An atomic magnetometer device and method based on detecting optical frequency detuning modulation

Abstract

A kind of atomic magnetometer device and method based on detecting light frequency detuning amount modulation, using red and blue detuning linear polarization modulation light as detection light to realize the modulation of atomic magnetometer rotation angle.The modulation light is red detuned and blue detuned under the condition of keeping the optical power unchanged, and the frequency is detuned by the same amount relative to the D1 line resonance frequency of alkali metal atom, so that the rotation angle is quickly switched between positive deflection and negative deflection, the modulation of rotation angle is realized, and the magnetometer output signal containing the information of the measured magnetic field is obtained by polarization differential detection and lock-in amplification technology.Compared with the conventional atomic magnetometer modulation method, the present application indirectly realizes the modulation of rotation angle by red and blue detuning modulation of detection light, avoids introducing modulation magnetic field, suppresses optical power noise and isolates low frequency noise, and compared with the unmodulated mode, the present application enhances the amplitude of rotation angle and improves the sensitivity of magnetometer.

Description

TECHNICAL FIELD

[0001] The application discloses an atomic magnetometer device and method based on detection of light frequency detuning modulation, and belongs to the technical field of atomic magnetometers. BACKGROUND

[0002] With the development of science into the quantum era, the emergence and development of atomic magnetometers provide a new direction for magnetic field detection and show great potential in the field of extremely weak magnetic field measurement. Atomic magnetometers use the characteristics and laws of atoms in the optical field and the magnetic field to measure the magnetic field, and play an increasingly important role in the fields of biomedicine, industrial production, national defense construction and frontier physics research.

[0003] SERF (Spin-Exchange Relaxation-Free) atomic magnetometers have extremely high theoretical sensitivity and miniaturization potential in the field of extremely weak magnetic field detection, so that extremely weak magnetic field detection enters the era of sub-fT level. The low-frequency sensitivity of the SERF atomic magnetometer is largely limited by low-frequency noise. In order to improve the low-frequency sensitivity of the SERF atomic magnetometer, in addition to improving the signal strength, a modulation method is usually used. One commonly used modulation method is to introduce magnetic field modulation, but this method will cause additional atomic relaxation, resulting in a decrease in overall sensitivity. Another commonly used modulation method is to directly modulate the optical rotation angle after the gas chamber through an external modulator, but this modulation method has a small modulation angle of the optical rotation angle, which will cause the output optical rotation angle signal of the magnetometer to decrease, and the modulator has a large volume and high cost, which is not conducive to the miniaturization and portability of the atomic magnetometer. SUMMARY

[0004] The application proposes an atomic magnetometer device and method based on detection of light frequency detuning modulation to solve the problem of limited sensitivity improvement of the classical magnetometer device based on modulation. The red and blue detuned linearly polarized modulation light is used for detecting the optical rotation angle. The frequency of the modulation light is detuned by the same amount of red and blue detuning relative to the D1 line resonance frequency of the alkali metal atom under the condition that the optical power remains unchanged, so that the optical rotation angle is switched between positive deflection and negative deflection, the modulation of the optical rotation angle signal is realized, the optical rotation angle signal after modulation is converted into an electric signal proportional to the optical rotation angle by a photoelectric detector, the first harmonic signal is extracted from the electric signal by a lock-in amplifier as the output signal of the magnetometer, the suppression of the optical power noise and the isolation of the low-frequency noise can be realized, and the amplitude of the optical rotation angle signal and the sensitivity of the magnetometer are further improved compared with the non-modulation mode.

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

[0006] The application discloses an atomic magnetometer device based on detecting light frequency detuning modulation, and is characterized in that the device comprises a photoelectric measurement and control system connected with an atomic magnetometer table head system, wherein the photoelectric measurement and control system comprises a red detuning light path system, a blue detuning light path system and a pumping light path system; the red detuning light path system and the blue detuning light path system jointly form red and blue detuning modulation light as detection light input into the magnetometer table head system; and the red and blue detuning modulation light is combined into combined light in an interlaced connection mode by switching the red detuning modulation light and the blue detuning modulation light.

[0007] The red detuning light path system comprises a first laser, a first acousto-optic modulator, a first half-wave plate, a first quarter-wave plate and a first light barrier connected in sequence, the first light barrier is connected with a first input side of a depolarization beam splitter prism, the first acousto-optic modulator is connected with a first function signal generator through a first acousto-optic modulator driver, the blue detuning light path system comprises a second laser, a second acousto-optic modulator, a second half-wave plate, a second quarter-wave plate and a second light barrier connected in sequence, the second light barrier is connected with a second input side of the depolarization beam splitter prism through a mirror, the second acousto-optic modulator is connected with the first function signal generator through a second acousto-optic modulator driver, and an output side of the depolarization beam splitter prism is connected with the atomic magnetometer table head system through a fiber coupler and a detection light polarization maintaining optical fiber in sequence.

