Method and device for measuring polarizability of alkali metal atom in SERF state based on transient response

Abstract

The application discloses a method and device for measuring the polarizability of alkali metal atoms in a SERF state based on transient response, which comprises the following steps: adding a chopper in a pumping light path to modulate a pumping light beam at a certain frequency, and applying a known magnetic field in a transverse direction to make the alkali metal atoms achieve the SERF state, wherein the modulation time of the chopper should be greater than the polarization time of the alkali metal atoms to achieve the SERF state, the alkali metal atoms are fully polarized in an open state, and the alkali metal atoms are fully depolarized in a closed state to obtain a more accurate measurement result of the polarizability of the alkali metal atoms, a transient response equation of the atoms is established to obtain the resonance frequency of the transverse magnetic field through fitting, and the polarizability of the alkali metal atoms is solved through a slow factor, which provides a more accurate parameter measurement means for further developing a SERF magnetometer device with higher sensitivity and a SERF inertial measurement device, and can be applied to the fields of basic physics research and extremely weak magnetic brain magnetic detection.

Description

Technical Field

[0001] This invention relates to the field of SERF (Spin-exchange relaxation-Free) atomic magnetometer instrumentation technology, and in particular to a method and apparatus for measuring the polarizability of alkali metal atoms in the SERF state based on transient response. This is achieved by adding a chopper to the pump optical path to modulate the pump beam at a certain frequency and applying a known magnetic field laterally. The chopper modulation time should be greater than the polarization time of the alkali metal atoms to reach the SERF state. In the on state, the atoms are fully polarized, and in the off state, the atoms are fully depolarized, resulting in a more accurate measurement of the polarizability of alkali metal atoms. The resonance frequency of the transverse magnetic field is obtained by fitting an atomic transient response equation, and the polarizability of the alkali metal atoms is obtained by solving for a slowing factor. This provides a more accurate parameter measurement means for further developing more sensitive SERF magnetometer devices and SERF inertial measurement devices. Background Technology

[0002] Spin-exchange relaxation-free (SERF) state atomic spin magnetic field measurement is a novel magnetic field measurement technique that has emerged in recent years amidst the rapid development of quantum science and technology. Its theoretical sensitivity for magnetic field measurement can reach aT (1aT = 10⁻⁶). -18 The SERF effect is on the order of T. Atomic SERF effects can be applied to cutting-edge fields of physics, such as experiments verifying charge, parity, and time reversal symmetry (CPT symmetry) and measuring electron electric dipole moments. High-sensitivity SERF magnetometers are of great significance in applications such as measuring extremely weak magnetocardiography and magnetoencephalography, as well as high-resolution imaging and analysis of magnetic fields in matter.

[0003] Alkali metal atom polarizability is one of the important parameters of the SERF atom spin magnetic field measurement device. It determines the accuracy limit that the magnetic field measurement device can achieve, as well as the above-mentioned application exploration capabilities. Accurately measuring the polarizability of alkali metals is a prerequisite for judging the performance of the atomic system itself.

[0004] Common methods for detecting the polarizability of alkali metal atoms include electron paramagnetic resonance (EPR), pump light intensity attenuation, and near-resonance frequency resonance. For SERF magnetometers, the EPR method requires applying a magnetic field on the order of G to measure electron polarizability by analyzing the distribution probability of electrons at each energy level of the atom. The presence of a large magnetic field affects the SERF state conditions, rendering the device inoperable. The pump light transmission attenuation method suffers from inaccuracies due to the large optical depth of the SERF magnetometer, preventing the pump light from transmitting completely in the pump direction. Near-resonance light conditions do not meet the operating conditions of SERF-state atoms. Currently, existing methods for detecting the polarizability of alkali metal atoms are difficult to implement under SERF state operating conditions, resulting in low measurement accuracy. Summary of the Invention

[0005] This invention addresses the deficiencies and shortcomings of existing technologies by providing a method and apparatus for measuring the polarizability of alkali metal atoms in the SERF state based on transient response. This is achieved by adding a chopper to the pump optical path to modulate the pump beam at a certain frequency and applying a known magnetic field laterally. The chopper modulation time should be greater than the polarization time of the alkali metal atoms in the SERF state. In the on state, the atoms are fully polarized, and in the off state, they are fully depolarized, resulting in a more accurate measurement of the alkali metal atom polarizability. The resonance frequency of the transverse magnetic field is obtained by fitting an atomic transient response equation, and the alkali metal atom polarizability is obtained by solving for a slowing factor. This provides a more accurate parameter measurement method for further developing more sensitive SERF magnetometers and SERF inertial measurement devices.

