WO2017015713A1 - Capteur pour mesurer une grandeur physique - Google Patents

Capteur pour mesurer une grandeur physique Download PDF

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Publication number
WO2017015713A1
WO2017015713A1 PCT/AU2016/050668 AU2016050668W WO2017015713A1 WO 2017015713 A1 WO2017015713 A1 WO 2017015713A1 AU 2016050668 W AU2016050668 W AU 2016050668W WO 2017015713 A1 WO2017015713 A1 WO 2017015713A1
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Prior art keywords
laser
sensor
drive
magnetic field
laser medium
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PCT/AU2016/050668
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English (en)
Inventor
Jan JESKE
Andrew Greentree
Jared Cole
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Rmit University
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Priority claimed from AU2015902991A external-priority patent/AU2015902991A0/en
Priority claimed from AU2015230816A external-priority patent/AU2015230816B2/en
Application filed by Rmit University filed Critical Rmit University
Publication of WO2017015713A1 publication Critical patent/WO2017015713A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/36—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using magnetic elements, e.g. magnets, coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/323—Detection of MR without the use of RF or microwaves, e.g. force-detected MR, thermally detected MR, MR detection via electrical conductivity, optically detected MR
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/0007—Applications not otherwise provided for
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/0014—Monitoring arrangements not otherwise provided for
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/24—Arrangements or instruments for measuring magnetic variables involving magnetic resonance for measuring direction or magnitude of magnetic fields or magnetic flux

Definitions

  • the present invention relates to a sensor for measuring a physical parameter.
  • the invention relates to a magnetometer or an electrometer having a laser medium.
  • Magnetic tomography The precise measurement of magnetic fields (magnetometry) has a variety of scientific applications including NMR detection and gravitational wave detection. More generally, it is an enabling technology for mining exploration, to detect gas, oil and mineral reserves, in airports for automated detection of plane movements with less building induced interference than radar, and in medicine for the detection of magnetic fields produced by the heart (magento-cardiography or "MCG”) or the brain (magento- encephalography or "MEG").
  • a sensor for measuring a physical parameter including: an optical cavity; a laser medium which together with the optical cavity has a laser threshold; a laser pump; and a radio-frequency (RF) drive applied to the laser medium, such that the laser threshold varies with a change in the physical parameter; wherein the RF drive is applied to the laser medium at or around a particular resonance frequency which varies depending on the physical parameter, such that depending on the value of the physical parameter, the RF drive induces transitions between at least two states of the laser medium, each state causing a different laser threshold in an intensity of a laser output; and wherein the intensity of the laser output provides a measurement of the value of the physical parameter.
  • RF radio-frequency
  • the laser pump is a light source, typically in or close to the visible range, or electrical pumping applied to the laser medium.
  • the laser pump lifts single atoms or single colour centres of the laser medium into an energetically higher lying excited state, from which the laser medium returns to an energetically lower lying state.
  • the energy difference between the two states of the laser medium is emitted as a photon, i.e. light.
  • the photon is created with a wavelength and energy corresponding to the energy difference of the two states.
  • the laser output may be directly fibre-coupled, i.e. directed into and guided through an optical fibre. This allows the laser output to be guided, for example towards a light detector, which makes it possible to move the sensor around.
  • the laser pump signal and its fluctuations may be monitored and used in combination with the laser output signal to reduce technical noise.
  • the RF drive and its fluctuations are monitored and applied together with a laser output signal to reduce technical noise.
  • the minimisation of technical noise enables more accurate measurements.
  • the laser medium is a solid-state material. Solid-state materials are a reliable option for the laser medium due to their density of emitters, thermal capacity, ease of fabrication and robustness.
  • NV nitrogen-vacancy
  • the NV centre laser pumping typically occurs from the electronic ground state triplet 3A2 to the electronic excited state triplet 3E.
  • the states with different levels of brightness, may be at least two out of the three states of the ground state triplet 3A2.
  • at least one of the transitions between the 3E states and the phonon-added states of the 3A2 are used as a lasing transition.
  • Suitable solid-state materials for forming the laser medium are silicon-vacancy centres in diamond or Cerium in Yttrium- Aluminium-Garnet.
  • the senor achieves a sensitivity better than nT/V(Hz).
  • Ideal sensitivity can be achieved by optimisation of various operational parameters.
  • the optical cavity includes a diffraction grating.
  • the diffraction grating tunes the optical cavity to be resonant to one or more particular wavelengths which correspond to a particular transition of the laser medium.
  • the physical parameter is selected from any one of: an external magnetic field; an external electric field; a temperature; or a pressure.
  • the sensor is referred to as a "laser threshold magnetometer”.
  • the sensor is referred to as a "laser threshold electrometer”.
  • a sensor for measuring an external magnetic field including: an optical cavity; a laser medium which together with the optical cavity has a laser threshold; a laser pump; and a radio-frequency (RF) drive applied to the laser medium, such that the laser threshold varies with a change in the external magnetic field; wherein, the RF drive is applied to the laser medium at or around a particular resonance frequency which varies depending on the external magnetic field, such that depending on the strength of the external magnetic field, the RF drive induces transitions between at least two states of the laser medium, each state causing a different laser threshold in an intensity of a laser output; and wherein the intensity of the laser output provides a measurement of the strength of the external magnetic field.
  • RF radio-frequency
  • a method for measuring the strength of an external physical parameter including the following steps: (a) providing a sensor including a laser pump and a laser medium which together with an optical cavity forms a laser threshold; (b) applying a radio-frequency (RF) drive to the laser medium, such that the laser threshold varies with a change in the external magnetic field; wherein, the RF drive is applied to the laser medium at or around a particular resonance frequency which varies depending on the external magnetic field, such that depending on the strength of the external magnetic field, the RF drive induces transitions between at least two states of the laser medium, each state causing a different laser threshold in an intensity of a laser output; and (c) detecting the intensity of the laser output, wherein the intensity of the laser output provides a measurement of the strength of the external physical parameter.
