A modulation method and device for a free-precession atomic magnetometer based on optical-magnetic double resonance pulses

Abstract

The present invention discloses a modulation method and device for a free precession atomic magnetometer based on optical-magnetic double resonance pulses, relating to the field of precision magnetic field measurement technology. First, pump light is passed through an optical intensity modulator to generate a light pulse with a pulse frequency approximately equal to the Larmor precession frequency and a duty cycle of 50% to produce macroscopic polarization. The pump light is then turned off, and a radio frequency pulse corresponding to the optical pulse frequency is instantaneously applied to manipulate the spin polarization vector to a plane perpendicular to the magnetic field direction. After the radio frequency pulse is removed, a free precession signal is generated. By processing the free precession signal to extract the Larmor precession frequency, magnetic field information can be obtained. This invention enhances the free precession signal and reduces the magnetometer dead zone to a single axis in the detection light direction, providing a new solution for the application of free precession atomic magnetometers.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic field precision measurement, and in particular to a modulation method and device for a free precession atomic magnetometer based on optical-magnetic double resonance pulses. Background Art

[0002] With the advancement of laser and micro-electromechanical systems (MEMS) technology, optically pumped magnetometers (OPMs) have shown great potential for chip integration. Their high sensitivity, wide bandwidth, and high dynamic range have made them suitable for applications in geomagnetic navigation, magnetic anomaly detection, and mineral exploration, attracting extensive research and attention both domestically and internationally. The free-induction-decay (FID) atomic magnetometer, also known as the free precession atomic magnetometer, a new operating mode of optically pumped atomic magnetometers, offers high accuracy, simple circuitry, and strong robustness, making it a mainstream choice for scientific research and industrialization.

[0003] However, the free precession atomic magnetometer extracts magnetic field information by directly processing the free precession signal in the time domain. Therefore, the strength of the free precession signal directly determines the signal-to-noise ratio of the magnetometer, which in turn affects the sensitivity of the magnetometer.

[0004] Therefore, it is necessary to provide a modulation method and device for a free precession atomic magnetometer based on optical-magnetic double resonance pulses to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a free precession atomic magnetometer modulation method and device based on optical-magnetic double resonance pulses. Based on optical-magnetic modulation technology, a free precession signal is generated by applying optical-magnetic double resonance pulses for modulation. The intensity of the free precession signal can be effectively enhanced, and the dead zone of the magnetometer is suppressed, thereby improving the working performance of the magnetometer and facilitating the precise measurement of the magnetic field.

[0006] To achieve the above object, the present invention provides a modulation method for a free precession atomic magnetometer based on optical-magnetic double resonance pulses, comprising the following steps:

[0007] S1: Turn on the pump laser and the detection laser, adjust the emission frequencies of the pump laser and the detection laser, and make the pump light and the detection light pass through the alkali metal atom gas chamber respectively;

[0008] S2: Control the signal generator to input a square wave pulse with a duty cycle of 50% and a pulse frequency approximately equal to the Larmor precession frequency corresponding to the magnetic field to the optical intensity modulator to perform optical pumping operation. After a period of time, the modulated optical signal is removed.

[0009] S3: At the moment when the input signal from the signal generator to the light intensity modulator is removed, a radio frequency pulse with the same frequency as the square wave pulse frequency of the light intensity modulator is applied to control the spin polarization vector to a plane perpendicular to the magnetic field direction, and then the radio frequency pulse is removed;

[0010] S4: After removing the input signal from the signal generator to the radio frequency coil, the detection light outputs a free precession signal, and the generated free precession signal is collected by a data acquisition device and processed to obtain magnetic field information.

[0011] Preferably, the adjustment of the pump laser and the detection laser in step S1 specifically includes the following steps:

[0012] S11: Adjust the frequency of the pumping light emitted by the pumping laser to the center of the alkali metal atomic spectrum line D1;

[0013] S12: adjusting the polarization device to generate circularly polarized light, and the circularly polarized light passes through the alkali metal atom gas cell;

[0014] S13: adjusting the frequency detuning of the detection light emitted by the detection laser to maximize the optical rotation angle of the detection light;

[0015] S14: Produce linearly polarized light through a polarizer, and allow the linearly polarized light to pass through the alkali metal atom gas cell.

