In-situ adjustment system for angle of pumping light beam of atomic spin inertial measurement device

Abstract

The system is used to adjust the angle of pumping light beam in situ for atomic spin inertial measurement device. The system is based on the fact that the pumping light will polarize the atoms, and the different performance of pumping light beam angle will bring different polarization rate. The system is used to adjust the angle of pumping light beam by using the signal of atomic polarization rate. The system is based on the fact that the atoms feel the change of light field, and it can meet the design requirements and be easy to implement. The system can eliminate the installation error and reduce the light scattering error caused by alkali metal cell, and improve the atomic polarization rate. The system is suitable for atomic spin inertial measurement device and has a very broad application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of atomic spin inertial measurement devices, specifically relating to an in-situ adjustment system for the pump beam angle of an atomic spin inertial measurement device. Background Technology

[0002] In recent years, atomic spin inertial measurement units (ISMs) have become a research frontier, possessing the potential to balance high precision, small size, and relatively easy engineering implementation, thus representing a new development direction for inertial measurement instruments. ISMs require working atoms to have high polarizability, and precise adjustment of the pump beam angle is crucial for improving the polarizability of the working atoms.

[0003] Currently, the main method for adjusting the laser beam angle is to adjust the beam expander lens. For atomic spin inertial measurement devices, traditional pump beam angle adjustment generally involves designing and installing an optical beam expander lens system based on the size of the gas cell. However, in practical applications, on the one hand, lens installation errors result in a non-ideal beam emitted from the beam expander lens system; on the other hand, parallel beams entering the alkali metal gas cell undergo refraction, causing the beam inside the alkali metal gas cell to no longer be parallel, thus reducing atomic polarizability.

[0004] In summary, with the advancements in quantum physics, the design of pump beam angles has broad prospects, but practical research in this area is still relatively lacking. This invention, starting from a holistic perspective, studies an in-situ adjustment system for the pump beam angle of an atomic spin inertial measurement device, which will provide guidance and reference for the design of pump beam angle adjustment in similar atomic spin inertial / magnetic field measurement devices. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of reduced atomic polarizability caused by installation errors in laser beam expansion systems and refraction angle errors in alkali metal gas cells, and to provide an in-situ adjustment system for the pump beam angle of an atomic spin inertial measurement device to improve the accuracy of the beam expansion system.

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

[0007] An in-situ adjustment system for the pump beam angle of an atomic spin inertial measurement device is characterized by comprising a beam expanding system disposed on the pump optical path on the left side of an alkali metal gas cell and a detection optical path system disposed on the right side of the alkali metal gas cell. The pump light emitted from the beam expanding system passes through the alkali metal gas cell via a depolarizing beam splitter. The depolarizing beam splitter reflects the detection light that passes through the alkali metal gas cell in opposition to the pump light to a photoelectric detection differential processing system, so that the in-situ adjustment of the pump beam angle can be achieved in the beam expanding system based on the detection result of the photoelectric detection differential processing system.

[0008] The in-situ adjustment of the pump beam angle includes adjusting the focal length and position of the beam expander. By adjusting, the polarizability of the alkali metal atoms in the system is maximized, thereby obtaining the optimal pump beam angle.

[0009] The photoelectric detection differential processing system obtains the linear polarization plane rotation angle information of the detection light after passing through the alkali metal gas cell, and then obtains the polarizability information of the alkali metal atoms in the gas cell.

[0010] The detection light and the pump light are directed to directly detect the atomic polarizability in the pump light direction. This allows for real-time direct measurement of the polarizability and avoids the measurement errors and indirect parameter errors introduced when the electronic polarizability is indirectly calculated using the system response in the traditional method.

[0011] The beam expanding system includes a first beam expander connected to a pump laser via a first optical isolator. The output side of the first beam expander is connected to a second beam expander via a first polarizing beam splitter, a first liquid crystal phase retarder, and a second polarizing beam splitter in sequence. The second beam expander is connected to the depolarizing beam splitter via a quarter-wave plate. The second polarizing beam splitter is connected to the first liquid crystal phase retarder via a first photodetector to form a first stable light intensity system. The light intensity after passing through the first stable light intensity system is stably controlled by adjusting the voltage of the first liquid crystal phase retarder. The first polarizing beam splitter and the second polarizing beam splitter are perpendicular to each other to achieve an extinction effect.