[0006] The technical solution of the present invention is as follows:

[0007] A method for measuring the polarizability of SERF-state alkali metal atoms based on transient response is characterized by comprising: converting the laser output from a pump laser into circularly polarized light by sequentially passing it through a Glan Taylor prism and a quarter-wave plate; modulating the intensity of the pump light of the circularly polarized light using a chopper, wherein the modulation time of the chopper is greater than the polarization time of the alkali metal atoms reaching the SERF state; and applying a Y-axis magnetic field B in the Y-axis direction, which is perpendicular to both the Z-axis pump light and the X-axis detection light, using a triaxial magnetic field coil. y Linearly polarized detection light, Y-axis magnetic field B y The modulated circularly polarized pump light is applied to alkali metal atoms in the alkali metal gas cell. The linearly polarized detection light is used to detect the transient spin precession process of the alkali metal atoms. After passing through the alkali metal gas cell, the linearly polarized detection light passes through a quarter-wave plate, a photoelastic modulator, and a Glan-Taylor prism in sequence to reach a photodetector. The optical signal is converted into an electrical signal and input into a signal acquisition system through a multi-channel lock-in amplifier. In the signal acquisition system, the transient signal y of the atomic spin precession is fitted to obtain the alkali metal atom spin precession slowing factor q, thereby calculating the SERF state alkali metal atom polarizability P based on the transient response.

[0008] q=g / γ e ×B y Where g is the fitting parameter or fitting coefficient, γ e The gyromagnetic ratio of alkali metal atoms;

[0009] g is determined from the following fitting formula:

[0010] y = ae -(bt) [b cos(gt)+d sin(gt)]+h, where a, b, d, and h are all fitted values, e is the natural constant, and t is time;

[0011] The relationship between q and P is as follows:

[0012] When alkali metal atoms are 85 When Rb, q=(38+52P) 2 +6P 4 ) / (3+10P 2 +3P 4 );

[0013] When alkali metal atoms are 87 Rb or 39 At time K, q = (6 + 2P) 2 ) / (1+P 2 );

[0014] When alkali metal atoms are 41 At time K, q = (6 + P) 2 ) / (1+P 2 );

[0015] When alkali metal atoms are 133 When Cs, q = (22 + 70P) 2 +34P 4 +2P 6 ) / (1+7P 2 +7P 4 +P 6 ).

[0016] The ambient magnetic field is shielded by a magnetic shielding system, and the triaxial residual magnetism is further compensated using a triaxial magnetic field coil. After compensating for the residual magnetism, a B force with an amplitude not exceeding 5 nT is applied. y .

[0017] The alkali metal atom in the alkali metal chamber is one of potassium, rubidium, or cesium. It is filled with buffer gas helium and quenching gas nitrogen. The helium pressure is greater than 1 atmosphere, which slows down the spin of the atoms.

[0018] The polarization time of the alkali metal atoms to the SERF state is on the order of milliseconds. The modulation frequency of the chopper is 0.5 to 2 Hz. The atoms are fully polarized when the chopper is on and fully depolarized when the chopper is off.

[0019] The X-axis component Px of the alkali metal atomic polarizability P and the photorotation angle θ of the detection light pr The direct proportional relationship is as follows:

[0020]

[0021] Where l is the distance the laser travels through the gas chamber, and r e Let c be the classical electron radius, c be the speed of light, n be the density of alkali metal atoms, and P be the atomic density. x f is the projection of the spin polarization of alkali metal atoms along the x-axis. D2 v is the oscillation intensity of line D2, and v is the frequency of the detection light. D2 Γ is the center frequency of the D2 line of alkali metal atoms. L This represents the pressure broadening value of the D2 line of alkali metal atoms.

