An all-optical dual-axis atomic magnetometer device and method based on optical frequency shift modulation

Abstract

The application relates to a full-optical double-axis atomic magnetometer device and method based on optical frequency shift modulation. A conventional SERF atomic magnetometer can only realize single-axis magnetic field measurement, and a high-frequency modulation magnetic field can be introduced through a magnetic field coil to realize multi-axis magnetic field measurement. However, the method can increase spin exchange relaxation and reduce the sensitivity of magnetic field measurement. Meanwhile, in the application of an arrayed SERF atomic magnetometer, the method can also cause crosstalk. The full-optical double-axis atomic magnetometer device and method based on optical frequency shift modulation disclosed by the application adopts a beam of pumping light which is modulated into a modulation light through an acousto-optic modulator. On the basis of realizing the original pumping function, the light beam simultaneously generates an optical frequency shift modulation magnetic field to replace the existing modulation magnetic field introduced through a magnetic field coil, realizes full-optical configuration, can complete double-axis magnetic field measurement, and can be better applied to extremely weak magnetic field measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atomic magnetometer, and particularly relates to a full-optical double-axis atomic magnetometer device and method based on optical frequency shift modulation. BACKGROUND

[0002] An atomic magnetometer realizes precise measurement of a magnetic field through optical pumping of atomic spin polarization, and has a wide application in basic physical research, magnetic anomaly detection, biological treatment and the like. Among them, an atomic magnetometer based on a SERF (Spin-Exchange-Relaxation-Free) effect has surpassed a superconducting quantum interference device (SQUID) to become the highest-sensitivity instrument for magnetic field measurement, and reaches a level of sub-fT, and plays a huge role in extremely weak magnetic field measurement such as heart and brain magnetic detection.

[0003] A conventional SERF atomic magnetometer can only realize single-axis magnetic field measurement, and a high-frequency modulation magnetic field introduced through a magnetic field coil can realize multi-axis magnetic field measurement. However, the method increases spin exchange relaxation and reduces the sensitivity of magnetic field measurement. Meanwhile, in arrayed SERF atomic magnetometer application, the method also causes crosstalk. SUMMARY

[0004] The present application provides a full-optical double-axis atomic magnetometer device and method based on optical frequency shift modulation, which changes a beam of mismatched pumping light into modulation light through an acousto-optic modulator, and the modulation light generates an optical frequency shift modulation magnetic field to replace the existing modulation magnetic field introduced through a magnetic field coil on the basis of realizing the original pumping function, so as to facilitate the realization of full-optical configuration and the completion of double-axis magnetic field measurement, and better application in extremely weak magnetic field measurement.

[0005] The technical solution of the present application is as follows:

[0006] The application discloses a full-optical double-axis atomic magnetometer device based on optical frequency shift modulation, and is characterized in that an acousto-optic modulator (AOM) is arranged on a pumping light path, the AOM makes the pumping light into modulated light, the modulated light passes through a fiber collimator to become collimated light, the collimated light passes through a second linear polarizer to become linearly polarized light, the linearly polarized light passes through a 1 / 4 wave plate to become circularly polarized light, the circularly polarized light enters an alkali metal cell, and is used for polarizing alkali metal atoms on one hand and acting on atoms to generate an optical frequency shift phenomenon on the other hand, the atoms experience a time-varying optical frequency shift modulation magnetic field, the optical frequency shift modulation magnetic field is used to replace a modulated magnetic field generated by a magnetic field coil to act on atomic spin precession, and the atomic spin precession is used to realize double-axis magnetic field measurement by detecting an optical rotation angle generated by optical rotation effect.

[0007] An input end of the AOM is connected with a first laser, an output end of the AOM is connected with a fiber collimator through a first reflecting mirror, the 1 / 4 wave plate is connected with the alkali metal cell through a second reflecting mirror, and the alkali metal cell is located in a non-magnetic electric heating oven.

