A self-compensation cavity matching method and system based on a fast mirror super-stable laser

Abstract

The application discloses a self-compensation cavity matching system and method of an ultra-stable laser based on a fast mirror, and the laser beam is transmitted through a first light splitting prism, and the transmitted light is reflected by an F-P cavity to form signal light, and the signal light is detected and calibrated on a charge coupled device; the ultra-stable laser is deviated due to vibration and other reasons; whether the position of the light spot center changes is judged by the charge coupled device (CCD); the laser beam is reflected by the F-P cavity, and the reflected light is reflected by a 1 / 4 wave plate and a polarization light splitting prism, and then transmitted through a second light splitting prism, and the transmitted light enters the charge coupled unit to detect the position of the signal light spot center; when the position of the light spot detected by S4:S3 does not change, the laser normally works and directly enters the F-P cavity. The self-compensation cavity matching system and method of the ultra-stable laser based on the fast mirror realize automatic compensation of the optical path of the F-P cavity position deviation, and have high cavity matching efficiency and high precision.

Description

Technical Field

[0001] This invention relates to the field of lasers, and more specifically to a self-compensating cavity matching method and system for ultrastable lasers based on fast-reflection mirrors. Background Technology

[0002] Ultrastable lasers possess extremely low frequency noise, extremely high coherence, and excellent short-to-medium-term frequency stability, making them a core light source for high-resolution laser spectroscopy, precise optical frequency control, and precision measurement physics. They also have wide applications in cold atom optical clocks, geodesy, and gravitational wave detection. Due to the wide range of applications of ultrastable lasers, many research groups both domestically and internationally are racing to develop ultrastable lasers (USLs) based on Pound-Drever-Hall (PDH) frequency stabilization technology. The core of PDH frequency stabilization technology lies in the FP reference cavity within the entire ultrastable laser system. While ultrastable lasers operating under relatively stable laboratory conditions exist, with the continuous deepening of scientific research, ultrastable lasers with extremely high frequency stability are needed in many non-laboratory environments and even outer space environments, such as portable optical clock systems and space gravitational wave detection. Therefore, research on ultrastable lasers suitable for portable and space applications is of great significance and value.

[0003] The portability and application of ultrastable lasers still face numerous scientific and technological challenges. One of the core issues is the difficulty in maintaining the required high-precision mode matching between the incident laser and the FP cavity during transport and space missions. This is mainly because the jolting during transport and the mechanical vibrations during rocket launch can cause the FP cavity to shift, directly leading to a deterioration or even failure of the mode matching between the incident laser and the FP cavity. This results in a decrease in the overall performance of the ultrastable laser and even frequency lock-up. Currently, the main solutions fall into two categories: improving the shape and structure of the cavity and improving the support method. However, both methods can only passively compensate for the cavity shift caused by mechanical vibrations and cannot effectively and completely suppress the impact of mechanical vibrations on the cavity shift.

[0004] Therefore, how to accurately measure the offset of the FP cavity after being subjected to mechanical vibration, and then perform optical path active compensation for the offset of the FP cavity, so as to achieve high-precision mode matching between the cavity laser and the FS cavity in transportation and space missions, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The first objective of this invention is to provide a self-compensating cavity matching method for ultrastable lasers based on fast-reflecting mirrors.

[0006] Therefore, the above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0007] A self-compensating cavity matching method for an ultrastable laser based on a fast-reflection mirror includes the following steps:

[0008] S1: After the laser beam passes through the first beam splitter, the transmitted light is reflected by the FP cavity to form a signal light, which is then detected and calibrated on the charge-coupled element.

[0009] S2: The ultra-stable laser is deflected due to vibration or other reasons;

[0010] S3: Determine whether the centroid position of the light spot has changed by detecting the light spot using a charge-coupled device (CCD).

[0011] The laser beam is reflected by the FP cavity, passes through a quarter wave plate, is reflected by a polarizing beam splitter, and then passes through a second beam splitter. The transmitted light enters the charge-coupled unit to detect the centroid of the signal light spot.

[0012] S4: The position of the probe spot in S3 did not change, and the laser was working normally and directly injected into the FP cavity;

[0013] Alternatively, if the position of the probe spot changes, the piezoelectric ceramic actuator will drive the piezoelectric ceramic to produce displacement, causing the fast-reflecting mirror to rotate around its own vertical axis and / or horizontal axis, adjusting the laser direction until the laser is recoupled into the FP cavity.

