source. Further, optics, such as mirrors and lenses, are not needed to increase the path length of the laser light path. Thus, the system may be less expensive. Still further, there is no need to synchronize turning on and off the light from readout optical light source 3310 with the RF excitation source, since the readout optical light source 3310 remains continuously on during the RF pulse sequence.

[0584] For the continuous optical excitation for RF pulse sequence, the readout optical light source 3310 is continuously on during the sequence, and thus continuously performs some amount of reset to the ground state throughout the sequence. Since the readout optical light source 3310 provides a relatively low power beam, however, the reset is tolerable.

[0585] FIG. 36 illustrates a magnetometry curve in the case of using a continuous optical excitation RF pulse sequence. FIG. 36 shows the dimmed luminescence intensity at readout as a function of RF frequency applied during the RF pulse sequences. As can be seen, there are 8 spin state transition envelopes, each having a respective resonance frequency, for the case where the diamond material has NV centers aligned along directions of four different orientation classes. This is similar to the 8 spin state transitions shown in FIG. 5 for continuous wave optical excitation where the RF frequency is scanned. The magnetic field component along each of the four different orientation classes can be determined in a similar manner to that in FIG. 5. FIG. 37 illustrates a magnetometry curve similar to that of FIG. 36, where the RF waveform, including τ, has been optimized for each ~ 12.5 MHz collection interval.

[0586] FIG. 38 illustrates a magnetometry curve for the left most resonance frequency of FIG. 37. In monitoring the magnetic field, the dimmed luminescence intensity, i.e., the amount the fluorescence intensity diminishes from the case where the spin states have been set to the ground state, of the region having the maximum slope may be monitored. If the dimmed luminescence intensity does not change with time, the magnetic field component does not change. A change in time of the dimmed luminescence intensity indicates that the magnetic field is changing in time, and the magnetic field may be determined as a function of time. For example, FIG. 39 illustrates the dimmed luminescence intensity as a function of time for the region of the maximum slope of FIG. 38.

[0587] FIG. 40 illustrates the normalized intensity of the luminescence as a function of time for diamond NV material for a continuous optical illumination of the diamond NV material during a time which includes application of RF excitation according to a RF pulse sequence. Initially, the NV centers have all been reset to the ground state and the normalized intensity has a maximum value. At a time ti, RF excitation according to a RF sequence is applied and the normalized polarization drops to a minimum value. The normalized intensity continues to increase after ti as the ground state population continues to increase. FIG. 41 illustrates a zoomed in region of FIG. 40 including time ti. The intensity may be read out for a time starting after ti and integrated. The time at which the read out stops and high power reset begins may be set based on the application.

Example Magneto-Optical Defect Center System With Additional Features

[0588] Referring to FIGS. 42A and 42B, a magnetic detection system 4200 includes a magneto-optical defect center material comprising at least one magneto-optical defect center that emits an optical signal when excited by an excitation light, a radio frequency (RF) exciter system configured to provide RF excitation to the magneto-optical defect center material, an optical light system configured to direct the excitation light to the magneto-optical defect center material, and an optical detector configured to receive the optical signal emitted by the magneto-optical defect center material based on the excitation light and the RF excitation. In particular, the magnetic detection system 4200 includes a housing 4205, an optical excitation source 4210, which directs optical light to a magneto-optical defect center material 4220 (e.g., a nitrogen vacancy (NV) diamond material with one or more NV centers, or another magneto-optical defect center material with one or more magneto-optical defect centers), a magnet ring mount 4215, and a bias magnet ring 4225. In alternative embodiments, additional, fewer, and/or different elements may be used. For example, although two light sources 421 OA and 4210B are shown in the

embodiments of FIGS. 42A and 42B, the optical excitation source 4210 may include any suitable number of light sources, such as one, three, four, etc. light sources. The magneto-optical defect center material 4220 may be held by a holder 4290. FIGS. 42 A and 42B illustrate the same components, except that an orientation of the magneto-optical defect center material 4220 is different in FIG. 42A than in FIG. 42B (discussed in further detail below).

[0589] Referring to FIGS. 43A and 43B, in some implementations, a housing 4305 can include a top plate 4306, a bottom plate 4307, one or more side plates 4308 and a main plate 4409 containing the components of the system 4200 therein. In some embodiments, the housing 4305 may be the housing 4205 of FIG. 42A. The one or more side plates 4308 may be integrated into the top plate 4306, the main plate 4409 and/or bottom plate 4307. The top plate 4306, bottom plate 4307, and/or main plate 4409 can be secured to the one or more side plates 4308 and/or the one or more side plates 4308 may include one or more openings therethrough wit an attachment member, such as a screw, bolt, etc., to couple the top plate 4306, the bottom plate 4307 and/or the main plate 4409 with the one or more side plates 4308. The coupling of the top plate 4306, the bottom plate 4307, and/or the main plate 4409 to the one or more side plates 4308 and/or to each other may substantially seal the magnetic detection system (e.g., the magnetic detection system 4200 of FIG. 42A) to limit exposure of the components therein to external light and/or contaminants. External light may interfere with reception of light from the magneto-optical defect center material when detecting a magnetic field, thereby introducing error into the measurements. Similarly, external contaminants, such as dust, dirt, etc., may disrupt transmission of the excitation source to the magneto-optical defect center material and/or reception of light from the magneto-optical defect center material, such as dust or dirt on the optical excitation source, on one or more lenses, on the magneto-optical defect center material itself, on a light tube transmitting light from the magneto-optical defect center component to the optical detector, and/or on the optical detector itself. The top plate and/or bottom plate may include convective cooling features, such as cooling fins 4313, to thermally dissipate heat transferred to the top plate 4306 and/or bottom plate 4307.

[0590] Referring to FIG. 44 A, the top plate 4306 may be made from any suitable material, for example, Noryl such as Black Noiyl PPO Plastic from McMaster-Carr, which is a modified PPE resin including amorphous blends of PPO polyphenylene ether (PPE) resin and polystyrene. Noryl provides high heat resistance, good electrical insulation properties, dimensional stability, low thermal conductivity, low reflection, and low density. Referring to FIG. 44B, the bottom plate 4307 may be made from the same material as the top plate 4306 or from a different material than the top plate 4306. For example, the bottom plate 4307 may be made from copper (e.g., copper per UN S C 10100, full hard to half hard temper), stainless steel (e.g., 316 stainless steel), aluminum (e.g., aluminum 6061 -T6 per ASTM 8209), or titanium grade 5 (e.g., Ti 6A1-4V). Referring to FIG. 44C, the side plate 4308 may be made from the same material as the top plate 4306 or the bottom plate 4307, or a different material than the top plate 4306 or the bottom plate 4307. In some implementatio s, the side plate 4308 may be made from Noryl such as Black Noryl PPO Plastic from McMaster-Carr. In other implementations, the side plate 4308 may be made of metal, or a metal coated with a low reflecting paint. Referring to FIGS. 44D (top view) and 44E (bottom view), the main plate 4409 may be made from the same material as the top plate 4306, the bottom plate 4307, or the side plate 4308, or the main plate 4409 can be made from a different material than the top plate 4306, the bottom plate 4307, or the side plate 4308. For example, the main plate 4409 may be made from copper (e.g., copper per UNS CI 0100, full hard to half hard temper), stainless steel (e.g., 316 stainless steel), aluminum (e.g., aluminum 6061-T6 per ASTM 8209), or titanium grade 5 (e.g., Ti 6A1-4V).

[0591] Referring to FIGS. 44A-44E, the top plate 4306, the bottom plate 4307, the side plate 4308 and the main plate 4409 may be any suitable shape having the same overall width and length. For example, each of the top plate 4306, the bottom plate 4307, the side plate 4308 and the main plate 4409 may be rectangular and have a width of 6.5 inches and a length of 7.5 inches. The top plate 4306, the bottom plate 4307, the side plate 4308 and the main plate 4409 may have the same thickness (i.e., height) or may vary in thickness. For example, the top plate 4306 may have a thickness of 0.050 inches, the bottom plate 4307 may have a thickness of 0.150 inches, the side plate 4308 may have a thickness of 0.950 inches, and the main plate 4409 may have a thickness of 0.325 inches, in the example illustrated in FIG. 43 A, the housing

components have the following ascending order in thickness: the top plate 4306, the bottom plate 4307, the main plate 4409, and the side plate 4308, The housing 4305 may have the overall dimensions of 7.5 inches x 6.5 inches x 1.515 inches (length x width x height). These dimensions are representative sizes that are foreseen to reduce as the technology progresses.

[0592] Referring to FIGS. 42A and 42B, in some embodiments, the components of the system 4200 may be mounted on a main plate such as the main plate 4409. In these embodiments, the main plate 4409 includes a plurality of through holes 4414 positioned to allow the location of the system components (e.g., the optical excitation source, the optical detection systems, the waveplate, the magneto-optical defect center material, the RF excitation source, the optical detector, the optical filter, the bias magnet ring mount, the bias magnet ring, the magnetic field generator, etc. of the system 4200 of FIG. 42A) to be repositioned within the housing 4305. As seen in FIG. 42A, components of the system 4200, for example, the optical components and the magnetic components, may be directly mounted to a top surface of the main plate 4409. Other components, for example, a circuit board, may be directly mounted to a bottom surface of the main plate 4409. The circuit board includes circuitry, for example, circuitry that drives the optical excitation source 4210, the photo diodes in the red collection 4217 and the green collection 4218 (described below), the RF exciter system (e.g., an RF amplifier), the thermal electric coolers 4500A, 4500B (described below), etc. By repositioning the location of the system components, it is possible to change at least one of a location or angle of incidence of the excitation light on the magneto-optical defect center material The system components may be repeatedly mounted to, removed from, relocated, and remounted to the main plate 4409. Any of the system components may be mounted in a particular set of through holes 4414 with attachment members, such as screws, bolts, etc. The through holes 4414 and attachment members may be threaded.

[0593] In the system 4200, light from the magneto-optical defect center material 4220 is directed through an optical filter to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band through a light pipe 4223, which in turn is detected by the optical detector 4240. A red collection 4217, a green collection 4218 and a beam trap 4219 may be mounted to an exterior of the bias magnet ring mount 4215 (i.e., the side of the bias magnet ring mount 4215 that does not face the magneto-optical defect center material 4220. The position of the green collection 4218 and the beam trap 4219 may be switched in other implementations. The red collection 4217 is a system of parts that includes, for example, a photo diode, the light pipe 4223, and filters that measure the red light emitted from the magneto- optical defect center material 4220. The red collection 4217 provides the main signal of interest, used to measure external magnetic fields. The green collection 4218 is a system of parts that includes, for example, a photo diode, a light pipe, and filters that measure the green light from the excitation light that passes through the magneto-optical defect center material 4220. The green collection 4218 may be used in tandem with the red collection 4217 to remove common mode noise in the detection signal, and therefore, increase device sensitivity. The green beam 4219 is configured to capture any portion of the excitation light (e.g., a green light portion) that is not absorbed by the magneto-optical defect center material 4220 to ensure that that the excitation light does not bounce around and add noise to the measurement. This noise could result from the excitation light bouncing off other components of the system 4200 and hitting the magneto-optical defect center material 4220 at a later time, where the excitation light would be absorbed and contaminate the signal. The excitation light that is not absorbed by the magneto- optical defect center material 4220 might also be captured on the green or red collection photodiodes, directly adding noise to those signals.

[0594] In some implementations, one or more separation plates 4211 may be provided between optical components of the system 4200 and other components of the system 4200, thereby physically isolating the optical components from other components (e.g., control circuitry, data analytics circuitry, signal generation circuitry, etc.). The separation plate 4211 may be a ground shield to also electrically isolate the optical components from the other components. In some implementations, the separation plate 421 1 may also thermally isolate the optical components from the other components. In the example illustrated in FIG. 42A, the separation plate 421 1 is integrally formed with the side plate of the housing 4205 (e.g., the separation plate 421 1 is integrally formed with the side plate 4308 of the housing 4305 of FIG. 44C). In other examples, the separation plate 4211 may be a separate piece provided within an inner perimeter of the side plate. [0595] In some implementations, the system 4200 may be hermetically sealed such as through the use of a gasket or other sealant (e.g., a gasket 4312 of the housing 4305 of FIG. 43 A). The gasket 4312 is configured to seal the top plate 4306, bottom plate 4307, one or more side plates 4308, and main plate 4409 together. The gasket 4312 may be made of any suitable material, for example, Noryl such as black Noryl PPO from McMaster-Carr and/or aluminum (e.g., aluminum 6061-T6 per ASTM B209). In one example, the gasket 4312 may have the following

dimensions: 6.5 inches x 7.5 inches x 0.040 inches. In implementations in which the housing includes a separation plate, the gasket 4312 is provided may include an internal contour corresponding to the location of the separator plate 4211.

[0596] Referring to FIG. 45, which illustrates components fixed to a bottom side of the main plate 4409, the system 4200 may further include one or more thermal electric coolers (TECs) configured to move heat from the main plate 4409. In the example of FIG. 45, two thermal electric coolers 4500A and 4500B are illustrated, but in other implementations, any number of thermal electric coolers may be used (for example, one, three, four, five, ten, etc.). A controller such as the controller 680 of FIGS. 6A-6C or separate controller (e.g., a proportional-integral- derivative (PID) controller) controls the thermal electric coolers 4500A and 4500B to maintain a predetermined temperature of the main plate 4409. This, in turn, controls a temperature of the components of the system 4200 (e.g., the laser diode of the optical excitation system 4210) and keeps the temperature stable. If the temperature of the components of the system 4200 (e.g., the laser diode of the optical excitation system 4210) is not stable, the sensitivity of the system 4200 is lowered.

[0597] The system 4200 further includes an RF exciter system 4230 that will be discussed in further detail below. The RF exciter system 4230 may include an RF amplifier assembly 4295. The RF amplifier assembly 4295 includes the RF circuitry that amplifies the signal from the RF source to a desired power level needed in the RF excitation element.

[0598] In implementations in which the system 4200 is hermetically sealed, a hydrogen absorber (not illustrated) and/or nitrogen cooling system (not illustrated) may be used. The hydrogen absorber can be positioned within a magnetic detection system such as the system 4200 of FIG. 42A to absorb hydrogen released from components therein that results from hydrogen trapped in materials used to make the components (e.g., metals, thermoplastics, etc.). The hydrogen absorber or hydrogen getter may be, for example, Cookson Group's STAYDRY® H2- 3000 Hydrogen and Moisture Getter, which employs an active hydrogen getter and desiccant for water absorption, dispersed in a flexible silicone polymer matrix. The hydrogen absorber material may be a film or a sheet that can be molded or stamped to a desired shape. In other implementations, other commercially available hydrogen absorbers or hydrogen getters may be used.

[0599] The nitrogen cooling system can be implemented in a magnetic detection system such as the system 4200 of FIG. 42 A to cool or otherwise reduce thermal loading on components therein, such as the optical excitation source 4210, the magneto-optical defect center material 4220, control circuitry, etc, and/or to prevent condensation. The nitrogen cooling system may- include a nitrogen source, a pressure regulator valve, and a controller configured to control a flow rate of nitrogen from the nitrogen source to the sy stem 4200. The nitrogen source may be, for example, a nitrogen air tank or a system capable of extracting nitrogen from air. In some implementations, the nitrogen cooling system may be in thermal communication (e.g., conductive) with the housing, for example the top plate 4306 and/or bottom plate 4307 of FIGS. 44 A. and 44B having the convective cooling features 4313. Accordingly, the nitrogen cooling system can form a heat transfer system to remove heat from one or more components within the system 4200 to be convectiveiy dissipated to atmosphere via the convective cooling features. As seen in FIG. 45, the various cables (e.g., the green and red collection cables, the RF cables, etc. are provided between the bottom side of the main plate 4409 and the bottom plate 4307 such that all of the components of the system 4200 are located within the housing 4205 (e.g., the housing 4305 of FIG. 44A).

Readout optical light source and reset optical light source

[0600] FIG. 46A is a schematic diagram of a portion 4600 of a magnetic detection system according to some embodiments. In some embodiments, the portion 4600 may be part of the magnetic detection system 4200 of FIG. 42 A. The portion 4600 includes an optical excitation source 4610, a magneto-optical defect center material 4620, an RF excitation system 4630, and an optical detector 4640. In some embodiments, the optical excitation source 4610, the magneto- optical defect center material 4620, the RF excitation system 4630, and the optical detector 4640 correspond to the optical excitation source 4210, the magneto-optical defect center material 4220, the RF excitation system 4230, and the optical detector 4240, respectively, of the system 4200 of FIG. 42 A. [0601] The optical excitation source 4610 may include a readout optical light source 4611 and reset optical light source 4612. The readout optical light source 4611 may be a laser or a light emitting diode, for example, which emits light in the green which may be focused to the magneto-optical defect center materia! 4620 via focusing optics 4631. The readout optical light source 4611 induces fluorescence in the red from the magneto-optical defect center material 4620, where the fluorescence corresponds to an electronic transition of the NV electron pair from the excited state to the ground state. Referring back to FIGS. 3 A and 3B, light from the magneto-optical defect center material (NV diamond material) 320 is directed through the optical filter 350 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 340. The readout optical light source 4611 induces fluorescence which is then detected by the optical detector 4640, i.e., the fluorescence induced by the readout optical light source 4611 is read out.

[0602] The reset optical light source 4612 may provide light which is focused to the magneto- optical defect center material 4620 via focusing optics 4632. The reset optical light source 4612 of the optical excitation source 4610 serves to reset the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired polarization. In general, it may be desired in a reset stage to reset the spin population to the desired spin state relatively quickly to reduce the reset time, and thus to increase sensor bandwidth. In this case the reset optical light source 4612 provides light of a relatively high power. Further, the reset optical light source 4612 may have a lower duty cycle than readout optical light source 4611, thus providing reduced heating of the system.

[0603] On the other hand, a relatively lower power may be desired for the readout optical light source 4611 to provide a higher accuracy readout. The relatively lower power readout optical light source 4611 beneficially allows for easier control of the spectral purity, a slower readout time with lower noise, reduced laser heating, and may be light weight and compact. Thus, the reset optical light source 4612 may provide light of a higher power than that of the readout optical light source 4611. The readout optical light source 4611 does provide some amount of a reset function. However, a lower powered light source takes longer to provide a reset and thus is tolerable.

[0604] The readout optical light source 4611 may be a laser or an LED, for example, while the reset optical light source 4612 may a laser, or an LED. Exemplary arrangements are as follows. The readout optical light source 4611 may be a lower powered laser, and the reset optical light source 4612 may be a higher powered laser with a lower duty cycle. The readout optical light source 4611 may be a lower powered laser, and the reset optical light source 4612 may be a bank of LED flash-bulbs. The readout optical light source 4611 may be an LED, and the reset optical light source 4612 may be a bank of LED flash-bulbs.

RF excitation source and NV diamond material

[0605] FIG. 47 illustrates some embodiments of a RF excitation source 4730 with the magneto- optical defect center material 4720 with NV centers. In some embodiments, the RF excitation source 4730 and the magneto-optical defect center material 4720 may correspond to the RF excitation source 4630 and the magneto-optical defect center material 4620, respectively, of FIGS. 46A and 46B. The RF excitation source 4730 includes a block portion 4740, RF feed connector 4750 with output 4751, and circuit board 4760. The RF feed connector 4750 may be electronically connected to a controller, such as the controller 680 of FIGS. 6A-6C, via a cable, for example, where the controller 680 provides an RF signal whereby the controller 680 may provide an RF signal to the RF feed connector 4750.

[0606] The block portion 4740 may include a support portion 4741, which supports the magneto-optical defect center material 4720. The block portion 4740 may further include a first wall portion 4742 and a second wall portion 4743 adjacent the support portion 4741. The first wall portion 4742 is on one side of the support portion 4741, while the second wall portion 4743 is on another side of the support portion 4741 opposite to the first side. The face of the second wall portion 4743 is slanted with respect to the first wall portion 4742, and thus the second wall portion 4743 makes an angle Θ with respect to the first wall portion 4742.

[0607] FIG. 46B shows some embodiments of a portion of a magnetic field detection system with a different arrangement of the light sources than in FIG. 46A. In the embodiments in which the RF excitation source 4730 and the magneto-optical defect center material 4720 correspond to the RF excitation source 4630 and the magneto-optical defect center material 4620 of FIGS. 46 A and 46B, respectively, the slanted second wall portion 4743 allows both the light emitted by the readout optical light source 4611 and the light emitted by the reset optical light source 4612 (see FIGS. 42A and 42B) to be directed at a proper angle to the magneto-optical defect center material 4620, 4720 with NV centers over a variety of arrangements of the readout optical light source 4611 and the reset optical light source 4612. In particular, the slanted second wall portion 4743 allows the readout optical light source 4611 and the reset optical light source 4612 to be positioned relatively close to each other, over a variety of arrangements of the readout optical light source 4611 and the reset optical light source 4612, while directing light to the same portion of the NV magneto-optical defect center material 4620, 4720 with NV centers.

[0608] In the arrangement of FIG. 46 A, the readout optical light source 4611 and the reset optical light source 4612 direct light on one side of the first wall portion 4742, while in FIG. 46B the readout optical light source 4611 and the reset optical light source 4612 direct light on another side of the of the first wall portion 4742. The face of the second wall portion 4743 is slanted with respect to the first wall portion 4742 to allow either of the arrangements of the plurality of the readout optical light source 4611 and the reset optical light source 4612 in FIGS. 46A or 46B to direct light to the magneto-optical defect center material 4620 with NV centers without blocking the light.

[0609] The block portion 4740 may comprise an electrically and thermally conductive material. For example, the block portion 4740 may be formed of a metal such as copper or aluminum. The good thermal conductivity of the block portion 4740 allows the block portion to function as a heat sink drawing heat away from the magneto-optical defect center material 4720 with NV centers. The electrically conductive nature of the block portion 4740 allows that a metallic material 4770 provided on the magneto-optical defect center material 4720 with NV centers may electrically short with the block portion 4740.

[0610] FIG. 48 illustrates the RF excitation source 4730 with the magneto-optical defect center material 4720 of FIG. 47 oriented on its side. The block portion 4740 has both side holes 4744 and bottom holes 4745. The side holes 4744 allow for mounting the block portion 4740 on its side for edge injection of light into the magneto-optical defect center material 4720. The bottom holes 4745 allow for mounting the block portion 4740 on its bottom for side injection of light. Other orientations for the block portion 4740 are possible.

[0611] FIG. 49 illustrates a top view of the circuit board 4760 of FIG. 47 in more detail with conductive traces shown. The circuit board 4760 includes a notch 4961 within which the RF feed connector 4750 is positioned. The circuit board 4760 may include an insulating board with conductive traces thereon. The output 4751 of the RF feed connector 4750 is electrically connected to a RF connector output trace 4975, which in turn is connected to a first trace 4980, which in turn is electrically connected to a second trace 4990. The traces 4975, 4980, and 4990 may be conducting metals, for example, such as copper or aluminum.