[0012] The detection optical path system includes a detection laser, which is connected to the depolarization beam splitter sequentially through a second optical isolator, a second half-wave plate, a fifth polarizing beam splitter, a second liquid crystal phase retarder, a fourth polarizing beam splitter, and an alkali metal gas cell. The fourth polarizing beam splitter is connected to the second liquid crystal phase retarder through a third photodetector to form a second stable light intensity system. The light intensity after passing through the second stable light intensity system is stabilized by adjusting the voltage of the second liquid crystal phase retarder. The fourth polarizing beam splitter and the fifth polarizing beam splitter are perpendicular to each other to achieve an extinction effect.

[0013] The photoelectric detection differential processing system includes a differential node. The output of the differential node is connected to a signal processor. The first input of the differential node is connected to the transmission side of a third polarizing beam splitter via a second photodetector. The second input of the differential node is connected to the reflection side of the third polarizing beam splitter via a fourth photodetector. The input side of the third polarizing beam splitter is connected to the depolarizing beam splitter via a first half-wave plate. The optical axes of the third polarizing beam splitter and the fourth polarizing beam splitter are orthogonal to achieve an extinction effect.

[0014] The detection laser generates a beam of monochromatic light that is detuned to alkali metal atoms, and the pump laser generates a beam of monochromatic light that is resonant with alkali metal atoms.

[0015] The alkali metal chamber is located in the oven and contains potassium, rubidium, or cesium atoms, while being filled with nitrogen and helium.

[0016] Let the intensity of the detected light after passing through the alkali metal gas cell be I. The difference in refractive index between left-handed and right-handed circularly polarized light in the polarization medium causes the polarization plane of the linearly polarized light to rotate by an angle due to polarization by the alkali metal atoms. If the light intensity entering the second photodetector is I1 and the light intensity entering the fourth photodetector is I2, then...

[0017]

[0018]

[0019] Therefore, it is calculated that The polarizability P of alkali metal atoms can then be calculated using the following formula. e ,

[0020]

[0021] Where K is a constant coefficient.

[0022] The technical effects of this invention are as follows: This invention, an in-situ adjustment system for the pump beam angle of an atomic spin inertial measurement device, takes an atomic spin inertial measurement device as its research object and addresses the problem of pump beam angle adjustment. It utilizes the fact that pump light polarizes atoms, and that pump beam angles with different properties result in different polarizabilities. A scheme is established to adjust the pump beam angle using atomic polarizability signals. This beam angle adjustment based on changes in the light field sensed by atoms meets design requirements while being easy to implement in engineering. It eliminates installation errors, reduces beam scattering errors caused by alkali metal gas cells, and improves atomic polarizability. It is suitable for products such as atomic spin inertial measurement devices and has a very broad application prospect.

[0023] The advantages of this invention compared to existing technologies are as follows: This invention utilizes the real-time response of atomic polarizability to adjust the pump beam angle, avoiding the installation errors and refraction angle errors of the alkali metal gas cell inherent in traditional methods. Furthermore, the atomic polarizability-based adjustment method can improve the atomic polarizability, further enhancing measurement accuracy. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the in-situ adjustment system for the pump beam angle of the atomic spin inertial measurement device of the present invention.

[0025] The reference numerals in the attached figures are listed below: 1-Pump laser; 2-First beam expander; 3-First polarizing beam splitter; 4-First liquid crystal phase retarder; 5-Second polarizing beam splitter; 6-First photodetector; 7-Second beam expander; 8-First optical isolator; 9-1 / 4 waveplate; 10-Depolarizing beam splitter; 11-First 1 / 2 waveplate; 12-Third polarizing beam splitter; 13-Second photodetector; 14-Alkali metal gas cell; 15-Fourth polarizing beam splitter; 16-Third photodetector; 17-Second liquid crystal phase retarder; 18-Fifth polarizing beam splitter; 19-Second 1 / 2 waveplate; 20-Second optical isolator; 21-Detection laser; 22-Oven; 23-Fourth photodetector; 24-Signal processor. Detailed Implementation

[0026] The following is in conjunction with the attached diagram ( Figure 1 The invention will be described in the following sections and examples.