[0014] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0015] As a preferred technical solution of the present invention: after the charge-coupled device (CCD) detects the reflected light spot, the position of the light spot centroid is calculated using the following gray-scale centroid algorithm:

[0016]

[0017] In the formula: x ij This indicates the calculation of the x-coordinate and y-coordinate of a pixel. ij I represents the calculation of the y-coordinate of a pixel. ij This indicates the calculation of the light intensity value of a pixel.

[0018] As a preferred technical solution of the present invention: when the position of the detection spot changes, the S3 includes the following steps: firstly, quickly control the piezoelectric ceramic inside the reflector to generate displacement, and secondly, quickly control the reflector lens to rotate counterclockwise by 1° around its own vertical axis. Then, quickly control the piezoelectric ceramic inside the reflector to generate displacement, and secondly, quickly control the reflector lens to rotate clockwise by 1° around its own vertical axis. For each 1° rotation, the change in the centroid position of the spot is determined by the spot detected by the charge-coupled element. If the change is within the error range, laser coupling into the cavity is achieved.

[0019] If the above rotation direction causes the spot position to deviate, the first and second fast control mirrors are first restored to their initial state. The piezoelectric ceramic inside the first fast control mirror is displaced, and the first fast control mirror lens rotates 1° clockwise around its vertical axis. The piezoelectric ceramic inside the second fast control mirror is displaced, and the second fast control mirror lens rotates 1° counterclockwise around its vertical axis. Every 1° rotation is used to determine whether the change in the center of mass of the spot meets the error range by detecting the spot position through the charge coupling element. If it does, laser coupling into the cavity is achieved.

[0020] If the rotation in both directions does not meet the error range, then the two fast mirrors are rotated around their own vertical axis to the state of minimum error, so that the two fast mirror lenses remain stationary in the vertical axis direction. The first fast control mirror internal piezoelectric ceramic is displaced, and the first fast control mirror lens is rotated counterclockwise by 1° around its own horizontal axis. The second fast control mirror internal piezoelectric ceramic is displaced, and the second fast control mirror lens is rotated clockwise by 1° around its own horizontal axis. Every 1° rotation is used to determine whether the change in the centroid position of the light spot is within the error range by detecting the light spot through the charge coupling element. If it is within the error range, laser coupling into the cavity is achieved.

[0021] If the aforementioned rotation direction causes the spot position to deviate, the first and second fast control mirrors are first restored to their initial state around their horizontal axis. The piezoelectric ceramic inside the first fast control mirror is displaced, and the first fast control mirror lens rotates 1° clockwise around its horizontal axis. The piezoelectric ceramic inside the second fast control mirror is displaced, and the second fast control mirror lens rotates 1° counterclockwise around its horizontal axis. Every 1° rotation is used to determine whether the change in the center of mass of the spot meets the error range by detecting the spot position through the charge-coupled element. If it does, laser coupling into the cavity is achieved.

[0022] The second objective of this invention is to provide a self-compensating cavity matching system for an ultra-stable laser based on a fast-reflecting mirror.

[0023] Therefore, the above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0024] A self-compensating cavity matching system for an ultra-stable laser based on a fast-reflecting mirror is characterized by the following: a first beam-splitting prism, a half-wave plate, a polarizing beam-splitting prism, a first fast-control mirror, a second fast-control mirror, a quarter-wave plate, a cavity mirror, and a FP cavity are sequentially arranged on the laser optical axis; a second beam-splitting prism is arranged in the reflection path of the polarizing beam-splitting prism, and a charge-coupled device (CCD) is arranged in the transmission path of the second beam-splitting prism; after the laser beam enters the first beam-splitting prism, the transmitted light is directed towards the FP cavity, reflected by the FP cavity, and then passes through the quarter-wave plate... The light, after being reflected by a polarizing beam splitter and then through a second beam splitter, enters the charge-coupled unit (CCD) to detect the centroid of the signal light spot. The CCD measures the change in the position of the centroid of the reflected light spot. The CCD drives the piezoelectric ceramic to move through an SZT (piezoelectric ceramic) driver, thereby driving the first fast control mirror and / or the second fast control mirror. The first fast control mirror and / or the second fast control mirror rotate around their own vertical axis and / or horizontal axis to adjust the laser direction and recouple the laser into the FP cavity.