  • RF radio-frequency
  • the method may further include the step of determining the laser output and a sensitivity of the sensor as a function of a plurality of parameters from a steady-state solution to a plurality of differential equations relating to the sensor, wherein a laser pump strength is set to an operating point which is determined from the laser output as a function of the laser pump strength and the sensitivity of the sensor is optimised as a function of a remainder of the plurality of parameters within predefined constraints.
  • the method further includes the step of determining a sensor measurement range as a range of detuning between an RF addressed transition frequency and an RF drive frequency above which the output changes as a function of detuning.
  • the laser output is plotted as a function of detuning (or as a function of the physical parameter to be measured) and the sensor measurement range is given by the width of a dip (or peak), typically around zero.
  • the sensor measurement range can accordingly be readily determined for a given set of parameters.
  • the range of possible parameters for a laser threshold sensor is given by the range of parameters for which the laser output as a function of (positive) laser pump strength has a region of non-negative values, i.e. a positive gradient.
  • a combination of a density of optically active atoms or color centres and a coherence time of the RF addressed transition is selected based on an optimal sensor sensitivity and/or sensor measurement range.
  • optimisation maximum power might place restrictions on the possible range of laser pump rates and/or RF drive strength and a given target of homogeneous power distribution in the laser medium might place restrictions on the range of possible densities of optically active atoms or colour centres.
  • the loss rate of the cavity is chosen based on the optimal sensor sensitivity and/or sensor measurement range given previous choices of parameters and/or given an optimisation of other parameters.
  • the cavity loss rate can be adapted via the choice of transmittance of the cavity mirrors, i.e. the fraction of light which is transmitted rather than reflected.
  • the above mentioned parameters are used in the construction of a laser threshold sensor. The subsequently mentioned parameters relate to calibration of the laser threshold sensor.
  • a RF drive strength is selected based on the optimal sensor sensitivity and/or sensor measurement range. Maximal power may restrict the possible range of RF drive strengths.
  • a laser pump strength may be set to the operating point, wherein the operating point is given by the highest laser threshold as a function of detuning. For laser media where the laser pump together with the internal decay structure drives towards the brighter state, the operating point is given by the laser threshold at zero detuning.
  • the laser pump strength can be set slightly above the operating point to achieve stability and robustness against technical noise. Alternatively, the laser pump strength can be set to a different value below the operating point to achieve better sensitivity over a smaller measurement range.
  • FIG. 1 is a schematic representation of the states of an NV centre as an example of a suitable laser medium according to an embodiment of the present invention.
  • FIG. 2 is a schematic representation of the laser threshold sensor.
  • FIG. 3 is a schematic representation of a laser cavity which includes a diffraction grating.
  • FIG. 4 is the solution to the equation in para [0063].
  • FIG. 5 is a plot showing the laser output power as a function of the laser pump rate for an exemplary laser magnetometer based on NV centres according to an embodiment of the present invention.
  • FIG.6 is a plot showing the laser output power as a function of the laser pump rate and detuning, i.e. the frequency difference between the RF drive and the lasing transition according to an exemplary embodiment.
  • FIG. 7 is another plot showing the laser output as a function of detuning, for several examples of laser magnetometer based on NV centres with different parameters.
  • FIG.s 9A to 9D there are shown corresponding plots of the pump laser irradiance in Watt/mm2.
  • FIG. 10 is a plot showing the sensitivity for measuring magnetic fields as a function of the magnetic field strength for several examples of laser magnetometer based on NV centres with different parameters.
  • FIG. 1 1 is a plot showing the alternative measurement modality to achieve very good sensitivity: (a) Sensitivity as a function of magnetic field strength, (b) laser output as a function of magnetic field strength, and (c) enlargement of the highly sensitive magnetic field range.
  • FIG. 12 is another plot showing the sensitivity for measurements of an oscillating field as a function of frequency.
  • FIG. 13 is a schematic representation of the states of a Cerium in YAG centre as an example of a suitable laser medium according to an embodiment of the present invention. Detailed Description
  • laser threshold refers to the point of laser pumping above which the laser turns on, and below which the laser turns off. “On” means that self-sustained lasing occurs and coherent laser light is emitted continuously.
  • a "laser” as referred to herein, consists of at least a laser medium, a cavity and a laser pump, which is typically a light source or electrical pumping, which is applied to the laser medium.
  • a "radio-frequency drive” or “RF drive” as referred to herein is an antenna or wire emitting electro-magnetic waves in the radio-frequency region.
  • the term "resonance frequency" as used throughout this specification with respect to a laser medium is intended to refer to a transition frequency corresponding to the energy difference of at least two states of the laser medium. If an external drive at that frequency is applied to the laser medium it induces transitions between those (at least) two states. For any transition the resonance frequency is the centre frequency of a resonance peak. The peak width of the resonance peak is referred to as the broadening of the transition.
  • vibronic states refers to the states with added phonons, which are very short-lived.
  • a laser consists of at least a laser medium, a cavity and a laser pump, which is typically a light source, typically in or close to the visible range or electrical pumping, which is applied to the laser medium.
  • the laser pump lifts single atoms or single colour centres of the laser medium into an energetically higher lying excited state. From this excited state the laser medium returns to an energetically lower lying state; the energy difference is emitted as light (a photon).
  • the photon is created with a wavelength and energy corresponding to that energy difference of the two states.
  • the lower lying energy state has multiple states slightly higher in energy because they have an additional phonon (vibrational quantum).
  • the photon that is created can have a range of different wavelengths, the so-called phonon sidebands.
  • Spontaneous emission emits photons over this range of wavelength.
  • Stimulated emission emits photons in only one wavelength (i.e. a much smaller range of wavelengths), namely that wavelength of the strong field which creates stimulated emission. This wavelength corresponds to one particular transition in the laser medium. This transition is called the lasing transition.
  • the process of pumping to an excited state followed by the emission of a photon is continuously repeated by the atoms or colour centres of the laser medium.
  • the photon emission can either be spontaneous emission or stimulated emission. Stimulated emission occurs when a light field interacts with the atom or colour centre and is more likely the stronger the light field; the emitted photon under stimulated emission has the same wavelength, phase and spatial mode as the strong light field.
