Large-angle control and calibration device and method for Raman reflector

Abstract

The invention discloses a Raman reflector large-angle control and calibration device which comprises a Raman laser light source, a 2 * 2 optical fiber coupler, a Raman collimating lens group, a 1 / 4 wave plate, a Raman reflector I, a Raman reflex lens group, a magneto-optical trap device, a 1 / 4 wave plate II and a Raman reflector II, wherein the Raman reflex lens group, the magneto-optical trap device, the 1 / 4 wave plate II and the Raman reflector II are arranged in an atomic gravimeter structure frame; the invention further discloses a control and calibration method. The method is suitable for the precision and the accuracy of the overlap ratio of the light wave vector reflected by the Raman light and the Raman light at a large angle, and the dynamic environment adaptability of the atomic gravimeter can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of quantum precision measurement technology, specifically to a Raman mirror large-angle control and calibration device, and its calibration method. Background Technology

[0002] Inertial sensors such as accelerometers and gyroscopes based on cold atom interferometry have gradually moved out of the laboratory. In recent years, cold atom accelerometers have been successfully applied to field measurements in vehicles such as trucks, ships, and airplanes. However, these sensors are highly susceptible to dynamic changes in the operating environment. Taking a gravity accelerometer as an example, if the angle between the Raman beam direction and the perpendicular to gravity is 1 mrad, the gravitational acceleration value can decrease by hundreds or even thousands of microgals. If the angle increases further, attitude interference caused by rotation may severely reduce or eliminate the contrast of the atomic interference fringes, making gravity measurement impossible and severely limiting the application of atomic gravimeters in dynamic environments. In addition, poor overlap between the two laser beams constituting the Raman beam in dynamic environments is also a significant source of systematic error.

[0003] A promising solution employs real-time compensation control of the Raman mirror to ensure that the Raman wave vector direction remains aligned with the vertical line of gravity even when the carrier is at different tilt angles, and to achieve overlap between the wave vector directions of two Raman beams. While this method of stabilizing the gravity-sensitive axis through real-time compensation of the Raman mirror can actively stabilize the axis, its performance bottleneck lies in the lack of an efficient and precise alignment and calibration method suitable for large angles.

[0004] Specifically, achieving alignment and overlap between the two Raman beams and the vertical line of gravity at large angles is a prerequisite for ensuring the final compensation effect. Summary of the Invention

[0005] One of the objectives of this invention is to provide a large-angle control and calibration device for Raman mirrors, in order to solve the problem of achieving overlap of two Raman beams in an environment where an atomic gravimeter is subject to large-angle swaying.

[0006] The technical solution adopted by this invention to solve its technical problem is: a Raman reflector large-angle control and calibration device, including a Raman laser source, a 2×2 fiber coupler, and a Raman collimating lens group for expanding and collimating the Raman beam. The Raman laser source includes two Raman beams, Raman beam 1 and Raman beam 2, which interact with cold atoms. The 2×2 fiber coupler is used to split the Raman laser source and the reflected light from the second Raman reflector. The Raman laser source is connected to port 1 of the 2×2 fiber coupler, which serves as the input port for Raman beam 1 and Raman beam 2. Port 2 is connected to a power meter. Port 3 is used to monitor the reflected light power of the Raman beam after Raman mirror 2 during calibration. Port 3 is connected to Raman collimating mirror group 30 and serves as the connection port between the 2×2 fiber coupler and the Raman collimating mirror group. Port 4 serves as the input port for stabilizing the Raman beam power. The output light path of the Raman collimating mirror group is sequentially equipped with a quarter wave plate, a Raman mirror, a Raman folding mirror group, a magneto-optical trap device, a quarter wave plate, and a Raman mirror. The magneto-optical trap device includes a vacuum cavity, a cold atom cluster, and a set of anti-Helmholtz coils for generating cold atoms.

[0007] The aforementioned Raman reflector large-angle control and calibration device also includes an attitude displacement sensor within the atomic gravimeter structural frame. The attitude displacement sensor is used to measure the attitude values ​​of the atomic gravimeter structural frame at different angles, including pitch, roll, and yaw angle information.