[0027] Figure 1 This is a schematic diagram of the in-situ adjustment system for the pump beam angle of the atomic spin inertial measurement device of the present invention. (Reference) Figure 1 As shown, the in-situ adjustment system for the pump beam angle of the atomic spin inertial measurement device includes a beam expander system disposed on the pump beam path to the left of the alkali metal gas cell 14 and a detection beam path system disposed on the right of the alkali metal gas cell 14. The pump beam emitted from the beam expander system passes through the alkali metal gas cell 14 via a depolarizing beam splitter prism 10. The depolarizing beam splitter prism 10 reflects the detection beam that passes through the alkali metal gas cell 14 in opposition to the pump beam to a photoelectric detection differential processing system. Based on the detection result of the photoelectric detection differential processing system, the in-situ adjustment of the pump beam angle is achieved in the beam expander system. The in-situ adjustment of the pump beam angle includes adjusting the focal length and position of the beam expander to maximize the polarizability of the alkali metal atoms and thus obtain the optimal pump beam angle. The photoelectric detection differential processing system obtains the polarizability information of the alkali metal atoms within the gas cell by obtaining the linear polarization plane rotation angle information of the detection light after passing through the alkali metal gas cell. The detection light and the pump light are directed to directly detect the atomic polarizability in the pump light direction. This allows for real-time direct measurement of the polarizability and avoids the measurement errors and indirect parameter errors introduced when the electronic polarizability is indirectly calculated using the system response in the traditional method.

[0028] The beam expanding system includes a first beam expander 2 connected to a pump laser 1 via a first optical isolator 8. The output side of the first beam expander 2 is connected to a second beam expander 7 via a first polarizing beam splitter 3, a first liquid crystal phase retarder 4, and a second polarizing beam splitter 5. The second beam expander 7 is connected to the depolarizing beam splitter 10 via a quarter-wave plate 9. The second polarizing beam splitter 5 is connected to the first liquid crystal phase retarder 4 via a first photodetector 6 to form a first stable light intensity system. The light intensity after passing through the first stable light intensity system is stabilized by adjusting the voltage of the first liquid crystal phase retarder 4. The first polarizing beam splitter 3 and the second polarizing beam splitter 5 are perpendicular to each other to achieve an extinction effect.

[0029] The detection optical path system includes a detection laser 21. The detection laser 21 is connected to the depolarization beam splitter 10 in sequence through a second optical isolator 20, a second half-wave plate 19, a fifth polarization beam splitter 18, a second liquid crystal phase retarder 17, a fourth polarization beam splitter 15, and an alkali metal gas cell 14. The fourth polarization beam splitter 15 is connected to the second liquid crystal phase retarder 17 through a third photodetector 16 to form a second stable light intensity system. The light intensity after passing through the second stable light intensity system is stabilized by adjusting the voltage of the second liquid crystal phase retarder 17. The fourth polarization beam splitter 15 and the fifth polarization beam splitter 18 are perpendicular to each other to achieve an extinction effect. The photoelectric detection differential processing system includes a differential node. The output of the differential node is connected to a signal processor 24. The first input of the differential node is connected to the transmission side of the third polarizing beam splitter 12 through a second photodetector 13. The second input of the differential node is connected to the reflection side of the third polarizing beam splitter 12 through a fourth photodetector 23. The input side of the third polarizing beam splitter 12 is connected to the depolarizing beam splitter 10 through a first half-wave plate 11. The optical axes of the third polarizing beam splitter 12 and the fourth polarizing beam splitter 15 are orthogonal to achieve an extinction effect.

[0030] The detection laser 21 generates a beam of monochromatic light detuned to alkali metal atoms, and the pump laser 1 generates a beam of monochromatic light resonating with alkali metal atoms. The alkali metal gas chamber 14 is located in the oven 22 and contains potassium, rubidium, or cesium atoms, while also being filled with nitrogen and helium. Assuming the intensity of the detection light after passing through the alkali metal gas chamber is I, the difference in refractive index between left-handed and right-handed circularly polarized light in the polarization medium causes the polarization plane of the linearly polarized light after passing through the alkali metal gas chamber to rotate by an angle. If the light intensity entering the second photodetector is I1 and the light intensity entering the fourth photodetector is I2, then...

[0031]

[0032]

[0033] Therefore, it is calculated that The polarizability P of alkali metal atoms can then be calculated using the following formula. e ,

[0034]

[0035] Where K is a constant coefficient.

