CN112748378A - Quantum vector magnetometer based on nanoscale finned waveguide - Google Patents

Abstract

The invention relates to a device comprising: a substrate and a nanoscale fin, the substrate and the nanoscale fin being formed of a first material; an RF transmitter, the RF transmitter being at an energy in a radio frequency range; and a waveguide formed of the second material. The device further comprises a two-color directional coupler configured to couple the pump and probe lasers into the waveguide. The waveguide is positioned proximate to the nanoscale fin along a coupling length such that the pump laser light propagating within the waveguide is coupled into the nanoscale fin along the coupling length due to evanescent wave overlap. The pump laser causes the first material to absorb the probe laser when the energy emitted by the RF transmitter is at one or more frequencies that depend on the magnetic field. The apparatus also includes a processor configured to determine a magnetic field strength of the magnetic field based on the identification of the one or more frequencies.

Description

Quantum vector magnetometer based on nanoscale finned waveguide

Background

Many applications use accurate measurements of magnetic fields. In particular, applications attempt to measure vector magnetic field information to provide desired functionality within the system. For example, an application may measure magnetic fields in anomaly-based navigation and dipole beacon-based navigation. These applications typically require magnetic sensors with: high sensitivity; low size, weight and power; and the ability to operate in the field. Some technologies (e.g., superconducting quantum interference devices (SQUIDs) or atom-based magnetometry) can provide high sensitivity that can be used for certain applications. However, some of these techniques have drawbacks. For example, SQUIDs use cryogenic refrigeration, which increases the size and power consumption of magnetometers, and atomic-based magnetometers cannot operate in the earth's field. In addition, the aforementioned techniques use at least three sensors to provide vector information.

Disclosure of Invention

In one example, an apparatus includes: a substrate and a nanoscale fin, the substrate and the nanoscale fin being formed of a first material; a radio frequency transmitter that transmits energy in a radio frequency range; and a waveguide formed from a second material, wherein the waveguide is positioned on the nanoscale fin. The device further comprises a two-color directional coupler configured to couple the pump and probe lasers into the waveguide. The waveguide is positioned proximate to the nanoscale fin along a coupling length such that the pump laser light propagating within the waveguide is coupled into the nanoscale fin along the coupling length due to evanescent wave overlap. The pump laser causes the first material to absorb the probe laser when the energy emitted by the radio frequency transmitter is at one or more frequencies that depend on the magnetic field. The apparatus also includes a processor configured to determine a magnetic field strength of the magnetic field based on the identification of the one or more frequencies that depend on the magnetic field.

Drawings

Understanding that the drawings depict only some embodiments and are not therefore to be considered to be limiting in scope, the exemplary embodiments will be described with additional specificity and detail through use of the accompanying drawings in which:

FIG. 1 is a diagram showing transitions between various states of a particular material used to make a magnetometer;

FIG. 2 is a graph illustrating magnetic field detection based on identification of resonant lines in an applied microwave field;

FIG. 3 is a diagram showing a waveguide structure that can be used to detect a magnetic field;

fig. 4A to 4B are graphs showing the influence of different waveguide widths in a waveguide structure for detecting a magnetic field;

FIGS. 5A-5B are graphs illustrating the effect of different separation distances between a waveguide and a substrate in a waveguide structure for detecting a magnetic field;

fig. 6A to 6C are graphs showing the influence of the position along the coupling length of a waveguide in a waveguide structure for detecting a magnetic field;

FIG. 7 is a graph illustrating the effect of pump power on probe transmissions from a waveguide in a waveguide structure for detecting magnetic fields;

FIG. 8 is a diagram of a waveguide system for detecting a magnetic field;

FIG. 9 is a flow chart of an exemplary method for fabricating a waveguide structure for detecting a magnetic field; and

FIG. 10 is a flow chart of an exemplary method for fabricating a waveguide structure for detecting a magnetic field.

In accordance with common practice, the various features described are not necessarily drawn to scale, emphasis instead being placed upon particular features associated with the example embodiments.

Detailed Description

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific exemplary embodiments. However, it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made.

Systems and methods for integrated photonic quantum vector magnetometers are provided herein. In some examples, the magnetometer includes a waveguide structure including a waveguide positioned on a nanoscale fin formed from a wafer. Light from the pump laser is coupled into the waveguide, and the pump laser is coupled into the nanoscale fin along the length of the waveguide and the nanoscale fin through their proximity to each other. Furthermore, in the presence of a microwave signal, light from the probe laser is coupled into the waveguide and the pump laser is coupled into the nanoscale fin. At a particular frequency of the microwave signal, the probe laser light is absorbed by the material of the nanoscale fin, and from the frequency or frequencies at which the probe laser light is absorbed, the magnetic vector can be determined. The waveguide structures and systems described herein can be fabricated on bulk wafers without the more difficult thin film techniques described in the' 533 patent application.

