Method for optimizing and stabilizing the detuning detection frequency to suppress spin polarization errors of electrons

Abstract

The application discloses a method for optimizing and stabilizing a mismatch detection frequency for inhibiting an electron spin polarization error, which changes the absorption amount of a pumping light by an atomic cell by changing a detection frequency, and quickly judges a point at which the detection frequency has the least influence on electron spin polarization according to the transmitted light intensity of the pumping light, so as to serve as an optimal working point. When the frequency works at the optimal working point, the polarization rate fluctuation caused by the detection light is the least, the output signal change of an atomic spin inertia measurement or a magnetic field measurement system caused by the detection light fluctuation is the least, and thus the atomic spin inertia measurement or the magnetic field measurement error caused by the detection light fluctuation is inhibited. On this basis, a first derivative of the transmitted light intensity of the pumping light with respect to the detection frequency is obtained by a modulation and demodulation method, the first derivative of the optimal point is taken as a control target, the injection current of a detection laser controller is adjusted, and the purpose of a closed loop of the detection frequency is achieved. The closed loop of the detection frequency far from the optimal working point can further improve the stability of the system.

Description

Technical Field

[0001] This invention relates to the field of suppressing errors in atomic spin inertial measurement or magnetic field measurement caused by electron spin polarization fluctuations, and in particular to a method for optimizing and stabilizing the detuned detection frequency to suppress electron spin polarization errors. This method can be used to suppress errors in the output signal of atomic spin inertial measurement or magnetic field measurement systems caused by fluctuations in detection optical power and frequency. Background Technology

[0002] Atomic spin inertial measurement or magnetic field measurement devices operating under the Spin-Exchange Relaxation-Free (SERF) mechanism are precision measuring instruments with broad application prospects in cutting-edge physics research, magnetocardiography, and high-precision inertial navigation.

[0003] SERF atomic spin inertial measurement or magnetic field measurement devices obtain information about electron spin polarizability through the interaction of light with atoms. Therefore, improving the long-term stability of these devices is closely related to the stability of the atomic spin ensemble polarizability. Currently, many studies focus on the pump system to strive for uniform and stable polarizability of the atomic spin ensemble. However, experiments show that significant fluctuations in electron spin polarizability still exist in inertial measurement or magnetic field measurement devices. Therefore, it is necessary to improve the stability of electron spin polarizability by addressing the detection system, thereby further reducing the error of SERF atomic spin inertial measurement or magnetic field measurement devices. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for optimizing and stabilizing the detuned detection frequency to suppress electron spin polarization errors. By adjusting the detection frequency to its operating point where its impact on electron spin polarization is minimal, and by improving the stability of the detection frequency through detuned frequency closed-loop control technology, the electron spin polarization rate of the SERF atomic spin inertial measurement or magnetic field measurement system becomes insensitive to fluctuations in the detection frequency, thereby suppressing errors caused by fluctuations in the detection light and improving measurement accuracy.

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

[0006] A method for optimizing and stabilizing the detuned detection frequency to suppress electron spin polarization errors is characterized by altering the absorption of pump light by the atomic gas cell by changing the detection light frequency. The optimal operating point is determined by rapidly identifying the point where the detection light frequency has the least impact on electron spin polarization based on the pump light transmission intensity. When the detection frequency operates at this optimal operating point, the polarizability fluctuation caused by the detection light frequency fluctuation is minimized, and the resulting change in the output signal of the atomic spin inertial measurement or magnetic field measurement system is minimized, thereby suppressing the atomic spin inertial measurement or magnetic field measurement errors caused by the detection light fluctuation. The first derivative of the pump light transmission intensity with respect to the detection frequency is obtained through modulation and demodulation. Using the optimal first derivative as the control target, the injection current of the detection laser controller is adjusted to achieve closed-loop detection light frequency control, thereby detuning the detection light frequency to the optimal operating point.

[0007] Includes the following steps:

[0008] Step 1: Start the atomic spin inertial measurement or magnetic field measurement system to bring the atoms to a polarized stable state and perform magnetic field compensation so that the atomic spin inertial measurement or magnetic field measurement system can work normally.

[0009] Step 2: Perform a detection light frequency scan to monitor the electron spin polarization, that is, monitor the pump light transmission intensity, and find the detection frequency with the lowest pump light transmission intensity at a wavelength greater than or equal to 795nm as the operating point. This point is the optimal operating point v0 for reducing the influence of the detection frequency on electron spin polarization.

