Atomic magnetometer device and method based on detection light frequency detuning amount modulation

Abstract

The invention discloses an atom magnetometer device and method based on detection light frequency detuning amount modulation. Red and blue detuning linear polarization modulation light is used as detection light to realize modulation of an optical rotation angle of an atom magnetometer. Under the condition that the optical power of the modulated light is kept unchanged, the frequency of the modulated light is subjected to red detuning and blue detuning conversion with the same detuning amount relative to the resonance frequency of the alkali metal atom D1 line, so that the rotation angle is quickly switched between positive deflection and negative deflection, the modulation of the rotation angle is realized, and the modulation efficiency is improved. And the modulated optical rotation angle signal is subjected to polarization differential detection and phase-locked amplification technologies to obtain a magnetometer output signal containing to-be-detected magnetic field information. Compared with a conventional atom magnetometer modulation method, the method has the advantages that the modulation of the optical rotation angle is indirectly realized by carrying out red and blue detuning modulation on the detection light, the introduction of a modulation magnetic field is avoided, the optical power noise is suppressed, the low-frequency noise is isolated, and compared with an unmodulated mode, the amplitude of the optical rotation angle is enhanced, and the sensitivity of the magnetometer is improved.

Description

Technical Field

[0001] The invention discloses an atomic magnetometer device and method based on detecting optical frequency detuning modulation, belonging to the technical field of atomic magnetometers. Background Art

[0002] As science enters the quantum era, the emergence and development of atomic magnetometers has provided a new direction for magnetic field detection and has shown great potential in the field of extremely weak magnetic field measurement. Atomic magnetometers use the characteristics and laws of atoms in light and magnetic fields to measure magnetic fields, and are playing an increasingly important role in biomedicine, industrial production, national defense construction, and cutting-edge 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 detection, bringing extremely weak magnetic detection into the era of sub-fT. The low-frequency sensitivity of SERF atomic magnetometers is largely limited by low-frequency noise. In order to improve the low-frequency sensitivity of SERF atomic magnetometers, in addition to improving signal strength, modulation methods are 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 passing through the gas chamber through an external modulator, but this modulation method has a small modulation angle for the optical rotation angle, which will cause the output optical rotation angle signal of the magnetometer to decrease, and the modulator is large in size and high in cost, which is not conducive to the realization of miniaturization and portability of atomic magnetometers. Summary of the invention

[0004] In view of the problem of limiting sensitivity improvement in a classical magnetometer device based on modulation means, the present invention proposes an atomic magnetometer device and method based on modulation of the detection light frequency detuning amount. Red and blue detuned linearly polarized modulated light is used for detecting the optical rotation angle. While keeping the optical power unchanged, the frequency of the modulated light is subjected to red detuning and blue detuning transformation with the same detuning amount relative to the D1 line resonance frequency of the alkali metal atom, so that the optical rotation angle is switched between positive deflection and negative deflection, thereby realizing modulation of the optical rotation angle signal. The modulated optical rotation angle signal is converted into an electrical signal proportional to the optical rotation angle by a photoelectric detector. A first harmonic signal is extracted from the electrical signal by a phase-locked amplifier as the output signal of the magnetometer, thereby realizing suppression of optical power noise and isolation of low-frequency noise. Meanwhile, compared with the non-modulation mode, the amplitude of the optical rotation angle signal is further improved, thereby improving the sensitivity of the magnetometer.

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

[0006] An atomic magnetometer device based on detection of optical frequency detuning modulation, characterized in that it comprises an optoelectronic measurement and control system connected to an atomic magnetometer head system, the optoelectronic measurement and control system comprises a red detuned optical path system, a blue detuned optical path system and a pumping optical path system, the red detuned optical path system and the blue detuned optical path system jointly form red and blue detuned modulated light as detection light input to the magnetometer head system, the red and blue detuned modulated light is a combined beam of light obtained by switching red detuned modulated light and blue detuned modulated light into an interlaced connection.