[0022] The relationship between the slowing factor and the polarizability oscillation process is as follows:

[0023]

[0024] Where t is time, e is the natural constant, and R p R is the pumping rate. rel Let ω be the relaxation rate, k0 and k1 be the amplitude parameters, q(P) be the slowing factor, and ω be the relaxation rate. y ω is an intermediate quantity. y =γ e ×B y γ e P is the gyromagnetic ratio of alkali metal atoms. x (t) represents the function of Px as a function of time t, where Px is the projection of the spin polarizability of the alkali metal atom onto the x-axis.

[0025] A transient response-based SERF state alkali metal atom polarizability measurement device is used to implement the aforementioned transient response-based SERF state alkali metal atom polarizability measurement method. The device is characterized by comprising a pump laser and a detection laser. The pump laser is sequentially connected to the pump light incident end of the alkali metal gas cell via a first GlanTell prism, a quarter-wave plate, a chopper, and a first beam expander. The pump light emitting end of the alkali metal gas cell is sequentially connected to a signal acquisition system via a first photodetector and a multi-channel lock-in amplifier. The detection laser is sequentially connected to the detection light incident end of the alkali metal gas cell via a half-wave plate, a second beam expander, and a second GlanTell prism. The detection light emitting end of the alkali metal gas cell is sequentially connected to the signal acquisition system via a quarter-wave plate, a photoelastic modulator, a third GlanTell prism, a second photodetector, and a multi-channel lock-in amplifier.

[0026] The alkali metal gas chamber is surrounded by a non-magnetic electric heating system, a triaxial magnetic field coil, and a magnetic shielding system. The triaxial magnetic field coil is connected to a signal generator.

[0027] The technical effects of this invention are as follows: This invention is based on a transient response-based method and apparatus for measuring the polarizability of SERF-state alkali metal atoms. By adding a chopper to the pump optical path to modulate the pump beam at a certain frequency and applying a known magnetic field laterally to achieve modulation of atomic spin polarization, the resonance frequency of the transverse magnetic field is obtained by fitting the atomic transient response equation, and the polarizability of alkali metal atoms is obtained by solving for the slowing factor. The operation process is simple and convenient, the measurement time is short, and the accuracy is high. It provides a basic parameter measurement means for optimizing the performance of SERF magnetometers and can be applied to basic physics research and the field of extremely weak magnetic field detection of the heart and brain. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the SERF state alkali metal atom polarizability measurement device based on transient response, which implements the present invention. SERF (Spin-exchange relaxation-Free) is a spin-exchange relaxation-free process.

[0029] Figure 2 This is a schematic diagram of the process for implementing the SERF state alkali metal atom polarizability measurement method based on transient response of the present invention. Figure 2 The process includes: Step 1, SERF magnetic field measurement and triaxial in-situ magnetic compensation; Step 2, applying a known magnetic field to the Y-axis and using a chopper to apply a certain frequency modulated pump light to the Z-axis; Step 3, using a signal acquisition system to output the instantaneous response signal of the magnetometer and obtaining the resonant frequency parameter of the transverse magnetic field through MATLAB fitting; Step 4, calculating the alkali metal slowing factor through parameter g; and Step 5, obtaining the electronic polarizability based on the relationship between the slowing factor and the alkali metal electronic polarizability.

[0030] The reference numerals in the attached diagram are listed below: 1-Pump laser; 2-First Glan-Taylor prism; 3-1 / 4 waveplate; 4-Chopper; 5-First beam expander; 6-First photodetector; 7-Detection laser; 8-1 / 2 waveplate; 9-Second beam expander; 10-Second Glan-Taylor prism; 11-1 / 4 waveplate; 12-Photoelastic modulator; 13-Third Glan-Taylor prism; 14-Second photodetector; 15-Signal generator; 16-Non-magnetic electric heating system; 17-Alkali metal gas chamber; 18-Triaxial magnetic field coil; 19-Multi-channel lock-in amplifier; 20-Signal acquisition system; 21-Magnetic shielding system. Detailed Implementation

[0031] The following is in conjunction with the attached diagram ( Figures 1-2 The present invention will be described below.