[0025] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0026] As a preferred technical solution of the present invention: the reflecting surface of the first fast control mirror is at about 45°; the reflecting surface of the second fast control mirror is at about 45°; different rotation directions of the mirror surfaces of the first and second fast control mirrors can produce different optical axis trajectories, so as to achieve the adjustment of the optical axis.

[0027] As a preferred embodiment of the present invention: the piezoelectric ceramic driver circuit drives the piezoelectric ceramic inside the first fast control mirror to generate displacement, thereby causing the first fast control mirror to rotate around its own vertical axis and / or horizontal axis, realizing the translation and pitch direction adjustment of the laser to achieve the cavity matching function; and / or, the piezoelectric ceramic driver circuit drives the piezoelectric ceramic inside the second fast control mirror to generate displacement, thereby causing the second fast control mirror to rotate around its own vertical axis and / or horizontal axis, thereby realizing the translation and pitch direction adjustment of the laser to achieve the cavity matching function.

[0028] Compared with existing technologies, this invention provides an automatic compensation cavity matching method and system for ultra-stable lasers based on fast-reflecting mirrors. It utilizes charge-coupled devices (CCDs) to detect the centroid position of the laser beam, achieving high-precision position determination of the beam reflected back from the cavity. This allows for the measurement of the azimuth and elevation of the FP cavity, obtaining the overall offset of the FP cavity. Furthermore, by controlling a connected piezoelectric ceramic (PZT) driver to precisely adjust the angle of a pair of relatively positioned fast-reflecting mirrors, it achieves precise adjustment of the laser optical path. This forms a closed loop between precise beam pointing measurement and precise optical path adjustment, enabling automatic compensation for the FP cavity position offset. This invention's self-compensating cavity matching method and system for ultra-stable lasers based on fast-reflecting mirrors differs from previous methods that passively reduce FP cavity position offset after impact by improving the FP cavity shape and structure or improving the FP cavity support method. Instead, it provides a novel automatic laser cavity matching technology that forms a closed loop between precise beam pointing measurement and precise optical path adjustment to address the FP cavity position offset, achieving automatic optical path compensation for the FP cavity position offset. The self-compensating cavity matching system for ultrastable lasers based on fast-reflecting mirrors provided by this invention has a simple structure, a complete automatic compensation mechanism, a high degree of automation, and high cavity matching efficiency and accuracy after compensation for FP cavity offset. It has broad application prospects in ultrastable lasers and optical communication fields in portable scenarios and even space applications. Attached Figure Description

[0029] Figure 1 A flowchart of a self-compensating cavity matching system for an ultrastable laser based on a fast-reflection mirror, provided by the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of the self-compensating cavity matching system for an ultrastable laser based on a fast-reflection mirror provided by the present invention.

[0031] Figure 3 This is a schematic diagram of the laser optical path adjustment for rapid control of the mirror pair provided by the present invention;

[0032] In the attached diagram, the first beam splitter 1-1; the second beam splitter 1-2; the half-wave plate 2; the polarizing beam splitter 3; the first fast-control mirror 4-1; the second fast-control mirror 4-2; the quarter-wave plate 5; the cavity mirror 6; the FP cavity 7; the charge-coupled device (CCD) 8; and the piezoelectric ceramic (PZT) driver circuit 9. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] Combination Figure 2 , Figure 3As shown, the present invention discloses a self-compensating cavity matching system for an ultra-stable laser based on a fast-reflecting mirror, comprising a first beam splitter 1-1, a second beam splitter 1-2, a half-wave plate 2, a polarizing beam splitter 3, a first fast-control mirror 4-1, a second fast-control mirror 4-2, a quarter-wave plate 5, a cavity mirror 6, an FP cavity 7, a charge-coupled device (CCD) 8, and a piezoelectric ceramic (PZT) driver circuit 9. A first beam splitter 1-1, a half-wave plate, a polarizing beam splitter 3, a first fast-control mirror 4-1, a second fast-control mirror 4-2, a quarter-wave plate 5, an inlet mirror 6, an FP cavity 7, a charge-coupled device (CCD) 8 are placed sequentially along the optical axis. The second beam splitter 1-2 is placed in the reflection path of the polarizing beam splitter 3, and the CCD 7 is placed in the transmission path of the second beam splitter 1-2. The driving circuit 9 drives the first fast-control mirror 4-1 and the second fast-control mirror 4-2 to rotate, thereby controlling their reflection angles.

