Atomic polarization error suppression method based on twin beam splitting system

Abstract

The invention discloses an atomic polarization error suppression method based on a twin beam splitting system. According to the method, an atomic polarization error of an atomic spin inertia measurement device is taken as a research object, a PID controller is designed aiming at the problem that atoms are easily interfered by unknown noise of an external environment due to pumping optical power density, liquid crystal voltage is controlled through the feedback of the atomic polarization error, the pumping optical power density is further controlled, a twin optical path is introduced, and a twin optical path is introduced. Through the consistency of the splitting ratios of the twin optical path and the main optical path, the suppression of the splitting ratio drift and the real-time acquisition of atomic polarization are realized, and the atomic polarization error caused by the splitting ratio drift is effectively suppressed. The method is used for suppressing the polarization error of the air chamber of the atomic spin inertial measurement device, has the characteristics of good suppression effect, high control precision, strong anti-interference performance and convenience in engineering realization, and is suitable for the field of air chamber polarization control of the atomic spin inertial measurement device.

Description

Technical Field

[0001] The present invention relates to a method for suppressing atomic polarization error based on a twin spectroscopic system, which is applicable to the technical field of polarization error control of atomic inertial measurement devices. Background Art

[0002] Inertial navigation technology senses the motion information of an object through an inertial measurement unit (IMU). Based on the detection of acceleration and angular velocity, it can continuously calculate the position, velocity, and attitude of the carrier. This technology is widely used in many fields such as aerospace and ship navigation. In an inertial navigation system, a gyroscope is the core component for measuring angular velocity and plays a crucial role. As a high-precision sensor, an atomic spin gyroscope measures angular velocity based on the principle of spin-exchange relaxation-free and utilizes the quantum properties of atomic spins. It has the advantages of miniaturization, high sensitivity, and strong stability, and is therefore regarded as an important development direction for the next generation of inertial measurement technology.

[0003] Atomic polarization based on laser pumping is the core step of atomic spin inertial measurement. The power density fluctuation of the laser will have a significant impact on indicators such as the atomic polarization uniformity and stability in the gas chamber of the inertial measurement device. Currently, the control of the pumping laser power density is generally carried out by adding a spectroscopic prism in the incident optical path, collecting the optical power density of the reflected light to indirectly reflect the actual pumping optical power density, and applying control. However, this method ignores the influence of environmental factors on the drift of the spectroscopic ratio, resulting in the actual object of control being the power density of the reflected light. Due to the drift of the spectroscopic ratio, the power density of the incident light is not actually controlled in a steady state. Since the incident light, that is, the pumping optical power density, is unstable, it leads to errors in atomic polarization. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, and in view of the problem that atomic polarization in an atomic spin inertial measurement device is easily affected by the power density fluctuation of the pumping laser, a method for suppressing atomic polarization error based on a twin spectroscopic system is proposed to achieve high-precision control of the pumping laser power density.

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

[0006] A method for suppressing atomic polarization error based on a twin spectroscopic system, characterized by comprising the following steps:

[0007] Step 1: Set up a twin beam splitting system on the pumping light incident side of the glass atomic gas cell. The twin beam splitting system splits the main path light into a first transmitted main path light and a first reflected branch light, splits the first reflected branch light into a second transmitted branch light and a second reflected branch light, and splits the first transmitted main path light into a second transmitted main path light and a third reflected branch light. The second transmitted main path light enters the glass atomic gas cell through a quarter-wave plate. The second transmitted branch light, the second reflected branch light, and the third reflected branch light are respectively collected by a photoelectric control circuit board. Connect the photoelectric control circuit board to a host computer and set the expected atomic polarizability through the host computer.

[0008] Step 2: The host computer calculates the reflected light power density from the main optical path, as well as the transmitted light power density and the reflected light power density of the twin optical path system.

[0009] Step 3: Calculate the beam splitting ratio of the twin optical path system, calculate the drift factor relative to the ideal beam splitting ratio after time smoothing, and update it to the main optical path. Calculate the actual transmitted light power density of the main optical path and the real-time value of the atomic polarizability.