[0032] Figure 1 This is a schematic diagram of the SERF state alkali metal atom polarizability measurement device based on transient response, which is used to implement the present invention. Figure 2 This is a schematic diagram illustrating the process of implementing the SERF-state alkali metal atom polarizability measurement method based on transient response of this invention. (Reference) Figures 1 to 2 A method for measuring the polarizability of SERF-state alkali metal atoms based on transient response includes: passing the laser output from a pump laser sequentially through a Glan Taylor prism and a quarter-wave plate to convert it into circularly polarized light; modulating the intensity of the pump light of the circularly polarized light using a chopper, wherein the modulation time of the chopper is greater than the polarization time of the alkali metal atoms reaching the SERF state; and applying a Y-axis magnetic field B in the Y-axis direction, which is perpendicular to both the Z-axis pump light and the X-axis detection light, using a triaxial magnetic field coil. y Linearly polarized detection light, Y-axis magnetic field B y The modulated circularly polarized pump light is applied to alkali metal atoms in the alkali metal gas cell. The linearly polarized detection light is used to detect the transient spin precession process of the alkali metal atoms. After passing through the alkali metal gas cell, the linearly polarized detection light passes through a quarter-wave plate, a photoelastic modulator, and a Glan-Taylor prism in sequence to reach a photodetector. The optical signal is converted into an electrical signal and input into a signal acquisition system through a multi-channel lock-in amplifier. In the signal acquisition system, the transient signal y of the atomic spin precession is fitted to obtain the alkali metal atom spin precession slowing factor q, thereby calculating the SERF state alkali metal atom polarizability P based on the transient response.

[0033] q=g / γ e ×B y Where g is the fitting parameter or fitting coefficient, γ e The gyromagnetic ratio of alkali metal atoms; g is determined from the following fitted formula: y = ae -(bt)[b cos(gt)+d sin(gt)]+h, where a, b, d, and h are fitted values, e is the natural constant, and t is time; the relationship between q and P is as follows: when the alkali metal atom is 85 When Rb, q=(38+52P) 2 +6P 4 ) / (3+10P 2 +3P 4 When the alkali metal atom is 87 Rb or 39 At time K, q = (6 + 2P) 2 ) / (1+P 2 When the alkali metal atom is 41 At time K, q = (6 + P) 2 ) / (1+P 2 When the alkali metal atom is 133 When Cs, q = (22 + 70P) 2 +34P 4 +2P 6 ) / (1+7P 2 +7P 4 +P 6 ).

[0034] The ambient magnetic field is shielded by a magnetic shielding system, and the triaxial residual magnetism is further compensated using a triaxial magnetic field coil. After compensating for the residual magnetism, a B force with an amplitude not exceeding 5 nT is applied. y The alkali metal atom in the alkali metal chamber is one of potassium, rubidium, or cesium, and is filled with buffer gas helium and quenching gas nitrogen. The helium pressure, greater than one atmosphere, slows down the atomic spin. The polarization time of the alkali metal atom to the SERF state is on the order of milliseconds. The chopper modulation frequency is 0.5–2 Hz. When the chopper is on, the atoms are fully polarized; when it is off, the atoms are fully depolarized.

[0035] The X-axis component Px of the alkali metal atomic polarizability P and the photorotation angle θ of the detection light pr The direct proportional relationship is as follows:

[0036]

[0037] Where l is the distance the laser travels through the gas chamber, and r e Let c be the classical electron radius, c be the speed of light, n be the density of alkali metal atoms, and P be the atomic density. x f is the projection of the spin polarization of alkali metal atoms along the x-axis. D2 v is the oscillation intensity of line D2, and v is the frequency of the detection light. D2 Γ is the center frequency of the D2 line of alkali metal atoms. L This represents the pressure broadening value of the D2 line of alkali metal atoms.

[0038] The relationship between the slowing factor and the polarizability oscillation process is as follows:

[0039]

[0040] Where t is time, e is the natural constant, and R p R is the pumping rate. rel Let ω be the relaxation rate, k0 and k1 be the amplitude parameters, q(P) be the slowing factor, and ω be the relaxation rate. y ω is an intermediate quantity. y =γ e ×B y γ e P is the gyromagnetic ratio of alkali metal atoms. x (t) represents the function of Px as a function of time t, where Px is the projection of the spin polarizability of the alkali metal atom onto the x-axis.