FIG. 1 is a diagram showing transitions between various states of a particular material used to make a magnetometer. For example, some materials may have certain physical properties that allow the material to respond to a magnetic field. For example, the first material may be Nitrogen Vacancy (NV) diamond, silicon carbide with defect centers, or other materials with similar physical properties. As used herein, NV diamond may refer to a diamond material having a plurality of point defects, wherein the point defects include nearest neighbor pairs of nitrogen atoms and crystal lattice vacancies in place of carbon atoms.

As shown, the first material may have a ground state that is a spin triplet state. Specifically, the ground state may have multiple spin projections: a base antiparallel 101 for spin projection 0 and a base parallel spin 103 for spin projection of +/-1, where the base antiparallel spin 101 and the base parallel spin 103 are separated by a resonant frequency 121. For example, in the absence of a magnetic field, when the first material is NV diamond, the resonant frequency may be equal to 2.87 GHz. In addition, a point defect within the first material may be optically excited to a spin triplet excitation level by a spin conservation transition, wherein the triplet excitation level also has a plurality of spin projections: the excited antiparallel spin of spin projection 0 105 and the excited parallel spin of spin projection about +/-1 107. For optical excitation of point defects, the first material may be exposed to pump light having a specific frequency. For example, in NV diamond, a laser with a wavelength of 532nm can cause a spin-conservative transition from the base triplet state to the excited triplet state.

When the point defect within the first material is in an excited state, the defect may relax by radiative transition 115 or by intersystem crossing 117. When the point defect relaxes by radiative transition 115, the point defect may fluoresce and return to a base triplet state. For example, the NV diamond point defect may emit light at a wavelength of 637nm during the radiative transition 115. When the point defect relaxes through intersystem crossing 117, the point defect will not fluoresce and will transition to a resting state, which may be the resting ground state 111 or the resting excited state 109. In addition, when the point defect is in one of the resting states 109 and 111, the point defect can absorb the probe laser 119 having a specific frequency. For example, NV diamond point defects in the resting states 109 and 111 may absorb the probing laser 119 at a wavelength of 1042 nm.

In some examples, microwave frequencies may be applied to the first material to increase the rate of inter-system cross-over 117 compared to radiative transition 115. In the first material, the non-radiative intersystem crossing 117 may be strongly spin selective. For example, point defects with parallel spins 107 are more likely to experience intersystem crossing 117 to rest states 109 and 111. In contrast, a point defect with an excited antiparallel spin 105 is more likely to undergo radiative transition back to the base triplet state. To increase the probability of intersystem crossing, a microwave frequency may be applied to the first material, the microwave frequency being equal to the resonant frequency of the first material. For example, when the first material is NV diamond, the resonant frequency may be 2.87 GHz. Thus, applying a radio frequency of 2.87GHz to the first material may increase the probability of intersystem crossing 117 to the resting states 109 and 111.

In addition, when a microwave signal at a resonant frequency is applied to the first material, the probe laser 119 is more likely to be absorbed by the first material because the population of point defects in the first material in the resting states 109 and 111 is greater than the population of point defects when the first material is not exposed to RF energy at the resonant frequency. Thus, when the probe laser 119 is applied to the first material in the absence of a microwave signal at the resonant frequency, the probe laser 119 is absorbed by the first material having the smaller frequency. For example, when the NV diamond material is exposed to a microwave signal having a resonant frequency of 2.87GHz, the NV diamond material may begin to absorb the detection laser 119 at an increasing rate at a wavelength of 1042 nm.

In some examples, the resonant frequency of the first material may change in the presence of a magnetic field. For example, when a first material is exposed to a magnetic field, the zeeman effect may cause the resonant frequency to experience a shift that is proportional to the strength of the magnetic field experienced. In particular, in the presence of a magnetic field, the resonant frequency can be divided into two different resonant frequencies, wherein the difference between the two resonant frequencies is proportional to the magnetic field experienced. Thus, the resonant frequency of the point defect absorption probe laser 119 in the first material can be monitored to determine the strength of the magnetic field experienced by the first material.

