Synchronous closed-loop control method and system for light intensity and frequency of nuclear magnetic resonance gyroscope detection light

Abstract

The invention provides a synchronous closed-loop control method for detecting laser light intensity and frequency by a nuclear magnetic resonance gyroscope, which comprises the following steps of: firstly, detecting laser detection power fluctuation by utilizing a splitting part of a beam splitter prism, and realizing closed-loop stable control on the detection laser power by adjusting injection current of a detection laser tube; secondly, a detection power signal absorbed by the air chamber is extracted through a summation signal of the polarization balance beam splitting detection system, the signal reflects fluctuation of the detection laser frequency, and finally synchronous closed-loop stable control over the detection laser frequency is achieved by adjusting the temperature of a detection laser tube with the signal as a closed-loop feedback signal. The synchronous closed-loop stable control of the nuclear magnetic resonance gyroscope detection laser power and frequency can be realized, the nuclear magnetic resonance gyroscope output signal drift caused by the fluctuation of the detection laser power and frequency is inhibited, and the long-term stability of the gyroscope output signal is improved. By applying the technical scheme provided by the invention, the technical problem that the miniaturization requirement of the nuclear magnetic resonance gyroscope is difficult to meet in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum sensing (nuclear magnetic resonance gyroscope), and in particular to a method and system for synchronous closed-loop control of light intensity and frequency of a nuclear magnetic resonance gyroscope detection light. Background Art

[0002] The nuclear magnetic resonance gyroscope is a type of atomic spin gyroscope that uses the invariance of the magnetic resonance frequency of the nuclear spins of inert gas atoms in inertial space to measure the angular velocity of the carrier. In the nuclear magnetic resonance gyroscope, since it is not easy to directly manipulate the nuclear spin with the light field, the magnetic resonance signal detection of the nuclear spin needs to be indirectly achieved by detecting the precession signal of the electron spin of the alkali metal atom based on the optical rotation effect using a linearly polarized detection laser. In this process, fluctuations in the power and frequency of the detection laser will directly produce magnetic resonance signal detection errors, which will in turn affect the accuracy and stability of the angular velocity measurement of the nuclear magnetic resonance gyroscope. Therefore, it is necessary to perform closed-loop stable control of the power and frequency of the detection laser.

[0003] However, the existing closed-loop control method of laser power and frequency synchronization based on atomic absorption peak by adjusting laser current and temperature (Mu W., Hu Z., Wang J., et al. Intensity and frequency stabilization of a laser diode by simultaneously controlling its temperature and current [C]. Applied Optics and Photonics China (AOPC2017), 2017: 1045728) is only applicable to the power and frequency closed-loop control of the driving laser. For the detection laser, the detection laser frequency needs to be greatly detuned, far away from the atomic absorption peak. Therefore, this method is difficult to achieve stable control of the detuned frequency of the detection laser. The existing laser detuning frequency stabilization method based on the transfer cavity (Zhai Yueyang, Li Xiufei, Quan Wei, etc., A laser dual-frequency stabilization optical path system for SERF atomic inertial measurement device [P]. ZL201910034846.X) and the laser power closed-loop control method based on the optical modulator (Fang Jiancheng, Huang Jiong, Xing Li, etc., A full-optical path light intensity stabilization control system for SERF atomic spin gyroscope [P]. 201710916926.9) require additional optical devices such as FP cavity, electro-optical or acousto-optical, which is difficult to meet the needs of miniaturization of nuclear magnetic resonance gyroscope. Summary of the invention

[0004] The present invention provides a method and system for synchronous closed-loop control of light intensity and frequency of a nuclear magnetic resonance gyroscope detection light, which can solve the technical problem that the existing technology is difficult to meet the demand for miniaturization of the nuclear magnetic resonance gyroscope.

[0005] According to one aspect of the present invention, a method for synchronous closed-loop control of laser light intensity and frequency for detecting a nuclear magnetic resonance gyroscope is provided. The method for synchronous closed-loop control of laser light intensity and frequency for detecting a nuclear magnetic resonance gyroscope comprises: arranging a first half-wave plate, a first polarization beam splitter prism, a polarization-independent beam splitter prism, an alkali metal atom gas chamber, a second half-wave plate, and a second polarization beam splitter prism in sequence along the advancing direction of a light beam emitted by a collimated beam expansion detection laser source; arranging a three-dimensional magnetic field coil and a magnetic shielding cylinder outside the alkali metal atom gas chamber; arranging a first photodetector, a second photodetector, a first operational amplifier, a second operational amplifier, a third photodetector, and a signal processing and control unit; the first photodetector, the second photodetector, the first operational amplifier, and the second operational amplifier constitute a balanced differential summation detector; the first operational amplifier is used to calculate the differential signal between the first photodetector and the second photodetector; and the second operational amplifier is used to calculate the differential signal between the first photodetector and the second photodetector. The polarization-independent beam splitter prism splits a beam of detection laser into the third photodetector, and the second polarization beam splitter prism splits the detection laser after passing through the alkali metal atom gas chamber into two beams, which respectively enter the first photodetector and the second photodetector; the detection laser emitted along the collimated beam expansion detection laser light source is divided into two beams after passing through the first half wave plate, the first polarization beam splitter prism and the polarization-independent beam splitter prism, one beam enters the third photodetector, the third photodetector converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber and enters the balanced differential summation detector, the differential signal is used to detect the atomic spin precession signal, the summation signal reflects the change of the detection light frequency, the summation signal is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

[0006] Furthermore, the relationship between the detection laser power incident into the alkali metal atom gas cell and the detection laser power emitted from the alkali metal atom gas cell separated by the polarization-independent beam splitter prism is:

[0007] I=I0e -nσ (v) L

[0008] Where I0 is the detection laser power before entering the alkali metal atom gas cell, I is the detection laser power emitted through the alkali metal atom gas cell, n is the number density of alkali metal atoms, L is the length of the laser passing through the alkali metal atom gas cell, and σ(ν) is the absorption cross section and satisfies the following formula:

[0009]

[0010] Where ν0 is the resonant absorption frequency of alkali metal atoms, ν-ν0 describes the detuning between the pump laser frequency and the resonant absorption frequency of alkali metal atoms, c is the speed of light, and r is e is the electron radius, f is the oscillator strength, Γ is the spectral line broadening. Under the condition of closed-loop stable control of the detection light intensity and the gas chamber temperature, I0 and n can be approximately constant. Since the detection laser frequency ν is detuned to a certain extent relative to the alkali metal atom resonance absorption frequency ν0, the change of the detection laser power I emitted from the alkali metal atom gas chamber is approximately proportional to the change of the detection laser frequency ν, which can be used to measure the fluctuation of the detection laser frequency and then perform frequency stability control.

