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WO2018174907A1 - Appareil et procédé de référencement en mode pulsé de matériau de centre de défaut magnéto-optique de résonance - Google Patents

Appareil et procédé de référencement en mode pulsé de matériau de centre de défaut magnéto-optique de résonance Download PDF

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Publication number
WO2018174907A1
WO2018174907A1 PCT/US2017/024169 US2017024169W WO2018174907A1 WO 2018174907 A1 WO2018174907 A1 WO 2018174907A1 US 2017024169 W US2017024169 W US 2017024169W WO 2018174907 A1 WO2018174907 A1 WO 2018174907A1
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Prior art keywords
optical
magneto
defect center
center material
excitation
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PCT/US2017/024169
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English (en)
Inventor
Gregory Scott Bruce
Arul Manickam
Peter G. Kaup
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Lockheed Martin Corporation
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Priority to PCT/US2017/024169 priority Critical patent/WO2018174907A1/fr
Publication of WO2018174907A1 publication Critical patent/WO2018174907A1/fr

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    • 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
    • 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
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
    • G01R33/1284—Spin resolved measurements; Influencing spins during measurements, e.g. in spintronics devices
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors

Definitions

  • the present disclosure relates to magnetic detection systems, and more generally, to measurement and signal processing methods for a magnetic detection system.
  • a number of industrial applications, as well as scientific areas such as physics and chemistry can benefit from magnetic detection and imaging with a device that has extraordinary sensitivity, ability to capture signals that fluctuate very rapidly (bandwidth) all with a substantive package that is extraordinarily small in size and efficient in power.
  • Many advanced magnetic imaging systems can require operation in restricted conditions, for example, high vacuum and/or cryogenic temperatures, which can make them inapplicable for applications that require ambient or other conditions.
  • a system for magnetic detection may include a magneto-optical defect center material comprising a plurality of defect centers, a radio frequency (RF) excitation source configured to provide RF excitation to the magneto-optical defect center material, an optical excitation source configured to provide optical excitation to the magneto- optical defect center material, an optical detector configured to receive an optical signal emitted by the magneto-optical defect center material, a bias magnet configured to separate RF resonance responses of the lattice oriented subsets of the magneto-optical defect center material, and a controller.
  • RF radio frequency
  • the controller may be configured to control the optical excitation source and the RF excitation source to apply a first pulse sequence to the magneto-optical defect center material, the first pulse sequence comprising a first optical excitation pulse, a first pair of RF excitation pulses separated by a first time period, and a second optical excitation pulse to the magneto- optical defect center material.
  • the controller may be configured to control the optical excitation source and the RF excitation source to further apply a second pulse sequence to the magneto- optical defect center material, the second pulse sequence comprising a third optical excitation pulse, a second pair of RF excitation pulses separated by a second time period, and a fourth optical excitation pulse to the magneto-optical defect center material.
  • a pulse width of the first pair of RF excitation pulses may be different than a pulse width of the second pair of RF excitation pulses, and the first time period may be different than the second time period.
  • the controller may be further configured to receive a first light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the first pulse sequence and may be configured to receive a second light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the second pulse sequence.
  • the controller may be further configured to compute a combined measurement based on a difference between a measured value of the first light detection signal and a measured value of the second light detection signal wherein the slope of the combined measurement is greater that the slope of the first light detection signal and the second light detection signal.
  • the controller may be further configured to compute a combined measurement based on a difference between a measured value of the first light detection signal and a measured value of the second light detection signal wherein the slope of the combined measurement is greater than the slope of the measured value of the first and second light detection signals.
  • a method for magnetic detection using a magneto- optical defect center material comprising a plurality of defect centers may comprise applying a first pulse sequence to the magneto-optical defect center material, applying a second pulse sequence to the magneto-optical defect center material, receiving a first light detection signal using an optical detector, receiving a second light detection signal using the optical detector, and computing a combined measurement based on a difference between a measured value of the first light detection signal and a measured value of the second light detection signal.
  • the first pulse sequence may comprise a first optical excitation pulse using an optical excitation source, a first pair of RF excitation pulses separated by a first time period using a radio frequency (RF) excitation source, and a second optical excitation pulse to the magneto-optical defect center material using the optical excitation source.
  • the second pulse sequence may comprise a third optical excitation pulse using the optical excitation source, a second pair of RF excitation pulses separated by a second time period using the RF excitation source, and a fourth optical excitation pulse to the magneto-optical defect center material using the optical excitation source.
  • a pulse width of the first pair of RF excitation pulses is different than a pulse width of the second pair of RF excitation pulses.
  • the first time period is different than the second time period.
  • Receiving the first light detection signal may be based on an optical signal emitted by the magneto-optical defect center material due to the first pulse sequence.