[0041] A transient response-based SERF state alkali metal atom polarizability measurement device is used to implement the aforementioned transient response-based SERF state alkali metal atom polarizability measurement method. It includes a pump laser 1 and a detection laser 7. The pump laser 1 is sequentially connected to the pump light incident end of an alkali metal gas cell 17 via a first Glan Taylor prism 2, a quarter-wave plate 3, a chopper 4, and a first beam expander 5. The pump light emitting end of the alkali metal gas cell 17 is sequentially connected to a signal acquisition system 20 via a first photodetector 6 and a multi-channel lock-in amplifier 19. The detection laser 7 is sequentially connected to the detection light incident end of the alkali metal gas cell 17 via a half-wave plate 8, a second beam expander 9, and a second Glan Taylor prism 10. The detection light emitting end of the alkali metal gas cell 17 is sequentially connected to the signal acquisition system 20 via a quarter-wave plate 11, a photoelastic modulator 12, a third Glan Taylor prism 13, a second photodetector 14, and a multi-channel lock-in amplifier 19. The alkali metal gas chamber 17 is surrounded by a non-magnetic electric heating system 16, a triaxial magnetic field coil 18, and a magnetic shielding system 21. The triaxial magnetic field coil 18 is connected to a signal generator 15.

[0042] A method and apparatus for measuring the polarizability of SERF-state alkali metal atoms based on transient response are disclosed. In the direction of pump light propagation, a pump laser 1 outputs laser light, which is then converted into circularly polarized light after passing through a GlanTeller prism 2 and a quarter-wave plate 3. A chopper 4 is used to modulate the intensity of the pump light. A magnetic field B is applied using a triaxial magnetic field coil 18 in a direction perpendicular to both the pump and detection light. yModulated circularly polarized pump light, linearly polarized detection light, and a transverse magnetic field simultaneously act on alkali metal atoms in the gas cell. The detection light, perpendicular to the pump light, is used to detect the transient precession of electron spin in alkali metal atoms under the influence of the modulated pump light and magnetic field. The laser emitted by the detection laser 7 becomes linearly polarized after passing through a half-wave plate 8 and a second Glan-Taylor prism 10. After passing through the alkali metal gas cell 17, the polarization of the light is modulated by a photoelastic modulator 12. The second array detector 14 converts the optical signal of the detection light into an electrical signal, which is then acquired by the signal acquisition system 20. By fitting the transient signal of atomic spin precession, the spin precession slowing factor of the alkali metal atoms is obtained, thereby calculating the electronic polarizability.

[0043] The modulation time of the chopper is greater than the polarization time of the alkali metal atoms to reach the SERF state. In the on state, the atoms are fully polarized, and in the off state, the atoms are fully depolarized.

[0044] To ensure the atomic magnetometer operates in SERF mode, a high-performance magnetic shielding system 21 is used to shield the ambient magnetic field, and a triaxial magnetic field coil 18 is used to further compensate for the triaxial remanence. After compensating for the remanence, a transverse magnetic field B with an amplitude not exceeding 5 nT is applied in a direction perpendicular to the pump and detection beams. y .

[0045] The alkali metal atom in the alkali metal chamber 17 is one of potassium, rubidium, or cesium. It is filled with buffer gas helium and quenching gas nitrogen. By filling it with helium at a pressure greater than 1 atmosphere, the atomic spin is slowed down.

[0046] Detecting the optical rotation angle θ of light pr Projection P along the direction of the detection light for atomic spin polarization x Proportional

[0047]

[0048] Where l is the distance the laser travels through the gas chamber, and r e Let c be the classical atomic radius, c be the speed of light, n be the atomic density of the alkali metal, and P be the atomic radius of the alkali metal. x f represents the projection of the spin polarization of alkali metal atoms along the x-axis. D2 v is the oscillation intensity of line D2, and v is the frequency of the detection light. D2 Γ is the center frequency of the D2 line of alkali metal atoms. L This represents the pressure broadening value of the D2 line of alkali metal atoms.

[0049] The relationship between the slowing factor and the polarizability oscillation process is shown in the following formula:

[0050]

[0051] Where t is time, e is the natural constant, and R p R is the pumping rate. rel ω is the relaxation rate, k0 and k1 are amplitude parameters, and ω y =γ e ×B y q(P) is the slowing factor.

[0052] The photodetector converts the optical signal of the detected light into a voltage signal, and the signal acquisition system 20 then fits the acquired signal y.