[0008] The Raman reflector large-angle control and calibration device is described above, wherein the Raman folding mirror group, the magneto-optical trap device, the second quarter wave plate and the second Raman reflector are fixedly connected within the structural frame of the atomic gravimeter.

[0009] The aforementioned Raman mirror large-angle control and calibration device uses a 2×2 fiber optic coupler as a polarization-maintaining optical component.

[0010] The aforementioned Raman reflector large-angle control and calibration device has Raman reflector one and Raman reflector two mounted on a voice coil control platform.

[0011] The second objective of this invention is to provide a method for large-angle control and calibration of a Raman mirror under different orientations, comprising the following steps:

[0012] S1. The initial installation positions of Raman mirror II and attitude displacement sensor are basically consistent and fixed together. A carrier coordinate system is established with the geometric center of Raman mirror II as the origin, the x-axis control axis of Raman mirror II as the x-axis, and the normal vector of Raman mirror II as the z-axis. An inertial reference frame is established using the pitch, roll, and y axes of the initial alignment position of the attitude displacement sensor as the z-axis, x-axis, and y-axis, respectively. ;

[0013] S2, the zero-position normal vector of Raman mirror two is consistent with the wave vector of its reflected light wave, which can be expressed in the carrier coordinate system as: In an inertial coordinate system consistent with the initial alignment coordinate system of the attitude displacement sensor, it can be expressed as: ,in This is the transfer matrix from the attitude displacement sensor coordinate system to the carrier coordinate system. The transfer matrix from the initial alignment coordinate system of the attitude displacement sensor to a certain attitude i can be obtained by solving the transfer matrix equations of the reflected light wave vector of the Raman mirror II in the carrier coordinate system and the inertial coordinate system. y-axis controls angle ;

[0014] S3. Based on the coincidence of the reflected light wave vector and the incident light wave vector of Raman mirror two in different attitudes, the Raman reflected light wave vector in the body coordinate system in different attitudes can be obtained by combining the calibration of Raman mirror one and Raman folding mirror group. Furthermore, the reflected light wave vector is a parallel vector in the inertial coordinate system, that is... The transition matrix can be obtained by solving a series of linear equations. ;

[0015] S4. The Raman incident light wave vector, after passing through Raman reflector one and the Raman folding mirror group, remains vertical in all attitudes i. In a certain attitude i, by adjusting the position of Raman reflector two, its reflected light wave vector passes through the 1 / 4 wave plate two, the Raman folding mirror group, Raman reflector one, the 1 / 4 wave plate one, the Raman collimating mirror group, and port 2 of the 2×2 fiber coupler. Power monitoring is performed at the input port. When the power meter reading reaches its maximum, it is considered that the reflected light wave vector of Raman reflector two coincides with the Raman incident light wave vector. The transfer matrix from the initial alignment coordinate system of the attitude displacement sensor to the certain attitude i is recorded. The carrier coordinates of the Raman reflected light wave vector at a certain posture i. .

[0016] Furthermore, the transfer matrix from the attitude displacement sensor coordinate system to the carrier coordinate system... The solution process requires calibrating the return wave vector of the second Raman mirror in different axial carrier coordinate systems, i.e. In the diagram, i and j belong to the return wave vectors of the second Raman mirror along different axes, and a nonlinear fitting solution is obtained to calculate the transfer matrix from the attitude displacement sensor coordinate system to the carrier coordinate system. according to The rotation method is used to solve for the transfer matrix from the initial alignment coordinate system of the attitude displacement sensor to a certain attitude i. According to the pitch value of the attitude displacement sensor Roll value Swell value Solve the problem.

[0017] The beneficial effects of this invention are:

[0018] The method of this invention is particularly suitable for the accuracy and precision of the coincidence between the wave vector of the Raman light reflected back and the Raman light itself at large angles, which can greatly improve the dynamic environmental adaptability of atomic gravimeters.

[0019] This invention employs an offline calibration method and utilizes an attitude displacement sensor in conjunction with a voice coil control platform to achieve self-stabilization control of the incident and reflected light wave vectors of a mirror under different attitudes.