[0036] The in-situ adjustment system for the pump beam angle of the atomic spin inertial measurement device of the present invention includes a pump laser (1), a first beam expander (2), a first polarizing beam splitter (3), a first liquid crystal phase retarder (4), a second polarizing beam splitter (5), a first photodetector (6), a second beam expander (7), a first optical isolator (8), a quarter-wave plate (9), a depolarizing beam splitter (10), a first half-wave plate (11), a third polarizing beam splitter (12), a second photodetector (13), an alkali metal gas cell (14), and a fourth polarizing beam splitter. A beam splitter (15), a third photodetector (16), a second liquid crystal phase retarder (17), a fifth polarizing beam splitter (18), a second half-wave plate (19), a second optical isolator (20), a detection laser (21), an oven (22), a fourth photodetector (23), and a signal processor (24) are used. A monochromatic beam resonating with alkali metal atoms is generated by a pump laser (1), and passes sequentially through the first optical isolator (8), the first beam expander (2), the first polarizing beam splitter (3), the first liquid crystal phase retarder (4), and the second half-wave plate (19). After being split into two beams of equal size and orthogonal polarization direction by the polarization beam splitter (5), the reflected light is sent to the first photodetector (6) for detection; the transmitted light passes sequentially through the second beam expander (7), the quarter-wave plate (9), the depolarization beam splitter (10), and the alkali metal gas cell (14); a beam of monochromatic light detuned to the alkali metal atoms is generated by the detection laser (21), and passes sequentially through the second optical isolator (20), the second half-wave plate (19), the fifth polarization beam splitter (18), the second liquid crystal phase retarder (17), and the fourth polarization beam splitter (15). After being split into two beams of the same size and orthogonal polarization, the reflected light is sent to the third photodetector (16) for detection; the transmitted light passes through the alkali metal gas chamber (14) and the depolarizing beam splitter (10) in sequence, and its reflected light passes through the first half-wave plate (11) and the third polarizing beam splitter (12) in sequence. The transmitted light is then sent to the second photodetector (13), and the reflected light is sent to the fourth photodetector (23); the signals from the second photodetector (13) and the fourth photodetector (23) are differentially divided and sent to the signal processor (24) for the instructor to observe.

[0037] The first optical isolator (8) and the second optical isolator (20) in the optical path are polarization-dependent optical isolators.

[0038] The gas chamber (14) contains potassium, rubidium or cesium atoms, and is filled with nitrogen and helium.

[0039] The first polarizing beam splitter (3), the first liquid crystal phase retarder (4), and the second polarizing beam splitter (5) together constitute a light intensity stabilization system. The fifth polarizing beam splitter (18), the second liquid crystal phase retarder (17), and the fourth polarizing beam splitter (15) together constitute a light intensity stabilization system. In the two light intensity stabilization systems, the two polarizing beam splitters are placed vertically to achieve the extinction effect. The light intensity after passing through the light intensity stabilization system is stabilized by adjusting the voltage of the liquid crystal phase retarder.

[0040] The third polarizing beam splitter (12) and the fourth polarizing beam splitter (15) are placed orthogonally to each other, and the first half-wave plate is adjusted so that the system composed of the third polarizing beam splitter (12), the first half-wave plate (11) and the fourth polarizing beam splitter (15) can achieve the effect of extinction.

[0041] The polarizability detection method uses a method of direct detection of the atomic polarizability in the pump light direction by opposing the detection laser and the pump laser. On the one hand, it can directly measure the polarizability in real time, and on the other hand, it avoids the measurement error and the error caused by indirect parameters introduced when the electronic polarizability is indirectly calculated by the system response in the traditional way.

[0042] Different beam angles result in different polarizabilities of alkali metal atoms. The beam angle can be adjusted by changing different focal length beam expanders and adjusting the position of the beam expander. By adjusting, the polarizability of alkali metal atoms in the system can be maximized, thus obtaining the optimal pump beam angle.

[0043] The signals from the second photodetector (13) and the fourth photodetector (23) are differentially processed and sent to the signal processor (24) to obtain the linear polarization plane rotation angle information of the detected laser after passing through the gas cell, and then to obtain the polarizability information of the alkali metal atoms in the gas cell, that is:

[0044] Define the intensity of the transmitted light after the detection laser (21) passes through the fourth polarizing beam splitter (15) as I0, and the intensity of the light after passing through the alkali metal gas cell (14) as I. The linearly polarized light has different refractive indices for left-handed circularly polarized light and right-handed circularly polarized light in the polarization medium. The polarized alkali metal atoms will cause the polarization plane of the linearly polarized light after passing through the alkali metal gas cell to rotate by an angle.

[0045]

[0046] Where l is the propagation distance of the detection light in the alkali metal gas cell (14), and r eLet n be the electron radius, c be the speed of light, f be the oscillator strength, and n be the electron radius. a Where ν is the atomic number density, D(ν) is a coefficient related to the laser frequency ν, and all of the above parameters are constants. e Given the polarizability of alkali metal atoms, the above formula can be simplified to:

[0047]

[0048] K is a simplified constant coefficient. The light intensity I1 entering the second photodetector (13) and the light intensity I2 entering the fourth photodetector (23) are respectively:

[0049]

[0050]

[0051] The rotation angle of the linear polarization plane can be obtained by dividing the two and processing the result by the signal processor (24). and atomic polarizability P e This invention, starting from the overall perspective, studies the in-situ adjustment system of the pump beam angle of an atomic spin inertial measurement device, which will provide guidance and reference for the design of pump beam angle adjustment for similar atomic spin inertial / magnetic field measurement devices.

