Method for improving spatial optical path performance of cold atom gravimeter

Abstract

This invention relates to a method for improving the spatial optical path performance of a cold atom gravimeter. This method employs a pre-assembly and adjustment scheme to select components better suited to each assembly step, reducing the angle adjustment range during assembly, increasing bonding strength and environmental adaptability, and improving assembly efficiency. Furthermore, by establishing a relationship between the wedge gap angle and the curing shrinkage angle, an effective angle pre-compensation mechanism is established. Pre-compensating for the curing shrinkage angle allows for better control of the output light angle, increasing the coupled output laser power. This method organically combines pre-assembly and adjustment with the angle pre-compensation mechanism, improving both the final coupled output light power and the bonding strength, thereby extending the lifespan.

Description

Technical Field

[0001] This invention relates to the field of optoelectronics technology, and more specifically to a method for improving the spatial optical path performance of a cold atom gravimeter. Background Technology

[0002] Cold atom gravimeters manipulate atoms using light of different frequencies. The laser optical path mainly consists of a frequency-locked optical path and a frequency-modulated optical path. The frequency-locked optical path provides a frequency reference for the entire gravity measurement process, ensuring the frequency stability of subsequent light sources. In the frequency-modulated optical path, frequency-shifting devices such as acousto-optic modulators (AOMs) generate beams of different frequencies and powers required for manipulating cold atom interference, including trapping cooling light, pumping back light, clearing light, Raman light, and probe light.

[0003] To minimize the optical path volume and improve production efficiency, optical components are typically bonded to an optical substrate using ultraviolet (UV) adhesive. In the optical path of a cold atom gravimeter, due to the limited mass of the optical components and the substrate itself, a wedge-shaped gap usually exists between the optical components and the substrate to ensure that the light is output at a specific angle. This wedge-shaped gap is filled with UV-curable adhesive. However, an excessively large wedge-shaped gap may reduce the stability and strength of the bond. Currently, commonly used UV adhesives are usually free-radical acrylic adhesives. Due to the changes in interatomic distance and the free volume change from monomer to polymer caused by the polymerization reaction, volume shrinkage is inevitable during the curing process. This shrinkage usually leads to changes in the orientation of the optical components, causing changes in the output light angle, and thus affecting the improvement of coupling efficiency. Summary of the Invention

[0004] Based on the above description, the present invention provides a method for improving the spatial optical path performance of a cold atom gravimeter, so as to solve the technical problem of the change in the output light angle of the optical path of the cold atom gravimeter in the prior art.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A method for improving the space optical path performance of a cold atom gravimeter includes the following steps:

[0007] S1, Construct an assembly and adjustment optical path, the assembly and adjustment optical path including an assembly and adjustment frequency shift optical path, a reference component and an autocollimator, the assembly and adjustment frequency shift optical path including an input optical fiber, a collimator, a first polarization beam splitter, an acousto-optic modulator, a first half-wave plate, a triangular mirror, a second half-wave plate and a second polarization beam splitter arranged along the light propagation direction, the reference component being disposed at the front end of the input optical fiber, and the autocollimator being disposed at the rear end of the second polarization beam splitter;

[0008] S2, Pre-assembly and screening: Place the optical components naturally on the substrate, measure the adhesive filling angle between the optical components and the substrate, load the optical components into the classic frequency-shifting optical path, sort and number the optical components according to the angle adjustment required for the output light, and screen out the optical components that meet the predetermined requirements.

[0009] S3, Curing Pre-compensation: The optical element is cured on the substrate with adhesive, the actual linear shrinkage rate of the adhesive is obtained, and the installation angle of the optical element is pre-compensated based on the change in the angle of adhesive shrinkage.

[0010] The optical element is either a first polarization beam splitter or a second polarization beam splitter.

[0011] Based on the above technical solution, the present invention can be further improved as follows.

[0012] Furthermore, the optical element that meets the predetermined requirements is an optical element whose angle adjustment amount is within a predetermined range so that the output light angle is consistent with the reference element.

