Method for precise suppression of polarization error of SERF magnetometer

Abstract

A method for precisely suppressing polarization error of a SERF co-magnetometer, by setting a half-wave plate in a detection laser module, wherein the position, angle and fast-slow axis angle of the half-wave plate will directly affect the polarization angle and ellipticity of the detection laser. The polarization error is caused by the transverse light displacement and transverse light pumping caused by the non-ideal linear polarization of the detection light. The half-wave plate can precisely adjust the polarization angle and ellipticity of the detection light, thereby precisely suppressing the polarization error of the SERF co-magnetometer.

Description

Technical Field

[0001] This invention relates to SERF common magnetometer measurement error suppression technology, specifically a method for precisely suppressing polarization errors in SERF common magnetometers. The method involves setting a half-wave plate corresponding to the wavelength of the detection laser in the detection laser module. By rotating the fast and slow axes of the half-wave plate, the position of the plate and its angle with the detection laser are adjusted, achieving precise adjustment of the azimuth and ellipticity of the detection laser from three degrees of freedom. By adjusting to appropriate azimuth and ellipticity, fluctuations in detection noise and transverse light pumping effects are reduced, ultimately suppressing measurement errors in the atomic magnetometer. Background Technology

[0002] SERF common magnetometer is an atomic magnetometer based on spin-exchange relaxation-free (SERF). This magnetometer can also be used as an inertial measurement instrument at different operating points, hence the name SERF common magnetometer, also known as SERF atomic spin common magnetometer.

[0003] The SERF atomic spin common magnetometer is a high-precision magnetometer widely used in fundamental physics research such as testing Lorentz and searching for anomalous spins. In the common magnetometer, the precession signal of the atomic ensemble is obtained from the detection laser. In previous studies, the detection light was considered to be ideally linearly polarized and non-destructive to the system. However, with further research, the transverse optical frequency shift and transverse optical pump caused by non-ideal linear polarization affect the direction and stability of electron spin and amplify other noise introduced by the detection light. The inventors believe that adding a half-wave plate to the detection optical path and changing the position, angle, and fast / slow axis angles of the wave plate can achieve precise control of the polarization state of the detection laser, suppressing noise caused by non-ideal linear polarization, reducing the impact of the detection light on the SERF common magnetometer, and improving the measurement accuracy of the SERF common magnetometer. Therefore, the inventors have completed this invention. Summary of the Invention

[0004] This invention addresses the deficiencies and shortcomings of existing technologies by providing a precise method for suppressing polarization errors in a SERF common magnetometer. This method involves incorporating a half-wave plate into the detection laser module. The position, angle, and fast / slow axis angles of the half-wave plate directly affect the polarization angle and ellipticity of the detection laser. The polarization error is caused by lateral optical displacement and pumping due to the non-ideal linear polarization of the detection light. The half-wave plate allows for precise adjustment of the polarization angle and ellipticity of the detection light, thereby achieving accurate suppression of polarization errors in the SERF common magnetometer.

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

[0006] A method for accurately suppressing polarization error in a SERF common magnetometer is characterized by the following steps: First half-wave plate, Glan Taylor prism, additional half-wave plate, and alkali metal gas cell are sequentially arranged along the x-axis of the SERF common magnetometer on the detection optical path. A polarization analyzer is installed at the emission point of the detection laser in the alkali metal gas cell. The polarization analyzer accurately determines the polarization state of the detection laser. Based on the polarization error corresponding to the polarization state, the polarization azimuth angle and ellipticity of the detection laser entering the alkali metal gas cell are precisely adjusted by the additional half-wave plate to accurately suppress the polarization error. After this, the polarization analyzer is removed. A second polarization beam splitter is installed at the emission point of the detection laser in the alkali metal gas cell. The detection laser is split by the second polarization beam splitter. A photodetector converts the two beams into electrical signals and inputs them to the input of a differential circuit. The output of the differential circuit is connected to a host computer.