  • the second light detection signal may be based on an optical signal emitted by the magneto-optical defect center material due to the second pulse sequence.
  • an RF excitation frequency used for the first pair of RF excitation pulses and the second pair of RF excitation pulses in a system for magnetic detection may be associated with an axis of a defect center of the magneto-optical defect center material.
  • the controller may be further configured to compute a change in an external magnetic field acting on the magneto-optical defect center material based on the combined measurement.
  • a method for magnetic detection using a magneto-optical defect center material has the RF excitation frequency used for the first pair of RF excitation pulses and the second pair of RF excitation pulses is associated with an axis of a defect center of the magneto-optical defect center material.
  • a method for magnetic detection using a magneto-optical defect center material further comprises computing a change in an external magnetic field acting on the magneto-optical defect center material based on the combined measurement.
  • the second pair of RF excitation pulses of the first pulse sequence may be applied at a frequency detuned from a resonance frequency of the magneto-optical defect center material.
  • the pulse width of the second pair of RF excitation pulses may be associated with a null at center frequency representing a lack of dimming in the fluorescence of the magneto-optical defect center material.
  • the second time period may be associated with a null at a center frequency representing a lack of dimming in the fluorescence of the magneto-optical defect center material.
  • the pulse width of the second pair of RF excitation pulses and the second time period may be associated with a null at a center frequency
  • the RF excitation source may be a microwave antenna.
  • the controller may be configured to apply the first pair of RF excitation pulses followed by the second pair of RF excitation pulses.
  • the pulse width of the first pair of RF excitation pulses and the first time period is associated with a high point at a center frequency representing dimming in the fluorescence of the magneto-optical defect center material.
  • a method for magnetic detection using a magneto- optical defect center material may have the first pair of RF excitation pulses applied followed by the second pair of RF excitation pulses.
  • the bias magnet is one of a permanent magnet, a magnet field generator, or a Halbach set of permanent magnets.
  • computing the change in an external magnetic field acting on the magneto-optical defect center material based on the combined measurement comprise a plurality of pairs of RF excitation pulses.
  • a SMAC measurement may be performed at a chosen frequency (e.g. at a frequency with a maximum slope for the curve) and the intensity of the SMAC measurement is monitored to provide an estimate of the magnetic field.
  • the maximum slope, positive and negative may be determined from the curve obtained by the SMAC pairing and the corresponding frequencies.
  • the curve may be first smoothed and fit to a cubic spline.
  • only the corresponding frequencies may be stored for use in magnetic field measurements. In some implementations, the entire curve may be stored.
  • a magnetic detection system may comprise a defect center material responsive to an applied magnetic field, a radio frequency (RF) emitter operational to provide a first RF pulse sequence separated by at least one pause, a detector operational to measure the fluorescence of the defect center material in conjunction with the first RF pulse sequence and the second RF pulse sequence, thereby providing a first measurement curve and a second measurement curve affected by the applied magnetic field, respectfully, and a control circuit connected to the detector and operational to determine a difference between the first measurement curve and the second measurement curve to obtain greater sensitivity to variations in the applied magnetic field.
  • the RF emitter may be operational to provide a second RF pulse sequence that is different from the first RF pulse sequence.
  • the RF emitter may be operational to provide a second RF pulse sequence that is different from the first RF pulse sequence.
  • the first RF pulse sequence and the second RF pulse sequence are applied at a frequencies detuned from a resonance frequency of the defect center material.
  • the first RF pulse sequence is applied followed by the second RF pulse sequence.
  • the defect center material may be a nitrogen vacancy diamond.
  • the defect center material may be Silicon Carbide (SiC).
  • a method for magnetic detection or a method for detecting a magnetic field comprises emitting a first RF pulse sequence separated by at least one pause, using an RF emitter to a defect center material, emitting a second RF pulse sequence that is different from the first RF pulse sequence, using the RF emitter, to the defect center material, measure the fluorescence of the defect center material in conjunction with the first RF pulse sequence and the second RF pulse sequence, using a detector, providing a first RF pulse sequence separated by at least one pause, using an RF emitter to a defect center material, emitting a second RF pulse sequence that is different from the first RF pulse sequence, using the RF emitter, to the defect center material, measure the fluorescence of the defect center material in conjunction with the first RF pulse sequence and the second RF pulse sequence, using a detector, providing a first RF pulse sequence separated by at least one pause, using an RF emitter to a defect center material, emitting a second RF pulse sequence that is different from the first RF pulse
  • determining the difference between the first measurement curve and the second measurement curve may be performed by a control circuit.
  • the first RF pulse sequence and the second RF pulse sequence may be applied at a frequency detuned from a resonance frequency of the defect center material.