[0008] The pumping light path system comprises a third laser and a pumping light polarization maintaining optical fiber connected in sequence, and the pumping light polarization maintaining optical fiber is connected with the atomic magnetometer table head system.

[0009] The atomic magnetometer table head system comprises an alkali metal cell, the alkali metal cell is located in a non-magnetic electric heating oven, the non-magnetic electric heating oven is located in a three-axis magnetic compensation coil, the three-axis magnetic compensation coil is connected with a second function signal generator, a detection light input side of the alkali metal cell is connected with a detection light polarization maintaining optical fiber through a first linear polarizer, a detection light output side of the alkali metal cell sequentially passes through a third half-wave plate, a lateral displacement polarization beam splitter prism, a photoelectric detector, a differential amplifier and a lock-in amplifier to form an atomic magnetometer output signal, and a pumping light input side of the alkali metal cell is connected with a pumping light polarization maintaining optical fiber through a third quarter-wave plate and a second linear polarizer in sequence.

[0010] The first function signal generator in the photoelectric measurement and control system generates two square wave signals with the same frequency and a phase difference of 180°, and the two square wave signals are input into acousto-optic modulator drivers in the red detuning and blue detuning light path systems respectively, so that the control of the modulation frequency of the acousto-optic modulator is realized.

[0011] The red detuning modulation light and the blue detuning modulation light are coupled to the slow axis of the detection light optical fiber by adjusting the polarization state, and the light powers of the red detuning modulation light and the blue detuning modulation light are the same after the light passes through the optical fiber.

[0012] The lock-in amplifier demodulates the first harmonic component from the differential signal as the detection result of the magnetometer on the magnetic field size.

[0013] Comprising:

[0014]

[0015] where v mod is the frequency of the modulated probe light, v0 is the alkali D1 line resonance frequency, Δv is the frequency detuning, Δv = |v mod -v0|, ω m is the modulation frequency of the acousto-optic modulator, i.e. the switching frequency of v mod , t is time, and k is a positive integer.

[0016] Comprising:

[0017]

[0018] where θ mod is the modulated optical rotation angle, l is the cell length, r e is the classical electron radius, n is the alkali atom number density, c is the speed of light, f D1 is the alkali D1 line resonance strength, P x is the alkali atom polarizability projection along the x direction, Δv is the frequency detuning, Γ pr is the atomic cell pressure broadening value, ω m is the modulation frequency of the acousto-optic modulator, and t is time.

[0019] Comprising:

[0020]

[0021] where V out is the first harmonic signal demodulated by the lock-in amplifier from the differential amplified signal, i.e. the atomic magnetometer output signal, e is the natural constant, l is the cell length, r e is the classical electron radius, n is the alkali atom number density, c is the speed of light, f D1 is the alkali D1 line resonance strength, Δv is the frequency detuning, Γ pr is the atomic cell pressure broadening value, P0 is the initial polarizability, R OP is the pumping rate, R rel is the transverse relaxation rate, γ e is the electron gyromagnetic ratio, B x , B y and B z are the components of the measured magnetic field vector along the x, y and z axes respectively, B is the size of the measured magnetic field, ω mThe modulation frequency of the acousto-optic modulator is the change frequency of v mod .

[0022] The application discloses an atomic magnetometer based on light frequency detuning modulation, and relates to the technical field of atomic magnetometers.

[0023] Step 1, the first laser and the second laser of the red-detuned light path and the blue-detuned light path are respectively adjusted to emit symmetrical laser about the alkali metal atom D1 line resonance frequency, two frequency ω m and phase difference 180° square wave signals are generated by a first function signal generator and input into the acousto-optic modulator drivers in the two light paths to control the corresponding acousto-optic modulators to generate modulated light, and the two modulated 0th diffraction lights are coupled into the slow axis of the detection light polarization maintaining optical fiber, and the modulated linearly polarized light emitted through the detection light polarization maintaining optical fiber enters the gas chamber as detection light through the first linear polarizer in the head system.

[0024] Step 2, the light powers and wavelengths of the first laser and the second laser are adjusted so that the red-detuned modulated light and the blue-detuned modulated light entering the head system through the detection light polarization maintaining optical fiber have the same light power.

[0025] Step 3, the laser emitted by the third laser is adjusted to be the alkali metal atom D1 line resonance frequency, the laser enters the head system through the pumping light polarization maintaining optical fiber and forms circularly polarized light through the second linear polarizer and the quarter-wave plate in the head system, and the circularly polarized light is used as pumping light to irradiate the gas chamber.