[0007] The newly added half-wave plate in the detection optical path is installed on the lens frame, which has the function of adjusting the half-wave plate in both horizontal and vertical planes.

[0008] The alkali metal gas chamber is surrounded, from the inside out, by a non-magnetic electric heating system, a triaxial magnetic compensation coil, and a magnetic shielding barrel. The triaxial magnetic compensation coil is connected to a function generator. The pump light is generated by a pump laser, expanded by a first convex lens and a second convex lens, and reflected along the z-axis by a first reflecting mirror. The light then passes sequentially through a first linear polarizer, a first liquid crystal variable phase retarder, a second linear polarizer, a second half-wave plate, a first polarizing beam splitter, and a first quarter-wave plate before entering the alkali metal gas chamber. The first polarizing beam splitter is connected to the first liquid crystal variable phase retarder via a photodetector and a first electronic control unit, enabling real-time measurement and stabilization of the pump light power density before it enters the alkali metal gas chamber.

[0009] The detection light is generated by a detection laser and passes sequentially through a third linear polarizer, a second liquid crystal variable phase retarder, a fourth linear polarizer, a second reflector, a first half-wave plate in the detection light path, a GlanTylene prism, and an additional half-wave plate in the detection light path before entering the alkali metal gas cell. The GlanTylene prism is then connected back to the second liquid crystal variable phase retarder via a photodetector and a second electronic control unit, thereby enabling real-time measurement and stabilization of the detection light power density.

[0010] In the SERF common magnetometer, the system output voltage signal U is expressed as follows:

[0011]

[0012] In the formula, K PD R is the conversion coefficient of the photodetector, I is the intensity of the detection light, and r is the conversion coefficient of the photodetector. eLet be the electron radius, c be the speed of light, f be the oscillation intensity, and L be the Lorentz function related to the frequency of the detection light. To detect the electronic polarizability along the light direction, the positive x-axis represents the direction of light propagation. The transient solution of the electronic polarizability... The relationship with time t is as follows:

[0013]

[0014] Where R2 represents the electron spin-related magnetic field term; C1 is the integration constant; in In this context, e is the base of the natural logarithm, and Q is the slowing factor. Let R be the total electronic relaxation rate; m To detect the photopumping rate, it is related to the intensity of the detection light, s m To detect the optical pump vector, which depends on the ellipticity of the light, the expression for the output signal U is as follows:

[0015]

[0016] In the expression for the output signal U, when the gas chamber temperature and pump optical power are determined, R2, Q, and Both I and L are fixed values. When the detected optical power and frequency are determined, I and L are fixed values. The polarization error is the value of s corresponding to the polarization state of the detected light. m The resulting error, and by changing s m The value, The change is made, which in turn changes U; when there is no input, the fine-tuning of s is performed. m , It is expected that the output signal U will not be affected by the intensity of the detection light, and the change caused by the change in the intensity of the detection light will be greatly reduced, thus suppressing the polarization error.

[0017] The system includes a pump laser, which is a distributed Bragg reflector (DBR) laser. The DBR laser provides pump light, which is frequency-locked using saturable absorption frequency locking technology. The pump light is first expanded into an 8 mm circular spot by a pair of plano-convex lenses to ensure maximum coverage of the gas cell. Then, its power is stabilized by a liquid crystal variable phase retarder module, and finally, it is polarized into fully circularly polarized light by an optical isolation module before entering the alkali metal gas cell. The detection light comes from a detection laser, which is a distributed feedback DFB laser. The detection light spot diameter is 1 mm. The probe light path has the same optical power stabilization module as the pump light path. In addition, before entering the alkali metal gas cell, it is repolarized using a Glan Taylor prism to ensure the linearity of the detection light.