[0020] In the calibration process, this invention uses a 2×2 polarization-maintaining fiber coupler instead of an optical circulator, which can provide a stable power output port for the Raman beam while meeting the requirements for large-angle control and calibration of the Raman mirror. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0022] Figure 2 This is a schematic diagram of the large-angle control of the Raman reflector in a certain posture in an embodiment of the present invention.

[0023] The labels in the attached figures are as follows: 10—Raman laser source, 20—2×2 fiber coupler, 201—port 1, 202—port 2, 203—port 3, 204—port 4, 30—Raman collimating mirror group, 40—1 / 4 wave plate one, 50—Raman laser beam, 60—Raman reflector one, 70—Raman folding mirror group, 80—magneto-optical trap device, 801—anti-Helmholtz coil, 802—vacuum cavity, 803—cold atom cluster, 90—1 / 4 wave plate two, 100—Raman reflector two, 110—attitude displacement sensor, 120—power meter, 130—atomic gravimeter structural frame. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings.

[0025] Example 1

[0026] like Figure 1As shown, this invention discloses a large-angle control and calibration device for a Raman mirror, comprising a Raman laser source 10, a polarization-maintaining optical device 2×2 fiber coupler 20, and a Raman collimating lens group 30 for expanding and collimating the Raman beam. The Raman laser source 10 includes two Raman beams, Raman beam 1 and Raman beam 2, which interact with cold atoms. Raman beam 1 and Raman beam 2 are collectively referred to as Raman beams in this patent. The 2×2 fiber coupler 20 is used to split the reflected light from the Raman laser source 10 and the Raman mirror 100. The Raman laser source 10 is connected to port 1 201, which serves as the input port for Raman beam 1 and Raman beam 2. Port 2 202 is connected to a power meter 120. The Raman beam is used to monitor the reflected light power of the Raman beam through the second Raman mirror 100 during the calibration process. Port 3 (203) is connected to the Raman collimating mirror group 30. Port 3 (203) serves as the connection port between the 2×2 fiber coupler 20 and the Raman collimating mirror group 30. Port 4 (204) serves as the input port for stabilizing the Raman beam power. The output light path of the Raman collimating mirror group 30 is sequentially provided with a quarter wave plate 40, a Raman mirror 60, and a Raman folding mirror group 70, a magneto-optical trap device 80, a quarter wave plate 90, and a second Raman mirror 100 within the atomic gravimeter structural frame 130. The magneto-optical trap device 80 includes a vacuum cavity 802, a cold atom cluster 803, and a set of anti-Helmholtz coils 801, which are used to generate cold atoms. An attitude displacement sensor 110 is also installed inside the atomic gravimeter structural frame 130. The attitude displacement sensor 110 is used to measure the attitude measurement values ​​of the atomic gravimeter structural frame 130 in different attitudes, including pitch, roll, and yaw angle information. The Raman folding mirror group 70, the magneto-optical trap device 80, the quarter-wave plate 90, and the Raman reflector 100 are fixedly connected inside the atomic gravimeter structural frame 130.

[0027] In this invention, Raman reflector 60 and Raman reflector 100 are mounted on a voice coil control platform. Raman reflector 60 is used to adjust the incident angle of the Raman laser beam under different orientations; Raman folding mirror group 70 is used to adjust the incident direction of the Raman laser beam 50 incident on Raman reflector 60 so that the Raman laser beam 50 output under different orientations always remains vertical and passes through the center of the cold atom cluster 803; Raman reflector 60 and Raman folding mirror group 70 are used to adjust the output light wave vector direction of the Raman beam under different orientations so that it always remains vertical in the inertial coordinate system and coincides with the direction of the vertical line of gravity; 1 / 4 wave plate 90 is used to adjust the polarization of the Raman beam reflected back by Raman reflector 100 so that its output power at port 2 of the 2×2 fiber coupler 20 reaches the maximum during calibration / to adjust the polarization of the reflected back light of Raman reflector 100 so that its output optical power at the output port of the 2×2 fiber coupler 20 reaches the maximum.