[0010] Step 3: After the atoms have stabilized at the optimal operating point due to repolarization, perform magnetic field compensation, and then proceed to step 4.

[0011] Step 4: Apply modulation voltage to the laser current controller module, adjust the modulation amplitude and frequency to make it work in a working mode that does not affect other system parameters, and then proceed to step 5;

[0012] Step 5: Amplify the pump light transmission intensity signal and connect it to a lock-in amplifier. Connect the output first-order conductor signal to a PID module. Connect the control voltage output by the PID module to the laser controller to adjust the injection current in real time to complete the real-time adjustment of the detection light frequency.

[0013] The magnetic field compensation in step 1 and / or step 3 adopts the following magnetic field cross-modulation compensation method implemented by a three-dimensional magnetic compensation coil: First, an amplitude A = (a·10) is applied in the Y direction using a Y-direction magnetic compensation coil. 2)A square-wave magnetic field with pT, 0 < a ≤ 10 is applied. The magnetic field in the Z direction is changed so that the difference in the steady-state response of the inertial angular rate measurement system to the modulated magnetic field in the Y direction is 0, that is, the Z magnetic compensation point is found and recorded as Bzc. Then, a square-wave magnetic field with amplitude A and bias Bzc is applied in the Z direction using the Z-direction magnetic compensation coil, and the magnetic field in the Y direction is changed so that the difference in the steady-state response of the inertial angular rate measurement system to the modulated magnetic field in the Z direction is 0, and the Y magnetic compensation point is found. Finally, a square-wave magnetic field with amplitude A and bias (Bzc + A) is applied in the Z direction using the Z-direction magnetic compensation coil, and the magnetic field in the X direction is changed so that the difference in the steady-state response of the inertial angular rate measurement system to the modulated magnetic field in the Z direction is 0, and the X magnetic compensation point is found.

[0014] The method for determining the following modulation parameters is included in step 4: A sinusoidal voltage V = V0 + a V sin(ωt) is input into the detection laser current controller through a signal generator. V0 is the voltage corresponding to the optimal operating point v0. The voltage modulation amplitude aV does not exceed 4V, and the injection current corresponding to 4V is 2mA. The modulation frequency ω is selected as a prime number between 50Hz and 100Hz. t represents time. After this sinusoidal voltage is injected into the laser controller, the resulting current frequency v = v0 + asin(ωt), where a represents the frequency oscillation amplitude. The modulation amplitude and modulation frequency are increased in sequence, and the monitored values of the stable light intensity system and the liquid crystal control voltage are observed, and the maximum value that does not increase the noise of both is selected.

[0015] Step 2 includes: Setting the current detection frequency as the operating point v0 = c / (795nm × 10 -9 ). The wavelength scanning range is 794.5nm to 795.5nm. The temperature of the detection laser controller is adjusted, and at the same time, the detection wavelength is monitored using a wavelength meter. Scanning is performed from 794.5 with a gradient of 0.02nm. During the scanning process, there are two lowest points on both sides of 795nm for the transmitted light intensity of the pump light. The right lowest point is used as the optimal operating point.

[0016] The optimal operating point is 795.1nm ± 0.1nm.

[0017] For the optimal frequency operating point v0, the sensitivity coefficient of the system to the detection frequency is negative on the left side and positive on the right side. The closer it is to the optimal point, the smaller the absolute value of the sensitivity coefficient and the lower the transmitted light intensity of the pump light.

[0018] The atomic spin inertial measurement or magnetic field measurement system includes a detection laser source. The detection laser source outputs frequency-controlled detection light to a stable intensity module. The stable intensity module outputs power-stable detection light to a detection light polarization module. The detection light polarization module outputs approximately ideal linearly polarized light to a gas cell. Power-stable circularly polarized pump light passes through the gas cell and is transmitted through a pump light transmission intensity module. The difference between the first derivative of the transmitted light intensity and a set value is output to a PID module. The PID module controls the detection laser source by adjusting the laser injection current to achieve closed-loop detection light frequency control. The gas cell outputs a gyroscope signal.