[0013] Furthermore, the optical element that meets the predetermined requirements is an optical element that can make the output light angle consistent with the reference element without angle adjustment.

[0014] Furthermore, the adhesive is a UV-curable adhesive.

[0015] Furthermore, let the change in the angle of the adhesive shrinkage be x, the actual linear shrinkage rate be a, and the adhesive filling angle be α. Then we have x = a * α, and the pre-compensation angle is (a * α) / (1 - a).

[0016] Furthermore, the light rays of the classical frequency-shifting optical path are reflected at a right angle at the triangular mirror, and the autocollimator can be moved to the rear end of the triangular mirror.

[0017] Furthermore, the angle pre-compensation includes adjusting the optical element using an adjustment bracket in the opposite direction to the linear contraction direction of the adhesive.

[0018] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0019] (1) This method, through the pre-assembly and adjustment scheme, can select components that are more suitable for each step of assembly and adjustment, reduce the angle adjustment range during the assembly and adjustment process, increase the bonding firmness and environmental adaptability, and improve the assembly and adjustment efficiency.

[0020] (2) By establishing the relationship between the wedge gap angle and the curing shrinkage angle, an effective angle pre-compensation mechanism is established. Pre-compensating the curing shrinkage angle can better control the output light angle and improve the coupled output laser power.

[0021] (3) By combining the pre-installed adjustment with the angle pre-compensation mechanism, the final coupled output optical power can be improved while the bonding strength is increased and the service life is extended. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the steps of a method for improving the space optical path performance of a cold atom gravimeter, as provided in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the optical path assembly in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the classic frequency-shifting optical path in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram illustrating the implementation of curing pre-compensation in an embodiment of the present invention. Detailed Implementation

[0026] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0028] It is understood that spatial relation terms such as "below," "under," "below," "below," "above," "above," etc., can be used here to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as "below" or "below" of the other element or feature will be oriented "above" the other element or feature. Therefore, the exemplary terms "below" and "below" can include both upper and lower orientations. Furthermore, the device may also include other orientations (e.g., rotated 90° or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0029] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. In the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have the transmission of electrical signals or data between them.

[0030] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0031] like Figure 1 As shown, this application provides a method for improving the space optical path performance of a cold atom gravimeter, which includes the following steps:

[0032] S1, construct and adjust the optical path, such as Figure 2 As shown, the assembly and adjustment optical path includes an assembly and adjustment frequency shift optical path 100, a reference component 200, and an autocollimator 300.

[0033] Among them, such as Figure 3 As shown, the classic frequency-shifting optical path 400 includes an input optical fiber 110, a collimator 120, a first polarization beam splitter 130, an acousto-optic modulator 140, a first half-wave plate 150, a triangular mirror 160, a second half-wave plate 170, a second polarization beam splitter 180, an output collimator 190, and an output optical fiber arranged along the direction of light propagation.

[0034] The laser beam input through the input fiber 110 is collimated to the right by the collimator 120. After being filtered by the first polarization beam splitter 130, it is frequency-shifted by the acousto-optic modulator 140 to obtain the laser beam with the frequency required to manipulate atoms. Then, it passes through the first half-wave plate 150 to change the polarization direction, the triangular mirror 160 deflects the optical axis downward, the second half-wave plate 170 changes the polarization direction, and then reaches the second polarization beam splitter 180. The second polarization beam splitter 180 deflects the optical axis to the right, and after being collimated by the output collimator 190, it is output.

[0035] In its own application, the frequency-shifting optical path 100 is modified from the classic frequency-shifting optical path 400, including an input optical fiber 110 arranged along the direction of light propagation, a collimator 120, a first polarization beam splitter 130, an acousto-optic modulator 140, a first half-wave plate 150, a triangular mirror 160, a second half-wave plate 170, and a second polarization beam splitter 180.

[0036] The reference element 200 is disposed at the front end of the input optical fiber 110 and is used as an angle reference for the output light. In this application, the reference element is preferably a reference flat crystal.