[0028] Example 2

[0029] like Figure 2 As shown, the present invention discloses a method for controlling and calibrating a Raman mirror at a large angle, comprising the following steps.

[0030] S1. The initial installation positions of Raman mirror 2 100 and attitude displacement sensor 110 are basically consistent and fixed together. A carrier coordinate system is established with the geometric center of Raman mirror 2 100 as the origin, the x-axis control axis of Raman mirror 2 100 as the x-axis, and the normal vector of Raman mirror 2 100 as the z-axis. An inertial reference frame is established using the pitch, roll, and pitch axes of the initial alignment position of the attitude displacement sensor 110 as the z-axis, x-axis, and y-axis, respectively. .

[0031] S2, the zero-position normal vector of the Raman mirror 100 is consistent with the wave vector of its reflected light wave, which can be expressed in the carrier coordinate system as: In the inertial coordinate system (consistent with the initial alignment coordinate system of the attitude displacement sensor 110), it can be represented as: ,in This is the transfer matrix from the attitude displacement sensor 110 coordinate system to the carrier coordinate system. The transfer matrix from the initial alignment coordinate system of the attitude displacement sensor 110 to a certain attitude i can be obtained by solving the transfer matrix equation of the reflected light wave vector of the Raman mirror 100 into the quantum carrier coordinate system and the inertial coordinate system. y-axis controls angle .

[0032] S3. Based on the coincidence of the reflected light wave vector and the incident light wave vector of Raman mirror 100 under different attitudes, the Raman reflected light wave vector in the body coordinate system under different attitudes can be obtained by combining the calibration of Raman mirror 60 and Raman folding mirror group 70. Furthermore, the reflected light wave vector is a parallel vector in the inertial coordinate system, that is... The transition matrix can be obtained by solving a series of linear equations. .

[0033] S4. The Raman incident light wave vector after passing through Raman reflector 60 and Raman folding mirror group 70 remains vertical in different postures i. In a certain posture i, by adjusting the position of Raman reflector 100, its reflected light wave vector passes through port 202 of 1 / 4 wave plate 90, Raman folding mirror group 70, Raman reflector 60, 1 / 4 wave plate 40, Raman collimating mirror group 30 and 2×2 fiber coupler 20. Power monitoring is performed at the input port. When the power meter 120 reading reaches the maximum, it is considered that the reflected light wave vector of Raman reflector 100 coincides with the Raman incident light wave vector. The output values ​​of posture displacement sensor 110 and Raman reflector 100 at this time are recorded as steps S2 and S3. and .

[0034] The transfer matrix from the attitude displacement sensor 110 coordinate system to the carrier coordinate system The solution process requires calibrating the return wave vector of the Raman mirror 2100 in different axial carrier coordinate systems, i.e. In the equation, i and j belong to the return wave vectors of Raman mirrors 100 with different axes, and are solved by nonlinear fitting. The transfer matrix from the coordinate system of the attitude displacement sensor 110 to the coordinate system of the carrier is then calculated. according to The rotation method is used to solve the problem, and the attitude displacement sensor 110 is initially aligned with the coordinate system to the transfer matrix of a certain attitude i. According to the pitch value of attitude displacement sensor 110 Roll value Swell value Solve the problem.

[0035] Those skilled in the art will readily understand that the above description is merely a preferred use case of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for controlling and calibrating a large angle of a Raman mirror, characterized in that: The system includes a Raman laser source (10), a 2×2 fiber coupler (20), and a Raman collimating lens assembly (30). The Raman laser source (10) and the Raman collimating lens assembly (30) are connected to port 1 (201) and port 3 (203) of the 2×2 fiber coupler (20), respectively. Port 2 (202) of the 2×2 fiber coupler (20) is connected to a power meter (120), and port 4 (204) serves as the power input for Raman beam stabilization. At the input port, the Raman collimating lens group (30) is provided with a 1 / 4 wave plate (40), a Raman reflector (60), a Raman folding mirror group (70), a magneto-optical trap device (80), a 1 / 4 wave plate (90), and a Raman reflector (100) in sequence on the output optical path. The magneto-optical trap device (80) includes a vacuum cavity (802), a cold atom cluster (803), and a set of anti-Helmholtz coils (801) for generating cold atoms.