[0019] The response model of the pump light transmitted light intensity relative to the detection light is represented by the function f(v) as follows:

[0020]

[0021] Where f(v) represents the pump light transmission intensity as a function of the detection light frequency v, and R1 is an intermediate quantity. It is spin exchange relaxation between electrons. It is the spin exchange relaxation of electrons and nucleons, R sd It is collision-induced relaxation, I pr It measures optical power, s m It is the degree of polarization, σ(v) is σ probe (v) represents the collision cross-section function of the detection light related to the detection light frequency v, n is the atomic number density, l represents the gas cell diameter, e is the natural constant, and A I Let h represent the detection beam, and σ represent Planck's constant. pump Let represent the collision cross section of the pump light, W represent the Lambertian W function, I(0) represent the initial pump light intensity, z represent the current position of the pump light propagation, and exp represent the exponential function.

[0022] The technical effects of this invention are as follows: This invention provides a method for optimizing and stabilizing the detuned detection frequency to suppress electron spin polarization errors. By changing the detection frequency, the absorption of pump light by the atomic gas cell is altered. Based on the transmitted light intensity of the detection light, the point where the detection frequency has the least impact on electron spin polarization is quickly determined as the optimal operating point. When the frequency operates at this optimal operating point, the polarizability fluctuation caused by the detection light is minimized, and the change in the output signal of the atomic spin inertial measurement or magnetic field measurement system caused by the detection light fluctuation is minimized, thereby suppressing the atomic spin inertial measurement or magnetic field measurement errors caused by the detection light fluctuation. Based on this, the first derivative of the pump light transmitted light intensity with respect to the detection frequency is obtained through modulation and demodulation methods. Using the optimal first derivative as the control target, the injection current of the detection laser controller is adjusted to achieve the purpose of closed-loop detection frequency control. Closed-loop detection frequency detuning to the optimal operating point further improves the stability of the system.

[0023] The advantages of this invention over existing technologies are as follows: Research has revealed that the electron spin polarization, represented by the pump light transmission intensity of an atomic spin inertial measurement or magnetic field measurement device, exhibits a definite relationship with increasing detection light frequency, displaying a W-shaped curve. When this first derivative is zero, it represents the lowest point of the pump light transmission intensity, signifying the point where the detection frequency has the least impact on the electron spin polarization of inertial or magnetic field measurements, and is also the point where the output signal of atomic spin inertial or magnetic field measurements is most stable. This point is referred to as the optimal operating point v0 of this method. The method's judgment is based on the sensitivity coefficient and the amplitude of the pump light transmission intensity, without requiring knowledge of the specific electron spin polarization. Therefore, it is simple to operate and easy to implement, enabling the rapid finding of the optimal operating point of the detection frequency without adding new devices. Furthermore, the zero point of the first derivative of this curve is only related to the gas chamber pressure and is independent of other parameters, providing the possibility for far-detuned frequency stabilization of the detection frequency. The detuned detection frequency optimization and stabilization method proposed in this paper uses the first derivative of the pump light transmission intensity as the control target for closed-loop detection light frequency control. By simply linking the pumped transmitted light intensity, integrated circuit board, signal generator, and laser controller, a frequency-stabilized target based on gas cell light intensity absorption can be achieved. This method facilitates the miniaturization of inertial measurement or magnetic field measurement devices, significantly improves the stability of the detection frequency, reduces electron spin polarization errors, and enhances the accuracy and long-term stability of atomic spin inertial or magnetic field measurements. Attached Figure Description

[0024] Figure 1 This is a flowchart of the detuning detection frequency optimization and stabilization method for suppressing electron spin polarization error according to the present invention. Figure 1 The process includes step 1, starting the system and reaching a stable state; and step 2, changing the detection frequency and monitoring the pump transmitted light intensity.

[0025] Step 3: Is the current pump transmitted light intensity at its lowest value? If not, return to step 2; if yes, proceed to step 4.

[0026] Step 4: The system returns to a stable state and the magnetic field is replenished; Step 5: The frequency closed-loop working mode is started at the optimal operating point.

[0027] Figure 2 This is a schematic diagram of the atomic spin inertial measurement or magnetic field measurement system involved in implementing the detuning detection frequency optimization and stabilization method for suppressing electron spin polarization error of the present invention. Figure 2The system includes a detection laser source, which outputs frequency-controlled detection light to a stable intensity module. The stable intensity module outputs power-stable detection light to a detection light polarization module. The detection light polarization module outputs approximately ideal linearly polarized light to a gas cell. Power-stable circularly polarized pump light passes through the gas cell and is transmitted through a pump light transmission intensity module. The difference between the first derivative of the transmitted light intensity and a set value is output to a PID module (Proportional Integral Derivative). The PID module controls the detection laser source by adjusting the laser injection current (achieving closed-loop detection light frequency control). The gas cell outputs a gyroscope signal. Detailed Implementation

[0028] The following is in conjunction with the attached diagram ( Figures 1-2 The invention will be described in the following sections and examples.