[0010] Step 4: Compare the calculated real-time value of the atomic polarizability with the set expected value of the atomic polarizability to obtain an error amount.

[0011] Step 5: According to the error amount, the host computer outputs a control signal to the liquid crystal variable phase retarder on the pumping optical path through a PID controller to control the light power density of the pumping light, thereby suppressing the atomic polarization error.

[0012] Step 1 includes: adjusting the power density and frequency of the pumping light and the detection light, and applying excitation to the three-axis magnetic field coil for compensation. Heat the glass atomic gas cell to 175 °C through an oven device to make the atomic spin gyroscope reach an approximate working state. The glass atomic gas cell is located inside the oven device, and the oven device is located inside the three-axis magnetic field coil.

[0013] The twin beam splitting system in Step 1 includes a first depolarizing beam splitting prism and a second depolarizing beam splitting prism distributed in sequence along the pumping optical path. The transmission side of the second depolarizing beam splitting prism is connected to the quarter-wave plate, and the reflection side is connected to the photoelectric control circuit board through a first photodetector. The input side of the first depolarizing beam splitting prism is connected to a distributed feedback laser through a half-wave plate, a second polarizing beam splitting prism, a liquid crystal variable phase retarder, and a first polarizing beam splitting prism in sequence. The reflection side of the first depolarizing beam splitting prism is connected to the input side of a third depolarizing beam splitting prism. The transmission side of the third depolarizing beam splitting prism is connected to the photoelectric control circuit board through a second photodetector, and the reflection side of the third depolarizing beam splitting prism is connected to the photoelectric control circuit board through a third photodetector. The liquid crystal variable phase retarder is connected to the host computer.

[0014] The control signal in step 5 is the output signal obtained by multiplying the control voltage by the high-frequency square wave signal. After power amplification, the output signal is loaded onto the liquid crystal variable phase retarder.

[0015] The PID controller in step 5 is implemented based on the positional discrete PID controller.

[0016] Step 5 includes the following expressions:

[0017]

[0018] where u(k) is the control voltage at the k-th moment in the control signal, k is the sequence number, K p is the proportional gain, e(k) is the error amount at the k-th moment, K i is the integral gain, Δt is the preset step size, K d is the derivative gain. In actual use, the preset step size Δt is set, and e(k - 1) is the error amount at the (k - 1)-th moment.

[0019] Step 3 includes the following expressions:

[0020]

[0021]

[0022] where is the actual splitting ratio of the second depolarizing beam splitter at the k-th moment, is the actual splitting ratio of the third depolarizing beam splitter at the k-th moment, is the optical power density of the reflected light in the main optical path collected by the first photodetector at the k-th moment, is the set optical power density of the transmitted light, is the set optical power density of the reflected light, ξ2 is the set splitting ratio of the third depolarizing beam splitter, and δ(k) is the splitting ratio drift factor of the twin optical paths at the k-th moment.

[0023] Step 2 includes the following expressions:

[0024]

[0025] where is the actual atomic polarizability at the k-th moment, ξ1 is the set splitting ratio of the second depolarizing beam splitter, R rel is the relaxation rate.

[0026] The advantages of the present invention compared with the prior art are as follows:

[0027] (1) A method for suppressing atomic polarization error based on a twin spectroscopic system proposed by the present invention is designed based on the principle of ensuring that the actual atomic polarization is close to the desired atomic polarization, and can effectively suppress the laser power density fluctuation caused by unknown noise in the external environment and the resulting atomic polarization fluctuation.

[0028] (2) A method for suppressing atomic polarization error based on a twin spectroscopic system proposed by the present invention has the advantage that it takes into account the factor of the spectroscopic characteristics of the PBS spectroscopic prism drifting with time, and can calculate the actual pumping light power density incident into the gas cell, rather than relying on the power density of the reflected light to indirectly reflect its value. And the actual pumping light power density incident into the gas cell is related to atomic polarization, which increases the accuracy of atomic polarization control. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of the twin spectroscopic system involved in implementing the method for suppressing atomic polarization error based on a twin spectroscopic system of the present invention.

