A fast optimization method for pumping optical power of SERF gyroscope

Abstract

The invention discloses a method for rapidly optimizing the pumping light power of a SERF gyroscope, and belongs to the technical field of atomic gyroscopes. The method firstly uses the cross-modulation compensation technology to make the gyroscope work in a nuclear spin self-compensation state, then applies a sinusoidal alternating magnetic field of fixed frequency and amplitude on the x-axis, and locks the system output of the gyroscope in real time through a phase-locked amplifier to obtain a first harmonic signal output by the system, and finally quickly changes the size of the pumping light power to maximize the first harmonic signal output by the system, and the pumping light power at this time is the pumping light power point with the strongest system signal. The method can make the SERF atomic spin gyroscope work at the pumping light power point with the strongest signal in a very short time without causing relaxation of the SERF atomic spin gyroscope, and has important significance for the engineering application of the SERF atomic spin gyroscope.

Description

Technical Field

[0001] The invention belongs to the technical field of atomic gyroscopes, and in particular to an optical pumping technology for atomic spin gyroscopes, and in particular to a method for rapidly optimizing the pumping optical power of a SERF gyroscope, which can be used to rapidly find the pumping optical power operating point with the strongest signal of the SERF atomic spin gyroscope. Background Art

[0002] The atomic spin gyroscope based on spin-exchange relaxation-free (SERF) has an ultra-high theoretical angular velocity measurement sensitivity, which can reach SERF gyroscopes not only have ultra-high theoretical angular velocity measurement sensitivity, but also have the potential for engineering, and have become one of the important development directions of new inertial technology measurement technology. In addition, SERF atomic spin gyroscopes are also widely used in basic physics research, especially in charge parity time symmetry breaking and anomalous interaction force detection.

[0003] The research on SERF atomic spin gyroscope is of great significance in inertial navigation and the exploration of cutting-edge physical problems. Before the SERF atomic spin gyroscope works, it is necessary to use pump laser to polarize alkali metal atoms, and alkali metal atoms hyperpolarize inert gas atoms through spin exchange collision. The signal strength of the SERF atomic spin gyroscope is related to the size of the pump light power, and the pump light power needs to be optimized. The pump light power is closely related to the polarization state of the atomic system. The current pump light power optimization method needs to wait for the system to re-hyperpolarize to reach a steady state after changing the pump light power, and find the light power operating point corresponding to the maximum signal-to-noise ratio of the system after traversing the pump light power. It is time-consuming and difficult to operate, which is very unfavorable for the subsequent engineering application of SERF atomic spin gyroscope, and greatly limits the further development of SERF atomic spin gyroscope. Therefore, it has become an urgent problem to be solved in gyroscope research to quickly find the pump light power operating point with the strongest signal of SERF atomic spin gyroscope and promote the engineering application of SERF atomic spin gyroscope. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for rapidly optimizing the pumping light power of a SERF gyroscope. By real-time locking the amplitude of the first harmonic output by the system after applying a sinusoidal alternating magnetic field of a specific frequency and amplitude on the x-axis, the pumping light power is adjusted to make the SERF atomic spin gyroscope signal the strongest. This method can quickly determine the optimal operating point of the pumping light power when the SERF atomic spin gyroscope output signal is the strongest, which is of great significance to the experimental operation and engineering application of the SERF atomic spin gyroscope.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for rapidly optimizing the pumping optical power of a SERF gyroscope comprises the following steps:

[0007] Step 1: Using the cross-modulation method, the SERF atomic spin gyroscope is operated in a nuclear spin self-compensation state;

[0008] Step 2: fix the SERF atomic spin gyroscope in a stationary state in the inertial space, apply an AC magnetic field with a fixed frequency and amplitude on the x-axis, lock the gyroscope output signal in real time through a phase-locked amplifier, and obtain the first harmonic signal in the system response;

[0009] Step 3, changing the pumping light power to obtain the pumping light power that maximizes the amplitude of the first harmonic signal, that is, the pumping light power that makes the SERF atomic spin gyroscope signal the strongest.