[0008] The detection light comes from a second laser, the second laser is sequentially connected with an input side of a polarization beam splitter prism through a first linear polarizer, the alkali metal cell and a 1 / 2 wave plate, a transmission side of the polarization beam splitter prism is connected with a positive input end of a differential amplifier through a first photoelectric detector, a reflection side of the polarization beam splitter prism is sequentially connected with a negative input end of the differential amplifier through a third reflecting mirror and a second photoelectric detector, an output end of the differential amplifier is connected with a lock-in amplifier through a computer, and the lock-in amplifier is connected with a host computer through data processing of an output signal of the differential amplifier to obtain a direct current component and a first harmonic component of an electronic spin expression, wherein the direct current component is used to realize y-direction magnetic field measurement, and the first harmonic component is used to realize x-direction magnetic field measurement.

[0009] The first laser is used to generate modulated light, and the modulated light is 60GHz away from a D1 line of the used alkali metal atom; and the second laser is used to generate detection light, and the detection light is 150GHz away from the D1 line of the used alkali metal atom.

[0010] The atoms in the alkali metal cell work in a SERF state, the alkali metal atom density is in the order of 10 13 ~ 10 14 / cm 3 , the environmental magnetic field is below 1nT, and the working temperature is heated to 160 DEG C by the non-magnetic electric heating oven.

[0011] The optical frequency shift modulation magnetic field is represented as B LS cos(ω m t), wherein B LS is an amplitude of the optical frequency shift modulation magnetic field, and ω m is a modulation frequency.

[0012]

[0013] where B LS is the light frequency shift modulation magnetic field amplitude, r e is the classical electron radius, c is the speed of light, f D1 is the alkali metal D1 line oscillation intensity, γ e is the gyromagnetic ratio of electron spin, I is the laser light intensity, A is the laser spot cross-sectional area, h is the Planck constant, υ is the modulation light frequency, υ D1 is the alkali metal D1 line center frequency, Г D1 is the alkali metal D1 line pressure broadening.

[0014]

[0015]

[0016] where S x-DC (t) is the direct current component of the x-axis electron spin component S x (t) with time t, S x-ωm (t) is the first harmonic component of S x (t), γ e is the gyromagnetic ratio of electron spin, Sz is the z-axis electron spin component, J0(β) is the zero-order first kind Bessel function, J1(β) is the 1-order first kind Bessel function, B y0 is the y-axis measured magnetic field, B x0 is the x-axis measured magnetic field, R op 0 denotes the static pumping rate, R rel is the relaxation rate, ω m is the modulation frequency, R op mod is the dynamic modulation pumping rate amplitude.

[0017] An all-optical dual-axis atomic magnetometer based on light frequency shift modulation, characterized in that the all-optical dual-axis atomic magnetometer based on light frequency shift modulation is used to realize the dual-axis magnetic field measurement while realizing the all-optical configuration.

[0018] It includes changing the modulation light frequency by changing the laser temperature, changing the laser light intensity by changing the laser injection current, and changing the light frequency shift modulation magnetic field amplitude by changing the laser spot cross-sectional area.

[0019] The technical effect of the present application is as follows: the present application is a full-optical dual-axis atomic magnetometer device and method based on optical frequency shift modulation. A conventional SERF atomic magnetometer can only realize single-axis magnetic field measurement, and a high-frequency modulation magnetic field can be introduced through a magnetic field coil to realize multi-axis magnetic field measurement, but the conventional method will increase spin exchange relaxation and reduce the sensitivity of magnetic field measurement, and in the application of arrayed SERF atomic magnetometer, the conventional method will also cause crosstalk. The present application adopts a beam of mismatched pumping light, which is converted into a modulation light through an acousto-optic modulator. The light beam can generate an optical frequency shift modulation magnetic field to replace the existing modulation magnetic field introduced through the magnetic field coil on the basis of realizing the original pumping function, realize full-optical configuration, complete dual-axis magnetic field measurement, and better apply to extremely weak magnetic field measurement.