In addition, the point defects within the first material may be in one of a plurality of different orientations. For example, when the first material is NV diamond, each point defect may be in one of four different orientations. In addition, the first material may have many point defects in each of four different orientations. Thus, when the probe laser 119 is applied to the first material, vector information of the magnetic field can be extracted from the first material. For example, when the first material is exposed to a magnetic field, the resonant frequency of the point defect may shift based on the orientation of the point defect relative to the experienced magnetic field. Thus, when the point defects in the first material are in a plurality of different orientations, the point defects in the first material may have a separate resonant frequency associated with each of the different orientations of the point defects. Thus, the vector information of the magnetic field can be determined by identifying which resonances correspond to different orientations of point defects in the first material. In some examples, a bias magnetic field may be applied to the first material to help determine which resonant frequencies are associated with particular orientations of point defects.

In the examples described herein, the first material may be incorporated within a magnetometer that exposes the first material to the pump light 113 to cause point defects within the first material to move to an excited triplet state. The magnetometer can also expose the first material to RF energy within a frequency range that includes the resonant frequency 121 of the first material, where the probability of intersystem crossing 117 to the resting states 109 and 111 increases at the resonant frequency 121, as described above. Additionally, the first material may be exposed to a probing laser 119, wherein the probing laser 119 is absorbed by the point defects in the lay-up states 109 and 111. Thus, the applied microwave signal may be swept through a series of frequencies to identify resonant frequencies associated with different orientations of point defects within the first material. The resonant frequency may be identified when the intensity of the applied probe laser light 119 passing through the first material decreases (thereby indicating that the applied probe laser light 119 is absorbed by a point defect within the first material). Based on the identified resonant frequency, the magnetic field experienced by the first material may be calculated by: high sensitivity to magnetic field variations; low size, weight and power; and robustness that may enable the use of the resulting magnetometer in many magnetic/aiding-based applications, such as in navigation.

FIG. 2 is a graph illustrating magnetic field detection based on identification of resonant lines in an applied microwave field swept through a range of frequencies. As described above, the first material may be exposed to a range of microwave frequencies, wherein the applied frequency range includes different resonant frequencies of the first material. In addition, the different resonant frequencies are associated with the strength of the magnetic field experienced by the first material. Additionally, the first material may have different resonant frequencies associated with different orientations of point defects within the first material.

As shown, fig. 2 shows various plots of the intensity of the probing laser emitted from the first material at different microwave frequencies applied to the first material for three different magnetic field strengths. For example, graph 201 shows the intensity of the emitted probing laser at different frequencies when the first material is not exposed to a magnetic field. When coupling light from the probe laser into the first material in the absence of an applied magnetic field, the first material may not experience a zeeman shift, and the probe laser may be absorbed at a single resonant frequency of the first material. Thus, the intensity of the light 201 may be reduced at a single resonant frequency of the first material.

In addition, when the first material is exposed to different magnetic field strengths, the resonant frequency may experience a frequency shift that is proportional to the magnetic field strength experienced. For example, graphs 205 and 203 show the intensity of the probing laser emitted by the first material in the presence of different magnetic field strengths. For example, the magnetic field strength experienced by the first material associated with plot 203 is greater than the magnetic field strength experienced by the first material associated with plot 205. Thus, the magnitude of the shift in resonant frequency is greater when the first material is exposed to a greater magnetic field strength. To identify the magnitude of the shift in the resonant frequency, the system may identify a frequency 207 associated with the decrease in intensity of the probing laser emitted by the first material. Based on the magnitude of the shift in the resonant frequency, the system can determine the magnetic field experienced by the point defect. In addition, when multiple resonant frequencies are present, the system can identify the orientation of point defects and the direction of the magnetic field experienced associated with the different resonant frequencies.

Fig. 3 is a diagram illustrating a waveguide structure 300 that may be used within a system for detecting a magnetic field. In the example shown in FIG. 3, the waveguide structure 300 includes a substrate 301, nanoscale fins 302, and a waveguide 304. In some examples, the waveguide structure 300 includes cladding material (not shown) that fills the empty spaces between the substrate 301, the nanoscale fins 302, and the waveguides 304 shown in fig. 3.

In some examples, the substrate 301 and the nanoscale fins 302 are formed from the first material described above. For example, the nanoscale fins 302 may be formed in an NV diamond substrate or other similar material using the techniques described below. In some examples, the waveguide 304 is formed of a second material different from the first material. The waveguide 304 is transparent at the pump and probe wavelengths and has a sufficiently high index of refraction such that it supports both the pump and probe optical modes. In an example where the first material is NV diamond, the second material is transparent at the pump wavelength (532nm) and the probe wavelength (1042nm) discussed above. In such examples, the refractive index of the second material should be greater than or equal to 2, and the refractive index will preferably be about 2.4 or higher. In some examples, the second material is titanium dioxide, silicon nitride, or another material that satisfies the above parameters.