[0010] The beneficial effects of the present invention are:

[0011] The present invention performs rapid optimization of the pumping light power operating point of the SERF atomic spin gyroscope based on the amplitude frequency response of the x-axis AC magnetic field. Since the applied magnetic field is very small and far away from the bandwidth of the SERF atomic spin gyroscope, the SERF atomic spin gyroscope can be operated at the pumping light power point with the strongest signal in a very short time without causing relaxation of the SERF atomic spin gyroscope, which is of great significance to the engineering application of the SERF atomic spin gyroscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of a method for rapidly optimizing pumping optical power of a SERF gyroscope according to the present invention;

[0013] Figure 2 The present invention is a schematic diagram of a system for implementing a method for rapidly optimizing the pumping light power of a SERF gyroscope. DETAILED DESCRIPTION

[0014] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0015] like Figure 1 As shown, the specific implementation steps of the method for rapidly optimizing the pumping optical power of a SERF gyroscope of the present invention are as follows:

[0016] Step 1: At the beginning, the alkali metal gas chamber of the SERF atomic spin gyroscope is heated to the required operating temperature, and the pumping laser is turned on. The pumping laser polarizes the alkali metal atoms, and the alkali metal atoms polarize the inert gas nuclear spins through spin exchange collisions. When the system is polarized to a steady state, the magnetic field cross-modulation compensation technology is used to compensate the magnetic field to determine whether the system is in a "nuclear spin self-compensation" state. If so, the z-axis magnetic field satisfy , the x-axis magnetic field satisfies , the y-axis magnetic field satisfies , execute step 2, otherwise continue to use the "cross-modulation method" to adjust the magnetic field; , , is the coordinate system relative to the inertial space, , , They are , , The magnitude of the magnetic field applied along the three axes, is the nuclear spin self-compensation point, is the electron spin magnetic field generated by the alkali metal atoms, The nuclear spin magnetic field generated by the noble gas atoms.

[0017] Step 2: Fix the SERF atomic spin gyroscope in a stationary state in the inertial space, apply an AC magnetic field with a fixed frequency and amplitude on the x-axis, such as a sinusoidal AC magnetic field with an amplitude of 0.5nT and a frequency of 10Hz (the frequency and amplitude are not fixed and can vary within a certain range), and use a phase-locked amplifier to lock the system output signal in real time to obtain the first harmonic signal in the system response. , which can be expressed as:

[0018] ,

[0019] in, and are the gyromagnetic ratio of the electron spin of the alkali metal atom and the gyromagnetic ratio of the nuclear spin of the inert gas atom, is the electron spin polarization of the alkali metal atom, is the Fermi contact coefficient, is the Fermi contact constant, and are the magnetization intensities of alkali metal atoms and noble gas atoms, is the slowing factor, is the transverse relaxation rate of alkali metal atom electrons, where is the pumping rate, is the electron spin destruction collision relaxation rate, is the electron spin exchange relaxation rate. Since the SERF atomic spin gyroscope is in the “nuclear spin self-compensation” state, Much smaller than , so the above formula can be simplified to:

[0020] ,

[0021] Alkali metal atomic electron spin polarizability Pumping rate The relationship between can be expressed as:

[0022] ,

[0023] in, is the longitudinal relaxation rate of alkali metal atom electrons, and the pumping rate and pump light power The relationship between can be expressed as:

[0024] ,

[0025] in, is the speed of light, is the classical electron radius, is the oscillation intensity, is Planck's constant, is the laser frequency, is the natural resonance frequency of the atom, is the pressure frequency shift of the atomic light absorption curve, is the pressure broadening of the atomic light absorption curve, the intermediate parameter Pumping rate and pump light power The conversion coefficient between the pumping light power The spin polarization rate of the electrons in the alkali metal atoms is and pumping rate Substitute the expression into the first harmonic signal The expression of can be obtained:

[0026] ,

[0027] Step 3: Change the pump light power , so that the first harmonic signal Maximum pump light power , the first harmonic signal Pumping light power Taking partial derivatives we get Right now , we can get:

[0028] ,

[0029] The signal strength of the SERF atomic spin gyroscope can be measured using the calibration factor To express, the larger the scale factor, the stronger the signal, which can be expressed as:

[0030] ,

[0031] in, is the coefficient term in the calibration coefficient that is independent of the pumping light power. The maximum pump light power point is , the scale factor Pumping light power Taking the partial derivative, we get , we can get:

[0032] ,

[0033] As you can see, ,even though The maximum pumping light power point is also the pumping light power operating point that makes the SERF atomic spin gyroscope signal the strongest. That is, by changing the pumping light power, it is constantly determined whether the first harmonic signal output by the system is the maximum. If not, continue to change the pumping light power. If yes, cancel the AC magnetic field applied by the x-axis and the optimization ends.