[0018] Includes the following steps:

[0019] Step 1: Turn off the pump laser and optical switch. Adjust the non-magnetic electric heating system according to the type of alkali metal atoms to control the temperature of the alkali metal gas chamber between 160℃ and 190℃. At this time, the alkali metal gas chamber will only absorb the linearly polarized beam emitted by the detection laser module. Change the injection current of the detection laser and use an optical power meter to test the light intensity of the detection beam passing through the alkali metal gas chamber. Record the light intensity values ​​under different injection currents to calibrate the detection light intensity. Turn on the pump laser and optical switch, and adjust the pump laser so that the frequency of the emitted laser is at the center of the D1 line of the alkali metal contained in the alkali metal gas chamber.

[0020] Step 2: Set the polarization analyzer at the light output of the alkali metal gas cell, and adjust the half-wave plate until the light obtained by the polarization analyzer is linearly polarized with a polarization angle of 45° and an ellipticity of 0. Remove the polarization analyzer, set the polarization beam splitter, and use the host computer to calculate the output of the SERF atomic magnetometer. Perform three-dimensional magnetic compensation on the SERF atomic magnetometer to make the magnetic field sensed by the alkali metal gas cell zero. At this time, the SERF atomic magnetometer enters normal working state. Then, change the injection current of the detection light to achieve a step change in the intensity of the detection light, and record the step output under this condition.

[0021] Step 3: Repeat step 2 to fine-tune the half-wave plate to achieve fine-tuning of the ellipticity. Record the step output of the detection light intensity under different ellipticities. Find the ellipticity with the smallest steady-state value of the step output under the same detection light intensity step condition. This is the condition under which the polarization error is best suppressed.

[0022] The technical effects of this invention are as follows: This invention provides a method for accurately suppressing polarization errors in a SERF common magnetometer. By adding a half-wave plate to the detection laser optical path, the azimuth angle and ellipticity of the detection laser are precisely adjusted, thereby achieving insensitivity of electronic polarization to the intensity of the detection light and significantly suppressing the sensitivity of the output signal to the intensity of the detection light, thus achieving accurate suppression of polarization errors.

[0023] The advantages of this invention compared with the prior art are as follows: (1) Current research on polarization error does not analyze it from a system perspective. Most of the work focuses on suppressing transverse optical frequency shift and optical pump. However, such suppression methods usually change the operating point of the common magnetometer, which will affect other parameters, such as the scaling factor. The method of this invention does not change the operating point and achieves the suppression of polarization error without affecting the normal operation of the device. (2) This invention only adds a half-wave plate to the detection optical path without adding too many devices and circuit systems, and can be applied to miniaturized instruments. Attached Figure Description

[0024] Figure 1 A schematic diagram of the SERF atomic common magnetometer structure involved in implementing the precise suppression method for polarization error of a SERF common magnetometer according to the present invention. Figure 1The addition of a half-wave plate 20 to the detection optical path allows for precise adjustment of the polarization azimuth and ellipticity of the detection laser 12 entering the alkali metal gas chamber 21. The polarization state of the detection light is accurately determined by a polarization analyzer, and the polarization error can be suppressed by fine-tuning the half-wave plate to a suitable polarization state.

[0025] The reference numerals in the attached figures are listed below: 1-Pump laser; 2-First convex lens; 3-Second convex lens; 4-First reflecting mirror; 5-First linear polarizer; 6-First liquid crystal variable phase retarder; 7-Second linear polarizer; 8-Second half-wave plate; 9-First electronic control unit; 10-First polarization beam splitter; 11-Quarter-wave plate; 12-Detection laser; 13-Third linear polarizer; 14-Second liquid crystal variable phase retarder; 15-Fourth linear polarizer; 16 - Second electronic control unit; 17- Second reflector; 18- First half-wave plate of the detection optical path; 19- Glan-Taylor prism; 20- New half-wave plate (or third half-wave plate) of the detection optical path; 21- Alkali metal gas chamber; 22- Non-magnetic heating system; 23- Three-axis magnetic compensation system; 24- Magnetic shielding barrel; 25- Second polarization beam splitter; 26- Differential circuit; 27- Polarization analyzer; 28- Host computer; xyz- Cartesian coordinate system three axes (x-axis, y-axis, z-axis). Detailed Implementation

[0026] The following is in conjunction with the attached diagram ( Figure 1 The invention will be described in the following sections and examples.