[0016] Preferably, in step S2, the specific steps of the optical pumping operation are as follows:

[0017] S21: Input a square wave pulse with a frequency of approximately the Larmor precession frequency and a duty cycle of 50% to the light intensity modulator through a signal generator, and remove the input signal after a period of time;

[0018] S22: The duty cycle in step S21 is controlled to remain unchanged, and the frequency of the square wave pulse is changed so that the detection light output signal is maximized when the input signal of the optical intensity modulator is removed, thereby completing the optical pumping operation.

[0019] Preferably, in step S3, the specific steps of controlling the spin polarization vector to be perpendicular to the magnetic field direction are as follows:

[0020] S31: Input a radio frequency pulse signal with the same frequency as the square wave frequency of the light intensity modulator to the radio frequency coil through the signal generator in a direction perpendicular to the plane of the pumping light and the detection light, and remove it after it lasts for less than 0.05ms;

[0021] S32: Control the RF field action time and frequency to remain unchanged, adjust the RF input signal amplitude so that the signal amplitude is maximized when the RF pulse is removed, and the spin polarization vector will be manipulated to a plane perpendicular to the magnetic field direction.

[0022] Preferably, in step S4, the free precession signal acquisition and processing specifically includes the following steps:

[0023] S41: After the RF pulse is removed, the spin polarization vector undergoes a free precession process, and the detection light outputs a free precession signal;

[0024] S42: Collecting a free precession signal output by the detection light through a data acquisition device;

[0025] S43: Process the free precession signal, extract the Larmor precession frequency contained in the free precession signal, and obtain magnetic field information.

[0026] A free precession atomic magnetometer device based on optical-magnetic double resonance pulses, including a device for realizing a pumping optical path and a detection optical path of the free precession atomic magnetometer, and steps for realizing a modulation method of the free precession atomic magnetometer based on optical-magnetic double resonance pulses;

[0027] The pumping optical path of the free precession atomic magnetometer passes through the pumping laser, the light intensity modulator, the first half-wave plate, the first polarizer, the reflector, the quarter-wave plate and then reaches the alkali metal gas chamber;

[0028] The detection optical path of the free precession atomic magnetometer passes through the detection laser, the second polarizer, the alkali metal gas cell, the second half-wave plate and then reaches the spectroscopic system;

[0029] A polarization balance differential detection circuit is provided on one side of the spectroscopic system. A first photodetector and a second photodetector are provided in parallel on the polarization balance differential detection circuit. The reflection side of the spectroscopic system is connected to the first photodetector, and the transmission side of the spectroscopic system is connected to the second photodetector. The output end of the polarization balance differential detection circuit is connected to the input end of the transimpedance amplifier, the output end of the transimpedance amplifier is connected to the input end of the data acquisition device, and the output end of the signal generator is respectively connected to the input end of the light intensity modulator and the input end of the radio frequency coil perpendicular to the direction of the pumping light and the detection light plane.

[0030] Preferably, a first polarizer is arranged between the first half-wave plate and the reflector, a quarter-wave plate is arranged between the first polarizer and the alkali metal gas chamber, the second polarizer and the second half-wave plate are respectively arranged on both sides of the alkali metal gas chamber, a non-magnetic electric heating system is arranged on the outside of the alkali metal gas chamber, and a spectroscopic system is arranged between the second half-wave plate and the polarization balance differential detection circuit. All of the above components are arranged in an area surrounded by a radio frequency coil, and the radio frequency coil is arranged in a magnetometer support shell.

[0031] Therefore, the present invention adopts the above-mentioned free precession atomic magnetometer modulation method based on optical-magnetic double resonance pulse, which has the following beneficial effects:

[0032] (1) The present invention is simple to operate and achieves the enhancement of the free precession signal without increasing the system volume, cost, and complexity, thereby improving the signal-to-noise ratio of the free precession magnetometer and contributing to the improvement of the magnetometer sensitivity.

[0033] (2) The present invention reduces the dead zone of the free precession magnetometer to a single-axis dead zone in the detection light direction without changing the magnetometer structure or sacrificing the magnetometer sensitivity, further improving the application flexibility of the free precession atomic magnetometer.