  • the first RF pulse sequence may be emitted followed by the second RF pulse sequence.
  • the defect center material may be a nitrogen vacancy diamond.
  • the defect center material is Silicon Carbide (SiC).
  • a system for magnetic detection may comprise, a magneto-optical defect center material comprising a plurality of defect centers, a means of providing RF excitation to the magneto-optical defect center material, a means of providing optical excitation to the magneto-optical defect center material, a means of receiving an optical signal emitted by the magneto-optical defect center material, and a means of controlling the provided RF excitation and provided optical excitation.
  • the means of controlling the provided RF excitation and provided optical excitation may apply a first pulse sequence to the magneto- optical defect center material, the first pulse sequence comprising a first optical excitation pulse, a first pair of RF excitation pulses separated by a first time period, and a second optical excitation pulse to the magneto-optical defect center material, control the optical excitation source and the RF excitation source to apply a second pulse sequence to the magneto-optical defect center material, the second pulse sequence comprising a third optical excitation pulse, a second pair of RF excitation pulses separated by a second time period, and a fourth optical excitation pulse to the magneto-optical defect center material, receive a first light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the first pulse sequence, receive a second light detection signal from the optical detector based on an optical signal emitted by the magneto-optical defect center material due to the second pulse sequence, and compute a combined measurement based on a difference between
  • FIG. 1 illustrates a defect center in a diamond lattice in accordance with some illustrative embodiments.
  • FIG. 2 illustrates an energy level diagram showing energy levels of spin states for a defect center in accordance with some illustrative embodiments.
  • FIG. 3 is a schematic diagram illustrating a defect center magnetic sensor system in accordance with some illustrative embodiments.
  • FIG. 4 is a graph illustrating the fluorescence as a function of an applied RF frequency of a defect center along a given direction for a zero magnetic field.
  • FIG. 5 is a graph illustrating the fluorescence as a function of an applied RF frequency for four different defect center orientations for a non-zero magnetic field.
  • FIG. 6 is a schematic illustrating a Ramsey sequence of optical excitation pulses and RF excitation pulses according to an operation of the system in some embodiments.
  • FIG. 7A is a free induction decay curve where a free precession time ⁇ is varied using a Ramsey sequence in some embodiments.
  • FIG. 7B is a magnetometry curve where a RF detuning frequency ⁇ is varied using a Ramsey sequence in some embodiments.
  • FIG. 8 is a graphical diagram depicting a reference signal intensity relative to detune frequency and a measured signal intensity relative to detune frequency in accordance with some embodiments.
  • FIG. 9 is a plot showing a traditional magnetometry curve using a Ramsey sequence in accordance with some embodiments.
  • FIG. 10 is a plot showing an invented magnetometry curve using a Ramsey sequence in accordance with some embodiments.
  • FIG. 11 is a plot showing a combined magnetometry curve of a traditional and inverted curve in accordance with some embodiments.
  • FIG. 12 is a schematic diagram illustrating a system for magnetic field detection according to some embodiments. DETAILED DESCRIPTION
  • Magneto-optical defect center materials such as diamonds with nitrogen vacancy (NV) centers can be used to detect magnetic fields.
  • Atomic-sized nitrogen-vacancy (NV) centers in diamond lattices can have excellent sensitivity for magnetic field measurement and can enable fabrication of small magnetic sensors.
  • the sensing capabilities of diamond NV (DNV) sensors may be maintained at room temperature and atmospheric pressure and these sensors can be even used in liquid environments.
  • Excitation light such as green light
  • fluorescent light which is red
  • the intensity of red light emitted can be used to determine the strength and direction of the magnetic field.
  • the efficiency and accuracy of sensors using magneto-optical defect center materials such as diamonds with NV centers (generally, DNV sensors) is increased by transferring as much light as possible from the defect centers to the photo sensor that measures the amount of red light.
  • Magneto-optical defect center materials include but are not be limited to diamonds, Silicon Carbide (SiC) and other materials with nitrogen, boron, or other chemical defect centers.
  • the system utilizes a special Ramsey pulse sequence pair or a 'shifted magnetometry adapted cancellation' (SMAC) pair to detect and measure the magnetic field acting on the system.
  • These parameters include the resonant Rabi frequency, the free precession time (tau), the RF pulse width, and the detuning frequency, all of which help improve the sensitivity of the measurement.
  • tau free precession time
  • tau detuning frequency
  • a single pulse sequence is repeated in which there may be repolarization of the system, double RF pulses separated by a gap for the free precession time, a start of the optical excitation and a readout during the optical excitation.
  • a SMAC excitation there is a second set of RF pulses having a pulse width and tau values which may be different from the pulse width and tau of the first set.