[0029] Figure 1 This is a flowchart of the detuning detection frequency optimization and stabilization method for suppressing electron spin polarization error according to the present invention. Figure 2 This is a schematic diagram of the atomic spin inertial measurement or magnetic field measurement system involved in implementing the detuning detection frequency optimization and stabilization method for suppressing electron spin polarization errors of the present invention. (Reference) Figures 1 to 2 As shown, the method for optimizing and stabilizing the detuned detection frequency to suppress electron spin polarization error involves changing the detection light frequency to alter the absorption of pump light by the atomic gas cell. The optimal operating point is determined by rapidly identifying the detection light frequency that minimizes the impact on electron spin polarization based on the pump light transmission intensity. When the frequency operates at this optimal operating point, the polarizability fluctuation caused by the detection light is minimized, and the output signal change of the atomic spin inertial measurement or magnetic field measurement system caused by the detection light fluctuation is minimized, thus suppressing the atomic spin inertial measurement or magnetic field measurement error caused by the detection light fluctuation. The first derivative of the pump light transmission intensity with respect to the detection frequency is obtained through modulation and demodulation. Using the optimal first derivative as the control target, the injection current of the detection laser controller is adjusted to achieve closed-loop detection light frequency control, thereby detuning the detection light frequency to the optimal operating point.

[0030] It includes the following steps: Step 1, start the atomic spin inertia measurement or magnetic field measurement system, make the atoms reach a polarized and stable state, and perform magnetic field compensation to enable the atomic spin inertia measurement or magnetic field measurement system to work properly; Step 2, perform detection light frequency scanning, monitor the electron spin polarization rate, that is, monitor the transmitted light intensity of the pumping light, and find the detection frequency with a wavelength greater than or equal to 795 nm and the lowest transmitted light intensity of the pumping light as the working point, and this point is used as the optimal working point v0 to reduce the influence of the detection frequency on the electron spin polarization; Step 3, after the atoms are re-polarized and stabilized at the optimal working point, perform magnetic field compensation, and then enter Step 4; Step 4, apply a modulation voltage to the detection laser current controller module, adjust the modulation amplitude and frequency to make it work in a working mode that does not affect other system parameters, and then enter Step 5; Step 5, amplify the transmitted light intensity signal of the pumping light and connect it to a lock-in amplifier, connect the output first derivative signal to a PID module, and connect the control voltage output by the PID module to the laser controller to adjust the injection current in real time to complete the real-time adjustment of the detection light frequency.

[0031] The magnetic field compensation in Step 1 and / or Step 3 adopts the following magnetic field cross-modulation compensation method realized by three-dimensional magnetic compensation coils: First, use the Y-direction magnetic compensation coil to apply a square-wave magnetic field with an amplitude A=(a·10 2 ) pT, 0 < a ≤ 10) in the Y direction to change the Z-direction magnetic field, so that the steady-state response difference of the inertial angular rate measurement system to the Y-direction modulated magnetic field is 0, that is, find the Z magnetic field compensation point, recorded as Bzc; then, use the Z-direction magnetic compensation coil to apply a square-wave magnetic field with an amplitude A and a bias of Bzc in the Z direction to change the Y-direction magnetic field, so that the steady-state response difference of the inertial angular rate measurement system to the Z-direction modulated magnetic field is 0, and find the Y magnetic field compensation point; finally, use the Z-direction magnetic compensation coil to apply a square-wave magnetic field with an amplitude A and a bias of (Bzc + A) in the Z direction to change the X-direction magnetic field, so that the steady-state response difference of the inertial angular rate measurement system to the Z-direction modulated magnetic field is 0, and find the X magnetic field compensation point. The modulation parameter determination method in Step 4 includes: input a sinusoidal voltage V = V0 + a V sin(ωt) into the detection laser current controller through a signal generator, V0 is the voltage corresponding to the optimal working point v0, the voltage modulation amplitude a V does not exceed 4V, 4V corresponds to an injection current of 2 mA, the modulation frequency ω is selected as a prime number between 50 Hz and 100 Hz, t represents time, after this sinusoidal voltage is injected into the laser controller, the generated current frequency v = v0 + asin(ωt), a represents the frequency oscillation amplitude, increase the modulation amplitude and modulation frequency in turn, observe the monitored value of the stable light intensity system and the liquid crystal control voltage, and select the maximum value that does not increase the noise of the two.