[0011] The laser powers of the two beams separated by the polarization beam splitter and entering the first photodetector and the second photodetector can be expressed as:

[0012]

[0013] Where θ is the optical rotation angle generated by the atomic spin precession in the alkali metal atom gas chamber, I9 is ​​the laser power detected by the first photodetector, and I 10 is the laser power detected by the second photodetector. The sum of the laser powers detected by the two detectors is I9+I 10 That is, the detection laser power I emitted from the alkali metal atom gas chamber, which can be used to measure the fluctuation of the detection laser frequency and then perform frequency stability control.

[0014] Furthermore, a non-magnetic electric heating film is arranged outside the alkali metal atom gas chamber, and the alkali metal atom gas chamber contains Rb or Cs alkali metal atoms, buffer gas N2, inert gas atoms, 129 Xe and 131 Xe.

[0015] Furthermore, the wavelength of the laser emitted by the collimated beam expansion detection laser light source 1 is tuned to be detuned by 0.1 to 0.3 nm relative to the wavelength corresponding to the alkali metal atomic absorption line D1.

[0016] Furthermore, the first polarization beam splitter prism 3 is a Glan Taylor polarization prism made of calcite, the second polarization beam splitter prism 8 is a PBS polarization beam splitter prism, and the splitting ratio of the polarization-independent beam splitter prism is 1:1, so as to achieve the best effect of detecting laser power fluctuation monitoring.

[0017] Furthermore, the three-dimensional magnetic field coil and the magnetic shielding tube are composed of a Helmholtz coil and a Permalloy magnetic shielding tube, which provide a necessary magnetic field environment for nuclear spin magnetic resonance.

[0018] Furthermore, the signal processing and control module is composed of a digital signal processor, a digital-to-analog converter and an analog-to-digital converter. The signals output by the third photodetector and the second operational amplifier are converted into digital signals by the analog-to-digital converter. The digital signals enter the digital signal processor for processing to realize filtering processing of the detection laser power and frequency monitoring signals and generation of injection current and temperature PID decoupling control signals of the collimating and expanding beam detection laser source. The current and temperature PID decoupling control signals output by the digital signal processor are converted into analog signals by the digital-to-analog converter and output to the collimating and expanding beam detection laser source, thereby completing the current and temperature control of the collimating and expanding beam detection laser source.

[0019] According to another aspect of the present invention, a closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection is provided, characterized in that the closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection uses the above-mentioned closed-loop control method for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection to perform closed-loop control of laser light intensity and frequency for nuclear magnetic resonance gyroscope detection, and the closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection comprises a collimated beam expansion detection laser light source, a first half-wave plate, a first polarization beam splitter prism, a polarization-independent beam splitter prism, an alkali metal atom gas chamber, a three-dimensional magnetic field coil and a magnetic shielding tube, a second half-wave plate, a second polarization beam splitter prism, a first photodetector, a second photodetector, a first operational amplifier, a second operational amplifier, a third photodetector and a signal processing and control unit; wherein the first photodetector, the second photodetector, the first operational amplifier and the second operational amplifier constitute a parallel A balanced differential summation detector, a first operational amplifier is used to calculate the differential signal between the first photodetector and the second photodetector, and a second operational amplifier is used to calculate the summation signal between the first photodetector and the second photodetector. The detection laser emitted along the collimated beam expansion detection laser light source is divided into two beams after passing through the first half wave plate, the polarization beam splitter prism and the polarization-independent beam splitter prism. One beam enters the third photodetector, and the third photodetector converts the optical signal into an electrical signal and sends it to the signal processing and control unit. The stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber and enters the balanced differential summation detector. The differential signal is used to detect the atomic spin precession signal. The summation signal reflects the change of the detection light frequency. The summation signal is sent to the signal processing and control unit. The synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

[0020] According to another aspect of the present invention, a method for synchronous closed-loop control of laser light intensity and frequency for detecting a nuclear magnetic resonance gyroscope is provided. The method for synchronous closed-loop control of laser light intensity and frequency for detecting a nuclear magnetic resonance gyroscope comprises: arranging a first half-wave plate, a first polarization beam splitter prism, a first polarization-independent beam splitter prism, an alkali metal atom gas chamber, a second half-wave plate, a second polarization-independent beam splitter prism, and a second polarization beam splitter prism in sequence along the advancing direction of a light beam emitted from a collimated beam expansion detection laser source; arranging a three-dimensional magnetic field coil and a magnetic shielding cylinder outside the alkali metal atom gas chamber; arranging a first photodetector, a second photodetector, an operational amplifier, a third photodetector, a fourth photodetector, and a signal processing and control unit; the operational amplifier is used to calculate a differential signal between the first photodetector and the second photodetector; the differential signal is used to detect an atomic spin precession signal; the first polarization-independent beam splitter prism splits a beam of detection laser into the third photodetector; The detector comprises a second polarization beam splitter prism which splits the detection laser after passing through the alkali metal atom gas chamber into two beams which enter the first photodetector and the second photodetector respectively; the detection laser emitted along the collimated beam expansion detection laser light source passes through the first half wave plate, the first polarization beam splitter prism and the polarization-independent beam splitter prism and is split into two beams, one beam enters the third photodetector, the third photodetector converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber and enters the fourth photodetector through the second polarization-independent beam splitter prism, the fourth photodetector is used to detect the detection laser power emitted through the alkali metal atom gas chamber, the signal output by the fourth photodetector is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

[0021] According to another aspect of the present invention, a closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection is provided. The closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection uses the above-mentioned closed-loop control method for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection to perform closed-loop control of laser light intensity and frequency for nuclear magnetic resonance gyroscope detection. The closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection comprises a collimated beam expansion detection laser light source, a first half-wave plate, a first polarization beam splitter prism, a first polarization-independent beam splitter prism, an alkali metal atom gas chamber, a three-dimensional magnetic field coil and a magnetic shielding tube, a second half-wave plate, a second polarization-independent beam splitter prism, a fourth photodetector, a second polarization beam splitter prism, a first photodetector, a second photodetector, an operational amplifier, a third photodetector and a signal processing and control unit; the operational amplifier is used to calculate the first The differential signal between the photodetector and the second photodetector is used to detect the atomic spin precession signal. The detection laser emitted along the collimated beam expansion detection laser light source is divided into two beams after passing through the first half-wave plate, the first polarization beam splitter and the first polarization-independent beam splitter. One beam enters the third photodetector, and the third photodetector converts the optical signal into an electrical signal and sends it to the signal processing and control unit. The stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber and enters the fourth photodetector through the second polarization-independent beam splitter. The fourth photodetector is used to detect the detection laser power emitted through the alkali metal atom gas chamber. The signal output by the fourth photodetector is sent to the signal processing and control unit. The synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