[0034] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of a modulation method of a free precession atomic magnetometer based on optical-magnetic double resonance pulses according to the present invention;

[0036] Figure 2 This is a schematic structural diagram of a free precession atomic magnetometer device based on optical-magnetic double resonance pulses according to the present invention;

[0037] Figure 3 This is a timing diagram of a signal waveform applied by a signal generator involved in a modulation method for a free precession atomic magnetometer based on optical-magnetic double resonance pulses according to an embodiment of the present invention;

[0038] Figure annotation

[0039] 1. Pumping laser; 2. Detection laser; 3. Light intensity modulator; 4. First half-wave plate; 5. First polarizer; 6. Reflector; 7. Quarter-wave plate; 8. Second polarizer; 9. Second half-wave plate; 10. Alkali metal gas chamber; 11. Non-magnetic electric heating system; 12. Spectral system; 13. Polarization balance differential detection circuit; 14. Transimpedance amplifier; 15. Data acquisition equipment; 16. Signal generator; 17. Radio frequency coil; 18. Magnetometer support housing. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0041] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0042] The words “include” or “comprising” and similar words used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms “inside”, “outside”, “upper”, “lower”, etc. is based on the orientation or position relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly stipulated and limited, the terms such as “attachment” should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral whole; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0043] Example

[0044] like Figure 2 As shown in the figure, xyz are the three axes of the Cartesian coordinate system (x-axis, y-axis, and z-axis) established with the direction of the laboratory pump light as the z-axis; x'y'z' are the three axes of the Cartesian coordinate system (x'-axis, y'-axis, and z'-axis) established with the direction of the magnetic field to be measured as the z'-axis; B0 is the magnetic field to be measured; θ is the polar angle of the magnetic field to be measured in the z-axis direction; φ is the azimuth angle of the magnetic field to be measured in the xy plane.

[0045] The present invention provides a modulation method for a free precession atomic magnetometer based on optical-magnetic double resonance pulses, comprising the following steps:

[0046] S1: Turn on the pump laser and the detection laser, adjust the emission frequencies of the pump laser and the detection laser, and make the pump light and the detection light pass through the alkali metal atom gas chamber respectively; the adjustment of the pump laser and the detection laser in step S1 specifically includes the following steps:

[0047] S11: Adjust the frequency of the pumping light emitted by the pumping laser to the center of the alkali metal atomic spectrum line D1;

[0048] S12: adjusting the polarization device to generate circularly polarized light, and the circularly polarized light passes through the alkali metal atom gas cell;

[0049] S13: adjusting the frequency detuning of the detection light emitted by the detection laser to maximize the optical rotation angle of the detection light;

[0050] S14: Produce linearly polarized light through a polarizer, and allow the linearly polarized light to pass through the alkali metal atom gas cell.

[0051] S2: Control the signal generator to input a square wave pulse with a duty cycle of 50% and a pulse frequency approximately equal to the Larmor precession frequency corresponding to the magnetic field to the optical intensity modulator to perform optical pumping operation. After a period of time, the modulated optical signal is removed. Figure 3 As shown, the signal waveform timing is divided into three stages. In the pumping stage, the signal generator inputs a square wave pulse with a frequency of Larmor precession frequency and a duty cycle of 50% to the optical intensity modulator; in the RF stage, the signal generator applies an RF pulse with a frequency of Larmor precession frequency to the y-axis of the RF coil; and in the detection stage, no signal is input.

[0052] In step S2, the specific steps of the optical pumping operation are as follows:

[0053] S21: Input a square wave pulse with a frequency of approximately the Larmor precession frequency and a duty cycle of 50% to the light intensity modulator through a signal generator, and remove the input signal after a period of time;

[0054] S22: The duty cycle in step S21 is controlled to remain unchanged, and the frequency of the square wave pulse is changed so that the detection light output signal is maximized when the input signal of the optical intensity modulator is removed, thereby completing the optical pumping operation.

[0055] S3: At the moment when the input signal from the signal generator to the optical intensity modulator is removed, a radio frequency pulse having the same frequency as the square wave pulse frequency of the optical intensity modulator is applied to manipulate the spin polarization vector to a plane perpendicular to the magnetic field direction, and then the radio frequency pulse is removed. In step S3, the specific steps of manipulating the spin polarization vector to be perpendicular to the magnetic field direction are as follows:

[0056] S31: Input a radio frequency pulse signal with the same frequency as the square wave frequency of the light intensity modulator to the radio frequency coil through the signal generator in a direction perpendicular to the plane of the pumping light and the detection light, and remove it after it lasts for less than 0.05ms;

[0057] S32: Control the RF field action time and frequency to remain unchanged, adjust the RF input signal amplitude so that the signal amplitude is maximized when the RF pulse is removed, and the spin polarization vector will be manipulated to a plane perpendicular to the magnetic field direction.