[0026] Step 4, the gas chamber is heated by a non-magnetic electric heating oven, and the three-axis magnetic compensation coil is controlled by a second function signal generator to perform magnetic compensation on the gas chamber.

[0027] Step 5, when the measured magnetic field is not 0, the light intensities sensed by the two photodetectors in the head system have a difference, the difference is output to a lock-in amplifier through a differential amplifier, and a first harmonic component is demodulated by lock-in amplification technology in the lock-in amplifier at a frequency ω m to serve as an atomic magnetometer output signal.

[0028] The technical effects of the application are as follows: the atomic magnetometer device and method based on light frequency detuning modulation modulate the detection light frequency by taking the red-detuned linearly polarized modulated light and the blue-detuned linearly polarized modulated light as the magnetometer detection light, thereby realizing modulation of the optical rotation angle. The first harmonic signal is extracted from the modulated electrical signal corresponding to the optical rotation angle to serve as the atomic magnetometer output signal, the optical power noise is suppressed, the low-frequency noise is isolated, the optical rotation angle signal is enhanced to a certain extent compared with the conventional non-modulation mode, and the low-frequency sensitivity of the magnetometer is improved.

[0029] The present application has the following advantages compared with the prior art:

[0030] (1) Compared with the conventional optical angle modulation method, such as using an external modulator, such as a Faraday modulator, a photoelastic modulator, etc., to realize optical angle modulation, the present application indirectly realizes modulation of the optical angle by an optical method, which can be directly integrated into a small size, and has the technical advantages of easy miniaturization and arraying;

[0031] (2) Compared with the conventional atomic magnetometer without modulation mode, the present application enhances the optical angle signal in principle, thereby enhancing the signal strength output by the atomic magnetometer and improving the signal-to-noise ratio;

[0032] (3) Compared with the method of modulating the optical angle by a magnetic field, the present application avoids the problem of increased atomic spin exchange relaxation and decreased total sensitivity caused by the introduction of a modulation magnetic field. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic structural diagram of an atomic magnetometer device based on detection of optical frequency detuning modulation according to the present application.

[0034] The reference signs are explained as follows: 1-optoelectronic measurement and control system; 2-atomic magnetometer meter system; 1a-red detuning light path system; 1b-blue detuning light path system; 101-first laser; 102-first acousto-optic modulator; 103-first half-wave plate; 104-first quarter-wave plate; 105-first diaphragm; 106-polarization splitting prism; 107-fiber coupler; 108-detection light polarization maintaining fiber; 109-first function signal generator; 110-first acousto-optic modulator driver; 111-second acousto-optic modulator driver; 112-second laser; 113-second acousto-optic modulator; 114-second half-wave plate; 115-second quarter-wave plate; 116-second diaphragm; 117-reflection mirror; 118-third laser; 119-pumping light polarization maintaining fiber; 120-differential amplifier; 121-phase-locked amplifier; 122-atomic magnetometer output signal; 123-second function signal generator; 201-alkali metal cell; 202-magnetic-free electric heating oven; 203-three-axis magnetic compensation coil; 204-third half-wave plate; 205-lateral displacement polarization splitting prism; 206-optoelectronic detector; 207-second linear polarizer; 208-third quarter-wave plate; 209-first linear polarizer. DETAILED DESCRIPTION

[0035] The present application will be described below in conjunction with the drawings Figure 1 and examples.

[0036] Figure 1is a schematic diagram of an atomic magnetometer device based on detecting the amount of frequency detuning modulation of light according to the present application. Referring to Figure 1 As shown in the figure, an atomic magnetometer device based on detecting the amount of frequency detuning modulation of light comprises a photoelectric measurement and control system 1 connected to an atomic magnetometer watch system 2, the photoelectric measurement and control system 1 comprises a red detuning light path system 1a, a blue detuning light path system 1b and a pumping light path system, the red detuning light path system 1a and the blue detuning light path system 1b jointly form red and blue detuning modulation light as the detection light input of the magnetometer watch system 2, and the red and blue detuning modulation light is the switching of red and blue detuning modulation light into interlaced and connected combined light.

[0037] The red detuning light path system 1a comprises a first laser 101, a first acousto-optic modulator 102, a first half-wave plate 103, a first quarter-wave plate 104 and a first light stop 105 connected in sequence, the first light stop 105 is connected to the first input side of a depolarization beam splitter prism 106, the first acousto-optic modulator 102 is connected to a first function signal generator 109 through a first acousto-optic modulator driver 110, the blue detuning light path system 1b comprises a second laser 112, a second acousto-optic modulator 113, a second half-wave plate 114, a second quarter-wave plate 115 and a second light stop 116 connected in sequence, the second light stop 116 is connected to the second input side of the depolarization beam splitter prism 106 through a mirror 117, the second acousto-optic modulator 113 is connected to the first function signal generator 109 through a second acousto-optic modulator driver 111, and the output side of the depolarization beam splitter prism 106 is connected to the atomic magnetometer watch system 2 through a fiber coupler 107 and a detection light polarization maintaining fiber 108 in sequence. The pumping light path system comprises a third laser 118 and a pumping light polarization maintaining fiber 119 connected in sequence, and the pumping light polarization maintaining fiber 119 is connected to the atomic magnetometer watch system 2.