[0020] The advantages of the present application over the prior art are that the optical frequency shift modulation magnetic field is used to replace the modulation magnetic field generated by the magnetic field coil, the problems of additional spin exchange relaxation caused by the modulation magnetic field generated by the magnetic field coil and crosstalk in arrayed application are overcome, the full-optical configuration is realized, dual-axis magnetic field measurement is completed, and the present application can be better applied to extremely weak magnetic field measurement. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structure schematic diagram of the full-optical dual-axis atomic magnetometer device based on optical frequency shift modulation.

[0022] The reference signs are explained as follows: 1-optoelectronic system; 2-magnetometer probe system; 101-first laser; 102-second laser; 103-AOM (Acousto-Optic Modulator, acousto-optic modulator); 104-first mirror; 105-fiber collimator; 106-phase-locked amplifier; 107-upper computer; 201-first linear polarizer; 202-second linear polarizer; 203-1 / 4 wave plate; 204-second mirror; 205-magnetic-free electric heating oven; 206-alkali metal cell; 207-1 / 2 wave plate; 208-polarization beam splitter prism; 209-third mirror; 210-first photodetector; 211-second photodetector; 212-differential amplifier. DETAILED DESCRIPTION

[0023] The present application will be described below in combination with the drawings ( Figure 1 ) and examples.

[0024] Figure 1 is a structure schematic diagram of the full-optical dual-axis atomic magnetometer device based on optical frequency shift modulation. Reference is made to Figure 1As shown, a full-optical double-axis atomic magnetometer device based on optical frequency shift modulation includes an acousto-optic modulator AOM 103 arranged on a pumping light path, the AOM 103 makes the pumping light into modulated light, the modulated light passes through a fiber collimator 105 into collimated light, the collimated light passes through a second linear polarizer 202 into linearly polarized light, the linearly polarized light passes through a 1 / 4 wave plate 203 into circularly polarized light, the circularly polarized light enters an alkali metal cell 206, which is used for polarizing alkali metal atoms on one hand and acting on atoms to produce optical frequency shift phenomenon on the other hand, the atoms experience a time-varying optical frequency shift modulation magnetic field, which is used to replace the modulation magnetic field generated by the magnetic field coil to act on the atomic spin precession, and the atomic spin precession is used to realize double-axis magnetic field measurement by detecting the optical rotation angle generated by the optical rotation effect. The input end of the AOM 103 is connected to a first laser 101, the output end of the AOM is connected to the fiber collimator 105 through a first mirror 104, the 1 / 4 wave plate 203 is connected to the alkali metal cell 206 through a second mirror 204, and the alkali metal cell 206 is located in a non-magnetic electric heating oven 205.

[0025] The detection light comes from a second laser 102, which in turn passes through a first linear polarizer 201, the alkali metal cell 206 and a 1 / 2 wave plate 207 to connect the input side of a polarization beam splitter prism 208, the transmission side of the polarization beam splitter prism 208 is connected to the positive input end (+) of a differential amplifier 212 through a first photodetector 210, and the reflection side of the polarization beam splitter prism 208 is connected to the negative input end (-) of the differential amplifier 212 in turn through a third mirror 209 and a second photodetector 211. The output end of the differential amplifier 212 is connected to a lock-in amplifier 106 through a lock-in amplifier 106, and the lock-in amplifier 106 is connected to a host computer 107. The lock-in amplifier 106 obtains the direct current component and the first harmonic component of the electronic spin expression by data processing of the output signal of the differential amplifier 212, wherein the direct current component is used to realize y-direction magnetic field measurement, and the first harmonic component is used to realize x-direction magnetic field measurement.

[0026] The first laser 101 is used to generate modulated light, and the wavelength of the modulated light is 60GHz away from the D1 line of the alkali metal atoms used, and the second laser is used to generate detection light, and the wavelength of the detection light is 150GHz away from the D1 line of the alkali metal atoms used. The atoms in the alkali metal cell 206 work in the SERF state, the density of alkali metal atoms is in the order of 10 13 ~10 14 cm 3 -3 , the environmental magnetic field is below 1nT, and the working temperature is heated to 160℃ by the non-magnetic electric heating oven.