[0030] Figure 2 It is a schematic flow diagram of the method for suppressing atomic polarization error based on a twin spectroscopic system of the present invention. Figure 2 It includes Step 1, the host computer sets the desired atomic polarization rate of the main path; Step 2, collect the power density of the reflected light on the main optical path at time k, where k is the time sequence number, collect the transmitted light and reflected light power densities of the twin optical path at time k, and calculate the splitting ratio and splitting drift factor at time k; Step 3, calculate the actual atomic polarization rate at time k; Step 4, compare with the desired atomic polarization rate to obtain the error amount; Step 5, calculate the control quantity liquid crystal control voltage u(k) through a PID controller, then let k = k + 1, and return to Step 2. The PID controller is the proportional-integral-derivative controller.

[0031] Figure 3 It is a schematic flow diagram of the controller parameter update involved in implementing the method for suppressing atomic polarization error based on a twin spectroscopic system of the present invention. Figure 3 It includes Step 1, set the expected value of the atomic polarization rate; Step 2, collect and calculate the actual atomic polarization rate; Step 3, subtract the expected value to obtain the error e(k); Step 4, substitute e(k) into the positional PID controller; Step 5, output u(k), then let k = k + 1, and return to Step 2.

[0032] The descriptions of the reference numerals are as follows: 1 - Distributed Feedback Laser (DFB); 2 - Polarizing Beamsplitter (PBS); 3 - Liquid Crystal Variable Retarder (LCVR); 4 - Second Polarizing Beamsplitter; 5 - Half-wave plate; 6 - Non-polarizing Beamsplitter (NPBS); 7 - Second Non-polarizing Beamsplitter (NPBS1); 8 - Quarter-wave plate; 9 - First Photoelectric Detector (PD1); 10 - Third Non-polarizing Beamsplitter (NPBS2); 11 - Second Photoelectric Detector (PD2); 12 - Third Photoelectric Detector (PD3); 13 - Triaxial magnetic field coil; 14 - Glass atomic gas cell; 15 - Oven device; 16 - Optically controlled circuit board; 17 - Host computer. Detailed implementation manners

[0033] The present invention will be described below in conjunction with the accompanying drawings ( Figures 1 - 3 ).) and embodiments.

[0034] Figure 1 is a schematic structural diagram of a twin beam splitting system involved in implementing an atomic polarization error suppression method based on a twin beam splitting system according to the present invention. Figure 2 is a schematic flow diagram of an atomic polarization error suppression method based on a twin beam splitting system according to the present invention. Figure 3 is a schematic flow diagram of the controller parameter update involved in implementing an atomic polarization error suppression method based on a twin beam splitting system according to the present invention. Refer to Figures 1 to 3As shown, an atomic polarization error suppression method based on a twin spectroscopic system includes the following steps: Step 1, a twin spectroscopic system is arranged on the pumping light incident side of a glass atomic gas cell. The twin spectroscopic system splits the main path light into a first transmitted main path light and a first reflected branch light, splits the first reflected branch light into a second transmitted branch light and a second reflected branch light, and splits the first transmitted main path light into a second transmitted main path light and a third reflected branch light. The second transmitted main path light enters the glass atomic gas cell through a quarter-wave plate. The second transmitted branch light, the second reflected branch light, and the third reflected branch light are respectively collected by a light control circuit board. The light control circuit board is connected to a host computer, and the expected atomic polarization rate is set through the host computer. Step 2, the host computer calculates the reflected light power density from the main optical path, as well as the transmitted light power density and the reflected light power density of the twin optical path system. Step 3, calculate the splitting ratio of the twin optical path system, calculate the drift factor relative to the ideal splitting ratio after time smoothing, and update it to the main optical path. Calculate the actual transmitted light power density of the main optical path and the real-time value of the atomic polarization rate. Step 4, compare the calculated real-time value of the atomic polarization rate with the set expected value of the atomic polarization rate to obtain an error amount. Step 5, according to the error amount, the host computer outputs a control signal to the liquid crystal variable phase retarder on the pumping optical path through a PID controller to control the light power density of the pumping light, thereby suppressing the atomic polarization error.

