SERF inertial measurement device electron polarizability online measurement and closed loop method

Abstract

According to the SERF inertial measurement device electron longitudinal polarizability online measurement and closed-loop method, pumping light can be modulated through an electro-optical modulator to be rapidly switched between a left-hand circular polarization state and a right-hand circular polarization state, the electron spinning direction is overturned accordingly, and the longitudinal polarizability is changed accordingly. The light absorption of the pumping light changes along with the change of the electron spinning longitudinal polarizability, so that the change of the light intensity of the pumping light out of the cylinder reflects the change condition of the electron longitudinal polarizability. And the peak value of the light intensity of the pumping light out of the cylinder under the pulse modulation frequency is demodulated through the lock-in amplifier, so that the on-line measurement of the electron longitudinal polarizability of the SERF inertial measurement device is realized. The light intensity of pumping light entering a cylinder is adjusted by controlling the phase delay amount of the liquid crystal phase delayer LCVR, and the peak voltage of the light intensity of pumping light exiting the cylinder obtained by demodulation of the lock-in amplifier is controlled to remain unchanged, so that the real-time in-situ closed-loop control of the electron longitudinal polarizability of the SERF inertial measurement device is realized.

Description

Technical Field

[0001] The invention relates to the technical field of SERF inertial measurement, in particular to an online measurement and closed-loop method for electronic polarizability of a SERF inertial measurement device, wherein the pump light is modulated to quickly switch between a left-handed circular polarization state and a right-handed circular polarization state, and the electron spin direction is flipped accordingly, and the change of the light intensity of the pump light out of the tube is used to reflect the change of the electron longitudinal polarizability to achieve online measurement of the electron longitudinal polarizability, and the pump light into the tube is adjusted by a phase delay amount, and the peak voltage of the pump light out of the tube is kept unchanged, so as to achieve real-time in-situ closed-loop control of the electron longitudinal polarizability. The method has simple experimental steps, can achieve real-time in-situ closed-loop control of the longitudinal polarizability of alkali metal atoms, is helpful to improve the noise of the atomic spin inertial measurement system, improve the measurement sensitivity and long-term stability, and improve the robustness of the system under different environmental conditions. Background Art

[0002] The SERF (Spin-Exchange Relaxation-Free) atomic inertial measurement device has the potential to achieve ultra-high sensitivity inertial measurement. The device is used in cutting-edge basic physics research, including dark matter detection, measurement of exotic interaction forces, and verification of CPT (Charge Conjugation, Parity and Time Reversal) symmetry breaking. The high-precision gyroscope integrated in the SERF atomic inertial measurement device has the advantages of high accuracy, small size, and simple structure. It shows broad application prospects in the field of long-duration high-precision inertial navigation and is of great significance to national defense security.

[0003] In the SERF atomic spin inertial measurement device, the fluctuation of the alkali metal electron spin polarization rate introduces polarization noise, which affects the sensitivity of inertial measurement. At the same time, as the first-order error term of the long-term stability of the measurement system, the fluctuation of the alkali metal electron spin polarization rate is the main factor causing the zero-bias instability of the system. Therefore, it is necessary to realize the real-time in-situ closed-loop control of the alkali metal atomic polarization rate to improve the sensitivity and long-term stability of the system. Previously, researchers proposed a pump light intensity stabilization system for the stable control of the electronic polarization rate. The optical power of the pump light path splitting was closed-loop controlled by a stable power system based on a liquid crystal phase delay, thereby realizing indirect control of the main pump light path and suppressing the fluctuation of the electronic polarization rate. This method cannot realize the in-situ control of the electronic polarization rate of the atomic ensemble, and the optical device splitting ratio is greatly affected by the ambient temperature, so the control effect is limited. In addition, the researchers also measured the electronic polarization rate by locking the amplitude or phase of the electronic resonance peak to achieve closed-loop control of the polarization rate, but the conversion coefficient between the polarization rate and the resonance peak is affected by parameters such as temperature, and the modulated magnetic field required to be applied by this method may cause the system to relax during the measurement process. Therefore, further research is needed to achieve in-situ direct measurement and closed-loop control of the electronic polarizability of an atomic ensemble.