[0027] The optical frequency shift modulation magnetic field is represented as B LS cos(ωm t), where B LS is the light frequency shift modulation magnetic field amplitude, ω m is the modulation frequency.

[0028]

[0029] where B LS is the light frequency shift modulation magnetic field amplitude, r e is the classical electron radius, c is the speed of light, f D1 is the alkali D1 line oscillation strength, γ e is the gyromagnetic ratio of electron spin, I is the laser light intensity, A is the laser spot cross-sectional area, h is the Planck constant, υ is the modulation light frequency, υ D1 is the alkali D1 line center frequency, Г D1 is the alkali D1 line pressure broadening.

[0030]

[0031]

[0032] where S x-DC (t) is the direct current component of the x-axis electron spin component S x (t) with time t, S x-ωm (t) is the first harmonic component of S x (t), γ e is the gyromagnetic ratio of electron spin, Sz is the z-axis electron spin component, J0(β) is the zero-order first kind Bessel function, J1(β) is the 1-order first kind Bessel function, B y0 is the y-axis measured magnetic field, B x0 is the x-axis measured magnetic field, R op 0 denotes the static pumping rate, R rel is the relaxation rate, ω m is the modulation frequency, R op mod is the dynamic modulation pumping rate amplitude.

[0033] An all-optical double-axis atomic magnetometer implementation method based on light frequency shift modulation, which utilizes the above-mentioned all-optical double-axis atomic magnetometer device based on light frequency shift modulation to realize double-axis magnetic field measurement while realizing all-optical configuration. It includes changing the modulation light frequency by changing the laser temperature, changing the laser light intensity by changing the laser injection current, and changing the light frequency shift modulation magnetic field amplitude by changing the laser spot cross-sectional area.

[0034] The application provides a full-optical double-axis atomic magnetometer device based on optical frequency shift modulation, which comprises an optoelectronic system 1 and a magnetometer probe system 2; wherein the optoelectronic system 1 comprises a first laser 101, a second laser 102, an AOM (Acousto-Optic Modulator) 103, a first mirror 104, a fiber collimator 105, a lock-in amplifier 106 and an upper computer 107; the magnetometer probe system 2 comprises a first linear polarizer 201, a second linear polarizer 202, a 1 / 4 wave plate 203, a second mirror 204, a non-magnetic electric heating oven 205, an alkali metal cell 206, a 1 / 2 wave plate 207, a polarization beam splitter prism 208, a third mirror 209, a first photoelectric detector 210, a second photoelectric detector 211 and a differential amplifier 212; in the device, the atoms in the alkali metal cell 206 need to work in the SERF state; the spatial light emitted by the first laser 101 becomes modulated light after passing through the AOM 103, is reflected by the first mirror 104, enters the fiber collimator 105 to become collimated light, then enters the magnetometer probe system 2 through a polarization maintaining fiber, and becomes circularly polarized modulated light after passing through the second linear polarizer 202 and the 1 / 4 wave plate 203, wherein the second linear polarizer 202 is used for improving the linear polarization degree of the light beam, and the 1 / 4 wave plate 203 is used for converting linearly polarized light into circularly polarized light; then the light beam is reflected by the second mirror 204 to the alkali metal cell 206, which is used for polarizing alkali metal atoms, and at the same time, the light beam acts on the atoms to produce an optical frequency shift phenomenon, and the atoms feel a time-varying optical frequency shift modulation magnetic field, which can be used to replace the modulation magnetic field generated by the magnetic field coil and acts on the atomic spin precession; the laser emitted by the second laser 102 enters the magnetometer probe system 2 through a polarization maintaining fiber, passes through the first linear polarizer 201 to improve the linear polarization degree, and is incident on the alkali metal cell 206; the linearly polarized detection light passes through the polarized alkali metal atoms and appears a rotatory effect, and the polarization balance beam splitting method is used to detect the rotatory angle generated by the atomic spin precession; after the linearly polarized detection light exits the alkali metal cell 206, it first passes through the 1 / 2 wave plate 207, and the 1 / 2 wave plate 207 is used for adjusting the polarization axis of the detection light to an angle of 45° with the two optical axes of the polarization beam splitter prism 208; the polarization beam splitter prism 208 divides the exiting detection light into transmitted light and reflected light with a phase difference of 90°, then the transmitted light is incident on the first photoelectric detector 210, and the reflected light is reflected by the third mirror 209 to the second photoelectric detector 211; the first photoelectric detector 210 and the second photoelectric detector 211 convert the detected light signals into electric signals, then the two signals are respectively connected to the two ends of the differential amplifier 212, the differential amplifier 212 differentiates and amplifies the two signals, and outputs to the lock-in amplifier 106 in the optoelectronic system 1 for data processing, and then the upper computer 107 completes data receiving and display.The lock-in amplifier 106 is used to obtain the direct current component and the first harmonic component, wherein the direct current component is used to realize the y-direction magnetic field measurement, and the first harmonic component is used to realize the x-direction magnetic field measurement.