[0032] Step 2 includes: setting the current detection frequency as the operating point v0 = c / (795nm × 10). -9 The wavelength scanning range is 794.5nm to 795.5nm. The temperature of the detection laser controller is adjusted, and the detection wavelength is monitored simultaneously with a wavelength meter. Scanning is performed from 794.5nm with a gradient of 0.02nm. During the scanning process, the transmitted light intensity of the pump light has two minimum points on both sides of 795nm. The right minimum point is taken as the optimal operating point. The optimal operating point is 795.1nm ± 0.1nm. For the optimal frequency operating point v0, the sensitivity coefficient of the system to the detection frequency is negative on the left and positive on the right. The closer to the optimal point, the smaller the absolute value of the sensitivity coefficient and the lower the transmitted light intensity of the pump light. The atomic spin inertial measurement or magnetic field measurement system includes a detection laser source. The detection laser source outputs frequency-controlled detection light to a stable intensity module. The stable intensity module outputs power-stable detection light to a detection light polarization module. The detection light polarization module outputs approximately ideal linearly polarized light to a gas cell. Power-stable circularly polarized pump light passes through the gas cell and is transmitted through a pump light transmission intensity module. The difference between the first derivative of the transmitted light intensity and a set value is output to a PID module. The PID module controls the detection laser source by adjusting the laser injection current to achieve closed-loop detection light frequency control. The gas cell outputs a gyroscope signal.

[0033] The response model of the pump light transmitted light intensity relative to the detection light is represented by the function f(v) as follows:

[0034]

[0035] Where f(v) represents the pump light transmission intensity as a function of the detection light frequency v, and R1 is an intermediate quantity. It is spin exchange relaxation between electrons. It is the spin exchange relaxation of electrons and nucleons, R sd It is collision-induced relaxation, I pr It measures optical power, s m It is the degree of polarization, σ(v) is σ probe (v) represents the collision cross-section function of the detection light related to the detection light frequency v, n is the atomic number density, l represents the gas cell diameter, e is the natural constant, and A I Let h represent the detection beam, and σ represent Planck's constant. pump Let represent the collision cross section of the pump light, W represent the Lambertian W function, I(0) represent the initial pump light intensity, z represent the current position of the pump light propagation, and exp represent the exponential function.

[0036] The technical principle of this invention is as follows:

[0037] The attenuation of optical power of circularly polarized light propagating in an alkali metal gas cell in an atomic spin inertial measurement or magnetic field measurement system can be expressed as follows:

[0038]

[0039] The meanings of each parameter in the formula are as follows:

[0040] I(z) is the pump light intensity in the direction of pump light propagation, i.e., the z-direction, where n is the atomic number density and σ pump Let P(z) be the absorption cross section of the photon, and P(z) be the polarizability of the alkali metal atom at coordinate z.

[0041]

[0042] R op R is the pumping rate of the pump light for alkali metals, which is a function related to I(z). rel This represents the electronic relaxation related terms, which are composed of various relaxation terms, such as inter-electron spin exchange relaxation. Spin exchange relaxation of electrons and nuclei Collision damage relaxation R sd The pump rate R of the detection light m etc.R rel Record It can also be represented as R rel =R1+R m . It can be represented as a transcendental equation and solved using the Lambert-W function, expressed as:

[0043]

[0044] I(0) represents the initial pump light intensity, σ pump Let I(z) represent the collision cross-section of the pump beam, and z represent the current propagation position of the pump beam. It is worth noting that in the expression for I(z), the term related to the detection part is R. rel It includes the pump rate R of the detection light. m In a study at Princeton University, R m It can be expressed in the following form. It is a power related to the detection power I. pr Frequency v and degree of polarization s m Related terms. Among them, σ probe (ν) indicates that the collision cross section of the detection light is a function related to the frequency of the detection light, A I The detector beam is represented by h, Planck's constant is represented by l, the cell diameter is represented by Γ, the pressure broadening is represented by c, and the speed of light is represented by r. e Represents the electron radius, ν D1represents the frequency corresponding to the D1 linear transition of the Rb atom, and e represents the exponential function. In our atomic spin inertial measurement or magnetic field measurement system, since the detection power is closed-loop, linearly polarized light is used for detection. m It is a relatively stable value, so this method mainly considers the effect of the detection light frequency on the longitudinal polarizability.