[0007] The red detuned optical path system comprises a first laser, a first acousto-optic modulator, a first half-wave plate, a first quarter-wave plate and a first aperture which are connected in sequence, the first aperture is connected to a first input side of a depolarizing beam splitter prism, the first acousto-optic modulator is connected to a first function signal generator via a first acousto-optic modulator driver, the blue detuned optical path system comprises a second laser, a second acousto-optic modulator, a second half-wave plate, a second quarter-wave plate and a second aperture which are connected in sequence, the second aperture is connected to a second input side of the depolarizing beam splitter prism via a reflector, the second acousto-optic modulator is connected to the first function signal generator via a second acousto-optic modulator driver, and the output side of the depolarizing beam splitter prism is connected to the atomic magnetometer head system via an optical fiber coupler and a detection light polarization-maintaining optical fiber in sequence.

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

[0009] The atomic magnetometer head system includes an alkali metal gas chamber, the alkali metal gas chamber 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 gas chamber is connected to the detection light polarization-maintaining optical fiber through a first linear polarizer, the detection light output side of the alkali metal gas chamber is sequentially connected to the atomic magnetometer output signal through a third half-wave plate, a lateral displacement polarization splitter prism, a photodetector, a differential amplifier and a phase-locked amplifier, and the pumping light input side of the alkali metal gas chamber is sequentially connected to the pumping light polarization-maintaining optical fiber through a third quarter-wave plate and a second linear polarizer.

[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°, which are respectively input into the AOM drivers in the red detuned and blue detuned optical paths to control the modulation frequency of the AOM.

[0011] The red detuned modulated light and the blue detuned modulated light are coupled to the slow axis of the detection light optical fiber by adjusting the polarization state, and the red detuned modulated light and the blue detuned modulated light have the same optical power after being emitted through the optical fiber.

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

[0013] include:

[0014]

[0015] where v mod is the modulated detection light frequency, v 0 is the alkali metal D1 line resonance frequency, Δv is the frequency detuning amount, Δv=|v mod -v 0 |,ω m is the modulation frequency of the AOM, that is, v mod The switching frequency is , t is the time, and k is a positive integer.

[0016] include:

[0017]

[0018] where θ mod is the optical rotation angle after modulation, l is the length of the air chamber, r e is the classical electron radius, n is the number density of alkali metal atoms, 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 polarizability of the alkali metal atom along the x direction, Δv is the frequency detuning, Γ pr is the pressure broadening value of the atomic gas chamber, ω m is the modulation frequency of the AOM, t is the time, and k is a positive integer.

[0019] include:

[0020]

[0021] Where V out is the first harmonic signal demodulated by the lock-in amplifier from the differential amplification signal, i.e., the output signal of the atomic magnetometer, e is a natural constant, l is the length of the gas chamber, and r e is the classical electron radius, n is the number density of alkali metal atoms, c is the speed of light, f D1 is the resonance intensity of the alkali metal D1 line, Δv is the frequency detuning, Γ pr is the pressure broadening value of the atomic gas chamber, P 0 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 zare 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, ω m is the modulation frequency of the AOM, that is, v mod The frequency of change.

[0022] A method for realizing an atomic magnetometer based on detecting optical frequency detuning modulation, characterized in that it comprises adopting the above-mentioned atomic magnetometer device based on detecting optical frequency detuning modulation, and the following steps:

[0023] Step 1, respectively adjust the emission frequencies of the first laser and the second laser of the red detuned optical path and the blue detuned optical path to be symmetrical about the resonance frequency of the alkali metal atom D1 line, and generate two paths of frequency ω through the first function signal generator. m The square wave signals with a phase difference of 180° are respectively input into the AOM drivers in the two optical paths and respectively control the corresponding AOMs to generate modulated light, and the two modulated 0th-order diffracted lights are coupled into the slow axis of the detection light polarization-maintaining optical fiber. The modulated linearly polarized light emitted from the detection light polarization-maintaining optical fiber passes through the first linear polarizer in the meter system and then is emitted into the air chamber as the detection light.

[0024] Step 2, adjusting the optical power and wavelength of the first laser and the second laser so that the optical power of the red detuned modulated light and the blue detuned modulated light entering the meter system through the detection light polarization-maintaining optical fiber is the same.