  • the first set of RF pulses is done with the first set of values, there is repolarization of the system, and then the second set of values is used to create an inverted curve.
  • the SMAC pair estimate is a combination of the magnetometry curves of the two pulse sequences with different values. In some embodiments, the combination is the difference between the two curves. This creates a magnetometry curve with an improved slope and therefore improved performance.
  • low-frequency noise such as vibrations, laser drift, low-frequency noise in the receiver circuits, and residual signals from previous
  • this noise reduction may provide a sensitivity increase at lower frequencies where colored noise may be the strongest.
  • the low-frequency noise cancelation may be due to slowly varying noise in the time domain appearing almost identically in the two sequential sets of Ramsey measurements in the SMAC pair measurement.
  • inverting the second Ramsey set and subtracting the measurement from the first Ramsey set may largely cancel out any noise that is added post-inversion. Inverting the second Ramsey set and then subtracting its measurement off from the first may therefore largely cancel out any noise that is added post-inversion.
  • the low frequency noise cancelation may be understood by viewing the SMAC technique as a digital modulation technique, whereby, in the frequency domain, the magnetic signals of interest are modulated up to a carrier frequency of half the sampling rate (inverting every second set of Ramsey measurements is equivalent to multiplying the signal by e 17771 where n is the sample (i.e., Ramsey pulse number). In some embodiments, this may shift the magnetic signals of interest to a higher frequency band that is separated from the low-frequency colored noise region. Then, a high-pass filter may be applied to the signal to remove the noise, and finally, the signal may be shifted back to baseband.
  • performing a differential measurement may be equivalent to a two-tap high-pass filter, followed by a 2x down- sampling.
  • higher-order filters may be used to provide more out-of-band noise rejection to leave more bandwidth for the signal of interest.
  • the sidelobe responses from nearby lattice vectors will be present.
  • the signals from these sidelobes may cause inter-lattice vector interference, resulting in corruption of the desired measurement.
  • the SMAC technique may see lower sidelobe levels (and thus less inter-lattice vector interference) than those from regular Ramsey measurements.
  • different lattice vectors have potentially different optimal pulse width & tau values, based on the RF polarization, laser polarization, and gradient of the bias magnetic field.
  • applying the optimal pulse width and tau settings for one lattice vector may cause the nearby lattice vectors' responses to be lower than if they were interrogated at their respective optimal values. In some embodiments, for the SMAC technique, this reduction of the nearby lattice vector's responses can become even more pronounced. Not only are there different optimal pulsewidth and tau settings for the first Ramsey set, but there may be also potentially different optimal pulse width and tau settings for the second, inverted Ramsey set. This second Ramsey set discrepancy provides potential for even more reduction in neighboring lattice vectors' responses when using the optimal settings for the lattice vector of interest.
  • the defect center in a diamond comprises a substitutional nitrogen atom in a lattice site adjacent a carbon vacancy as shown in FIG. 1.
  • the NV center may have four orientations, each corresponding to a different crystallographic orientation of the diamond lattice.
  • the NV center may exist in a neutral charge state or a negative charge state.
  • the neutral charge state uses the nomenclature NV°, while the negative charge state uses the nomenclature NV, which is adopted in this description.
  • the NV center has a number of electrons, including three unpaired electrons, each one from the vacancy to a respective of the three carbon atoms adjacent to the vacancy, and a pair of electrons between the nitrogen and the vacancy.
  • the NV center which is in the negatively charged state, also includes an extra electron.
  • the optical transitions between the ground state 3 A 2 and the excited triplet 3 E are predominantly spin conserving, meaning that the optical transitions are between initial and final states that have the same spin.
  • a photon of red light is emitted with a photon energy corresponding to the energy difference between the energy levels of the transitions.
  • the system 300 includes an optical excitation source 310, which directs optical excitation to a magneto-optical defect center material 320 with defect centers (e.g, NV diamond material).
  • the system further includes an RF excitation source 330, which provides RF radiation to the magneto-optical defect center material 320. Light from the NV diamond may be directed through an optical filter 350 to an optical detector 340.
  • the RF excitation source 330 may be a microwave coil.
  • the optical excitation source 310 may be a laser or a light emitting diode which emits light in the green. In some implementations, the optical excitation source 310 induces fluorescence in the red, which corresponds to an electronic transition from the excited state to the ground state.
  • light from the magneto-optical defect center material 320 is directed through the optical filter 350 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the detector 340.
  • the component Bz may be determined.
  • Optical excitation schemes other than continuous wave excitation are contemplated, such as excitation schemes involving pulsed optical excitation, and pulsed RF excitation. Examples of pulsed excitation schemes include Ramsey pulse sequence (described in more detail below), and spin echo pulse sequence.