[0612] FIG. 50A illustrates a magneto-optical defect center material 5020 coated with a metallic material 5070 from a top perspective view. FIG. 50B illustrates the magneto-optical defect center material 5020 coated with a metallic material 5070 from a bottom perspective view. In some embodiments, the magneto-optical defect center material 5020 of FIGS. 50A and 50B corresponds to the magneto-optical defect center material 4620 of FIGS. 46A and 46B or the magneto-optical defect center material 4720 of FIG. 47. The metallic material 5070 may be gold, copper, silver, or aluminum, for example. The metallic material 5070 has a top 5070a, bottom 5070c, and a side portion 5070b connecting the top 5070a and bottom 5070c, and is designed to electrically short to the underlying block portion (e.g., the underlying block portion 4740 of FIG. 47) via the metallic material on the side portion, where the block portion 4740 functions as a RF ground. The second trace 4790 (see FIG. 49) is electrically connected to the metallic material 5070 on the magneto-optical defect center material 4720, 5020 with NV centers. As mentioned above, the electrically conductive nature of the block portion 4740 allows that the metallic material 4770 provided on the magneto-optical defect center material 4720 with NV centers may electrically short with the block portion 4740. In this regard, the second trace 4790 is electrically connected to the metallic material 4770, 5070, and the RF feed connector 4750 is driven by an RF signal, where the signal propagates along the traces 4775, 4780 and 4790. The second trace 4790 may have a width corresponding to the width of the magneto- optical defect center material 4720, 5020 with NV centers, and may be electrically connected to the metallic material 4770, 5070 along the width of the second trace 4790. The second trace 4790 may be electrically connected to the metallic material 5070 by a ribbon bond, for example.

[0613] Because the magneto-optical defect center material 4720, 5020 with NV centers is coated with a metallic material 5070, where the metallic material 5070 functions to provide an RF excitation to the magneto-optical defect center material 4720, 5020 with NV centers, a highly efficient RF excitation to the diamond material is possible.

Standing-Wave RF Exciter

[0614] Referring to FIG. 51 the RF excitation source 5130 provides RF radiation to the magneto-optical defect center material (NV diamond material) 5120. The system 5100 may include a magnetic field generator which generates a magnetic field, which may be detected at the magneto-optical defect center material 5120, or the magnetic field generator may be external to the system 5100. The magnetic field generator may provide a biasing magnetic field.

[0615] FIG. 51 illustrates a standing-wave RF exciter system 5100 (i.e., RF excitation source 330) according to some embodiments. In some embodiments, the RF exciter system 5100 corresponds to the RF excitation source 4730 of FIG. 47 and may be utilized in the system 4200 of FIG. 42A. The system 5100 includes a controller 5108 and an RF exciter circuit 5125. The RF exciter circuit 5125 includes an RF feed connector 5150 with an RF feed connector output 5151, and a conducting trace including a RF connector output trace 5175, a first trace 5180 and a second trace 5190. In some embodiments, the RF feed connector 5150, the RF feed connector output 5151, the RF connector output trace 5175, the first trace 5180 and the second trace 5190 correspond to the RF feed connector 4750, the RF feed connector output 4751, the RF connector output trace 4775, the first trace 4780 and the second trace 4790, respectively, of FIG. 47. The RF feed connector output 5151 of the RF feed connector 5150 is electrically connected to the RF connector output trace 5175. The RF connector output trace 5175 in turn is electrically connected to the first trace 5180, which in turn is electrically connected to second trace 5190. The first trace 5180 has an impedance which matches that of the system circuit impedance, for example, if the system circuit impedance is 50Ω, which is typical, the first trace 5180 should have an impedance of 50Ω.

[0616] The second trace 5190 has a width where the impedance of the second trace 5190 is lower than that of the first trace 5180. The second trace 5190 is electrically connected to a metallic material 5170 on a magneto-optical defect center material 5120. The metallic material 5170 is formed on a top, a bottom, and a side portion connecting the metal on the top and bottom, of the magneto-optical defect center material 5120, and is designed to electrically short to the underlying block portion 5140, which functions as a RF ground.

[0617] The controller 5108 is programmed or otherwise configured to control an RF excitation source 5130 so as to apply an RF signal to the RF feed connector output 5151. The controller 5108 may cause the RF excitation source 5130 to apply an RF signal to the RF feed connector 5150 which is then applied to the traces 5175, 5180, and 5190, which are short-circuited to the block portion 5140 via the metallic material 5170 on the magneto-optical defect center material 5120. [0618] The controller 5108 may control the RF excitation source 5130 so as apply an RF signal to RF feed connector 5150 such that a standing wave is produced within the magneto-optical defect center material 5120. In this regard, the controller 5108 may include or control the RF excitation source 5130, which may comprise an external or internal oscillator circuit, for example. The signal may be a modulated sinusoidal with a RF carrier frequency, for example. The second trace 5190 has a width where the impedance of the second trace 5190 is lower relative to that of the first trace 5180. For example, if the impedance of the first trace 5180 is about 50Ω, then the impedance of the second trace 5190 may be less than 10Ω, for example. The low impedance of the second trace 5190 provides a relatively high RF field which is applied to the magneto-optical defect center material 5120.

[0619] The second trace 5190 may have a relatively wide width, such as for example greater than 2 mm, so that the second trace 5190 has a relatively low impedance. The traces 5180 and 5190, along with the metallic material 5170 on the magneto-optical defect center material 5120, act as a microstrip line. The relatively wide second trace 5190 along with the metallic material 5170 which is coated on the magneto-optical defect center material 5120 beneficially provides for a small field gradient of the RF field applied to the NV diamond material 5120. The good RF field uniformity is due in part to the arranged microstrip line.

[0620] The metallic material 5170 on the magneto-optical defect center material 5120 is located at the end, and is part of, the microstrip line, which also comprises the traces 5180 and 5190. The short circuiting of the metallic material 5170 to the block portion 5140 provides current and thus an applied field maxima at the diamond. The standing wave field which is applied results in doubling the RF field applied to the magneto-optical defect center material 5120. This means a 4-times decrease in the power needed to maintain a particular RF field.

[0621] Thus, providing a standing wave application of the RF field to the magneto-optical defect center material 5120 using a microstrip line short circuit at the magneto-optical defect center material 5120 provided with the metallic material 5170 covering the magneto-optical defect center material 5120 provides a power reduction needed to maintain the RF field intensity in the magneto-optical defect center material 5120, and a low RF field gradient in the magneto- optical defect center material 5120.

[0622] The magnitude of the RF field applied at the magneto-optical defect center material 5120 will also depend on the length of the microstrip line, which includes traces 5180 and 5190, along with the metallic material 5170 on the magneto-optical defect center material 5120. In an ideal case a length of the microstrip line of a quarter wavelength of the RF carrier frequency will produce the maximum current, and thus the maximum RF field applied to the magneto-optical defect center material 5120. Incorporating the diamond to the system, however, affects the nature of the standing wave, resulting in a different optimal length than a quarter wavelength. This length can be found computationally, and is generally shorter than a quarter wavelength. Thus, the length of the microstrip lines is about a quarter wavelength and is set to provide a maximum magnitude of the RF applied field applied to the magneto-optical defect center material 5120.

[0623] FIGS. 52 A and 52B are circuit diagrams illustrating RF exciter systems including the RF exciter circuit 5125 according to some embodiments having a non-reciprocal isolation arrangement and a balanced amplifier arrangement, respectively.

[0624] Except for small ohmic and radiative losses in the exciter, all of the power incident to the microstrip line will be reflected back from the short to an RF amplifier of the system. To avoid this back reflection, the systems 5200A and 5200B in FIGS. 52A and 52B, respectively, include an RF termination component. The RF termination component may be, for example, a non-reciprocal isolator device as in FIG. 52A, or a balanced amplifier configuration as in FIG. 52B. If the non-reciprocal isolator device has magnetic materials, a balanced amplifier is preferred to avoid interference due to the magnetic fields.

[0625] FIG. 52A includes, in addition to RF exciter circuit 5225, controller 5208 and RF excitation source 5230 of the FIG. 51 system (e.g., the RF exciter circuit 5125, controller 5108 and RF excitation source 5130 of the FIG. 51 system), an amplifier 5210 and a RF isolator 5220. The RF signal from the RF excitation source 5230 is amplified by the amplifier 5210, and the amplified signal is input to the RF isolator 5220, which provides an RF termination function, and is then output to the RF exciter circuit 5225.

[0626] The balanced amplifier arrangement of FIG. 52B includes, in addition to RF exciter circuit 5225, controller 5208 and RF excitation source 5230 of the FIG. 52A system (e.g., the RF exciter circuit 5125, controller 5108 and RF excitation source 5130 of the FIG. 51 system), a first quadrature component 5235 arranged before two amplifiers 5240 and 5245, followed by a second quadrature component 5250 arranged after the two amplifiers 5240 and 5245. The RF signal from the RF excitation source 5230 is input to the first quadrature component 5235, and then quadrature result is input to the two amplifiers 5240 and 5245. The amplified signal from the two amplifiers 5240 and 5245 is then output to the second quadrature component 5250, and the quadrature result is input to the RF exciter circuit 5225.

[0627] FIGS. 53 A and 53B illustrate the estimated applied field for, respectively, a prior RF exciter, and an RF exciter with a short circuited microstrip line with a standing wave applied field at the diamond. The prior RF exciter for FIG. 53 A employed a 16W RF power amplifier running at saturation. The RF exciter with a short circuited microstrip line with a standing wave applied field employed a 300 mW low noise amplifier (LNA) running in the linear regime (40 mW in) to produce an equivalent applied field. FIGS. 53 A and 53B illustrate the applied field both with and without a balanced amplifier in the circuit. As can be seen, for the RF exciter with a short circuited microstrip line with a standing wave applied field in FIG. 53B the applied field (Relative |H|) as a function of frequency over the frequency range of 2.6 to 3.1 GHz shows a flat frequency response in particular with an addition of a balanced amplifier. The frequency response shown in FIG. 53B is an improvement over that in FIG. 53 A.

[0628] The RF exciter with a short circuited microstrip line with a standing wave applied field at the diamond described above, provides a number of advantages. The field intensity applied to the diamond for a given incident RF power is maximized. The RF exciter provides both a small field gradient and a flat frequency response. Further setting the microstrip line of the RF exciter to have a length of about a quarter wavelength produces maximum current, and thus maximum applied field.

Precision Adjustability of Optical Components

[0629] FIG. 54 illustrates an optical light source 5410 (i.e., an optical excitation assembly) with adjustable spacing features in accordance with some illustrative embodiments. The optical light source 5410 may be, for example, one of the light sources in the optical excitation source 4210 of FIG. 42 A. The optical light source 5410 may be, for example, the readout optical light source 4611 and reset optical light source 4612. The optical light source 5410 includes, in brief, an optical excitation module 5420 (e.g., a laser diode), an optical excitation module mount 5425, a lens mount 5430, one or more X axis translation slots 5440, one or more y axis translation slots 5450, Z axis translation material 5460 (e.g., shims), an X axis lens translation mechanism 5470, and a Y axis lens translation mechanism 5480. In addition, FIG. 54 comprises an illustration of a representation of a light beam 5495. [0630] Still referring to FIG. 54 and in further detail, the optical light source 5410 comprises an optical excitation module 5420. In some implementations, the optical excitation module 5420 is a directed light source. In some implementations, the optical excitation module 5420 is a light emitting diode. In some implementations, the optical excitation module 5420 is a laser diode. In some implementations, the optical light source 5410 comprises an optical excitation module mount 5425 that is configured to fasten the optical excitation module 5420 in position relative to the rest of the optical light source 5410.

[0631] In some implementations, the optical light source 5410 further comprises a lens mount 5430. In some implementations, the lens mount 5430 is configured to fasten a plurality of lenses in position relative to each respective lens as well as configured to fasten a plurality of lenses in position relative to the rest of the optical light source 5410.

[0632] In some implementations, the optical light source 5410 further comprises one or more X axis translation slots 5440. The one or more X axis translation slots 5440 can be configured to allow for a positive or negative adjustment of the optical light source 5410 in a linear direction. In some implementations, the linear direction is orthogonal to a path of a light beam 5495 generated by the optical light source 5410. In some implementations, the X axis translation slots 5440 are configured to, upon adjustment, be used to fasten the optical light source 5410 to an underlying mount. In some implementations, the X axis translation slots 5440 are configured to accept a screw or other fastener that can be tightened to an underlying mount to fasten the optical light source 5410 to an underlying mount in a fixed location. In some implementations, the X axis translation slots 5440 are used to align the path of a light beam 5495 to a desired target destination.

[0633] In some implementations, the optical light source 5410 further comprises one or more Y axis translation slots 5450. The one or more Y axis translation slots 5450 can be configured to allow for a positive or negative adjustment of the optical light source 5410 in a linear direction. In some implementations, the linear direction is parallel to a path of a light beam 5495 generated by the optical light source 5410. In some implementations the linear direction is orthogonal to the linear direction of the one or more X axis translation slots 5440. In some implementations, the Y axis translation slots 5450 are configured to, upon adjustment, be used to fasten the optical light source 5410 to an underlying mount. In some implementations, the Y axis translation slots 5450 are configured to accept a screw or other fastener that can be tightened to an underlying mount to fasten the optical light source 5410 to an underlying mount in a fixed location. In some implementations, the Y axis translation slots 5450 are used to adjust the distance of the path of a light beam 5495 from a desired target destination.

[0634] In some implementations, the optical light source 5410 further comprises Z axis translation material 5460. In some implementations, the Z axis translation material 5460 comprises one or more shims. In some implementations the Z axis translation material 5460 can be added to or removed from the optical light source 5410 for a positive or negative adjustment of the optical light source 5410 in a linear direction relative to an underlying mount to which the optical light source 5410 is fastened. In some implementations, the linear direction is orthogonal to two or more of the linear direction of the one or more X axis translation slots 5440, the linear direction of the one or more Y axis translation slots 5450, and/or the path of a light beam 5495 generated by the optical light source 5410. In some implementations the linear direction is orthogonal to the linear direction of the one or more X axis translation slots 5440. In some implementations, the Z axis translation material 5460 is configured to, upon adjustment, be used to alter a distance of the fastening of the optical light source 5410 to an underlying mount. In some implementations, the Z axis translation material 5460 is configured to accommodate the one or more X axis translation slots 5440 and/or the one or more Y axis translation slots 5450 with similar or matching slots in the Z axis translation material 5460 in order to accept a plurality of screws or other fasteners that can be tightened to an underlying mount to fasten the optical light source 5410 to the underlying mount in a fixed location. In some implementations, the Z axis translation material 5460 are used to adjust the path of a light beam 5495 to a desired target destination.

[0635] In some implementations, the optical light source 5410 further comprises an X axis lens translation mechanism 5470. The X axis lens translation mechanism 5470 can be configured to allow for a positive or negative adjustment of the one or more lenses in a lens mount 5430 in a linear direction. In some implementations, the linear direction is parallel to a path of a light beam 5495 generated by the optical light source 5410. In some implementations, the X axis lens translation mechanism 5470 is used to align a lens to a path of a light beam 5495. In some implementations, the X axis lens translation mechanism 5470 is a drive screw mechanism configured to move the one or more lenses in a lens mount 5430 in the linear direction. [0636] In some implementations, the optical light source 5410 further comprises a Y axis lens translation mechanism 5480. The Y axis lens translation mechanism 5480 can be configured to allow for a positive or negative adjustment of the one or more lenses in a lens mount 5430 in a linear direction. In some implementations, the linear direction is orthogonal to a path of a light beam 5495 generated by the optical light source 5410. In some implementations, the Y axis lens translation mechanism 5480 is used to align a lens to a path of a light beam 5495. In some implementations, the Y axis lens translation mechanism 5480 is a drive screw mechanism configured to move the one or more lenses in a lens mount 5430 in the linear direction.

[0637] In some implementations, the optical light source 5410 further comprises a Z axis lens translation mechanism 5485. The Z axis lens translation mechanism 5485 can be configured to allow for a positive or negative adjustment of the one or more lenses in a lens mount 5430 in a linear direction. In some implementations, the linear direction is orthogonal to a path of a light beam 5495 generated by the optical light source 5410. In some implementations, the linear direction is orthogonal to a path of a light beam 5495 generated by the optical light source 5410 and to one or more of the linear adjustment of the X axis lens translation mechanism 5470 or the Y axis lens translation mechanism 5480. In some implementations, the Z axis lens translation mechanism 5485 is used to align a lens to a path of a light beam 5495. In some implementations, the Z axis lens translation mechanism 5485 is a drive screw mechanism configured to move the one or more lenses in a lens mount 5430 in the linear direction.

[0638] FIG. 55 illustrates a cross section as viewed from above of a portion of the optical light source 5410 in accordance with some illustrative embodiments. The optical assembly cross section includes, in brief, an optical excitation module 5420 (e.g., a laser diode), an optical excitation module mount 5425, a lens mount 5430, one or more Y axis translation slots 5450, one or more lenses 5510, a lens spacer 5520, and a lens retaining ring 5530.

[0639] Still referring to FIG. 55 and in further detail, the optical assembly cross section comprises an optical excitation module 5420. In some implementations, the optical excitation module 5420 is a directed light source. In some implementations, the optical excitation module 5420 is a light emitting diode. In some implementations, the optical excitation module 5420 is a laser diode. In some implementations, the optical assembly cross section comprises an optical excitation module mount 5425 that is configured to fasten the optical excitation module 5420 in position relative to the rest of the optical assembly cross section. [0640] In some implementations, the optical assembly cross section further comprises a lens mount 5430. In some implementations, the lens mount 5430 is configured to fasten a plurality of lenses 5510 in position relative to each respective lens 5510 as well as configured to fasten a plurality of lenses 5510 in position relative to the rest of the optical assembly cross section. In some implementations, a lens spacer 5520 is configured to maintain a fixed distance between one or more lenses 5510. In some implementations, a lens retaining ring 5530 is configured to hold one or more lenses 5510 in a proper position relative to the lens mount 5430.

[0641] In some implementations, the optical assembly cross section further comprises one or more Y axis translation slots 5450. The one or more Y axis translation slots 5450 can be configured to allow for a positive or negative adjustment of the optical assembly cross section in a linear direction. In some implementations, the linear direction is parallel to a path of a light beam generated by the optical assembly cross section. In some implementations the linear direction is orthogonal to the linear direction of the one or more X axis translation slots 5440. In some implementations, the Y axis translation slots 5450 are configured to, upon adjustment, be used to fasten the optical light source (e.g., the optical light source 5410) to an underlying mount. In some implementations, the Y axis translation slots 5450 are configured to accept a screw or other fastener that can be tightened to an underlying mount to fasten the optical assembly cross section to an underlying mount in a fixed location. In some implementations, the Y axis translation slots 5450 are used to adjust the distance of the path of a light beam from a desired target destination.

Waveplate

[0642] FIG. 56 is a schematic diagram illustrating a waveplate assembly 5600 according to some embodiments. In some implementations, the waveplate assembly 5600, in brief, may be comprised of a waveplate 5615, a mounting disk 5610, a mounting base 5625, a pin 5630, and a screw lock 5640. In some embodiments, the waveplate 5615 may correspond to the waveplate 315 of FIG. 3B. In some implementations, the waveplate assembly 5600 may be configured to adjust the polarization of the light (e.g., light from a laser) as the light is passed through the waveplate assembly 5600. In some implementations, the waveplate assembly 5600 may be configured to mount the waveplate 5615 to allow for rotation of the waveplate 5615 with the ability to stop the plate in to a position at a specific rotation. In some implementations, the waveplate assembly 5600 may be configured to allow for rotation of the waveplate 5615 with the ability to lock the plate in to a position at a specific rotation. Stopping the waveplate 5615 at a specific rotation may allow the configuration of the waveplate assembly 5600 to tune the polarization of the light passing through the waveplate 5615. In some implementations, the waveplate 5615 tunes the polarization of the light passing through by being configured to have a different refractive index for a different polarization of light. In these implementations, the waveplate 5615 operates using the principle of birefringence, where the refractive index of the material of the waveplate 5615 depends on the polarization of the light and the phase is changed between two perpendicular polarizations by π (i.e., half a wave), effectively rotating the polarization of the light passing through it by ninety degrees. In some implementations, the waveplate assembly 5600 may be configured to adjust the polarization of the light such that the orientation of a given lattice of a magneto-optical defect center material allows the contrast of a dimming Lorentzian to be deepest and narrowest such that the slope of each side of the

Lorentzian is steepest. In some implementations, when the light polarization (e.g., laser polarization is lined up geometrically with the orientation of the given lattice, the contrast and the narrowness of the dimming Lorentzian, the portion of the light that is sensitive to magnetic fields is deepest and narrowest, meaning that the slope of each side of Lorentzian is steepest, and that equates directly to sensitivity for the magnetic field. In some implementations, one polarization of the light (e.g., laser light) aligns with one axis or one crystal lattice of the magneto-optical defect center material, the two Lorentzians associated with that one lattice are steep and narrow, the others are not as steep and not as narrow. The slope of each side of the Lorentzian is steepest when the polarization of the light is lined up geometrically with the orientation of the given lattice of the magneto-optical defect center material. In some

implementations where the waveplate 5615 is a half-wave plate, the waveplate assembly 5600 may be configured such that the polarization of the light is lined up with the orientation of a given lattice of a magneto-optical defect center material such that it allows extraction of maximum sensitivity of the lattice (i.e., maximum sensitivity of a vector in free space). In some implementations, the waveplate assembly 5600 may be configured such that four determined positions of the waveplate 5615 increase (e.g., maximize) the sensitivity across all the different lattices of a magneto-optical defect center material. In some implementations, the orientation of the light waves consequent to the polarization of light causes the light waves to coincides with an orientation of one or more of the defect centers, thereby imparting substantially increased energy transfer to the one or more defect centers with coincident orientation while imparting substantially decreased energy transfer to the defect centers that are not coincident. In some implementations, the waveplate assembly 5600 may be configured where the position of the waveplate 5615 is such that similar sensitivities are achieved to the four Lorentzians

corresponding to lattice orientations of a magneto-optical defect center material.

[0643] In some implementations where the waveplate 5615 is a quarter-wave plate, the waveplate assembly 5600 may be configured such that the polarization of the light is lined up with the orientation of a given lattice of a magneto-optical defect center material such that it allows extraction of maximum sensitivity of the lattice (i.e., maximum sensitivity of a vector in free space). In some implementations, the waveplate assembly 5600 may be configured such that certain determined positions of the waveplate 5615 increase (e.g., maximize) the sensitivity across all the different lattices of a magneto-optical defect center material. In some

embodiments, the orientation of the light waves consequent to the polarization of light causes the light waves to coincides with an orientation of one or more of the defect centers, thereby imparting substantially increased energy transfer to the one or more defect centers with coincident orientation while imparting substantially decreased energy transfer to the defect centers that are not coincident. In some embodiments, the circular polarization of the light waves consequent to the polarization of light caused by passing through the quarter-wave assembly causes the light waves to impart substantially equivalent energy transfer to a plurality of defect centers such that similar sensitivities are achieved to the four Lorentzians corresponding to lattice orientations of the plurality of defect centers in the magneto-optical defect center material.

[0644] Still referring to FIG. 56, the mounting disk 5610, in some implementations, is attached to a waveplate 5615. The mounting disk 5610 may be attached to a waveplate 5615 such that rotation of the mounting disk 5610 also correspondingly rotates the waveplate 5615. In some implementations, the mounting disk 5610 may be securely adhered (e.g., using epoxy) to a portion of the perimeter of the waveplate 5615. In some implementations, the mounting disk 5610 may be configured to rotate freely and also be locked in place relative to the rest of the waveplate assembly 5600 while the adhered waveplate 5615 may be rotated and locked in place due to the attachment to the mounting disk 5610. In some implementations, the waveplate assembly 5600 may be comprised of a waveplate 5615, a mounting disk 5610, a mounting base 5625, a pin 5630, and a screw lock 5640. [0645] The mounting base 5625, in some implementations, may be configured to restrict a movement of rotation of a waveplate 5615. In some implementations, the movement of rotation is restricted to a single plane such that the rotation occurs around an axis of the waveplate 5615. In some implementations, the mounting base 5625 is configured to restrict a movement of rotation of the mounting disk 5610 such that the rotation of the waveplate 5615 attached to the mounting disk 5610 occurs around an axis of the waveplate 5615. In some implementations, one or more pins 5630 may be attached to the mounting disk 5610 slide through a slot in the mounting base 5625 to allow the mounting disk 5610 to rotate relative to the mounting base 5625. The one or more pins 5630 may be adhered to the mounting disk 5610 such that the one or more pins 5630 stay relative in position to the mounting disk 5610 during rotation of the mounting disk 5610 relative to the mounting base 5625. In some implementations, the one or more pins 5630 may be adhered directly to the waveplate 5615 such that the one or more pins 5630 stay relative in position to the waveplate 5615 during rotation of the waveplate 5615 relative to the mounting base 5625. In some implementations, one or more screw locks 5640 are attached to the mounting disk 5610 and are configured to restrict movement of the mounting base 5625 relative to the mounting base 5625 when tightened. In some implementations, one or more screw locks 5640 are attached to the mounting disk 5610 and lock the mounting disk 5610 in place when tightened. In some implementations, one or more screw locks 5640 may be attached directly to the waveplate 5615 and are configured to restrict movement of the waveplate 5615 when the one or more screw locks 5640 are tightened. In some implementations, the mounting disk 5610 and/or waveplate 5615 can be locked in place or have rotational motion restricted through other means such as through frictional force, electromagnetic force (e.g., an electromagnet is activated to restrict further rotation), other mechanical forces, and the like.