[0025] Step 3, adjusting the laser frequency emitted by the third laser to the resonance frequency of the alkali metal atom D1 line, the laser is incident on the meter head system through the pump light polarization-maintaining fiber and passes through the second linear polarizer and quarter wave plate in the meter head system to form circularly polarized light, and the circularly polarized light is used as pump light to irradiate the gas chamber;

[0026] Step 4, heating the air chamber by a non-magnetic electric heating oven and controlling the three-axis magnetic compensation coil by a second function signal generator to perform magnetic compensation on the air chamber;

[0027] Step 5: When the magnetic field to be measured is not zero, there is a difference in the light intensity felt by the two photodetectors in the meter system. The difference will be output to the phase-locked amplifier through the differential amplifier. In the phase-locked amplifier, the phase-locked amplifier uses the phase-locked amplification technology to generate a phase difference with a frequency of ω. m The first harmonic component is demodulated as the output signal of the atomic magnetometer.

[0028] The technical effects of the present invention are as follows: The present invention provides an atomic magnetometer device and method based on the modulation of the detuned amount of the detection light frequency, and uses the red and blue detuned linearly polarized modulated light as the magnetometer detection light to realize the modulation of the detection light frequency, thereby realizing the modulation of the optical rotation angle. The present invention extracts the first harmonic signal from the modulated electrical signal corresponding to the modulated optical rotation angle as the output signal of the atomic magnetometer, suppresses the optical power noise and isolates the low-frequency noise, and at the same time, compared with the conventional non-modulation mode, enhances the optical rotation angle signal to a certain extent, and improves the low-frequency sensitivity of the magnetometer.

[0029] The advantages of the present invention compared with the prior art are:

[0030] (1) Compared with conventional methods for modulating the optical rotation angle, such as using an external modulator such as a Faraday modulator or a photoelastic modulator to achieve optical rotation angle modulation, the present invention indirectly achieves the modulation of the optical rotation angle by an optical method, which can be directly integrated into miniaturization and has the technical advantages of being easy to miniaturize and array.

[0031] (2) Compared with conventional atomic magnetometers without modulation mode, the present invention enhances the optical rotation 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 rotation angle with a magnetic field, this method avoids the problem of increased atomic spin exchange relaxation and decreased overall sensitivity caused by the introduction of a modulated magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a schematic diagram of the structure of an atomic magnetometer device based on detecting optical frequency detuning modulation.

[0034] The reference numerals are as follows: 1-photoelectric measurement and control system; 2-atomic magnetometer head system; 1a-red detuned optical path system; 1b-blue detuned optical path system; 101-first laser; 102-first acousto-optic modulator; 103-first half-wave plate; 104-first quarter-wave plate; 105-first aperture; 106-depolarizing spectroscopic 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-first 2-half wave plate; 115-second quarter wave plate; 116-second aperture; 117-reflector; 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 gas chamber; 202-non-magnetic electric heating oven; 203-three-axis magnetic compensation coil; 204-third half wave plate; 205-lateral displacement polarization spectrometer; 206-photodetector; 207-second linear polarizer; 208-third quarter wave plate; 209-first linear polarizer. DETAILED DESCRIPTION

[0035] Below is the attached figure ( Figure 1 ) and Examples illustrate the present invention.

[0036] Figure 1 This is a schematic diagram of the structure of an atomic magnetometer device based on detecting the modulation of optical frequency detuning according to the present invention. Figure 1 As shown, an atomic magnetometer device based on modulation of the frequency detuning amount of detection light includes an optoelectronic measurement and control system 1 connected to an atomic magnetometer head system 2, wherein the optoelectronic measurement and control system 1 includes a red detuned optical path system 1a, a blue detuned optical path system 1b and a pumping optical path system, wherein the red detuned optical path system 1a and the blue detuned optical path system 1b jointly form red and blue detuned modulated light as detection light input to the magnetometer head system 2, wherein the red and blue detuned modulated light is a combined beam of red detuned modulated light and blue detuned modulated light switched into an interlaced connection.

