阅读说明：本技术 一种基于光频移操控的闭环原子自旋陀螺仪 (Closed-loop atomic spin gyroscope based on optical frequency shift control ) 是由 王卓 黄炯 全伟 段利红 范文峰 张伟佳 于 2020-10-23 设计创作，主要内容包括：一种基于光频移操控的闭环原子自旋陀螺仪,利用频率失谐的圆偏振或椭圆偏振激光作用碱金属原子,通过控制碱金属电子感受的光频移操控电子自旋进动,实现原子自旋陀螺输出的闭环检测,有效抑制由抽运光功率、检测光功率频率波动以及放大器增益波动引入的标度因数误差,提高陀螺信号的长期稳定性。(A closed-loop atomic spin gyroscope based on optical frequency shift control utilizes frequency-detuned circularly polarized or elliptically polarized laser to act on alkali metal atoms, controls electron spin precession by controlling optical frequency shift sensed by alkali metal electrons, realizes closed-loop detection of output of the atomic spin gyroscope, effectively inhibits scale factor errors introduced by pumping optical power, detecting optical power frequency fluctuation and amplifier gain fluctuation, and improves long-term stability of gyroscope signals.)

1. A closed-loop atomic spin gyroscope based on optical frequency shift control is characterized by comprising an atomic gas chamber with a non-magnetic temperature control system, a magnetic shielding system with magnetic compensation, an optical pumping system, an optical rotation angle detection system and an optical frequency shift control system; the non-magnetic temperature control system heats the atomic gas chamber to the working temperature of the alkali metal atoms; the magnetic shielding system comprises an active magnetic compensation coil and a passive magnetic shielding cylinder, and is used for providing a magnetic shielding environment for the alkali metal atoms so as to inhibit spin exchange relaxation of alkali metal electron spin; the optical pumping system is used for generating pumping laser beams along the z-axis direction, the pumping laser beams are circularly polarized light with stable frequency and power and are used for polarizing alkali metal electron spin, and then the hyperpolarization of the inert gas nuclear spin is realized through spin exchange collision between the polarized alkali metal electron spin and the inert gas nuclear spin, and the polarization directions of the alkali metal electron spin and the inert gas nuclear spin are along the z-axis direction; the optical rotation angle detection system is used for generating a detection laser beam along the y-axis direction, the detection laser beam is linearly polarized light, and the precession angle of the alkali metal electron spin is detected through an optical rotation effect; the optical frequency shift control system is used for generating an optical frequency shift light beam along the direction of an x axis, the x axis is an angular rate sensitive axis, the optical frequency shift light beam is circularly polarized light with detuned frequency, the electronic spin precession is controlled through an optical frequency shift effect, the electronic spin precession caused by inertial rotation is counteracted, a gyroscope output signal is closed to a zero position in real time, the rotating angular rate of a measured gyroscope carrier is determined according to the applied optical frequency shift, and a signal corresponding to the applied optical frequency shift is used as a finally measured gyroscope output signal, so that the closed-loop detection of a carrier rotation angular rate measured value is realized.

2. The closed-loop atomic spin gyroscope based on optical frequency shift manipulation according to claim 1, wherein the optical pumping system comprises a first laser, a first λ/2 wave plate, a first polarization beam splitter prism, a first liquid crystal phase retarder, a first analyzer, a second λ/2 wave plate, a second polarization beam splitter prism and a first λ/4 wave plate which are optically connected in sequence, the first polarization beam splitter prism is connected with the first laser through a frequency stabilization control module, and the second polarization beam splitter prism is connected with the first liquid crystal phase retarder through a power stabilization control module; the second polarization beam splitter prism and the optical axis of the first lambda/4 wave plate form an angle of 45 degrees; the optical axis of the first polarization beam splitter prism is perpendicular to the optical axis of the first polarization analyzer, and the angle between the first polarization beam splitter prism and the optical axis of the first liquid crystal phase retarder is 45 degrees; emergent light of the first lambda/4 wave plate enters the atomic gas chamber; the frequency stabilization control module detects the laser frequency split by the first polarization beam splitter prism and then modulates the current injected by the first laser to realize the locking of the laser frequency; the frequency of a pumping laser beam generated by the optical pumping system is tuned to the alkali metal atom formant, and a saturated absorption method is adopted for frequency locking; the power stabilization control module controls the phase delay amount of the first liquid crystal phase retarder so as to control the laser power attenuation amount to stabilize the laser power.