  • Optical excitation schemes other than continuous wave excitation are
  • excitation schemes involving pulsed optical excitation, and pulsed RF excitation.
  • pulsed excitation schemes include Ramsey pulse sequence, and spin echo pulse sequence.
  • the excitation scheme utilized during the measurement collection process i.e., the applied optical excitation and the applied RF excitation
  • the excitation scheme utilized during the measurement collection process may be any appropriate excitation scheme.
  • the excitation scheme may utilize continuous wave (CW) magnetometry, pulsed magnetometry, and variations on CW and pulsed magnetometry (e.g., pulsed RF excitation with CW optical excitation).
  • pulse parameters ⁇ and ⁇ may be determined as described in, for example, U.S. Patent Application No. 15/003,590, which is incorporated by reference herein in its entirety.
  • the magneto-optical defect center material 320 has defect centers aligned along directions of four different orientation classes.
  • FIG. 5 illustrates fluorescence as a function of RF frequency for the case where the magneto-optical defect center material 320 has defect centers aligned along directions of four different orientation classes.
  • the component Bz along each of the different orientations may be determined.
  • the magnetic sensor system may employ a variety of different magneto- optical defect center material, with a variety of magneto-optical defect centers.
  • Magneto-optical defect center materials include but are not be limited to diamonds, Silicon Carbide (SiC) and other materials with nitrogen, boron, or other defect centers.
  • the electronic spin state energies of the magneto-optical defect centers shift with magnetic field, and the optical response, such as fluorescence, for the different spin states is not the same for all of the different spin states.
  • the magnetic field may be determined based on optical excitation, and possibly RF excitation, in a corresponding way to that described above with NV diamond material.
  • Ramsey pulse sequence is a pulsed RF laser scheme that is believed to measure the free precession of the magnetic moment in the magneto-optical defect material 320 with defect centers, and is a technique that quantum mechanically prepares and samples the electron spin state.
  • a first RF excitation pulse in the form of, for example, a pulse width / 2 (pwi/2) microwave (MW)
  • the spins are allowed to freely precess (and dephase) over a time period referred to as tau ( ⁇ ).
  • tau tau
  • a second optical pulse is applied to optically sample the system and a measurement basis is obtained by detecting the fluorescence intensity.
  • a third RF excitation pulse in the form of, for example, a second MW pulse width / 2 (pw 2 /2) ).
  • the spins are allowed to freely precess (and dephase) over a time period referred to as tau 2 ( ⁇ 2 ).
  • tau 2 ⁇ 2
  • the system measures the local magnetic field and serves as a coherent integration.
  • a fourth optical pulse is applied to optically sample the system and a measurement basis is obtained by detecting the fluorescence intensity of the system.
  • FIG. 6 depicts the pulse sequences continuing with another sequence with pwi.
  • a reference signal may be determined by using a reference signal acquisition prior to the RF pulse excitation sequence and measured signal acquisition. A contrast measurement between the measured signal and the reference signal for a given pulsed sequence is then computed as a difference between a processed read-out fluorescence level from the measured signal acquisition and a processed reference fluorescence measurement from the reference signal. The processing of the measured signal and/or the reference signal may involve computation of the mean fluorescence over each of the given intervals.
  • the reference signal acts to compensate for potential fluctuations in the optical excitation power level (and other aspects), which can cause a proportional fluctuation in the measurement and readout fluorescence measurements.
  • the magnetometer includes a full repolarization between measurements with a reference fluorescence intensity (e.g., the reference signal) captured prior to RF excitation (e.g., RF pulse excitation sequence) and the subsequent magnetic b field measurement data.
  • a reference fluorescence intensity e.g., the reference signal
  • RF excitation e.g., RF pulse excitation sequence
  • the bandwidth considerations provide a high laser power density trade space in sensor design, which can impact available integration time and achievable sensitivity.
  • the magnetometer system may omit a reference signal acquisition prior to RF pulse excitation sequence and measured signal acquisition.
  • the system processes the post RF sequence read-out measurement from the measured signal directly to obtain magnetometry measurements.
  • the processing of the measured signal may involve computation of the mean fluorescence over each of the given intervals.
  • a fixed "system rail" photo measurement is obtained and used as a nominal reference to compensate for any overall system shifts in intensity offset.
  • an optional ground reference signal may be obtained during the RF pulse excitation sequence to be used as an offset reference.
  • an approximation of the readout from a Ramsey pulse sequence when the pulse width is much less than the free precession interval may be defined as equation (1) below:
  • ⁇ represents the free precession time
  • ⁇ 2 * represents spin dephasing due to inhomogeneities present in the system 600
  • ⁇ ⁇ 3 represents the resonant Rabi frequency
  • ⁇ ⁇ ⁇ represents the effective Rabi frequency
  • a n represents the hyperfine splitting of the NV diamond material 620 ( ⁇ 2.14 MHz)
  • ⁇ represents the MW detuning
  • ⁇ represents the phase offset.