  • the laser cavity essentially consists of at least two mirrors surrounding the laser medium, one of which is partially transmitting. The emitted light is reflected back and forth between the mirrors and builds up a light field which in turn creates stimulated emission. This light field continuously gains photons from the laser medium but also continuously loses photons due to the partially transmitting mirror.
  • Lasing is achieved, when the stimulated emission becomes strong enough to counteract the cavity loss and builds up a strong light field inside the cavity.
  • the laser threshold or lasing threshold When the laser pump strength is above the laser threshold lasing is achieved, i.e. the laser turns on. This is because the light field inside the cavity is strong and creates stimulated emission. Some of this light is transmitted through the partially transmitting mirror and creates the laser beam of light, i.e. the laser output.
  • An atom or colour centre has separate states with different energies.
  • a transition between at least two states can be induced by applying electromagnetic waves to the atom or colour centre, with a frequency which corresponds to the energy difference between those states. Since inducing transitions is dependent on applying a particular frequency it is a resonance phenomenon. Transitions between states with different spin are typically induced by frequencies in the radio-frequency (RF) range. This is called magnetic resonance. States with different spin also have an energy difference (and hence a resonance frequency) which is dependent on the value of a physical parameter. Inducing transitions is therefore dependent both on the frequency and the physical parameter.
  • the physical parameter may, for example, be an external magnetic field, an external electric field, temperature, or pressure. It will be understood by those skilled in the art, that whilst this invention is described largely in the context of a laser threshold sensor to measure an external magnetic field, the principles detailed herein are equally applicable to measurement of other quantities or physical parameters which effect transitions between states with different spin.
  • Magnetic resonance is used widely for example in medical imaging and spectroscopy.
  • the transitions can be detected by measuring the brightness. This is called optically detected magnetic resonance (ODMR).
  • ODMR optically detected magnetic resonance
  • the present invention combines the principles of lasing and magnetic resonance to create a laser threshold sensor with exceptional sensitivity.
  • a laser with a particular laser medium is combined with an RF drive in such a way that the laser threshold shifts when the physical parameter changes.
  • a laser medium must satisfy three requirements.
  • the first requires that the laser medium has at least two states with an energy difference which changes with the external magnetic field to be measured (or more generally: with the external quantity to be measured). For example different spin states have an energy difference which changes with the magnetic field.
  • the RF drive is applied to the transition between these states.
  • the second requires that the at least two states which are addressed by the RF drive have different brightness under laser pumping.
  • the difference in brightness means that depending on the resonance of the RF drive there are different gains into the cavity, which shifts the laser threshold.
  • the third requires that the laser pump together with the internal decay structure of the laser medium drives the laser medium preferentially into one of the two RF addressed states which have different brightness. This way the laser pump and the RF drive work against each other and off-resonant RF driving results in the laser medium being driven into the preferential state (which is defined by the laser pump and the internal decay structure) rather than staying in an arbitrary state. Only on-resonant RF driving creates a transition into the non-preferential state.
  • the third feature is often equivalent to (and therefore present in materials which have) a mechanism of optical initialisation in the context of qubits.
  • Solid-state materials are often a good choice for the laser medium due to their density of emitters, thermal capacity, ease of fabrication and robustness.
  • One example of a suitable solid-state laser medium satisfying the foregoing requirements are nitrogen-vacancy colour centres (NV centres) in a diamond crystal. This is a diamond impurity that can be naturally found, or more commonly grown into synthetic diamonds.
  • the suitability of the NV centre as a laser medium is due to the fact that the parameters of the NV centre are well defined and it has a spin dependent fluorescence, i.e. it emits different amounts of light depending on the spin state it is in.
  • the laser threshold is determined by the number of photons which are emitted on the lasing transition relative to the number of photons lost from the cavity. The fraction of photons lost is determined by the transmittance of the mirrors and unwanted scattering processes.
  • the number of photons emitted on the lasing transition is determined by the number of atoms or colour centres, the strength of the laser pump and the probability of photon emission into the cavity mode (i.e. the brightness of the lasing transition) of one atom or colour centre for a given laser pump strength. That means that the laser threshold changes when the brightness of the laser medium on the lasing transition changes (for fixed laser pump strength).
  • a physical parameter e.g. an external magnetic field
  • changes the energy difference i.e. resonance frequency between two states. If the RF drive frequency is fixed, the external magnetic field shifts the RF drive on and off resonance, which determines the relative probability of the state that the laser medium is predominantly in.
  • the different states are associated with different brightness, which creates a different lasing threshold. Therefore the lasing threshold changes with the external magnetic field. This means that the laser output provides a measurement of the magnetic field.
  • a measurement can be obtained in different ways.
  • One way is to sweep through the RF frequency and to record the laser output as a function of the RF frequency. This provides a plot with at least one resonance peak (or dip, i.e. inverted peak). The position of that at least one peak yields information about the quantity or physical parameter to be measured, or more specifically, the external magnetic field. In cases where there are several peaks their relative position, height and width can provide further information. For example for laser media with branching ratios, which depend on the orientation of the magnetic field the relative height of different peaks can yield precise information about the orientation of the magnetic field.
  • Sweeping the RF frequency has the advantage of recording a spectral profile, which can either be advantageous to determine a resonance frequency to very high precision or is particularly advantageous, in cases where the additional information is in the spectral profile, such as cases with several peaks.
  • Another way of obtaining a measurement is by fixing the RF drive to a certain frequency. This has the advantage, that the laser output measurement can be obtained either much faster (since it is not necessary to scan the RF frequency range) and/or to higher precision at the fixed RF frequency (since the laser output intensity can be measured for longer).
  • FIG. 1 there are shown the relevant states 100 of an NV centre, which is an exemplary laser medium for laser threshold magnetometry.
  • the vertical height implies the relative energy level of the state 100.
  • the downwards pointing arrows 1 10 represent internal decay rates of the NV.
  • the RF drive addresses transitions between states 1 and 4 (two- way horizontal arrow 120).
  • the laser pump lifts the NV from the lower lying energy state 1 or 4 to the excited state 2 and 5 (upwards arrows 130), often via phonon-added states above 2 and 5.