The nanoscale fins 302 serve multiple purposes of the waveguide structure 300. The nanoscale fins 302 serve to separate the optical mode propagating in the waveguide 304 from the substrate 301. If the optical modes (pump mode and probe mode) are too close to the substrate 301, light may radiate down to the substrate 301 through the nanoscale fins 302. To provide sufficient spacing between the optical mode and the substrate 301, the height of the nanoscale fins 302 must be above a threshold height. In some examples, the height of the nanoscale fins 302 is about 3 microns or greater.

Furthermore, the nanoscale fins 302 are where absorption of the pump and probe lasers described above with respect to FIG. 1 occurs in the waveguide structure 300. In some examples, the waveguide 304 is positioned proximate to a top surface of the nanoscale fin 302 such that light propagating through the waveguide 304 is coupled into the nanoscale fin 302 due to evanescent wave overlap. For example, light from the pump laser may be coupled into the waveguide 304, and the pump laser is coupled from the waveguide 304 into the nanoscale fin 302 due to evanescent wave overlap. In some examples, the pump laser is configured to emit light at a frequency of the pump laser. For example, when the nanoscale fin 302 is formed from NV diamond, the pump laser may be a laser configured to emit light at a wavelength of 532 nm. Thus, as the pump laser light is coupled from the waveguide 304 into the nanoscale fin 302 due to evanescent wave overlap, the pump laser light can cause a point defect within the nanoscale fin 302 to transform into an excited triplet state.

In some examples, light from the probing laser is coupled into the waveguide 304 from a laser source. The detection laser may emit light having a wavelength that is absorbed by point defects in the first material in the lay-up state. For example, when the nanoscale fins 302 are made of NV diamond, the light from the probing laser may have a wavelength of 1042 nm.

When the waveguide structure 300 is exposed to a signal having the resonant frequency of the first material, the pump laser coupled into the waveguide 304 and gradually coupled into the nanoscale fin 302 due to evanescent wave overlap may cause point defects within the nanoscale fin 302 to move to a resting state. As the pump laser light is progressively coupled into the nanoscale fin 302 along the coupling length between the nanoscale fin 302 and the waveguide 304, the point defect may absorb the probe laser light along the coupling length in the presence of a signal having the resonant frequency of the first material. Additionally, since the resonant frequency of the first material changes upon exposure to a magnetic field, the frequency of the applied signal can be changed to identify the frequency at which point defects within the nanoscale fin 302 absorb the probing laser. As described above, different identified frequencies may be identified to determine the magnitude and direction of the magnetic field.

While the waveguide 304 appears uniform in fig. 3, it should be understood that this is for ease of illustration. In some examples, the physical characteristics (e.g., width) of the waveguide 304 and the relationship between the waveguide 304 and the substrate 301 and/or the nanoscale fins 302 may be modified such that the pump laser light is gradually coupled from the waveguide 304 into the nanoscale fins 302 due to evanescent wave overlap. In some examples, the width of the waveguide 304 is varied such that the pump laser light is gradually coupled into the nanoscale fin 302 along a coupling length through which the nanoscale fin 302 and the waveguide 304 are close to each other. In some examples, the physical relationship between the waveguide 304 and the substrate 301 and the nanoscale fin 302 is changed such that the pump laser light is gradually coupled into the nanoscale fin 302 along the coupling length through which the nanoscale fin 302 and the waveguide 304 are close to each other. Further, in some examples, the pump laser light is substantially coupled into the nanoscale fin 302 such that the pump laser light no longer propagates within the waveguide 304 after the coupled length of the nanoscale fin 302 and the waveguide 304. By gradually coupling the pump laser light from the second waveguide 304 into the nano-scale fin 302 due to evanescent wave overlap, the amount of point defects converted into excited triplet states in the nano-scale fin 302 increases.

As discussed with respect to fig. 3, the use of the waveguide structure 300 increases the interaction length of light within the first material. As discussed above, both the pump laser and the probe laser propagate in the waveguide. With the use of the nanoscale fins 302 and waveguides 304, the pump laser light can be slowly coupled into the nanoscale fins 302 due to evanescent wave overlap. In particular, the pump laser light is absorbed by the first material at a faster rate than the probe laser light is absorbed by the first material.

By slowly leaking the pump laser light into the nanoscale fin 302, the waveguide structure 300 may provide increased absorption of the probe laser light, resulting in greater contrast and efficient absorption of the pump laser light along the coupling length between the nanoscale fin 302 and the waveguide 304. As described below, light may be slowly coupled from the waveguide 304 to the nanoscale fins 302 in such a way that the pump laser light has a substantially constant intensity over the entire coupling length of the nanoscale fins 302.