[0035] Step 1 includes: adjusting the power density and frequency of the pumping light and the detection light, and applying excitation to the three-axis magnetic field coil 13 for compensation. The glass atomic gas cell 14 is heated to 175°C through the oven device 15 to make the atomic spin gyroscope reach an approximate working state. The glass atomic gas cell 14 is located inside the oven device 15, and the oven device 15 is located inside the three-axis magnetic field coil 13. The twin spectroscopic system in Step 1 includes a first depolarizing beam splitter prism 6 and a second depolarizing beam splitter prism 7 sequentially distributed along the pumping optical path. The transmission side of the second depolarizing beam splitter prism 7 is connected to the quarter-wave plate 8, and the reflection side is connected to the light control circuit board 16 through the first photodetector 9. The input side of the first depolarizing beam splitter prism 6 is sequentially connected to the distributed feedback laser 1 through the half-wave plate 5, the second polarization beam splitter prism 4, the liquid crystal variable phase retarder 3, and the first polarization beam splitter prism 2. The reflection side of the first depolarizing beam splitter prism 6 is connected to the input side of the third depolarizing beam splitter prism 10. The transmission side of the third depolarizing beam splitter prism 10 is connected to the light control circuit board through the second photodetector 11. The reflection side of the third depolarizing beam splitter prism is connected to the light control circuit board 16 through the third photodetector. The liquid crystal variable phase retarder 3 is connected to the host computer 17.

[0036] The control signal in step 5 is the output signal obtained by multiplying the control voltage by the high-frequency square-wave signal. After power amplification, the output signal is loaded onto the liquid crystal variable phase retarder 3. The PID controller in step 5 is implemented based on the positional discrete PID controller.

[0037] Step 5 includes the following expressions:

[0038]

[0039] where u(k) is the control voltage at the k-th moment in the control signal, k is the sequence number, K p is the proportional gain, e(k) is the error amount at the k-th moment, K i is the integral gain, Δt is the preset step size, K d is the derivative gain. In actual use, the preset step size Δt is set in advance, and e(k - 1) is the error amount at the (k - 1)-th moment.

[0040] Step 3 includes the following expressions:

[0041]

[0042] where is the actual splitting ratio of the second depolarizing beam splitter at the k-th moment, is the actual splitting ratio of the third depolarizing beam splitter at the k-th moment, is the optical power density of the reflected light collected by the first photodetector at the k-th moment in the main optical path, is the set optical power density of the transmitted light, is the set optical power density of the reflected light, ξ2 is the set splitting ratio of the third depolarizing beam splitter, and δ(k) is the splitting ratio drift factor of the twin optical paths at the k-th moment.

[0043] Step 2 includes the following expressions:

[0044]

[0045] where is the actual atomic polarizability at the k-th moment, ξ1 is the set splitting ratio of the second depolarizing beam splitter, R rel is the relaxation rate.

[0046] The present invention discloses an atomic polarization error suppression method based on a twin beam splitting system. This method takes the atomic polarization error of an atomic spin inertia measurement device as the research object. Aiming at the problem that the pump light power density received by the atoms is vulnerable to unknown noise interference from the external environment, a PID controller is designed. By feeding back the atomic polarization error to control the liquid crystal voltage, and then controlling the pump light power density. A twin optical path is introduced. Through the consistency of the beam splitting ratio between the twin optical path and the main optical path, the suppression of the beam splitting ratio drift is achieved, and the real-time acquisition of atomic polarization is realized, effectively suppressing the atomic polarization error caused by the beam splitting ratio drift. The present invention is aimed at suppressing the polarization error of the gas chamber of an atomic spin inertia measurement device, and has the characteristics of good suppression effect, high control precision, strong anti-interference ability and convenience for engineering implementation, and is applicable to the field of gas chamber polarization control of atomic inertia measurement devices.