[0035] The laser beam reflected back from the surface of the FP cavity 7 is called the signal beam. After passing through the quarter-wave plate 5, the second fast control mirror 4-2, and the first fast control mirror 4-1, the signal beam is reflected by the polarizing beam splitter 3. The reflected laser beam passes through the third beam splitter 1-3 and is transmitted into the charge-coupled device (CCD) 8.

[0036] Before the ultra-stable laser vibrates, the position of the centroid of the signal beam measured by the charge-coupled device (CCD8) is recorded first. After the ultra-stable laser vibrates, the position of the FP cavity 7 will shift, and the position of the centroid of the beam on the CCD8 will change. At this time, the system will drive the first fast control mirror 4-1 and the second fast control mirror 4-2 to rotate through the piezoelectric ceramic (PZT) driver drive circuit 9 to control their reflection angle and adjust the laser direction so that the laser is recoupled into the cavity.

[0037] The reflective surface of the first fast control mirror 4-1 is at approximately 45°; the reflective surface of the second fast control mirror 4-2 is at approximately 45°; different rotation directions of the mirror surfaces of the first and second fast control mirrors can produce different optical axis trajectories, thereby achieving adjustment of the optical axis.

[0038] In existing technologies, the use of wedge prism assemblies results in excessive reflection, refraction, and scattering in the optical path, increasing light loss and attenuation, and affecting the intensity and quality of the optical signal. In this invention, a first and a second fast-control mirror are selected. These mirrors achieve high reflection efficiency, resulting in minimal light loss after passing through them, thus ensuring the required optical signal intensity. This avoids the difficulties encountered with wedge prism assemblies in decoupling data related to changes in the centroid of the light spot caused by cavity offset during optical path adjustment, which hinders the easy achievement of required optical path compensation.

[0039] In this invention, a fast-reflecting mirror group is formed by selecting the first fast-control mirror surface and the second fast-control mirror surface. The adjustment of the optical path is divided into two parts: translation and pitch. It is only necessary to change the relative position of the horizontal axis and vertical axis of the first fast-control mirror surface or the second fast-control mirror surface. The data decoupling for the change of the centroid of the light spot caused by the cavity offset is relatively simple. Compared with the prior art, it is easier to obtain the algorithm implementation.

[0040] When a wedge prism assembly is used to adjust the optical path, the formulas for the maximum adjustment range of its translation and pitch angles are as follows:

[0041] θ 平移max =arctan(d / 2f)

[0042] θ 俯仰max =arctan(d / 2h)

[0043] Where d is the thickness of the wedge prism group, f is the focal length of the lens, and h is the distance from the lens to the wedge prism group.

[0044] Assuming the thickness of the wedge prism assembly is 2cm, the focal length of the lens is 10cm, and the distance from the lens to the wedge prism assembly is 20cm, then according to the formula:

[0045] θ 平移max =arctan(2 / 2*10)=arctan(0.1)≈5.71°

[0046] θ 俯仰max =arctan(2 / 2*20)=arctan(0.05)≈2.86°

[0047] Therefore, the maximum adjustable angles of this wedge prism assembly in the translation and pitch directions are 5.71° and 2.86°, respectively.

[0048] The maximum adjustable angle range can be changed by adjusting the d, f, and h parameters. However, due to limitations in the size, design, and manufacturing precision of the wedge prism, the maximum adjustable angle range is generally between 5° and 10°. Beams exceeding this angle range are difficult to compensate for using the wedge prism assembly. The fast-reflecting mirror assembly used in this invention can achieve ±45° adjustment ranges based on horizontal and vertical axis rotation, thus achieving full coverage of the adjustable light range (180° horizontally and vertically). When the cavity offset is large, corresponding optical path compensation adjustments can also be made.