[0038] The atomic magnetometer watch system 2 comprises an alkali metal cell 201, the alkali metal cell 201 is located in a non-magnetic electric heating oven 202, the non-magnetic electric heating oven 202 is located in a three-axis magnetic compensation coil 203, the three-axis magnetic compensation coil 203 is connected to a second function signal generator 123, the detection light input side of the alkali metal cell 201 is connected to the detection light polarization maintaining fiber 108 through a first linear polarizer 209, and the detection light output side of the alkali metal cell 201 is connected to the atomic magnetometer watch system 2 through a third half-wave plate 204, a lateral displacement polarization beam splitter prism 205, a photodetector 206, a differential amplifier 120 and a lock-in amplifier 121 in sequence to form an atomic magnetometer output signal 122, and the pumping light input side of the alkali metal cell 201 is connected to the pumping light polarization maintaining fiber 119 through a third quarter-wave plate 208 and a second linear polarizer 207 in sequence.

[0039] The first function signal generator 109 in the photoelectric measurement and control system 1 generates two square wave signals with the same frequency and a phase difference of 180°, which are input into the sound-light modulator drivers in the red and blue detuned light paths respectively, so as to control the modulation frequency of the sound-light modulator. The red and blue detuned modulation lights are coupled into the slow axis of the detection light fiber by adjusting the polarization state, and the light powers of the red and blue detuned modulation lights are the same after passing through the fiber. The lock-in amplifier 121 demodulates the first harmonic component from the differential signal as the detection result of the magnetometer on the magnetic field size.

[0040] The method for implementing the atomic magnetometer based on the frequency detuning modulation of detection light, characterized by comprising the atomic magnetometer based on the frequency detuning modulation of detection light and the following steps.

[0041] Step 1: Adjust the light emitted from the first laser and the second laser in the red and blue detuned light paths to be the laser symmetrical to the D1 line resonance frequency of the alkali metal atom, generate two square wave signals with the same frequency and a phase difference of 180° by the first function signal generator, and input the square wave signals into the sound-light modulator drivers in the two light paths respectively to control the corresponding sound-light modulators to generate modulation light. m Step 2: Adjust the light power and wavelength of the first laser and the second laser, so that the light powers of the red and blue detuned modulation lights entering the head system through the detection light polarization maintaining fiber are the same. Step 3: Adjust the light frequency emitted from the third laser to be the D1 line resonance frequency of the alkali metal atom, and the light enters the head system through the pumping light polarization maintaining fiber and forms circularly polarized light through the second linear polarizer and the quarter wave plate in the head system, and the circularly polarized light is used as the pumping light to irradiate the cell. Step 4: Heat the cell by the non-magnetic electric oven and control the magnetic compensation of the cell by the second function signal generator through the three-axis magnetic compensation coil. Step 5: When the magnetic field to be measured is not 0, the light intensities sensed by the two photodetectors in the head system have a difference, and the difference is output to the lock-in amplifier through the differential amplifier, and the first harmonic component is demodulated by the lock-in amplification technology in the lock-in amplifier as the output signal of the atomic magnetometer. m

[0042] The following formula is included:

[0043]

[0044] Where v mod is the frequency of the modulated detection light, v0 is the D1 line resonance frequency of the alkali metal, and Δv is the frequency detuning, Δv = |v mod ​v0, ω m is the modulation frequency of the acousto-optic modulator, v mod is the switching frequency, t is time, k is a positive integer, θ mod is the modulated optical rotation angle, l is the cell length, r e is the classical electron radius, n is the alkali metal atomic number density, c is the speed of light, f D1 is the resonance intensity of the alkali metal D1 line, P x is the projection of the alkali metal atomic polarizability along the x direction, Γ pr is the atomic cell pressure broadening value, V out is the first harmonic signal demodulated from the differential amplified signal by the lock-in amplifier, i.e., the atomic magnetometer output signal, e is the natural constant, P0 is the initial polarizability, R OP is the pumping rate, R rel is the transverse relaxation rate, γ e is the electron gyromagnetic ratio, B x , B t and B z are the components of the measured magnetic field vector along the x, y and z axes, respectively, B is the magnitude of the measured magnetic field,