[0022] The technical scheme of the present invention is applied to provide a method for synchronous closed-loop control of laser intensity and frequency of nuclear magnetic resonance gyroscope detection. The method firstly uses a split prism to separate part of the detection laser detection power fluctuation, and realizes closed-loop stable control of detection laser power by adjusting the injection current of the detection laser tube. Secondly, the sum signal of the polarization balance beam splitting detection system is used to extract the detection detection power signal after being absorbed by the gas chamber. The signal reflects the fluctuation of the detection laser frequency. Finally, the signal is used as a closed-loop feedback signal to realize synchronous closed-loop stable control of the detection laser frequency by adjusting the temperature of the detection laser tube. The present invention can realize synchronous closed-loop stable control of nuclear magnetic resonance gyroscope detection laser power and frequency, suppress the drift of the nuclear magnetic resonance gyroscope output signal caused by the fluctuation of the detection laser power and frequency, and improve the long-term stability of the gyroscope output signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It shows a schematic structural diagram of a nuclear magnetic resonance gyro detection laser intensity and frequency synchronization closed-loop control system provided in accordance with a first embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the structure of a nuclear magnetic resonance gyro detection laser intensity and frequency synchronization closed-loop control system provided according to a second embodiment of the present invention is shown.

[0026] The above drawings include the following reference numerals:

[0027] 1. Collimated beam expansion detection laser light source; 2. First half wave plate; 3. First polarization beam splitter prism; 4. Polarization-independent beam splitter prism; 5. Alkali metal atom gas chamber; 6. Three-dimensional magnetic field coil and magnetic shielding tube; 7. Second half wave plate; 8. Second polarization beam splitter prism; 9. First photoelectric detector; 10. Second photoelectric detector; 11. Third photoelectric detector; 12. Second polarization-independent beam splitter prism; 13. Fourth photoelectric detector. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0031] like Figure 1As shown, according to the first embodiment of the present invention, a method for synchronous closed-loop control of laser light intensity and frequency for detecting a nuclear magnetic resonance gyroscope is provided. The method for synchronous closed-loop control of laser light intensity and frequency for detecting a nuclear magnetic resonance gyroscope comprises: a first half-wave plate 2, a first polarization beam splitter prism 3, a polarization-independent beam splitter prism 4, an alkali metal atom gas chamber 5, a second half-wave plate 7, and a second polarization beam splitter prism 8 are sequentially arranged along the advancing direction of the light beam emitted by a collimated beam expansion detection laser source 1; a three-dimensional magnetic field coil and a magnetic shielding tube 6 are arranged outside the alkali metal atom gas chamber 5; a first photodetector 9, a second photodetector 10, a first operational amplifier, a second operational amplifier, a third photodetector 11, and a signal processing and control unit are arranged; the first photodetector 9, the second photodetector 10, the first operational amplifier, and the second operational amplifier constitute a balanced differential summation detector; the first operational amplifier is used to calculate the differential signal between the first photodetector 9 and the second photodetector 10; the second operational amplifier is used to calculate the differential signal between the first photodetector 9 and the second photodetector 10; and the third photodetector 11 is used to calculate the differential signal between the first photodetector 9 and the second photodetector 10. The summation signal between the electric detector 10, the polarization-independent beam splitter 4 separates a beam of detection laser into the third photodetector 11, the second polarization beam splitter prism 8 divides the detection laser after passing through the alkali metal atom gas chamber 5 into two beams and enters the first photodetector 9 and the second photodetector 10 respectively; the detection laser emitted along the collimated beam expansion detection laser light source 1 is divided into two beams after passing through the first half wave plate 2, the first polarization beam splitter prism 3 and the polarization-independent beam splitter prism 4, one beam enters the third photodetector 11, the third photodetector 11 converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source 1; the other beam passes through the alkali metal atom gas chamber and enters the balanced differential summation detector, the differential signal is used to detect the atomic spin precession signal, the summation signal reflects the change of the detection light frequency, the summation signal is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source 1.

[0032] By using this configuration, a method for synchronous closed-loop control of laser intensity and frequency of nuclear magnetic resonance gyroscope detection is provided. When the detection laser power fluctuates, the photoelectric detector detects the detection laser detection light power fluctuation signal separated by the polarization-independent beam splitter as a feedback signal to achieve closed-loop stable control of the detection laser power by adjusting the injection current of the laser. At the same time, when the detection laser frequency fluctuates, the detection laser power emitted by the alkali metal atom gas chamber fluctuates, directly representing the fluctuation of the detection laser frequency. The detection laser power fluctuation signal emitted by the alkali metal atom gas chamber is measured by the sum signal of the polarization-balanced beam splitting detection, thereby indirectly achieving the measurement of the detection laser frequency fluctuation, and as a feedback signal, the controlled temperature of the laser is synchronously adjusted to achieve synchronous closed-loop stable control of the detection laser frequency. The system has a simple and compact structure and is easy to operate, which can meet the needs of miniaturization of nuclear magnetic resonance gyroscopes. Therefore, compared with the prior art, the method for synchronous closed-loop control of nuclear magnetic resonance gyro detection laser intensity and frequency provided by the present invention can realize synchronous closed-loop stable control of nuclear magnetic resonance gyro detection laser power and frequency, suppress the drift of nuclear magnetic resonance gyro output signal caused by fluctuations in detection laser power and frequency, and improve the long-term stability of the gyro output signal; the operation is simple and convenient, the system is simple and compact in structure, the detection laser separated by a polarization-independent beam splitter is used as a measurement signal for the detection laser power, the power sum signal of polarization-balanced beam splitting detection is used as a measurement signal for the detection laser frequency, and the synchronous closed-loop control of the detection laser is realized by adjusting the injection current and the controlled temperature of the detection laser.