  • the lasing transition (arrows 140) is chosen between the excited state and a phonon-added state.
  • the intrinsic asymmetry created by the transitions L57 and L71 ensures that under continuous laser pumping (without the RF drive) the system is driven towards the spin 0 manifold.
  • the decay rate L57 also means that the likelihood of emitting a photon from state 5 is lower than from state 2, i.e. that the spin manifolds have different brightness.
  • FIG. 2 there is shown the configuration of a laser threshold sensor 200 showing the primary components.
  • a laser medium 210 is positioned inside a cavity 220, a laser pump 230, an RF drive 240 (e.g. a wire or coil). Above the laser threshold, stimulated emission from the laser medium occurs. At equilibrium there are n photons of the same wavelength, emitted from the lasing transition occurring inside the cavity 220.
  • a partially transmitting mirror 260 lets a certain fraction of the photons escape the cavity 220. These escaping photons form the laser beam 250, i.e. the laser output.
  • a population inversion is necessary, i.e.
  • the laser medium 210 needs to be more likely in the upper state of the lasing transition than the lower state of the lasing transition.
  • the fast spontaneous decay from the excited state to the ground state in many laser media 210 makes population inversion on the transition between the excited and ground state very difficult because the laser pump 230 has to be strong enough to counteract the spontaneous decay.
  • the lasing transition can be chosen to be between the excited state and a phonon-added ground state. This means that for lasing population inversion between the phonon-added ground state and the excited state is necessary instead of population inversion between the absolute ground state and the excited state. Since the phonons decay very quickly the population in the phonon-added ground state is very small and population inversion can be achieved much more easily.
  • the lasing transition is ideally chosen between the excited state and that phonon-added ground state which has the strongest transition, i.e. is the brightest. This transition is given by the peak of the phonon-sideband, which for the example of an NV centre is at approximately 700nm and corresponds to the three-phonon-added ground state.
  • any of the phonon added states could be used.
  • the NV centre laser pumping occurs from the electronic ground state triplet 3A2 to the electronic excited state triplet 3E, where A1 , A2, and E refer to the group theoretical irreducible representations of the C3V symmetry group of the NV centre.
  • the states with different levels of brightness are at least two out of the three states of the ground state triplet 3A2.
  • At least one of the transitions between the 3E states and the phonon-added states of the 3A2 are used as a lasing transition.
  • the cavity 220 can be chosen resonant to that transition optionally with the help of a diffraction grating as shown in FIG. 3.
  • Light that hits the grating 300 is diffracted towards different angles 310 and 320 corresponding to different wavelengths. Therefore only certain predetermined wavelength or wavelengths 320 are reflected back into the cavity by grating 300. That is, the cavity is only resonant to that particular wavelength.
  • a diffraction grating 300 can therefore be used to tune the resonance of a cavity to a (or several) particular wavelength, corresponding to a particular transition of the laser medium 330.
  • Lasing (population inversion) on the transition of states 1 to 2 and 4 to 5 is close to impossible due to the fast decay. Lasing on the transition 2 to 3 and 5 to 6 is achievable because the fast decay rates L31 and L64 ensure that the population in states 3 and 6 is low.
  • the lasing threshold is lowered to an achievable value by decreasing the laser cavity loss rate, increasing the number of atoms or colour centres, and choosing a laser medium with a low decoherence rate and relaxation rate on the RF addressed transition.
  • the cavity loss rate is decreased by reducing the transmission of the cavity mirrors as well as minimising scattering and losses inside the cavity.
  • a diamond with high NV density (and/or a large diamond volume) but also with a long inhomogeneous coherence time T2 * is advantageous.
  • a long coherence time can be achieved by using isotopically purified diamond and ensuring a high conversion efficiency from N to NV for example by appropriate annealing.
  • Qualitative details and quantitative details for the example of NV centres in diamond) to achieve lasing follow further below.
  • p is the diagonal density matrix element corresponding to state j of FIG. 1
  • p 14 is the off-diagonal density matrix element between states 1 and 4, the represent the effective incoherent pumping rates from the green laser pump, which model the coherent excitation to a phonon-added state just above states 2 and 5, followed by a rapid decay into states 2 and 5.
  • the L jk are the incoherent decay rates within the NV centre and the G jk the coherent (cavity induced) transitions.
  • the strength of the RF drive is given by ⁇ , which is the Rabi frequency, which has detuning ⁇ , whilst ⁇ 14 is the ground-state decoherence.
  • Equations 1 (and similar equations for any other laser medium) are non-linear if n is considered a variable.
  • a solution as a function of time can be obtained numerically for any example, where all parameters are set to numerical values.
  • An analytical solution can be obtained for the steady-state solution (i.e. all time-derivatives are zero).
  • n can be assumed to be constant.
  • the differential equations for the density matrix elements as a function of n are then linear equations and can be written as a matrix multiplication, where the matrix contains only the coefficients. These linear equations are solved analytically by diagonalisation of the matrix or solving for the nullspace of the matrix.
  • the unnormalised steady state solution for the density matrix elements in Equations 1 is:
  • Equation 3 (or a similar equation for any other laser medium) is a single equation for a single variable and does not contain any derivatives of that variable any more. It can be solved numerically by well-known numerical routines. It can be solved analytically by appropriate analytical routines, such as 'Solve' in 'Wolfram Mathematica'. The analytical solution to Equation 3 is shown as FIG. 4.
  • the expression allows calculation of the laser threshold and the laser output as a function the external magnetic field to be measured for any set of given parameters.
  • the laser output P out in Watt is linearly proportional to n. It is given by: where N at is the number of optically active atoms or colour centres inside the cavity, v 23 the transition frequency corresponding to the energy difference between the states 2 and 3, as well as 5 and 6, referring to FIG. 1 .
  • Equation 5 can be solved both analytically and numerically in the same way as Equation 3.
  • NV centres in diamond are utilised as the laser medium.
  • the intrinsic decay rates of NV centres in diamond are known in the literature:
  • ⁇ is the wavelength of the emitted light in the medium
  • ⁇ ⁇ 23 is the width of the atomic transition
  • V c is the cavity volume.
  • the dephasing is set by the inhomogeneous coherence time T 2 .