Fig. 4A-4B are graphs illustrating the effect of different widths of waveguides in a waveguide structure (such as waveguide structure 300 in fig. 3) for detecting magnetic fields. In fig. 4A, various coupling coefficients of pump modes propagating in waveguides made of a second material having different widths are shown. For example, graph 401 shows the pump-mode coupling coefficients of a waveguide and nanoscale fins over various widths of the waveguide structure. In fig. 4B, various coupling coefficients of probe modes propagating in a waveguide 304 made of a second material having different widths are shown. For example, graph 402 illustrates the probe mode coupling coefficients of a waveguide and nanoscale fins across various widths of the waveguide structure. As can be seen from fig. 4A to 4B, the general trend of the pump mode coupling coefficient versus the waveguide width is similar to the general trend of the probe mode coupling coefficient versus the waveguide width.

Fig. 5A is a graph illustrating the effect of different separation distances between a substrate and a waveguide in a waveguide structure (such as waveguide structure 300 in fig. 3) for detecting a magnetic field. In fig. 5A, various coupling coefficients of pump modes propagating in 0.6 μm wide waveguides 304 made of the second material and separated from the substrate by various distances are shown. For example, graph 501 shows the pump mode coupling coefficients of a waveguide and a nanoscale fin over various separation distances between the substrate of the waveguide structure and the waveguide.

Fig. 5B is a graph illustrating the effect of different separation distances between a substrate and a waveguide in a waveguide structure (such as waveguide structure 300 in fig. 3) for detecting a magnetic field. In fig. 5B, various coupling coefficients of probe modes propagating in 0.6 μm wide waveguides 304 made of the second material and separated from the substrate by various distances are shown for various pump powers. For example, graph 502 shows the probe mode coupling coefficients for the waveguide and the nanoscale fin at a pump power of 8mW, graph 503 shows the probe mode coupling coefficients for the waveguide and the nanoscale fin at a pump power of 4mW, graph 504 shows the probe mode coupling coefficients for the waveguide and the nanoscale fin at a pump power of 2mW, and graph 505 shows the probe mode coupling coefficients for the waveguide and the nanoscale fin at a pump power of 1 mW. As can be seen from fig. 5A to 5B, the general trend of the pump mode coupling coefficient versus the separation distance is similar to the general trend of the probe mode coupling coefficient versus the separation distance.

As shown in fig. 4A-5B, the rate at which light is coupled from the waveguide 304 into the nanoscale fin 302 along the coupling length of the waveguide structure 300 depends on both the lateral width of the waveguide 304 and the vertical distance between the substrate and the waveguide 304 (the height of the nanoscale fin). Thus, to control the rate at which light is coupled from the waveguide 304 into the nanoscale fin 302 along the coupling length of the waveguide structure, the width of the waveguide 304 and/or the distance between the substrate 301 and the waveguide 304 (the height of the nanoscale fin 302) may be varied along the coupling length.

Fig. 6A-6C are graphs illustrating the effect of different locations along the coupling distance of a waveguide in a waveguide structure for detecting magnetic fields, such as waveguide structure 300 in fig. 3. In fig. 6A, various coupling coefficients of pump modes propagating at various locations along the coupling length of the waveguide in a waveguide 304 made of a second material are shown. For example, graph 601 illustrates the pump mode coupling coefficients of a waveguide and nanoscale fins over the coupling length of the waveguide structure. In fig. 6B, various coupling coefficients of a probe mode propagating at various positions along the coupling length of the waveguide in the waveguide 304 made of the second material are shown. For example, graph 602 shows the probe mode coupling coefficients of a waveguide and a nanoscale fin over the coupling length of the waveguide structure at a pump power of 8 mW.

Fig. 6C is a graph showing that the distance between the substrate 301 and the waveguide 304 varies along the coupling length of the waveguide 304 such that the pump absorption of the nanoscale fins is uniform. For example, graph 603 shows that the separation distance between the substrate 301 and the waveguide 304 decreases along the coupling length of the waveguide 304 such that the absorption of the pump laser light in the nanoscale fins is uniform.

Fig. 7 is a graph illustrating the effect of pump power on probe transmissions from a waveguide in a waveguide structure for detecting magnetic fields, such as waveguide structure 300 in fig. 3. In fig. 7, a graph 701 shows that probe transmission decreases with increasing pump power.

Fig. 8 is a diagram of a waveguide system 800 that can be used to detect a magnetic field. In the example shown in fig. 8, the waveguide system 800 includes a waveguide structure 802 that includes similar features as described above with respect to the waveguide structure 300, the waveguide structure 300 being described above with respect to fig. 3. In some examples, the waveguide system 800 includes an absorption region 801. As used herein, absorption region 801 may refer to a region within waveguide system 800 where the nanoscale fin and waveguide of waveguide structure 802 extend through a coupling length in close proximity to each other such that pump laser 807 and probe laser 809 introduced into the waveguide from the pump laser source and probe laser source, respectively, couple into the nanoscale fin due to evanescent wave overlap as described above.