[0027] Figure 1 A schematic diagram of the SERF atomic common magnetometer structure involved in implementing the precise suppression method for polarization error of a SERF common magnetometer according to the present invention. (Reference) Figure 1 As shown, a method for accurately suppressing polarization error in a SERF common magnetometer includes sequentially arranging a first half-wave plate 18, a Glan Taylor prism 19, a newly added half-wave plate 20, and an alkali metal gas cell 21 along the x-axis of the SERF common magnetometer. A polarization analyzer 27 is installed at the laser emission point in the alkali metal gas cell 21. The polarization analyzer 27 accurately determines the polarization state of the laser. Based on the polarization error corresponding to the polarization state, the newly added half-wave plate 20 precisely adjusts the polarization azimuth angle and ellipticity of the laser entering the alkali metal gas cell 21, thereby accurately suppressing the polarization error. The polarization analyzer 27 is then removed, and a second polarization beam splitter 25 is installed at the laser emission point in the alkali metal gas cell 21. The laser beam is split by the second polarization beam splitter 25. A photodetector converts the two beams into electrical signals, which are input to the input of a differential circuit 26. The output of the differential circuit 26 is connected to a host computer 28.

[0028] The newly added half-wave plate 20 in the detection optical path is mounted on the lens frame, which has the function of adjusting the half-wave plate in both horizontal and vertical planes. Around the alkali metal gas chamber 21, from the inside out, are arranged a non-magnetic electric heating system 22, a triaxial magnetic compensation coil 23, and a magnetic shielding barrel 24. The triaxial magnetic compensation coil 23 is connected to the function generator. The pump light is generated by the pump laser 1, expanded by the first convex lens 2 and the second convex lens 3, and reflected by the first reflecting mirror 4 to be along the z-axis. It then sequentially passes through the first linear polarizer 5, the first liquid crystal variable phase retarder 6, the second linear polarizer 7, the second half-wave plate 8, the first polarizing beam splitter 10, and the first quarter-wave plate 11 before entering the alkali metal gas chamber 21. The first polarizing beam splitter 10 is sequentially connected back to the first liquid crystal variable phase retarder 6 through a photodetector and the first electronic control unit 9. The detection light is generated by the detection laser 12 and passes sequentially through the third linear polarizer 13, the second liquid crystal variable phase retarder 14, the fourth linear polarizer 15, the second reflector 17, the first half-wave plate 18 of the detection optical path, the GlanTylene prism 19, and the newly added half-wave plate 20 of the detection optical path before entering the alkali metal gas chamber 21. The GlanTylene prism 19 is then connected back to the second liquid crystal variable phase retarder 14 via a photodetector and the second electronic control unit 16.

[0029] A method for precisely suppressing polarization errors in a SERF common magnetometer involves incorporating a half-wave plate into the detection laser module. The position, angle, and fast / slow axis angles of the half-wave plate directly affect the polarization angle and ellipticity of the detection laser. The polarization error is caused by lateral optical displacement and pumping due to the non-ideal linear polarization of the detection light. The half-wave plate allows for precise adjustment of the polarization angle and ellipticity of the detection light, thereby achieving accurate suppression of polarization errors in the SERF common magnetometer.

[0030] refer to Figure 1 As shown, the system structure of a method for precisely suppressing polarization error in a SERF atomic common magnetometer includes a pump laser module and a detection laser module. A half-wave plate 20 is set in the optical path of the detection laser module to precisely adjust the polarization state of the detection light. The linear polarization state of the detection light directly affects the polarization error of the common magnetometer. The half-wave plate 20 is used to adjust the detection light to an appropriate azimuth angle and ellipticity to achieve precise suppression of the polarization error of the common magnetometer. The polarization error analysis uses the following formula:

[0031] In the SERF common magnetometer, the system output voltage signal U can be expressed as:

[0032]

[0033] In the formula, K PD R is the conversion coefficient of the photodetector, I is the intensity of the detection light, and r is the conversion coefficient of the photodetector. eLet f be the electron radius, c be the speed of light, f be the oscillation intensity (usually 3 / 2), and L be the Lorentz function related to the frequency of the detection light. To detect the electronic polarizability along the light direction, with the positive x-axis pointing in the direction of light propagation, the transient solution of the electronic polarizability is... The relationship with time t can be expressed by the following formula:

[0034]

[0035] Where R2 represents the electron spin-related magnetic field term; C1 is the integration constant; in In this context, e is the base of the natural logarithm, and Q is the slowing factor. The total relaxation rate of electrons can be considered as R m The sum of other relaxation terms; R m The photopumping rate is related to the intensity of the detection light; s m To detect the optical pump vector, we need to consider the ellipticity of the light. Therefore, the output signal U can be written as:

[0036]

[0037] According to the output expression of U, when the gas chamber temperature and pump optical power are determined, R2, Q, and Except for R m The relaxation term outside the equation is a fixed value. When the detected optical power and frequency are determined, I and L are fixed values. Therefore, only s in the formula U... m An adjustable amount.

[0038] The polarization error is the s corresponding to the detected light polarization state. m The resulting error, and by changing s m The value, It can be changed, and thus U can be changed. When there is no input, fine-tuning s... m P x e It is expected that the output U will not be affected by the intensity of the detection light, and the change caused by the change in the intensity of the detection light will be greatly reduced, thus suppressing the polarization error.

[0039] In this embodiment, the alkali metal chamber is a spherical chamber with a diameter of 10 mm, containing a mixture of alkali metals K and Rb, and 2280 Torr (approximately 3 atmospheres) of oxygen. 21 Ne and 40 Torr (approximately 0.05 atmospheres) of N2, where the density ratio of K to Rb is 1:130.

[0040] The pump light module includes a DBR laser 1, which provides pump light whose frequency is locked using saturable absorption frequency locking technology. The pump light is first expanded into an 8mm circular spot by a pair of plano-convex lenses 2 and 3 to ensure maximum coverage of the gas chamber 21. Then, its power is stabilized by a liquid crystal variable phase delay module 6, and finally, it is polarized into fully circularly polarized light by a quarter-wave plate before entering the alkali metal gas chamber 21. The detection light module uses a DFB laser 12, which provides the detection light with a spot diameter of 1mm. The probe light path has the same optical power stabilization module 14 as the pump light path. Furthermore, before entering the gas chamber, a Glan-Taylor prism 19 is used for repolarization to ensure the linearity of the detection light. Around the alkali metal gas chamber, from the inside out, are a non-magnetic electric heating system 22, a triaxial magnetic compensation coil 23, and a magnetic shielding barrel 24, the triaxial magnetic compensation coil being connected to a function generator.

[0041] The half-wave plate 20 used for polarization error suppression is mounted on a self-made frame to ensure that adjustments can be made in both the horizontal and vertical planes.

[0042] A method for accurately suppressing polarization errors in a SERF common magnetometer includes the following steps:

[0043] Step 1: Turn off the pump laser and optical switch. Adjust the non-magnetic heating system according to the type of alkali metal atoms to control the temperature of the alkali metal chamber between 160℃ and 190℃. At this temperature, the alkali metal chamber will only absorb the linearly polarized beam emitted by the detection laser module. Change the injection current of the detection laser and use an optical power meter to test the light intensity of the detection beam passing through the alkali metal chamber. Record the light intensity values ​​under different injection currents to calibrate the detection light intensity. Turn on the pump laser and optical switch, and adjust the pump laser so that the frequency of its emitted laser is centered on the D1 line of the alkali metal K contained in the alkali metal chamber.