[0646] In some implementations, the waveplate assembly 5600 is configured such that a position of the waveplate 5615 is determined as an initial calibration for a light directed through a waveplate 5615. In some implementations, the performance of the system may be affected by the polarization of the light (e.g., light from a laser) as it is lined up with a crystal structure of the magneto-optical defect center material (e.g., NV diamond material). In some implementations, a waveplate 5615 is mounted to allow for rotation of the waveplate 5615 with the ability to stop and/or lock the half-wave after an initial calibration determines the eight Lorentzians associated with a given lattice with each pair of Lorentzians associated with a given lattice plane symmetric around the carrier frequency. In some implementations, the initial calibration may be set to allow for high contrast with steep Lorentzians for a particular lattice plane. In some implementations, the initial calibration may be set to create similar contrast and steepness of the Lorentzians for each of the four lattice planes.

[0647] FIG. 57 is a half-wave plate schematic diagram illustrating a change in polarization of light when the waveplate 5615 is a half-wave plate. In some implementations, plane polarized light entering the half-wave plate is rotated to an angle that is twice the angle (i.e., 2Θ) of the entering plane polarized light with respect to a fast axis of the half-wave plate. In some implementations, the half-wave plate is used to turn left circularly polarized light into right circularly polarized light or vice versa.

[0648] FIG. 58 is a quarter-wave plate schematic diagram illustrating a change in polarization of light when the waveplate 5615 is a quarter-wave plate. In some implementations, plane polarized light entering the quarter-wave plate is turned into circularly polarized light. The exiting polarized light may be circularly polarized when the entering plane-polarized light is at an angle of 45 degrees to the fast or slow axis as shown in FIG. 58.

[0649] In order to tune the magnetic field measurement for certain axes of the magneto-optical defect center materials the polarization of light entering the magneto-optical defect center material may be controlled. During manufacture of a sensor system, there may be small variations in how a magneto-optical defect center material is mounted to the sensor such that axes have deviation in orientation as well as inherent differences between different magneto- optical defect center materials. In such manufacturing, a calibration can be conducted by adjusting the polarization of the light to benefit the final intended purpose of the sensor.

[0650] In some implementations a sensor is described comprising an optical excitation source emitting green light, a magneto-optical defect center material with defect centers in a plurality of orientations, and a half-wave plate. At least some of the green light may pass through the half- wave plate, rotating a polarization of such green light to thereby provide an orientation to the light waves emitted from the half-wave plate. The half-wave plate may be capable of being orientated relative to the defect centers in a plurality of orientations, wherein the orientation of the light waves coincides with an orientation of the defect centers, thereby imparting

substantially increased energy transfer to the defect center with coincident orientation while imparting substantially decreased energy transfer to the defect centers that are not coincident. [0651] In some implementations, a sensor is described comprising a waveplate assembly, an optical excitation source and a magneto-optical defect center material with defect centers. The waveplate assembly can include a waveplate, mounting base, and a mounting disk. The mounting disk can be adhered to the waveplate. The mounting base can be configured such that the mounting disk can rotate relative to the mounting base around an axis of the waveplate.

[0652] In some implementations, the sensor can be configured to direct light from the optical excitation source through the waveplate before the light is directed to the magneto-optical defect center material. In some implementations, the sensor can further comprise a pin adhered to the mounting disk. The mounting base can comprise a slot configured to receive the pin, the pin can slide along the slot and the mounting disk can rotate relative to the mounting base around the axis of the waveplate with the axis perpendicular to a length of the slot. In some

implementations, the magneto-optical defect center material with defect centers can be comprised of a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers. In some implementations, the optical excitation source can be one of a laser (e.g., a laser diode) or a light emitting diode. In some implementations, the sensor can further comprise a screw lock attached to the mounting disk. The screw lock can be configured to prevent rotation of the mounting disk relative to the mounting base when tightened. In some implementations, the sensor can further comprise a controller electrically coupled to the waveplate assembly. The controller can be configured to control an angle of the rotation of the waveplate relative to the mounting base.

[0653] In some implementations, an assembly can comprise a half-wave plate, a mounting base, an optical excitation source, and a magneto-optical defect center material with defect centers. The mounting base can be configured such that the half-wave plate can rotate relative to the mounting base around an axis of the half-wave plate. In some implementations, the assembly can further comprise a pin adhered to the mounting disk. The mounting base can comprise a slot configured to receive the pin, the pin can slide along the slot and the mounting disk can rotate relative to the mounting base around the axis of the half-wave plate with the axis perpendicular to a length of the slot. In some implementations, the magneto-optical defect center material with defect centers can be comprised of a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers. In some implementations, the optical excitation source can be one of a laser (e.g., a laser diode) or a light emitting diode. In some implementations, the assembly can further comprise a screw lock attached to the mounting disk. The screw lock can be configured to prevent rotation of the mounting disk relative to the mounting base when tightened. In some implementations, the assembly can further comprise a controller electrically coupled to the half- wave plate assembly. The controller can be configured to control an angle of the rotation of the half-wave plate relative to the mounting base.

[0654] In some implementations, a sensor assembly is described comprising a mounting base and a half-wave plate assembly. The half-wave plate assembly can further comprise a half-wave plate, an optical excitation means for providing optical excitation through the half-wave plate, a magneto-optical defect center material comprising a plurality of magneto-optical defect centers, and a detector means, for detecting optical radiation.

[0655] In some implementations, an assembly is described and can comprise a half-wave plate, a mounting base, an optical excitation source, and a magneto-optical defect center material with defect centers. The mounting base can be configured such that the half-wave plate can rotate relative to the mounting base around an axis of the half-wave plate.

Holder for Magneto-Optical Defect Center Material

[0656] FIGS. 59A-59C are three-dimensional views of a holder 5900 for the magneto-optical defect center material 5920 (e.g., a nitrogen vacancy (NV) diamond material) in accordance with some illustrative embodiments. In some embodiments, the holder 5900 corresponds to the holder 4290 of FIG. 42A. An illustrative holder 5900 includes the magneto-optical defect center material 5920, a base 5906, a radio frequency (RF) circuit board 5912, an RF signal connector 5915, first mounting holes 5924, and second mounting holes 5925. In the embodiment illustrated in FIGS. 59A-59C, the holder 5900 includes locating slots 5930. In alternative embodiments, additional, fewer, and/or different elements may be used.

[0657] As shown in FIG. 59A, the magneto-optical defect center material 5920 is attached to the base 5906. The magneto-optical defect center material 5920 can be mounted to the base 5906 using any suitable securing mechanism, such as a glue or an epoxy. In alternative embodiments, screws, bolts, clips, fasteners, or etc. may be used. In some embodiments, the magneto-optical defect center material 5920 can be fixed to the RF circuit board 5912. For example, a ribbon bond can be used between the magneto-optical defect center material 5920 and the RF circuit board 5912. In alternative embodiments, any other suitable methods can be used to attach the magneto-optical defect center material 5920 to the RF circuit board 5912. [0658] In the embodiment shown in FIG. 59A, one side of the magneto-optical defect center material 5920 is adjacent to the base 5906, and one side of the magneto-optical defect center material 5920 is adjacent to the RF circuit board 5912. In such an embodiment, other sides of the magneto-optical defect center material 5920 are not adjacent to opaque objects and, therefore, can have light injected therethrough. In the embodiment shown in FIG. 59A, the magneto-optical defect center material 5920 has eight sides, six of which are not adjacent to an opaque object. In alternative embodiments, the magneto-optical defect center material 5920 can have greater than or fewer than eight sides.

[0659] For example, the magneto-optical defect center material 5920 includes two sides 5921 and 5922 through which light can be injected into the magneto-optical defect center material 5920. In such an example, light can be injected through the edge side 5921 or the face side 5922. When light is injected through the edge side 5921, the defect centers in the magneto-optical defect center material 5920 are excited less uniformly than when light is injected through the face side 5922. Also, when light is injected through the edge side 5921, more of the defect centers in the magneto-optical defect center material 5920 are excited than when light is injected through the face side 5922.

[0660] In some illustrative embodiments, the more of the defect centers in the magneto-optical defect center material 5920 are excited by light, the more red light is emitted from the magneto- optical defect center material 5920. In some illustrative embodiments, the more uniformly that the defect centers in the magneto-optical defect center material 5920 are excited by the light the more sensitive the magnetometer may be. Thus, in some instances, it may be preferential to inject light into the edge side 5921 while in other instances it may be preferential to inject light into the face side 5922.

[0661] In the embodiment shown in FIG. 59A, the side of the magneto-optical defect center material 5920 opposite the edge side 5921 is not obstructed by an opaque object (e.g., base 5906 or the RF circuit board 5912). That is, light injected into the edge side 5921 that is not absorbed by defect centers (e.g., used to excite defect centers) of the NV diamond material 620 may pass through the magneto-optical defect center material 5920. In an illustrative embodiment the light that passes through the magneto-optical defect center material 5920 may be sensed by an optical sensor. The light that passes through the magneto-optical defect center material 5920 may be used to eliminate or reduce correlated noise in the light captured by the optical detector. [0662] In the embodiment shown in FIG. 59A, the side of the magneto-optical defect center material 5920 that is opposite the face side 5922 is adjacent to the base 5906. Thus, light that is injected through the face side 5922 that is not absorbed by defect centers is absorbed by the base 5906. That is, the light not absorbed by the defect centers is not detected by a light detector to be used to eliminate or reduce correlated noise. In some alternative embodiments, the base 5906 includes a through hole that unabsorbed light can pass through.

[0663] As shown in FIG. 59B, the base 5906 can include first mounting holes 5924. As shown in FIG. 59C, the base 5906 can include second mounting holes 5925. The first mounting holes 5924 and the second mounting holes 5925 can be configured to accept mounting means, such as a screw, a bolt, a clip, a fastener, etc. In some illustrative embodiments, the mounting holes 5924 are threaded. For example, a helical insert can be used to provide threaded means for accepting a screw or bolt. In some illustrative embodiments, the helical insert can be made of brass, steel, stainless steel, aluminum, nylon, plastic, etc. For example, the threaded inserts can have #2-56 threads. In alternative embodiments, the threaded inserts can have any other suitable threads. The first mounting holes 5924 can be used to secure the side of the base 5906 with the first mounting holes 5924 against a base of the housing 5905 (e.g., the housing 4205 of FIG. 42A or the housing 4305 of FIG. 43 A). Thus, when the base 5906 is mounted to the housing via the first mounting holes 5924, light from the plurality of optical light sources (e.g., the optical excitation system 4210 of FIG. 42A) can be injected through the face side 5922 of the magneto- optical defect center material 5920. Similarly, when the base 5906 is mounted to the housing via the second mounting holes 5925, light from the plurality of optical light sources can be injected through the edge side 5921.

[0664] In some illustrative embodiments, the base 5906 can include slots 5930. The slots 5930 can be used to receive pegs or other inserts that are attached to the housing. In such

embodiments, the slots 5930 can be used to align the base 5906 with holes or fasteners associated with the first mounting holes 5924 or the second mounting holes 5925. Thus, the holder 5900 can easily and/or conveniently be rotated to optionally mount to the housing via either the first mounting holes 5924 or the second mounting holes 5925. In alternative embodiments, the holder 5900 can include additional sets of mounting holes. Also, although the embodiments shown in FIGS. 59A-59C include two holes in each set of the first mounting holes 5924 and the second mounting holes 5925, any other suitable number of mounting holes can be used.

[0665] FIG. 60 is a circuit outline of a radio frequency element circuit board in accordance with some illustrative embodiments. An illustrative example RF circuit board 6012 can include a positive electrode 6011, an RF signal trace 6014, and ground connectors 6013. The RF circuit board 6012 may correspond to the RF circuit board 5912 of FIG. 59A. In alternative

embodiments, additional, fewer, and/or different elements may be used. As shown in FIG. 59A, the RF circuit board 6012 can be attached to the base 5906. The RF circuit board 6012 can be attached to the base 5906 using any suitable method, such as via a glue, epoxy, screws, bolts, clips, fasteners, etc.

[0666] An RF field can be applied to the magneto-optical defect center material 5920 to determine the external magnetic field. In some illustrative embodiments, the RF signal connector 5915 can be configured to receive a connector or cable over which an RF signal is transmitted. For example, the RF signal connector 5915 can be configured to accept a coaxial cable. The positive electrical connection of the RF signal connector 5915 can be connected to the positive electrode 601 1. The positive electrode 6011 can, in turn, be electrically connected to the RF signal trace 6014. Similarly, the ground connection from the RF signal connector 5915 can be electrically connected to the ground connectors 6013. In some illustrative embodiments, the ground connectors 6013 are electrically connected to the base 5906, which can be connected to a ground of the system. Thus, an RF signal transmitted to the RF signal connector 5915 can be transmitted through the RF signal trace 6014, which can transmit an RF field. The RF field can be applied to the magneto-optical defect center material 5920. Thus, the signal transmitted to the RF signal connector 5915 can be used to apply the RF field to the magneto-optical defect center material 5920.

[0667] FIGS. 61 A and 61B are three-dimensional views of an element holder base in accordance with some illustrative embodiments. An illustrative base 6106 includes the first mounting holes 6124, the second mounting holes 6125, the slots 6130, an RF connector recess 6107, and a magneto-optical defect recess 6108. The base 6106, the first mounting holes 6124, the second mounting holes 6125, the slots 6130 may correspond to the base 5906, the first mounting holes 5924, the second mounting holes 5925, and the slots 5930, respectively, of FIG. 59A. In alternative embodiments, additional, fewer, and/or different elements may be used. [0668] In some illustrative embodiments, the base 5906, 6106 is made of a conductive material. For example, the base 5906, 6106 may be made of brass, steel, stainless steel, aluminum, etc.

[0669] The base 5906, 6106 can include an RF connector recess 6107 that can be configured to accept at least a portion of the RF signal connector 5915. Similarly, the magneto-optical defect recess 6108 can be configured to accept the magneto-optical defect center material 5920. For example, the NV diamond material 620 can be mounted to the magneto-optical defect recess 6108.

[0670] In some illustrative embodiments, the length L (e.g., from the edge of the base 6106 with the RF connector recess 6107 to the edge with the magneto-optical defect recess 6108, as shown by the dashed line) of the base 6106 is 0.877 inches long. In alternative embodiments, the length L can be less than or greater than 0.877 inches. In some illustrative embodiments, the width W is 0.4 inches. In alternative embodiments, the width W is less than or greater than 0.4 inches. In some illustrative embodiments, the height H is 0.195 inches. In alternative embodiments, the height H is less than or greater than 0.195 inches.

Vivaldi RF Antenna Array

[0671] A magneto-optical defect center sensor can utilize a Vivaldi antenna array for increasing uniformity of an RF magnetic signal at a specified location of the magneto-optical defect center material. FIG. 62 depicts an implementation of a Vivaldi or tapered slot antenna element 6200. In the implementation shown, a conductive layer 6221 is positioned on a substrate for the Vivaldi antenna element 6200. A slot 6202 is formed in the conductive layer 6221 that widens from a minimum distance 6204 at a first end 6206 of the slot 6202 to a maximum distance 6208 at a second end 6210. The opening of the slot 6202 is symmetrical in the implementation shown about an axis 6212 along the length of the slot 6202 and each side 6222, 6224 of the conductive layer 6221 widens outwardly as the slot 6202 approaches the second end 6210.

[0672] The Vivaldi antenna element 6200 can be constructed from a pair of symmetrical conductive layers 6221 on opposing sides of a thin substrate layer. The conductive layers 6221 are preferably substantially identical with the slot 6202 formed in each conductive layer 6221 pair being parallel. The Vivaldi antenna element 6200 is fed by a transmission line (not shown) at the first end 6206 and radiates from the second end 6210. The size, shape, configuration, and/or positioning of the transmission line of the Vivaldi antenna element 6200 may be modified for different bandwidths for the Vivaldi antenna element 6200.

[0673] As shown in FIG. 63, a plurality of Vivaldi antenna elements 6300 may be arranged in an array 6390. The array 6390 may include Vivaldi antenna elements 6300 in a two-dimensional configuration with Vivaldi antenna elements 6300 arranged horizontally 6312 and vertically 6311 in a plane of the array 6390. In some implementations, the Vivaldi antenna elements 6300 may be uniform in size and configuration. In other implementations, the Vivaldi antenna elements 6300 may have different sizes and/or configurations based on a position of the corresponding Vivaldi antenna element 6300 in the array 6390 and/or based on a target far-field uniformity for a magneto-optical defect center element positioned relative to the array 6390. In some implementations, the array 6390 of Vivaldi antenna elements 6300 is configured to be oversampled to operate over a frequency band centered at 2.87GHz. Each individual Vivaldi antenna element 6300 may be designed to operate from approximately 2 GHz to 40 GHz. The array 6390 may include 64 to 196 individual Vivaldi antenna elements 6300.

[0674] FIG. 64 depicts an RF system 6400 for use in a magneto-optical defect center sensor, such as the system 4200 of FIG. 42A. A magneto-optical defect center sensor may use an RF excitation method that has substantial uniformity over a portion of the magneto-optical defect center material 6420 (e.g., a NV diamond material) such as the magneto-optical defect center material 4220 that is illuminated by the optical excitation system 4210, such as the optical light source 421 OA and 4210B of FIG. 42 A. A spatially oversampled Vivaldi antenna array 6490, such as the array 6390 of FIG. 63, can be implemented to achieve a high uniformity in a compact size through the use of small Vivaldi antenna elements 6200, 6300 to permit the magneto-optical defect center material 6420 to effectively be in the far field of the array, thereby decreasing the distance needed between the magneto-optical defect center material 6420 and the array 6490.

[0675] As shown in FIG. 64, the RF system includes an RF generator 6402, a beam former system 6404, and the Vivaldi antenna element array 6490. The RF generator 6402 is configured to generate an RF signal for generating an RF magnetic field for the magneto-optical defect center sensor based on an output from the controller such as the controller 680 of FIGS. 6A-6C. Each Vivaldi antenna element 6200, 6300 of the array 6490 can be designed to work from 2 gigahertz (GHz) to 40 GHz. In some implementations, each Vivaldi antenna element 6200, 6300 of the array 6990 can be designed to work at other frequencies, such as 50 GHz. The Vivaldi antenna elements 6200, 6300 are positioned on an array lattice or other substructure correlating to 40 GHz. In some implementations, the array lattice may be a small size, such as 0.1 inches by 0.1 inches. Each Vivaldi antenna element 6200, 6300 of the array 6490 is electrically coupled to the beam former system 6404. The combination of the Vivaldi antenna elements 6200, 6300 permits the array 6490 to operate at lower frequencies than each Vivaldi antenna element 6200, 6300 making up the array 6490.

[0676] The beam former system 6404 is configured to spatially oversample the Vivaldi antenna elements 6400 of the array 6490 such that the array 6490 of Vivaldi antenna elements 6200, 6300 effectively operates like a single element at 2 GHz. The beam former system 6404 may include a circuit of several Wilkinson power splitters. In some implementations, the beam former system 6404 may be configured to spatially oversample the Vivaldi antenna elements 6200, 6300 of the array 6490 such that the array 6490 of Vivaldi antenna elements 6200, 6300 perform like a single element at other frequencies, such as 2.8-2.9 GHz. A single 2 GHz antenna would typically require an increased distance for the magneto-optical defect center material 6420 to be located in the far field. If the magneto-optical defect center material 6420 is moved into the near field, decreased uniformity occurs. However, since the array 6490 is composed of much smaller Vivaldi antenna elements 6200, 6300, the far field of each element 6200, 6300 is much closer than a single 2 GHz antenna. Thus, the magneto-optical defect center material 6420 is able to be positioned much closer to still be in the far field of the array 6490. Due to oversampling provided by the beam former system 6404 of the array 6490 of very small Vivaldi antenna elements 6200, 6300 the magneto-optical defect center material 6420 is able to be positioned in the far field of the array 6490 and achieve a high uniformity.

[0677] Because of the high uniformity for the RF magnetic field provided by the array 6490, the magneto-optical defect center material 6420 can be at multiple different orientations, thereby providing additional adaptability for designing the magneto-optical defect center sensor. That is, the magneto-optical defect center material 6420 may be mounted to a light pipe for collected red wavelength light emitted from the magneto-optical defect center material 6420 when excited by a green wavelength optical excitation source, and the array 6490 can be maneuvered to a number of different positions to accommodate any preferred configurations for the positioning of the light pipe and/or optical excitation source. By providing the array 6490 of Vivaldi antenna elements 6200, 6300, the magneto-optical defect center sensor can have a more customized and smaller configuration compared to other magneto-optical defect center sensors.

[0678] In addition, in some implementations, the array 6390, 6490 may be able to control the directionality of the generated RF magnetic field. That is, because of the several Vivaldi antenna elements 6300, 6400 making up the array 6390, 6490, the directionality of the resulting RF magnetic field can be modified based on which of the Vivaldi antenna elements 6200, 6300 are active and/or the magnitude of the transmission from each of the Vivaldi antenna elements 6200, 6300. In some implementations, one or more phase shifters may be positioned between a corresponding output of a beam former of the beam former system 6404 for a Vivaldi antenna element 6200, 6300. The one or more phase shifters may be selectively activated or deactivated to provide constructive or destructive interference so as to "steer" each RF magnetic field generated from each Vivaldi antenna element 6200, 6300 in a desired direction. Thus, in some implementations it may be possible to "steer" the generated RF magnetic field to one or more lattices of the magneto-optical defect center material 6420.

[0679] Some embodiments provide methods and systems for magneto-optical defect center sensors that utilize a Vivaldi antenna array for increasing uniformity of an RF magnetic signal at a specified location of the magneto-defect center element, such as a diamond having a nitrogen vacancy.

[0680] Some implementations relate to a magnetic field sensor assembly that may include an optical excitation source, a radio frequency (RF) generator, a beam former in electrical communication with the RF generator, an array of Vivaldi antenna elements in electrical communication with the beam former, and a magneto-optical defect center material positioned in a far field of the array of Vivaldi antenna elements. The array of Vivaldi antenna elements may generate a RF magnetic field that is uniform over the magneto-optical defect center material and the optical excitation source may transmit optical light at a first wavelength to the magneto- optical defect center material to detect a magnetic field based on a measurement of optical light at a second wavelength that is different from the first wavelength.

[0681] In some implementations, the array of Vivaldi antenna elements may be configured to operate in a range from 2 gigahertz (GHz) to 50 GHz. The array of Vivaldi antenna elements may include a plurality of Vivaldi antenna elements and an array lattice. The beam former may be configured to operate the array of Vivaldi antenna elements at 2 GHz or 2.8-2.9 GHz. The beam former may be configured to spatially oversample the array of Vivaldi antenna elements. The array of Vivaldi antenna elements may be adjacent the magneto-optical defect center material. The magneto-optical defect center material may be a diamond having nitrogen vacancies.