[0045]

[0046] R m Substituting into I(z), we can obtain the response model of the pump light transmitted light intensity, i.e., the longitudinal polarizability, relative to the detection light, denoted as the function f(v).

[0047]

[0048] when When the detection frequency changes, the change in electron spin polarization in the atomic spin inertial measurement or magnetic field measurement system is minimal; that is, the system experiences the least fluctuation in signal output due to frequency fluctuations, resulting in the most stable system. When the detection frequency is adjusted to... In this way, errors in atomic spin inertial measurement or magnetic field measurement caused by fluctuations in the detection frequency can be suppressed.

[0049] Based on this, according to the expression for f(v), a closed-loop frequency closure for far-detuned detection can also be performed simultaneously. By slightly modulating the laser frequency, the resulting frequency is...

[0050] y = y0 + asin(ωt)

[0051] Where ν0 is the optimal operating point, a represents the frequency oscillation amplitude, and ω is the modulation frequency. Therefore, ignoring the effect of modulation on laser intensity, if a small modulation is applied to the probe frequency, the resulting frequency can be expressed as I = f(v0 + sin(ωt)).

[0052] After Taylor expansion, it can become

[0053]

[0054] Where f 1 (ν0) represents the first derivative at v0. This signal is demodulated at second harmonics, and the DC component is extracted to obtain the first derivative of f. The first derivative signal is then fed back to the PID controller to adjust the laser injection current and stabilize the laser frequency.

[0055] A method for optimizing and stabilizing the detuned detection frequency to suppress electron spin polarization errors is proposed. This method alters the absorption of pump light by the atomic gas cell by changing the detection frequency. The optimal operating point is determined by rapidly identifying the detection frequency that minimizes the impact on electron spin polarization based on the transmitted light intensity. When the frequency operates at this optimal point, the polarizability fluctuation caused by the detection light is minimized, and the output signal change of the atomic spin inertial measurement or magnetic field measurement system caused by the detection light fluctuation is also minimized, thus suppressing the atomic spin inertial measurement or magnetic field measurement errors caused by the detection light fluctuation. Based on this, the first derivative of the pump light transmitted light intensity with respect to the detection frequency is obtained through modulation and demodulation. Using the optimal first derivative as the control target, the injection current of the detection laser controller is adjusted to achieve closed-loop detection frequency control. Detuning the detection frequency to the optimal operating point further improves the system stability.

[0056] like Figure 1-2 As shown, the flowchart of the detuning detection frequency optimization and stabilization method for suppressing electron spin polarization error and the closed-loop system of the detection frequency and detuning frequency of the present invention are respectively illustrated.

[0057] The specific implementation steps are as follows:

[0058] (1) Start the atomic spin inertial measurement or magnetic field measurement device to make the atom reach a polarized stable state and perform magnetic field compensation so that the atomic spin inertial measurement or magnetic field measurement system works normally.

[0059] The pump laser provides pump light with a center frequency at the D1 harmonic transition of the K atom, and this pump light 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 chamber. Then, the power is stabilized by a liquid crystal module, and finally, it is polarized into fully circularly polarized light by an optical isolation module before entering the gas chamber. After absorption by the gas chamber, the remaining component of the pump light is received and output by a photodetector placed behind a shielded container. The detection laser provides detection light with a red-edge detuned D1 transition of Rb, and its spot diameter is 1 mm. The detection light path has the same optical power stabilization module as the pump light path. Furthermore, before entering the gas chamber, it is polarized using a Glan-Taylor prism to ensure the linearity of the detection light. A balanced polarimeter at the end enables high-sensitivity measurements of the SERF common magnetometer output. Additionally, an oven surrounding the gas chamber provides the necessary high temperature. The outer layer of magnetic shielding material provides passive magnetic shielding, while the inner layer of three-cycle magnetic compensation coils provides active magnetic compensation, in order to provide an extremely weak magnetic environment for the atomic SERF state.

[0060] (2) Perform a detection light frequency scan to monitor the electron spin polarization, i.e. the pump light transmission intensity. Find the detection frequency with the lowest pump light transmission intensity above 795nm as the working point v0. This point is the optimal working point for the detection frequency to affect the electron spin polarization.

[0061] The current detection frequency is used as the operating point: v0 = c / (795nm × 10). -9 The wavelength scanning range is 794.5 nm to 795.5 nm. The temperature of the detection laser controller is adjusted, and the detection wavelength is monitored simultaneously with a wavelength meter. The scan starts from 794.5 nm with a gradient of 0.02 nm. During this process, the transmitted light intensity of the pump light has two minimum points on both sides of 795 nm. This method uses the right minimum point as the optimal operating point, which is usually around 795.1 nm.