[0004] In order to overcome the shortcomings of the above methods, the present invention proposes to introduce electro-optic modulators (EOM) to realize left-hand and right-hand modulation of circularly polarized light pumped into the cylinder, thereby controlling the longitudinal reversal of the electron spin, and realizing in-situ online measurement of the electron polarization rate through the peak value of the change in the intensity of the pump light out of the cylinder. By controlling the phase delay of the liquid crystal phase retarder LCVR to adjust the intensity of the pump light entering the cylinder to control the stability of the electron polarization rate (LCVR, Liquid Crystal Variable Retarder, liquid crystal phase retarder), the in-situ real-time closed-loop control of the electron longitudinal polarization rate of the SERF inertial measurement device is realized. Summary of the invention

[0005] In view of the defects or deficiencies of the prior art, the present invention proposes an online measurement and closed-loop method for the electronic polarizability of a SERF inertial measurement device, which can quickly switch between the left-handed circular polarization state and the right-handed circular polarization state by modulating the pump light, and the electron spin direction is flipped accordingly, and the change of the pump light intensity out of the tube is used to reflect the change of the electron longitudinal polarizability to achieve online measurement of the electron longitudinal polarizability, and the pump light intensity into the tube is adjusted by the phase delay amount, and the peak voltage of the pump light intensity out of the tube is kept unchanged, so as to achieve real-time in-situ closed-loop control of the electron longitudinal polarizability. The method has simple experimental steps, can achieve real-time in-situ closed-loop control of the longitudinal polarizability of alkali metal atoms, and is helpful to improve the noise of the atomic spin inertial measurement system, improve the measurement sensitivity and long-term stability, and improve the robustness of the system under different environmental conditions.

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

[0007] An online measurement and closed-loop method for electronic polarizability of a SERF inertial measurement device, characterized in that it comprises the following steps:

[0008] Step 1, heating the atomic gas chamber in the SERF inertial measurement device to the operating temperature;

[0009] Step 2, controlling the pumping light to sequentially form left-handed circularly polarized light and right-handed circularly polarized light on the optical path of the pumping light incident side of the atomic gas chamber;

[0010] Step 3, wait for the pumping to reach a steady state, and perform three-axis magnetic compensation so that the system works in a gyro state;

[0011] Step 4, collecting the peak voltage of the pump light output tube optical power signal at the modulation frequency, the change of the peak voltage reflects the change of the electronic polarizability of the atomic ensemble, so as to realize the in-situ online measurement of the electronic polarizability;

[0012] Step 5, taking the peak voltage as the closed-loop feedback quantity, adopting the proportional-integral-differential (PID) control strategy to generate a control signal, and using the control signal to adjust the optical power of the pumping light entering the tube, so as to keep the peak voltage of the pumping light intensity out of the tube unchanged through closed-loop control, thereby realizing real-time in-situ closed-loop control of the electron longitudinal polarization rate of the SERF inertial measurement device.

[0013] The atomic gas chamber in step 1 is installed in a non-magnetic electric heating oven, and the non-magnetic electric heating oven is placed in a coil frame. The surface of the coil frame is a three-axis magnetic compensation coil, and the outside of the three-axis magnetic compensation coil is a layer of manganese-zinc ferrite magnetic shielding tube, and the outside of the manganese-zinc ferrite magnetic shielding tube is a three-layer permalloy magnetic shielding tube. On the pumping light input side of the atomic gas chamber, the pumping laser is emitted along the z-axis direction, and the first 1 / 2 wave plate, the first polarization beam splitter prism, the liquid crystal phase retarder, the second polarization beam splitter prism, the electro-optical modulator crystal, the third polarization beam splitter prism and the 1 / 4 wave plate are connected in sequence. The 1 / 4 wave plate is connected to the atomic On the pumping light input side of the gas chamber, the electro-optic modulator crystal is connected to an external signal trigger through an electro-optic modulator controller, the pumping light output side of the atomic gas chamber is connected to the liquid crystal phase retarder through an attenuation plate, a first photodetector, a phase-locked amplifier and an electronic control unit in sequence, on the detection light input side of the atomic gas chamber, the detection laser is emitted along the x-axis direction, and is connected to the second 1 / 2 wave plate and the fourth polarization beam splitter prism in sequence, the fourth polarization beam splitter prism is connected to the detection light input side of the atomic gas chamber, and the detection light output side of the atomic gas chamber is connected to a host computer through a third 1 / 2 wave plate and a second photodetector in sequence.