[0037] The red detuned optical 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 aperture 105 which are connected in sequence, wherein the first aperture 105 is connected to a first input side of a depolarizing beam splitter prism 106, the first acousto-optic modulator 102 is connected to a first function signal generator 109 via a first acousto-optic modulator driver 110, and the blue detuned optical path system 1b comprises a second laser 112, a second acousto-optic modulator 113 and a first function signal generator 109 which are connected in sequence. The pumping optical path system includes a third laser 118 and a pumping light polarization-maintaining fiber 119 which are connected in sequence, and the pumping light polarization-maintaining fiber 119 is connected to the atomic magnetometer head system 2.

[0038] The atomic magnetometer head system 2 includes an alkali metal gas chamber 201, which is located in a non-magnetic electric heating oven 202, and 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 gas chamber 201 is connected to the detection light polarization-maintaining optical fiber 108 through a first linear polarizer 209. The detection light output side of the alkali metal gas chamber 201 passes through a third half-wave plate 204, a lateral displacement polarization beam splitter prism 205, a photodetector 206, a differential amplifier 120 and a phase-locked amplifier 121 in sequence to form an atomic magnetometer output signal 122. The pumping light input side of the alkali metal gas chamber 201 is connected to the pumping light polarization-maintaining optical 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 respectively input into the acousto-optic modulator drivers in the red detuned and blue detuned optical paths to control the modulation frequency of the acousto-optic modulator. The red detuned modulated light and the blue detuned modulated light are coupled to the slow axis of the detection optical fiber by adjusting the polarization state, and the red detuned modulated light and the blue detuned modulated light have the same optical power after passing through the optical fiber. The phase-locked amplifier 121 demodulates the first harmonic component from the differential signal as the detection result of the magnetic field magnitude by the magnetometer.

[0040] A method for realizing an atomic magnetometer based on detecting optical frequency detuning modulation, characterized in that it comprises adopting the above-mentioned atomic magnetometer device based on detecting optical frequency detuning modulation, and the following steps:

[0041] Step 1, respectively adjust the emission frequencies of the first laser and the second laser of the red detuned optical path and the blue detuned optical path to be symmetrical about the resonance frequency of the alkali metal atom D1 line, and generate two paths of frequency ω through the first function signal generator. m The square wave signals with a phase difference of 180° are respectively input into the AOM drivers in the two optical paths and respectively control the corresponding AOMs to generate modulated light, and the two modulated 0th-order diffraction lights are coupled to the slow axis of the detection light polarization-maintaining optical fiber. The modulated linearly polarized light emitted from the detection light polarization-maintaining optical fiber passes through the first linear polarizer in the header system and then is emitted into the air chamber as the detection light; Step 2, adjusting the optical power and wavelength of the first laser and the second laser so that the optical power of the red detuned modulated light and the blue detuned modulated light entering the header system through the detection light polarization-maintaining optical fiber is the same. Step 3, adjust the laser frequency emitted by the third laser to the resonance frequency of the alkali metal atom D1 line, the laser is incident on the meter head system through the pump light polarization-maintaining fiber and passes through the second linear polarizer and quarter wave plate in the meter head system to form circularly polarized light, and the circularly polarized light is used as pump light to irradiate the air chamber; Step 4, heat the air chamber through a non-magnetic electric heating oven and control the three-axis magnetic compensation coil through a second function signal generator to perform magnetic compensation on the air chamber; Step 5, when the magnetic field to be measured is not 0, there is a difference in the light intensity felt by the two photodetectors in the meter head system, and the difference will be output to the phase-locked amplifier through the differential amplifier, and the phase-locked amplifier is used in the phase-locked amplifier with a frequency ω m The first harmonic component is demodulated as the output signal of the atomic magnetometer.