[0062] (3) After the atoms are repolarized and stabilized at the optimal operating point, magnetic field compensation is performed, and then the frequency stabilization step (4) is entered.

[0063] (4) Apply modulation voltage to the laser current controller module, adjust the modulation amplitude and frequency to make it work in a working mode that does not affect other system parameters, and then enter the closed loop step;

[0064] A sinusoidal voltage V = V0 + a is input to the current controller of the detection laser via a signal generator. V sin(ωt), modulation amplitude not exceeding 4V (corresponding to an injection current of 2mA), and modulation frequency selected as a prime number between 50Hz and 100Hz. Increasing the modulation amplitude and frequency sequentially, observing the monitoring values ​​of the stable light intensity system and the liquid crystal control voltage, and selecting the maximum value that does not increase the noise of either.

[0065] (5) The pump light transmission intensity signal is amplified and connected to the lock-in amplifier. The first-order lead signal output is connected to the PID module. The control voltage output by the PID module is connected to the laser controller to adjust the injection current in real time to complete the real-time adjustment of the detection frequency.

[0066] At the optimal operating point v0, the output signal change of the atomic spin inertial measurement or magnetic field measurement system caused by the detection of light fluctuations is minimized, thereby suppressing or significantly reducing the atomic spin inertial measurement / magnetic field measurement error caused by the detection of light fluctuations.

[0067] A method for optimizing and stabilizing the detuned detection frequency to suppress electron spin polarization errors is proposed. This method adjusts the detection frequency to alter the absorption of detection light by the alkali metal within the gas chamber, thereby reducing the pump effect of the detection light and suppressing electron spin polarization errors in inertial or magnetic field measurements caused by detection light fluctuations. Ultimately, this reduces the error in atomic spin inertial or magnetic field measurements. Based on this, a closed-loop technique for far-detuned frequency is proposed according to the relationship between the pump light transmission intensity and the detection frequency. By adjusting the injection current of the detection laser tube in real time, the pump light transmission intensity is stabilized at its first derivative zero relative to the detection frequency, i.e., the point where the detection frequency has the least impact on electron spin polarization.

[0068] 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 optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error, characterized in that, By changing the frequency of the detection light, the absorption of pump light by the atomic gas cell is altered. Based on the intensity of the transmitted pump light, the point where the frequency of the detection light has the least impact on electron spin polarization is quickly determined and taken as the optimal operating point. When the frequency operates at this optimal operating point, the polarizability fluctuation caused by the detection light is minimized, and the change in the output signal of the atomic spin inertial measurement or magnetic field measurement system caused by the fluctuation of the detection light is minimized, thereby suppressing the error in atomic spin inertial measurement or magnetic field measurement caused by the fluctuation of the detection light. The first derivative of the pump light transmission intensity with respect to the detection frequency is obtained by modulation and demodulation method. The optimal first derivative is used as the control target. The injection current of the detection laser controller is adjusted to realize the detection light frequency closed loop and the detection light frequency is detuned to the optimal operating point. Includes the following steps: Step 1: Start the atomic spin inertial measurement or magnetic field measurement system to bring the atoms to a polarized stable state and perform magnetic field compensation so that the atomic spin inertial measurement or magnetic field measurement system can work normally. Step 2: Perform a detection light frequency scan to monitor the electron spin polarization, i.e., monitor the pump light transmission intensity. Find the detection frequency with a wavelength ≥795 nm and the lowest pump light transmission intensity as the operating point. This point is considered the optimal operating point for reducing the influence of the detection frequency on electron spin polarization. ; Step 3: After waiting for the atoms to repolarize and stabilize at the optimal operating point, perform magnetic field compensation, and then proceed to step 4. Step 4: Apply modulation voltage to the laser current controller module, adjust the modulation amplitude and frequency to make it work in a working mode that does not affect other system parameters, and then proceed to step 5; Step 5: Amplify the pump light transmission intensity signal and connect it to a lock-in amplifier. Connect the output first-order conduction signal to a PID module. Connect the control voltage output by the PID module to the laser controller to adjust the injection current in real time to complete the real-time adjustment of the detection light frequency.