[0037] In this embodiment, the autocollimator 300 is disposed at the rear end of the second polarization beam splitter 180. The autocollimator 300 visualizes the laser coupling output process and measures in real time the angle that needs to be adjusted to make the output light rotate to match the reference component 200.

[0038] S2, Pre-assembly and screening: Place the optical components naturally on the substrate, measure the adhesive filling angle between the optical components and the substrate, load the optical components into the classic frequency-shifting optical path, sort and number the optical components according to the angle adjustment required for the output light, and screen out the optical components that meet the predetermined requirements.

[0039] The optical element is either the first polarizing beam splitter 130 or the second polarizing beam splitter 180.

[0040] Taking the first polarization beam splitter as an example, different first polarization beam splitters 130 are placed naturally on the mounting substrate in sequence without using adhesive curing. They are then loaded into the above-mentioned classic frequency shifting optical path, and the output light is adjusted to be consistent with the angle reference on the reference component 200. The different first polarization beam splitters 130 are sorted and numbered according to the angle adjustment required for the output light. Then, optical elements that can make the output light angle consistent with the angle reference within a predetermined range are selected.

[0041] The principle of the above screening is that when the first polarizing beam splitter 130 is naturally placed on the mounting substrate, there may be a certain angle between the first polarizing beam splitter 130 and the substrate when the adhesive is not used for curing, i.e., the adhesive filling angle. The substrate itself is generally designed without angle adjustment. That is, if there is no angle between the first polarizing beam splitter 130 and the substrate, the angle adjustment of the first polarizing beam splitter 130 is 0, that is, no adjustment is needed to make the output light emit in the direction specified by the angle reference. If there is an angle between the first polarizing beam splitter 130 and the substrate, the output light will also have a certain angle difference from the direction of the angle reference. Therefore, it is necessary to adjust the first polarizing beam splitter 130 so that the output angle of the output light is consistent with the direction specified by the angle reference. The angle adjusted in this adjustment process is the angle adjustment amount. In this application, optical elements that can output normally without angle adjustment amount not exceeding a certain threshold can be screened out, as well as a small portion of optical elements with very small angle adjustment amounts.

[0042] During the screening process, the angle adjustment amount of each first polarization beam splitter 130 that meets the predetermined requirements is calibrated to ensure that during subsequent normal assembly and adjustment, the gap between the selected first polarization beam splitter 130 and the substrate 131 is not too large and the angle is known, thereby improving the stability, lifespan and temperature resistance of the adhesive bonding.

[0043] When calibrating the angle adjustment, if the output angle deviation is too large, the rear end of the triangular reflector of the autocollimator 300 can be moved to confirm the output angle of the optical element one by one or in pairs.

[0044] S3, Curing Pre-compensation: The first polarizing beam splitter 130 is cured on the substrate with adhesive, the actual linear shrinkage rate of the adhesive is obtained, and the installation angle of the first polarizing beam splitter 130 is pre-compensated according to the change in the angle of adhesive shrinkage.

[0045] The angle pre-compensation is achieved by adjusting the first polarization beam splitter 130 in the opposite direction to the linear shrinkage direction of the adhesive using an angle adjustment device such as an adjustment bracket. In this embodiment, the adjustment bracket is preferably a five-dimensional adjustment bracket.

[0046] like Figure 4 As shown in Figure a, in the prior art, the adhesive is generally filled in a corresponding amount according to the angle between the first polarizing beam splitter 130 and the substrate 131. However, due to the approximately linear shrinkage during the curing process of the UV adhesive 500, after the UV adhesive 500 is cured, the angle between the first polarizing beam splitter 130 and the substrate 131 is no longer the original angle, but an angle value smaller than the original angle. The actual position and actual output angle of the first polarizing beam splitter 130 are shown by the dashed line. Therefore, the angle of the output light L1 also has an angle difference from the angle reference L0, which affects the laser power of the coupled output.