  • T 2 the inhomogeneous coherence time
  • FIG. 5 there is shown a plot representative of an example of a laser threshold magnetometer based on NV centres with the parameters described above.
  • the plot 500 shows the laser output power 510 as a function of laser pump rate 520 with on-resonant RF drive 530 and off- resonant RF drive 540.
  • the laser threshold is the point where the laser output starts to be non-zero 550 and is visibly shifted between the on-resonant RF drive curve 530 and off-resonant RF drive curve 540.
  • the laser threshold of the on-resonant RF drive curve 530 is a good choice for an operating point, i.e. the RF drive can be set fixed to this strength.
  • That operating point means that any external magnetic field causes non-zero detuning and therefore turns the laser on with a particular laser output.
  • the RF drive strength is chosen as 3.67MHz in the plot shown in FIG. 5.
  • FIG. 6 there is shown another plot 600 representative of the laser threshold magnetometer shown in FIG. 5, showing the laser output 610 as a function of the laser pump rate 620 and detuning 630.
  • the on-resonant RF drive 530 and off-resonant RF drive 540 curves of FIG. 5 are contained in this plot and indicated by horizontal lines 640 and 650 respectively.
  • the magnetic field changes the laser output along the vertical line 660.
  • FIG. 7 is shown another plot 700 representative of the laser threshold magnetometer shown in FIG.s 5 and 6, showing the laser output 710 as a function of detuning 720 (set by the magnetic field).
  • the solid line 750 is contained in FIG. 6 as vertical line 660. The other two lines have different laser pump rates and RF drive strengths as given.
  • FIG. 5 shows how the lasing threshold is shifted with detuning (i.e. the difference) between the frequency of the RF drive and the corresponding transition frequency set by the external magnetic field.
  • detuning i.e. the difference
  • An efficient way to operate the laser threshold magnetometer is to set the RF drive to a fixed frequency which corresponds to the zero-field splitting, i.e. set the RF drive to the frequency, which is on-resonance with the transition in the absence of any external magnetic field. Any detuning is then purely determined by the external magnetic field to be measured.
  • an efficient way of operation is to also set the laser pump rate to a fixed value, referred to as the operating point.
  • a good choice for this operating point is the highest laser threshold, which occurs for zero detuning (see FIG. 5).
  • Zero detuning corresponds to zero external field when the RF drive frequency is set to the zero-field splitting.
  • This choice of RF drive frequency means that any external magnetic field causes detuning, which means that the laser threshold is shifted below the operating point and the laser turns on with a laser output unique to that magnetic field strength. The laser output then provides a direct measurement of the external magnetic field.
  • the external magnetic field uniquely determines the laser output, i.e. a certain laser output will provide a direct measurement of the magnetic field.
  • the connection between magnetic field and laser output can be seen in FIG. 7.
  • FIG. 7 shows that the laser output varies from its maximum value all the way to zero, i.e. provides a strong response to the magnetic field and excellent contrast. This is a distinct advantage of laser threshold magnetometry over other measurement techniques, such as ODMR or any other magnetometry schemes with NV centres.
  • the measurement is simply obtained by measuring the laser output for a certain measurement time.
  • the laser output changes with the magnetic field over the measurement range in a known fashion (see details for NV in FIG. 4 or the example in FIG. 7), such that a particular measurement value of the laser output converts to a particular value of the magnetic field.
  • To measure a constant magnetic field the constant laser output is measured. Measurement of oscillating magnetic fields is described further below.
  • the precision of measurement is determined as the smallest magnetic field value to which the measurement is correct.
  • Ultra-high precision means that the magnetic field value to which the measurement is correct is ultra-low, i.e. the values of the sensitivity are ideal when they are extremely low.
  • the precision will be given by a magnetic field strength (in Tesla) to which the measurement is precise.
  • This precision value is smaller (i.e. better) the longer the measurement lasts for and decreases with a factor of 1/V(T), where T is the measurement time.
  • the sensitivity is simply defined by the product of the measurement precision multiplied with V(T) as:
  • the sensitivity quantifies how precise the laser threshold magnetometer (or any magnetic field sensor) is and is measured in Tesla*V(second), or equivalently Tesla/V(Hertz). For measurements of a constant magnetic field B the sensitivity can be calculated as:
  • Equation 1 1 the derivative can be calculated as:
  • the first term defines how the physical parameter to be measured changes the RF addressed transition frequency (and for fixed RF drive frequency therefore the detuning) and the second term can be calculated from the solution for n as a function of the detuning. If the physical parameter B to be measured is the magnetic field the first term becomes the magnetic dipole moment of the RF addressed transition and (for a transition where m s changes by one) is given by:
  • the offset n 0 is given by the DC response (FIG. 4) to the RF drive detuning in the absence of oscillations and the derivative can be calculated using the derivative of the DC response at the
  • the AC sensitivity can also be determined via a numerical simulation of the response based on the differential equations for the laser threshold magnetometer wherein the amplitude n s and the offset n 0 are determined numerically and can be determined numerically from by simulating several detunings. This was done for FIG. 12 and confirmed Equation 14 for the region where the frequency is below the response time.
  • FIG.s 8A to 8D a number of plots are provided containing information as to how lasing can be achieved as well as information as to how good sensitivity can be achieved.
  • the DC sensitivity is shown as a function of the cavity loss rate ⁇ and the RF drive strength ⁇ for several different combinations of the number of NV centres inside the cavity and the coherence time T2 * (which is the inverse of the dephasing rate
  • the plots provide information about which sensitivity is achieved for any set of parameters.
  • FIG.s 8A to 8D show the sensitivity plots followed by FIG.s 9A to 9D which show the pump laser irradiance plots for the same parameters.
  • the dots within the plots are the result of failures of the numerical algorithm and can be ignored.
  • FIG.s 8A to 8D are based on Equation 1 1 and FIG. 4 and assume the internal decay rates of the NV centre as given above and always set the laser pump rate to its respective operating point, which is determined as the laser threshold (i.e. the root of n as a function of the laser pump rate) for zero detuning.