[0045] An atomic magnetometer device and method based on detecting the frequency detuning amount modulation, using red and blue detuned polarized modulation light as detection light to realize the modulation of the optical rotation angle of the atomic magnetometer. The modulation light is subjected to red and blue detuning transformation with the same detuning amount relative to the resonance frequency of the alkali metal D1 line under the condition that the optical power remains unchanged, so that the optical rotation angle is quickly switched between positive and negative deflection, the modulation of the optical rotation angle is realized, and the optical rotation angle signal after modulation is obtained through polarization differential detection and lock-in amplification technology. The magnetometer output signal containing the measured magnetic field information is obtained. Compared with the conventional atomic magnetometer modulation method, the present application indirectly realizes the modulation of the optical rotation angle by red and blue detuning modulation of the detection light, avoids the introduction of the modulation magnetic field, suppresses the optical power noise and isolates the low frequency noise, and compared with the unmodulated mode, the present application enhances the amplitude of the optical rotation angle and improves the sensitivity of the magnetometer.

[0046] Reference Figure 1As shown, a kind of atomic magnetometer device based on detecting light frequency detuning amount modulation, including photoelectric measurement and control system 1 and atomic magnetometer meter head system 2, the photoelectric measurement and control system 1 includes red detuning light path system 1a and blue detuning light path system 1b, respectively for generating red detuning modulation light and blue detuning modulation light, the first laser of the red detuning light path 1a 101 generates red detuning laser, laser is successively through acoustooptic modulator 102, half wave plate 103, quarter wave plate 104 and diaphragm 105, only red detuning 0 order diffracted light is kept as red detuning modulation light and exits, the second laser of the blue detuning light path 1b 112 generates blue detuning laser, laser is successively through acoustooptic modulator 113, half wave plate 114, quarter wave plate 115 and diaphragm 116, only blue detuning 0 order diffracted light is kept as blue detuning modulation light and exits, the red detuning modulation light and blue detuning modulation light are combined after passing through reflecting mirror 117 and depolarization beam splitter prism 106 and enter the fiber coupler 107 and are coupled into the slow axis of detection light polarization maintaining optical fiber 108.The laser generated by the third laser 112 is incident into the meter head system 2 after passing through pumping light polarization maintaining optical fiber 119, the laser emitted by the pumping light polarization maintaining optical fiber 119 is successively through second linear polarizer 207 and quarter wave plate 208 in the meter head system 2 and then irradiates alkali metal cell 201, the laser emitted by the detection light polarization maintaining optical fiber 108 is successively through first linear polarizer 209, cell 202, half wave plate 204 and lateral displacement polarizing beam splitter prism 205 in the meter head system 2 and then is received by photodetector 206, the electrical signal output by the photodetector 206 is successively through differential amplifier 120 and lock-in amplifier 121 of the photoelectric measurement and control system 1 to generate atomic magnetometer output signal 122.

[0047] The first function signal generator 109 in the optical drive system 1 generates two square wave signals with the same frequency and a phase difference of 180°, which are input into the acoustooptic modulator driver 110 of the red detuning light path and the acoustooptic modulator driver 113 of the blue detuning light path respectively, so as to realize the control of the modulation frequency of the acoustooptic modulators in the two light paths.

[0048] The red detuning modulation light and the blue detuning modulation light are coupled into the slow axis of the detection light polarization maintaining optical fiber 108 by adjusting the polarization state, and the optical powers of the light emitted after the red detuning modulation light and the blue detuning modulation light pass through the optical fiber 108 are the same.

[0049] The lock-in amplifier 121 demodulates the first harmonic component from the differential signal as the detection result of the magnetometer to the magnetic field size.

[0050] The alkali metal gas chamber 201 is located in a non-magnetic electrically heated oven 202, which is located within a triaxial magnetic compensation coil 203 connected to a second function signal generator 123. The alkali metal atoms in the alkali metal gas chamber 201 are in a SERF state, and the alkali metal atom vapor density is 10. 13 ~10 14 pcs / cm 3 Magnitude.

[0051]

[0052] Where P x Let P0 be the initial polarizability projected along the x-direction by the polarizability of alkali metal atoms, and R be the polarizability. OP R is the pumping rate. rel γ is the transverse relaxation rate. e For electron gyromagnetic ratio, B x B y and B z Let be the components of the magnetic field vector to be measured along the x-axis, y-axis, and z-axis, respectively, and let B be the magnitude of the magnetic field to be measured.

[0053]

[0054] Where w mod v0 is the frequency of the modulated detection light, v0 is the resonant frequency of the alkali metal D1 line, and Δv = |v0|v0. mod -v0| represents the frequency detuning, ω m The modulation frequency of the acousto-optic modulator, i.e., v mod The frequency of change, where t is time and k is a positive integer.