  • the parameters that may be controlled are the duration of the MW ⁇ /2 pulses, the frequency of the MW pulse (which is referenced as the frequency amount detuned from the resonance location, ⁇ ), and the free precession time ⁇ .
  • FIGS. 7 A and 7B show the effects on the variance of certain parameters of the Ramsey pulse sequence. For example, as shown in FIG. 7A, if all parameters are kept constant except for the free precession time ⁇ , an interference pattern, known as the free induction decay (FID), is obtained.
  • the FID curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting.
  • the decay of the signal is due to
  • Figure 8 is a graphical diagram of an intensity of a measured signal 810 from an optical detector 340 relative to an intensity of a reference signal 820 from the optical detector 340 over a range of detune frequencies.
  • the reference signal 820 will contain signal information from a prior RF pulse for a finite period of time. This prior signal information in the reference signal 820 reduces available detune Vpp and slope for a detune point for positive slope 830 and a detune point for negative slope 840.
  • the system would need to wait until the prior signal information is eliminated from the reference signal or operate without the reference signal.
  • FIG. 9 depicts a plot of a magnetometry curve using a Ramsey sequence in accordance with some embodiments. The plot depicts intensity decreasing as you go up the y- axis, so curves seen in the plot going up represent a dimming in intensity. In some embodiments, the intensity is the measured fluorescence intensity obtained from a magneto-optical defect material with defect centers.
  • the x-axis represents an RF excitation frequency of a microwave source used in the Ramsey sequence.
  • the magnetometry curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting in addition to side lobes caused by the Ramsey pulse.
  • this curve is a representative depiction of the first pulse sequence as depicted in FIG. 6.
  • the curve shows an upward curve at the center frequency, representing dimming.
  • FIG. 10 depicts a plot of an inverted magnetometry curve using a Ramsey sequence in accordance with some embodiments.
  • the plot depicts intensity decreasing as you go up the y- axis so curves seen in the plot going up represent a dimming in intensity.
  • the intensity is the measured fluorescence intensity obtained from a magneto-optical defect material with defect centers.
  • the x-axis represents an RF excitation frequency of a microwave source used in the Ramsey sequence.
  • the magnetometry curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting in addition to side lobes caused by the Ramsey pulse.
  • this curve is a representative depiction of the second pulse sequence as depicted in FIG. 6.
  • the values of pulse width and ⁇ 2 of the second pulse sequence are chosen such that a null is seen at the center frequency, representing a lack of dimming.
  • the null can be thought of in terms of a representation on a Bloch sphere where the zero reference of the spin state and the minus one spin state of the defect center electrons on a sphere are the North Pole and South Pole.
  • the first RF pulse may move the state from the baseline zero spin state to the equator of the Bloch sphere.
  • the precession time after the first RF pulse may move the state around the equator of the Bloch sphere representation with time.
  • the second RF pulse may create maximum dimming in the fluorescence.
  • the precession time i.e., ⁇ 2
  • the precession time allows for the state to simply go around the South Pole which is not doing anything, and the second RF pulse to create minimum dimming or take advantage of a null point in the dimming of the fluorescence.
  • the curve shows a downward curve at the center frequency, representing a lack of dimming.
  • the inverted curve is created because the pulse width and ⁇ 2 value are chosen such that the time given to the precession is enough to take advantage of a null point at the chosen frequency.
  • FIG. 11 depicts a plot showing a combined magnetometry curve of a traditional and inverted curve in accordance with some embodiments, where the curves from FIG. 9 and FIG. 10 are combined.
  • the curves are combined by combining the intensities at each frequency value, such as for example, by taking the difference between intensities at each frequency value.
  • the intensity is the measured fluorescence intensity obtained from a magneto-optical defect material with defect centers.
  • the x-axis represents an RF excitation frequency of a microwave source used in the Ramsey sequence.
  • the plot combines the curves as depicted in FIG. 10 and FIG. 11.
  • the combined plot is obtained by taking the difference between the traditional curve and the inverted curve.
  • the plot depicts intensity decreasing as you go up the y-axis so curves seen in the plot going up represent a dimming in intensity.
  • the magnetometry curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting in addition to side lobes caused by the Ramsey pulse.
  • a SMAC measurement is performed at a chosen frequency (e.g. at a frequency with a maximum slope for the curve) and the intensity of the SMAC measurement is monitored to provide an estimate of the magnetic field.