[0033] Specifically, in the present invention, the relationship between the detection laser power incident into the alkali metal atom gas cell 5 split by the polarization-independent beam splitter 4 and the detection laser power emitted from the alkali metal atom gas cell 5 is:

[0034] I=I0e -nσ (v) L

[0035] Where I0 is the detection laser power before entering the alkali metal atom gas chamber 5, I is the detection laser power emitted through the alkali metal atom gas chamber 5, n is the number density of alkali metal atoms, L is the length of the laser passing through the alkali metal atom gas chamber 5, σ(ν) is the absorption cross section and satisfies the following formula:

[0036]

[0037] Wherein ν0 is the resonance absorption frequency of the alkali metal atom, ν-ν0 describes the detuning amount between the pumping laser frequency and the resonance absorption frequency of the alkali metal atom, Γ is the spectral line broadening, and under the condition of closed-loop stable control of the detection light intensity and the gas chamber temperature, I0 and n can be approximately constant values. Since there is a certain detuning of the detection laser frequency ν relative to the resonance absorption frequency ν0 of the alkali metal atom, the change of the detection laser power I emitted through the alkali metal atom gas chamber 5 is approximately proportional to the change of the detection laser frequency ν, which can be used to measure the fluctuation of the detection laser frequency and then perform frequency stability control;

[0038] The laser powers of the two beams separated by the polarization beam splitter prism 8 and entering the first photodetector 9 and the second photodetector 10 can be expressed as:

[0039]

[0040] Where θ is the optical rotation angle generated by the atomic spin precession in the alkali metal atom gas chamber 5, I9 is ​​the laser power detected by the first photodetector 9, and I 10 is the laser power detected by the second photodetector 10, and the sum of the laser powers detected by the two detectors is I9+I 10 That is, the detection laser power I emitted from the alkali metal atom gas chamber 5, which can be used to measure the fluctuation of the detection laser frequency and then perform frequency stability control.

[0041] Furthermore, in the present invention, a non-magnetic electric heating film is arranged outside the alkali metal atom gas chamber 5, and the alkali metal atom gas chamber 5 contains Rb or Cs alkali metal atoms, buffer gas N2, inert gas atoms, 129 Xe and 131 Xe.

[0042] In addition, in the present invention, the wavelength of the laser emitted by the collimated beam expansion detection laser light source 1 is tuned to be detuned by 0.1 to 0.3 nm relative to the wavelength corresponding to the alkali metal atomic absorption line D1 to ensure that the optical rotation signal generated by the detection light after passing through the gas chamber is the strongest.

[0043] Furthermore, in the present invention, the first polarization beam splitter prism 3 is a Glan Taylor polarization prism made of calcite, and its extinction ratio is better than 10-5, which is used to purify the linear polarization purity of the detection laser emitted by the collimated beam expansion detection laser source 1, and the splitting ratio of the polarization-independent beam splitter prism 4 is 1:1, so as to achieve the best detection laser power fluctuation monitoring effect. The second polarization beam splitter prism 8 uses a PBS polarization beam splitter prism. The three-dimensional magnetic field coil and the magnetic shielding tube 6 are composed of a Helmholtz coil and a Permalloy magnetic shielding tube to provide the necessary magnetic field environment for nuclear spin magnetic resonance.

[0044] In the present invention, the signal processing and control module is composed of a digital signal processor, a digital-to-analog converter and an analog-to-digital converter. The signals output by the third photodetector 11 and the second operational amplifier are converted into digital signals by the analog-to-digital converter. The digital signals enter the digital signal processor for processing to realize filtering processing of the detection laser power and frequency monitoring signals and generation of injection current and temperature PID decoupling control signals of the collimated beam expansion detection laser source 1. The current and temperature PID decoupling control signals output by the digital signal processor are converted into analog signals by the digital-to-analog converter and output to the collimated beam expansion detection laser source 1, thereby completing the current and temperature control of the collimated beam expansion detection laser source 1.

[0045] According to another aspect of the present invention, a closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection is provided. The closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection uses the closed-loop control method for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection as described in the first embodiment to perform closed-loop control of laser light intensity and frequency for nuclear magnetic resonance gyroscope detection. The closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection comprises a collimated beam expansion detection laser light source 1, a first half-wave plate 2, a first polarization beam splitter prism 3, a polarization-independent beam splitter prism 4, an alkali metal atom gas chamber 5, a three-dimensional magnetic field coil and a magnetic shielding tube 6, a second half-wave plate 7, a second polarization beam splitter prism 8, a first photodetector 9, a second photodetector 10, a first operational amplifier, a second operational amplifier, a third photodetector 11 and a signal processing and control unit; wherein the first photodetector 9, the second photodetector 10, the first operational amplifier and the second operational amplifier constitute a balanced Differential summation detector, the first operational amplifier is used to calculate the differential signal between the first photodetector 9 and the second photodetector 10, the second operational amplifier is used to calculate the summation signal between the first photodetector 9 and the second photodetector 10, the detection laser emitted along the collimated beam expansion detection laser light source 1 is divided into two beams after passing through the first half wave plate 2, the first polarization beam splitter prism 3 and the polarization-independent beam splitter prism 4, one beam enters the third photodetector 11, the third photodetector 11 converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source 1; the other beam passes through the alkali metal atom gas chamber 5 and enters the balanced differential summation detector, the differential signal is used to detect the atomic spin precession signal, the summation signal reflects the change of the detection light frequency, the summation signal is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source 1.

[0046] By using this configuration, a closed-loop control system for detecting laser light intensity and frequency of a nuclear magnetic resonance gyroscope is provided. When the detection laser power fluctuates, the photoelectric detector detects the detection laser detection light power fluctuation signal separated by the polarization-independent beam splitter as a feedback signal, and realizes closed-loop stable control of the detection laser power by adjusting the injection current of the laser. At the same time, when the detection laser frequency fluctuates, the detection laser power emitted by the alkali metal atom gas chamber fluctuates, directly representing the fluctuation of the detection laser frequency. The detection laser power fluctuation signal emitted by the alkali metal atom gas chamber is measured by the sum signal of the polarization-balanced beam splitting detection, thereby indirectly realizing the measurement of the detection laser frequency fluctuation, and as a feedback signal, the controlled temperature of the laser is synchronously adjusted to realize the synchronous closed-loop stable control of the detection laser frequency. The system has a simple and compact structure, is easy to operate, and can meet the needs of miniaturization of the nuclear magnetic resonance gyroscope. Therefore, compared with the prior art, the nuclear magnetic resonance gyroscope detection laser intensity and frequency synchronous closed-loop control system provided by the present invention is simple and convenient to operate, the system is simple and compact in structure, the detection laser separated by a polarization-independent beam splitter is used as a measurement signal for detecting laser power, and the power summation signal of polarization-balanced beam splitting detection is used as a measurement signal for detecting laser frequency. The synchronous closed-loop control of the detection laser is achieved by adjusting the injection current and the controlled temperature of the detection laser.