3. The closed-loop atomic spin gyroscope based on optical frequency shift manipulation according to claim 1, wherein the optical rotation angle detection system comprises a second laser, a first polarizer, a polarization splitting prism and a balanced differential detector which are optically connected in sequence, and the atomic gas cell is located between the first polarizer and the polarization splitting prism; the detection laser generated by the second laser is changed into linearly polarized light through the second polarizer, an optical rotation angle is generated after passing through the atomic gas chamber, and the linearly polarized light enters the balanced differential detector after passing through the polarization beam splitter prism, so that the polarization balanced differential detection of the optical rotation angle is realized; the detection laser frequency output by the second laser is detuned to the resonance peak of the atom so as to reduce the absorption effect of the gas chamber, enhance the optical rotation angle signal and realize the optical rotation angle signal detection under the condition of far detuning.

4. The closed-loop atomic spin gyroscope based on optical frequency shift manipulation according to claim 1, wherein the optical frequency shift manipulation system comprises a third laser, a second polarizer, a second liquid crystal phase retarder, a second analyzer, a liquid crystal polarization rotator, a second λ/4 wave plate, a photodetector and a data acquisition and control module which are optically connected in sequence, and the atomic gas cell is located between the second λ/4 wave plate and the photodetector; linearly polarized light emitted by the liquid crystal polarization rotator forms an angle of 45 degrees with the optical axis of the second lambda/4 wave plate; the optical axes of the second polarizer and the second analyzer are vertical, and the angle between the second polarizer and the second liquid crystal phase delay optical axis is 45 degrees; the circularly polarized light frequency generated by the optical frequency shift control system is detuned from the resonance peak of the atom so as to generate obvious optical frequency shift effect and smaller optical pumping effect; the data acquisition and control module controls the phase delay amount of the second liquid crystal phase delayer and the polarization rotation amount of the liquid crystal polarization rotator through 2KHz square wave signals, and acquires an optical rotation angle detection signal of the balanced differential detector and an optical frequency shift detection signal output by the photoelectric detector through the analog-to-digital converter.

5. The closed-loop atomic spin gyroscope based on optical frequency shift manipulation as claimed in claim 1, wherein the alkali metal atoms and the inert gas are K-Rb-²¹Ne、Cs-Rb-²¹Ne、K-³He or Cs-¹²⁹Xe。

6. The closed-loop atomic spin gyroscope based on optical frequency shift manipulation as claimed in claim 1, wherein the data acquisition and control module controls the optical frequency shift according to the laser power controlled by the power stabilization control module, the optical frequency shift acts on the electron spins to generate precession to close the electron spins to the gyroscope zero position in real time, and finally the angular rate signal is indirectly extracted according to the optical frequency shift.

Technical Field

The invention relates to an atomic spin gyroscope technology, in particular to a closed-loop atomic spin gyroscope controlled based on optical frequency shift, which controls the electron spin precession by controlling the optical frequency shift sensed by alkali metal electrons, thereby realizing the closed-loop detection of the gyroscope angular rate.

Background

The atomic spin gyroscope is a novel gyroscope which utilizes the atomic spin ensemble to sense the angular rate in the SERF state, and utilizes the coupling precession characteristic of the alkali metal electron spin and the inert gas nuclear spin in a weak magnetic field, the inert gas nuclear spin senses the angular rate, and the alkali metal electron spin forms an in-situ SERF magnetometer to realize indirect reading of angular rate signals. The SERF atomic spin gyro is essentially a rate gyro, has ultrahigh inertial angular rate measurement sensitivity, and is one of important development directions of ultrahigh-precision inertial navigation for a new generation of motion carrier. According to the error transfer relation of the SERF atomic spin gyro, the fluctuation of the pumping laser power can cause the fluctuation of the atomic polarizability, thereby causing the gyro scale factor error; in order to suppress the scale factor error introduced by laser power fluctuation, the traditional method is to realize indirect stable control of main path light beam power by controlling the bypass laser power before entering the air chamber through the feedback of an external actuator, but in weak signal detection, the laser entering the air chamber still has certain fluctuation due to the temperature drift of a light splitting device and the like, thereby affecting the stability of gyro signals. In addition, the additional addition of the external actuator is not beneficial to the integration and miniaturization of the SERF atomic spin gyro.

Disclosure of Invention

Aiming at the defects or shortcomings in the prior art, the invention provides a closed-loop atomic spin gyroscope controlled based on optical frequency shift, which utilizes the action of frequency-detuned circularly polarized or elliptically polarized laser on alkali metal atoms, controls the precession of electron spin by controlling the optical frequency shift sensed by alkali metal electrons, realizes the closed-loop detection of the output of the atomic spin gyroscope, effectively inhibits the scale factor errors introduced by pumping optical power, detecting optical power frequency fluctuation and amplifier gain fluctuation, and improves the long-term stability of gyroscope signals.