[0042] Includes the following formulas:

[0043]

[0044] where v mod is the modulated detection light frequency, v 0 is the alkali metal D1 line resonance frequency, Δv is the frequency detuning amount, Δv=|v mod -v 0 |,ω m is the modulation frequency of the AOM, that is, v mod The switching frequency, t is the time, k is a positive integer, θ mod is the optical rotation angle after modulation, l is the length of the air chamber, r e is the classical electron radius, n is the number density of alkali metal atoms, 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 polarizability of the alkali metal atom along the x direction, Γpr is the pressure broadening value of the atomic gas chamber, V out is the first harmonic signal demodulated by the lock-in amplifier from the differential amplification signal, i.e., the output signal of the atomic magnetometer, e is a natural constant, P 0 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 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,

[0045] An atomic magnetometer device and method based on modulation of the detuning amount of the detection light frequency, using red and blue detuned linear polarization modulated light as the detection light to realize modulation of the optical rotation angle of the atomic magnetometer. Under the condition of keeping the optical power unchanged, the frequency of the modulated light is transformed into red detuning and blue detuning with the same detuning amount relative to the D1 line resonance frequency of the alkali metal atom, so that the optical rotation angle can be quickly switched between positive deflection and negative deflection, thereby realizing modulation of the optical rotation angle. The modulated optical rotation angle signal is used to obtain a magnetometer output signal containing the magnetic field information to be measured through polarization differential detection and phase-locked amplification technology. Compared with the conventional atomic magnetometer modulation method, the present invention indirectly realizes modulation of the optical rotation angle by performing red and blue detuning modulation on the detection light, avoids the introduction of the modulated magnetic field, suppresses the optical power noise and isolates the low-frequency noise, and compared with the unmodulated mode, the present invention enhances the amplitude of the optical rotation angle and improves the sensitivity of the magnetometer.

[0046] refer to Figure 1As shown, an atomic magnetometer device based on detecting optical frequency detuning modulation comprises an optoelectronic measurement and control system 1 and an atomic magnetometer head system 2. The optoelectronic measurement and control system 1 comprises a red detuned optical path system 1a and a blue detuned optical path system 1b, which are used to generate red detuned modulated light and blue detuned modulated light respectively. The first laser 101 of the red detuned optical path 1a generates red detuned laser light. The laser light sequentially passes through an acousto-optic modulator 102, a half wave plate 103, a quarter wave plate 104 and an aperture 105, and only the red detuned laser light is retained. The 0th order diffraction light is emitted as red detuned modulated light, and the second laser 112 of the blue detuned optical path 1b generates blue detuned laser. The laser passes through the acousto-optic modulator 113, the half wave plate 114, the quarter wave plate 115 and the aperture 116 in sequence, and only the blue detuned 0th order diffraction light is retained as the blue detuned modulated light to be emitted. The red detuned modulated light and the blue detuned modulated light are combined by the reflector 117 and the depolarizing beam splitter prism 106 and enter the optical fiber coupler 107 and are coupled into the slow axis of the detection light polarization-maintaining optical fiber 108. The laser generated by the third laser 112 is incident on the meter head system 2 through the pumping light polarization-maintaining fiber 119. The laser emitted by the pumping light polarization-maintaining fiber 119 passes through the second linear polarizer 207 and the quarter-wave plate 208 in the meter head system 2 in turn and then irradiates the alkali metal gas chamber 201. The laser emitted by the detection light polarization-maintaining fiber 108 passes through the first linear polarizer 209, the gas chamber 202, the half-wave plate 204 and the lateral displacement polarization splitter prism 205 in the meter head system 2 in turn and then is received by the photodetector 206. The electrical signal output by the photodetector 206 passes through the differential amplifier 120 and the phase-locked amplifier 121 of the photoelectric measurement and control system 1 in turn to generate the 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 respectively input into the AOM driver 110 of the red detuned optical path and the AOM driver 113 of the blue detuned optical path, thereby realizing the control of the modulation frequency of the AOMs in the two optical paths.

[0048] The red detuned modulated light and the blue detuned modulated light are coupled into the slow axis of the detection light polarization-maintaining optical fiber 108 by adjusting the polarization state. The red detuned modulated light and the blue detuned modulated light have the same optical power after exiting the optical fiber 108 .