  • the volume of the laser medium and cavity are assumed as given above but changes to either values have clear effects and can be optimised as given further below.
  • FIG. 10 there is shown a plot 1000 of several examples of a laser threshold magnetometer based on NV centres with different parameters.
  • Curves 1010, 1020 and 1030 correspond to curves 750, 740 and 730 respectively for the same parameters as in FIG. 7.
  • Curve 1040 is for parameters chosen to achieve ultra-high precision, i.e. extremely low sensitivity values.
  • the parameters chosen are an NV density of 16ppm, coherence time of 0.181 microseconds, cavity loss rate of 63.1 GHz, laser pump rate of 10.4MHz and RF drive strength of 6.14MHz.
  • the cavity loss rate is a parameter set in the construction of the laser threshold sensor, specifically the cavity.
  • the RF drive strength i.e.
  • Rabi frequency is a calibration parameter, which can easily be adjusted after construction for different measurements with the same laser threshold sensor. It can make sense to adjust both the RF drive strength as well as the laser pump to achieve either good sensitivity or wide measurement range.
  • Plots such as FIG. 7 and FIG. 10 can be produced for any set of parameters and show how the calibration parameters can be chosen to optimize either for sensitivity or measurement range.
  • the laser pump strength is set to the respective operating point, which can be seen by the fact that the laser output power is zero if and only if the detuning is zero.
  • the plots in FIG.s 8A to 8D also provide information for which parameters NV laser threshold magnetometry is possible at all.
  • the cavity loss rate gets too large or the number of NV centres too small then lasing cannot be achieved. This can be seen by the black regions to the right hand side of the plots, where the cavity loss rate is too large for lasing. For the parameters in these regions lasing is not achieved, i.e. these parameters are not suitable to build a laser threshold magnetometer. It can be seen that for smaller numbers of NV centres the edge of this region moves further left, i.e. towards smaller cavity loss rates. This is because for lower numbers of NV centres lasing is harder to achieve and a lower cavity loss rate is necessary.
  • Isotopic purification of the diamond can help to increase the coherence time without reduction of the NV density. Maximising the conversion efficiency from N impurities to NV centres by ideal radiation and annealing conditions increases the NV density with lowest impact on the coherence time. These measures can be taken to maximise NV density and coherence time at the same time. For any choice of laser medium with a given volume, density and coherence time a plot such as the examples in FIG. 8 can be produced in the same way. The optimal cavity loss rate and RF drive intensity can then be determined from the plot.
  • a change of only the laser medium volume with a fixed density of atoms or colour centres is equivalent to an increase of the number of atoms or colour centres.
  • a change of the cavity volume only by a factor f is equivalent to a reduction of atoms or colour centres by the same factor for the calculation of G (and therefore the calculation of n in FIG. 4).
  • the ideal parameters can be determined to optimize the sensitivity and/or measurement range.
  • the requirement of homogeneous application of the pump power can create restrictions and how these restrictions need to be considered.
  • any of the parameters can likely be restricted to a certain range of possible values due to technical availability and/or cost.
  • a certain type of laser medium might only be available with a certain range of colour centre densities or a certain range of volumes.
  • the laser pump power is restricted to a certain maximum power due to technical availability and/or heating and/or safety of the device. All such restrictions can easily be taken into account by optimizing the parameters only within the restricted possible range.
  • the frequency and wavelength of the laser pump are chosen such that it actually pumps the laser medium. For NV centres this is a wavelength with good absorption, for example laser light at 532nm.
  • the laser pump strength is ideally chosen to be at or close to the operating point, defined by the laser threshold. More specifically, for laser media where the laser pump together with the internal decay structure drives towards the brighter state (such as the NV centre in diamond), the operating point is the laser threshold at zero detuning (see FIG. 5). This operating point determines the laser pump strength, i.e. the laser pump strength cannot be chosen arbitrarily for the laser threshold sensor to work (and particularly to work ideally). For the sensitivity plots in FIG.s 8A to 8D the laser pump strength is always set to the respective operating point.
  • the maximal laser pump strength that is technically achievable needs to be considered in the following way since it can limit the process of finding the parameters for optimal sensitivity.
  • the laser pump should ideally be applied uniformly to the whole laser medium, although this can be compromised without destroying the operation of a laser threshold sensor.
  • the pump is applied uniformly when the power provided by the pump is much more than the power absorbed by the atoms or colour centres Ppump » Pabs. If the laser pump is another laser the pump power in Watt is given by: where A is the area illuminated by the pump, n is Planck's constant, ⁇ the angular frequency of the pump light, ⁇ the laser pump strength in Hertz and ⁇ the effective cross-section of the atom or colour centre.
  • N a t is the number of atoms or colour centres.
  • the pump power P pU mp refers to the power necessary if all atoms or colour centres are exposed to the same pump power.
  • the absorbed power Pabs refers to the power which is actually absorbed by the laser medium in that same case. For all colour centres to be exposed to approximately the same pump power the absorbed power should be much less than the pump power at the operating point for ⁇ . Otherwise the power of the pump is reduced by absorption as it passes through the laser medium and the pump power is not uniform throughout the laser medium any more.
  • Parameter choices which make P a bs similar to or even larger than P pU mp are not ideal for optical laser pumping because then the laser medium becomes significantly absorbing for the pumping light and excites the atoms or colour centres much stronger at the side of the laser medium, where the laser pump enters the laser medium, compared to the other side.
  • the output laser field in the cavity is still uniform (speaking in terms of the envelope of the nodes and antinodes) throughout the laser medium and will create stimulated emission even for weakly pumped atoms or colour centres. Therefore such a regime, although not ideal, might be chosen for certain reasons, such as a lower laser threshold or a wider range of magnetic fields or better sensitivity.
  • the density and geometry of the laser medium needs to fulfil: which can be achieved by using an appropriate density and/or volume or by adjusting the area, which is being pumped by using a suitable geometry of the laser medium within the limits of the cavity design.
  • An alternative measurement modality is to lower the laser pump to a fixed value below the upper laser threshold.
  • the upper laser threshold refers to the laser threshold when the RF drive is on resonance (for laser media where the laser pump together with the internal decay structure drives towards the brighter state).