[0044] Step 2: Set the polarization analyzer at the point of light detection, and adjust the half-wave plate until the light obtained by the polarization analyzer is linearly polarized light with a polarization angle of 45° and an ellipticity of 0. Remove the polarization analyzer, set the polarization beam splitter 25, and use the host computer to calculate the output of the SERF atomic common magnetometer. Perform three-dimensional magnetic compensation on the SERF atomic common magnetometer to make the magnetic field sensed by the alkali metal gas cell zero. At this time, the SERF atomic common magnetometer enters the normal working state. Then, change the injection current of the detection light to achieve a step change in the intensity of the detection light, and record the step output under this condition.

[0045] Step 3: Repeat Step 2 to fine-tune the half-wave plate to adjust the ellipticity, and record the step output of the detection light intensity under different ellipticities. Find the ellipticity that minimizes the steady-state value of the step output under the same detection light intensity step condition; this is the condition under which the polarization error is best suppressed.

[0046] A method for accurately suppressing polarization error in a SERF common magnetometer is characterized by the precise suppression of polarization error. A half-wave plate corresponding to the wavelength of the detection laser is set in the detection laser module. The detection light obtains a suitable polarization state after passing through the half-wave plate to suppress polarization error.

[0047] The half-wave plate used for polarization error suppression is mounted on the lens frame to ensure that adjustments can be made in both the horizontal and vertical planes.

[0048] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A method for accurately suppressing polarization error in a SERF common magnetometer, characterized in that, The SERF common magnetometer includes a detection optical path consisting of a first half-wave plate, a Glan Taylor prism, a newly added half-wave plate, and an alkali metal gas cell, arranged sequentially along the x-axis. A polarization analyzer is installed at the laser emission point in the alkali metal gas cell to accurately determine the polarization state of the detection laser. Based on the polarization error corresponding to the polarization state, the polarization azimuth and ellipticity of the detection laser entering the alkali metal gas cell are precisely adjusted by the newly added half-wave plate to accurately suppress the polarization error. After the polarization analyzer is removed, a second polarization beam splitter is installed at the laser emission point in the alkali metal gas cell. The detection laser is split by the second polarization beam splitter. A photodetector converts the two beams into electrical signals and inputs them to the input of a differential circuit. The output of the differential circuit is connected to a host computer.

2. The method for accurately suppressing polarization error of the SERF common magnetometer according to claim 1, characterized in that, The newly added half-wave plate in the detection optical path is installed on the lens frame, which has the function of adjusting the half-wave plate in both horizontal and vertical planes.

3. The method for accurately suppressing polarization error of the SERF common magnetometer according to claim 1, characterized in that, The alkali metal gas chamber is surrounded by a non-magnetic electric heating system, a triaxial magnetic compensation coil, and a magnetic shielding barrel arranged sequentially from the inside out. The triaxial magnetic compensation coil is connected to a function generator.

4. The method for accurately suppressing polarization error of the SERF common magnetometer according to claim 1, characterized in that, The pump light is generated by a pump laser, expanded by a first convex lens and a second convex lens, and reflected by a first reflecting mirror to be along the z-axis. It then passes sequentially through a first linear polarizer, a first liquid crystal variable phase retarder, a second linear polarizer, a second half-wave plate, a first polarizing beam splitter, and a first quarter-wave plate before entering the alkali metal gas cell. The first polarizing beam splitter is connected to the first liquid crystal variable phase retarder via a photodetector and a first electronic control unit to achieve real-time measurement and stabilization of the pump light power density before entering the alkali metal gas cell.

5. The method for accurately suppressing polarization error of the SERF common magnetometer according to claim 1, characterized in that, The detection light is generated by a detection laser and passes sequentially through a third linear polarizer, a second liquid crystal variable phase retarder, a fourth linear polarizer, a second reflector, a first half-wave plate of the detection light path, a Glan Taylor prism, and an additional half-wave plate of the detection light path before entering the alkali metal gas chamber. The Glan Taylor prism is then connected back to the second liquid crystal variable phase retarder via a photodetector and a second electronic control unit, thereby realizing real-time measurement and stabilization of the detection light power density.