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

[0050] The alkali metal gas chamber 201 is located in a non-magnetic electric heating oven 202, and the oven 202 is located in a three-axis magnetic compensation coil 203, and the three-axis magnetic compensation coil 203 is connected to the 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 Pieces / cm 3 Magnitude.

[0051]

[0052] Where P x is the projection of the polarizability of the alkali metal atom along the x direction, P 0 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,

[0053]

[0054] where w mod is the modulated detection light frequency, v 0 is the resonance frequency of the alkali metal D1 line, Δv=|v mod -v 0 |, is the frequency detuning amount, ω m is the modulation frequency of the AOM, that is, v mod The frequency of change of , t is time, and k is a positive integer.

[0055]

[0056] where θ mod is the optical rotation angle after modulation, l is the length of the air chamber, r e is the classical electron radius, n is the number density of alkali metal atoms, 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 polarizability of the alkali metal atom along the x direction, Δv = |v mod -v 0 |, is the frequency detuning amount, v mod is the modulated detection light frequency, v 0 is the alkali metal D1 line resonance frequency, Γ pr is the pressure broadening value of the atomic gas chamber, ω m is the modulation frequency of the AOM, that is, v modThe switching frequency.

[0057]

[0058] Where V out is the first harmonic signal demodulated by the lock-in amplifier from the differential amplification signal, i.e., the output signal of the atomic magnetometer, e is a natural constant, l is the length of the gas chamber, and r e is the classical electron radius, n is the number density of alkali metal atoms, c is the speed of light, f D1 is the resonance intensity of the alkali metal D1 line, Δv = |v mod -v 0 |, is the frequency detuning amount, v mod is the modulated detection light frequency, v 0 is the alkali metal D1 line resonance frequency, Γ pr is the pressure broadening value of the atomic gas chamber, P 0 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, is the magnitude of the magnetic field to be measured, ω m is the modulation frequency of the AOM, that is, 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 have frequencies v 0 -100GHz and v 0 +100GHz linearly polarized light, where v 0 =377106.92GHz 87 The resonance frequency of the D1 line of the Rb atom is generated by the first function signal generator 109, and both frequencies are ω m =1kHz and a square wave signal with a duty cycle of 50% are respectively input into the AOM driver 110 and the AOM driver 111 to control the AOM 102 and the AOM 113 to generate modulated light, and the remaining light in the two modulated lights except the 0th order diffracted light is filtered by adjusting the aperture 105 and the aperture 116, and the two 0th order diffracted modulated lights are combined and coupled to the slow axis of the detection light polarization-maintaining fiber 108;

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

[0062]

[0063] where w mod is the modulated detection light frequency, v 0 is the resonance frequency of the alkali metal D1 line, Δv=|v mod -v 0 |, is the frequency detuning amount, ω m is the modulation frequency of the AOM, that is, v mod The switching frequency is , t is the time, and k is a positive integer.

[0064] (3) The frequency of the laser emitted by the third laser 118 is adjusted to 377106.92 GHz. The laser is incident on the meter head system 2 through the pump light polarization-maintaining fiber 119 and forms circularly polarized light through the second linear polarizer 207 and the quarter-wave plate 208 in the meter head 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 the non-magnetic electric heating oven 202, so that the atomic density of the alkali metal vapor reaches 10 13 Pieces / cm 3 magnitude, and controlling the three-axis magnetic compensation coil 203 to perform magnetic compensation on the air chamber through the second function signal generator 123 so that the air chamber 201 is in a near-zero magnetic environment;

[0066]

[0067] Where P x is the projection of the polarizability of the alkali metal atom along the x direction, P 0 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,

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

[0069]

[0070] where θ mod is the optical rotation angle after modulation, V out is the first harmonic signal demodulated by the lock-in amplifier from the differential amplified signal, i.e., the output signal of the atomic magnetometer, P x is the projection of the polarizability of the alkali metal atom along the x direction, e is a natural constant, l is the length of the gas cell, r e is the classical electron radius, n is the number density of alkali metal atoms, c is the speed of light, f D1 for 87 The resonance intensity of the D1 line of the Rb atom, Δv = |v mod -v 0 | is the frequency detuning amount, v mod is the modulated detection light frequency, v 0 is the alkali metal D1 line resonance frequency, Γ pr is the pressure broadening value of the atomic gas chamber, P 0 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, is the magnitude of the magnetic field to be measured, ω m is the modulation frequency of the AOM, that is, v mod The switching frequency.