[0682] Some implementations relate to a magnetic field sensor assembly that may include a radio frequency (RF) generator, a beam former in electrical communication with the RF generator, an array of antenna elements in electrical communication with the beam former, and a magneto-optical defect center material positioned in a far field of the array of antenna elements. The array of antenna elements may generate a RF magnetic field that is uniform over the magneto-optical defect center material.

[0683] In some implementations, the array of antenna elements may be configured to operate in a range from 2 gigahertz (GHz) to 50 GHz. The array of antenna elements may include a plurality of Vivaldi antenna elements and an array lattice. The beam former may be configured to operate the array of antenna elements at 2 GHz or 2.8-2.9 GHz. The beam former may be configured to spatially oversample the array of antenna elements. The array of antenna elements may be adjacent the magneto-optical defect center material. The magneto-optical defect center material may be a diamond having nitrogen vacancies.

[0684] Other implementations relate to a magnetic field sensor assembly that may include a radio frequency (RF) generator, an array of antenna elements in electrical communication with the RF generator, and a magneto-optical defect center material positioned in a far field of the array of antenna elements. The array of antenna elements may generate a RF magnetic field that is uniform over the magneto-optical defect center material.

[0685] In some implementations, the array of antenna elements may be configured to operate in a range from 2 gigahertz (GHz) to 50 GHz. The magnetic field sensor assembly may include a beam former configured to operate the array of antenna elements at 2.8-2.9 GHz. The array of antenna elements may include a plurality of Vivaldi antenna elements and an array lattice.

Magnetic Field Generator

[0686] In the embodiment illustrated in FIG. 65, permanent magnets are mounted to the bias magnet ring 6525, which is secured within the magnet ring mount 6515. The bias magnet ring 6525 and the magnet ring mount 6515 may correspond to the bias magnet ring 4225 and the magnet ring mount 4215 of FIG. 42A. The magnet ring mount 6515 is mounted or fixed within the housing (e.g., the housing 4205 of FIG. 42A) such that the magnet ring mount 6515 does not move within the housing. Similarly, the plurality of optical light sources (e.g., the optical light sources 4210A and 421 OB of FIG. 42 A) are mounted within the housing such that the plurality of optical light sources do not move within the housing.

[0687] The magneto-optical defect center material (e.g., the magneto-optical defect center material 4220 of FIG. 42A) is mounted within the magnet ring mount 6515, but the plurality of optical light sources are mounted outside of the magnet ring mount 6515. The plurality of optical light sources transmit light to the magneto-optical defect center material which excites the defect centers, and light emitted from the defect centers is detected by the optical detector (e.g., the optical detector 4240 of FIG. 42 A). In some embodiments shown, the plurality of optical light sources transmit the light such that the magnet ring mount 6515 and the bias magnet ring 6525 do not interfere with the transmission of the light from the plurality of optical light sources to the NV diamond material.

[0688] The magnetic field generator (e.g., the magnetic field generator 670 of FIGS. 6A-6C) may generate magnetic fields with orthogonal polarizations, for example. In this regard, the magnetic field generator may include two or more magnetic field generators, such as two or more Helmholtz coils. The two or more magnetic field generators may be configured to provide a magnetic field having a predetermined direction, each of which provide a relatively uniform magnetic field at the magneto-optical defect center material. The predetermined directions may be orthogonal to one another. In addition, the two or more magnetic field generators of the magnetic field generator may be disposed at the same position, or may be separated from each other. In the case that the two or more magnetic field generators are separated from each other, the two or more magnetic field generators may be arranged in an array, such as a one- dimensional or two-dimensional array, for example.

[0689] The system (e.g., the system 4200 of FIG. 42A) may be arranged to include one or more optical detection systems, where each of the optical detection systems includes the optical detector, optical excitation source, and magneto-optical defect center material. Furthermore, the magnetic field generator may have a relatively high power as compared to the optical detection systems. In this way, the optical detection systems may be deployed in an environment that requires a relatively lower power for the optical detection systems, while the magnetic field generator may be deployed in an environment that has a relatively high power available for the magnetic field generator so as to apply a relatively strong magnetic field.

[0690] FIG. 65 illustrates a magnet mount assembly 6500 in accordance with some illustrative embodiments. The illustrative magnet mount assembly 6500 includes the magnet ring mount 6515 and the bias magnet ring 6525. In alternative embodiments, additional, fewer, and/or different elements may be used.

[0691] As shown in FIG. 65, the magnet ring mount 6515 includes a first portion 6616 and a second portion 6716 held together with fasteners 6518. The bias magnet ring 6525 can be fixed within the magnet ring mount 6515. The bias magnet ring 6525 can hold magnets such that a uniform or substantially uniform magnetic field is applied to a central portion of the magnet mount assembly 6500. For example, the uniform magnetic field can be applied to the magneto- optical defect center material.

[0692] The magnet mount assembly 6500 includes through-holes 6526. The through-holes 3026 can be sufficiently large to allow light from the plurality of optical light sources to pass into a center portion of the magnet mount assembly 6500 (e.g., to apply light to the magneto-optical defect center material). As noted above, the system may include any suitable number of optical light sources. Similarly, the magnet mount assembly 6500 may include any suitable number of through-holes 6526. In some illustrative embodiments, the magnet mount assembly 6500 incudes the same number of through-holes 6526 as a number of optical light sources in the system. In alternative embodiments, the magnet mount assembly 6500 includes a different number of through-holes 6526 than a number of optical light sources in the system. For example, two or more optical light sources may pass light through the same through-hole 6526. In another example, one or more through-holes 6526 may not have light passing therethrough.

[0693] The magnet mount assembly 6500 as shown in FIG. 65 includes six fasteners 6518. The fasteners 6518 can be used to secure the first portion 6616 to the second portion 6716. In some illustrative embodiments, the fasteners 6518 can be used to secure the magnet mount assembly 6500 to the housing of the system (e.g., the housing 4205 of FIG. 42A). The fasteners 6518 can be any suitable device for securing the first portion 6616 to the second portion 6716. In the embodiment shown in FIG. 65, the fasteners 6518 are screws. Other examples of fasteners 6518 may include bolts, studs, nuts, clips, etc. In alternative embodiments, any suitable means of securing the first portion 6616 and the second portion 6716 to one another, such as glue, welds, epoxy, etc. Although FIG. 65 shows six fasteners 6518 being used, any other suitable number can be used. For example, the magnet mount assembly 6500 may have one, two, three, five, ten, etc. fasteners 6518.

[0694] As shown in FIG. 65, the inside surface of the magnet ring mount 6515 is circular or semi -spherical and the outside surface is an octagonal prism. In such an embodiment, a center of the circular shape or semi-spherical shape of the inside surface is on a central axis of the octagonal prism of the outside surface. Any other suitable shapes may be used. For example, the inside surface of the magnet ring mount 6515 may be elliptical. In another example, the outside surface of the magnet ring mount 6515 may have more or fewer sides than eight.

[0695] In some illustrative embodiments, the inner diameter (e.g., the inner spherical diameter) of the magnet ring mount 6515 is 2.75 inches. In such an embodiment, the tolerance may be +0.002 inches and -0.000 inches. In alternative embodiments, the inner diameter of the magnet ring mount 6515 is greater than or less than 2.75 inches, and any suitable tolerance may be used.

[0696] As shown in FIG. 65, the bias magnet ring 6525 can include an outside ring that is circular. In some illustrative embodiments, the outside circumference of the bias magnet ring 6525 is the same or slightly less than the inside diameter of the magnet ring mount 6515. In such an embodiment, when not secured, the bias magnet ring 6525 can move freely within the magnet ring mount 6515. As discussed in greater detail below, the bias magnet ring 6525 can be secured in place inside of the magnet ring mount 6515 using, for example, set screws.

[0697] The magnet ring mount 6515 and the bias magnet ring 6525 may be made of any suitable material. In some illustrative embodiments, the magnet ring mount 6515 and the bias magnet ring 6525 are non-ferrous and/or non-magnetic. For example, the magnet ring mount 6515 and the bias magnet ring 6525 may be made of plastic (e.g., Black Noryl ® PPO™, polystyrene, polyphenylene ether, etc.), titanium (e.g., Grade 5, Ti 6A1-4V, etc.), aluminum (e.g., 6061-T6 per ASTM B209, may have a chemical conversion coating per military standard MIL- DTL-5541, etc.), etc. The fasteners 6518, the set screws, and any other component of the system may be made of the same or similar materials.

[0698] FIGS. 66 and 67 are illustrations of parts of a disassembled magnet ring mount in accordance with some illustrative embodiments. FIG. 66 is an illustration of the first portion 6616 of the magnet ring mount 6515, and FIG. 67 is an illustration of the second portion 6716 of a magnet ring mount 6615 (e.g., the magnet ring mount 6515 of FIG. 65). The first portion 6616 includes fastener holes 6606, and the second portion 6716 includes fastener holes 6706. In some illustrative embodiments, the fastener holes 6606 align with corresponding fastener holes 6706 to accept the fasteners 6518. The first portion 6616 includes a hole larger than the fastener holes 6606 above the fastener holes 6606 to accept a head of the fasteners 6518 (e.g., the head of a screw). For example, the fastener holes 6606 and the fastener holes 6706 may be 0.1 inches in diameter and may be suitable to accept fasteners 6518 that are #2-56 screws. In some illustrative embodiments, the fasteners 6518 screw into threaded holes in the housing or a surface secured to the housing (e.g., a circuit board). In alternative embodiments, any other suitable securing mechanism or arrangement may be used.

[0699] The first portion 6616 of the magnet ring mount 6515 includes a height 6741, a length 6742, and a width 6743. In some illustrative embodiments, the length 6742 can be as wide as the length 6742 is long. In some illustrative embodiments, the height 6741 is 0.475 inches, and the length 6742 and the length 6742 are 2.875 inches each. In alternative embodiments, any other suitable dimensions may be used.

[0700] The second portion 6716 of the magnet ring mount 6515 includes a height 6641, a length 6642, and a width 6643. In some illustrative embodiments, the width 6643 can be as wide as the length 6642 is long. In the embodiments shown in FIGS. 66 and 67, the height 6741 is the same as the height 6641, the length 6742 is the same as the length 6642, and the length 6742 is the same as the width 6643. In some such embodiments, the height 6641 is 0.475 inches, and the width 6643 and the length 6642 are 2.875 inches each. In such an embodiment, the inside surface 6660 and the inside surface 6760 are matching but opposite portions of a sphere. That is, the circle at which the inside surface 6660 and the inside surface 6760 meet is a circumference of a sphere, and the inside surface 6660 and the inside surface 6760 are along the sphere. In alternative embodiments, any other suitable dimensions may be used.

[0701] FIG. 68 is an illustration of a magnet ring mount showing locations of magnets in accordance with some illustrative embodiments. FIG. 68 includes a magnet ring mount 6815 (e.g., the magnet ring mount 6515 of FIG. 65) and magnets 6805. In FIG. 68, six sets of three magnets 6805 are shown. Each magnet 6805 in a set is arranged in the same direction (e.g., the poles of each magnet 6805 are pointed in the same direction). In alternative embodiments, additional, fewer, and/or different elements may be used. For example, in alternative embodiments, each set of magnets 6805 may include greater than or fewer than three magnets 6805. Similarly, the total number of magnets 6805 may be greater than or fewer than eighteen.

[0702] FIG. 68 shows the arrangement of the magnets 6805 within the magnet ring mount 6815 without the bias magnet ring. Although the bias magnet ring is not shown, the bias magnet ring may hold the magnets 6805 in the same position relative to one another. But, the bias magnet ring may move within the magnet ring mount 6815 while maintaining the magnets 6805 in the same position relative to one another. Accordingly, the magnets 6805 may be rotated around the center portion of the bias magnet ring and/or the magnet ring mount 6815 (e.g., around the magneto-optical defect center material). For reference, a detailed discussion of diamond axes crystal alignment and magnet orientation is provided in U.S. Patent Application No. 15/003,718 (now U.S. Patent No. 9,541,610) and U.S. Patent Application No. 15/003,704, both filed on January 21, 2016, and both of which are incorporated herein by reference in their entireties.

[0703] FIGS. 69 and 70 are illustrations of a bias magnet ring mount in accordance with some illustrative embodiments. The bias magnet ring mount 6915 includes magnet holders 6905 with magnet holes 6910 and securing tabs 6916 with set screw holes 6920. In alternative

embodiments, additional, fewer, and/or different elements may be used.

[0704] As shown in FIGS. 69 and 70, the bias magnet ring mount 6915 has an outer ring, and the magnet holders 6905 and the securing tabs 6916 are fixed to the outer ring. In some illustrative embodiments, the outside diameter 6952 of the outer ring and the bias magnet ring mount 6915 is 2.745 inches. The height 6951 of the magnet holders 6905 can be 0.290 inches. In some illustrative embodiments, the outside surface of the outer ring is spherically shaped to fit within and slide along the inner surface 6911 and the inner surface 6911.

[0705] As noted above, the magnet holders have magnet holes. The magnet holes 6910 may hold the magnets 6805 in the orientation to one another shown in FIG. 68. The securing tabs 6916 may each include one or more set screw holes 6920. The set screw holes 6920 may be configured to receive a set screw. For example, the set screw holes 6920 may be threaded. In some illustrative embodiments, set screws may be threaded into the set screw holes 6920 and be pressed against the inner surface 6911 and/or the inner surface 6911 to secure the bias magnet ring mount 6915 within the magnet ring mount 6915. In some illustrative embodiments, the set screws 6920 may be #2-56 screws. In alternative embodiments, any other suitable set screws may be used.

[0706] In the embodiment shown in FIG. 70, two of the securing tabs 7015 each include one set screw hole 7020 and six through-holes 7005. Each of the six through-holes 7005 can be used to drill or otherwise form the magnet holes 7010. For example, each of the through-holes 7005 may be aligned along a same central axis as a corresponding magnet hole 7010. For example, the inside diameter of the magnet holes 7010 can be 0.070 inches. The inside diameter of the through-holes 7005 can be the same or larger than the inside diameter of the magnet holes 7010. Following the example, the inside diameter of the through-holes 7005 may be 0.070 inches (or larger). In alternative embodiments, any other suitable inside diameters may be used.

[0707] Thus, the magnet mount assembly 6500 can be used to adjust the magnetic bias applied to the magneto-optical defect center material by moving the magnets 6805 about the magneto- optical defect center material. Similarly, once a desired position is selected, the bias magnet ring mount 6515 may be secured within the magnet ring mount 6515.

[0708] As noted above with respect to FIGS. 4A and 4B, each of the dips (e.g., Lorentzians) in the graphs may correspond to one or more axes of the defect centers within the NV diamond material 620. The bias magnetic field applied to the magneto-optical defect center material may adjust the order and orientation of the Lorentzian dips in the graphs. Accordingly, there are forty-eight unique orientations of the Lorentzians such that each Lorentzian is distinguishable from the others (e.g., as in the graph of FIG. 4B). Thus, there are forty-eight unique positions of the magnets 6805 around the magneto-optical defect center material corresponding to each of the forty-eight orientations of the Lorentzians.

[0709] In some illustrative embodiments, the magnet ring mount 6515 is movable within the bias magnet ring 6525 and the housing such that twelve of the forty-eight positions of the magnets 6805 are accessible. That is, the magnet ring mount 6515 cannot be positioned into all of the forty-eight positions because the magnet ring mount 6515 would interfere with the housing, which may span across the top and bottom of the magnet ring mount 6515. In some instances, only a portion of the twelve positions may position the bias magnet ring 6525 within the magnet ring mount 6515 such that the bias magnet ring 6525 does not interfere with the light that passes through the through-holes 6526. In some illustrative embodiments, the bias magnet ring 6525 is positioned such that the Lorentzians are distinguishable from one another and such that the light is not interfered with as it passes through the through-hole to the magneto-optical defect center material.

Magneto-optical Defect Center with Waveguide Implementation

[0710] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented having a magneto-optical defect center material with a waveguide.

[0711] In various embodiments described herein, the material with the defect centers may be formed in a shape that directs light from the defect centers towards the photo diode. When excited by the green light photon, a defect center emits a red light photon. But, the direction that the red light photon is emitted from the defect center is not necessarily the direction that the green light photon was received. Rather, the red light photon can be emitted in any direction. When the red photon reaches the interface between the diamond and the surrounding medium, the photon may transmit through the interface or reflect back into the diamond, depending, in part, on the angle of incidence at the interface. The phenomenon by which the photon may reflect back into the diamond is referred to as total internal reflection (TIR). Thus, the sides of the diamond can be angled and polished to reflect red light photons towards the photo sensor.

[0712] FIG. 71 illustrates a magneto-optical defect center material 7120 with a defect center 7115 and an optical detector 7140. In an illustrative embodiment, the magneto-optical defect center material 7120 is a diamond material, and the defect center 7115 is an NV center. In alternative embodiments, any suitable magneto-optical defect center material 7120 and defect center 7115 can be used. An excitation photon travels along path 7105, enters the material 7120 and excites the defect center 7115. The excited defect center 7115 emits a photon, which can be in any direction. Paths 7110, 7111, 7112, 7113, and 7114 are example paths that the emitted photon may travel. In the embodiments of FIG. 71, one defect center 7115 is shown for illustrative purposes. However, in alternative embodiments, the material may include multiple defect centers 7115. Also, the angles and specific paths in FIG. 71 are meant to be illustrative only and not meant to be limiting. In alternative embodiments, additional, fewer, and/or different elements may be used.

[0713] In the embodiments illustrated in FIG. 71, there is no object between the material 7120 and the optical detector 7140. Thus, air or a vacuum is between the material 7120 and the optical detector 7140. The air or vacuum surrounds the material 7120. In alternative embodiments, objects such as waveguides may be between the material 7120 and the optical detector 7140. Regardless of whether an object is between the material 7120 and the optical detector 7140, the refractive index of the material is different than the refractive index of whatever is between the material 7120 and the optical detector 7140.

[0714] In the embodiments shown in FIG. 71 in which the same material (e.g., air or a vacuum) surrounds the material 7120 on all sides and has a different refractive index than the material 7120, the path of the emitted light may change direction at the interface between the material 7120 and the surrounding material depending upon the angle of incidence and the differences in the refractive indexes. In some instances, depending upon the differences in the refractive indexes, the angle of incidence, and the surface of the interface (e.g., smooth or rough), the photon may reflect off of the surface of the material 7120. In general, as the angle of incidence becomes more orthogonal, as the differences in the refractive indexes gets closer to zero, and as the surface of the interface is more rough, the higher the chance that the emitted photon will pass through the interface rather than reflect off of the interface. In the examples of FIG. 71, all of paths 7110, 7111, 7112, 7113, and 7114 travel through the interface (i.e., a side surface of the material 7120). However, in other instances, the photon may reflect off of one or more surfaces of the material 7120 before passing through the interface. Because the emitted photon can be emitted in any three-dimensional direction, only a small fraction of the possible beam paths exit the surface of the material 7120 facing the optical detector 7140.

[0715] FIG. 72A is a diagram illustrating possible paths of light emitted from a material with defect centers and a rectangular waveguide in accordance with some illustrative embodiments. FIG. 72A illustrates a material 7220 with a defect center 7215 and an optical detector 7240. In an illustrative embodiment, the magneto-optical defect center material 7220 is a diamond material, and the defect center 7215 is an NV center. In alternative embodiments, any suitable magneto-optical defect center material 7220 and defect center 7215 can be used. Attached to the material 7220 is a waveguide 7322. An excitation photon travels along path 7205, enters the material 7220 and excites the defect center 7215. The excited defect center 7215 emits a photon, which can be in any direction. Paths 7210, 7211, 7212, 7213, and 7214 are example paths that the emitted photon may travel. In the embodiments of FIG. 72A, one defect center 7215 is shown for illustrative purposes. However, in alternative embodiments, the material may include multiple defect centers 7215. Also, the angles and specific paths in FIG. 72 are meant to be illustrative only and not meant to be limiting. FIG. 72B is a three-dimensional view of the material and rectangular waveguide of FIG. 72 A in accordance with an illustrative embodiment. As shown in FIG. 72B, the material 7220 and the waveguide 7222 are a cuboid. In alternative embodiments, additional, fewer, and/or different elements may be used.

[0716] The embodiments shown in FIG. 72A includes a waveguide 7222 attached to the material 7220. In an illustrative embodiment, the waveguide 7222 is a diamond, and there is no difference in refractive indexes between the waveguide 7222 and the material 7220. In alternative embodiments, the waveguide 7222 may be of any material with the same or similar refractive index as the material 7220. Because there is little or no difference in refractive indexes, light passing through the interface 7224 does not bounce back into the material 7220 or change velocity (e.g., including direction). Accordingly, because light passes freely through the interface 7224, more light is emitted from the material 7220 toward the optical detector 7240 than in the embodiments of FIG. 71. That is, light emitted in a direction toward a side of the material 7220 that is not the interface 7224 may bounce back into the material 7220 depending upon the angle of incidence, etc., as described above. Such light, therefore, has a chance to be bounced into the direction of the interface 7224 and toward the optical detector 7240. In general, light (e.g., via path 7212) that contacts a sidewall of the waveguide 7222 will be reflected back into the waveguide 7222 as opposed to transitioning outside of the waveguide 7222 because of the angle of incidence. That is, such light will generally have a low angle of incidence, thereby increasing the chance that the light will bounce back into the waveguide 7222. Similarly, light that hits the end face of the waveguide 7222 (i.e., the face of the waveguide 7222 facing the optical detector 7240) will generally have a high angle of incidence, and, therefore, a higher chance of passing through the end of the waveguide 7222 and pass onto the surface of the optical detector.

[0717] In some illustrative embodiments, the material 7220 includes NV centers, but the waveguide 7222 does not include NV centers. Light emitted from an NV center can be used to excite another NV center. The excited NV center emits light in any direction. Accordingly, if the waveguide 7222 includes NV centers, light that passed through the interface 7224 may excite an NV center in the waveguide 7222, and the NV center may emit light back towards the material 7220 or in a direction that would allow the light to pass through a side surface of the waveguide 7222 (e.g., as opposed to the end face of the waveguide 7222 and toward the optical detector 7240). In some instances, light may be absorbed by defects that are not NV centers, and such defects may not emit a corresponding light. In such instances, the light is not transmitted to a light sensor.

[0718] Accordingly, efficiency of the waveguide 7222 is increased when the waveguide 7222 does not include nitrogen vacancies. In this context, efficiency of the system is determined by the amount of light that is emitted from the defect centers compared to the amount of light that is detected the optical detector 7240. That is, in a system with 100% efficiency, the same amount of light that is emitted by the defect centers passes through the end face of the waveguide 7222 and is detected by the optical detector 7240. In an illustrative embodiment, a system with the waveguide 7222 that has nitrogen vacancies has a mean efficiency of about 4.5%, whereas a system with the waveguide 7222 that does not have nitrogen vacancies has a mean efficiency of about 6.1%.

[0719] FIG. 73 A is a diagram illustrating possible paths of light emitted from a material with defect centers and an angled waveguide in accordance with some illustrative embodiments. FIG. 73 A illustrates a material 7320 with a defect center 7315 and an optical detector 7340. In an illustrative embodiment, the magneto-optical defect center material 7320 is a diamond material, and the defect center 7315 is an NV center. In alternative embodiments, any suitable magneto- optical defect center material 7320 and defect center 7315 can be used. The material 7320 with the waveguide 7322 has a higher efficiency than the embodiments of FIG. 72. In an illustrative embodiment with a diamond and waveguide similar to the material 7320 and the waveguide 7322 of FIG. 73, the system has a mean efficiency of about 9.8%.