The technical scheme of the invention is as follows:

a closed-loop atomic spin gyroscope based on optical frequency shift control is characterized by comprising an atomic gas chamber A without a magnetic temperature control system, a magnetic shielding system B with magnetic compensation, an optical pumping system C, an optical rotation angle detection system D and an optical frequency shift control system E; the non-magnetic temperature control system heats the atomic gas chamber to the working temperature of the alkali metal atoms; the magnetic shielding system B comprises an active magnetic compensation coil and a passive magnetic shielding cylinder and is used for providing a magnetic shielding environment for the alkali metal atoms so as to inhibit spin exchange relaxation of alkali metal electron spin; the optical pumping system C is used for generating a pumping laser beam along the z-axis direction, the pumping laser beam is circularly polarized light with stable frequency and power and is used for polarizing an alkali metal electron spin A1, and then the hyperpolarization of an inert gas nuclear spin A2 is realized through spin exchange collision between the polarized alkali metal electron spin and the inert gas nuclear spin, and the polarization directions of the alkali metal electron spin and the inert gas nuclear spin are along the z-axis direction; the optical rotation angle detection system D is used for generating a detection laser beam along the y-axis direction, the detection laser beam is linearly polarized light, and the precession angle of the alkali metal electron spin A1 is detected through an optical rotation effect; the optical frequency shift control system E is used for generating an optical frequency shift light beam along the direction of an x axis, the x axis is an angular rate sensitive axis, the optical frequency shift light beam is circularly polarized light with detuned frequency, the electronic spin precession is controlled through an optical frequency shift effect, the electronic spin precession caused by inertial rotation is counteracted, a gyro output signal is closed to a zero position in real time, the rotating angular rate of a detected gyro carrier is determined according to the applied optical frequency shift, and a signal corresponding to the applied optical frequency shift is used as a finally detected gyro output signal, so that the closed-loop detection of a carrier rotation angular rate measured value is realized.

The optical pumping system C comprises a first laser C1, a first lambda/2 wave plate C2, a first polarization beam splitter C3, a first liquid crystal phase retarder C4, a first analyzer C5, a second lambda/2 wave plate C6, a second polarization beam splitter C7 and a first lambda/4 wave plate C8 which are sequentially and optically connected, wherein the first polarization beam splitter C3 is connected with the first laser C1 through a frequency stabilization control module C9, and the second polarization beam splitter C7 is connected with the first liquid crystal phase retarder C4 through a power stabilization control module C10; the second polarization beam splitter prism C7 is at an angle of 45 degrees with respect to the optical axis of the first lambda/4 wave plate C8; the optical axes of the first polarization beam splitter prism C3 and the first analyzer C5 are perpendicular to each other, and the optical axis of the first polarization beam splitter prism C3 and the optical axis of the first liquid crystal phase retarder C4 form an angle of 45 degrees; emergent light of the first lambda/4 wave plate C8 enters the atomic gas cell A; the frequency stabilization control module C9 detects the laser frequency split by the first polarization beam splitter prism C3, and then modulates the current injected by the first laser C1 to realize the locking of the laser frequency; the frequency of a pumping laser beam generated by the optical pumping system C is tuned to the alkali metal atom formant, and a saturated absorption method is adopted for frequency locking; the power stabilization control module C10 controls the phase delay amount of the first liquid crystal phase retarder C4 to control the laser power attenuation amount to stabilize the laser power.

The optical rotation angle detection system D comprises a second laser D1, a first polarizer D2, a polarization beam splitter prism D3 and a balanced difference detector D4 which are optically connected in sequence, wherein the atom gas cell A is positioned between the first polarizer D2 and the polarization beam splitter prism D3; the detection laser generated by the second laser D1 is changed into linearly polarized light through the second polarizer D2, generates an optical rotation angle after passing through the atomic gas chamber A, enters the balanced differential detector D4 after passing through the polarization beam splitter prism D3, and realizes polarization balanced differential detection of the optical rotation angle; the detection laser frequency output by the second laser D1 is detuned to the resonance peak of the atom to reduce the absorption of the gas cell, enhance the optical rotation angle signal and realize the optical rotation angle signal detection under the condition of far detuning.