  • the maximum slope positive and negative, is determined from the curve obtained by the SMAC pairing and the corresponding frequencies.
  • the curve is first smoothed and fit to a cubic line.
  • only the corresponding frequencies are stored for use in magnetic field measurements.
  • the entire curve is stored.
  • Various implementations may use different numbers of measurement points to plot out the curve.
  • a width of curve comprising 12.5 MHZ
  • 500 different frequencies separated by 25 KHz may be measured.
  • Other widths of the curve with differing granularity of the separation of measurement points are possible.
  • a plurality of measurements are done at each measurement point.
  • FIG. 12 is a schematic diagram of a system 1200 for a magnetic field detection system according to some embodiments.
  • the system 1200 includes an optical excitation source 1210, which directs optical excitation through a waveplate assembly 1225 to a diamond with nitrogen vacancy (NV) centers or another magneto-optical defect center material with magneto- optical defect centers 1220.
  • An RF excitation source 1230 provides RF radiation to the magneto- optical defect center material 1220.
  • a magnetic field generator 1270 generates a magnetic field, which is detected at the magneto-optical defect center material 1220.
  • the magnetic field generator 1270 may be used to apply a bias magnetic field that sufficiently separates the intensity responses corresponding to electron spin resonances for each of the lattice vectors.
  • the controller 1280 may then control the optical excitation source 1210 to provide optical excitation to the magneto-optical defect center material 1220 and the RF excitation source 1230 to provide RF excitation to the magneto-optical defect center material with magneto-optical defect centers 1220.
  • the resulting fluorescence intensity responses for each of the lattice vectors may be collected over time to determine the components of the external magnetic field Bz aligned along directions of the lattice vectors corresponding to magneto-optical defect center material crystallographic axes which may then be used to calculate the estimated vector magnetic field acting on the system 1200.
  • the magnetic field generator 1270 may be a permanent magnet positioned relative to the magneto-optical defect center material 1220, which generates a known, uniform magnetic field (e.g., a bias or control magnetic field) to produce a desired fluorescence intensity response from the magneto-optical defect center material 1220.
  • a known, uniform magnetic field e.g., a bias or control magnetic field
  • the magnetic field generator 1270 may generate magnetic fields with orthogonal polarizations.
  • the magnetic field generator 1270 may include two or more magnetic field generators, such as two or more Helmholtz coils.
  • the two or more magnetic field generators may be configured to provide a magnetic field having a predetermined direction, each of which provide a relatively uniform magnetic field at the magneto-optical defect center material 1220.
  • the predetermined directions may be orthogonal to one another.
  • the two or more magnetic field generators of the magnetic field generator 1270 may be disposed at the same position, or may be separated from each other. In the case that the two or more magnetic field generators are separated from each other, the two or more magnetic field generators may be arranged in an array, such as a one-dimensional or two-dimensional array, for example.
  • the system 1200 includes, in some implementations, a waveplate assembly 1225.
  • the waveplate assembly 1225 is configured to adjust the polarization of the light (e.g., light from a laser) as it the light is passed through the waveplate assembly 1225.
  • the waveplate assembly 1225 is configured to mount a waveplate to allow for rotation of the waveplate with the ability to stop the plate into a position at a specific rotation.
  • the waveplate assembly 1225 is configured to allow for rotation of the waveplate with the ability to lock the plate in to a position at a specific rotation. Stopping the waveplate at a specific rotation allows the configuration of the waveplate assembly 1225 to tune the polarization of the light passing through the waveplate.
  • the waveplate assembly 1225 is configured to adjust the polarization of the light such that the orientation of a given lattice of a magneto-optical defect center material allows the contrast of a dimming Lorentzian to be deepest and narrowest such that the slope of each side of the Lorentzian is steepest.
  • the waveplate assembly 1225 is configured such that the polarization of the light is lined up with the orientation of a given lattice of a magneto-optical defect center material such that it allows extraction of maximum sensitivity of the lattice (i.e., maximum sensitivity of a vector in free space).
  • the waveplate assembly 1225 is configured such that four determined positions of the waveplate maximize the sensitivity across all the different lattices of a magneto-optical defect center material. In some implementations, the waveplate assembly 1225 is configured where the position of the waveplate is such that similar sensitivities are achieved to the four Lorentzians corresponding to lattices of a magneto-optical defect center material. Different waveplates may be used in different implementations, including but not limited to half-wave plates and quarter- wave plates.
  • the system 1200 may be arranged to include one or more optical detection systems, comprising an optical detector 1240, optical excitation source 1210, and magneto-optical defect center material 1220.