In some examples, pump laser 807 and probe laser 809 are coupled into waveguide 802 via dichroic directional coupler 806. In the presence of the resonant frequency signal, the probe laser 809 may be absorbed by a point defect within the nanoscale fin, such that the power of the light received from the waveguide is reduced. To monitor the power of the probe laser 809 within the waveguide, the waveguide system 800 includes a filter 815. In some examples, a filter 815 is coupled to the waveguide structure 802 and is configured to receive light from the waveguide after the light has passed through the absorption region 801. In some examples, the filter 815 is configured to reflect light at the frequency of the probe laser light 809 through the reflection port 813 and allow light at other frequencies (such as the frequency of the pump laser light 807 or the fluorescence frequency) to pass through to the filter output port 811. The remaining pump laser light 807 (if any) passes through filter exit port 811 after leaving absorption region 801. In some examples, the power of the pump laser 807 at the filter exit port 811 may be substantially equal to or near zero because most of the pump laser 807 may be coupled into the nanoscale fin in the absorption region 801.

In some examples, the light at the reflective port 813 is coupled to a light detection device (such as a photodetector or camera) configured to monitor the intensity of the received light. During operation, microwave radiation may be emitted around the absorption region 801 where the microwave radiation is swept through a range of frequencies including the possible resonant frequencies of the first material. The light detection device may monitor the light received from the reflective port 813 and provide a signal associated with the intensity of the received light. In some examples, a processor (not shown) is configured to receive the signal from the light detection device and, when measuring the intensity of received light, correlate the intensity of received light with the frequency of the microwave radiation applied to the absorption region 801. In some examples, the processor is configured to execute computer-executable instructions that identify an applied frequency associated with the reduction in light intensity. In some examples, the processor may determine that the identified frequency is a resonant frequency and calculate the magnitude and direction of the magnetic field applied to the absorption region 801.

Fig. 9 illustrates an exemplary method 900 for fabricating a waveguide structure for detecting a magnetic field. The method begins by forming nanoscale fins in a wafer formed from a first material (block 902). In some examples, the first material may be nitrogen-vacancy (NV) diamond, silicon carbide, or other materials having similar physical properties. As used herein, NV diamond may refer to a diamond material having a plurality of point defects, wherein the point defects include nearest neighbor pairs of nitrogen atoms and crystal lattice vacancies in place of carbon atoms.

In some examples, forming the nanoscale fins in the wafer includes etching the wafer using, for example, reactive ion etching. In such examples, the wafer may be prepared for etching using photolithographic techniques. In some examples, the wafer is prepared as follows: depositing a photoresist layer on the wafer; patterning the photoresist layer using photolithography (e.g., electron beam lithography or UV lithography); and developing the photoresist layer. Once the nanoscale fins are sufficiently formed after the reactive ion etch, any residual photoresist is removed.

The method 900 continues with depositing cladding material over the nanoscale fins (block 904). In some examples, the cladding material has a low refractive index (e.g., silicon dioxide) compared to the wafer. In some examples, the cladding material is deposited using chemical vapor deposition or atomic layer deposition. In some examples, the cladding material is polished using chemical mechanical polishing to prepare the cladding material for further fabrication steps. In some examples, the cladding material is polished until the top surface of the nanoscale fins is exposed.

The method 900 continues with forming a waveguide on the nanoscale fin (block 906). In some examples, the waveguide is formed of a second material different from the first material. The waveguide is transparent at the pump and probe wavelengths and has a sufficiently high refractive index such that it supports both the pump and probe optical modes. In an example where the first material is NV diamond, the second material is transparent at the pump wavelength (532nm) and the probe wavelength (1042nm) discussed above. In such examples, the refractive index of the second material should be greater than or equal to 2, and the refractive index will preferably be about 2.4 or higher. In some examples, the second material is titanium dioxide, silicon nitride, or another material that satisfies the above parameters.

In some examples, forming the waveguide includes using, for example, reactive ion etching. In such examples, the waveguide material for etching may be prepared using photolithographic techniques. In some examples, the waveguide material is prepared as follows: depositing a photoresist layer on the waveguide material layer; patterning the photoresist layer using photolithography (e.g., electron beam lithography or UV lithography); and developing the photoresist layer. In some examples, the photoresist layer is removed after the reactive ion etch.

The method 900 continues with depositing cladding material over the waveguide (block 908) in a manner similar to that described above with respect to block 904.