[0047] A method for stabilizing the polarizability of an alkali metal atom, characterized by: a Distributed Feedback Laser (DFB) (1), a Polarizing Beamsplitter (PBS) (2), a Liquid Crystal Variable Retarder (LCVR) (3), a polarizing beamsplitter (4), a half-wave plate (5), a Non-polarizing Beamsplitter (NPBS) (6), a Non-polarizing Beamsplitter No. 1 (NPBS1) (7), a quarter-wave plate (8), a Photoelectric Detector No. 1 (PD1) (9), a Non-polarizing Beamsplitter No. 2 (NPBS2) (10), a Photoelectric Detector No. 2 (PD2) (11), a data acquisition module photoelectric detector No. 3 (PD3) (12), a three-axis magnetic field coil (13), a glass atomic gas chamber (14), an oven device (15), a data acquisition module (16), and a host computer module (17).

[0048] Step 1: Connect the optical control circuit board to the computer host and set the expected atomic polarization value. Adjust the power density and frequency of the pump laser and the detection laser, and apply appropriate excitation to the three-dimensional magnetic compensation coil. Heat the atomic gas chamber to 175 °C through the oven device to make the atomic spin gyroscope reach an approximate working state;

[0049] Step 2: The optical control circuit board collects the reflected light power density from the main optical path, as well as the transmitted light and reflected light power density of the twin optical path system;

[0050] Step 3: Calculate the splitting ratio of the twin optical path system. After time smoothing, calculate the drift factor relative to the ideal splitting ratio and update it to the main optical path. Calculate the actual power density of the transmitted light on the main optical path and the real-time value of atomic polarization;

[0051] Step 4: Compare the calculated atomic polarization value with the set atomic polarization value, update the PID controller parameters of the optical control circuit board, and obtain the output control voltage;

[0052] Step 5: The optical control circuit board multiplies the control voltage in Step 4 by the high-frequency square wave signal generated inside it to obtain an output signal. After power amplification, the output signal is loaded onto the LCVR to control the optical power density of the pumping laser, thereby achieving the effect of controlling the atomic polarization error.

[0053] After Step 1 is completed, Steps 2 to 5 are cycled to achieve high-precision control of the pumping optical power density and atomic polarization, and the purpose of improving the atomic polarization stability is achieved.

[0054] In Step 2, the measured optical power density of the reflected light on the main optical path is denoted as The transmitted and reflected light power densities of the twin optical path are respectively denoted as and

[0055] In Step 3, the splitting ratio is defined as the ratio of the reflected light to the transmitted light power density. The splitting ratio For each moment k, the corresponding actual splitting ratio can be calculated through the measured reflected and transmitted light power densities of the twin optical path Then the splitting ratio drift factor of the twin optical path at moment k can be written as

[0056] In Step 3, since the PBS used in the main optical path and the twin optical path is of the same model, their splitting ratio drift characteristics are basically the same. Therefore, the splitting ratio fluctuation of the twin optical path can be approximately equivalent to the splitting ratio fluctuation of the main optical path. Then, through the known ideal splitting ratio ξ1 of the main optical path and the splitting ratio drift factor δ(k) at moment k, the actual atomic polarization can be calculated, and the atomic polarization can be written as The transmitted light power density of the main optical path is related to atomic polarization. In the traditional method, since the transmitted light of the main optical path needs to enter the atomic gas cell, its actual value cannot be obtained through a photodetector. Through this method, its actual value can be deduced.

[0057] In Step 4, the PID controller is implemented based on a positional discrete PID controller, and its basic formula is where e(k) is the error value, obtained by subtracting the collected atomic polarization from the set atomic polarization; K p is the proportional gain, which is multiplied by the error term; K i is the integral gain, which is multiplied by the integral of the error term; K d is the derivative gain, which is multiplied by the derivative of the error term. In actual use, the step size Δt is preset in advance, and then the integral term and the derivative term are calculated at time k respectively, and then the output voltage u(k) at time k is obtained. This output voltage u(k) is used to control the LCVR, and the LCVR further controls the output power density of the main path light, so as to achieve the effect of controlling the atomic polarization.