[0035] The application also provides a full-optical double-axis atomic magnetometer method based on optical frequency shift modulation. The method uses the full-optical double-axis atomic magnetometer device based on optical frequency shift modulation to realize the atomic magnetometer, and comprises the following steps: the atoms in the alkali metal cell 206 need to work in the SERF state; the spatial light emitted by the first laser 101 becomes modulated light after passing through the AOM 103, is reflected by the first reflecting mirror 104, becomes collimated light after entering the optical fiber collimator 105, then enters the magnetometer probe system 2 through the polarization maintaining optical fiber, and becomes circularly polarized modulated light after passing through the second linear polarizer 202 and the 1 / 4 wave plate 203, wherein the second linear polarizer 202 is used to improve the linear polarization degree of the light beam, and the 1 / 4 wave plate 203 is used to convert the linearly polarized light into circularly polarized light; then the light beam is reflected to the alkali metal cell 206 by the second reflecting mirror 204, which is used to polarize the alkali metal atoms, and at the same time, the light beam acts on the atoms to produce the optical frequency shift phenomenon, and the atoms feel a time-varying optical frequency shift modulation magnetic field, which can be used to replace the modulation magnetic field generated by the magnetic field coil and acts on the atomic spin precession; the laser emitted by the second laser 102 enters the magnetometer probe system 2 through the polarization maintaining optical fiber, passes through the first linear polarizer 201 to improve the linear polarization degree, and is incident on the alkali metal cell 206, and the light beam is the incident detection light; the linearly polarized detection light passes through the polarized alkali metal atoms and appears the optical rotation effect, and the polarization balance beam splitting method is used to detect the optical rotation angle generated by the atomic spin precession; the linearly polarized detection light exits the alkali metal cell 206 and first passes through the 1 / 2 wave plate 207, and the 1 / 2 wave plate 207 is used to adjust the polarization axis of the detection light to be at an angle of 45° with the two optical axes of the polarization beam splitter prism 208; the polarization beam splitter prism 208 divides the exiting detection light into transmitted light and reflected light with a phase difference of 90°, and then the transmitted light is incident on the first photodetector 210, and the reflected light is reflected to the second photodetector 211 by the third reflecting mirror 209; the first photodetector 210 and the second photodetector 211 convert the detected light signals into electrical signals, and then the two signals are respectively connected to the two ends of the differential amplifier 212, the differential amplifier 212 differentiates and amplifies the two signals, and outputs to the lock-in amplifier 106 in the photoelectric system 1 for data processing, and then the host computer 107 completes data receiving and display; the lock-in amplifier 106 is used to obtain the direct current component and the first harmonic component, wherein the direct current component is used to realize the y-direction magnetic field measurement, and the first harmonic component is used to realize the x-direction magnetic field measurement. The non-magnetic electric heating oven 205 is used to heat the alkali metal cell 206 at high temperature.