In some examples, the method 900 continues with coupling the probe laser source and the pump laser source to the waveguide (block 910). For example, a probe laser source may be coupled to the waveguide and configured to emit probe laser light into the waveguide, and a pump laser source may be coupled to the waveguide and configured to emit pump laser light into the waveguide at a wavelength that causes the first material to absorb the probe laser light when the nanoscale fin is exposed to one or more resonant frequencies of the first material. In some examples, the detection laser source and the pump laser source are coupled to the waveguide using optical fibers and dichroic directional couplers. In such examples, the probe laser source and the pump laser source are coupled to respective optical fibers, which are then coupled to a dichroic directional coupler. The light from the probe laser source and the pump laser source is oscillated using a dichroic directional coupler such that substantially all of the light from the probe laser source and the pump laser source is coupled into the waveguide.

Fig. 10 illustrates an exemplary method 1000 for fabricating a waveguide structure for detecting a magnetic field, and depicts a cross-section of the waveguide structure during various steps of the method 1000.

In various aspects, the system elements, method steps, or examples described throughout this disclosure (e.g., a processor) may be implemented on one or more computer systems, Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), or similar devices including hardware executing code for implementing those elements, processes, or examples, which is stored on a non-transitory data storage device. These devices include or operate in conjunction with software programs, firmware, or other computer readable instructions for performing various methods, process tasks, calculations, and control functions for synchronization and fault management in a distributed antenna system.

The instructions are typically stored on any suitable computer storage medium for storing computer-readable instructions or data structures. Computer-readable media can be implemented as any available media that can be accessed by a general purpose or special purpose computer or processor, or any programmable logic device. Suitable processor-readable media may include storage or memory media such as magnetic or optical media. For example, the storage or memory medium may include a conventional hard disk, compact disk-read only memory (CD-ROM), volatile or non-volatile media such as Random Access Memory (RAM) (including but not limited to Synchronous Dynamic Random Access Memory (SDRAM), Double Data Rate (DDR) RAM, RAMBUS dynamic RAM (rdram), static RAM (sram), etc.), Read Only Memory (ROM), electrically erasable programmable ROM (eeprom), flash memory, and the like. Suitable processor-readable media may also include transmission media (such as electrical, electromagnetic, or digital signals) conveyed via a communication medium such as a network and/or a wireless link.

The methods and techniques described herein may be implemented in digital electronic circuitry, or in programmable processor (e.g., special purpose processor or general purpose processor such as a computer) firmware, software, or in combinations of them. Apparatus embodying these techniques may include appropriate input and output devices, a programmable processor, and a storage medium tangibly embodying program instructions for execution by the programmable processor. Processes embodying these techniques may be performed by: a programmable processor executes a program of instructions to perform desired functions by operating on input data and generating output. The techniques may be implemented advantageously in one or more programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Generally, a processor will receive instructions and data from a read-only memory and/or a random access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and DVD discs. Any of the foregoing may be supplemented by, or incorporated in, specially designed application-specific integrated circuits (ASICs).

Exemplary embodiments

Embodiment 1 includes an apparatus comprising: a substrate and a nanoscale fin, the substrate and the nanoscale fin being formed of a first material; a radio frequency transmitter configured to transmit energy in a radio frequency range; a waveguide formed of a second material; a two-color directional coupler configured to couple pump and probe lasers into the waveguide, wherein the waveguide is positioned along a coupling length proximate to the nanoscale fin such that the pump laser light propagating within the waveguide couples into the nanoscale fin along the coupling length due to evanescent wave overlap, wherein the pump laser light causes the first material to absorb the probe laser light when the energy emitted by the radio frequency emitter is at one or more frequencies that depend on a magnetic field; and a processor configured to determine a magnetic field strength based on the identification of the one or more frequencies that depend on the magnetic field.

Embodiment 2 includes the apparatus of embodiment 1, wherein the first material comprises nitrogen-vacancy diamond.

Embodiment 3 includes the apparatus of any of embodiments 1-2, wherein the second material comprises titanium dioxide.

Embodiment 4 includes the apparatus of any of embodiments 1-3, wherein the nanoscale fins have a height greater than or equal to about 3 microns.

Embodiment 5 includes the apparatus of any of embodiments 1-4, wherein a height of the nanoscale fins varies over the coupling length.

Embodiment 6 includes the apparatus of any of embodiments 1-5, wherein a height of the nanoscale fin increases over the coupling length.

Embodiment 7 includes the apparatus of any of embodiments 1-6, wherein a width of the waveguide varies over the coupling length.