[0058] Figure 1 is the structure of the optical pumping device of the atomic spin inertia measurement device. The light emitted by the distributed feedback laser passes through the constant power module composed of PBS and LCVR, and then is divided into two beams after passing through the half-wave plate and NPBS: the light beam of the main path is divided into two beams by NPBS1, the transmitted light is converted into circularly polarized light by the quarter-wave plate and enters the gas chamber to optically pump the electrons, and the reflected light of NPBS1 is detected by PD1; the light beam of the twin optical path is divided into two beams after passing through NPBS2, the transmitted light is detected by PD2, and the reflected light is detected by PD3; the electrical signals of PD1, PD2, and PD3 are transmitted to the upper computer through the data acquisition module for data processing. The upper computer calculates the real-time atomic polarization error value through operation, updates the output voltage through PID control, that is, the liquid crystal control voltage, controls the pumping light power density, so that the atomic polarization is stabilized at the set value, and thus the purpose of reducing the atomic polarization error is achieved.

[0059] Figure 2 is the process of the present invention. First, the upper computer sets the expected value of atomic polarization, that is, the power density value of the transmitted light of the main path. At time k, the power density of the main path reflection, the transmitted light of the twin optical path, and the reflected light of the twin optical path are collected by the photodetectors PD1, PD2, and PD3 respectively. Then, the splitting ratio and the splitting drift factor of the twin optical path at time k are calculated from the values of PD2 and PD3, and applied to the main optical path to obtain the actual transmitted light power density and atomic polarization of the main optical path, and then compared with the expected atomic polarization to obtain the error value. Calculate u(k) through positional PID control and output it, and at the same time perform the next acquisition and loop through the above steps.

[0060] Let the optical power densities collected by PD1, PD2, and PD3 at time k be

[0061] Then the actual splitting ratio of the twin optical path at time k The splitting ratio drift factor is Similarly, since the models of NPBS1 in the main optical path and NPBS2 in the twin optical path are the same, the actual splitting ratio of the main optical path can also be considered Furthermore, the transmitted optical power density of the main optical path, that is, the optical power density of the pump light, can be calculated as follows:

[0062] The atomic polarization is related to the pump light power density transmitted by the main optical path.

[0063] It can also be simplified to

[0064] Figure 3 This is the flow chart for updating the controller parameters in the present invention. The expression of the controller is:

[0065]

[0066] where k is time, e(k) is the error of the system at time k, that is, the difference between the desired atom and the actual value. K p is the proportional gain, which is directly multiplied by the error term and is collectively called the proportional term, and is usually used for the fast response of the system. K i is the integral gain, which is multiplied by the accumulation of all past errors to obtain the integral term, and it helps to eliminate the steady-state error. K d is the derivative gain, and the derivative term represents the rate of change between the current error and the error at the previous moment. It is used to predict the future trend of the error and suppress the over-response of the system. Δt, K p , K i , K d are all manually set values.

[0067] The content not described in detail in the specification of the present invention belongs to the prior art well-known to those skilled in the art. It is hereby pointed out that the above description helps those skilled in the art to understand the present invention, but does not limit the protection scope of the present invention. Any implementation that makes equivalent replacements, modifications and improvements, and / or simplifies the above description without departing from the essential content of the present invention falls within the protection scope of the present invention.

Claims

1. An atomic polarization error suppression method based on a twin spectroscopic system, characterized in that It includes the following steps: Step 1: A twin beam splitting system is arranged on the pumping light incident side of the glass atomic gas cell. The twin beam splitting system splits the main path light into a first transmitted main path light and a first reflected branch light, splits the first reflected branch light into a second transmitted branch light and a second reflected branch light, and splits the first transmitted main path light into a second transmitted main path light and a third reflected branch light. The second transmitted main path light enters the glass atomic gas cell through a quarter-wave plate. The second transmitted branch light, the second reflected branch light, and the third reflected branch light are respectively collected by a light control circuit board. The light control circuit board is connected to a host computer, and the expected atomic polarization rate is set through the host computer; Step 2: The host computer calculates the reflected light power density from the main optical path, as well as the transmitted light power density and the reflected light power density of the twin optical path system; Step 3: Calculate the beam splitting ratio of the twin optical path system, calculate the drift factor relative to the ideal beam splitting ratio after time smoothing, and update it to the main optical path. Calculate the actual transmitted light power density of the main optical path and the real-time value of the atomic polarization rate; Step 4: Compare the calculated real-time value of the atomic polarization rate with the set expected value of the atomic polarization rate to obtain an error amount; Step 5: According to the error amount, the host computer outputs a control signal to the liquid crystal variable phase retarder on the pumping optical path through a PID controller to control the light power density of the pumping light, thereby suppressing the atomic polarization error.