[0014] Step 2 includes locking the pumping light frequency at the K atom absorption peak D1 line, applying a pulse square wave voltage to the electro-optic modulator, wherein the low level voltage of the pulse square wave voltage is 0 and the high level voltage is the half-wave voltage of the electro-optic modulator. The duty cycle of the low-level voltage signal is greater than the duty cycle of the high-level voltage signal, the duration of the low-level pulse corresponds to the left-handed circularly polarized light, and the duration of the high-level pulse corresponds to the right-handed circularly polarized light.

[0015] Step 4 includes the following formula:

[0016]

[0017] Among them I max (z) is the maximum light intensity of the pump light when the longitudinal polarization rate of the electron gradually increases to the transient state under the action of left-handed circularly polarized light, I(0) is the initial light intensity of the pump light entering the tube, e is a natural constant, N is the atomic density of the alkali metal in the gas chamber, σ p is the absorption cross-sectional area of ​​light, which indicates the absorption capacity of each atom to photons, that is, the probability of photons being absorbed when they interact with atoms, z is the propagation distance of the pumping light in the atomic gas chamber, is the longitudinal polarization rate of electrons under the action of left-handed circularly polarized light that increases to a transient steady state, I min (z) is the pumping light intensity when the electron longitudinal polarization rate gradually decreases to a transient state under the action of right-handed circularly polarized light, that is, the minimum pumping light intensity. It is the longitudinal polarization rate of electrons under the action of right-handed circularly polarized light that is reduced to a quasi-stable state.

[0018] Step 4 includes the following formula:

[0019]

[0020] Where U is the peak voltage of the pump light output tube light intensity signal, K PD is the photodetector conversion factor.

[0021] Step 4 includes the following formula:

[0022]

[0023] where arcsinh is the inverse of the hyperbolic sine function.

[0024] The technical effects of the present invention are as follows: The present invention provides an online measurement and closed-loop method for the electronic polarizability of a SERF inertial measurement device. The electro-optic modulator is used to modulate the pump light to quickly switch between the left-handed circular polarization state and the right-handed circular polarization state, and the electron spin direction is flipped accordingly, and the longitudinal polarization rate also changes accordingly. The absorption of the pump light changes with the change of the longitudinal polarization rate of the electron spin, so the change of the pump light output tube intensity reflects the change of the electron longitudinal polarization rate. The online measurement of the electronic longitudinal polarization rate of the SERF inertial measurement device is achieved by demodulating the peak value of the pump light output tube intensity at the pulse modulation frequency by a phase-locked amplifier. The pump light input tube intensity is adjusted by controlling the phase delay amount of the liquid crystal phase retarder LCVR, and the peak voltage of the pump light output tube intensity obtained by controlling the phase-locked amplifier demodulation remains unchanged, thereby achieving real-time in-situ closed-loop control of the electronic longitudinal polarization rate of the SERF inertial measurement device.

[0025] Compared with the prior art, the advantages of the present invention are as follows: the online measurement and closed-loop method of the electronic polarizability of a SERF inertial measurement device of the present invention can realize real-time direct measurement and in-situ closed-loop control of the longitudinal polarizability of alkali metal atoms, compared with the previous methods of closed-loop light splitting feedback before pumping into the tube, and locking the electron resonance peak amplitude or phase feedback to achieve closed-loop control of polarizability, which is helpful to improve the noise of the atomic spin inertial measurement system, improve the measurement sensitivity and long-term stability, and improve the robustness of the system under different environmental conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The structure diagram of the SERF inertial measurement device involved in the online measurement and closed-loop method of the electronic polarizability of the SERF inertial measurement device of the present invention is shown in FIG. SERF is spin-exchange relaxation-free.