The optical frequency shift control system E comprises a third laser E1, a second polarizer E2, a second liquid crystal phase retarder E3, a second analyzer E4, a liquid crystal polarization rotator E5, a second lambda/4 wave plate E6, a photoelectric detector E7 and a data acquisition and control module E8 which are sequentially and optically connected, wherein the atomic gas cell A is positioned between the second lambda/4 wave plate E6 and the photoelectric detector E7; linearly polarized light emitted by the liquid crystal polarization rotator E5 forms an angle of 45 degrees with the optical axis of the second lambda/4 wave plate E6; the optical axes of the second polarizer E2 and the second analyzer E4 are vertical, and the optical axis of the second polarizer E2 and the optical axis of the second liquid crystal phase delay E3 form an angle of 45 degrees; the circularly polarized light generated by the optical frequency shift control system E is detuned from the resonance peak of the atom so as to generate obvious optical frequency shift effect and smaller optical pumping effect; the data acquisition and control module E8 controls the phase delay amount of the second liquid crystal phase retarder E3 and the polarization rotation amount of the liquid crystal polarization rotator E5 through 2KHz square wave signals, and acquires the optical rotation angle detection signal of the balanced differential detector D4 and the optical frequency shift detection signal output by the photodetector E7 through the analog-to-digital converter.

The alkali metal atom and the inert gas are K-Rb-²¹Ne、Cs-Rb-²¹Ne、K-³He or Cs-¹²⁹Xe。

The data acquisition and control module E8 controls the size of optical frequency shift through the laser power controlled by the power stabilization control module C10, the optical frequency shift acts on the electron spin to make the electron spin generate precession to carry out real-time closed loop to the zero position of the gyroscope, and finally the angular rate signal is indirectly extracted through the size of the optical frequency shift.

The invention has the following technical effects: the invention relates to a closed-loop atomic spin gyroscope based on optical frequency shift control, which consists of an atomic gas chamber, a non-magnetic temperature control system, a magnetic shielding and magnetic compensation system, an optical pumping system, an optical rotation angle detection system and an optical frequency shift control system. The inside of the atomic gas chamber contains alkali metal atoms, inert gas atoms and quenching gas atoms, and is a sensitive core of the atomic spin gyro; the non-magnetic temperature control system and the magnetic shielding magnetic compensation system provide a high-temperature weak magnetic environment for the atomic gas chamber, ensure the pressure density of alkali metal saturated steam to a certain degree, and inhibit the spin exchange relaxation between alkali metal electrons; the optical pumping system realizes the spin polarization of alkali metal electrons and the spin hyperpolarization of noble gas nuclei; the rotation angle detection system realizes electron spin precession detection; the optical frequency shift control system realizes the control of the electron spin precession. When the carrier rotates, the polarized alkali metal electron spin and the inert gas nuclear spin are strongly coupled to generate precession, the electron spin precession is controlled in real time by changing optical frequency shift, the closed-loop detection of the optical rotation angle is realized by weak signal feedback compensation, the gyroscope output is closed to a zero position in real time, and the applied optical frequency shift reflects the rotation angle rate of the carrier. The invention can realize the closed-loop detection of the rotation angular rate of the carrier, effectively inhibit the pumping laser, detect the gyro scale factor error caused by the laser power frequency fluctuation and the amplifier gain fluctuation, and has important significance for improving the long-term stability of gyro signals.

Compared with the prior art, the invention has the advantages that: the frequency detuning circular polarization or elliptical polarization laser is used for carrying out electron spin control on the optical frequency shift effect generated by electron spin, closed-loop detection of the output of the atomic spin gyro is realized, scale factor errors caused by pumping light power, detecting light power frequency fluctuation and amplifier gain fluctuation can be effectively inhibited, and the long-term stability of gyro signals is improved.

The principle of the invention is illustrated as follows: the detuned circular polarization or elliptical polarization light acts on the alkali metal electron spin to generate the light frequency shift effect, the light frequency shift can be equivalent to a virtual magnetic field to cause the alkali metal electron spin precession, but the virtual magnetic field cannot cause the inert gas nuclear spin precession, so that the independent control of the electron spin can be realized. The inertial rotation of the carrier drives the magnetic field and the optical field to rotate, and the coupled precession of electron spin and nuclear spin is caused. In a steady state, the precession angle of electron spin is in direct proportion to the rotation angle rate, the precession angle of the electron spin can cause the linearly polarized light polarization plane to rotate, a precession signal of the electron spin is extracted by a polarization balance differential optical rotation angle detection method, the difference value between the precession signal and the zero position of the gyroscope is used as an error signal, a PID control algorithm is used for generating a control law, a control voltage signal is generated by an analog-to-digital converter, the size of generated optical frequency shift is controlled, the electron spin is controlled, the precession of the electron spin caused by inertial rotation is counteracted, the gyroscope output is closed to the zero position in real time, and the applied optical frequency shift is in direct proportion to the rotation angle rate and serves.