[0053] The fitting coefficients g and e are natural constants, and b, d, and h are the fitted values. According to q(p) = g / γ... e ×B y B y γ is the y-axis magnetic field value. e Given the gyromagnetic ratio of alkali metal atoms, the slowing factor q(P) can be calculated, and the fitting formula is:

[0054] y = ae -(bt) [b cos(gt)+d sin(gt)]+h

[0055] The polarizability can be determined by using the relationship between the slowing factor q and the polarizability P based on the type of alkali metal atom.

[0056]

[0057] A method for measuring the electronic polarizability of SERF-state alkali metal atoms based on atomic transient response includes the following steps: In the direction of pump light propagation, a pump laser 1 outputs laser light, which is then converted into circularly polarized light after passing through a GranTeller prism 2 and a quarter-wave plate 3. The chopper 4 is removed, and the pump light and detection light simultaneously illuminate the alkali metal gas cell 17. A triaxial magnetic field coil 17 is used to perform triaxial magnetic compensation on the SERF atomic magnetometer. A voltage is applied to the triaxial magnetic field coil 17 by a control signal generator 15 to generate a magnetic field, which cancels out the external magnetic field, making the output of the photodetector zero, and the alkali metal atoms no longer sense the external magnetic field. The intensity of the pump light is modulated using the chopper 4. A magnetic field B is applied using the triaxial magnetic field coil 18 in a direction perpendicular to both the pump light and the detection light. yModulated circularly polarized pump light, linearly polarized detection light, and a transverse magnetic field simultaneously act on alkali metal atoms in the alkali metal gas cell. The detection light, perpendicular to the pump light, is used to detect the transient precession of electron spin in alkali metal atoms under the influence of the modulated pump light and magnetic field. The laser emitted by the detection light laser 7 becomes linearly polarized after passing through a half-wave plate 8 and a second Glan-Taylor prism 10. After passing through the alkali metal gas cell 17, the polarization of the light is modulated by a photoelastic modulator 12. The second array detector 14 converts the optical signal of the detection light into an electrical signal, which is then acquired by the signal acquisition system 20. By fitting the transient signal of atomic spin precession, the alkali metal atom spin precession slowing factor is obtained, thereby calculating the electronic polarizability.

[0058] A method and apparatus for measuring the electronic polarizability of SERF-state alkali metal atoms based on atomic transient response is disclosed. The modulation time of the chopper is longer than the polarization time of the alkali metal atoms reaching the SERF state. In the on state, the atoms are fully polarized, and in the off state, they are fully depolarized. The polarization time is approximately on the order of milliseconds. Considering the requirement for rapid measurement, the modulation frequency of the chopper 4 is approximately 0.5-2 Hz. The alkali metal atoms in the alkali metal gas chamber 17 are one of potassium, rubidium, or cesium, and are filled with buffer gas helium and quenching gas nitrogen. The helium pressure, greater than one atmosphere, slows down the atomic spin.

[0059] 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 measuring the polarizability of SERF-state alkali metal atoms based on transient response, characterized in that, The process involves sequentially passing the laser output from the pump laser through a Glan Taylor prism and a quarter-wave plate to convert it into circularly polarized light. A chopper is used to modulate the intensity of the pump light from this circularly polarized light. The modulation time of the chopper is longer than the polarization time of the alkali metal atoms reaching the SERF state. A Y-axis magnetic field B is applied using a triaxial magnetic field coil in the Y-axis direction, which is perpendicular to both the Z-axis pump light and the X-axis detection light. y Linearly polarized detection light, Y-axis magnetic field B y The modulated circularly polarized pump light is applied to alkali metal atoms in the alkali metal gas cell. The linearly polarized detection light is used to detect the transient spin precession process of the alkali metal atoms. After passing through the alkali metal gas cell, the linearly polarized detection light passes through a quarter-wave plate, a photoelastic modulator, and a Glan Taylor prism in sequence to reach a photodetector. The optical signal is converted into an electrical signal and input into a signal acquisition system through a multi-channel lock-in amplifier. The transient signal y of the atomic spin precession is fitted in the signal acquisition system to obtain the alkali metal atom spin precession slowing factor q, thereby calculating the SERF state polarizability P of the alkali metal atom based on the transient response. q=g / γ e ×B y Where g is the fitting parameter or fitting coefficient, γ e The gyromagnetic ratio of alkali metal atoms; g is determined from the following fitting formula: , where a, b, d, and h are all fitted values, e is the natural constant, and t is time; The relationship between q and P is as follows: When alkali metal atoms are 85 When Rb, q = (38 + 52P) 2 +6P 4 ) / (3+10P) 2 +3P 4 ); When alkali metal atoms are 87 Rb or 39 When K is reached, q = (6 + 2P) 2 ) / (1+P 2 ); When alkali metal atoms are 41 When K, q = (6 + P) 2 ) / (1+P 2 ); When alkali metal atoms are 133 When Cs, q = (22 + 70P) 2 +34P 4 +2P 6 ) / (1+7P 2 +7P 4 +P 6 ).