[0027] The reference numerals are as follows: L1-pumping laser; L2-first 1 / 2 wave plate; L3-first polarization beam splitter prism; L4-liquid crystal variable retarder (LCVR); L5-second polarization beam splitter prism; L6-electro-optic modulator crystal (EOM); L7-electro-optic modulator controller; L8-external signal trigger (Signal Generator); L9-third polarization beam splitter prism; L10-1 / 4 wave plate; L11-attenuation plate; L12-first photodetector; L13-lock-in amplifier (LIA); L14-electronic control unit (ECU) Unit, adopts PID control, PID, proportional-integral-derivative, proportional integral differential); L15-detection laser; L16-third 1 / 2 wave plate; L17-fourth polarization splitter prism; L18-third 1 / 2 wave plate; L19-second photodetector; L20-host computer; L21-atomic gas chamber; L22-non-magnetic electric heating oven; L23-manganese zinc ferrite magnetic shielding cylinder; L24-three-axis magnetic compensation coil; L25-Permalloy magnetic shielding cylinder; xyz-three axes of rectangular coordinate system (i.e., x-axis, y-axis, and z-axis). DETAILED DESCRIPTION

[0028] Below is the attached figure ( Figure 1 ) and Examples illustrate the present invention.

[0029] Figure 1 The structure diagram of the SERF inertial measurement device involved in the online measurement and closed-loop method of the electronic polarizability of the SERF inertial measurement device of the present invention is shown in FIG. Figure 1 As shown, an online measurement and closed-loop method for electronic polarizability of a SERF inertial measurement device comprises the following steps: step 1, heating an atomic gas chamber in the SERF inertial measurement device to an operating temperature; step 2, controlling the pumping light to sequentially form left-handed circularly polarized light and right-handed circularly polarized light on the optical path of the pumping light incident side of the atomic gas chamber; step 3, waiting for the pumping to reach a steady state, performing three-axis magnetic compensation, so that the system works in a gyroscopic state; step 4, collecting the peak voltage of the optical power signal of the pumping light output tube at the modulation frequency, wherein the change of the peak voltage reflects the change of the electronic polarizability of the atomic ensemble; step 5, taking the peak voltage as a closed-loop feedback quantity, adopting a proportional integral differential PID control strategy to generate a control signal, and using the control signal to adjust the optical power of the pumping light input tube, so as to keep the peak voltage of the pumping light output tube light intensity unchanged through closed-loop control, thereby realizing real-time in-situ closed-loop control of the electronic longitudinal polarizability of the SERF inertial measurement device.

[0030] The atomic gas chamber L21 in step 1 is installed in a non-magnetic electric heating oven L22, and the non-magnetic electric heating oven L22 is placed in a coil frame. The surface of the coil frame is a three-axis magnetic compensation coil L24, and the outside of the three-axis magnetic compensation coil L24 is a layer of manganese-zinc ferrite magnetic shielding tube L23, and the outside of the manganese-zinc ferrite magnetic shielding tube L23 is a three-layer permalloy magnetic shielding tube L25. On the pumping light input side of the atomic gas chamber L21, the pumping laser L1 is emitted along the z-axis direction, and is connected in sequence to the first 1 / 2 wave plate L2, the first polarization beam splitter prism L3, the liquid crystal phase retarder L4, the second polarization beam splitter prism L5, the electro-optic modulator crystal L6, the third polarization beam splitter prism L9 and the 1 / 4 wave plate L10, and the 1 / 4 wave plate L10 is connected to the atomic gas chamber L2 1, the electro-optic modulator crystal L6 is connected to the external signal trigger L8 through the electro-optic modulator controller L7, the pumping light output side of the atomic gas chamber L21 is connected to the liquid crystal phase retarder L4 through the attenuation plate L11, the first photodetector L12, the phase-locked amplifier L13 and the electronic control unit L14 in sequence, on the detection light input side of the atomic gas chamber L21, it is emitted by the detection laser L15 along the x-axis direction, and is connected to the second 1 / 2 wave plate L16 and the fourth polarization beam splitter prism L17 in sequence, the fourth polarization beam splitter prism L17 is connected to the detection light input side of the atomic gas chamber L21, and the detection light output side of the atomic gas chamber L21 is connected to the host computer L20 through the third 1 / 2 wave plate L18 and the second photodetector L19 in sequence.