[0720] In an illustrative embodiment, the shape of the material 7320 and the waveguide 7322 in FIG. 73A is two-dimensional. That is, the surfaces of the material 7320 and the waveguide 7322 that are orthogonal to the viewing direction of FIG. 73 are flat with each side in a plane that is parallel to one another, and each side spaced from one another. FIG. 73B is a three- dimensional view of the material and angular waveguide of FIG. 73 A in accordance with an illustrative embodiment.

[0721] As shown in FIG. 73 A, the material 7320 and the waveguide 7322 are defined, in one plane, by sides 7351, 7352, 7353, 7354, 7355, and 7356. The angles between sides 7351 and 7352, between sides 7352 and 7353, between sides 7353 and 7354, and between sides 7356 and 7351 are obtuse angles (i.e., greater than 90°). The angles between sides 7354 and 7355 and between sides 7355 and 7356 are right angles (i.e., 90°). The material 7320 with nitrogen vacancies does not extend to sides 7354, 7355, and 7356. In alternative embodiments, any suitable shape can be used. For example, the waveguide can include a compound parabolic concentrator (CPC). In another example, the waveguide can approximate a CPC.

[0722] FIG. 74A is a diagram illustrating possible paths of light emitted from a material with defect centers and a three-dimensional waveguide in accordance with some illustrative embodiments. FIG. 74A illustrates a material 7420 with a defect center 7415 and an optical detector 7440. In an illustrative embodiment, the magneto-optical defect center material 7420 is a diamond material, and the defect center 7415 is an NV center. In alternative embodiments, any suitable magneto-optical defect center material 7420 and defect center 7415 can be used.

Attached to the material 7420 is a waveguide 7422. An excitation photon travels along path 7405, enters the material 7420, and excites the defect center 7415. The excited defect center 7415 emits a photon, which can be in any direction. Paths 7410, 7411, 7412, and 7413 are example paths that the emitted photon may travel. In the embodiments of FIG. 74, one defect center 7415 is shown for illustrative purposes. However, in alternative embodiments, the material may include multiple defect centers 7415. Also, the angles and specific paths in FIG. 74 are meant to be illustrative only and not meant to be limiting. In alternative embodiments, additional, fewer, and/or different elements may be used.

[0723] In an illustrative embodiment, the material 7420 includes defect centers, and the waveguide 7422 is made of diamond but does not include defect centers. In an illustrative embodiment, the angles formed by sides 7455 and 7456 and by sides 7456 and 7457 are right angles, and the other angles formed by the other sides are obtuse angles. In an illustrative embodiment, the cross-sectional shape of the material 7420 and the waveguide 7422 of FIG. 74 A is the shape of the material 7420 and the waveguide 7422 in two, orthogonal planes. That is, the material 7420 and the waveguide 7422 have one side 7452, one side 7456, two sides 7451, two sides 7453, two sides 7454, two sides 7455, two sides 7457, and two sides 7458. The three- dimensional aspect can be seen in FIG. 74B.

[0724] FIGS. 74C-74F are two-dimensional cross-sectional drawings of a three-dimensional waveguide in accordance with some illustrative embodiments. The three-dimensional waveguide in FIGS. 74C-74F can be the same waveguide as in FIGS. 74A and/or 74B.

Dimensions 7461, 7462, 7463, 7464, 7465, 7466, 7467, 7468, 7469, and 7470 are provided as illustrative measurements in accordance with some embodiments. In alternative embodiments, any other suitable dimensions may be used. In an illustrative embodiment, the dimension 7461 is 2.81 mm, the dimension 7462 is 2.00 mm, the dimension 7463 is 0.60 mm, the dimension 7464 is 1.00 mm, the dimension 7465 is 3.00 mm, the dimension 7466 is 0.50 mm, the dimension 7467 is 1.17 mm, the dimension 7468 is 2.0 mm, the dimension 7469 is 0.60, and the dimension 7470 is 1.75 mm.

[0725] In an illustrative embodiment, the three-dimensional material 7420 and waveguide 7422 of the system of FIGS. 74A-74F had a mean efficiency of 55.1%. The shape of the configuration of FIGS. 74A and 74B can be created using diamond shaping and polishing techniques. In some instances, the shapes of FIGS. 74A-74F can be more difficult (e.g., more steps, more sides, etc.) than other configurations (e.g., those of FIGS. 72A, 72B, 73 A, and 73B). As explained above, the material and the waveguide of the configurations of FIGS. 72A, 72B, 73 A, 73B, and 74A- 74F include the material with the defect centers and the material without the defect centers (i.e., the waveguide). In some embodiments, the material with the defect centers is synthesized via any suitable method (e.g., chemical vapor deposition), and the waveguide is synthesized onto the material with the defect centers. In alternative embodiments, the material with the defect centers is synthesized onto the waveguide.

[0726] In alternative embodiments, the material and the waveguide can be synthesized (or otherwise formed) independently and attached after synthesis. For example, FIG. 75 is a diagram illustrating a material attached to a waveguide in accordance with some illustrative embodiments. The material 7520 can be fused to the waveguide 7522. In an illustrative embodiment, the material 7520 and the waveguide 7522 are fused together using optical contact bonding. In alternative embodiments, any suitable method can be used to fuse the material 7520 and the waveguide 7522.

[0727] In an illustrative embodiment, the refractive index of the material 7520 and the waveguide 7522 are the same. Accordingly, as discussed above, more of the light that is emitted from the defect centers is directed towards the optical detector 7540 with the waveguide 7522 than without.

[0728] In an illustrative embodiment, because the waveguide 7522 is synthesized separately from the material 7520, the waveguide 7522 can be manufactured into any suitable shape. In the embodiments shown in FIG. 75, the waveguide 7522 is a paraboloid. For example, the waveguide 7522 can be a compound parabolic concentrator. In an illustrative embodiment, the material 7520 is a cube. In such an embodiment, the length of the diagonal of one of the sides is the same as the length of the diameter of the paraboloid at the end of the waveguide 7522 attached to the material 7520. In alternative embodiments, any other suitable shape can be used, such as any of the shapes shown in FIGS. 72A, 72B, 73 A, 73B, and 74A-74F.

[0729] In the embodiments of FIGS. 71, 72A, 73 A, and 74A, the light used to excite the corresponding defect centers is orthogonal to the respective side of the material that the light enters. In some instances, light entering the material through the interface at an orthogonal angle is the most efficient direction to get the light into the material. In other instances, a larger incidence angle may be more efficient than an orthogonal angle, depending upon the polarization of the light with respect to the surface orientation. In alternative embodiments, the light can enter the material at any suitable angle, even if at a less efficient angle. For example, the angle of the light entering the material can be parallel to a plane of the respective optical detector (e.g., as in FIG. 71). Such an angle can be chosen based on, for example, a configuration of a magnetometer system (e.g., a DNV system) or other system constraints.

[0730] FIG. 76 is a flow chart of a method of forming a material with a waveguide in accordance with an illustrative embodiment. In alternative embodiments, additional, fewer, and/or different operations may be performed. Also, the use of a flow chart and/or arrows is not meant to be limiting with respect to the order or flow of operations. For example, in alternative embodiments, two or more operations may be performed simultaneously.

[0731] In an operation 7605, a material with defect centers is synthesized. For example, the material can be a diamond material, and the defect centers can be NV centers. In an illustrative embodiment, chemical vapor deposition can be used to create the material with defect centers. In alternative embodiments, any suitable method for synthesizing the material with defect centers can be used.

[0732] In an operation 7610, a waveguide is synthesized. For example, the waveguide can be the same material as the material with the defect centers but without the defect centers (e.g., diamond material without NV centers or other defect centers). In an illustrative embodiment, chemical vapor deposition is used to synthesize the waveguide onto the material with defect centers. For example, chemical vapor deposition can be used to form the material in the operation 7605 in the presence of nitrogen or other element or material, and the waveguide can be synthesized by continuing to deposit carbon on the material but without the nitrogen or other element or material.

[0733] In an operation 7615, the material and waveguide can be cut and polished. For example, the material and waveguide can be cut and polished into one of the shapes shown in FIGS. 72A, 72B, 73 A, 73B, 74A-74F. In an illustrative embodiment, after the material and waveguide is cut and polished, the material and waveguide can be used in a magnetometer such as a DNV sensor.

[0734] FIG. 77 is a flow chart of a method of forming a material with a waveguide in accordance with some illustrative embodiments. In alternative embodiments, additional, fewer, and/or different operations may be performed. Also, the use of a flow chart and/or arrows is not meant to be limiting with respect to the order or flow of operations. For example, in alternative embodiments, two or more operations may be performed simultaneously.

[0735] In an operation 7705, a material with defect centers is synthesized. In an illustrative embodiment, the material is diamond and the defect centers are NV centers. For example, a material can be formed using chemical vapor deposition in the presence of nitrogen or other defect material, thereby forming a material with defect centers. In alternative embodiments, any suitable method can be used to create a material with defect centers. In an operation 7710, the material with defect centers is cut and polished. The material with defect centers can be cut into any suitable shape, such as a cube, a cuboid, etc.

[0736] In an operation 7715, a waveguide is synthesized. For example, a material without defect centers can be formed using any suitable method, such as chemical vapor deposition. In an operation 7720, the waveguide can be cut and polished. For example, the waveguide can be cut into the shape of the waveguide 7222 of FIGS. 72A and 72B, the waveguide 7322 of FIGS. 73A and 73B, the waveguide 7422 of FIGS. 74A-74F, or the waveguide 7522 of FIG. 75. In alternative embodiments, the waveguide can be cut into any suitable shape.

[0737] In an operation 7725, the material with the defect centers is fused to the waveguide. For example, optical contact bonding can be used to fuse the material with the defect centers with the waveguide. In alternative embodiments, an adhesive or other suitable bonding agent can be used to attach the material with the defect centers to the waveguide. In such

embodiments, the substance used to fix the material with the defect centers to the waveguide can have a refractive index that is the same as or similar to the refractive index of the material. In an illustrative embodiment, after the material and waveguide are fixed together, the material and waveguide can be used in a magnetometer such as a DNV sensor.

Drift Error Compensation Implementation

[0738] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented with methods for drift error compensation.

[0739] Measurement errors due to vertical and horizontal fluctuations in fluorescence intensity caused by internal and external effects of the system (e.g., optical excitation, thermal and/or strain effects) may be addressed in a magnetic detection system including multi-RF excitation. Fluorescence intensity measurements may be obtained at resonant frequencies associated with the positive and negative maximum (including greatest and near greatest) slope points of a response curve of an NV center orientation and spin state (ms = +1) to account for vertical drift error. In addition, fluorescence intensity measurements may be obtained at resonant frequencies associated with the positive and/or negative maximum (including greatest and near greatest) slope points of the response curves of an NV center orientation at both spin states (ms = +1 and ms = -1) to account for horizontal drift error. By compensating for such errors, the system may realize increased sensitivity and stability when calculating an external magnetic field acting on the system. In certain embodiments, guard intervals, in the form of multi-pulse sets of RF excitation at a given resonant frequency, and/or guard pulses, in the form of initial pulses used to stabilize the system without providing measurement data, may also be utilized during the collection process to allow for sufficient repolarization of the system when switching between resonant frequencies. Such guard intervals and/or guard pulses may ensure that residual effects due to previous measurement collections are reduced or eliminated. Among other things, this allows the system to forego the use of high-powered optical excitation for repolarization, thus improving sensor performance and cost.

[0740] As shown in FIGS. 6A-6C, the controller 680 controls the operation of the optical excitation source 610, the RF excitation source 630, and the magnetic field generator 670 to perform Optically Detected Magnetic Resonance (ODMR). Specifically, the magnetic field generator 670 may be used to apply a bias magnetic field that sufficiently separates the intensity responses for each of the four NV center orientations. The controller 680 then controls the optical excitation source 610 to provide optical excitation to the NV diamond material 620 and the RF excitation source 630 to provide RF excitation to the NV diamond material 620. The resulting fluorescence intensity responses for each of the NV axes are collected over time to determine the components of the external magnetic field Bz aligned along directions of the four NV center orientations of the NV diamond material 620, which may then be used to calculate the estimated vector magnetic field acting on the system 600. The excitation scheme utilized during the measurement collection process (i.e., the applied optical excitation and the applied RF excitation) may be any appropriate excitation scheme. For example, the excitation scheme may utilize continuous wave (CW) magnetometry, pulsed magnetometry, and variations on CW and pulsed magnetometry (e.g., pulsed RF excitation with CW optical excitation). In cases where Ramsey pulse RF sequences are used, pulse parameters π and τ may be optimized using Rabi analysis and FID-Tau sweeps prior to the collection process, as described in, for example, U.S. Patent Application No. 15/003,590.

[0741] During the measurement collection process, fluctuations may occur in the measured intensity response due to effects caused by components of the system 600, rather than due to true changes in the external magnetic field. For example, prolonged optical excitation of the NV diamond material by the optical excitation source 610 may cause vertical (e.g., red

photoluminescence intensity) fluctuations, or vertical drift, in the intensity response, causing the response curve to shift upward or downward over time. In addition, thermal effects within the system 600 may result in horizontal (e.g., frequency) fluctuations, or horizontal drift, in the measured intensity response, causing the response curve to translate left or right over time.

[0742] In some systems, the excitation scheme is configured such that the measurement collection process occurs at a single resonant frequency associated with a given spin state (e.g., ms = +1) of an NV center orientation. This resonant frequency may be either the frequency associated with the positive maximum slope point or the frequency associated with the negative maximum slope point of the response curve. Intensity response changes that occur at the particular frequency are tracked and used to determine changes in the external magnetic field Bz. However, because these measurement techniques utilize data at only a single point of the response curve (e.g., the positive maximum slope point or the negative maximum slope point), it can be difficult to account for those changes in the intensity response that are not due to the external magnetic field Bz, but are rather due to internal or external system effects. For example, when only a single RF frequency is tracked for measurement purposes, vertical drift due to prolonged optical excitation and horizontal drift due to thermal effects may be perceived as changes in the external magnetic field Bz, thus introducing error into the estimated vector magnetic field. Thus, compensation for these internal errors during the measurement collection process is desirable to maximize sensitivity and stability of the magnetic detection system 600.

[0743] FIG. 78A illustrates one example of a reduced fluorescence intensity response associated with a particular NV axis orientation and a first spin state (e.g., ms = +1). The graph shown in FIG. 78A is a zoomed-in view of the signal of interest (e.g., the particular NV axis orientation at the first spin state) via an offset and gain within the optical detector 640 and related circuitry of the system 600. As shown in FIG. 78A, the intensity response curve for the given spin state includes two maximum (including greatest and near greatest) slope points, a positive maximum (including greatest and near greatest) slope point 7812A and a negative maximum (including greatest and near greatest) slope point 7812B.

[0744] To compensate for vertical drift error, data is collected on both the positive maximum slope point 7812A and the negative maximum slope point 7812B during a collection process for a given magnetometry response curve. In some embodiments, however, data may be collected on a positive slope point 7812A and a negative slope point 7812B that is the average between the positive maximum slope and the negative maximum slope for a given response curve to allow for faster switching between relative frequencies during measurement collection.

[0745] By collecting data on both the positive slope point 7812A and the negative slope point 7812B for a response curve, changes due to vertical drift may be detected and accounted for during the external magnetic field calculation process. For example, if a shift in the response curve is due to a true change in the external magnetic field, the intensity response associated with the slope point 7812A and the intensity response associated with the slope point 7812B should shift in opposite directions (e.g., the intensity response associated with the slope point 7812A increases, while the intensity response associated with the slope point 7812B decreases, or vice versa). On the other hand, if a shift in the response curve is due to internal system factors that may cause vertical fluctuations, the intensity response associated with the slope points 7812A, 7812B should shift in equal directions (e.g., the intensity responses for slope points 7812A, 7812B both increase). Thus, by determining the relative shift in intensity response of slope points 7812A, 7812B of the response curve, error due to vertical drift may be detected. The resulting intensity measurements of the positive slope point 7812A and the negative slope point 7812B are then subtracted and divided by the difference of the slopes 7812A, 7812B (i.e., positive slope 7812A - negative slope 7812B « 2*positive slope 7812A), allowing for compensation of vertical fluctuations associated with vertical drift. In some embodiments, the vertical compensation process provides similar sensitivity as compared to a single RF frequency data collection process, described above, but reduces the bandwidth of the collection process by a factor of two.

[0746] FIG. 78B illustrates the reduced fluorescence intensity response associated with the same NV axis orientation shown in FIG. 78A and a second spin state (e.g., ms = -1), which is opposite to the first spin state. Like FIG. 78A, FIG. 78B shows a zoomed-in view of the signal of interest (e.g., the particular NV axis orientation at the second spin state) via an offset and gain within the optical detector 640 and related circuitry of the system 600. Similar to the vertical drift compensation process, horizontal drift may be compensated by performing data collection on two different slope points. In this case, data is collected on a first slope point associated with the first spin state shown in FIG. 78A and a second slope point associated with the second spin state shown in FIG. 78B. The first slope point and the second slope point may be selected independently of each other. For example, in some embodiments, the first slope point and the second slope point have equal signs (i.e., positive slope points 7812A, 7812A' or negative slope points 7812B, 7812B'). In other embodiments, however, the first slope point and the second slope point may have opposite signs (e.g., slope points 7812A, 7812B' or slope points 7812B, 7812A'). By collecting measurement data associated with maximum slope points of the two spin states of a given NV axis orientation, horizontal drift error may be estimated and accounted for in magnetic field calculations. For example, if a shift in the intensity response is due to changes in the external magnetic field acting on the system 600, the response curves associated with each of the spin states should shift relative to one another (i.e., either outward or inward relative to the zero splitting frequency). If, on the other hand, a shift in the intensity response is due to thermal effects within the system 600, the response curves associated with each of the spin states translate. Thus, like vertical drift compensation, horizontal shifts due to internal thermal effects may be determined and compensated during the collection process.

[0747] In certain embodiments, the measurement collection process may include both vertical drift error compensation and horizontal drift error compensation by switching between frequencies associated with the positive and negative slopes of a response curve for the first spin state and a frequency associated with a slope point of a response curve for the second spin state of an NV center orientation, allowing for magnetometry calculations that account for both vertical drift and horizontal drift due to internal components of the system 600. In addition, while processing for the compensation of vertical drift and/or horizontal drift may occur at the relative fluorescence intensity level, as described above, error due to both effects may be compensated during processing associated with the external magnetic field Bz estimation.

[0748] When switching between frequencies of a given NV center orientation and/or spin state, fluorescence dimming from a previous frequency may impact the measurement data collected on a subsequent frequency. Optical excitation power is often increased to reduce the time required to allow the system to repolarize to mitigate this effect. However, such a solution increases costs in terms of sensor SWAP, RF power, thermal stability, sensor complexity, and achievable sensitivity. As such, to ensure sufficient repolarization of the system 600 when shifting measurement collection to a different frequency without significantly increasing the costs associated with the system 600, guard intervals and/or guard pulses may be utilized during the measurement collection process, as shown in FIGS. 79A-79C. By utilizing guard intervals and/or pulses between measurement collections at different frequencies, measurement information from a given NV center orientation or spin state impacting the measurement of subsequent orientations and/or spin states due to residual dimming may be avoided. Moreover, because guard intervals/pulses reduce the effective sensor level duty cycle, multi-pulse coherent integration schemes may be used to further optimize magnetometry performance.

[0749] FIG. 79A shows one example of a measurement collection scheme in which error due to vertical drift is compensated through alternating single pulse intervals of data collection 7920 on a first slope point (e.g., positive slope point 7812A) of a response curve (indicated by solid lines) and data collection 7925 on the second slope point (e.g., negative slope point 7812B) of the response curve (indicated by dashed lines). In this case, a faster net sample rate may be achieved through constant switching between the two slope points 7920, 7925. The

measurement collection scheme shown in FIG. 79A may be similarly applied for RF schemes utilizing horizontal drift error compensation.

[0750] In certain embodiments, to further reduce the impact of residual noise, longer data collection intervals may be used, such as the measurement collection scheme shown in FIGS. 79B and 79C. As shown in FIG. 79B, error due to vertical drift is compensated through alternating multi-pulse data collection interval 7930a-7930e on the first slope point (e.g., positive slope point 7812A) of the response curve (indicated by solid lines) and multi-pulse data collection interval 7935a-7935e on the second slope point (e.g., negative slope point 7812B) of the response curve (indicated by dashed liens). Similarly, as shown in FIG. 79C, error due to horizontal drift is compensated through alternating multi-pulse data collection 7940a-7940e (indicated by solid lines) on a first slope point of the response curve associated with a first spin state (e.g., positive slope point 7812A) and multi-pulse data collection 7945a-7945e (indicated by dashed lines) on a second slope point of the response curve associated with a second spin state (e.g., positive slope point 7812A') of the response curve.

[0751] While five pulses are shown for each data collection interval in FIGS. 79B and 79C, the total number of pulses or windows may vary and range from one pulse per interval up to about 400 pulses per interval. Longer segments of data collection allow for the averaging of intensity measurements over 60 Hz cycles, which provides a low-pass filter that nulls harmonics due to outside noise. In addition, in some embodiments, each of the pulses in a data collection interval (e.g., pulses 7930a-7930e shown in FIG. 79B) may be averaged to achieve a better signal-to- noise ratio. In other embodiments, initial pulses in a data collection interval (e.g., pulses 7930a- 7930c shown in FIG. 79B) may also serve as guard "pulses," in which only the subsequent pulses (e.g., pulses 7930d-7930e) are averaged to obtain measurement data. These guard pulses allow for the thermal stability of the system 600 to be maintained by maintaining a regular RF excitation and optical excitation pattern while allowing the system 600 to ignore intensity measurements associated with transitions between frequencies.

[0752] In some cases, the need for guard intervals and/or guard pulses to ensure sufficient repolarization of the system 600 may be eliminated through the use of two optical light sources, one with a relatively high power to provide reset of spin polarization and another to induce fluorescence for the readout. Such a system is described in U.S. Non-Provisional Patent Application No. 15/382,045, entitled "Two-Stage Optical DNV Excitation," filed January 4, 2017, which is incorporated herein by reference in its entirety.

[0753] In addition to guard intervals and/or guard pulses, in cases of RF excitation applied as Ramsey RF pulse sequences, the pulse sequence parameters may be re-optimized (i.e., pulse parameters π and τ) when switching from a response curve associated with one NV center orientation and/or spin state to a response curve associated with another NV center orientation and/or spin state. For example, when switching from a response curve associated with a first spin state of an NV center orientation to a response curve associated with a second spin state of the same NV center orientation, such as during horizontal drift error compensation, the Ramsey pulse sequence parameters may be re-optimized for the response curve associated with the second spin state. By doing so, the fluorescence intensity values and the contrast values may better match between the two response curves, thereby ensuring maximum sensitivity during the measurement collection process.

[0754] Some concepts presented herein provide for a magnetic detection system that provides for a multi-RF excitation scheme capable of compensating for measurement errors due to vertical and horizontal fluctuations in fluorescence intensity during the collection process, allowing for increased sensitivity and stability of the detection system. In addition, by utilizing guard intervals (i.e., multi-pulse sets) while switching between frequencies and guard pulses within pulse sets ensures that residual effects due to previous measurement collections are reduced or eliminated. This allows a system to forego the use of high-powered optical excitation for the required repolarization of the system, thus improving sensor performance and cost.

[0755] The drift error compensation described herein may be implemented in hardware, software or a combination of hardware and software, for example by the processing system 18400 of FIG. 184. A general purpose computer processor (e.g., processing system 18402 of FIG. 184) for receiving signals may be configured to receive and execute computer readable instructions. The instructions may be stored on a computer readable medium in communication with the processor. One or more processors may be used for calculation some or all of the drift error computations according to a non-limiting embodiment of the present disclosure.