[0049] The present invention discloses a self-compensating cavity matching system for an ultra-stable laser based on a fast-reflecting mirror. An additional cavity mirror 6 is added in front of the FP cavity 7. If cavity matching of a horizontal cavity is required, the cavity mirror can be removed. However, if cavity matching of a vertical cavity is required, the mirror is generally a mirror perpendicular to the horizontal plane at 45°, which can realize cavity matching and compensation for the vertical cavity.

[0050] This invention discloses a self-compensating cavity matching system for an ultra-stable laser based on a fast-reflecting mirror. It eliminates the need for a four-quadrant detector (QPD), simplifying the optical path and improving efficiency within reasonable limits. Firstly, eliminating the QPD avoids the complexity of QPD data decoupling, which to some extent prevents the implementation of corresponding algorithms. Secondly, the accuracy of the spot centroid position detection of the charge-coupled device (CCD8) in this invention is sufficient to meet the cavity compensation requirements for FP cavity offset.

[0051] like Figure 1 As shown, the self-compensating cavity matching method for ultrastable lasers based on fast-reflection mirrors of the present invention includes the following steps:

[0052] S1: After the laser beam passes through the first beam splitter 1-1, the transmitted light is reflected by the FP cavity 7 to form a signal light, which is detected and calibrated on the charge-coupled device CCD 8.

[0053] S2: The ultra-stable laser is deflected due to vibration or other reasons;

[0054] S3: Determine whether the centroid position of the light spot has changed by detecting the light spot using a charge-coupled device (CCD).

[0055] The laser beam is reflected by the FP cavity, then by the quarter wave plate 5, and by the polarizing beam splitter 3. After passing through the second beam splitter 1-2, the transmitted light enters the charge-coupled unit 8 to detect the centroid position of the signal light spot.

[0056] S4: The position of the probe spot in S3 did not change, and the laser was working normally and directly injected into the FP cavity;

[0057] Alternatively, if the position of the S3 probe spot changes, the piezoelectric ceramic (PZT) driver will be controlled to drive the piezoelectric ceramic to produce displacement, causing the fast-reflecting mirror to rotate around its own vertical axis and / or horizontal axis, adjusting the laser direction until the laser is recoupled into the FP cavity.

[0058] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0059] In this application, when the position of the S3 detector spot changes, the following steps are included:

[0060] The first fast control mirror 4-1 generates displacement of the piezoelectric ceramic inside, and the first fast control mirror lens rotates counterclockwise by 1° around its own vertical axis. The second fast control mirror 4-2 generates displacement of the piezoelectric ceramic inside, and the second fast control mirror lens rotates clockwise by 1° around its own vertical axis. Every 1° rotation is used to determine whether the change in the centroid position of the light spot is within the error range by detecting the light spot through the charge coupling element. If it is within the error range, laser coupling into the cavity is achieved.

[0061] If the above rotation direction causes the spot position to deviate, the first and second fast control mirrors are first restored to their initial state. The piezoelectric ceramic inside the first fast control mirror is displaced, and the first fast control mirror lens rotates 1° clockwise around its vertical axis. The piezoelectric ceramic inside the second fast control mirror is displaced, and the second fast control mirror lens rotates 1° counterclockwise around its vertical axis. Every 1° rotation is used to determine whether the change in the center of mass of the spot meets the error range by detecting the spot position through the charge coupling element. If it does, laser coupling into the cavity is achieved.

[0062] If the rotation in both directions does not meet the error range, then the two fast mirrors are rotated around their own vertical axis to the state of minimum error, so that the two fast mirror lenses remain stationary in the vertical axis direction. The first fast control mirror internal piezoelectric ceramic is displaced, and the first fast control mirror lens is rotated counterclockwise by 1° around its own horizontal axis. The second fast control mirror internal piezoelectric ceramic is displaced, and the second fast control mirror lens is rotated clockwise by 1° around its own horizontal axis. Every 1° rotation is used to determine whether the change in the centroid position of the light spot is within the error range by detecting the light spot through the charge coupling element. If it is within the error range, laser coupling into the cavity is achieved.

[0063] If the aforementioned rotation direction causes the spot position to deviate, the first and second fast control mirrors are first restored to their initial state around their horizontal axis. The piezoelectric ceramic inside the first fast control mirror is displaced, and the first fast control mirror lens rotates 1° clockwise around its horizontal axis. The piezoelectric ceramic inside the second fast control mirror is displaced, and the second fast control mirror lens rotates 1° counterclockwise around its horizontal axis. Every 1° rotation is used to determine whether the change in the center of mass of the spot meets the error range by detecting the spot position through the charge-coupled element. If it does, laser coupling into the cavity is achieved.