[0055]

[0056] Where θ mod The modulated optical rotation angle is r, where l is the length of the gas cell and r is the angle of rotation. e Let n be the classical electron radius, n be the alkali metal atomic number density, c be the speed of light, and f be the velocity of light. D1 P represents the resonance intensity of the alkali metal D1 line. x The polarizability of alkali metal atoms is projected along the x-direction, Δv=|v mod -v0| represents the frequency detuning, v mod v0 is the modulated detection light frequency, v0 is the alkali metal D1 line resonant frequency, and Γ is the frequency of the modulated detection light. pr ω represents the pressure broadening value of the atomic gas cell. m The modulation frequency of the acousto-optic modulator, i.e., v mod The switching frequency.

[0057]

[0058] Where V out The first harmonic signal is demodulated from the differential amplified signal by the lock-in amplifier, i.e., the output signal of the atomic magnetometer, where e is the natural constant, l is the length of the gas chamber, and r is the first harmonic signal. e Let n be the classical electron radius, n be the alkali metal atomic number density, c be the speed of light, and f be the velocity of light. D1 The resonance intensity of the alkali metal D1 line is given by Δv = |v|. mod -v0| represents the frequency detuning, v mod v0 is the modulated detection light frequency, v0 is the alkali metal D1 line resonant frequency, and Γ is the frequency of the modulated detection light. pr P0 is the pressure broadening value of the atomic gas cell, and R is the initial polarizability. OP R is the pumping rate. rel γ is the transverse relaxation rate. e For electron gyromagnetic ratio, B x B y and B z These are the components of the measured magnetic field vector along the x-axis, y-axis, and z-axis, respectively. Let ω be the magnitude of the magnetic field to be measured. m The modulation frequency of the acousto-optic modulator, i.e., v mod The switching frequency.

[0059] like Figure 1 As shown, the specific implementation steps of the present invention are as follows:

[0060] (1) First, adjust the lasers emitted by the first laser 101 and the second laser 112 to be linearly polarized light with frequencies of v0-100GHz and v0+100GHz respectively, where v0 = 377106.92GHz. 87 The resonant frequency of the Rb atom D1 line is generated by the first function signal generator 109, with two frequencies both being ω. m A square wave signal of 1 kHz and a duty cycle of 50% is input to the acousto-optic modulator driver 110 and the acousto-optic modulator driver 111 respectively to control the acousto-optic modulator 102 and the acousto-optic modulator 113 to generate modulated light. The remaining light rays in the two modulated light beams except for the 0th order diffraction light are filtered by adjusting the aperture 105 and the aperture 116, and the two 0th order diffraction modulated light beams are combined and coupled to the slow axis of the detection light polarization-maintaining fiber 108.

[0061] (2) After step (1), adjust the optical power and wavelength of the laser output by the first laser 101 and the second laser 112 so that the optical power of the red detuned modulation light and the blue detuned modulation light emitted from the detection optical polarization-maintaining fiber 108 are both 3mW, and adjust the first function signal generator 109 so that the phase difference between the two square wave signals is 180°, so that the red detuned modulation light and the blue detuned modulation light do not pass through the gas chamber 201 as detection light at the same time, and the switching of the detection light between the two modulation lights is completed immediately without time interval.

[0062]

[0063] Where w mod v0 is the frequency of the modulated detection light, v0 is the resonant frequency of the alkali metal D1 line, and Δv = |v0|v0. mod -v0| represents the frequency detuning, ω m The modulation frequency of the acousto-optic modulator, i.e., v mod The switching frequency, where t is time and k is a positive integer.

[0064] (3) Adjust the laser frequency emitted by the third laser 118 to 377106.92GHz. The laser is sent into the meter system 2 through the pump optical polarization maintaining fiber 119 and is formed into circularly polarized light through the second linear polarizer 207 and quarter-wave plate 208 in the meter system. The circularly polarized light is used as pump light to irradiate the alkali metal gas chamber 201.

[0065] (4) The gas chamber 201 is heated by a non-magnetic electric heating oven 202 to make the atomic number density of alkali metal vapor reach 10. 13 pcs / cm 3 The magnitude is measured, and the triaxial magnetic compensation coil 203 is controlled by the second function signal generator 123 to perform magnetic compensation on the air chamber so that the air chamber 201 is in a near-zero magnetic environment.

[0066]

[0067] Where P x Let P0 be the initial polarizability projected along the x-direction by the polarizability of alkali metal atoms, and R be the polarizability. OP R is the pumping rate. rel γ is the transverse relaxation rate. e For electron gyromagnetic ratio, B x B y and B z Let be the components of the magnetic field vector to be measured along the x-axis, y-axis, and z-axis, respectively, and let B be the magnitude of the magnetic field to be measured.