Embodiment 8 includes a system comprising: a substrate and a nanoscale fin, the substrate and the nanoscale fin being formed of a first material; a radio frequency transmitter configured to transmit energy in a radio frequency range; a waveguide formed of a second material; a pump laser source configured to generate the pump laser light; a probe laser source configured to generate the probe laser light; a bi-color directional coupler coupled to the pump laser source and the probe laser source, wherein the bi-color directional coupler is configured to couple the pump laser and the probe laser into the waveguide, wherein the waveguide is positioned along a coupling length proximate to the nanoscale fin such that the pump laser propagating within the waveguide couples into the nanoscale fin along the coupling length due to evanescent wave overlap, wherein the pump laser causes the first material to absorb the probe laser when the energy emitted by the radio frequency emitter is at one or more frequencies that depend on a magnetic field; and a processor configured to determine a magnetic field strength based on the identification of the one or more frequencies that depend on the magnetic field.

Embodiment 9 includes the system of embodiment 8, wherein the first material comprises nitrogen-vacancy diamond.

Embodiment 10 includes the system of any of embodiments 8-9, wherein the second material includes titanium dioxide.

Embodiment 11 includes the system of any of embodiments 8-10, wherein the nanoscale fins have a height greater than or equal to about 3 microns.

Embodiment 12 includes the system of any of embodiments 8-11, wherein a height of the nanoscale fin varies over the coupling length.

Embodiment 13 includes the system of any of embodiments 8-12, wherein a height of the nanoscale fin increases over the coupling length.

Embodiment 14 includes the system of any of embodiments 8-13, wherein a width of the waveguide varies over the coupling length.

Embodiment 15 includes the system of any of embodiments 8-14, further comprising a filter coupled to the waveguide, wherein the filter is configured to output the probe laser light at a first output port of the filter and the pump laser light and the fluorescence light at a second output port of the filter.

Embodiment 16 includes the system of embodiment 15, further comprising a light detection device coupled to the first output port of the filter and the processor, wherein the light detection device is configured to monitor an intensity of the detection laser received from the filter and provide a signal associated with the intensity of the detection laser to the processor.

Embodiment 17 includes a method comprising: forming a nanoscale fin in a substrate of a first material; depositing cladding material on the nanoscale fin and the substrate; forming a waveguide from a second material, wherein the waveguide is positioned along a coupling length proximate to a top surface of the nanoscale fin such that light propagating within the waveguide is coupled into the nanoscale fin along the coupling length due to evanescent wave overlap; depositing the cladding material on the waveguide; coupling a probe laser source to the waveguide, wherein the probe laser source is configured to emit a probe laser into the waveguide; and coupling a pump laser source to the waveguide, wherein the pump laser source is configured to emit pump laser into the waveguide at a wavelength that causes the first material to absorb the probe laser when the waveguide layer is exposed to one or more resonant frequencies of the first material.

Embodiment 18 includes the method of embodiment 17, wherein the first material comprises nitrogen-vacancy diamond.

Embodiment 19 includes the method of any one of embodiments 17-18, wherein the second material includes titanium dioxide.

Embodiment 20 includes the method of any of embodiments 17-19, wherein the nanoscale fins have a height greater than or equal to about 3 microns.

Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.

Claims (3)

1. An apparatus (800) comprising:

a substrate (301) and a nanoscale fin (302), the substrate and the nanoscale fin being formed of a first material;

a radio frequency transmitter configured to transmit energy in a radio frequency range;

a waveguide (304,802) formed from a second material;

a bi-color directional coupler (806) configured to couple pump laser light (807) and probe laser light (809) into the waveguide (304,802), wherein the waveguide (304,802) is positioned proximate to the nanoscale fin (302) along a coupling length such that the pump laser light (807) propagating within the waveguide (304,802) couples into the nanoscale fin (302) along the coupling length due to evanescent wave overlap, wherein the pump laser light (807) causes the first material to absorb the probe laser light (809) when the energy emitted by the radio frequency emitter is at one or more frequencies that depend on a magnetic field; and

a processor configured to determine a magnetic field strength based on an identification of the one or more frequencies that depend on the magnetic field.

2. The apparatus (800) of claim 1, wherein a height of the nanoscale fin (302) varies over the coupling length, wherein a width of the waveguide (304,802) varies over the coupling length.

3. The apparatus (800) of claim 1, further comprising:

a filter (815) coupled to the waveguide (304,802), wherein the filter (815) is configured to output the probe laser light (809) at a first output port (813) of the filter (815) and the pump laser light (807) and fluorescence light at a second output port (811) of the filter (815); and

a light detection device coupled to the first output port (813) of the filter (815) and the processor, wherein the light detection device is configured to monitor an intensity of the detection laser light (809) received from the filter (815) and to provide a signal associated with the intensity of the detection laser light (809) to the processor.

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