[0031] Step 2 includes locking the pumping light frequency at the K atom absorption peak D1 line, applying a pulse square wave voltage to the electro-optic modulator, wherein the low level voltage of the pulse square wave voltage is 0 and the high level voltage is the half-wave voltage of the electro-optic modulator. The duty cycle of the low-level voltage signal is greater than the duty cycle of the high-level voltage signal, the duration of the low-level pulse corresponds to the left-handed circularly polarized light, and the duration of the high-level pulse corresponds to the right-handed circularly polarized light.

[0032] Step 4 includes the following formula:

[0033]

[0034] Among them I max (z) is the maximum light intensity of the pump light when the longitudinal polarization rate of the electron gradually increases to the transient state under the action of left-handed circularly polarized light, I(0) is the initial light intensity of the pump light entering the tube, e is a natural constant, N is the atomic density of the alkali metal in the gas chamber, σ p is the absorption cross-sectional area of ​​light, which indicates the absorption capacity of each atom to photons, that is, the probability of photons being absorbed when they interact with atoms, z is the propagation distance of the pumping light in the atomic gas chamber, is the longitudinal polarization rate of electrons under the action of left-handed circularly polarized light that increases to a transient steady state, I min (z) is the pumping light intensity when the electron longitudinal polarization rate gradually decreases to a transient state under the action of right-handed circularly polarized light, that is, the minimum pumping light intensity. It is the longitudinal polarization rate of electrons under the action of right-handed circularly polarized light that is reduced to a quasi-stable state.

[0035] Step 4 includes the following formula:

[0036]

[0037] Where U is the peak voltage of the pump light output tube light intensity signal, K PD is the photodetector conversion factor.

[0038] Step 4 includes the following formula:

[0039]

[0040] where arcsinh is the inverse of the hyperbolic sine function.

[0041] An online measurement and closed-loop method for the longitudinal polarization rate of electrons in a SERF inertial measurement device is disclosed. The pump light is modulated by an electro-optic modulator to quickly switch between the left-handed circular polarization state and the right-handed circular polarization state, and the electron spin direction is flipped accordingly, and the longitudinal polarization rate also changes accordingly. The absorption of the pump light changes with the change of the longitudinal polarization rate of the electron spin, so the change of the pump light output tube intensity reflects the change of the electron longitudinal polarization rate. The online measurement of the longitudinal polarization rate of electrons in the SERF inertial measurement device is achieved by demodulating the peak value of the pump light output tube intensity under the pulse modulation frequency by a phase-locked amplifier. The pump light input tube intensity is adjusted by controlling the phase delay amount of the liquid crystal phase retarder LCVR, and the peak voltage of the pump light output tube intensity obtained by controlling the phase-locked amplifier demodulation remains unchanged, thereby achieving real-time in-situ closed-loop control of the longitudinal polarization rate of electrons in the SERF inertial measurement device.