2. The method for measuring the polarizability of SERF-state alkali metal atoms based on transient response according to claim 1, characterized in that, The ambient magnetic field is shielded by a magnetic shielding system, and the triaxial residual magnetism is further compensated using a triaxial magnetic field coil. After compensating for the residual magnetism, a B force with an amplitude not exceeding 5 nT is applied. y .

3. The method for measuring the polarizability of SERF-state alkali metal atoms based on transient response according to claim 1, characterized in that, The alkali metal atom in the alkali metal chamber is one of potassium, rubidium, or cesium. It is filled with buffer gas helium and quenching gas nitrogen. The helium pressure is greater than 1 atmosphere, which slows down the spin of the atoms.

4. The method for measuring the polarizability of SERF-state alkali metal atoms based on transient response according to claim 1, characterized in that, The polarization time of the alkali metal atoms to the SERF state is on the order of milliseconds. The modulation frequency of the chopper is 0.5 to 2 Hz. The atoms are fully polarized when the chopper is on and fully depolarized when the chopper is off.

5. The method for measuring the polarizability of SERF-state alkali metal atoms based on transient response according to claim 1, characterized in that, The X-axis component Px of the alkali metal atomic polarizability P and the photorotation angle θ of the detection light pr The direct proportional relationship is as follows: Where l is the distance the laser travels through the gas chamber, and r e Let c be the classical electron radius, c be the speed of light, n be the density of alkali metal atoms, and P be the atomic density. x f is the projection of the spin polarization of alkali metal atoms along the x-axis. D2 v is the oscillation intensity of line D2, and v is the frequency of the detection light. D2 Γ is the center frequency of the D2 line of alkali metal atoms. L This represents the pressure broadening value of the D2 line of alkali metal atoms.

6. The method for measuring the polarizability of SERF-state alkali metal atoms based on transient response according to claim 1, characterized in that, The relationship between the slowing factor and the polarizability oscillation process is as follows: Where t is time, e is the natural constant, and R p R is the pumping rate. rel Let ω be the relaxation rate, k0 and k1 be the amplitude parameters, q(P) be the slowing factor, and ω be the relaxation rate. y ω is an intermediate quantity. y =γ e ×B y γ e The gyromagnetic ratio of alkali metal atoms. The function representing the change of Px with time t, where Px is the projection of the spin polarizability of the alkali metal atom onto the x-axis.

7. A device for measuring the polarizability of SERF-state alkali metal atoms based on transient response, used to implement the method for measuring the polarizability of SERF-state alkali metal atoms based on transient response as described in any one of claims 1-6, characterized in that, The system includes a pump laser and a detection laser. The pump laser is sequentially connected to the pump light incident end of the alkali metal gas cell via a first Glan Taylor prism, a quarter-wave plate, a chopper, and a first beam expander. The pump light emitting end of the alkali metal gas cell is sequentially connected to a signal acquisition system via a first photodetector and a multi-channel lock-in amplifier. The detection laser is sequentially connected to the detection light incident end of the alkali metal gas cell via a half-wave plate, a second beam expander, and a second Glan Taylor prism. The detection light emitting end of the alkali metal gas cell is sequentially connected to the signal acquisition system via a quarter-wave plate, a photoelastic modulator, a third Glan Taylor prism, a second photodetector, and a multi-channel lock-in amplifier.

8. The SERF state alkali metal atom polarizability measurement device based on transient response according to claim 7, characterized in that, The alkali metal gas chamber is surrounded by a non-magnetic electric heating system, a triaxial magnetic field coil, and a magnetic shielding system. The triaxial magnetic field coil is connected to a signal generator.

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