  • This measurement modality achieves a better sensitivity, i.e. precision, at the expense of the measurement range of magnetic fields.
  • FIG. 1 1 shows the effects of this measurement modality with the example parameters used for curve 1040 in FIG. 10. Curve 1040 is plotted again and an additional curve 1 1 10 shows the effect when the laser pump is reduced. In this example it is reduced to 96% of the value of the curve 1040, which achieves much better (i.e. lower values of) sensitivity for a small range of magnetic fields, (a).
  • a laser threshold magnetometer can also measure oscillating (AC) magnetic fields. If the magnetometer is placed in an oscillating magnetic field, the laser output oscillates between values corresponding to the maximum and minimum of the oscillating magnetic field. Such oscillations can be measured well as long as the oscillation time is not shorter than the response time of the magnetometer. To be able to measure a large spectrum of frequencies the response time of the sensor should be minimised. The response time is essentially set by the inverse of the lowest of the following frequencies or rates: the laser pump rate, the effective internal non-spin-conserving decay rate of the laser medium, the RF drive strength (i.e. the Rabi frequency) or the cavity decay rate. The response time is minimised by choosing all of these frequencies and rates large.
  • the effective internal non-spin-conserving decay rate is the only one which is set by the laser medium and cannot be adjusted and therefore defines the shortest possible response time.
  • this rate is the decay via the singlet state (from state 5 via state 7 to state 1 in FIG.1 ) and sets the response time to approximately:
  • the laser output oscillates corresponding to the magnetic field.
  • an effective bias field can be set to offset the laser output to its point of maximal gradient with the magnetic field. This ensures that the laser output changes the strongest with the magnetic field oscillation.
  • An effective bias field can be set easily by detuning the RF drive from the corresponding transition frequency.
  • Very small amplitude oscillations can be measured with exceptional sensitivity by adjusting the laser threshold magnetometer to the small range of boosted sensitivity outlined above and in the example of curve 1 1 10 in FIG. 1 1 .
  • the sensitivity for an AC measurement can be calculated in accordance with Equation 14 , and reaches very similar values as the DC sensitivity.
  • a vector magnetometer measures the component in one direction of the magnetic field vector.
  • the laser threshold magnetometer can be realised as a vector magnetometer by using only one orientation of NV centres for the sensing. In a single crystal diamond there are four possible orientations for the NV centres. Using only one orientation for the sensing can be achieved by one or several of the following measures:
  • a single laser threshold magnetometer can also be realised as a magnetometer which measures magnetic field strength regardless of the orientation by directionally aligning the laser pump and the RF drive such that they address all four orientations equally. Such a laser threshold magnetometer senses magnetic fields in all directions.
  • Non-sensing centres do not create significant background fluorescence but instead can amplify the signal of the sensing centres because they also contribute to the signal via stimulated emission due to their interaction with the light field once the sensing centres have shifted the laser threshold and caused lasing.
  • the laser threshold sensor has been described largely in the context for the example of a laser threshold magnetometer, the same principles can be applied analogously to measure other quantities or physical parameters.
  • the only condition for that quantity is that it shifts the energy difference of the two states of the laser medium, which are referred to in the "first feature" of the laser medium above, i.e. the two states which have different brightness and are addressed by the RF drive.
  • the energy difference of the spin states are also dependent on the electric field due to the Stark shift. Although this dependence is less strong than the magnetic field dependence, the NV centre can also be used as an electrometer in the absence of a varying magnetic field. Laser threshold electrometry could therefore be performed, with NV centres in diamond as the laser medium, in complete analogy to laser threshold magnetometry.
  • a magnetic field sensitivity of 1fT/V(Hz) corresponds to an electric field sensitivity of approximately 10 "3 V/m / V(Hz).
  • the output from a laser threshold sensor is laser light which can be easily fibre-coupled, i.e. directed into and guided through an optical fibre, for example by either simply placing the end of an optic fibre outside the cavity or even by using fibre-cavities, where one end of the cavity is given by the end of an optic fibre with a suitable surface.
  • Fibre-coupling is advantageous as it enables the guiding of the output (for example towards the light detector) and therefore makes it possible to move the sensor around and allows for remote sensing. This makes the laser threshold sensor very versatile.
  • the ability for a fibre-coupled output is an advantage over existing magnetometry schemes, for example, which rely on the collection of spontaneously emitted light, which typically requires the usage of a large fixed optical system.
  • the laser threshold sensor can be designed such that parts of or the whole optical cavity is provided by the optic fibre itself.
  • the surface of the end of the optic fibre itself can be regarded as a partially transmitting mirror and therefore form one end of the optical cavity.
  • the reflection at the end of the optic fibre can be minimised and reflection can be arranged by a structure within the optic fibre, such as a fibre Bragg grating.
  • the laser medium for the laser threshold sensor could be integrated into the optic fibre and surrounded by reflecting structures, such that the fibre itself provides the whole optical cavity. For example a fibre Bragg grating on both sides could provide the optical cavity.
  • the laser pump is given by light then this laser pump light can be conveniently provided into the cavity through the optic fibre.
  • the cavity should be resonant with the pump laser light (as well as the emission from the laser medium) to enable the laser pump light to enter the cavity and to be amplified for cases where the laser medium is not strongly absorbing.
  • the cavity is made of mirrors with a wavelength dependence such as a fibre Bragg grating then two cavities (one inside the other) which are tuned to the pump wavelength and the emission wavelength respectively are a possible design.
  • the laser pump signal can fluctuate around its intended value. This can introduce technical noise because stronger or less strong driving can increase or decrease the laser output. Such fluctuations can be reduced for example by using amplitude stabilisers on the laser pump signal. If significant fluctuations remain on the laser pump signal the effect of such fluctuations can be counteracted or overcome by monitoring the pump laser signal and analysing the laser output signal of the magnetometer in relation to the pump laser signal, such that changes of the laser output signal due to changes in the magnetic field, for example, can be distinguished from changes of the laser output due to fluctuations in the laser pump signal. If the laser pump is another laser the signal can for example be monitored by splitting off a small fraction of the laser beam and directing it to a light detector, while the rest of the beam forms the laser pump signal for the laser threshold sensor.