[0058] S4: After removing the signal generator's input signal to the RF coil, the detector outputs a free precession signal. The generated free precession signal is collected and processed by a data acquisition device to obtain magnetic field information. In step S4, the free precession signal collection and processing specifically includes the following steps:

[0059] S41: After the RF pulse is removed, the spin polarization vector undergoes a free precession process, and the detection light outputs a free precession signal;

[0060] S42: Collecting a free precession signal output by the detection light through a data acquisition device;

[0061] S43: Process the free precession signal, extract the Larmor precession frequency contained in the free precession signal, and obtain magnetic field information.

[0062] A laboratory coordinate system was established using the Cartesian coordinate system of the free precession atomic magnetometer, with the x-direction being the detection direction, the z-direction being the pumping direction, and the y-direction being the RF field direction. A pulsed RF field was applied. The main magnetic field direction made an angle θ with the z-axis, and its projection on the xy plane made an angle φ with the y-axis.

[0063] In this state, the relationship between the spin polarization vector and the pumping time t1 in step S2 can be described by the following formula:

[0064]

[0065] in, is the pumping rate, R1 is the longitudinal relaxation rate, R2 is the transverse relaxation rate, S x2 、S y2 、S z2 They are respectively the changes of the spin polarization vector in the rotating coordinate system established with the direction of the main magnetic field to be measured as the z" axis.

[0066] In step S3, the pumping is turned off after the pumping is completed, and a radio frequency pulse 2B1cos(ωt2) is applied instantaneously. The time is very short and the relaxation can be ignored. A rotating coordinate system is established with the radio frequency pulse as the y" axis. The change of the spin polarization vector with the radio frequency pulse application time t2 can be described by the following formula:

[0067]

[0068] Where γ is the gyromagnetic ratio, B1 is the RF pulse amplitude, ω is the Larmor precession frequency, and δ is the angle between the spin polarization vector in the x”y” plane and the x” axis of the rotating coordinate system at the start of the RF pulse application.

[0069]

[0070] By controlling the amplitude and time of the RF pulse, the spin polarization vector can be manipulated to the x"y" plane, making the polarization in the z" direction 0. At this time, the spin polarization vector in the x"y" plane is

[0071]

[0072] In step S4, the radio frequency pulse is removed and the spin polarization vector performs free precession. At this time, in the magnetic field coordinate system established with the magnetic field direction as z', the following is obtained:

[0073]

[0074] Among them, t3 is the free precession time, B0 is the amplitude of the main magnetic field to be measured, is the angle between the spin polarization vector and the x' axis of the magnetic field coordinate system, is the transverse relaxation rate after pumping is turned off, S x1 、S y1 、S z1 They are respectively the changes of the spin polarization vector in the magnetic field coordinate system established with the direction of the main magnetic field to be measured as the z' axis.

[0075] Convert the magnetic field coordinate system into the laboratory coordinate system and we get:

[0076]

[0077] Among them, S x 、S y 、S z They are respectively the changes of the spin polarization vector in the laboratory coordinate system established with the direction of the laboratory pump light as the z-axis.

[0078] During free precession, after the detection light passes through the polarization balanced differential detection circuit and the transimpedance amplifier, the signal collected by the data acquisition device is

[0079] V signal =AS x

[0080] Among them, V signal is the free precession voltage signal collected by the data acquisition device, and A is the photoelectric amplification factor of the polarization balance differential detection circuit and the transimpedance amplifier.