[0047] According to the second embodiment of the present invention, Figure 2As shown, in the present invention, a polarization-independent beam splitter prism and a photodetector can be added before the second polarization beam splitter prism 8. The photodetector is used to detect the power conversion of the detection laser after passing through the gas chamber, instead of extracting the sum signal, and can also realize the extraction of the detection laser frequency fluctuation signal. Specifically, in the second embodiment, the nuclear magnetic resonance gyro detection laser intensity and frequency synchronization closed-loop control method includes: a first half wave plate 2, a first polarization beam splitter prism 3, a first polarization-independent beam splitter prism 4, an alkali metal atom gas chamber 5, a second half wave plate 7, a second polarization-independent beam splitter prism 12, and a second polarization beam splitter prism 8 are sequentially arranged along the advancing direction of the light beam emitted by the collimated beam expansion detection laser source, a three-dimensional magnetic field coil and a magnetic shielding tube 6 are arranged outside the alkali metal atom gas chamber 5, a first photodetector 9, a second photodetector 10, an operational amplifier, a third photodetector 13, a fourth photodetector 13 and a signal processing and control unit are arranged, the operational amplifier is used to calculate the differential signal between the first photodetector 9 and the second photodetector 10, the first polarization-independent beam splitter prism 4 separates a beam of detection laser into the third photodetector 11, and the second polarization beam splitter prism 8 separates the detection laser after passing through the alkali metal atom gas chamber. The laser is divided into two beams and enters the first photodetector 9 and the second photodetector 10 respectively; the detection laser emitted along the collimated beam expansion detection laser light source is divided into two beams after passing through the first half wave plate 2, the first polarization beam splitter prism 3 and the first polarization-independent beam splitter prism 4, one beam enters the third photodetector 11, the third photodetector 11 converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber and enters the fourth photodetector 13 through the second polarization-independent beam splitter prism 12, the differential signal is used to detect the atomic spin precession signal, the fourth photodetector is used to detect the detection laser power emitted through the alkali metal atom gas chamber, the signal output by the fourth photodetector is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

[0048] By using this configuration, a method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope is provided. When the detection laser power fluctuates, the photoelectric detector detects the detection laser power fluctuation signal separated by the first polarization-independent beam splitter as a feedback signal, and realizes closed-loop stable control of the detection laser power by adjusting the injection current of the laser. At the same time, when the detection laser frequency fluctuates, the detection laser power emitted by the alkali metal atom gas chamber fluctuates, directly representing the fluctuation of the detection laser frequency. The fourth photoelectric detector measures the detection laser power fluctuation signal emitted by the alkali metal atom gas chamber, thereby indirectly realizing the measurement of the detection laser frequency fluctuation, and as a feedback signal, realizes synchronous closed-loop stable control of the detection laser frequency by synchronously adjusting the controlled temperature of the laser. The system has a simple and compact structure, is easy to operate, and can meet the needs of miniaturization of the nuclear magnetic resonance gyroscope. Therefore, compared with the prior art, the nuclear magnetic resonance gyroscope detection laser intensity and frequency synchronous closed-loop control system provided by the present invention is simple and convenient to operate, the system is simple and compact in structure, the detection laser separated by the first polarization-independent beam splitter is used as the measurement signal for detecting the laser power, and the power signal detected by the fourth photodetector is used as the measurement signal for detecting the laser frequency, and the synchronous closed-loop control of the detection laser is achieved by adjusting the injection current and the controlled temperature of the detection laser.

[0049] According to another aspect of the present invention, Figure 2As shown, a closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection is provided. The closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection uses the closed-loop control method for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection provided by the second embodiment of the present invention to perform closed-loop control of laser light intensity and frequency for nuclear magnetic resonance gyroscope detection. The closed-loop control system for synchronizing laser light intensity and frequency for nuclear magnetic resonance gyroscope detection includes a collimated beam expansion detection laser light source 1, a first half-wave plate 2, a first polarization beam splitter prism 3, a first polarization-independent beam splitter prism 4, an alkali metal atom gas chamber 5, a three-dimensional magnetic field coil and a magnetic shielding tube 6, a second half-wave plate 7, a second polarization beam splitter prism 8, a first photodetector 9, a second photodetector 10, a third photodetector 11, a signal processing and control unit, a second polarization-independent beam splitter prism 12 and a fourth photodetector 13; an operational amplifier is used to calculate the first photodetector. The differential signal between the detector and the second photodetector is used to detect the atomic spin precession signal. The detection laser emitted along the collimated beam expansion detection laser light source is divided into two beams after passing through the first half wave plate 2, the first polarization beam splitter prism 3 and the first polarization-independent beam splitter prism 4. One beam enters the third photodetector 11, and the third photodetector 11 converts the optical signal into an electrical signal and sends it to the signal processing and control unit. The stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber 5 and enters the fourth photodetector 13 through the second polarization-independent beam splitter prism 12. The fourth photodetector 13 is used to detect the detection laser power emitted through the alkali metal atom gas chamber. The signal output by the fourth photodetector 13 is sent to the signal processing and control unit. The synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

[0050] In order to further understand the present invention, the following Figure 1 The method for synchronous closed-loop control of laser intensity and frequency detection by a nuclear magnetic resonance gyroscope provided in the first embodiment of the present invention is described in detail.

[0051] like Figure 1As shown, a nuclear magnetic resonance gyroscope detection laser power and frequency synchronization closed-loop stable control system, the system includes a collimated beam expansion detection laser light source 1, a first half wave plate 2, a first polarization beam splitter prism 3, a polarization-independent beam splitter prism 4, an alkali metal atom gas chamber 5, a three-dimensional magnetic field coil and a magnetic shielding tube 6, a second half wave plate 7, a second polarization beam splitter prism 8, a first photodetector 9, a second photodetector 10, a third photodetector 11, a first operational amplifier, a second operational amplifier and a signal processing and control unit; wherein the first photodetector 9, the second photodetector 10, the first operational amplifier and the second operational amplifier constitute a balanced differential summation detector, the first operational amplifier is used to calculate the differential signal between the first photodetector 9 and the second photodetector 10, and the second operational amplifier is used to calculate the differential signal between the first photodetector 9 and the second photodetector 10. The device is used to calculate the sum signal between the first photodetector 9 and the second photodetector 10; the detection laser emitted along the collimated beam expansion detection laser light source 1 is divided into two beams after passing through the first half wave plate 2, the polarization beam splitter prism 3 and the polarization-independent beam splitter prism 4, one beam enters the third photodetector 11, the third photodetector 11 converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source 1; the other beam passes through the atomic gas chamber 5 and enters the balanced differential summation detector, the differential signal is used to detect the atomic spin precession signal, the summation signal reflects the change of the detection light frequency, the summation signal is sent to the signal processing and control unit, and the laser tube temperature of the collimated beam expansion detection laser light source 1 is adjusted to achieve the stable control of the detection laser frequency.

[0052] The laser light emitted by the collimated beam expansion detection laser light source 1 is approximately linearly polarized laser light, and the first half-wave plate 2 adjusts its polarization direction to a horizontal polarization direction, which is consistent with the transmission axis direction of the polarization beam splitter prism 3 .