  • the magnetic field generator 1270 may have a relatively high power as compared to the optical detection systems. In this way, the optical detection systems may be deployed in an environment that requires a relatively lower power for the optical detection systems, while the magnetic field generator 1270 may be deployed in an environment that has a relatively high power available for the magnetic field generator 1270 so as to apply a relatively strong magnetic field.
  • the system 1200 further includes a controller 1280 arranged to receive a light detection signal from the optical detector 1240 and to control the optical excitation source 1210, the RF excitation source 1230, and a second magnetic field generator (not shown).
  • the controller may be a single controller, or multiple controllers. For a controller including multiple controllers, each of the controllers may perform different functions, such as controlling different components of the system 1200.
  • the second magnetic field generator may be controlled by the controller 1280 via an amplifier.
  • the RF excitation source 1230 is a microwave coil, for example.
  • the optical excitation source 1210 may be a laser or a light emitting diode, for example, which emits light in the green, for example.
  • the optical excitation source 1210 induces fluorescence in the red from the Magneto-optical defect center material 1220, where the fluorescence corresponds to an electronic transition from the excited state to the ground state.
  • Light from the Magneto-optical defect center material 1220 is directed through the optical filter 1250 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 1240.
  • the controller 1280 is arranged to receive a light detection signal from the optical detector 1240 and to control the optical excitation source 1210, the waveplate assembly 1225, and the RF excitation source 1230, and the second magnetic field generator.
  • the controller may include a processor 1282 and a memory 1284, in order to control the operation of the optical excitation source 1210, the waveplate assembly 1225, the RF excitation source 1230, and the second magnetic field generator.
  • the memory 1284 which may include a non-transitory computer readable medium, may store instructions to allow the operation of the optical excitation source 1210, the RF excitation source 1230, and the second magnetic field generator to be controlled. That is, the controller 1280 may be programmed to provide control. In some implementations, the controller 1280 is configured to control an angle of the rotation of a half-wave plate.
  • any of the operations described herein can be implemented at least in part as computer-readable instructions stored on a computer-readable memory. Upon execution of the computer-readable instructions by a processor, the computer- readable instructions can cause a node to perform the operations.
  • any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality.
  • operably couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

La présente divulgation concerne des appareils et des procédés pour stimuler un matériau à défauts magnéto-optiques ayant des centres de défauts dans un système de détection magnétique à l'aide d'un processus de stimulation de façon à accroître significativement la sensibilité magnétique du système de détection. Le système utilise une paire de séquences d'impulsions Ramsey modifiées ou une paire d'annulations adaptées par magnétométrie décalée (SMAC) pour détecter et mesurer le champ magnétique agissant sur le système, ce qui entraîne une atténuation des sources de bruit basse fréquence et induit une sensibilité de capteur améliorée. Pour une mesure par paire SMAC, deux valeurs différentes de tau sont utilisées ainsi que deux valeurs différentes de largeur d'impulsion hyperfréquence.
PCT/US2017/024169 2017-03-24 2017-03-24 Appareil et procédé de référencement en mode pulsé de matériau de centre de défaut magnéto-optique de résonance WO2018174907A1 (fr)

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CN112327226A (zh) * 2020-11-05 2021-02-05 北京卫星环境工程研究所 基于金刚石nv色心磁场测量中的微波噪声消除方法
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CN118349824A (zh) * 2024-03-29 2024-07-16 昆明理工大学 一种星载全波形激光雷达回波的最优脉宽高斯分解方法

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US10969445B2 (en) * 2018-07-03 2021-04-06 Sumida Corporation Magnetic field measurement apparatus and magnetic field measurement method
US11619687B2 (en) 2018-07-03 2023-04-04 Sumida Corporation Magnetic field measurement apparatus and magnetic field measurement method
GB2578799A (en) * 2018-09-18 2020-05-27 Lockheed Corp Apparatus and method for lower magnetometer drift with increased accuracy
CN110440910A (zh) * 2019-08-22 2019-11-12 西门子工厂自动化工程有限公司 振动监测方法、装置、驱动系统、工控设备及存储介质
KR20210075402A (ko) * 2019-12-13 2021-06-23 한국표준과학연구원 다이아몬드 질소 공석 자기장 센서
KR102274933B1 (ko) * 2019-12-13 2021-07-08 한국표준과학연구원 다이아몬드 질소 공석 자기장 센서
CN112327226A (zh) * 2020-11-05 2021-02-05 北京卫星环境工程研究所 基于金刚石nv色心磁场测量中的微波噪声消除方法
CN112327226B (zh) * 2020-11-05 2024-03-19 北京卫星环境工程研究所 基于金刚石nv色心磁场测量中的微波噪声消除方法
CN118349824A (zh) * 2024-03-29 2024-07-16 昆明理工大学 一种星载全波形激光雷达回波的最优脉宽高斯分解方法

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