[0071]

[0072] Where θ is the optical rotation angle generated by the gas cell in the conventional non-modulation mode.

[0073] In summary, the present invention provides an atomic magnetometer device and method based on modulation of the detuned amount of the detection light frequency, and uses red and blue detuned linear polarized light as the magnetometer detection light to realize modulation of the detection light frequency, thereby realizing modulation of the optical rotation angle. The present invention demodulates the first harmonic signal from the modulated electrical signal corresponding to the modulated optical rotation angle as the output signal of the atomic magnetometer, avoiding the problem of increased atomic spin exchange relaxation and decreased sensitivity caused by conventional modulation of the optical rotation angle signal by generating a modulated magnetic field through a magnetic field coil. At the same time, the present invention realizes modulation of the optical rotation angle by modulating the frequency of the detection light, solving the problem of reduced optical rotation angle signal caused by direct modulation of the optical rotation angle by an external modulator. The advantages of the present invention are that it suppresses optical power noise and isolates low-frequency noise, and at the same time, it also enhances the optical rotation angle signal to a certain extent, thereby improving the sensitivity of the magnetometer.

[0074] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. An atomic magnetometer device based on detecting optical frequency detuning modulation, characterized in that: The invention comprises a photoelectric measurement and control system connected to an atomic magnetometer head system, wherein the photoelectric measurement and control system comprises a red detuned optical path system, a blue detuned optical path system and a pumping optical path system, wherein the red detuned optical path system and the blue detuned optical path system jointly form red and blue detuned modulated light as detection light input to the magnetometer head system, and the red and blue detuned modulated light is a combined light beam obtained by switching the red detuned modulated light and the blue detuned modulated light into an interlaced connection.

2. The atomic magnetometer device based on detecting optical frequency detuning modulation according to claim 1, characterized in that: The red detuned optical path system comprises a first laser, a first acousto-optic modulator, a first half-wave plate, a first quarter-wave plate and a first aperture which are connected in sequence, the first aperture is connected to a first input side of a depolarizing beam splitter prism, the first acousto-optic modulator is connected to a first function signal generator via a first acousto-optic modulator driver, the blue detuned optical path system comprises a second laser, a second acousto-optic modulator, a second half-wave plate, a second quarter-wave plate and a second aperture which are connected in sequence, the second aperture is connected to a second input side of the depolarizing beam splitter prism via a reflector, the second acousto-optic modulator is connected to the first function signal generator via a second acousto-optic modulator driver, and the output side of the depolarizing beam splitter prism is connected to the atomic magnetometer head system via an optical fiber coupler and a detection light polarization-maintaining optical fiber in sequence.

3. The atomic magnetometer device based on detecting light frequency detuning modulation according to claim 1, characterized in that: The pumping optical path system comprises a third laser and a pumping light polarization-maintaining optical fiber which are 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 detecting light frequency detuning modulation according to claim 1, characterized in that: The atomic magnetometer head system includes an alkali metal gas chamber, the alkali metal gas chamber 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 gas chamber is connected to the detection light polarization-maintaining optical fiber through a first linear polarizer, the detection light output side of the alkali metal gas chamber passes through a third half-wave plate, a lateral displacement polarization splitter prism, a photodetector, a differential amplifier and a phase-locked amplifier in sequence to form an atomic magnetometer output signal, the pumping light input side of the alkali metal gas chamber 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 phase-locked amplifier demodulates a first harmonic component from the differential signal as the detection result of the magnetometer on the magnetic field size.

5. The atomic magnetometer device based on detecting light frequency detuning modulation according to claim 1, characterized in that: 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 respectively input into the AOM drivers in the red detuned and blue detuned optical paths to control the modulation frequency of the AOM.