[0036] In the above-mentioned all-optical biaxial atomic magnetometer based on optical frequency shift modulation, the first laser 101 is used to generate the modulation light, and the wavelength of the modulation light is 60 GHz away from the D1 line of the alkali metal atom; and the second laser 102 is used to generate the detection light, and the wavelength of the detection light is 150 GHz away from the D1 line of the alkali metal atom.

[0037] In the above-mentioned all-optical biaxial atomic magnetometer based on optical frequency shift modulation, preferably, the first laser 101 and the second laser 102 comprise tunable lasers, and the temperature and the injection current of the lasers can be greatly adjusted. The frequency of the modulation light can be changed by changing the temperature of the laser, the intensity of the laser light can be changed by changing the injection current of the laser, or the cross-sectional area of the laser light spot can be changed, and then the amplitude of the optical frequency shift modulation magnetic field is changed.

[0038] In the above-mentioned all-optical biaxial atomic magnetometer based on optical frequency shift modulation, the atoms in the alkali metal cell 206 need to work in the SERF state, including that the density of the alkali metal atoms is in the order of 10 13 ~ 10 14 cm 3 -2, the environmental magnetic field is below 1 nT, and the working temperature is heated to 160°C by a non-magnetic electric heating oven.

[0039] In the above-mentioned all-optical biaxial atomic magnetometer based on optical frequency shift modulation, the optical frequency shift modulation magnetic field used to generate the modulation magnetic field instead of the magnetic field coil can be written as B LS cos(ω m t), wherein B LS is the amplitude of the optical frequency shift modulation magnetic field, ω m is the modulation frequency; the amplitude B LS of the optical frequency shift modulation magnetic field generated by the modulation light can be represented as wherein r e is the classical electron radius, c is the speed of light, f D1 is the oscillation intensity of the D1 line of the alkali metal, γ e is the gyromagnetic ratio of the electron spin, I is the laser light intensity, A is the cross-sectional area of the laser light spot, h is the Planck constant, υ is the frequency of the modulation light, υ D1 is the central frequency of the D1 line of the alkali metal, and Г D1 is the pressure broadening of the D1 line of the alkali metal. When the first laser 101 is a preferred tunable laser, the frequency υ of the modulation light can be changed by changing the temperature of the laser, the intensity I of the laser light can be changed by changing the injection current of the laser, or the cross-sectional area of the laser light spot can be changed, and then the amplitude B LS of the optical frequency shift modulation magnetic field is changed.

[0040] The application relates to a full-optical double-axis atomic magnetometer device and method based on optical frequency shift modulation. A conventional SERF atomic magnetometer can only realize single-axis magnetic field measurement, and a high-frequency modulation magnetic field can be introduced through a magnetic field coil to realize multi-axis magnetic field measurement. However, the method can increase spin exchange relaxation and reduce the sensitivity of magnetic field measurement. Meanwhile, in the application of an arrayed SERF atomic magnetometer, the method can also cause crosstalk. The full-optical double-axis atomic magnetometer device and method based on optical frequency shift modulation disclosed in the application adopts a beam of mismatched pumping light, and the light beam becomes a modulation light through an acousto-optic modulator. On the basis of realizing the original pumping function, the light beam simultaneously generates an optical frequency shift modulation magnetic field to replace the existing modulation magnetic field introduced through a magnetic field coil, realizes full-optical configuration, can complete double-axis magnetic field measurement, and can be better applied to extremely weak magnetic field measurement. The specific principle is as follows:

[0041] As shown in Figure 1 , the z-axis is the pumping direction and the optical frequency shift modulation magnetic field direction, and the x-axis is the detection direction. The x-axis component of the magnetic field vector B is denoted as B x , the y-axis component is denoted as B y , the z-axis component is denoted as B z , the x-axis to-be-measured magnetic field is denoted as B x0 , the y-axis to-be-measured magnetic field is denoted as B y0 , the z-axis to-be-measured magnetic field is denoted as B z0 , and the z-axis optical frequency shift modulation magnetic field is denoted as B LS cos(omega m t), wherein B LS is the optical frequency shift modulation magnetic field amplitude, omega m is the modulation frequency. After active magnetic compensation is completed in advance, B x =B x0 , B y =B y0 , B z =B z0 +B LS cos(omega m t), wherein t is a time variable. The pumping rate R op (t) is denoted as R op (t)=R op 0 +R op mod cos(omega m t), wherein R op 0 represents a static pumping rate, R op mod cos(omega m t) represents a dynamic modulation pumping rate generated by the z-axis modulation light, R op mod is the dynamic modulation pumping rate amplitude, and omega mfor the modulation frequency, t is the time variable. The Bloch equation describing the electron spin S is expanded into the form of x-axis electron spin component Sx, y-axis electron spin component Sy, and z-axis electron spin component Sz:

[0042]

[0043]

[0044]

[0045] where q is a slowing factor, γ e is the gyromagnetic ratio of the electron spin, R rel is the relaxation rate.

[0046] Solving the above Bloch equation, the zero-order parametric resonance response of the time-varying x-axis electron spin component S x (t) is obtained as:

[0047]

[0048] where β is the modulation coefficient, J0(β) is the zero-order first kind Bessel function, J n (β) is the n-order first kind Bessel function, and n represents the order of the first kind Bessel function.

[0049] Therefore, the direct current component and the first harmonic component of the time-varying x-axis electron spin component S x (t) are:

[0050]

[0051]

[0052] where S x-DC (t) is the direct current component of the time-varying x-axis electron spin component S x (t), that is, the value of formula (4) when the order n of the first kind Bessel function is 0, S x-ωm (t) is the first harmonic component of the time-varying x-axis electron spin component S x (t), that is, the value of formula (4) when the order n of the first kind Bessel function is ±1.

[0053] When the remanence in the z direction is compensated to 0, the above formula can be simplified as:

[0054]

[0055]

[0056] Therefore, when using the method, S x-DC When detecting the y-direction magnetic field, the x-direction magnetic field crosstalk is contained in the signal, and S x-ωm When detecting the x-direction magnetic field, the y-direction magnetic field crosstalk is contained in the signal. However, the crosstalk can be reduced to less than 5% by increasing the detuning and increasing the light intensity or reducing the light spot cross-sectional area. The crosstalk of less than 5% does not affect the actual application effect, and therefore the all-optical dual-axis atomic magnetometer method based on optical frequency shift modulation is feasible, and the dual-axis magnetic field measurement can be realized.

[0057] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art. It is pointed out that the above description is helpful for those skilled in the art to understand the present application, but does not limit the protection scope of the present application. Any implementation of equivalent replacement, modification, improvement and / or deletion of the above description without departing from the essential content of the present application falls within the protection scope of the present application.