Drawings

Fig. 1 is a general system block diagram of a closed-loop atomic spin gyroscope based on optical frequency shift control according to the present invention.

FIG. 2 is a block diagram of a closed-loop atomic spin gyro pumping system based on optical frequency shift control according to the present invention.

Fig. 3 is a block diagram of an optical rotation angle detection system and an optical frequency shift control system of a closed-loop atomic spin gyroscope based on optical frequency shift control according to the present invention.

FIG. 4 is a block diagram of a gyro output closed loop control.

The reference numbers are listed below: a-an atomic gas chamber with a non-magnetic temperature control system, B-a magnetic shielding system with magnetic compensation, a C-optical pumping system, a D-optical rotation angle detection system, an E-optical frequency shift control system, A1-electron spin, A2-nuclear spin, C1-a first laser, a C-2 first lambda/2 wave plate, C3-a first polarization beam splitter prism, C4-a first liquid crystal phase retarder, C5-a first analyzer, C6-a second lambda/2 wave plate, C7-a second polarization beam splitter prism, C8-a first lambda/4 wave plate, C9-a frequency stabilization control module, C10-a power stabilization control module, D1-a second laser, D2-a first polarizer, D3-a polarization beam splitter prism, D4-a balance differential detector, e1-a third laser, E2-a second polarizer, E3-a second liquid crystal phase retarder, E4-a second analyzer, E5-a liquid crystal polarization rotator, E6-a second lambda/4 wave plate, E7-a photodetector and E8-a data acquisition and control module.

Detailed Description

The invention is described below with reference to the accompanying drawings (fig. 1-4).

Referring to fig. 1 to 4, a closed-loop atomic spin gyroscope based on optical frequency shift control includes an atomic gas chamber, a nonmagnetic temperature control system a, a magnetic shielding and compensation system B, an optical pumping system C, an optical rotation angle detection system D, and an optical frequency shift control system E; the atomic gas chamber is filled with alkali metal and inert gas, and the atomic gas chamber of the embodiment of the invention selects K-Rb-²¹Ne，Cs-Rb-²¹Ne，K-³He or Cs-¹²⁹Xe, and the like, single alkali metal or multi-component mixed gas cells. The non-magnetic temperature control system heats the air chamber to the atomic working temperature; the magnetic shielding and magnetic compensation system B consists of an active magnetic compensation coil and a passive magnetic shielding cylinder and is used for providing a weak magnetic environment for alkali metal atoms and inhibiting spin exchange relaxation of alkali metal electron spin; the optical pumping system C is used for generating pumping laser beams along the z-axis direction, the pumping laser beams are circularly polarized light with stable frequency and power, and are used for polarizing the alkali metal electron spin A1 and then polarizing the electron spin and the nuclear spinThe spin exchange collision between spins realizes the hyperpolarization of the noble gas nuclear spin A2, the polarization direction is along the z-axis direction; the optical rotation angle detection system D is used for generating a detection laser beam along the y-axis direction, the detection laser beam is linearly polarized light, and the precession angle of the electron spin A1 is detected through an optical rotation effect; the optical frequency shift control system E is used for generating optical frequency shift light beams along the direction of an x axis, the x axis is an angular rate sensitive axis, the optical frequency shift light beams are circularly polarized light with detuned frequency, the electronic spin precession is controlled through an optical frequency shift effect, the electronic spin precession caused by inertial rotation is counteracted, the gyroscope output is closed to a zero position in real time, and the applied optical frequency shift is in direct proportion to the rotation angular rate and serves as the final system output.