Thermal Drift Error Compensation Implementation

[0756] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented with methods for thermal drift compensation.

[0757] The present disclosure relates to systems and methods for estimating a full three- dimensional magnetic field from a magneto-optical defect center material, such as a NV center diamond material. The systems and methods only require using the spectral position of four electron spin resonances to recover a full three-dimensional estimated magnetic field, in the case of NV diamond material. By using only a subset of the full eight electron spin resonances, a faster vector sampling rate is possible. [0758] Further the systems and methods described for determining the estimated three- dimensional magnetic field are insensitive to temperature drift. Thus, the temperature drift is inherently accounted for.

[0759] Still further, according to the systems and methods described, the thermal drift in the spectral position of the electron spin resonances used in the magnetic field estimation may be readily calculated based on a four-dimensional measured projected magnetic field (onto the diamond lattice vectors) and the three-dimensional estimated magnetic field.

[0760] Referring back to FIGS. 6A-6C, the controller 680 controls the operation of the optical excitation source 610, the RF excitation source 630, and the magnetic field generator 670 to perform Optically Detected Magnetic Resonance (ODMR). Specifically, the magnetic field generator 670 may be used to apply a bias magnetic field that sufficiently separates the intensity responses corresponding to electron spin resonances for each of the four NV center orientations. The controller 680 then controls the optical excitation source 610 to provide optical excitation to the NV diamond material 620 and the RF excitation source 630 to provide RF excitation to the NV diamond material 620. The resulting fluorescence intensity responses for each of the NV axes are collected over time to determine the components of the external magnetic field Bz aligned along directions of the four NV center orientations which respectively correspond to the four diamond lattice crystallographic axes of the NV diamond material 620, which may then be used to calculate the estimated vector magnetic field acting on the system 600. The excitation scheme utilized during the measurement collection process (i.e., the applied optical excitation and the applied RF excitation) may be any appropriate excitation scheme. For example, the excitation scheme may utilize continuous wave (CW) magnetometry, pulsed magnetometry, and variations on CW and pulsed magnetometry (e.g., pulsed RF excitation with CW optical excitation). In cases where Ramsey pulse RF sequences are used, pulse parameters π and τ may be optimized using Rabi analysis and FID-Tau sweeps prior to the collection process, as described in, for example, U.S. Patent Application No. 15/003,590.

[0761] During the measurement collection process, fluctuations may occur in the measured intensity response due to effects caused by components of the system 600, rather than due to true changes in the external magnetic field. For example, prolonged optical excitation of the NV diamond material by the optical excitation source 610 may cause vertical (e.g., red

photoluminescence intensity) fluctuations, or vertical drift, in the intensity response, causing the response curve to shift upward or downward over time. In addition, thermal effects within the system 600 may result in horizontal (e.g., frequency) fluctuations, or horizontal drift, in the measured intensity response, causing the response curve to shift left or right over time depending on whether the temperature of the magneto-optical defect center material has increased or decreased.

[0762] In deriving the three-dimensional magnetic field vector impinging on the system 600 from the measurements obtained by the intensity response produced by the NV diamond material 620, it is desirable to establish the orientation of the NV defect center axes, or magneto-optical defect center axes more broadly, of the NV diamond material 620, or the magneto-optical defect center material more broadly, to allow for the accurate recovery of the magnetic field vector and maximize signal-to-noise information. Since the NV defect center axes are aligned along the respective crystallographic axes of the diamond lattice for the NV diamond material 620, the analysis below is with respect to the four crystallographic axes of the diamond lattice. Of course, the number of crystallographic axes will depend upon the material used in general for the magneto-optical defect center material, and may be a different number than four.

[0763] As shown in FIG. 80, a Cartesian reference frame having {x, y, z}orthogonal axes may be used, but any arbitrary reference frame and orientation may be used. FIG. 80 shows a unit cell 100 of a diamond lattice having a "standard" orientation. In practice, the diamond lattice of the NV diamond material may be rotated relative to the standard orientation, but the rotation may be accounted for, for example, as discussed in U.S. Application No, 15/003,718 entitled

"APPARATUS AND METHOD FOR RECOVERY OF THREE DIMENSIONAL MAGNETIC FIELD FROM A MAGNETIC DETECTION SYSTEM", filed January 21, 2016, the entire contents of which are incorporated herein. For simplicity, only the standard orientation will be discussed here. The axes of the diamond lattice will fall along four possible directions. Thus, the four axes in a standard orientation may be defined as unit vectors corresponding to:

[0764] For simplicity, the four vectors of the above equation may be represented by a single matrix As, which represents the standard orientation of the unit cell 8000:

[0765] Assuming the response is linear with the magnetic field, the true magnetic field b may be expressed as a linear model on the four coordinate axes as:

A1 b + w = m

[0766] where: b E E3 l is the true magnetic field vector in the NV diamond material excluding any field produced by a permanent magnet bias; w E E4 l is a sensor noise vector; m E R4xl is a vector where the ith element represents the magnetic field measurements along the Ith axis; and ATb gives the projection of the true magnetic field vector onto each of the four axes and AT is the transpose of As. More generally, ^ Trepresents the orientation of the diamond lattice after an arbitrary orthonormal rotation and possible reflection of the axes matrix As.

[0767] The bias magnetic field serves to separate the Lorentzians response curves of the fluorescence measurement corresponding to the electron spin resonances associated with the different crystallographic axes of the diamond material. For two spin states ms = ±1 for each crystallographic axis, there will be 8 Lorentzians, two Lorentzians corresponding to each crystallographic axis. The bias magnetic field may be calibrated to separate the Lorentzians corresponding to the different electron spin resonances as described in U.S. Application No. 15/003,718 entitled "APPARATUS AND METHOD FOR RECOVERY OF THREE

DIMENSIONAL MAGNETIC FIELD FROM A MAGNETIC DETECTION SYSTEM."

[0768] Further, for a given crystallographic axis and its corresponding two spin states, the magnitude of the projection of the magnetic field along the crystallographic axis can be determined, but the sign or direction of the projection will not be initially unknown. The sign due to the bias magnetic field for each crystallographic axis can also be recovered as described in U.S. Application No, 15/003,718 entitled "APPARATUS AND METHOD FOR RECOVERY OF THREE DIMENSIONAL MAGNETIC FIELD FROM A MAGNETIC DETECTION SYSTEM."

[0769] The model from the prior equation can be expanded to include temperature drift as follows, where it is presumed that the measurements of the different electron spin resonances are taken simultaneously or at least quickly enough that the temperature drift between measurements is insignificant.

A1 b + c + w = m

[0770] where c E o4xl is a constant vector representing a fixed, but unknown offset c

on the measurements from all four axes due to temperature. This model is valid presuming the sign used during the sign recovery process, due to the bias magnetic field, is the same for all four electron spin resonances, used. Such uniformity in the per lattice sign recovery process ensures that the modeled scalar translations of each lattice due to thermal drift share the same sign and, thus, that the drift vector represents a constant vector rather than a vector whose elements have fixed magnitude but varying sign. For a true quad bias magnet configuration (e.g., an alignment in which the bias magnet projects onto the lattice vectors in a relative 7:5 :3 : 1 ratio), potential sets of valid resonances, where the resonances are denoted as 1-8 starting from the left, would be { 1, 4, 6, 7} or {2, 3, 5, 8}, for example. This is shown below.

[0771] FIG. 81 A illustrates two fluorescence curves as a function of RF frequency for two different temperatures in the case the external magnetic field is aligned with the bias magnetic field. Each of the fluorescence curves has eight electron spin resonances, each electron spin resonance corresponding to one cry stall ographic axis and one spin state. Each of the resonances shifts in the same direction due to a temperature shift for those resonances where the sign used during the sign recovery process, due to the bias magnetic field, is the same. In this case, resonances in the set { 1, 4, 6, 7} shift in the same direction based on temperature shift.

[0772] FIG. 8 IB illustrates two fluorescence curves as a function of RF frequency for two different magnetic fields based on a change in the bias magnetic field. In this case, the external magnetic field is aligned with the bias magnetic field and creates an equal shift in each lattice with comparable amplitude to the thermal shift in FIG 81 A . Each of the fluorescence curves has eight resonances, each resonance corresponding to one crystallographic axis and one spin state. As can be seen, the resonance shifts need not all shift in the same direction based on a magnetic field shift for the set of resonances { 1, 4, 6, 7} .

[0773] FIG. 81C is similar to FIG. 8 IB but shows the resonances need not all shift in the same direction and with the same amplitude based on a magnetic field shift for the set of resonances { 1, 4, 6, 7} in the case of a more general external field. In FIGS. 81 A-81C, the results are based on a continuous wave measurement.

[0774] IThe magnetic field may now be determined using only a subset of all of the eight resonances, namely four of the eight resonances. Given the linear model for magnetic field measurement, a least-squares solution for the total magnetic field b acting on the system based on the four measurements (using sets { 1, 4, 6, 7} or {2, 3, 5, 8}) in the absence of temperature drift may be provided as: b m

[0775] where w' = -Aw represents a scaled sensor noise vector, AT is the transpose of A, and the subscript + denotes the pseudoinverse. Applying this solution to the model with a temperature drift provides the equation below:

(AT)+m = -Am

[0776] Thus, the temperature drift term c disappears from the least-squares solution and the solution is therefore insensitive to temperature drift. Moreover, only a subset of all of the resonances need be used to determine the three-dimensional magnetic field.

[0777] The thermal drift term c may be determined based on the estimated three-dimensional magnetic field b acting on the DNV material. In particular, an estimate of the offset c vector and, hence, the scalar constant of the thermal offset, c, which is the per element magnitude, can be obtained by projecting the estimated three-dimensional magnetic field b back onto the four lattice vectors and differencing this projection with the original magnetic field measurements m as follows in the below equation:

m - ATb = (ATb + c + w) - AT (b + w')

3

= (ATb + c + w) - (ATb + AT -Aw)

3 _

= c + w A1 Aw

4

= c + w— w

= c

[0778] Thus, the thermal offset due to temperature drift may be calculated based on the four- dimensional magnetic field measurements m and the estimated three-dimensional magnetic field b, which is projected onto the crystallographic axes.

[0779] The present disclosure relates to systems and methods for estimating a full three- dimensional magnetic field from a magneto-optical defect center material, such as a NV center material. The systems and methods only require using the spectral position of four electron spin resonances to recover a full three-dimensional estimated magnetic field, in the case of NV diamond material. By using only a subset of the full eight electron spin resonances, a faster thermally-compensated vector sampling rate is possible.

[0780] Further the systems and methods described for determining the estimated three- dimensional magnetic field are insensitive to temperature drift. Thus, the temperature drift is inherently accounted for.

[0781] Still further, according to the systems and methods described, the thermal drift in the spectral position of the electron spin resonances used in the magnetic field estimation may be readily calculated based on the four-dimensional measured magnetic field lattice projections and the three-dimensional estimated magnetic field.

[0782] The thermal drift error compensation described herein may be implemented in hardware, software or a combination of hardware and software, for example by the processing system 18400 of FIG. 184. A general purpose computer processor (e.g., processing system 18402 of FIG. 184) for receiving signals may be configured to receive and execute computer readable instructions. The instructions may be stored on a computer readable medium in communication with the processor. One or more processors may be used for calculation some or all of the thermal drift error computations according to a non-limiting embodiment of the present disclosure. Pulsed RF Methods of Continuous Wave Measurement Implementation

[0783] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented using pulsed RF methods for continuous wave (CW) measurements.

[0784] In pure CW excitation schemes, continuous RF and laser power set-ups are used to generate fluorescence in DNV systems, which are then measured to estimate magnetic field. Prior to this measurement, it is common to adjust RF excitation frequency and allow the DNV system to settle at a new steady state level of fluorescence.

[0785] In pure pulsed excitation schemes, laser/optical excitation is applied for an extended period of time with no RF excitation to polarize (i.e. reset) the quantum state of the ensemble DNV system. After the laser is turned off (for example, with an acousto-optic modulator (AOM) shutter or laser power controller), a series of RF excitation pulses are applied to the diamond for a predetermined duration and having predetermined power and frequency to optimize DNV sensitivity. Once the RF pulse sequence is completed, the laser/optical excitation is restarted and a fluorescence measurement is captured to estimate magnetic field. In practical implementation, the laser polarization pulse and laser/optical excitation pulse (which leads to fluorescence measurement) are combined as a single, longer duration pulse between RF pulse sequences. Common DNV Pulse techniques include Ramsey and Hahn Echo excitations.

[0786] The present disclosure describes a magnetic detection system having a laser operated in CW mode throughout and a pulsed RF excitation source operating only during fluorescence measurement periods. Pulsing the RF only during fluorescence measurement periods rather than maintaining a CW RF excitation source allows for RF-free laser time for faster quantum reset and thus, higher bandwidth measurements; higher RF peak power during bandwidth

measurements to meet sensitivity objectives; and, an improved sensor C-SWAP by reducing RF duty cycle and supporting efficient implementation of a two-stage optical excitation scheme. Moreover, the RF pulsing methods disclosed herein also allow for shortening of the RF pulse width to optimize and balance the overall DNV system response.

[0787] Some embodiments of a pulsed RF excitation source are described with respect to a diamond material with NV centers, or other magneto-optical defect center material. The intensity of the RF field applied to the diamond material by the RF excitation source will depend on the power of the system circuit. Specifically, the power is proportional to the square of the intensity of the RF field applied. It is desirable to reduce the power of the system circuit while maintaining the RF field. By pulsing the RF excitation, the total RF energy required by the sensor system may be reduced, thus producing a more efficient sensor (having a lower power and thermal loading) while maintaining the high RF power during excitation and readout required for overall sensitivity.

[0788] Similar to traditional CW DNV techniques, a laser is operated in CW mode throughout. To obtain magnetometry measurements, an RF pulse at the relevant resonant frequency is applied to a diamond and the resulting fluorescence is measured by one or more photo detectors. By controlling the RF pulse and photo detector collection times, a short but sufficient time is provided to allow the RF pulse to interact with the relevant [NV-] electron spin state and affect the corresponding level of diamond fluorescence dimming. Upon completion of the photo detector collection interval, both the RF excitation source and photo detector are suppressed, and the laser begins repolarization of the [NV-] quantum states to set the diamond system for the next measurement. By suppressing the RF excitation source during repolarization, the normally competing RF/laser quantum drivers are simplified to allow only the laser repolarization, with a subsequent decrease in required time for full repolarization and, therefore, greater DNV CW magnetometry sample bandwidth.

[0789] FIG. 82 illustrates a magneto-optical defect center material excitation scheme operating in CW Sit mode using a CW laser functioning throughout and a pulsed RF excitation source operating at a single frequency having a pulse repetition period (i.e. pulse sequence) of approximately 110 μβ. The CW Sit mode of collection at a fixed frequency (per diamond lattice and ±1 spin state resonance) does not preclude shifts between the different lattices, each of which would have a fixed RF excitation frequency.

[0790] As understood by those skilled in the art, a baseline CW Sweep was conducted prior to the CW Sit excitation scheme operation to select resonance frequencies and establish the relationship between fluorescence intensity and magnetic field for each diamond lattice and ±1 spin state. This relationship captures how a CW Sit excitation scheme-measured fluorescence intensity change for each lattice and spin state indicates a shift in the local baseline CW Sweep which, to first order, is proportional to a change in the external magnetic field.

[0791] In some embodiments, the pulse sequence includes a period of idle time followed by a period of time for an RF pulse. The idle time allows for repolarization of [NV-] electron spin states by light from the laser before the RF pulse. According to some embodiments, the period of time for the RF pulse is greater than the period of idle time. In some embodiments, the period of time for the RF pulse may vary between approximately 56 and 109 μβ, or 60 and 105 μβ, or 65 μβ and 100 μβ, or 70 μβ and 95 μβ, or 75 μβ and 90 μβ, or 80 μβ and 85 μβ. In some embodiments, the period of time for the RF pulse may be about 80 μβ. In some embodiments, the period of idle time may vary between approximately 1 μβ and 54 μβ, or 5 μβ and 50 μβ, or 10 μβ and 45 μβ, or 15 μβ and 40 μβ, or 20 μβ and 35 μβ, or 25 μβ and 30 μβ. In some embodiments, the period of idle time may be about 30 μβ.

[0792] In some embodiments, the period of idle time includes an optional period of time for reference collection with the RF pulse off. In other words, a reference fluorescence may be measured prior to applying the RF pulse to the diamond at the relevant resonant frequency. The reference collection measures the baseline intensity of fluorescence prior to RF excitation such that the net additional dimming due to the RF may be estimated by comparison with this reference (i.e. subtraction of the baseline fluorescence). For collections across multiple diamond lattices in which the fluorescence "dimming" from the previous RF excitation may not have fully repolarized, the reference collection allows measurement of the additional dimming caused by excitation of the new set of [NV] along the next diamond lattice. In some embodiments, the period of time for reference collection may vary between 1 μβ and 20 μβ. In some embodiments, the period of time for reference collection may be about 5 μβ. In some embodiments, the period of time for reference collection may vary proportionally with the period of idle time (i.e. longer periods of idle time having longer periods of time for reference collection).

[0793] In some embodiments, the period of time for the RF pulse includes a period of settling time followed by a period of time for fluorescence measurement (i.e. collection time). During collection time, both the CW laser and the RF pulse are "on" and the fluorescence is detected by the photo detectors. This period of time for fluorescence measurement may vary between 56 μβ and 95 μβ, or 60 μβ and 90 μβ, or 65 μβ and 85 μβ, or 70 μβ and 80 μβ. In some embodiments, the period of time for fluorescence measurement may be about 60 μβ.

[0794] FIG. 83 illustrates a magneto-optical defect center material excitation scheme operating in CW Sweep mode using a CW laser functioning throughout and a pulsed RF excitation source swept at different frequencies having a pulse repetition period of approximately 1100 μβ. In some embodiments, the pulse sequence includes a period of idle time followed by a period of time for an RF pulse. According to some embodiments, the period of idle time is greater than the period of time for the RF pulse. In some embodiments, the period of time for the RF pulse may vary between approximately 1 and 549 μβ, or 25 and 525 μβ, or 50 μβ and 500 μβ, or 75 μβ and 475 μβ, or 100 μβ and 450 μβ, or 125 μβ and 425 μβ, or 150 μβ and 400 μβ, or 175 μβ and 375 μβ, or 200 μβ and 350 μβ, or 225 μβ and 325 μβ, or 250 μβ and 300 μβ. In some

embodiments, the period of time for the RF pulse may be about 100 μβ. In some embodiments, the period of idle time may vary between approximately 551 μβ and 1099 μβ, or 575 μβ and 1075 μβ, or 600 μβ and 1050 μβ, or 625 μβ and 1025 μβ, or 650 μβ and 1000 μβ, or 675 μβ and 975 μβ, or 700 μβ and 950 μβ, or 725 μβ and 925 μβ, or 750 μβ and 900 μβ, or 775 μβ and 875 μβ, or 800 μβ and 850 μβ. In some embodiments, the period of idle time may be about 1000 μβ.

[0795] In some embodiments, the period of idle time includes an optional period of time for reference collection with the RF pulse off. In some embodiments, this period of time for reference collection may vary between 1 μβ and 20 μβ. In some embodiments, the period of time for reference collection may be about 5 μβ. In some embodiments, the period of time for reference collection may vary proportionally with the period of idle time (i.e. longer periods of idle time having longer periods of time for reference collection). In some embodiments, the period of time for the RF pulse includes a period of settling time followed by a period of time for fluorescence measurement (i.e. collection time). This period of time for fluorescence measurement may vary between 56 μβ and 95 μβ, or 60 μβ and 90 μβ, or 65 μβ and 85 μβ, or 70 μβ and 80 μβ. In some embodiments, the period of time for fluorescence measurement may be about 60 μβ.

[0796] The pulsed RF method, together with CW laser excitation, provides improved sample bandwidth over traditional CW DNV excitation while maintaining the sensitivity of the traditional methods. The reduction in RF duty cycle requires less power and creates less thermal drive on the diamond sensor. This reduction in duty cycle offers greater flexibility for practical sensor design trades. The pulsed CW method allows for increasing bandwidth without increasing both the RF and laser power. In combination with reduced power usage, these trade spaces support an improved overall sensor C-SWAP. This improved C-SWAP increases implementation of efficient DNV magnetometry sensors. The proposed solution is also compatible with high power-low duty cycle laser repolarization techniques to support faster sampling and increased sample bandwidth for vector magnetometry and/or thermally

compensated multi-lattice excitation techniques. [0797] The pulsed RF method described herein may be implemented in hardware, software or a combination of hardware and software, for example by the processing system 18400 of FIG. 184. A general purpose computer processor (e.g., processing system 18402 of FIG. 184) for receiving signals may be configured to receive and execute computer readable instructions. The

instructions may be stored on a computer readable medium in communication with the processor.

High Speed Sequential Cancellation for Pulsed Mode Implementation

[0798] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented using a high speed sequential cancellation for increasing bandwidth of the devices.

[0799] Following below are more detailed descriptions of various concepts related to, and implementations of, methods, apparatuses, and systems for high bandwidth acquisition of magnetometer data with increased sensitivity. Some embodiments increase bandwidth and sensitivity of the magnetometer by eliminating the need for a reference signal that requires full repolarization of the magneto-optical defect center material prior to acquisition. Eliminating the reference signal eliminates the time needed to repolarize the magneto-optical defect center material and the acquisition time for the reference signal. An optional ground reference, a fixed "system rail" photo measurement, and/or additional signal processing may be utilized to adjust for variations in intensity levels.

[0800] FIG. 84 depicts a graph 8400 of a magnetometer system using a reference signal 8410 acquisition prior to RF pulse excitation sequence 8420 and measured signal 8430 acquisition. A contrast measurement between the measured signal 8430 and the reference signal 8410 for a given pulsed sequence is then computed as a difference between a processed read-out

fluorescence level from the measured signal acquisition 8430 and a processed reference fluorescence measurement from the reference signal 8410. The processing of the measured signal 8430 and/or the reference signal 8410 may involve computation of the mean fluorescence over each of the given intervals. The reference signal 8410 is to compensate for potential fluctuations in the optical excitation power level, which can cause a proportional fluctuation in the measurement and readout fluorescence measurements. Thus, in some implementations the magnetometer includes a full repolarization between measurements with a reference fluorescence intensity (e.g., the reference signal 8410) captured prior to RF excitation (e.g., RF pulse excitation sequence 8420) and the subsequent magnetic b field measurement data 8430. This approach may reduce sensor bandwidth and increase measurement noise by requiring two intensity estimates per magnetic b field measurement. For a DNV magnetometer, this means that it needs full repolarization of the ensemble diamond [NV] states between measurements. In some instances, the bandwidth considerations provide a high laser power density trade space in sensor design, which can impact available integration time and achievable sensitivity.

[0801] FIG. 85 depicts a graph 8500 of a magnetometer system omitting a reference signal acquisition prior to RF pulse excitation sequence 8520 and measured signal 8530 acquisition. The RF pulse excitation sequence 8520 may correspond to periods 1-3 of FIG. 5 and the measured signal acquisition 8530 may correspond to period 4 of FIG. 5. The graph 8500 depicts the amplitude of optical light emitted from a magneto-optical defect center material as measured by an optical detector 340, such as a photodiode, over time. The system processes the post RF sequence read-out measurement from the measured signal 8530 directly to obtain magnetometry measurements. The processing of the measured signal 8530 may involve computation of the mean fluorescence over each of the given intervals. In some implementations, a fixed "system rail" photo measurement is obtained and used as a nominal reference to compensate for any overall system shifts in intensity offset. In some implementations, an optional ground reference signal 8510 may be obtained during the RF pulse excitation sequence 8520, such as during period 2 of FIG. 5, to be used as an offset reference. Some embodiments provide faster acquisition times, reduced or eliminated noise from the reference signal, and increased potential detune intensity peak to peak contrast.