6. The atomic magnetometer device based on detecting light frequency detuning modulation according to claim 1, characterized in that: The red detuned modulated light and the blue detuned modulated light are coupled to the slow axis of the detection light optical fiber by adjusting the polarization state, and the red detuned modulated light and the blue detuned modulated light have the same optical power after being emitted through the optical fiber.

7. The atomic magnetometer device based on detecting optical frequency detuning modulation according to claim 1, characterized in that: include: where ν mod is the modulated detection light frequency, v0 is the alkali metal D1 line resonance frequency, Δv is the frequency detuning amount, Δν=|ν mod -ν0|,ω m is the modulation frequency of the AOM, that is, ν mod The switching frequency is , t is the time, and k is a positive integer.

8. The atomic magnetometer device based on detecting optical frequency detuning modulation according to claim 1, characterized in that: include: where θ mod is the optical rotation angle after modulation, l is the length of the air cell, r e is the classical electron radius, n is the number density of alkali metal atoms, 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 polarizability of the alkali metal atom along the x direction, Δv is the frequency detuning, Γ pr is the pressure broadening value of the atomic gas chamber, ω m is the modulation frequency of the AOM, t is the time, and k is a positive integer.

9. The atomic magnetometer device based on detecting optical frequency detuning modulation according to claim 1, characterized in that: include: Where V out is the first harmonic signal demodulated by the lock-in amplifier from the differential amplification signal, i.e., the output signal of the atomic magnetometer, e is a natural constant, l is the length of the gas chamber, and r e is the classical electron radius, n is the number density of alkali metal atoms, c is the speed of light, f D1 is the resonance intensity of the alkali metal D1 line, Δν is the frequency detuning, ν mod is the modulated detection light frequency, v0 is the alkali metal D1 line resonance frequency, Γ pr is the pressure broadening value of the atomic gas chamber, 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, ω m is the modulation frequency of the AOM, that is, v mod The switching frequency.

10. A method for realizing an atomic magnetometer based on detecting optical frequency detuning modulation, characterized in that: The invention comprises an atomic magnetometer device based on detecting the modulation of optical frequency detuning amount according to any one of claims 1 to 9, and the following steps: Step 1, respectively adjust the emission frequencies of the first laser and the second laser of the red detuned optical path and the blue detuned optical path to be symmetrical about the resonance frequency of the alkali metal atom D1 line, and generate two paths of frequency ω through the first function signal generator. m The square wave signals with a phase difference of 180° are respectively input into the AOM drivers in the two optical paths and respectively control the corresponding AOMs to generate modulated light, and the two modulated 0th-order diffracted lights are coupled into the slow axis of the detection light polarization-maintaining optical fiber. The modulated linearly polarized light emitted from the detection light polarization-maintaining optical fiber passes through the first linear polarizer in the meter system and then is emitted into the air chamber as the detection light. Step 2, adjusting the optical power and wavelength of the first laser and the second laser so that the optical power of the red detuned modulated light and the blue detuned modulated light entering the meter system through the detection light polarization-maintaining optical fiber is the same. Step 3, adjusting the laser frequency emitted by the third laser to the resonance frequency of the alkali metal atom D1 line, the laser is incident on the meter head system through the pump light polarization-maintaining fiber and passes through the second linear polarizer and quarter wave plate in the meter head system to form circularly polarized light, and the circularly polarized light is used as pump light to irradiate the gas chamber; Step 4, heating the air chamber by a non-magnetic electric heating oven and controlling the three-axis magnetic compensation coil by a second function signal generator to perform magnetic compensation on the air chamber; Step 5: When the magnetic field to be measured is not zero, there is a difference in the light intensity felt by the two photodetectors in the meter system. The difference will be output to the phase-locked amplifier through the differential amplifier. In the phase-locked amplifier, the phase-locked amplifier uses the phase-locked amplification technology to generate a phase difference with a frequency of ω. m The first harmonic component is demodulated as the output signal of the atomic magnetometer.

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