Fig. 2 is a block diagram of a closed-loop atomic spin gyro pumping system based on optical frequency shift control according to the present invention. The optical pumping system C comprises a first laser C1, a first lambda/2 wave plate C2, a first polarization beam splitter C3, a first liquid crystal phase retarder C4, a first analyzer C5, a second lambda/2 wave plate C6, a second polarization beam splitter C7, a first lambda/4 wave plate C8, a frequency stabilization control module C9 and a power stabilization control module C10 which are optically connected in sequence; the second polarization beam splitter prism C7 is at an angle of 45 degrees with the optical axis of the first lambda/4 wave plate C8; the optical axes of the first polarization beam splitter prism C3 and the first analyzer C5 are mutually vertical and form an angle of 45 degrees with the optical axis of the first liquid crystal phase retarder C4; the optical axes of the second polarizer E2 and the second analyzer E4 are vertical, and form an angle of 45 degrees with the optical axis of the second liquid crystal phase delay E3; the frequency stabilization control module C9 detects the laser frequency split by the first polarization splitting prism C3 by using a saturated absorption atomic gas cell and a low-noise photoelectric detector, and then modulates the current injected by the first laser C1 to realize the locking of the laser frequency. The frequency of the pumping laser beam is tuned to an atomic resonance peak, and the frequency locking is carried out by adopting a saturation absorption method. The first polarization beam splitter prism C3 and the second polarization beam splitter prism C7 are PBS polarization beam splitter prisms or glan polarization beam splitter prisms.

Fig. 3 is a block diagram of a closed-loop atomic spin gyroscope optical rotation angle detection system and an optical frequency shift control system based on optical frequency shift control according to the present invention. The optical rotation angle detection system D comprises a second laser D1, a first polarizer D2, a polarization beam splitter D3 and a balance difference detector D4 which are optically connected in sequence; the detection laser generated by the second laser D1 is changed into linearly polarized light through the second polarizer D2, generates an optical rotation angle after passing through the atomic gas chamber A, enters the balanced differential detector D4 after passing through the polarization beam splitter prism D3, and realizes polarization balanced differential detection of the optical rotation angle; the detection laser frequency output by the second laser D1 is detuned to the resonance peak of the atom to reduce the absorption of the gas chamber, enhance the optical rotation angle signal and realize the optical rotation angle signal detection under the condition of far detuning; the polarization beam splitter D3 may be a PBS polarization beam splitter or a wollaston polarization beam splitter. The optical frequency shift control system E comprises a third laser E1, a second polarizer E2, a second liquid crystal phase retarder E3, a second analyzer E4, a liquid crystal polarization rotator E5, a second lambda/4 wave plate E6, a photoelectric detector E7 and a data acquisition and control module E8 which are sequentially and optically connected; the linearly polarized light emitted by the liquid crystal polarization rotator E5 forms an angle of 45 degrees with the optical axis of the second lambda/4 wave plate (E6); the circularly polarized light generated by the optical frequency shift control system E is detuned from the resonance peak of the atom so as to generate obvious optical frequency shift effect and smaller optical pumping effect; the data acquisition and control module E8 controls the phase delay amount of the second liquid crystal phase retarder E3 and the polarization rotation amount of the liquid crystal polarization rotator E5 through 2KHz square wave signals, and acquires voltage signals output by the balanced differential detector D4 and the photoelectric detector E7 through the analog-to-digital converter; the liquid crystal polarization rotator E5 can realize rotation of the polarization direction of linearly polarized light by 0 ° or 90 ° through switch control.

In operation, the first laser C1 is turned on first, the polarized light beam generated by the optical pumping system polarizes the alkali metal electron spin a1, and then the hyperpolarization of the noble gas nuclear spin a2 is realized by spin-exchange collision between the polarized electron spin and the nuclear spin, with the polarization direction along the pumping laser beam direction (z-axis direction). And then the second laser D1 is turned on, at the moment, the third laser E1 is in a closed state, the second laser D1 generates a detection laser beam (along the y-axis direction), the detection laser beam is changed into linearly polarized light through the second polarizer D2, an optical rotation angle is generated after the detection laser beam passes through the atomic gas chamber A, the linearly polarized light passes through the polarization beam splitter prism D3 and enters the balanced differential detector D4 to realize the polarization balance differential detection of the optical rotation angle, the gyroscope is in an open loop state, a spinning self-compensation point (a z-axis magnetic field compensation point) of the gyroscope nuclear spin is found by adopting a cross modulation method, the remanence in the gyroscope magnetic shielding cylinder is compensated to zero, so that the alkali metal electron spin works in a weak magnetic field environment, and a non-spin exchange relaxation state.

Turning on the third laser E1, detuning the outgoing laser frequency to a suitable position, adjusting the laser power by a power attenuator, changing the laser frequency by tuning the current of the third laser E1, finding the linear relationship between the optical power and frequency and the angle of optical rotation, at which time the optical frequency shiftsThe relationship with laser frequency, power and polarization state is:

in the formula, phi (v) is photon flux which is in direct proportion to the power of the light beam, v is the central frequency of the light beam, and r is_eIs the electron radius, c is the speed of light, f_D1The transition oscillator intensity of D1 line, A is the cross-sectional area of light beam, gamma^eV is the spin-to-spin ratio of electrons_D1V and v_D2Transition center frequencies, Γ, of the alkali metal atoms D1 and D2 lines, respectively_D1And Γ_D2Half-height and half-width of the lines of the alkali metal atoms D1 and D2 respectively,the degree of circular polarization of the light beam.