2. The atomic polarization error suppression method based on a twin spectroscopic system according to claim 1, characterized in that Step 1 includes: adjusting the power density and frequency of the pumping light and the detection light, and applying an excitation to the three-axis magnetic field coil for compensation. The glass atomic gas cell is heated to 175 °C through an oven device, so that the atomic spin gyroscope reaches an approximate working state. The glass atomic gas cell is located inside the oven device, and the oven device is located inside the three-axis magnetic field coil.

3. A method for suppressing atomic polarization error based on a twin spectroscopic system according to claim 1, characterized in that, The twin beam splitting system in Step 1 includes a first depolarizing beam splitting prism and a second depolarizing beam splitting prism that are sequentially distributed along the pumping optical path. The transmission side of the second depolarizing beam splitting prism is connected to the quarter-wave plate, and the reflection side is connected to the light control circuit board through a first photodetector. The input side of the first depolarizing beam splitting prism is sequentially connected to a distributed feedback laser through a half-wave plate, a second polarization beam splitting prism, a liquid crystal variable phase retarder, and a first polarization beam splitting prism. The reflection side of the first depolarizing beam splitting prism is connected to the input side of a third depolarizing beam splitting prism. The transmission side of the third depolarizing beam splitting prism is connected to the light control circuit board through a second photodetector. The reflection side of the third depolarizing beam splitting prism is connected to the light control circuit board through a third photodetector. The liquid crystal variable phase retarder is connected to the host computer.

4. A method for suppressing atomic polarization error based on a twin spectroscopic system according to claim 1, characterized in that, The control signal in Step 5 is an output signal obtained by multiplying a control voltage by a high-frequency square wave signal. After power amplification, the output signal is loaded onto the liquid crystal variable phase retarder.

5. A method for suppressing atomic polarization error based on a twin spectroscopic system according to claim 1, characterized in that The PID controller in Step 5 is implemented based on a position-type discrete PID controller.

6. A method for suppressing atomic polarization error based on a twin spectroscopic system according to claim 1, characterized in that, Step 5 includes the following expressions: where u(k) is the control voltage at the k-th moment in the control signal, k is the sequence number, and K p is the proportional gain, e(k) is the error amount at the k-th moment, and K i is the integral gain, Δt is the preset step size, and K d is the differential gain. In actual use, the preset step size Δt is set in advance, and e(k - 1) is the error amount at the (k - 1)-th moment.

7. A method for suppressing atomic polarization error based on a twin spectroscopic system according to claim 1, characterized in that, Step 3 includes the following expressions: wherein is the actual splitting ratio of the second depolarizing beam splitter prism at the k-th moment, is the actual splitting ratio of the third depolarizing beam splitter prism at the k-th moment, is the optical power density of the reflected light collected by the first photodetector in the main optical path at the k-th moment, is the set optical power density of the transmitted light, is the set optical power density of the reflected light, ξ2 is the set splitting ratio of the third depolarizing beam splitter prism, and δ(k) is the splitting ratio drift factor of the twin optical paths at the k-th moment.

8. A method for suppressing atomic polarization error based on a twin spectroscopic system according to claim 1, characterized in that Step 2 includes the following expressions: wherein is the actual atomic polarizability at time k, ξ1 is the set beam splitting ratio of the second depolarizing beam splitter, and R rel is the relaxation rate.

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