[0053] The second half-wave plate 7 adjusts the polarization direction of the detection laser emitted from the alkali metal atom gas chamber 5 to be nearly 45° with the horizontal direction, and after entering the polarization beam splitter prism 8, it is divided into two beams with nearly equal power, and then differentially summed and detected by the first photodetector 9 and the second photodetector 10.

[0054] The alkali metal atom gas chamber contains Rb or Cs alkali metal atoms, buffer gas N2, and inert gas atoms 129Xe and 131Xe, which are heated to about 120° C. (corresponding to the working temperature of Rb atoms) or about 90° C. (corresponding to the working temperature of Cs atoms) by a non-magnetic electric heating film, so that the gas chamber contains high-density alkali metal atomic vapor;

[0055] The wavelength of the laser emitted by the collimated beam expansion detection laser light source 1 is tuned to be detuned by about 0.1 to 0.3 nm relative to the wavelength corresponding to the alkali metal atomic absorption line D1 to ensure that the optical rotation signal generated by the detection light after passing through the gas chamber is the strongest.

[0056] The detection laser is split into a beam by the polarization-independent beam splitter prism 4 and enters the third photodetector. The splitting ratio of the polarization-independent beam splitter prism 4 is 1:1. The third photodetector 11 converts the optical signal into an electrical signal and sends it to the signal processing and control unit. The injection current of the collimated and expanded detection laser light source 1 is adjusted to achieve stable control of the detection laser power, that is, the power of the other laser beam split by the polarization-independent beam splitter prism 4 and entering the atomic gas chamber is stable.

[0057] The relationship between the detection laser power incident into the alkali metal atom gas cell 5 and the detection laser power emitted from the alkali metal atom gas cell 5 divided by the polarization-independent beam splitter 4 is:

[0058] I=I0e -nσ (v) L

[0059] Where I0 is the detection laser power before entering the alkali metal atom gas chamber 5, I is the detection laser power emitted through the alkali metal atom gas chamber 5), n is the alkali metal atom number density, L is the length of the laser passing through the alkali metal atom gas chamber 5, σ(ν) is the absorption cross section and satisfies the following formula:

[0060]

[0061] Where ν0 is the resonant absorption frequency of alkali metal atoms, ν-ν0 describes the detuning between the pump laser frequency and the resonant absorption frequency of alkali metal atoms, c is the speed of light, and r is e is the electron radius, f is the oscillator strength, and Γ is the line width (full width at half maximum). Under the condition of closed-loop stable control of the detection light intensity and the gas chamber temperature, I0 and n can be approximated to constant values. Since the detection laser frequency ν is detuned to a certain extent relative to the alkali metal atom resonance absorption frequency ν0, within a small range, the change of the detection laser power I emitted through the alkali metal atom gas chamber 5 is approximately proportional to the change of the detection laser frequency ν, which can be used to measure the fluctuation of the detection laser frequency and then perform frequency stability control.

[0062] The laser powers of the two beams separated by the polarization beam splitter prism 8 and entering the first photodetector 9 and the second photodetector 10 can be expressed as:

[0063]

[0064] Wherein θ is the optical rotation angle generated by the atomic spin precession in the alkali metal atom gas chamber 5. The sum of the laser powers detected by the two detectors is the detection laser power I emitted from the alkali metal atom gas chamber 5, which can be used to measure the fluctuation of the detection laser frequency and then perform frequency stability control.

[0065] The position relationship between the nuclear magnetic resonance gyro detection laser power and the frequency synchronization closed-loop stable control system is:

[0066] The direction of the light beam emitted from the collimated expanded beam detection laser source 1 is, in sequence, the first half wave plate 2, the first polarization beam splitter prism 3, the polarization-independent beam splitter prism 4, the alkali metal atom gas chamber 5, the second half wave plate 7, and the second polarization beam splitter prism 8. The polarization-independent beam splitter prism 4 splits a beam of detection laser into the third photodetector 11, and the second polarization beam splitter prism 8 splits the detection laser after passing through the alkali metal atom gas chamber 5 into two beams that respectively enter the first photodetector 9 and the second photodetector 10. The detection laser emitted along the collimated beam expansion detection laser light source 1 is divided into two beams after passing through the first half wave plate 2, the first polarization beam splitter prism 3 and the polarization-independent beam splitter prism 4. One beam enters the third photodetector 11, and the third photodetector 11 converts the optical signal into an electrical signal and sends it to the signal processing and control unit. The stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source 1; the other beam passes through the alkali metal atom gas chamber and enters the balanced differential summation detector composed of the first photodetector 9, the second photodetector 10, the first operational amplifier and the second operational amplifier. The differential signal is used to detect the atomic spin precession signal, and the summation signal reflects the change of the detection light frequency. The summation signal is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source 1.

[0067] The structural diagram of the best embodiment of the present invention is as follows Figure 1 As shown, its specific structure is as follows: the collimated beam expansion detection laser source 1 is a DFB semiconductor laser with a wavelength of 795nm, and the first polarization beam splitter prism 3 is a Glan Taylor polarization prism made of calcite with an extinction ratio better than 10 -5, used to purify the linear polarization purity of the detection laser emitted by the collimated beam expansion detection laser source 1, the splitting ratio of the polarization-independent beam splitter 4 is 1:1, so as to achieve the best detection laser power fluctuation monitoring effect, the second polarization beam splitter prism 8 uses a PBS polarization beam splitter prism, the signal processing and control module is composed of a digital signal processor, a digital-to-analog converter, and an analog-to-digital converter, the third photodetector 11 and the signal output by the second operational amplifier are converted into digital signals by the analog-to-digital converter, and the digital signals enter the digital signal processor for processing to realize the filtering processing of the detection laser power and frequency monitoring signals and the generation of the injection current and temperature PID decoupling control signals of the collimated beam expansion detection laser source (1), the current and temperature PID decoupling control signals output by the digital signal processor are converted into analog signals by the digital-to-analog converter and output to the collimated beam expansion detection laser source (1), and the current and temperature control of the collimated beam expansion detection laser source (1) is completed, and the three-dimensional magnetic field coil and magnetic shielding tube 6 are composed of a Helmholtz coil and a Permalloy magnetic shielding tube, which provide the necessary magnetic field environment for nuclear spin magnetic resonance.