The electron spin and nuclear spin dynamics evolution process can be described by a Bloch equation after small-angle linearization, and the steady state solution of the linearized Bloch equation can be obtained by solving the following steps:

in the formulaWhich is a projection of the electron spin polarizability in the z-direction,as electron spin relaxation rate, gammaⁿIs the nuclear spin gyromagnetic ratio, Q is the slowing factor, Ω_xAngular rate of rotation, L, of x-axis input_xIs the applied optical frequency shift in the x-axis direction.

By varying the frequency shift L of the applied light_xCounteracting the rotation angular rate omega_xFor precession generated by electron spin, detecting projection of electron polarizability in y-axis direction by using optical rotation effectAnd the detected optical rotation signal is differed from the zero position of the gyroscope to generate an error signal, the gyroscope output is closed to the zero position in real time through a PID control algorithm, a closed-loop control block diagram is shown in figure 4, a control target of a control system is to control an atomic spin ensemble to a desired gyroscope output zero point, the detection of the electronic spin polarization rate is realized by using an optical rotation angle detection technology, the difference between the detection signal and the gyroscope zero point generates the error signal, a controller controls the size of optical frequency shift generated by an actuator (laser), so that the atomic spin ensemble is controlled to the gyroscope output zero point, and the projection of the electronic polarization rate in the y-axis directionThe resulting optical rotation angle θ is expressed as:

wherein l is the length of the gas chamber through which the detection light passes, n is the atomic density, f_D2The D2 line transition element strength.

The detection output expression of the polarization balance differential optical rotation angle is as follows:

U＝A_iuI₀sin(2θ) (4)

in the formula A_iuIs amplifier gain, I₀To detect optical power.

After the system output rotation angle is closed to the zero position in real time by applying optical frequency shift, as can be seen from equations (2), (3) and (4), the magnitude of the applied optical frequency shift is proportional to the angular velocity of the carrier rotation, and can be used as a measure of the angular velocity, and the measure is independent of the detected optical power, the pumped optical power and the amplifier gain. Compared with open loop detection, the method can inhibit scale factor errors caused by detection optical power, pumping optical power and amplifier gain fluctuation, and improve the long-term stability of the gyroscope.

A closed-loop atomic spin gyroscope based on optical frequency shift control comprises an atomic gas chamber, a nonmagnetic temperature control system A, a magnetic shielding and magnetic compensation system B, an optical pumping system C, an optical rotation angle detection system D and an optical frequency shift control system E; the atomic gas chamber is filled with alkali metal and inert gas, and the nonmagnetic temperature control system heats the gas chamber to the atomic working temperature; the magnetic shielding and magnetic compensation system B consists of an active magnetic compensation coil and a passive magnetic shielding cylinder and is used for providing a weak magnetic environment for alkali metal atoms and inhibiting spin exchange relaxation of alkali metal electron spin; the optical pumping system C is used for generating pumping laser beams along the z-axis direction, the pumping laser beams are circularly polarized light with stable frequency and power and used for polarizing the alkali metal electron spin A1, and then the hyperpolarization of the inert gas nuclear spin A2 is realized through spin exchange collision between the polarized electron spin and the nuclear spin, and the polarization direction is along the z-axis direction; the optical rotation angle detection system D is used for generating a detection laser beam along the y-axis direction, the detection laser beam is linearly polarized light, and the precession angle of the electron spin A1 is detected through an optical rotation effect; the optical frequency shift control system E is used for generating optical frequency shift light beams along the direction of an x axis, the x axis is an angular rate sensitive axis, the optical frequency shift light beams are circularly polarized light with detuned frequency, the electronic spin precession is controlled through an optical frequency shift effect, the electronic spin precession caused by inertial rotation is counteracted, the gyroscope output is closed to a zero position in real time, and then the optical frequency shift control system E is used as final system output according to the direct proportion relation between the applied optical frequency shift and the angular rate.