[0042] refer to Figure 1 As shown, an online measurement and closed-loop method for electronic polarizability of a SERF inertial measurement device is characterized in that it includes the following steps: Step 1, using a non-magnetic electric heating system to heat the air chamber of the SERF inertial measurement device to the operating temperature, and demagnetizing the shielding tube to ensure that the air chamber is in a weak magnetic environment; Step 2, turning on the pumping laser, using a saturated absorption frequency stabilization module, and locking the pumping laser frequency to the K atomic absorption peak D1 line. Control the electro-optical modulator (EOM) driver to apply a pulsed square wave voltage, control its low-level voltage to 0, and the high-level voltage to be the half-wave voltage of the electro-optical modulator The duty cycle of the low-level voltage signal is greater than that of the high-level voltage signal. Adjust the 1 / 4 wave plate of the pumping optical path so that the pumping laser is left-handed after passing through the electro-optic modulator and the 1 / 4 wave plate during the low-level pulse duration (σ + ) circularly polarized light, the light produces a phase delay of π during the duration of the pulse high level, and the pump laser is right-handed (σ - ) circularly polarized light; step 3, wait for the pumping to reach a steady state, and perform three-axis magnetic compensation so that the system works in a gyro state; step 4, lock the peak voltage of the optical power signal collected by the pumping tube photodetector at the modulation frequency through a phase-locked amplifier, and the change in the peak voltage reflects the change in the electronic polarizability of the atomic ensemble, that is, the in-situ online measurement of the electronic polarizability is realized; step 5, using the above peak voltage signal as a closed-loop feedback quantity, adopting a proportional integral differential PID control strategy to generate a control signal, and inputting the control signal into a liquid crystal phase retarder, and adjusting the optical power of the pumping light entering the tube by controlling its phase delay, so as to realize the closed-loop control of the peak voltage signal, that is, the real-time in-situ closed-loop SERF inertial measurement device electronic longitudinal polarization.

[0043] The atomic gas chamber L21 is installed in a non-magnetic electric heating oven L22, and the oven is placed in a coil frame. The surface of the coil frame is a three-axis magnetic compensation coil L24, and the outside of the coil is a magnetic shielding system composed of a layer of manganese-zinc ferrite L23 and three layers of permalloy L25, providing a non-magnetic environment.

[0044] The pumping laser is emitted from the pumping laser L1, passes through the first 1 / 2 wave plate L2, the first polarization beam splitter prism L3, the liquid crystal phase retarder L4, the second polarization beam splitter prism L5, the electro-optic modulator crystal L6, the third polarization beam splitter prism L9, and the 1 / 4 wave plate L10, and then enters the atomic gas chamber L21. The detection laser is emitted from the detection laser L15, passes through the second 1 / 2 wave plate L16 and the fourth polarization beam splitter prism L17, and then enters the atomic gas chamber L21. The detection light passes through the third 1 / 2 wave plate L18 and the second photodetector L19, and then is converted into a voltage signal and collected to the host computer L20.

[0045] The electro-optical modulation module includes an electro-optical modulator crystal L6 and an electro-optical modulator controller L7, an external signal trigger L8, a third polarization beam splitter prism L9 and a quarter wave plate L10; the external signal trigger L8 is connected to the electro-optical modulator controller L7 to input an external trigger signal, and the electro-optical modulator controller L7 outputs a response high-voltage pulse drive voltage to the electro-optical modulator crystal L6. The pumping optical path quarter wave plate L10 is adjusted so that during the duration of the pulse low level, the second polarization beam splitter prism L5 transmits the light beam through the electro-optical modulator crystal L6 without phase delay, and the pumping laser is left-handed (σ +) circularly polarized light; during the pulse high level duration, the second polarization beam splitter prism L5 transmits the light beam through the electro-optic modulator crystal L6 and generates a phase delay of π, and the pump laser is right-handed (σ after passing through the third polarization beam splitter prism L9 and the 1 / 4 wave plate L10 - ) circularly polarized light, set the duty cycle of the low-level voltage signal to be greater than the duty cycle of the high-level voltage signal, that is, pump left-handed (σ + )Circularly polarized light lasts longer.

[0046] The electron longitudinal polarizability measurement module includes an attenuation plate L11 at the pumping tube, a first photodetector L12 and a phase-locked amplifier L13.