[0034] like Figure 2 FIG. 1 is a schematic diagram of a system for implementing a method for rapidly optimizing pumping light power of a SERF gyroscope according to the present invention. Figure 2 The invention comprises two layers of Permalloy shielding tubes, one layer of ferrite shielding tubes, a magnetic field coil, an oven and an air chamber, a pumping optical path passing through the air chamber along the Z axis and a detection optical path passing through the air chamber along the X axis. The pumping optical path comprises a pumping laser, a liquid crystal light intensity stabilization controller, a polarization beam splitter prism and a 1 / 4 wave plate. The reflection side of the polarization beam splitter prism is connected to the control system through a photoelectric detector to adjust the control voltage of the liquid crystal light intensity stabilization controller, thereby changing the light intensity of the pumping optical path. The pumping laser is converted into circularly polarized light by the polarization beam splitter prism and the 1 / 4 wave plate to enter the air chamber. The detection optical path comprises a detection laser, a Glan prism, a 1 / 2 wave plate, a Wollaston prism, a differential amplifier, a lock-in amplifier and a data acquisition system. The detection laser is converted into linearly polarized light by a Glan prism and passes through the air chamber. It is then divided into two beams by a 1 / 2 wave plate and a Wollaston prism and enters the differential amplifier to obtain the gyroscope output signal. After the magnetic field is applied to the x-axis, the first harmonic signal in the gyroscope output is locked in real time using a phase-locked amplifier and saved by a data acquisition system.

[0035] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for rapidly optimizing the pumping optical power of a SERF gyroscope, characterized in that: The method comprises the following steps: Step 1: Using the cross-modulation method, the SERF atomic spin gyroscope is operated in a nuclear spin self-compensation state; Step 2: fix the SERF atomic spin gyroscope in a stationary state in the inertial space, apply an AC magnetic field with a fixed frequency and amplitude on the x-axis, lock the gyroscope output signal in real time through a phase-locked amplifier, and obtain the first harmonic signal in the system response; Step 3, changing the pumping light power to obtain the pumping light power that maximizes the amplitude of the first harmonic signal, that is, the pumping light power that makes the SERF atomic spin gyroscope signal the strongest; The step 1 comprises: heating the alkali metal gas chamber of the SERF atomic spin gyroscope to a preset working temperature, turning on the pumping laser, polarizing the alkali metal atoms with the pumping laser, and polarizing the nuclear spins of the inert gas through spin exchange collisions. When the atomic system is polarized to a steady state, a cross-modulation method is used to compensate the magnetic field, so that the SERF atomic spin gyroscope works in a nuclear spin self-compensation state, and the z-axis magnetic field satisfy , the x-axis magnetic field satisfies , the y-axis magnetic field satisfies ,in , , is the coordinate system relative to the inertial space, , , They are , , The magnitude of the magnetic field applied along the three axes, is the nuclear spin self-compensation point, is the electron spin magnetic field generated by the alkali metal atoms, The nuclear spin magnetic field produced by the noble gas atoms; The step 3 comprises: Assume the first harmonic signal It is expressed as: ， in, and are the gyromagnetic ratio of the electron spin of the alkali metal atom and the gyromagnetic ratio of the nuclear spin of the inert gas atom, is the electron spin polarization of the alkali metal atom, is the Fermi contact coefficient, is the Fermi contact constant, and are the magnetization intensities of alkali metal atoms and noble gas atoms, is the slowing factor, is the transverse relaxation rate of alkali metal atom electrons, where is the pumping rate, is the electron spin destruction collision relaxation rate, is the electron spin exchange relaxation rate. The SERF atomic spin gyroscope is in the "nuclear spin self-compensation" state. Much smaller than , simplify the first harmonic signal expression: ， Alkali metal atomic electron spin polarizability Pumping rate The relationship between them is expressed as: ， in, is the longitudinal relaxation rate of alkali metal atom electrons; Pumping rate and pump light power The relationship between them is expressed as: ， in, is the speed of light, is the classical electron radius, is the oscillation intensity, is Planck's constant, is the laser frequency, is the natural resonance frequency of the atom, is the pressure frequency shift of the atomic light absorption curve, is the pressure broadening of the atomic light absorption curve, the intermediate parameter Pumping rate and pump light power The conversion coefficient between the electron spin polarization rate of the alkali metal atom and pumping rate Substitute the expression into the first harmonic signal The expression of , we get: ， The first harmonic signal Pumping light power Taking partial derivatives we get Right now ,get: ， Use scale factor Indicates the signal strength of the SERF atomic spin gyroscope, scale factor The larger it is, the stronger the signal strength is: ， in, is the coefficient term in the calibration coefficient that is independent of the pumping light power. The maximum pump light power point is , the scale factor Pumping light power Taking the partial derivative, we get ,get: ， Even if the first harmonic signal The maximum pumping light power point is also the pumping light power point that makes the SERF atomic spin gyroscope signal the strongest.

2. The method for rapidly optimizing the pumping optical power of a SERF gyroscope according to claim 1, characterized in that: The step 2 includes: keeping the SERF atomic spin gyroscope stationary in the inertial space, applying a sinusoidal AC magnetic field with an amplitude of 0.5nT and a frequency of 10Hz on the x-axis, and using a phase-locked amplifier to lock the system output signal in real time to obtain a first harmonic signal in the system response. .

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