The optical pumping system C comprises a first laser C1, a first lambda/2 wave plate C2, a first polarization beam splitter prism C3, a first liquid crystal phase retarder C4, a first analyzer C5, a second lambda/2 wave plate C6, a second polarization beam splitter prism C7, a first lambda/4 wave plate C8, a frequency stabilization control module C9 and a power stabilization control module C10 which are optically connected in sequence; the second polarization beam splitter prism C7 is at an angle of 45 degrees with respect to the optical axis of the first lambda/4 wave plate C8; the optical axes of the first polarization beam splitter prism C3 and the first analyzer C5 are mutually vertical and form an angle of 45 degrees with the optical axis of the first liquid crystal phase retarder C4; the optical axes of the second polarizer E2 and the second analyzer E4 are vertical, and form an angle of 45 degrees with the optical axis of the second liquid crystal phase delay E3; the pumping laser beam frequency is tuned to the atomic resonance peak and frequency locking is performed by a saturated absorption method (frequency stabilization control module C9). The frequency stabilization control module C9 detects the laser frequency split by the first polarization splitting prism C3 by using a saturated absorption atomic gas cell and a low-noise photoelectric detector, and then modulates the current injected by the first laser C1 to realize the locking of the laser frequency. The power stability control module C10 detects the laser split by the second polarization beam splitter prism C7 through a photoelectric detector, and controls the phase delay amount of the first liquid crystal phase retarder C4 through a 2KHz square wave signal so as to realize the control of the laser power attenuation amount;

the first polarization beam splitter prism C3 and the second polarization beam splitter prism C7 are PBS polarization beam splitter prisms or glan polarization beam splitter prisms. The optical rotation angle detection system D comprises a second laser D1, a first polarizer D2, a polarization beam splitter D3 and a balance difference detector D4 which are optically connected in sequence; the detection laser generated by the second laser D1 is changed into linearly polarized light through the second polarizer D2, generates an optical rotation angle after passing through the atomic gas chamber A, enters the balanced differential detector D4 after passing through the polarization beam splitter prism D3, and realizes polarization balanced differential detection of the optical rotation angle; the detection laser frequency output by the second laser D1 is detuned to the resonance peak of the atom to reduce the absorption of the gas chamber, enhance the optical rotation angle signal and realize the optical rotation angle signal detection under the condition of far detuning; the polarization beam splitter prism D3 can be a PBS polarization beam splitter prism or a Wollaston polarization beam splitter prism. The optical frequency shift control system E comprises a third laser E1, a second polarizer E2, a second liquid crystal phase retarder E3, a second analyzer E4, a liquid crystal polarization rotator E5, a second lambda/4 wave plate E6, a photoelectric detector E7 and a data acquisition and control module E8 which are sequentially and optically connected; the light is emitted through a liquid crystal polarization rotator E5Is at an angle of 45 DEG to the optical axis of the second lambda/4 plate (E6); the circularly polarized light generated by the optical frequency shift control system E is detuned from the resonance peak of the atom so as to generate obvious optical frequency shift effect and smaller optical pumping effect; the data acquisition and control module E8 controls the phase delay amount of the second liquid crystal phase retarder E3 and the polarization rotation amount of the liquid crystal polarization rotator E5 through 2KHz square wave signals, and acquires voltage signals output by the balanced differential detector D4 and the photoelectric detector E7 through the analog-to-digital converter; the liquid crystal polarization rotator E5 can realize the rotation of the polarization direction of linearly polarized light by 0 degrees or 90 degrees through switch control. The atomic gas chamber is selected from K-Rb-²¹Ne，Cs-Rb-²¹Ne，K-³He or Cs-¹²⁹Xe, and the like, single alkali metal or multi-component mixed gas cells. The power stability control module C10 and the data acquisition and control module E8 are composed of a digital controller, an analog-to-digital converter and a digital-to-analog converter, and the analog-to-digital converter and the digital-to-analog converter are respectively connected with the digital controller; the power stabilization control module C10 controls the phase delay amount of the first liquid crystal phase retarder C4 through a PI control algorithm so as to control the laser power attenuation amount to realize stable laser power control. The data acquisition and control module E8 controls the size of the optical frequency shift by controlling the size of the laser power through the power stability control module, the optical frequency shift acts on the electron spin to make the electron spin generate precession to carry out real-time closed loop to the zero position of the gyroscope, and finally the angular rate signal is indirectly extracted through the size of the optical frequency shift. The frequency stabilization control module C9 is composed of a saturated absorption atom air chamber, a photoelectric detector and a frequency locking circuit and realizes frequency stabilization control in a saturated absorption mode.

Those skilled in the art will appreciate that the invention may be practiced without these specific details. Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, and various changes may be made apparent to those skilled in the art as long as they are within the spirit and scope of the present invention as defined and defined by the appended claims, and all matters of the invention which utilize the inventive concepts are protected.