[0047] When the pump laser passes through the electro-optical modulation module, the polarization state of the laser incident on the atomic gas chamber quickly switches between left-handed and right-handed circularly polarized light, and the electron spin direction flips accordingly, and the longitudinal polarization rate also changes accordingly. The transmitted light intensity of left-handed circularly polarized light and right-handed circularly polarized light when passing through the atomic gas chamber L21 can be described by the following differential equation:

[0048]

[0049] The electron spin longitudinal polarization The relationship with I(z) is as follows:

[0050]

[0051] In the above formula, I(z) is the light intensity of the pump light at position z (out of the tube); z is the propagation distance of the pump light in the atomic gas chamber; N is the atomic number density of the alkali metal in the gas chamber; p is the absorption cross-sectional area of ​​the light, which represents the absorption capacity of each atom for photons, that is, the probability of being absorbed when a photon interacts with an atom; is the longitudinal polarization rate of the electron spin of the alkali metal atom, indicating the average orientation of the electron spin along the z-axis; I(0) is the initial light intensity at the entrance of the pumping light. There is a monotonic relationship between it and I(z).

[0052] The longitudinal polarization rate of the electron gradually increases to a transient stable state under the action of left-handed circularly polarized light. At this time, the light intensity out of the tube is the maximum:

[0053]

[0054] Under the action of right-handed circularly polarized light, the longitudinal polarization rate of the electron gradually decreases and reaches a transient steady state. At this time, the light intensity out of the tube is the minimum:

[0055]

[0056] In the above formula is the temporary steady-state value of the electron longitudinal polarization under the action of left-handed circularly polarized light, I max (z) is the light intensity out of the tube under the corresponding state; is the temporary steady-state value of the electron longitudinal polarization under the action of right-handed circularly polarized light, I min (z) is the light intensity out of the tube under the corresponding state.

[0057] The phase-locked amplifier L13 demodulates the peak value of the pumped tube light intensity signal:

[0058]

[0059] In the above formula, U is the peak voltage of the light intensity signal of the pump tube demodulated by the lock-in amplifier L13; K PD K PD is the conversion factor of the photodetector. There is a monotonic relationship between and Y. When the pump light intensity is I(0), the electron longitudinal polarization rate in the transient steady state under the left-right hand modulation of the pump light pulse is:

[0060]

[0061] Arcsinh is the inverse function of the hyperbolic sine function, also known as the inverse hyperbolic sine.

[0062] The electronic longitudinal polarization rate closed-loop module includes an electronic polarization rate measurement module, an electronic control unit L14, and a liquid crystal phase retarder L4. The peak voltage signal obtained by the electronic longitudinal polarization rate measurement module is a closed-loop feedback quantity. The electronic control unit L14 adopts a proportional integral differential PID control strategy to generate a control signal, and the control signal is input into the liquid crystal phase retarder L4. By controlling its phase delay amount to adjust the optical power of the pumping light entering the tube, the closed-loop control of the peak voltage signal is realized, that is, the electronic longitudinal polarization rate of the SERF inertial measurement device is measured in real time in situ in a closed-loop manner.

[0063] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. A SERF inertial measurement device electronic polarizability online measurement and closed loop method, characterized in that: The following steps are involved: Step 1, heating the atomic gas chamber in the SERF inertial measurement device to the operating temperature; Step 2, controlling the pumping light to sequentially form left-handed circularly polarized light and right-handed circularly polarized light on the optical path of the pumping light incident side of the atomic gas chamber; Step 3, wait for the pumping to reach a steady state, and perform three-axis magnetic compensation so that the system works in a gyro state; Step 4, collecting the peak voltage of the pump light output tube optical power signal at the modulation frequency, the change of the peak voltage reflects the change of the electronic polarizability of the atomic ensemble, so as to realize the in-situ online measurement of the electronic polarizability; Step 5, taking the peak voltage as the closed-loop feedback quantity, adopting the proportional-integral-differential (PID) control strategy to generate a control signal, and using the control signal to adjust the optical power of the pumping light entering the tube, so as to keep the peak voltage of the pumping light intensity out of the tube unchanged through closed-loop control, thereby realizing real-time in-situ closed-loop control of the electron longitudinal polarization rate of the SERF inertial measurement device.