[0068] The working principle of the present invention is as follows:

[0069] When the detection laser power fluctuates, the photodetector 11 uses the detection laser power fluctuation signal separated by the polarization-independent beam splitter 4 as a feedback signal to achieve closed-loop stable control of the detection laser power by adjusting the injection current of the collimated beam expansion detection laser source 1. At the same time, when the detection laser frequency fluctuates, the detection laser power emitted by the alkali metal atom gas chamber 5 fluctuates, which directly represents the fluctuation of the detection laser frequency. The detection laser power fluctuation signal emitted by the alkali metal atom gas chamber 5 is measured by the summation signal of the polarization balanced beam splitting detection, thereby indirectly realizing the measurement of the detection laser frequency fluctuation, and as a feedback signal, the synchronous closed-loop stable control of the detection laser frequency is achieved by synchronously adjusting the controlled temperature of the collimated beam expansion detection laser source 1.

[0070] In summary, the present invention provides a method for synchronous closed-loop control of laser light intensity and frequency for detecting a nuclear magnetic resonance gyroscope. When the detection laser power fluctuates, the photoelectric detector detects the detection laser detection light power fluctuation signal separated by the polarization-independent beam splitter as a feedback signal, and realizes closed-loop stable control of the detection laser power by adjusting the injection current of the laser. At the same time, when the detection laser frequency fluctuates, the detection laser power emitted by the alkali metal atom gas chamber fluctuates, directly representing the fluctuation of the detection laser frequency. The detection laser power fluctuation signal emitted by the alkali metal atom gas chamber is measured by the sum signal of the polarization-balanced beam splitting detection, thereby indirectly realizing the measurement of the detection laser frequency fluctuation, and as a feedback signal, the controlled temperature of the laser is synchronously adjusted to realize the synchronous closed-loop stable control of the detection laser frequency. The system structure is simple and compact, easy to operate, and can meet the needs of miniaturization of the nuclear magnetic resonance gyroscope. Therefore, compared with the prior art, the method for synchronous closed-loop control of laser intensity and frequency detected by a nuclear magnetic resonance gyroscope provided by the present invention is simple and convenient to operate, and the system has a simple and compact structure. The detection laser separated by a polarization-independent beam splitter is used as a measurement signal for detecting laser power, and the power summation signal of polarization-balanced beam splitting detection is used as a measurement signal for detecting laser frequency. The synchronous closed-loop control of the detection laser is achieved by adjusting the injection current and the controlled temperature of the detection laser.

[0071] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0072] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope, characterized in that: The nuclear magnetic resonance gyro detection laser light intensity and frequency synchronous closed-loop control method comprises: A first half-wave plate (2), a first polarization beam splitter prism (3), a polarization-independent beam splitter prism (4), an alkali metal atom gas chamber (5), a second half-wave plate (7) and a second polarization beam splitter prism (8) are sequentially arranged along the advancing direction of a light beam emitted from a collimated beam expansion detection laser source (1); a three-dimensional magnetic field coil and a magnetic shielding cylinder (6) are arranged outside the alkali metal atom gas chamber (5); a first photodetector (9), a second photodetector (10), a first operational amplifier, a second operational amplifier, a third photodetector (11) and a signal processing and control unit are arranged; the first photodetector (9), the second photodetector (10), the first operational amplifier, the second operational amplifier, the third photodetector (11) and a signal processing and control unit are arranged; The operational amplifier and the second operational amplifier constitute a balanced differential summing detector, the first operational amplifier is used to calculate the differential signal between the first photodetector (9) and the second photodetector (10), the second operational amplifier is used to calculate the summing signal between the first photodetector (9) and the second photodetector (10), the polarization-independent beam splitter (4) splits a beam of detection laser light into the third photodetector (11), and the second polarization beam splitter (8) splits the detection laser light after passing through the alkali metal atom gas chamber (5) into two beams that respectively enter the first photodetector (9) and the second photodetector (10); The detection laser emitted from the collimated beam expansion detection laser light source (1) is divided into two beams after passing through the first half wave plate (2), the first polarization beam splitter (3) and the polarization-independent beam splitter (4). One beam enters the third photodetector (11). The third photodetector (11) converts the optical signal into an electrical signal and sends it to the signal processing and control unit. The injection current of the collimated beam expansion detection laser light source (1) is adjusted to achieve stable control of the detection laser power. The other beam passes through the alkali metal atom gas chamber and enters the balanced differential summation detector. The differential signal is used to detect the atomic spin precession signal. The summation signal reflects the change of the detection light frequency. The summation signal is sent to the signal processing and control unit. The synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source (1).

2. The method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope according to claim 1, characterized in that: The relationship between the detection laser power incident into the alkali metal atom gas chamber (5) split by the polarization-independent beam splitter (4) and the detection laser power emitted from the alkali metal atom gas chamber (5) is: I=I0e -nσ (n) L Wherein I0 is the detection laser power before entering the alkali metal atom gas chamber (5), I is the detection laser power emitted from the alkali metal atom gas chamber (5), n is the number density of alkali metal atoms, L is the length of the laser passing through the alkali metal atom gas chamber (5), σ(ν) is the absorption cross section and satisfies the following formula: Where ν0 is the resonant absorption frequency of alkali metal atoms, ν-ν0 describes the detuning between the pump laser frequency and the resonant absorption frequency of alkali metal atoms, c is the speed of light, and r is e is the electron radius, f is the oscillator strength, Γ is the spectral line broadening, under the condition of closed-loop stable control of the detection light intensity and the gas chamber temperature, I0 and n can be approximately constant values, because the detection laser frequency ν is detuned to a certain extent relative to the alkali metal atom resonance absorption frequency ν0, the change of the detection laser power I emitted through the alkali metal atom gas chamber (5) is approximately proportional to the change of the detection laser frequency ν, which can be used to measure the fluctuation of the detection laser frequency and then perform frequency stability control; The laser powers of the two beams separated by the polarization beam splitting prism (8) and entering the first photodetector (9) and the second photodetector (10) can be expressed as: Wherein θ is the optical rotation angle generated by the spin precession of the atoms in the alkali metal atom gas chamber (5), I9 is ​​the laser power detected by the first photodetector (9), and I 10 is the laser power detected by the second photodetector (10), and the sum of the laser powers detected by the two detectors is I9+I 10 That is, the detection laser power I emitted from the alkali metal atom gas chamber (5) can be used to measure the fluctuation of the detection laser frequency and thus perform frequency stability control.

3. The method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope according to claim 1, characterized in that: A non-magnetic electric heating film is arranged outside the alkali metal atom gas chamber (5), and the alkali metal atom gas chamber (5) contains Rb or Cs alkali metal atoms, buffer gas N2, inert gas atoms 129 Xe and 131 Xe.

4. The method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope according to claim 1, characterized in that: The wavelength of the laser emitted by the collimated beam expansion detection laser light source 1 is tuned to be detuned by 0.1 to 0.3 nm relative to the wavelength corresponding to the alkali metal atomic absorption line D1.