[0068] (5) When the magnetic field to be measured is not zero, there is a difference in light intensity sensed by the two photodetectors 206 in the meter system 2. This difference will be output to the lock-in amplifier 121 through the differential amplifier 120, and then amplified at a frequency ω in the lock-in amplifier 121 using lock-in amplification technology. m =1kHz demodulated differential amplified signal first harmonic component is used as atomic magnetometer output signal 122.

[0069]

[0070] Where θ mod V is the modulated optical rotation angle.out is the first harmonic signal demodulated from the differential amplified signal by the lock-in amplifier, i.e. the output signal of the atomic magnetometer, P x is the x-projection of the alkali atom polarizability, e is the natural constant, l is the length of the cell, r e is the classical electron radius, n is the alkali atom number density, c is the light speed, f D1 is the 87 is the resonance strength of the Rb atom D1 line, Δv = |v mod -v0| is the frequency detuning, v mod is the frequency of the modulated probe light, v0 is the alkali D1 line resonance frequency, Γ pr is the atomic cell pressure broadening, P0 is the initial polarizability, R OP is the pumping rate, R rel is the transverse relaxation rate, γ e is the electron gyromagnetic ratio, B x , B y and B z are the components of the magnetic field vector to be measured along the x, y and z axes, respectively, is the magnitude of the magnetic field to be measured, ω m is the modulation frequency of the acousto-optic modulator, i.e. v mod is the switching frequency of the acousto-optic modulator.

[0071]

[0072] where θ is the optical rotation angle generated by the cell in the conventional non-modulated mode.

[0073] In summary, the present application provides an atomic magnetometer device and method based on the modulation of the frequency detuning of the probe light, which uses red-blue detuned linearly polarized light as the magnetometer probe light to modulate the frequency of the probe light, thereby modulating the optical rotation angle. The present application demodulates the first harmonic signal from the modulated electrical signal corresponding to the optical rotation angle as the output signal of the atomic magnetometer, thereby avoiding the problem of increased atomic spin-exchange relaxation and decreased sensitivity caused by the generation of a modulated magnetic field by a magnetic field coil to modulate the optical rotation angle signal in the conventional method. At the same time, the present application modulates the optical rotation angle by modulating the frequency of the probe light, thereby solving the problem of reduced optical rotation angle signal caused by the direct modulation of the optical rotation angle by an external modulator. The present application has the advantages of suppressing optical power noise and isolating low-frequency noise, and also enhances the optical rotation angle signal to some extent, thereby improving the sensitivity of the magnetometer.

[0074] The content not described in detail in the specification of the present application belongs to the prior art known to the person skilled in the art. It is indicated here that the above description helps the person 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. An atomic magnetometer device based on detecting the amount of frequency detuning modulation of light, characterized by, The photoelectric measurement and control system connected with the atomic magnetometer head system, the photoelectric measurement and control system includes red detuning light path system, blue detuning light path system and pumping light path system, the red detuning light path system and the blue detuning light path system jointly form red and blue detuning modulation light as the detection light input of the magnetometer head system, the red and blue detuning modulation light is the switching of red detuning modulation light and blue detuning modulation light into the combined beam light of interlaced connection; The first function signal generator in the photoelectric measurement and control system generates two square wave signals with the same frequency and a phase difference of 180°, which are input into the acoustic-optic modulator driver in the red detuning and blue detuning light path respectively to realize the control of the acoustic-optic modulator modulation frequency. The photoelectric measurement and control system connected with the atomic magnetometer head system, the photoelectric measurement and control system includes red detuning light path system, blue detuning light path system and pumping light path system, the red detuning light path system and the blue detuning light path system jointly form red and blue detuning modulation light as the detection light input of the magnetometer head system, the red and blue detuning modulation light is the switching of red detuning modulation light and blue detuning modulation light into the combined beam light of interlaced connection; where θ mod is the modulated optical rotation angle, l is the cell length, r e is the classical electron radius, n is the alkali atomic number density, c is the speed of light, f D1 is the resonance strength of the alkali D1 line, P x is the projection of the alkali atomic polarizability along the x direction, Δv is the frequency detuning, Γ pr is the atomic cell pressure broadening, ω m is the modulation frequency of the acousto-optic modulator, t is time, and k is a positive integer; V out is the first harmonic signal demodulated from the differential amplified signal by the phase-locked amplifier, e is the natural constant, P0 is the initial polarizability, R OP is the pumping rate, R rel is the transverse relaxation rate, γ e is the electron gyromagnetic ratio, B x , B y and B z are the components of the magnetic field vector to be measured along the x-axis, y-axis and z-axis respectively, B is the magnitude of the magnetic field to be measured, 2. The atomic magnetometer device based on modulation of the amount of frequency detuning of the detected light according to claim 1, characterized in that, The red detuning light path system includes a first laser, a first acoustic-optic modulator, a first half-wave plate, a first quarter-wave plate and a first light barrier connected in sequence, the first light barrier is connected to the first input side of the depolarization beam splitter prism, the first acoustic-optic modulator is connected to the first function signal generator through the first acoustic-optic modulator driver, the blue detuning light path system includes a second laser, a second acoustic-optic modulator, a second half-wave plate, a second quarter-wave plate and a second light barrier connected in sequence, the second light barrier is connected to the second input side of the depolarization beam splitter prism through a mirror, the second acoustic-optic modulator is connected to the first function signal generator through the second acoustic-optic modulator driver, the output side of the depolarization beam splitter prism is connected to the atomic magnetometer head system through a fiber coupler and a detection light polarization maintaining optical fiber in sequence.