2. The SERF inertial measurement device electronic polarizability online measurement and closed-loop method according to claim 1, characterized in that: The atomic gas chamber in step 1 is installed in a non-magnetic electric heating oven, and the non-magnetic electric heating oven is placed in a coil frame. The surface of the coil frame is a three-axis magnetic compensation coil, and the outside of the three-axis magnetic compensation coil is a layer of manganese-zinc ferrite magnetic shielding tube, and the outside of the manganese-zinc ferrite magnetic shielding tube is a three-layer permalloy magnetic shielding tube. On the pumping light input side of the atomic gas chamber, the pumping laser is emitted along the z-axis direction, and the first 1 / 2 wave plate, the first polarization beam splitter prism, the liquid crystal phase retarder, the second polarization beam splitter prism, the electro-optical modulator crystal, the third polarization beam splitter prism and the 1 / 4 wave plate are connected in sequence. The 1 / 4 wave plate is connected to the atomic On the pumping light input side of the gas chamber, the electro-optic modulator crystal is connected to an external signal trigger through an electro-optic modulator controller, the pumping light output side of the atomic gas chamber is connected to the liquid crystal phase retarder through an attenuation plate, a first photodetector, a phase-locked amplifier and an electronic control unit in sequence, on the detection light input side of the atomic gas chamber, the detection laser is emitted along the x-axis direction, and is connected to the second 1 / 2 wave plate and the fourth polarization beam splitter prism in sequence, the fourth polarization beam splitter prism is connected to the detection light input side of the atomic gas chamber, and the detection light output side of the atomic gas chamber is connected to a host computer through a third 1 / 2 wave plate and a second photodetector in sequence.

3. The SERF inertial measurement device electronic polarizability online measurement and closed-loop method according to claim 1, characterized in that: Step 2 includes locking the pumping light frequency at the K atom absorption peak D1 line, applying a pulse square wave voltage to the electro-optic modulator, wherein the low level voltage of the pulse square wave voltage is 0 and the high level voltage is the half-wave voltage of the electro-optic modulator. The duty cycle of the low-level voltage signal is greater than the duty cycle of the high-level voltage signal, the duration of the low-level pulse corresponds to the left-handed circularly polarized light, and the duration of the high-level pulse corresponds to the right-handed circularly polarized light.

4. The SERF inertial measurement device electronic polarizability online measurement and closed-loop method according to claim 1, characterized in that: Step 4 includes the following formula: Among them I max (z) is the maximum light intensity of the pump light when the longitudinal polarization rate of the electron gradually increases to the transient state under the action of left-handed circularly polarized light, I(0) is the initial light intensity of the pump light entering the tube, e is a natural constant, N is the atomic density of the alkali metal in the gas chamber, σ p is the absorption cross-sectional area of ​​light, which indicates the absorption capacity of each atom to photons, that is, the probability of photons being absorbed when they interact with atoms, z is the propagation distance of the pumping light in the atomic gas chamber, is the longitudinal polarization rate of electrons under the action of left-handed circularly polarized light that increases to a transient steady state, I min (z) is the pumping light intensity when the electron longitudinal polarization rate gradually decreases to a transient state under the action of right-handed circularly polarized light, that is, the minimum pumping light intensity. It is the longitudinal polarization rate of electrons under the action of right-handed circularly polarized light that is reduced to a quasi-stable state.

5. The SERF inertial measurement device electronic polarizability online measurement and closed-loop method according to claim 1, characterized in that: Step 4 includes the following formula: Where U is the peak voltage of the pump light output tube light intensity signal, K PD is the photodetector conversion factor.

6. The SERF inertial measurement device electronic polarizability online measurement and closed-loop method according to claim 1, characterized in that: Step 4 includes the following formula: where arcsinh is the inverse of the hyperbolic sine function.

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