2. The method for optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error according to claim 1, characterized in that, The magnetic field compensation in the above step 1 and / or step 3 adopts the following magnetic field cross-modulation compensation method realized by three-dimensional magnetic compensation coils: First, use the Y-direction magnetic compensation coil to apply a square-wave magnetic field with an amplitude A = (a • 10 2 ), 0 < a ≤ 10) in the Y direction to change the magnetic field in the Z direction, so that the steady-state response difference of the inertial angular rate measurement system to the modulated magnetic field in the Y direction is 0, that is, find the Z magnetic field compensation point and record it as Bzc; Then, use the Z-direction magnetic compensation coil to apply a square-wave magnetic field with an amplitude A and a bias of Bzc in the Z direction to change the magnetic field in the Y direction, so that the steady-state response difference of the inertial angular rate measurement system to the modulated magnetic field in the Z direction is 0, and find the Y magnetic field compensation point; Finally, use the Z-direction magnetic compensation coil to apply a square-wave magnetic field with an amplitude A and a bias of (Bzc + A) in the Z direction to change the magnetic field in the X direction, so that the steady-state response difference of the inertial angular rate measurement system to the modulated magnetic field in the Z direction is 0, and find the X magnetic field compensation point.

3. The method for optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error according to claim 1, characterized in that, Step 4 includes the following modulation parameter determination method: inputting a sinusoidal voltage to the current controller of the detection laser through a signal generator. V0 is the optimal operating point. The corresponding voltage, voltage modulation amplitude a V The voltage should not exceed 4V, which corresponds to an injection current of 2mA. The modulation frequency ω is selected as a prime number between 50Hz and 100Hz, and t represents time. This sinusoidal voltage, after being injected into the laser controller, generates the current frequency. 'a' represents the frequency oscillation amplitude. By increasing the modulation amplitude and modulation frequency in sequence, we observe the monitoring value of the stable light intensity system and the liquid crystal control voltage, and select the maximum value that does not increase the noise of either.

4. The method for optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error according to claim 1, characterized in that, Step 2 includes: setting the current detection frequency as the operating point. The wavelength scanning range is 794.5 nm to 795.5 nm. The temperature of the detection laser controller is adjusted, and the detection wavelength is monitored with a wavelength meter at the same time. The scanning is performed from 794.5 nm with a gradient of 0.02 nm. During the scanning process, there are two minimum points of the transmitted light intensity of the pump light on the left and right sides of 795 nm. The right minimum point is taken as the optimal working point.

5. The method for optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error according to claim 4, characterized in that, The wavelength corresponding to the optimal operating point is 795.1 nm ± 0.1 nm.

6. The method for optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error according to claim 1, characterized in that, For the optimal operating frequency The sensitivity coefficient of the system on the left is negative for the detection frequency, while that on the right is positive. The closer to the optimal point, the smaller the absolute value of the sensitivity coefficient and the lower the intensity of the pump light transmitted.

7. The method for optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error according to claim 1, characterized in that, The atomic spin inertial measurement or magnetic field measurement system includes a detection laser source. The detection laser source outputs frequency-controlled detection light to a stable intensity module. The stable intensity module outputs power-stable detection light to a detection light polarization module. The detection light polarization module outputs approximately ideal linearly polarized light to a gas cell. Power-stable circularly polarized pump light passes through the gas cell and is transmitted through a pump light transmission intensity module. The difference between the first derivative of the transmitted light intensity and a set value is output to a PID module. The PID module controls the detection laser source by adjusting the laser injection current to achieve closed-loop detection light frequency control. The gas cell outputs a gyroscope signal.

8. The method for optimizing and stabilizing the detuning detection frequency to suppress electron spin polarization error according to claim 1, characterized in that, The response model of the pump light transmitted light intensity relative to the detection light is represented by the function f(v) as follows: ， Where f(v) represents the transmitted light intensity of the pump light as a function of the detection light frequency v, and R1 is an intermediate quantity, R1= + + , It is spin exchange relaxation between electrons. It is the spin exchange relaxation of electrons and nucleons. It is collision-induced relaxation, I pr It measures optical power, s m It is the degree of polarization, σ(v) This represents the collision cross-section function of the detection light related to the detection light frequency v, where n is the atomic number density, l is the gas cell diameter, e is the natural constant, and A I Let h represent the detection beam, and σ represent Planck's constant. pump Let represent the collision cross section of the pump light, W represent the Lambertian W function, I(0) represent the initial pump light intensity, z represent the current position of the pump light propagation, and exp represent the exponential function.

Images