[0052] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. An in-situ adjustment system for the pump beam angle of an atomic spin inertial measurement device, characterized in that, The system comprises a beam expander system arranged on the left side of the alkali metal cell in the pumping light path and a detection light path system arranged on the right side of the alkali metal cell, the pumping light emitted by the beam expander system passes through the alkali metal cell via a depolarization prism, the depolarization prism reflects the detection light which is in counter-propagation with the pumping light and passes through the alkali metal cell to a photodetector differential processing system, so as to realize in-situ adjustment of the pumping light beam angle in the beam expander system according to the detection result of the photodetector differential processing system; The in-situ adjustment of the pumping light beam angle comprises adjusting the focal length and position of the beam expander mirror, so as to maximize the alkali metal atom polarization rate and obtain the optimal pumping light beam angle. The photodetector differential processing system obtains the linear polarization plane rotation angle information of the detection light after passing through the alkali metal cell, and further obtains the alkali metal atom polarization rate information in the cell.

2. The atomic spin inertial device pump light beam angle in-situ adjustment system of claim 1, wherein, The detection light and the pumping light are in counter-propagation to directly detect the atomic polarization rate in the pumping light direction.

3. The atomic spin inertial device pump light beam angle in-situ adjustment system of claim 1, wherein, The beam expander system comprises a first beam expander mirror connected to a pumping laser via a first optical isolator, the output side of the first beam expander mirror is connected to a second beam expander mirror via a first polarizing beam splitter, a first liquid crystal phase retarder and a second polarizing beam splitter in sequence, the second beam expander mirror is connected to the depolarization prism via a 1 / 4 wave plate, the second polarizing beam splitter is connected to the first liquid crystal phase retarder via a first photodetector to form a first light intensity stabilizing system, the light intensity after passing through the first light intensity stabilizing system is stably controlled by adjusting the voltage of the first liquid crystal phase retarder, and the first polarizing beam splitter and the second polarizing beam splitter are perpendicular to each other to achieve light extinction effect.

4. The atomic spin inertial measurement apparatus pump light beam angle in-situ adjustment system of claim 1, wherein, The detection light path system comprises a detection laser, the detection laser is connected to the depolarization prism via a second optical isolator, a second 1 / 2 wave plate, a fifth polarizing beam splitter, a second liquid crystal phase retarder, a fourth polarizing beam splitter and an alkali metal cell in sequence, the fourth polarizing beam splitter is connected to the second liquid crystal phase retarder via a third photodetector to form a second light intensity stabilizing system, the light intensity after passing through the second light intensity stabilizing system is stably controlled by adjusting the voltage of the second liquid crystal phase retarder, and the fourth polarizing beam splitter and the fifth polarizing beam splitter are perpendicular to each other to achieve light extinction effect.

5. The atomic spin inertial measurement apparatus pump light beam angle in-situ adjustment system of claim 4, wherein, The photodetector differential processing system comprises a differential node, the output end of the differential node is connected to a signal processor, the first input end of the differential node is connected to the transmission side of a third polarizing beam splitter via a second photodetector, the second input end of the differential node is connected to the reflection side of the third polarizing beam splitter via a fourth photodetector, the input side of the third polarizing beam splitter is connected to the depolarization prism via a first 1 / 2 wave plate, and the third polarizing beam splitter and the fourth polarizing beam splitter are orthogonal to each other to achieve light extinction effect.

6. The atomic spin inertial measurement apparatus pump light beam angle in-situ adjustment system of claim 1, wherein, The detection laser generates a monochromatic light which is detuned from the alkali metal atoms, and the pumping laser generates a monochromatic light which is resonant with the alkali metal atoms.

7. The atomic spin inertial measurement apparatus pump light beam angle in-situ adjustment system of claim 1, wherein, The alkali metal cell is located in an oven, and contains potassium, rubidium or cesium atoms, and is filled with nitrogen and helium.

8. The atomic spin inertial measurement apparatus pump light beam angle in-situ adjustment system of claim 5, wherein, The intensity of the detected light after passing through the alkali metal cell is I, and the difference in the refractive index of the left-handed and right-handed circularly polarized light in the polarizing medium causes the polarization plane of the linearly polarized light after passing through the alkali metal cell to rotate by an angle The intensity of the light entering the second photodetector is I1, and the intensity of the light entering the fourth photodetector is I2. From this the atomic polarizability P of the alkali metal is calculated The atomic polarizability P of the alkali metal is then calculated from e , K is a constant coefficient.

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