[0081] like Figure 1 As shown, a free precession atomic magnetometer device based on optical-magnetic double resonance pulses includes a device for realizing a pumping optical path and a detection optical path of the free precession atomic magnetometer, and steps for realizing a modulation method of the free precession atomic magnetometer based on optical-magnetic double resonance pulses;

[0082] The pumping optical path of the free precession atomic magnetometer passes through the pumping laser, the light intensity modulator, the first half-wave plate, the first polarizer, the reflector, the quarter-wave plate and then reaches the alkali metal gas chamber;

[0083] The detection optical path of the free precession atomic magnetometer passes through the detection laser, the second polarizer, the alkali metal gas cell, the second half-wave plate and then reaches the spectroscopic system;

[0084] A polarization balance differential detection circuit is provided on one side of the spectroscopic system. A first photodetector and a second photodetector are provided in parallel on the polarization balance differential detection circuit. The reflection side of the spectroscopic system is connected to the first photodetector, and the transmission side of the spectroscopic system is connected to the second photodetector. The output end of the polarization balance differential detection circuit is connected to the input end of the transimpedance amplifier, the output end of the transimpedance amplifier is connected to the input end of the data acquisition device, and the output end of the signal generator is respectively connected to the input end of the light intensity modulator and the input end of the radio frequency coil perpendicular to the direction of the pumping light and the detection light plane.

[0085] A first polarizer is arranged between the first half-wave plate and the reflector, a quarter-wave plate is arranged between the first polarizer and the alkali metal gas chamber, the second polarizer and the second half-wave plate are respectively arranged on both sides of the alkali metal gas chamber, a non-magnetic electric heating system is arranged on the outside of the alkali metal gas chamber, and a spectroscopic system is arranged between the second half-wave plate and the polarization balance differential detection circuit. All of the above components are arranged in an area surrounded by a radio frequency coil, and the radio frequency coil is arranged in a magnetometer support shell.

[0086] Comparative Example

[0087] In the prior art, while ensuring the consistency of the average pumping rate of the pumping light, the free precession signal amplitude of the free precession atomic magnetometer modulation method using only optical resonance pulses is smaller than that of the present solution. The dead zone of the free precession atomic magnetometer modulation method using only optical resonance pulses is the pumping light direction (z-axis) and the detection light direction (x-axis). The dead zone of the free precession atomic magnetometer modulation method based on optical and magnetic dual resonance pulses in the present invention is the detection light direction (x-axis).

[0088] In the prior art, while ensuring the consistency of the average pumping rate of the pumping light, the free precession signal amplitude of the free precession atomic magnetometer modulation method using only magnetic resonance pulses is smaller than that of the present solution. The dead zone of the free precession atomic magnetometer modulation method using only optical resonance pulses is the xy plane. The dead zone of the free precession atomic magnetometer modulation method based on optical and magnetic dual resonance pulses in the present invention is the detection light direction (x-axis).

[0089] Therefore, the present invention adopts the above-mentioned free precession atomic magnetometer modulation method based on optical and magnetic double resonance pulses, and performs optical pumping and spin polarization vector manipulation by successively applying resonant optical pulses and radio frequency magnetic field pulses to the alkali metal atomic gas chamber, and realizes the free precession signal after the pulse is removed; ultimately, without increasing the complexity of the system, the free precession signal is enhanced, the signal-to-noise ratio of the magnetometer is improved, and the sensitivity of the free precession atomic magnetometer is thereby improved. In addition, the dead zone of the magnetometer is suppressed, and the dead zone of the magnetometer is reduced to a single axis in the detection light direction, providing a new solution for the application of free precession atomic magnetometers.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A modulation method for a free precession atomic magnetometer based on optical-magnetic double resonance pulses, characterized by: The following steps are involved: S1: Turn on the pump laser and the detection laser, adjust the emission frequencies of the pump laser and the detection laser, and make the pump light and the detection light pass through the alkali metal atom gas chamber respectively; S2: The control signal generator inputs a square wave pulse with a duty cycle of 50% and a pulse frequency approximately equal to the Larmor precession frequency corresponding to the magnetic field to the optical intensity modulator to perform optical pumping operation. After a period of time, the modulated optical signal is removed. S3: At the moment when the input signal from the signal generator to the light intensity modulator is removed, a radio frequency pulse with the same frequency as the square wave pulse frequency of the light intensity modulator is applied to control the spin polarization vector to a plane perpendicular to the magnetic field direction, and then the radio frequency pulse is removed; S4: After removing the input signal from the signal generator to the radio frequency coil, the detection light outputs a free precession signal, and the generated free precession signal is collected by a data acquisition device and processed to obtain magnetic field information; In step S2, the specific steps of the optical pumping operation are as follows: S21: Input a square wave pulse with a frequency of approximately the Larmor precession frequency and a duty cycle of 50% to the light intensity modulator through a signal generator, and remove the input signal after a period of time; S22: The duty cycle in step S21 is controlled to remain unchanged, and the frequency of the square wave pulse is changed so that the detection light output signal is maximized when the input signal of the optical intensity modulator is removed, thereby completing the optical pumping operation; In step S3, the specific steps of controlling the spin polarization vector to be perpendicular to the magnetic field direction are as follows: S31: Input a radio frequency pulse signal with the same frequency as the square wave frequency of the light intensity modulator to the radio frequency coil through the signal generator in a direction perpendicular to the plane of the pumping light and the detection light, and remove it after it lasts for less than 0.05ms; S32: Control the RF field action time and frequency to remain unchanged, adjust the RF input signal amplitude so that the signal amplitude is maximized when the RF pulse is removed, and the spin polarization vector will be manipulated to a plane perpendicular to the magnetic field direction.