[0064] Compared with the prior art, the automatic compensation cavity matching system for ultrastable lasers based on fast-reflection mirrors of the present invention has the following significant advantages:

[0065] (1) Unlike the traditional passive compensation method of improving the shape and support of the reference cavity, this invention realizes active compensation for the positional offset of the FP cavity by precisely measuring the beam direction and adjusting the laser path in a closed loop. Theoretically, this can completely eliminate the influence of cavity offset on cavity matching.

[0066] (2) Based on the fast, efficient and high-precision adjustment of the fast mirror by the piezoelectric ceramic (PZT) driver, the laser optical path can be precisely adjusted. Compared with other optical path adjustment methods, the combined rotation adjustment of the two fast mirrors can realize the translation and pitch adjustment of the laser beam, which is a two-dimensional motion mode, making the whole system highly stable.

[0067] (3) By using a charge-coupled device (CCD) to detect the centroid of the laser spot, the two-dimensional pointing of the laser in azimuth and elevation can be measured, providing data support and foundation for the high-precision adjustment of the laser beam path by the drive circuit.

[0068] Example 1

[0069] Combination Figures 1-3 As shown, in the automatic compensation cavity matching method and system for an ultra-stable laser based on a fast-reflecting mirror of the present invention, a 20mW laser beam first passes through the first beam splitter 1-1. The 10mW light is transmitted through the first beam splitter prism, then passes through a half-wave plate to adjust the polarization direction, and then passes through a polarizing beam splitter 3, a first fast control mirror 4-1, a second fast control mirror 4-2, a quarter-wave plate 5, and a cavity mirror 6 before entering the FP cavity 7. The laser beam reflected back from the FP cavity 7 is called the signal light. After passing through the quarter-wave plate, the second fast control mirror 4-2, and the first fast control mirror 4-1 again, it enters the polarizing beam splitter 3 again. After being reflected by the polarizing beam splitter 3, it enters the second beam splitter 1-3. The 5mW signal light is transmitted into the charge-coupled device (CCD) 8 for spot centroid position detection.

[0070] After the ultra-stable laser vibrates, the position of the FP cavity 7 shifts, causing a change in the position of the centroid of the light spot detected on the charge-coupled element 8. By simultaneously adjusting the displacement of the piezoelectric ceramics inside the first fast control mirror 4-1 and the second fast control mirror 4-2, the mirrors of the first fast control mirror 4-1 and the second fast control mirror 4-2 are rotated synchronously in opposite directions around their own vertical axes, with a step size of 1° and a range of 45°. Each 1° rotation is used to calculate whether the position of the centroid of the light spot on the charge-coupled element 8 is within the error range. If it is not within the error range or even worsens, the rotation direction of the two fast mirrors is reversed, and they continue to rotate synchronously in opposite directions, with a step size of 1° and a range of 45°. Each 1° rotation is used to calculate whether the position of the centroid of the light spot on the charge-coupled element 8 is within the error range. If it still cannot be satisfied, the mirrors are first rotated around their vertical axes... The system moves until the error is minimized, then stops rotating around the vertical axis. Simultaneously, the piezoelectric ceramics inside the first and second fast-control mirrors 4-1 and 4-2 are adjusted to produce displacement, causing the mirrors of the first and second fast-control mirrors 4-1 and 4-2 to rotate synchronously in opposite directions around their own horizontal axes, with a step size of 1° and a range of 45°. For each 1° rotation, the position of the light spot centroid on the charge-coupled element 8 is calculated to ensure it is within the error range. If it still fails to meet the error or even deteriorates, the rotation directions of the two fast-reflecting mirrors are reversed, and they continue to rotate synchronously in opposite directions, with a step size of 1° and a range of 45°, until the position of the light spot centroid on the charge-coupled element 8 is within the error range.

[0071] Figure 3 This diagram illustrates the precise adjustment of the optical path of a fast-reflecting mirror pair. By controlling the rotation of the mirror pair with a piezoelectric ceramic (SZT) driver, the precise pointing adjustment of the laser beam's translation and pitch can be achieved.