5. The method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyro according to claim 4, characterized in that: The first polarization beam splitter prism 3 is a Glan Taylor polarization prism made of calcite, the second polarization beam splitter prism 8 is a PBS polarization beam splitter prism, and the splitting ratio of the polarization-independent beam splitter prism (4) is 1:1, so as to achieve the best effect of detecting laser power fluctuation monitoring.

6. The method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope according to claim 5, characterized in that: The three-dimensional magnetic field coil and magnetic shielding cylinder (6) are composed of a Helmholtz coil and a Permalloy magnetic shielding cylinder, and provide a necessary magnetic field environment for nuclear spin magnetic resonance.

7. The method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope according to claim 6, characterized in that: The signal processing and control module is composed of a digital signal processor, a digital-to-analog converter and an analog-to-digital converter. The signals output by the third photodetector (11) and the second operational amplifier are converted into digital signals by the analog-to-digital converter. The digital signals enter the digital signal processor for processing to achieve filtering of the detection laser power and frequency monitoring signals and generation of injection current and temperature PID decoupling control signals of the collimated beam expansion detection laser source (1). The current and temperature PID decoupling control signals output by the digital signal processor are converted into analog signals by the digital-to-analog converter and output to the collimated beam expansion detection laser source (1), thereby completing current and temperature control of the collimated beam expansion detection laser source (1).

8. A nuclear magnetic resonance gyroscope to detect laser intensity and frequency synchronization closed-loop control system, characterized in that: The nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control system uses the nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control method according to any one of claims 1 to 7 to perform nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control, and the nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control system comprises a collimated beam expansion detection laser light source (1), a first half-wave plate (2), a first polarization beam splitter prism (3), a polarization-independent beam splitter prism (4), an alkali metal atom gas chamber (5), a three-dimensional magnetic field coil and a magnetic shielding tube (6), a second half-wave plate (7), a second polarization beam splitter prism (8), a first photodetector (9), a second photodetector (10), a first operational amplifier, a second operational amplifier, a third photodetector (11) and a signal processing and control unit; wherein the first photodetector (9), the second photodetector (10), the first operational amplifier and the second operational amplifier constitute a balanced differential summation detector, and the first operational amplifier is used to calculate the first photodetector The invention relates to a method for detecting a laser beam from a collimated beam expansion detection laser light source (1) and a detection laser beam from a collimated beam expansion detection laser light source (1). The method comprises the following steps: a first operational amplifier (4) for detecting laser beams from a collimated beam expansion detection laser light source (1) and a second operational amplifier (5) for calculating a sum signal between the first photodetector (9) and the second photodetector (10). The second operational amplifier is used for calculating a sum signal between the first photodetector (9) and the second photodetector (10). The detection laser beam emitted from the collimated beam expansion detection laser light source (1) is divided into two beams after passing through the first half wave plate (2), the polarization beam splitter prism (3) and the polarization-independent beam splitter prism (4). One beam enters the third photodetector (11). The third photodetector (11) converts the optical signal into an electrical signal and sends it to the signal processing and control unit. The injection current of the collimated beam expansion detection laser light source (1) is adjusted to achieve stable control of the detection laser power. The other beam passes through the alkali metal atom gas chamber (5) and enters the balanced differential sum detector. The differential signal is used to detect the atomic spin precession signal. The sum signal reflects the change of the detection light frequency. The sum signal is sent to the signal processing and control unit. The synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source (1).

9. A method for synchronous closed-loop control of laser intensity and frequency for detecting a nuclear magnetic resonance gyroscope, characterized in that: The nuclear magnetic resonance gyro detection laser light intensity and frequency synchronous closed-loop control method comprises: A first half-wave plate, a first polarization beam splitter, a first polarization-independent beam splitter, an alkali metal atom gas chamber, a second half-wave plate, a second polarization-independent beam splitter, and a second polarization beam splitter are sequentially arranged along the advancing direction of the light beam emitted by the collimated beam expansion detection laser source; a three-dimensional magnetic field coil and a magnetic shielding cylinder are arranged outside the alkali metal atom gas chamber; a first photodetector, a second photodetector, an operational amplifier, a third photodetector, a fourth photodetector, and a signal processing and control unit are arranged; the operational amplifier is used to calculate the differential signal between the first photodetector and the second photodetector, and the differential signal is used to detect the atomic spin precession signal; the first polarization-independent beam splitter splits a beam of detection laser into the third photodetector; the second polarization beam splitter splits the detection laser after passing through the alkali metal atom gas chamber into two beams that enter the first photodetector and the second photodetector respectively; The detection laser emitted along the collimated beam expansion detection laser light source is divided into two beams after passing through the first half wave plate, the first polarization beam splitter and the polarization-independent beam splitter, one beam enters the third photodetector, the third photodetector converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber and enters the fourth photodetector through the second polarization-independent beam splitter, the fourth photodetector is used to detect the detection laser power emitted through the alkali metal atom gas chamber, the signal output by the fourth photodetector is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

10. A nuclear magnetic resonance gyroscope to detect laser intensity and frequency synchronization closed-loop control system, characterized in that: The nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control system uses the nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control method as claimed in claim 9 to perform nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control, and the nuclear magnetic resonance gyro detection laser light intensity and frequency synchronization closed-loop control system includes a collimated beam expansion detection laser light source, a first half-wave plate, a first polarization beam splitter prism, a first polarization-independent beam splitter prism, an alkali metal atom gas chamber, a three-dimensional magnetic field coil and a magnetic shielding tube, a second half-wave plate, a second polarization-independent beam splitter prism, a fourth photodetector, a second polarization beam splitter prism, a first photodetector, a second photodetector, an operational amplifier, a third photodetector and a signal processing and control unit; the operational amplifier is used to calculate the differential signal between the first photodetector and the second photodetector, and the differential signal is used to calculate the differential signal between the first photodetector and the second photodetector. For detecting atomic spin precession signals, the detection laser emitted along the collimated beam expansion detection laser light source is divided into two beams after passing through the first half wave plate, the first polarization beam splitter and the first polarization-independent beam splitter, one beam enters the third photodetector, the third photodetector converts the optical signal into an electrical signal and sends it to the signal processing and control unit, and the stable control of the detection laser power is achieved by adjusting the injection current of the collimated beam expansion detection laser light source; the other beam passes through the alkali metal atom gas chamber and enters the fourth photodetector through the second polarization-independent beam splitter, the fourth photodetector is used to detect the detection laser power emitted from the alkali metal atom gas chamber, the signal output by the fourth photodetector is sent to the signal processing and control unit, and the synchronous closed-loop stable control of the detection laser frequency is achieved by adjusting the laser tube temperature of the collimated beam expansion detection laser light source.

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