2. The modulation method of a free precession atomic magnetometer based on optical-magnetic double resonance pulse according to claim 1, characterized in that: The adjustment of the pump laser and the detection laser in step S1 specifically includes the following steps: S11: Adjust the frequency of the pumping light emitted by the pumping laser to the center of the alkali metal atomic spectrum line D1; S12: adjusting the polarization device to generate circularly polarized light, and the circularly polarized light passes through the alkali metal atom gas cell; S13: adjusting the frequency detuning of the detection light emitted by the detection laser to maximize the optical rotation angle of the detection light; S14: Produce linearly polarized light through a polarizer, and allow the linearly polarized light to pass through the alkali metal atom gas cell.

3. The modulation method of a free precession atomic magnetometer based on optical-magnetic double resonance pulse according to claim 1, characterized in that: In step S4, the free precession signal acquisition and processing specifically includes the following steps: S41: After the RF pulse is removed, the spin polarization vector undergoes a free precession process, and the detection light outputs a free precession signal; S42: collecting a free precession signal output by the detection light through a data acquisition device; S43: Process the free precession signal, extract the Larmor precession frequency contained in the free precession signal, and obtain magnetic field information.

4. A free precession atomic magnetometer device based on optical and magnetic double resonance pulses, characterized by: The invention comprises a device for realizing a pumping optical path and a detection optical path of a free precession atomic magnetometer, and implements the steps of a modulation method of a free precession atomic magnetometer based on optical-magnetic double resonance pulse according to any one of claims 1 to 3; The pumping optical path of the free precession atomic magnetometer passes through the pumping laser, the light intensity modulator, the first half-wave plate, the first polarizer, the reflector, the quarter-wave plate and then reaches the alkali metal gas chamber; The detection optical path of the free precession atomic magnetometer passes through the detection laser, the second polarizer, the alkali metal gas cell, the second half-wave plate and then reaches the spectroscopic system; A polarization balance differential detection circuit is provided on one side of the spectroscopic system. A first photodetector and a second photodetector are provided in parallel on the polarization balance differential detection circuit. The reflection side of the spectroscopic system is connected to the first photodetector, and the transmission side of the spectroscopic system is connected to the second photodetector. The output end of the polarization balance differential detection circuit is connected to the input end of the transimpedance amplifier, the output end of the transimpedance amplifier is connected to the input end of the data acquisition device, and the output end of the signal generator is respectively connected to the input end of the light intensity modulator and the input end of the radio frequency coil perpendicular to the direction of the pumping light and the detection light plane.

5. The free precession atomic magnetometer device based on optical-magnetic double resonance pulse according to claim 4, characterized in that: A first polarizer is arranged between the first half-wave plate and the reflector, a quarter-wave plate is arranged between the first polarizer and the alkali metal gas chamber, the second polarizer and the second half-wave plate are respectively arranged on both sides of the alkali metal gas chamber, a non-magnetic electric heating system is arranged on the outside of the alkali metal gas chamber, and a spectroscopic system is arranged between the second half-wave plate and the polarization balance differential detection circuit. All of the above components are arranged in an area surrounded by a radio frequency coil, and the radio frequency coil is arranged in a magnetometer support shell.

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