Claims

1. A fully optical biaxial atomic magnetometer device based on optical frequency shift modulation, characterized in that, The system includes an acousto-optic modulator (AOM) installed in the pump optical path. The AOM converts the pump light into modulated light. The modulated light passes through an optical fiber collimator to become collimated light. The collimated light passes through a second linear polarizer to become linearly polarized light. The linearly polarized light passes through a quarter-wave plate to become circularly polarized light. The circularly polarized light enters the alkali metal gas cell and is used to polarize alkali metal atoms on one hand, and on the other hand, it acts on the atoms to produce an optical frequency shift phenomenon. The atoms experience a time-varying optical frequency shift modulated magnetic field. The optical frequency shift modulated magnetic field is used to replace the modulated magnetic field generated by the magnetic field coil to act on the spin precession of the atoms. The spin precession of the atoms is used to realize the biaxial magnetic field measurement by detecting the optical rotation angle generated by the optical rotation effect. The input end of the AOM is connected to the first laser, the output end of the AOM is connected to the fiber collimator through the first reflector, the quarter wave plate is connected to the alkali metal gas chamber through the second reflector, and the alkali metal gas chamber is located in a non-magnetic electric heating oven. The detection light originates from a second laser, which is connected to the input side of a polarizing beam splitter via a first linear polarizer, the alkali metal gas cell, and a half-wave plate. The transmission side of the polarizing beam splitter is connected to the positive input of a differential amplifier via a first photodetector. The reflection side of the polarizing beam splitter is connected to the negative input of the differential amplifier via a third mirror and a second photodetector. The output of the differential amplifier is connected to a host computer via a lock-in amplifier. The lock-in amplifier processes the output signal of the differential amplifier to obtain the DC component and the first harmonic component of the electron spin expression. The DC component is used to measure the magnetic field in the y-direction, and the first harmonic component is used to measure the magnetic field in the x-direction. The first laser is used to generate modulation light, the wavelength of which is detuned by 60 GHz near the D1 line of the alkali metal atom used. The second laser is used to generate detection light, the wavelength of which is detuned by 150 GHz near the D1 line of the alkali metal atom used.

2. The all-optical biaxial atomic magnetometer device based on optical frequency shift modulation according to claim 1, characterized in that, The atoms in the alkali metal gas chamber operate in the SERF state, and the alkali metal atom density is 10. 13 ~10 14 pcs / cm 3 The magnitude is below 1nT, the ambient magnetic field is below 1nT, and the working temperature is heated to 160℃ by a non-magnetic electric heating oven.

3. The all-optical biaxial atomic magnetometer device based on optical frequency shift modulation according to claim 1, characterized in that, The optical frequency shift modulation magnetic field is represented by B. LS cos(ω m t), where B LS ω is the amplitude of the optical frequency shift modulation magnetic field. m This is the modulation frequency.

4. The all-optical biaxial atomic magnetometer device based on optical frequency shift modulation according to claim 1, characterized in that, Among them B LS r is the amplitude of the optical frequency shift modulation magnetic field. e Let f be the classical electron radius, c be the speed of light, and f be the velocity of light. D1 The oscillation intensity of the alkali metal D1 line, γ e Let I be the gyromagnetic ratio of the electron spin, I be the laser intensity, A be the cross-sectional area of ​​the laser spot, h be Planck's constant, and υ be the modulation frequency. D1 The center frequency of the alkali metal D1 line is Γ. D1 This broadens the pressure of the D1 line for alkali metals.

5. The all-optical biaxial atomic magnetometer device based on optical frequency shift modulation according to claim 1, characterized in that, Where S x-DC (t) is the x-axis electron spin component S that varies with time t. x DC component of (t), S x-ωm (t) is S x The first harmonic component of (t), γ e Let Sz be the gyromagnetic ratio of the electron spin, Sz be the z-axis electron spin component, J0(β) be the zeroth-order Bessel function of the first kind, J1(β) be the first-order Bessel function of the first kind, and Bz be the electron spin ratio. y0 The magnetic field to be measured is along the y-axis, B. x0 The magnetic field to be measured along the x-axis is R. op 0 R represents the static pumping rate. rel Let ω be the relaxation rate. m For the modulation frequency, R op mod This is for dynamically modulating the pump rate amplitude.

6. A method for implementing an all-optical biaxial atomic magnetometer based on optical frequency shift modulation, characterized in that, Using the all-optical biaxial atomic magnetometer device based on optical frequency shift modulation as described in any one of claims 1-5, biaxial magnetic field measurement can be completed while achieving an all-optical configuration.

7. The method for implementing an all-optical biaxial atomic magnetometer based on optical frequency shift modulation according to claim 6, characterized in that, This includes changing the modulation frequency by altering the laser temperature, changing the laser intensity by altering the laser injection current, and changing the amplitude of the optical frequency shift modulation magnetic field by altering the cross-sectional area of ​​the laser spot.

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