2. The Raman reflector large-angle control and calibration device according to claim 1, characterized in that, The atomic gravimeter structural frame (130) is also equipped with an attitude displacement sensor (110) for measuring the attitude measurement values ​​of the atomic gravimeter structural frame (130) under different attitudes.

3. A Raman reflector large-angle control and calibration device according to claim 1 or 2, characterized in that, The Raman folding mirror assembly (70), magneto-optical trap device (80), quarter-wave plate II (90) and Raman reflector II (100) are fixed within the atomic gravimeter structural frame (130).

4. The Raman reflector large-angle control and calibration device according to claim 3, characterized in that, The 2×2 fiber coupler (20) is a polarization-maintaining optical device.

5. The Raman reflector large-angle control and calibration device according to claim 3, characterized in that, The Raman reflector one (60) and Raman reflector two (100) are mounted on the voice coil control platform.

6. A method for large-angle control and calibration of a Raman mirror, employing the device described in claim 1, characterized in that, Includes the following steps: S1, with the geometric center of Raman mirror 2 (100) as the origin, the x-axis as the control axis, and the normal vector as the z-axis, establish the carrier coordinate system. An inertial reference system is established using the pitch, roll, and y axes of the initial alignment position of the attitude displacement sensor (110) as the z-axis, x-axis, and y-axis, respectively. ; S2, Raman mirror two (100) is represented in the carrier coordinate system as follows: In an inertial coordinate system consistent with the initial alignment coordinate system of the attitude displacement sensor (110), it is represented as ,in The transfer matrix from the attitude displacement sensor (110) coordinate system to the carrier coordinate system is given. The transfer matrix from the initial alignment coordinate system of the attitude displacement sensor (110) to a certain attitude i is obtained by solving the transfer matrix equation of the reflected light wave vector of the Raman mirror (100) into the quantum carrier coordinate system and the inertial coordinate system. y-axis controls angle ; S3, based on the coincidence of the reflected light wave vector and the incident light wave vector of Raman mirror 2 (100) under different attitudes, and combined with the calibration of Raman mirror 1 (60) and Raman folding mirror group (70), the Raman reflected light wave vector in the body coordinate system under different attitudes is obtained. The reflected light wave vector is a parallel vector in the inertial coordinate system, that is... The transition matrix is ​​obtained by solving the simultaneous system of linear equations. ; S4. The Raman incident light vector after passing through Raman reflector one (60) and Raman folding mirror group (70) remains vertical in different postures i. In a certain posture i, by adjusting the position of Raman reflector two (100), the reflected light vector passes through the port 2 (202) of 1 / 4 wave plate two (90), Raman folding mirror group (70), Raman reflector one (60), 1 / 4 wave plate one (40), Raman collimating mirror group (30) and 2×2 fiber coupler (20) for power monitoring. When the power meter (120) reading reaches the maximum, it is considered that the reflected light vector of Raman reflector two (100) coincides with the Raman incident light vector. The transfer matrix of the initial alignment coordinate system of the posture displacement sensor (110) to a certain posture i is recorded. The carrier coordinates of the Raman reflected light wave vector at a certain posture i. .

7. The method for large-angle control and calibration of a Raman mirror according to claim 6, characterized in that, The transition matrix The solution process requires calibrating the return wave vector of Raman mirror 2 (100) in the carrier coordinate system with different axes, i.e. In the equation, i and j belong to the return wave vectors of Raman mirrors (100) with different axes, and are solved by nonlinear fitting; the transfer matrix from the coordinate system of the attitude displacement sensor (110) to the coordinate system of the carrier is obtained. according to The rotation method is used to solve the problem; the attitude displacement sensor (110) is initially aligned with the coordinate system to the transfer matrix of a certain attitude i. According to the pitch value of the attitude displacement sensor (110) Roll value Swell value Solve the problem.

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