6. The method for accurately suppressing polarization error of the SERF common magnetometer according to claim 1, characterized in that, In the SERF common magnetometer, the system output voltage signal The expression is as follows: ， In the formula, denoted as the conversion coefficient of the photodetector. To detect light intensity, For electron radius, At the speed of light, The intensity of the oscillation. The Lorentz function is related to the frequency of the detected light. To detect the electronic polarizability in the direction of light, The positive axis is the direction of light propagation, and the transient solution of electronic polarizability is... (t) and time The relationship is as follows: ， in, This represents the magnetic field term related to electron spin; It is the integration constant; in middle, The base of the natural logarithm, As a slowing factor, Let be the total electronic relaxation rate; let be... The photo-pumping rate is related to the intensity of the detection light. To detect the optical pump vector, which depends on the ellipticity of the light, the output signal is determined. The expression is as follows: ， In the output signal In the expression, when the gas chamber temperature and pump optical power are determined, , and All are fixed values; when the detected optical power and frequency are determined, and The polarization error is a fixed value, which is the polarization state of the detected light. The resulting error, and by changing The value, To be changed, and thus to change Fine-tuning when there is no input. , It is expected that the output signal will not be affected by the intensity of the detection light. The change caused by the change in the intensity of the detection light will also be greatly reduced, and the polarization error will be suppressed.

7. The method for accurately suppressing polarization error of the SERF common magnetometer according to claim 1, characterized in that, The system includes a pump laser, which is a distributed Bragg reflector (DBR) laser. The DBR laser provides pump light, which is frequency-locked using saturable absorption frequency locking technology. The pump light is first expanded into an 8 mm circular spot by a pair of plano-convex lenses to ensure maximum coverage of the gas cell. Then, its power is stabilized by a liquid crystal variable phase retarder module, and finally, it is polarized into fully circularly polarized light by an optical isolation module before entering the alkali metal gas cell. The detection light comes from a detection laser, which is a distributed feedback DFB laser. The detection light spot diameter is 1 mm. The probe light path has the same optical power stabilization module as the pump light path. In addition, before entering the alkali metal gas cell, it is repolarized using a Glan Taylor prism to ensure the linearity of the detection light.

8. The method for accurately suppressing polarization error of the SERF common magnetometer according to claim 1, characterized in that, Includes the following steps: Step 1: Turn off the pump laser and optical switch. Adjust the non-magnetic electric heating system according to the type of alkali metal atoms to control the temperature of the alkali metal gas chamber between 160℃ and 190℃. At this time, the alkali metal gas chamber will only absorb the linearly polarized beam emitted by the detection laser module. Change the injection current of the detection laser and use an optical power meter to test the light intensity of the detection beam passing through the alkali metal gas chamber. Record the light intensity values ​​under different injection currents to calibrate the detection light intensity. Turn on the pump laser and optical switch, and adjust the pump laser so that the frequency of the emitted laser is at the center of the D1 line of the alkali metal contained in the alkali metal gas chamber. Step 2: Set the polarization analyzer at the light output of the alkali metal gas cell, and adjust the half-wave plate until the light obtained by the polarization analyzer is linearly polarized with a polarization angle of 45° and an ellipticity of 0. Remove the polarization analyzer, set the polarization beam splitter, and use the host computer to calculate the output of the SERF atomic magnetometer. Perform three-dimensional magnetic compensation on the SERF atomic magnetometer to make the magnetic field sensed by the alkali metal gas cell zero. At this time, the SERF atomic magnetometer enters normal working state. Then, change the injection current of the detection light to achieve a step change in the intensity of the detection light, and record the step output under this condition. Step 3: Repeat step 2 to fine-tune the half-wave plate to achieve fine-tuning of the ellipticity. Record the step output of the detection light intensity under different ellipticities. Find the ellipticity with the smallest steady-state value of the step output under the same detection light intensity step condition. This is the condition under which the polarization error is best suppressed.

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