[0802] FIG. 86 is a graphical diagram of an intensity of a measured signal 8610 from an optical detector 340 relative to an intensity of a reference signal 8620 from the optical detector 340 over a range of detune frequencies. When using a reference signal 8620, the reference signal 8620 will contain signal information from a prior RF pulse for a finite period of time. This prior signal information in the reference signal 8620 reduces available detune peak to peak intensity range and slope for a detune point for positive slope 8630 and a detune point for negative slope 8640. That is, as shown in FIG. 86, the reference signal 8620 is curved in a similar manner to the measured signal 8610. Accordingly, when a reference signal 8620 value is subtracted from a corresponding measured signal 8610 at a corresponding detune frequency, the net magnetometry curve peak to peak intensity contrast is reduced. The reason that the reference signal 8610 curve contains information from the measured signal 8610 curve is due to insufficient (laser only) polarization time for a given sensor configuration. The prior RF pulse defines the state of the measurement and, if not enough time passes between measurements, then the reference signal 8620 will contain some of the "hold" data from the prior RF "sample." This will subtract from the current measured signal 8610, thereby resulting in less signal overall as seen in FIG. 86. Thus, to remove the prior signal information, the system would need to wait until the prior signal information is eliminated from the reference signal or operate without the reference signal, such as described herein. Prior signal information from a prior measured signal 8610 (RF pulse) is cleared out via excitation from a green laser source and waiting for a period of time. This decay is exponential and tied to the power density applied from laser. However, waiting for a period of time for the prior signal information to be eliminated can decrease available bandwidth.

[0803] FIG. 87 is a diagram depicting slope relative to laser polarization pulse width for a system implementing a reference signal and a system omitting the reference signal. A first slope line 8710 corresponds to a system utilizing a reference signal while a second slope line 8720 corresponds to a system without utilizing a reference signal. As shown, the second slope line 8720 has a higher slope at equivalent laser pulse widths (in microseconds) compared to the first slope line 8710 that uses a reference signal. Longer polarization pulse widths can allow for a more complete repolarization of the a magneto-optical defect center material quantum state to reduce the residual impact of previous RF excitations. In effect, this more complete polarization can allow "less dimmed" fluorescence levels to be measured more accurately rather than exhibiting residual dimming due to an earlier RF excitation that retains some NV spin +1/-1 excited states. The wider measurement range can increase the peak to peak intensity range and, therefore, optimal slope. While both unreferenced first slope line 8710 and the referenced second slope line 8720 indicate a drop off in slope with shorter polarization pulse widths, the referenced second slope line 8720 decreases more quickly than the unreferenced first slope line 8710 due to the incomplete polarization of the reference, such as the reference signal 8620 of FIG. 86, that is further subtracted from the measured signal, such as measured signal 8610 of FIG. 86. As shown, the second slope line 8720 has a slower roll-off (e.g., reduction) of slope at shorter laser pulse widths than the first slope line 8710. That is, the lase pulse widths can be reduced without a significant decrease in optimal slope values. The second slope line 8720 can achieve a smaller laser pulse width of approximately 60-70 microseconds with minimal loss in slope compared to the first slope line 8710 that reduces slope by a factor of two when the laser pulse width is reduced by a factor of four. Thus, by eliminating the need for the reference signal, the second slope line 8720 demonstrates that the system can achieve an increase in sample rate by a factor of four with minimal impact on the slope point.

[0804] FIG. 88 depicts a comparison of a sensitivity of a system relative to a laser polarization pulse length for a system implementing a reference signal and a system omitting the reference signal. In the diagram shown, a first sensitivity line 8810 for the system implementing the reference signal has a lower sensitivity achievable at 10 nanoTeslas per root Hertz for a polarization pulse length of 150 microseconds. Thus, the system is limited in sampling rate based on a polarization pulse length of 150 microseconds as lower polarization pulse lengths reduce the sensitivity achievable to higher values. In comparison, a second sensitivity line 8820 for the system without the reference signal continues to increase the achievable lower sensitivity for lower polarization pulse lengths below 150 microseconds. Thus, by eliminating the reference signal, the sensitivity of the system can be improved for shorter polarization pulse lengths.

[0805] FIG. 89 depicts some implementations of a process 8900 of operating a magnetometer that utilizes a magneto-optical defect center material, such as a diamond having nitrogen vacancies. The process 8900 includes activating an RF pulse sequence (block 8902). The RF pulse sequence is done without acquiring a reference measurement, thereby reducing

measurement noise and increasing sample bandwidth by eliminating noise introduced by the reference measurement and decreasing the time between measurement acquisitions. In some implementations, a nominal ground reference measurement (block 8904) may be acquired as a simple offset relative to the ground state. The process 8900 further includes acquiring b field measurement data (block 8906). The acquisition of b field measurement data may be acquired at a faster sample rate as full repolarization of the magneto-optical defect center material is eliminated between measurements. In some implementations, the acquired b field measurement data may be processed to determine a vector of a measured b field. By removing the reference signal, a sensor can increase AC sensitivity and bandwidth.

[0806] The process described herein may be implemented in hardware, software or a combination of hardware and software, for example by the processing system 18400 of FIG. 184. A general purpose computer processor (e.g., processing system 18402 of FIG. 184) for receiving signals may be configured to receive and execute computer readable instructions. The

instructions may be stored on a computer readable medium in communication with the processor. Photodetector Circuit Saturation Mitigation Implementation

[0807] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented using a photodetector circuit saturation mitigation component.

[0808] Some embodiments disclosed herein relate to a system including a magneto-optical defect center material, a first optical excitation source configured to provide a first optical excitation to the magneto-optical defect center material, a second optical excitation source configured to provide a second optical excitation to the magneto-optical defect center material, and an optical detection circuit. The optical detection circuit which includes a photocomponent, (e.g., a photodetector) may be configured to activate a switch between a disengaged state and an engaged state, receive, via the second optical excitation source, a light signal including a high intensity signal provided by the second optical excitation source, and cause at least one of the photocomponent or the optical detection circuit to operate in a non-saturated state responsive to the activation of the switch. The second optical excitation source rapidly illuminates the magneto-optical defect center material with light to re-polarize the magneto-optical defect center material without loss of sensitivity.

[0809] With reference to FIG. 90, some embodiments of a circuit saturation mitigation system 9000 is illustrated. The circuit saturation mitigation system 9000 uses fluorescence intensity to distinguish the ms = ±1 states, and to measure the magnetic field based on the energy difference between the ms = +1 state and the ms = -1 state, as manifested by the RF frequencies

corresponding to each state. In these embodiments, the circuit saturation mitigation system 9000 includes a first optical excitation source 9010, second optical excitation source 9015, a magneto- optical defect center material 9005, a RF excitation source 9020, and an optical detection circuit 9040. The first and second optical excitation sources 9010, 9015 direct or otherwise provide optical excitation to the magneto-optical defect center material 9005. The RF excitation source 9020 provides RF radiation to the magneto-optical defect center material 9005. Light from the magneto-optical defect center material (e.g., diamonds, Silicon Carbide (SiC), etc.) may be directed through an optical filter (not shown) to the optical detection circuit 9040.

[0810] In general, the circuit saturation mitigation system may instead employ different magneto-optical defect center materials, with a plurality of magneto-optical defect centers. Magneto-optical defect center materials include, but are not limited to, diamonds, Silicon Carbide (SiC) and other materials with nitrogen, boron, or other defect centers. The electronic spin state energies of the magneto-optical defect centers shift with magnetic field, and the optical response, such as fluorescence, for the different spin states may not be the same for all of the different spin states. In this way, the magnetic field may be determined based on optical excitation, and possibly RF excitation, in a corresponding way to that described above with magneto-optical defect center material.

[0811] In some embodiments, the RF excitation source 9020 may take the form of a

microwave coil. The RF excitation source 9020, when emitting RF radiation with a photon energy resonant with the transition energy between ground ms = 0 spin state and the ms = +1 spin state, excites a transition between those spin states. For such a resonance, the spin state cycles between ground ms = 0 spin state and the ms = +1 spin state, reducing the population in the ms =

0 spin state and reducing the overall fluorescence at resonances. Similarly, resonance and a subsequent decrease in fluorescence intensity occurs between the ms = 0 spin state and the ms = -

1 spin state of the ground state when the photon energy of the RF radiation emitted by the RF excitation source may be the difference in energies of the ms = 0 spin state and the ms = -1 spin state.

[0812] The first and second optical excitation sources 9010, 9015 may take the form of a laser (e.g., a high power laser, low power laser, etc.), light emitting diode, etc. for example, which emits light in the green (e.g., a light signal having a wavelength Wl such that the color is green). In turn, the first and second optical excitation sources 9010, 9015 induces fluorescence in the red (e.g., the wavelength W2), which corresponds to an electronic transition from the excited state to the ground state. Light from the magneto-optical defect center material 9005 may be directed through an optical filter to filter out light in the excitation band (e.g., in the green), and to pass light in the red fluorescence band, which in turn may be detected by the optical detection circuit 9040. The first and second optical excitation light sources 9010, 9015 in addition to exciting fluorescence in the magneto-optical defect center material 9005 also serve to reset or otherwise re-polarize the population of the ms = 0 spin state of the ground state 3A2 to a maximum polarization, or other desired polarization.

[0813] As illustrated in FIGS. 90 and 91, the circuit saturation mitigation system 9000 further includes the optical detection circuit 9040. The optical detection circuit 9040 includes a photocomponent 9120 (as shown in FIG. 91) such as, but not limited to, a photodetector, photodiode, photosensor, or other device configured to receive a light signal and convert the light signal received into voltage or current. The optical detection circuit 9040 may be configured to receive, via the photocomponent 9120, a first optical excitation provided by the first optical excitation source 9010 (e.g., a low power laser). The first optical excitation source 9010 may provide the first optical excitation to the magneto-optical defect center material 9005. The first optical excitation may include a light signal configured to provide a continuous optical illumination (e.g., a low intensity light signal 9310 as illustrated in FIG. 93 A) of the magneto- optical defect center material 9005. For example, the low power laser may continuously illuminate the magneto-optical defect center material 9005 for a period of time. Accordingly, the photocomponent 9120, in turn, receives the first optical excitation (e.g., a light signal that provides the continuous optical illumination) provided by the first optical excitation source 9010 over the period of time. Alternatively or additionally, the photocomponent 9120 receives the induced fluorescence provided by the magneto-optical defect center material 9005.

[0814] The optical detection circuit 9040 may be configured to receive, via the

photocomponent 9120, a light signal provided via the second optical excitation source 9015 (e.g., a high power laser). In some embodiments, the second optical excitation source 9015 may provide a light signal configured to operate according to or otherwise provide a pulsed optical illumination 9320 (as illustrated in FIG. 93B) to the magneto-optical defect center material 9005. For example, the high power laser may provide a high intensity pulsed illumination to the magneto-optical defect center material 9005 for a predetermined period of time (e.g., a

predetermined period of time that may be less than the period of time during which the first optical detection circuit illuminates the magneto-optical defect center material). In turn, the photocomponent 9120 receives the second optical excitation (e.g., via a light signal that provides the high intensity pulsed illumination) provided by the second optical excitation source 9015 during the predetermined period of time. The photocomponent 9120 converts the light signal received into current (A) or voltage (V).

[0815] The optical detection circuit 9040 includes a switch 9110. The switch 9110 may be disposed in the feedback path to control the output voltage, transimpedance gain, and/or the flow of current, to reduce distortion, etc., of the optical detection circuit 9040 and/or the

photocomponent 9120. In some examples, the switch 9110 may take the form of a speed switch, relay, proximity switch, or any other switch configured to detect or otherwise sense optical or magnetic motion. The switch 9110 (e.g., a high speed relay) reduces the load (e.g., the amount of electrical power utilized or consumed) corresponding to the photocomponent 9120 (e.g., a photodetector). The switch 9110 includes electronic circuits configured to move between an engaged state (e.g., a state during which the switch may be turned on or may be otherwise closed) and a disengaged state (e.g., a state during which the switch may be turned off or may be otherwise open).

[0816] The switch 9110 may activate or otherwise move between the engaged state and disengaged state responsive to a light signal (e.g., a high intensity light signal) or magnetic field sensed. In some embodiments, the switch 9110 may activate in response to a command generated via at least one of a controller (e.g., the controller 9250 shown in FIG. 92 as described herein below) or an on-board diagnostics system (OBDS). In the engaged state, the flow of current or voltage may be uninterrupted, while the flow of current or voltage may be interrupted in the disengaged state. For example, in response to the command generated via the controller, the switch 9110 moves from the disengaged state (e.g., the flow of current or voltage may be interrupted) to the engaged state (e.g., the flow of current or voltage may be uninterrupted) and, thereby, turns on or may be otherwise closed.

[0817] Alternatively or additionally, the switch 9110 may be disengaged or otherwise deactivated via at least one of the controller (e.g., the controller 9250 shown in FIG. 92 as described herein below) or the on-board diagnostics system. For example, in response to the command generated via the controller, the switch 9110 moves from the engaged state (e.g., the flow of current or voltage may be uninterrupted) to the disengaged state (e.g., the flow of current or voltage may be interrupted) and, thereby, turns off or may be otherwise opened.

[0818] Advantageously, including the switch 9110 in the feedback path prevents the optical detection circuit 9040 and/or the photocomponent 9120 from experiencing a delay when returning to the level of voltage output prior to the application of the second optical excitation source 9015 (e.g., the high power laser) since the optical detection circuit 9040 and/or the photocomponent 9120 are in a non-saturated state as described with reference to FIG. 93 C. In turn, the repolarization time and/or the reset time corresponding to the magneto-optical defect center material 9005 may be reduced resulting in the operability of the photocomponent 9120 and/or the optical detection circuit 9040 at a higher bandwidth without signal attenuation. As shown in FIG. 93D, a delay occurs when the photocomponent 9120 and/or the optical detection circuit 9040 begins to return to the level of voltage output prior to the application of the second optical excitation source 9015 when the photocomponent 9120 and/or the optical detection circuit 9040 may be saturated.

[0819] The optical detection circuit 9040 further includes an amplifier 9130 configured to amplify the voltage provided by the photocomponent 9120. The amplifier may take the form of an operational amplifier, fully differential amplifier, negative feedback amplifier,

instrumentation amplifier, isolation amplifier, or other amplifier. In some embodiments, the photocomponent 9120, switch 9110, resistor 9140, or a combination thereof may be coupled to the inverting input terminal (-) of the amplifier 9130 (e.g., an operational amplifier).

Alternatively or additionally, the switch 9110 and the resister 9140 may be coupled to the output voltage (Vout) of the amplifier 9130 as illustrated.

[0820] In further embodiments, the optical detection circuit 9040 may be configured to cause, via the switch 9110, at least one of the photocomponent 9120 or the optical detection circuit 9040 to operate in a non-saturated state responsive to the activation of the switch 9110.

Accordingly, the amplifier 9130 receives the current or voltage provided via the photocomponent 9120. In FIG. 91 the switch 9110 may be parallel to the resistor 9140 such that in the engaged state (e.g., when the switch is closed or otherwise turned on) the switch 9110 shorts out the resistor 9140 which shutters or otherwise limits the output resistance in the transimpedance gain (e.g., the degree to which the current output via the photodetector translates to Vout) such that the resistance of the switch may be at or near 0Ω. To that end, the gain of the amplifier 9130 (e.g., the operational amplifier) expresses a gain at or near 0 which causes the output voltage Vout to be at or near 0V for the current (e.g., a variable amount of input current) or voltage received or otherwise provided by the photocomponent 9120 (e.g., the photodetector). Accordingly, the optical detection circuit 9040 operates in a non-saturated state due to the gain of the amplifier 9130 (e.g., the operational amplifier) expressing a gain at or near 0. In further embodiments, the optical detection circuit 9040 may be configured such that the output voltage Vout may be equal to the input voltage received via the amplifier 9130. The output voltage may be within a predetermined output range such as between a minimum voltage level and a maximum voltage level. The minimum voltage level and the maximum voltage level may be based on the voltage rails of the amplifier 9130 (e.g., the operational amplifier, transimpedance/gain circuit, etc). For example, if the amplifier 9130 has voltage rails of +10V and -10V, the output of the amplifier 9130 may not exceed +10V or go below -10V. Accordingly, the switch 9110 may be configured to keep the measured levels within the predetermined output range. Although the above example is directed to the predetermined output range of +10V and -10V, the predetermined output range may be +-15V, +-5V, +-3.3V, etc. Advantageously though the resister 9140 which establishes the transimpedance gain associated with the amplifier 9130 may be included in the feedback path of the optical detection circuit 9040, the optical detection circuit 9040 (e.g., the amplifier 9130) operates in the non-saturated state.

[0821] Alternatively or additionally, the switch 9110 may be further configured to reduce a load (e.g., the load impedance) corresponding to the photocomponent 9120. For example, in the engaged state the switch 9110 causes the load impedance of the photocomponent 9120 to decrease (e.g., to equal a value at or near 0 ohms (Ω)) such that the photocomponent 9120 can operate in a non-saturated state. The load (e.g., the load impedance) corresponding to the photocomponent 9120 may express a direct relationship with the state of saturation (e.g., saturated state or non-saturated state) of the optical detection circuit 9040 and/or the

photocomponent 9120 in that the higher the load impedance, the greater the amount of saturation of the optical detection circuit 9040 and/or the photocomponent 9120. Advantageously, while in the non-saturated state which results from the reduction of the load impedance, the

photocomponent 9120 can receive an increased amount of light at higher intensities. In further embodiments, a direct relationship may be expressed between the amount of saturation and the repolarization time (e.g., the reset time) of the magneto-optical defect center material 9005. For example, when the saturation of the photocomponent 9120 and/or the optical detection circuit 9040 may be reduced, the repolarization time may be reduced such that the magneto-optical defect center material 9005 may be reset quickly at higher light intensities.

[0822] FIG. 92 is a schematic diagram of a system 9200 for a circuit saturation mitigation system according to some embodiments. The system 9200 includes first and second optical light sources 9010, which direct optical light to a magneto-optical defect center material 9005. An RF excitation source 9020 provides RF radiation to the magneto-optical defect center material 9005. The system 9200 may include a magnetic field generator 9270 that generates a magnetic field, which may be detected at the magneto-optical defect center material 9005, or the magnetic field generator 9270 may be external to the system 9200. The magnetic field generator 9270 may provide a biasing magnetic field. [0823] The system 9200 further includes a controller 9250 arranged to receive a light detection signal from the optical detection circuit 9040 and to control the optical light sources 9010, 9015, the RF excitation source 9020, the switch 9110, and the magnetic field generator 9270. The controller may be a single controller, or multiple controllers. For a controller including multiple controllers, each of the controllers may perform different functions, such as controlling different components of the system 9200. The magnetic field generator 9270 may be controlled by the controller 9250 via an amplifier.

[0824] The RF excitation source 9020 may include a microwave coil or coils, for example. The RF excitation source 9020 may be controlled to emit RF radiation with a photon energy resonant with the transition energy between the ground ms = 0 spin state and the ms = ±1 spin states as discussed above with respect to FIG. 90, or to emit RF radiation at other nonresonant photon energies.

[0825] The controller 9250 may be arranged to receive a light detection signal via the optical detection circuit 9040, activate the switch 9110 based on the light detection signal received, and to control the optical light sources 9010, 9015, the RF excitation source 9020, the switch 9110, and the magnetic field generator 9270. The controller 9250 may include a processor 9252 and memory 9254, in order to control the operation of the optical light sources 9010, 9015, the RF excitation source 9020, the switch 91 10, and the magnetic field generator 9270. The memory 9254, which may include a non-transitory computer readable medium, may store instructions to allow the operation of the optical light sources 9010, 9015, the RF excitation source 9020, the switch 9110, and the magnetic field generator 9270 to be controlled. That is, the controller 9250 may be programmed or otherwise operable via programmable instructions to provide control.

[0826] FIGS. 93C and 93D illustrate the output of voltage V of the photocomponent (e.g., the photodetector). Initially the controller generates a command to activate the switch to operate in the engaged state (e.g., turns the switch on). The controller then generates a command to activate or otherwise apply the second optical light source to the magneto-optical defect center material. Responsive to the receipt of the light signal (e.g., the high power light signal) by the

photocomponent, the output of voltage by the photocomponent may be rapidly (e.g., without delay) decreased to 0V at time t0 due to the reduction of the load impedance and the non- saturated state of the photocomponent as described herein with reference to FIGS. 90 and 91. In some embodiments, the increase in the bandwidth achieved as result of the decrease in the delay to return to the previous output voltage may be at least twice (2x) the bandwidth achieved without the decrease in the delay to return to the previous output voltage. A high intensity signal at a short or otherwise minimal duration may cause the photocomponent to become saturated. The saturation time is independent of the sample rate such that the bandwidth increase may be significant. In example embodiments wherein the pulse rate is 100 (microsecond), the cycle of time pulsed may demonstrate or otherwise express a 10% improvement. If the pulse rate is 10 μβ, the cycle of time pulsed may demonstrate or otherwise express an improvement that is at least twice (2x) the cycle of time pulsed without the decrease in the delay.

[0827] When the second optical light source is no longer applied or the high intensity pulse is otherwise off, the voltage output V of the photocomponent rapidly (e.g., without delay) returns at time to to the level of voltage output V prior to the application of the second optical excitation source as a result of the photocomponent in the non-saturated state (e.g., there may be no saturation to recover from which results in no delay). In turn, the repolarization time

corresponding to the magneto-optical defect center material may be reduced such that the magneto-optical defect center material resets to a maximum polarization between the excited triplet state and the ground state rapidly. Additionally, the photocomponent operates at a higher bandwidth without signal attenuation.

[0828] With reference to FIG. 93D, initially the controller does not generate a command to activate the switch to operate in the engaged state (e.g., the switch remains turned off or is not included in the optical detection circuit). When the controller generates a command to activate or otherwise apply the second optical light source to the magneto-optical defect center material, the photocomponent receives the light signal (e.g., the high power light signal). The output of voltage V provided by the photocomponent increases at time to due to the increase of the load impedance such that the photocomponent moves to a saturated state. Alternatively or

additionally, the output voltage (Vout as shown in FIG. 91) of the amplifier approaches or otherwise reaches (e.g., hits) the rail of the amplifier (e.g., saturates the amplifier) which distorts the output voltage Vout- When the second optical light source is no longer applied or the high intensity pulse is otherwise turned off, a delay occurs at time ti when the photocomponent begins to return to the level of voltage output V prior to the application of the second optical excitation source due to the saturated state of the photocomponent and/or the amplifier. In turn, the repolarization time corresponding to the magneto-optical defect center material may be increased as shown at ti + ts such that the magneto-optical defect center material may be inhibited from resetting between the excited triplet state and the ground state rapidly.