[0047] Therefore, in the embodiments of this application, such as Figure 4 As shown in b, an angle pre-compensation scheme is implemented to address the angle change caused by shrinkage during the curing process of UV adhesive 500. The first polarizing beam splitter 130 is cured on the substrate using UV adhesive 500, and the actual linear shrinkage rate of UV adhesive 500 is obtained. Then, the installation angle of the first polarizing beam splitter 130 is pre-compensated based on the angle change caused by the shrinkage of the adhesive. The actual position and actual light output angle of the first polarizing beam splitter 130 are shown by the dashed line.

[0048] Specifically, assuming the change in the shrinkage angle of the UV adhesive 500 is x, the actual linear shrinkage rate is a, and the angle between the first polarizing beam splitter 130 and the substrate in its natural state is α, then x = a * α, and thus the pre-compensation angle is (a * α) / (1 - a).

[0049] Generally, the actual linear shrinkage rate 'a' is a very small value relative to 1. Therefore, 1-a is approximately equal to 1, so the pre-compensation angle can be directly set as a*α.

[0050] By pre-compensating, the first polarizing beam splitter 130 is pre-deflected by a certain angle in the direction opposite to the linear shrinkage direction of the adhesive. After the UV adhesive cures, the angle between the first polarizing beam splitter 130 and the substrate is the same as the angle under its original natural state. Since the angle adjustment amount of the first polarizing beam splitter 130 is calibrated in step S2, only the first polarizing beam splitter 130 needs to be adjusted according to the calibrated amount to obtain output light consistent with the angle reference. This method pre-compensates for the angle change caused by shrinkage during the curing process, thus ensuring precise control of the output light angle after curing.

[0051] The above description is only a preferred 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 within the protection scope of the present invention.

Claims

1. A method for improving the spatial optical path performance of a cold atom gravimeter, comprising the following steps: S1, Construct an assembly and adjustment optical path, the assembly and adjustment optical path including an assembly and adjustment frequency shift optical path, a reference component and an autocollimator, the assembly and adjustment frequency shift optical path including an input optical fiber, a collimator, a first polarization beam splitter, an acousto-optic modulator, a first half-wave plate, a triangular mirror, a second half-wave plate and a second polarization beam splitter arranged along the light propagation direction, the reference component being disposed at the front end of the input optical fiber, and the autocollimator being disposed at the rear end of the second polarization beam splitter; S2, Pre-assembly and screening: Place the optical components naturally on the substrate, measure the adhesive filling angle between the optical components and the substrate, load the optical components into the classic frequency-shifting optical path, sort and number the optical components according to the angle adjustment required for the output light, and screen out the optical components that meet the predetermined requirements. S3, Curing Pre-compensation: Optical components are cured onto the substrate using adhesive. The actual linear shrinkage rate of the adhesive is obtained. Angle pre-compensation is performed on the mounting angle of the optical components based on the angular change of adhesive shrinkage. Let the angular change of adhesive shrinkage be x, the actual linear shrinkage rate be a, and the adhesive filling angle be α, then x = a. α, the pre-compensation angle is (a α) / (1-a); in, The optical element is either a first polarization beam splitter or a second polarization beam splitter.

2. The method for improving the spatial optical path performance of a cold atom gravimeter according to claim 1, characterized in that, The optical element that meets the predetermined requirements is an optical element whose angle adjustment amount is within a predetermined range so that the output light angle is consistent with the reference element.

3. The method for improving the spatial optical path performance of a cold atom gravimeter according to claim 2, characterized in that, The optical element that meets the predetermined requirements is an optical element that can make the output light angle consistent with the reference element without angle adjustment.

4. The method for improving the spatial optical path performance of a cold atom gravimeter according to claim 1, characterized in that, The adhesive is a UV-curable adhesive.

5. The method for improving the spatial optical path performance of a cold atom gravimeter according to claim 1, characterized in that, The light rays of the classic frequency-shifting optical path are reflected at a right angle at the triangular mirror, and the autocollimator can be moved to the rear end of the triangular mirror.

6. The method for improving the spatial optical path performance of a cold atom gravimeter according to claim 1, characterized in that, The angle pre-compensation includes adjusting the optical element using an adjustment bracket in the opposite direction to the linear contraction direction of the adhesive.

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