  • the ground states 1 and 4 are the 4f(1 ) electron configuration
  • the excited states 2 and 5 are 5d(1 ) electron configuration.
  • States 1 , 2 and 3 are the spin manifold with states 4
  • States 3 and 6 are phonon-added ground states corresponding to 1 and 4 respectively.
  • the energy difference between the ground and excited state corresponds to a zero-phonon-line of about 489nm.
  • Internal decay rates are shown as solid downwards arrows.
  • Cerium in YAG is also a suitable laser medium for laser threshold magnetometry. Since the states 1 and 4 correspond to different spin states their energy difference depends on the external magnetic field and the first requirement is therefore fulfilled. From state 1 the laser pump efficiently excites the Cerium, leading to photon emission. From state 4 on the other hand the excitation by the laser pump is much weaker and therefore state 4 has less brightness under laser pumping than state 1 . The second requirement is therefore fulfilled. Finally the third requirement is also fulfilled because the laser pump together with the internal decay structure drives the Cerium towards state 4.
  • the laser pump drives Cerium in YAG towards the less bright state, which is in contrast to NV centres, where the laser pump drives towards the brighter state.
  • An operating point for the laser pump can therefore be chosen above this lower laser threshold. In that case an external magnetic field reduces the laser output.
  • the laser threshold sensor of the present invention demonstrates the potential to provide a number of advantages over the state of the art.
  • a laser threshold magnetometer formed and operated in accordance with the principles set forth herein, for example, enables measurement of an external magnetic field with high sensitivity but does not need to be operated at cryogenic temperatures unlike prior art devices.
  • the laser threshold magnetometer can be fibre-coupled, the laser output can be guided resulting in a capacity for the sensor to be moved around and allow for remote sensing. This makes the proposed laser threshold sensor very versatile.
  • this invention is described largely in the context of a laser threshold magnetometer, the principles enunciated herein are also applicable to measurement of other physical parameters, such as external electric fields, temperature and pressure.

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Abstract

L'invention concerne un capteur prévu pour mesurer une grandeur physique, le capteur comprenant : une cavité optique ; un milieu laser qui, conjointement avec la cavité optique, possède un seuil de laser ; une pompe laser ; et une commande radiofréquence (RF) appliquée au milieu laser, de telle sorte que le seuil de laser varie avec un changement de la grandeur physique ; la commande RF étant appliquée au milieu laser au niveau ou autour d'une fréquence de résonance particulière qui varie en fonction de la grandeur physique, de telle sorte qu'en fonction de la valeur de la grandeur physique, la commande RF induise des transitions entre au moins deux états du milieu laser, chaque état provoquant un seuil de laser différent dans une intensité d'une sortie laser ; et l'intensité de la sortie laser permettant une mesure de la valeur de la grandeur physique.
PCT/AU2016/050668 2015-07-28 2016-07-27 Capteur pour mesurer une grandeur physique WO2017015713A1 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019002576A1 (fr) * 2017-06-29 2019-01-03 Danmarks Tekniske Universitet Magnétomètre utilisant des défauts optiquement actifs dans un matériau à l'état solide
US20210218213A1 (en) * 2020-01-15 2021-07-15 Ceromaze Inc. Thin film maser emitter and thin panel phased array of emitters
CN114002515A (zh) * 2021-12-31 2022-02-01 南京高华科技股份有限公司 电场传感器及其制备方法
CN116227610A (zh) * 2023-05-08 2023-06-06 国仪量子(合肥)技术有限公司 离子阱系统及其电场补偿方法、离子阱量子计算机

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2685274A1 (fr) * 2011-03-08 2014-01-15 Sumitomo Heavy Industries, Ltd. Magnétomètre à pompage optique, appareil de mesure de magnétoencéphalographie et dispositif irm

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2685274A1 (fr) * 2011-03-08 2014-01-15 Sumitomo Heavy Industries, Ltd. Magnétomètre à pompage optique, appareil de mesure de magnétoencéphalographie et dispositif irm

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
JESKE, J. ET AL.: "Laser threshold magnetometer reaching attotesla precision", 23 October 2014 (2014-10-23), Cornell University Library, pages 1 - 11, XP020292199, Retrieved from the Internet <URL:https://arxiv.org/abs/1410.6239v1> [retrieved on 20161005] *
JESKE, J. ET AL.: "Laser threshold magnetometer reaching attotesla precision", 23 October 2014 (2014-10-23), RMIT University, pages 1 - 11, XP020292199, Retrieved from the Internet <URL:https://arxiv.org/pdf/1410.6239v1.pdf> [retrieved on 20161005] *
KAI-KAI, H. ET AL.: "A High Sensitivity Laser -Pumped Cesium Magnetometer", CHINESE PHYSICS LETTERS, vol. 29, no. 10, 2012, pages 100701-1 - 100701-3 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019002576A1 (fr) * 2017-06-29 2019-01-03 Danmarks Tekniske Universitet Magnétomètre utilisant des défauts optiquement actifs dans un matériau à l'état solide
US11340320B2 (en) 2017-06-29 2022-05-24 Danmarks Tekniske Universitet Magnetometer for measuring an unknown external magnetic field
US20210218213A1 (en) * 2020-01-15 2021-07-15 Ceromaze Inc. Thin film maser emitter and thin panel phased array of emitters
US11872386B2 (en) * 2020-01-15 2024-01-16 Emad Eskandar Thin film maser emitter and thin panel phased array of emitters
CN114002515A (zh) * 2021-12-31 2022-02-01 南京高华科技股份有限公司 电场传感器及其制备方法
CN114002515B (zh) * 2021-12-31 2022-04-05 南京高华科技股份有限公司 电场传感器及其制备方法
CN116227610A (zh) * 2023-05-08 2023-06-06 国仪量子(合肥)技术有限公司 离子阱系统及其电场补偿方法、离子阱量子计算机
CN116227610B (zh) * 2023-05-08 2023-07-25 国仪量子(合肥)技术有限公司 离子阱系统及其电场补偿方法、离子阱量子计算机

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