[0829] FIGS. 94-95 illustrate the voltage output of the optical detection circuit as a function of time based on a continuous optical illumination of the magneto-optical defect center material during a time interval which includes application of the second optical excitation source (here depicted as waveform SI along the trace 9410). In FIG. 94, the x-axis indicates time where each block equals 200 ns and the y-axis indicates voltage taken at Vout where each block equals 200 mV. Initially, the magneto-optical defect center material has been reset to the ground state. The cycle of time (e.g., a value of delay) at which the switch may be turned on and turned off is illustrated in FIG. 94. As shown, when the second optical excitation source (e.g., the high power laser) is applied at a value of delay set to, for example, 0 s (e.g., 0 cycle switch on delay and 0 cycle switch off delay) and 20 ns (e.g., 1 cycle switch on delay and 0 cycle switch off delay), the increased voltage output 9420 results. The voltage output 9420 which may be indicative of high power laser data (e.g., information relating to the high power laser) in the measured signal may be beyond a predetermined output range (e.g., between a minimum voltage level and a maximum voltage level). For example, the voltage output 9420 spikes, rapidly increases, or otherwise increases beyond the predetermined output range. The voltage output may be beyond the predetermined output range as a result of the propagation delay in the switch and the use of the second optical light source (e.g., the high power signal) which increases the transimpedance gain as described above with reference to FIGS. 90 and 91. The increase in the transimpedance gain results in saturation of the optical detection circuit (e.g., the amplifier) before the switch can affect (e.g., reduce) the transimpedance gain. The optical detector circuit is thereby saturated and not sensitive during the period of time illustrated at 9420. This is further illustrated in FIG. 93D which shows the conventional behavior of the output voltage without the use of the example embodiments described herein. For example, when the second optical light source (e.g., the high power light signal) is applied, the output of voltage V provided by the photocomponent increases between time to and ti due to the increase of the load impedance such that the photocomponent moves to a saturated state and the voltage output 9420 spikes or rapidly increases. In turn, when the second optical light source is no longer applied between time t1 and ti+ts, a delay in the repolarization (e.g., a delay in the reset time) of the magneto-optical defect center material occurs as the photocomponent returns to the level of voltage output V prior to the application of the second optical excitation source. The delay in the repolarization of the magneto-optical defect center material occurs responsive to the saturated state of the photocomponent and/or the amplifier.

[0830] In FIG. 95, the delay in the cycle of time at which the second optical excitation source is turned on may be set to 10 cycles. In this example, a continuous optical illumination of the magneto-optical defect center material is applied during the time interval which includes application of the second optical excitation source. When the switch is turned on, the switch shorts the resistor which results in a rapid decrease in the voltage output 9510. The resulting voltage output 9510 of waveform SI may be at or near 0 V during application of the second optical excitation source (e.g., when the switch is engaged or may be otherwise closed) due to the delay in the cycle of time which may be set to, for example, 10 cycles in FIG. 95. As shown, the optical detector circuit is not saturated during the period of time illustrated at 9510 and the time between to and ti illustrated in FIG. 93 C such that the resulting voltage output 9510 no longer expresses a spike or increase beyond the predetermined output range in contrast to the voltage output 9420 of FIG. 94. Advantageously, the repolarization time of the magneto-optical defect center material may be reduced and the photocomponent and/or the optical detection circuit may operate at a higher bandwidth without signal attenuation.

[0831] The process described herein may be implemented in hardware, software or a combination of hardware and software, for example by the processing system 18400 of FIG. 184. A general purpose computer processor (e.g., processing system 18402 of FIG. 184) for receiving signals may be configured to receive and execute computer readable instructions. The

instructions may be stored on a computer readable medium in communication with the processor.

Shifted Magnetometry Adapted Cancellation for Pulse Sequence Implementation

[0832] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented using a shifted magnetometry adapted cancellation for a pulse sequence.

[0833] In some embodiments, the system utilizes a special Ramsey pulse sequence pair or a 'shifted magnetometry adapted cancellation' (SMAC) pair to detect and measure the magnetic field acting on the system. These parameters include the resonant Rabi frequency, the free precession time (tau), the RF pulse width, and the detuning frequency, all of which help improve the sensitivity of the measurement. For a SMAC pair measurement, two different values of tau are used as well as two different values of the pulse width for each measurement of the pair. This is in contrast to Ramsey excitation measurement where a single pulse sequence is repeated in which there may be repolarization of the system, double RF pulses separated by a gap for the free precession time, a start of the optical excitation and a readout during the optical excitation. In a SMAC excitation, there is a second set of RF pulses having a pulse width and tau values which may be different from the pulse width and tau of the first set. The first set of RF pulses is done with the first set of values, there is repolarization of the system, and then the second set of values is used to create an inverted curve. The SMAC pair estimate is a combination of the magnetometry curves of the two pulse sequences with different values. In some embodiments, the combination is the difference between the two curves. This creates a magnetometry curve with an improved slope and therefore improved performance.

[0834] In some embodiments, using the SMAC technique or SMAC pair measurements to perform a differential measurement technique, low-frequency noise such as vibrations, laser drift, low-frequency noise in the receiver circuits, and residual signals from previous

measurements (e.g., from previous measurements on other lattice vectors) get canceled out through the differential measurement technique. In some embodiments, this noise reduction may provide a sensitivity increase at lower frequencies where colored noise may be the strongest. In some embodiments, the low-frequency noise cancelation may be due to slowly varying noise in the time domain appearing almost identically in the two sequential sets of Ramsey measurements in the SMAC pair measurement. In some embodiments, inverting the second Ramsey set and subtracting the measurement from the first Ramsey set may largely cancel out any noise that is added post-inversion. Inverting the second Ramsey set and then subtracting its measurement off from the first may therefore largely cancel out any noise that is added post-inversion. In some embodiments, the low frequency noise cancelation may be understood by viewing the SMAC technique as a digital modulation technique, whereby, in the frequency domain, the magnetic signals of interest are modulated up to a carrier frequency of half the sampling rate (inverting every second set of Ramsey measurements is equivalent to multiplying the signal by e 17771 where n is the sample (i.e., Ramsey pulse number). In some embodiments, this may shift the magnetic signals of interest to a higher frequency band that is separated from the low-frequency colored noise region. Then, a high-pass filter may be applied to the signal to remove the noise, and finally, the signal may be shifted back to baseband. In some embodiments, performing a differential measurement may be equivalent to a two-tap high-pass filter, followed by a 2x down- sampling. In some embodiments, higher-order filters may be used to provide more out-of-band noise rejection to leave more bandwidth for the signal of interest.

[0835] In some embodiments, when interrogating a single lattice vector via RF and laser excitation, the sidelobe responses from nearby lattice vectors will be present. The signals from these sidelobes may cause inter-lattice vector interference, resulting in corruption of the desired measurement. The SMAC technique may see lower sidelobe levels (and thus less inter-lattice vector interference) than those from regular Ramsey measurements. For regular Ramsey measurements, different lattice vectors have potentially different optimal pulse width & tau values, based on the RF polarization, laser polarization, and gradient of the bias magnetic field. Because of this discrepancy, applying the optimal pulse width and tau settings for one lattice vector may cause the nearby lattice vectors' responses to be lower than if they were interrogated at their respective optimal values. In some embodiments, for the SMAC technique, this reduction of the nearby lattice vector's responses can become even more pronounced. Not only are there different optimal pulsewidth and tau settings for the first Ramsey set, but there may be also potentially different optimal pulse width and tau settings for the second, inverted Ramsey set. This second Ramsey set discrepancy provides potential for even more reduction in neighboring lattice vectors' responses when using the optimal settings for the lattice vector of interest.

[0836] Ramsey pulse sequence is a pulsed RF laser scheme that is believed to measure the free precession of the magnetic moment in the magneto-optical defect material 320 of FIGS. 3A-3B with defect centers, and is a technique that quantum mechanically prepares and samples the electron spin state. FIG. 96 is an example of a schematic diagram illustrating the Ramsey pulse sequence using a SMAC pair for the two pulse sequences. Several pulse sequences are shown. As shown in FIG. 96, a Ramsey pulse sequence includes optical excitation pulses (e.g., from a laser) and RF excitation pulses over a five-step period. In a first step, a first optical excitation pulse is applied to the system to optically pump electrons into the ground state (i.e., ms = 0 spin state). This is followed by a first RF excitation pulse (in the form of, for example, a pulse width / 2 (pwi/2) microwave (MW)). The first RF excitation pulse may set the system into superposition of the ms = 0 and ms = +1 spin states (or, alternatively, the ms = 0 and ms = -1 spin states, depending on the choice of resonance location). During a period 2, the spins are allowed to freely precess (and dephase) over a time period referred to as tau (τι). During this free precession time period, the system measures the local magnetic field and serves as a coherent integration. Next, a second RF excitation pulse (in the form of, for example, a MW pwi/2 pulse) is applied to project the system back to the ms = 0 and ms = +1 basis. Finally, a second optical pulse is applied to optically sample the system and a measurement basis is obtained by detecting the fluorescence intensity.

[0837] Continuing with FIG. 96, to create a SMAC pair, a second Ramsey pulse sequence includes a third optical excitation pulse applied to the system to optically pump electrons into the ground state (i.e., ms = 0 spin state). This is followed by a third RF excitation pulse (in the form of, for example, a second MW pulse width / 2 (pw2/2) ). The third RF excitation pulse may again set the system into superposition of the ms = 0 and ms = +1 spin states (or, alternatively, the ms = 0 and ms = -1 spin states, depending on the choice of resonance location). The spins are allowed to freely precess (and dephase) over a time period referred to as tau22). During this free precession time period, the system measures the local magnetic field and serves as a coherent integration. Next, a fourth RF excitation pulse (in the form of, for example, a MW pw2/2 pulse) is applied to project the system back to the ms = 0 and ms = +1 basis. Finally, a fourth optical pulse is applied to optically sample the system and a measurement basis is obtained by detecting the fluorescence intensity of the system. FIG. 96 depicts the pulse sequences continuing with another sequence with pwi.

[0838] In some embodiments, a reference signal may be determined by using a reference signal acquisition prior to the RF pulse excitation sequence and measured signal acquisition. A contrast measurement between the measured signal and the reference signal for a given pulsed sequence is then computed as a difference between a processed read-out fluorescence level from the measured signal acquisition and a processed reference fluorescence measurement from the reference signal. The processing of the measured signal and/or the reference signal may involve computation of the mean fluorescence over each of the given intervals. The reference signal acts to compensate for potential fluctuations in the optical excitation power level (and other aspects), which can cause a proportional fluctuation in the measurement and readout fluorescence measurements. Thus, in some implementations the magnetometer includes a full repolarization between measurements with a reference fluorescence intensity (e.g., the reference signal) captured prior to RF excitation (e.g., RF pulse excitation sequence) and the subsequent magnetic b field measurement data. This approach may reduce sensor bandwidth and increase

measurement noise by requiring two intensity estimates per magnetic b field measurement. For a magneto-optical defect material with defect centers magnetometer, this can means that it needs full repolarization of the ensemble defect center states between measurements. In some instances, the bandwidth considerations provide a high laser power density trade space in sensor design, which can impact available integration time and achievable sensitivity.

[0839] In some embodiments, the magnetometer system may omit a reference signal acquisition prior to RF pulse excitation sequence and measured signal acquisition. The system processes the post RF sequence read-out measurement from the measured signal directly to obtain magnetometry measurements. The processing of the measured signal may involve computation of the mean fluorescence over each of the given intervals. In some implementations, a fixed "system rail" photo measurement is obtained and used as a nominal reference to compensate for any overall system shifts in intensity offset. In some implementations, an optional ground reference signal may be obtained during the RF pulse excitation sequence to be used as an offset reference. Some embodiments provide faster acquisition times, reduced or eliminated noise from the reference signal, and increased potential detune Vpp contrast.

[0840] In some embodiments, an approximation of the readout from a Ramsey pulse sequence when the pulse width is much less than the free precession interval may be defined as the equation below:

[0841] where τ represents the free precession time, Γ2 * represents spin dephasing due to inhomogeneities present in the system 600, a)res represents the resonant Rabi frequency, ωβ^ represents the effective Rabi frequency, an represents the hyperfine splitting of the NV diamond material 320 (-2.14 MHz), Δ represents the MW detuning, and Θ represents the phase offset.

[0842] When taking a measurement based on a Ramsey pulse sequence, the parameters that may be controlled are the duration of the MW π/2 pulses, the frequency of the MW pulse (which is referenced as the frequency amount detuned from the resonance location, Δ), and the free precession time τ. FIGS. 97 A and 97B show the effects on the variance of certain parameters of the Ramsey pulse sequence. For example, as shown in FIG. 97A, if all parameters are kept constant except for the free precession time τ, an interference pattern, known as the free induction decay (FID), is obtained. The FID curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting. The decay of the signal is due to inhomogeneous dephasing and the rate of this decay is characterized by Γ2 * (characteristic decay time). In addition, as shown in FIG. 97B, if all parameters are kept constant except for the microwave detuning Δ, a magnetometry curve is obtained. In this case, the x-axis may be converted to units of magnetic field through the conversion 1 nT = 28 Hz in order to calibrate for magnetometry.

[0843] FIG. 98 is a graphical diagram of an intensity of a measured signal 9810 from an optical detector 340 relative to an intensity of a reference signal 9820 from the optical detector 340 over a range of detune frequencies. When using a reference signal 9820, the reference signal 9820 will contain signal information from a prior RF pulse for a finite period of time. This prior signal information in the reference signal 9820 reduces available detune Vpp and slope for a detune point for positive slope 9830 and a detune point for negative slope 9840. Thus, to remove the prior signal information, the system would need to wait until the prior signal information is eliminated from the reference signal or operate without the reference signal.

[0844] In some embodiments, there may be implementation of a reference signal and in some embodiments, omitting of the reference signal may be possible through the use of the SMAC pair due to the increased performance. Eliminating the need for a reference signal reduces the number of pulse measurements that need to be taken and increases the bandwidth of gathering magnetic field data (i.e., an increase in sample rate).

[0845] FIG. 99 depicts a plot of a magnetometry curve using a Ramsey sequence in accordance with some embodiments. The plot depicts intensity decreasing as you go up the y-axis, so curves seen in the plot going up represent a dimming in intensity. In some embodiments, the intensity is the measured fluorescence intensity obtained from a magneto-optical defect material with defect centers. In some embodiments, the x-axis represents an RF excitation frequency of a microwave source used in the Ramsey sequence. The magnetometry curve is due to the

constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting in addition to side lobes caused by the Ramsey pulse. In some embodiments, this curve is a representative depiction of the first pulse sequence as depicted in FIG. 96. In some embodiments, the curve shows an upward curve at the center frequency, representing dimming.

[0846] FIG. 100 depicts a plot of an inverted magnetometry curve using a Ramsey sequence in accordance with some embodiments. The plot depicts intensity decreasing as you go up the y- axis so curves seen in the plot going up represent a dimming in intensity. In some embodiments, the intensity is the measured fluorescence intensity obtained from a magneto-optical defect material with defect centers. In some embodiments, the x-axis represents an RF excitation frequency of a microwave source used in the Ramsey sequence. The magnetometry curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting in addition to side lobes caused by the Ramsey pulse. In some embodiments, this curve is a representative depiction of the second pulse sequence as depicted in FIG. 96. The values of pulse width and τ2 of the second pulse sequence are chosen such that a null is seen at the center frequency, representing a lack of dimming.

[0847] Still referring to FIG. 100 and expanding on a null seen at the center frequency representing a lack of dimming in the fluorescence. In some embodiments using a spin state of the defect center electrons, the null can be thought of in terms of a representation on a Bloch sphere where the zero reference of the spin state and the minus one spin state of the defect center electrons on a sphere are the North Pole and South Pole. In the first sequence, represented in FIG. 99, the first RF pulse may move the state from the baseline zero spin state to the equator of the Bloch sphere. The precession time after the first RF pulse may move the state around the equator of the Bloch sphere representation with time. If the chosen precession time (i.e., xi) allows for the state to go around the circumference all or most of the way before application of the second RF pulse, the second RF pulse may create maximum dimming in the fluorescence. However, if in the sequence, represented in FIG. 100, the first RF pulse was longer and for an amount of time that moved the state from the baseline zero spin state all the way to the South Pole of the Block sphere, then the precession time (i.e., τ2) allows for the state to simply go around the South Pole which is not doing anything, and the second RF pulse to create minimum dimming or take advantage of a null point in the dimming of the fluorescence.

[0848] Therefore, in some embodiments, the curve shows a downward curve at the center frequency, representing a lack of dimming. In some embodiments, the inverted curve is created because the pulse width and τ2 value are chosen such that the time given to the precession is enough to take advantage of a null point at the chosen frequency.

[0849] FIG. 101 depicts a plot showing a combined magnetometry curve of a traditional and inverted curve in accordance with some embodiments, where the curves from FIG. 99 and FIG. 100 are combined. The curves are combined by combining the intensities at each frequency value, such as for example, by taking the difference between intensities at each frequency value. In some embodiments, the intensity is the measured fluorescence intensity obtained from a magneto-optical defect material with defect centers. In some embodiments, the x-axis represents an RF excitation frequency of a microwave source used in the Ramsey sequence. In some embodiments, the plot combines the curves as depicted in FIG. 100 and FIG. 101. In some embodiments, the combined plot is obtained by taking the difference between the traditional curve and the inverted curve. The plot depicts intensity decreasing as you go up the y-axis so curves seen in the plot going up represent a dimming in intensity. The magnetometry curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting in addition to side lobes caused by the Ramsey pulse.

[0850] In some implementations such as depicted in FIGS. 99-101, when performing a magnetic field measurement using a magnetometer system, once the magnetometry curves have been obtained, a SMAC measurement is performed at a chosen frequency (e.g. at a frequency with a maximum slope for the curve) and the intensity of the SMAC measurement is monitored to provide an estimate of the magnetic field. In some embodiments, the maximum slope, positive and negative, is determined from the curve obtained by the SMAC pairing and the corresponding frequencies. In some implementations, the curve is first smoothed and fit to a cubic line. In some implementations, only the corresponding frequencies are stored for use in magnetic field measurements. In some implementations, the entire curve is stored. Various implementations may use different numbers of measurement points to plot out the curve. For example, to obtain a width of curve comprising 12.5 MHZ, 500 different frequencies separated by 25 KHz may be measured. Other widths of the curve with differing granularity of the separation of measurement points are possible. In some implementations, a plurality of measurements are done at each measurement point.

[0851] The process described herein may be implemented in hardware, software or a combination of hardware and software, for example by the processing system 18400 of FIG. 184. A general purpose computer processor (e.g., processing system 18402 of FIG. 184) for receiving signals may be configured to receive and execute computer readable instructions. The

instructions may be stored on a computer readable medium in communication with the processor.

Generation of Magnetic Field Proxy Through RF Dithering Implementation

[0852] In some implementations, the devices 300, 600A, 600B, 600C, 700, 2500, and/or 4200 can be implemented in a magnetic field proxy generation system. [0853] Following below are more detailed descriptions of various concepts related to, and implementations of, methods, apparatuses, and systems for creating a proxy magnetic field by frequency modulating a desired magnetic field proxy modulation onto an RF wave. In the implementations described herein, no actual external magnetic field are created. Magneto- optical defect center sensors may be susceptible to both internal and external or environmental changes such as temperature, DC and near DC magnetic fields, and power variability of the laser and RF. Providing a magnetic signal of known strength and orientation that can be used as a reference can provide a capability to compensate or correct for some of these environmental changes. In addition, a magnetic field proxy modulation can be used to help determine sensor operational status such as current functionality of the sensor and/or current noise or other error levels of the sensor. The use of an external magnetic source to generate a reference magnetic signal of precise field strength and orientation at a particular portion of a magneto-optical defect center material can be difficult. For instance, some current methods to generate a reference magnetic signal may use one or more external magnetic sources (e.g., a Helmholtz coil with RF source and amplification) to generate the magnetic field. In practice, it may be very difficult to precisely create a magnetic field of known strength and orientation at the magneto-optical defect center element using such methods. Additionally, it can be difficult to generate broadband magnetic signals from a single magnetic source due to the bandwidth limitations of most antennas. Instead, as described herein, a frequency modulated magnetic field proxy modulation can be formulated in lieu of an external magnetic source to generate a biasing proxy magnetic field. Such a proxy magnetic field can reliably create a reference magnetic signal of known strength and orientation, which can be used to compensate for environmental conditions. In addition, the proxy magnetic reference signal can be used for initial functional testing of the sensor and/or determination of current noise and/or error levels with the sensor.

[0854] The implementations described herein provides methods, systems, and apparatuses to generate proxy magnetic field modulations representative of a magnetic field of known frequency, magnitude, and field orientation. Such proxy magnetic field modulations can be used for off-line, periodic, or real-time calibration; real-time drift compensation; and/or built-in- testing. To produce the desired proxy magnetic field modulation, R(t), a base RF wave used to interrogate the magneto-optical defect center material can be modified by the biasing RF modulation, F(t). A final RF signal, G(t), to be used to generate the RF field at the magneto- optical defect center material can be determined based on the equation G(t) = A cos (2uF(t)t + φ), where A is the amplitude of the carrier, φ is a phase of the carrier, and F(t) is the base RF wave used to interrogate the magneto-optical defect center material modified by a biasing RF modulation based on the magnetic field proxy modulation of F(t) = Fc +yR(t), where Fc is the frequency of the base RF wave, γ is the electron gyromagnetic ratio for the magneto-optical defect center material, R(t) is the magnetic field proxy modulation and yR(t) is the biasing RF modulation. For a simple magnetic field proxy modulation, R(t) where bi is the strength of the proxy signal and f\ is the frequency of the proxy signal. In other

implementations, complex magnetic field proxy modulation scan be implemented where the strength, b(t), or frequency, fit), varies based on time or other variables. In implementations where the material is a diamond having nitrogen vacancies, the gyromagnetic ratio is

approximately 28 GHz/Tesla. The RF field is applied to the magneto-optical defect center material and an optical excitation source, such as a green laser light, is applied to the magneto- optical defect center material. As described below, the when excited by the optical excitation source, the magneto-optical defect centers generate a different wavelength of optical light, such as red fluorescence for a diamond having nitrogen vacancies. The system uses an optical detector to detect the generated different wavelength of optical light. In some instances, a filter may be used to filter out wavelengths of optical light than the wavelength of interest. The system processes the optical light, such as red light, emitting from the magneto-optical defect center material as if the base RF wave, F(t), was not modulated by the desired magnetic field proxy modulation, R(t). Accordingly, the desired magnetic field proxy modulation, R(t), will be present in the output and will appear as an additional reference magnetic field in addition to any other external magnetic fields to which the magneto-optical defect center material is exposed (e.g., the local Earth magnetic field and any other external magnetic fields). The detected optical signal representative of the applied desired magnetic field proxy modulation, R(t), will be

superimposed on top of any background environmental magnetic field signals present.

[0855] The use of the desired magnetic field proxy modulation, R(t), for the generation of precise proxy reference magnetic fields can be useful in a number of aspects. For instance, the technique does not incur alignment issues between a magnetic transmitter and the magneto- optical defect center material, does not incur drift of the magnetic transmitter, and does not require a magnetic transmitting coil to be integrated into a sensor head for real-time calibration purposes. In addition, the broadband response of the technique can allow for offline or real-time determination of a system transfer function over a magnetic frequency span of several orders of magnitude. The detected signal by the optical detector for the applied desired magnetic field proxy modulation, R(t), can then be used for base line compensation for the magneto-optical defect center sensor. In addition, the desired magnetic field proxy modulation, R(t), can be periodically used in real-time for the generated RF signal, G(t), for periodic compensation for drift, such as due to temperature fluctuations during operation. Moreover, the detected signal by the optical detector for the applied desired magnetic field proxy modulation, R(t), can be used as an initial pass/fail test for the magneto-optical defect center sensor based on if the detected signal by the optical detector for the applied desired magnetic field proxy modulation, R(t), is within a predetermined tolerance range.

[0856] FIG. 102 illustrates a magnetometry curve for an example resonance RF frequency. The magnetometry curve of FIG. 102 corresponds to a spin state transition envelope having a respective resonance frequency for the case where the diamond material has NV centers aligned along a direction of an orientation class. This is similar to one of the 8 spin state transitions shown in FIG. 5 for continuous wave optical excitation where the RF frequency is scanned. The magnetic field component, Bz, along the orientation class can be determined based on the resonance frequency relative to the zero external magnetic field frequency, such as 2.87 GHz, in a similar manner to that in FIG. 4B. In monitoring the magnetic field, the dimmed luminesc