3. The atomic magnetometer device based on modulation of the amount of frequency detuning of the detected light according to claim 1, characterized in that, The pumping light path system includes a third laser and a pumping light polarization maintaining optical fiber connected in sequence, and the pumping light polarization maintaining optical fiber is connected to the atomic magnetometer head system.

4. The atomic magnetometer device based on modulation of the amount of frequency detuning of the detected light according to claim 1, characterized in that, The atomic magnetometer head system includes an alkali metal cell, the alkali metal cell is located in a non-magnetic electric heating oven, the non-magnetic electric heating oven is located in a three-axis magnetic compensation coil, the three-axis magnetic compensation coil is connected to a second function signal generator, the detection light input side of the alkali metal cell is connected to the detection light polarization maintaining optical fiber through a first linear polarizer, the detection light output side of the alkali metal cell is sequentially connected to a third half-wave plate, a lateral displacement polarization beam splitter prism, a photodetector, a differential amplifier and a lock-in amplifier to form an atomic magnetometer output signal, the pumping light input side of the alkali metal cell is connected to the pumping light polarization maintaining optical fiber through a third quarter-wave plate and a second linear polarizer in sequence, and the lock-in amplifier demodulates a first harmonic component from the differential signal as a detection result of the magnetometer to the magnetic field size.

5. The apparatus of claim 1, wherein the frequency of the probe light is modulated by an amount proportional to the magnetic field. The red detuning modulation light and the blue detuning modulation light are coupled to the slow axis of the detection light optical fiber by adjusting the polarization state, and the optical power of the red detuning modulation light and the blue detuning modulation light emitted after passing through the optical fiber is the same.

6. The apparatus of claim 1, wherein, The photoelectric measurement and control system connected with the atomic magnetometer head system, the photoelectric measurement and control system includes red detuning light path system, blue detuning light path system and pumping light path system, the red detuning light path system and the blue detuning light path system jointly form red and blue detuning modulation light as the detection light input of the magnetometer head system, the red and blue detuning modulation light is the switching of red detuning modulation light and blue detuning modulation light into the combined beam light of interlaced connection; where v mod is the frequency of the modulated probe light, v0is the frequency of the alkali D1 line resonance, and Δv = |v mod -v0|.

7. A method for implementing an atomic magnetometer based on detecting the amount of frequency detuning modulation of light, characterized in that, Step 2, adjust the optical power and wavelength of the first laser and the second laser, so that the optical power of the red detuning modulation light and the blue detuning modulation light entering the head system through the detection light polarization maintaining optical fiber is the same; Step 1, the first laser and the second laser of the red detuned light path and the blue detuned light path are respectively adjusted to generate laser symmetrical about the alkali metal atom D1 line resonance frequency, two frequency ω m and phase difference of 180° square wave signals are generated by the first function signal generator, input into the acousto-optic modulator driver in the two light paths and control the corresponding acousto-optic modulator to generate modulated light, and the two modulated 0th order diffraction lights are coupled into the slow axis of the detection optical polarization maintaining fiber, and the modulated linearly polarized light emitted from the detection optical polarization maintaining fiber is shot into the cell as detection light through the first linear polarizer in the table head system; ​ Step 3, adjust the frequency of the laser emitted by the third laser to the frequency of the D1 line of the alkali metal atom, and the laser passes through the pump light polarization maintaining fiber to enter the head system and passes through the second polarizer and the quarter-wave plate in the head system to form circularly polarized light, and the circularly polarized light is used as the pump light to irradiate the cell; Step 4, heat the cell by a non-magnetic electric heating oven and control the magnetic compensation coils on the three axes to magnetically compensate the cell by a second function signal generator. Step 5, when the magnetic field to be measured is not 0, there is a difference in the light intensity sensed by the two photodetectors in the table head system, which will be output to the lock-in amplifier through the differential amplifier, and the first harmonic component will be demodulated out as the atomic magnetometer output signal through the lock-in amplification technology in the lock-in amplifier with the frequency ω m The first harmonic component is demodulated out as the atomic magnetometer output signal.

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