[0072] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A self-compensating cavity matching method for an ultrastable laser based on a fast-reflection mirror, comprising the following steps: S1: After the laser beam passes through the first beam splitter, the transmitted light is reflected by the FP cavity to form a signal light, which is then detected and calibrated on the charge-coupled element. S2: The ultra-stable laser is deflected by vibration; S3: Determine whether the centroid position of the light spot has changed by detecting the light spot using a charge-coupled device (CCD). The laser beam is reflected by the FP cavity, passes through a quarter wave plate, is reflected by a polarizing beam splitter, and then passes through a second beam splitter. The transmitted light enters the charge-coupled unit to detect the centroid of the signal light spot. S4: The position of the probe spot in S3 did not change, and the laser was working normally and directly injected into the FP cavity; Alternatively, if the position of the probe spot changes, the piezoelectric ceramic actuator will drive the piezoelectric ceramic to produce displacement, causing the lenses of the first and second fast control mirrors to rotate around their own vertical and / or horizontal axes, respectively. The reflective surfaces of the first and second fast control mirrors are both set at 45°. By coordinating the different rotation directions of the two fast control mirrors around their vertical and / or horizontal axes, different optical axis trajectories are generated to achieve translation and pitch adjustment of the laser beam, thereby decoupling the data from changes in the centroid of the laser spot caused by cavity offset. Furthermore, the first and second fast control mirrors can achieve an adjustment range of ±45° based on rotation of the horizontal and vertical axes to fully cover the adjustable range of light. Adjust the laser direction until the laser is recoupled into the FP cavity.

2. The self-compensating cavity matching method for ultrastable lasers based on fast-reflection mirrors as described in claim 1, characterized in that: After the charge-coupled device (CCD) detects the reflected light spot, the centroid position of the light spot is calculated using the following gray-scale centroid algorithm: ， In the formula: Represents the calculation of pixels x coordinate, Represents the calculation of pixels y coordinate, This indicates the calculation of the light intensity value of a pixel.

3. The self-compensating cavity matching method for ultrastable lasers based on fast-reflection mirrors as described in claim 1, characterized in that: When the position of the S3 detector spot changes, the following steps are included: The first rapid control mirror generates displacement of the piezoelectric ceramic inside, and the first rapid control mirror rotates counterclockwise by 1° around its vertical axis. The second rapid control mirror generates displacement of the piezoelectric ceramic inside, and the second rapid control mirror rotates clockwise by 1° around its vertical axis. Every 1° rotation is used to determine whether the change in the centroid position of the light spot is within the error range by detecting the light spot through the charge coupling element. If it is within the error range, laser coupling into the cavity is achieved. If the above rotation direction causes the spot position to deviate, the first and second fast control mirrors are first restored to their initial state. The piezoelectric ceramic inside the first fast control mirror is displaced, and the first fast control mirror lens rotates 1° clockwise around its vertical axis. The piezoelectric ceramic inside the second fast control mirror is displaced, and the second fast control mirror lens rotates 1° counterclockwise around its vertical axis. Every 1° rotation is used to determine whether the change in the center of mass of the spot meets the error range by detecting the spot position through the charge coupling element. If it does, laser coupling into the cavity is achieved. If the rotation in both directions does not meet the error range, then the two fast mirrors are rotated around their own vertical axis to the state of minimum error, so that the two fast mirror lenses remain stationary in the vertical axis direction. The first fast control mirror internal piezoelectric ceramic is displaced, and the first fast control mirror lens is rotated counterclockwise by 1° around its own horizontal axis. The second fast control mirror internal piezoelectric ceramic is displaced, and the second fast control mirror lens is rotated clockwise by 1° around its own horizontal axis. Every 1° rotation is used to determine whether the change in the centroid position of the light spot is within the error range by detecting the light spot through the charge coupling element. If it is within the error range, laser coupling into the cavity is achieved. If the aforementioned rotation direction causes the spot position to deviate, the first and second fast control mirrors are first restored to their initial state around their horizontal axis. The piezoelectric ceramic inside the first fast control mirror is displaced, and the first fast control mirror lens rotates 1° clockwise around its horizontal axis. The piezoelectric ceramic inside the second fast control mirror is displaced, and the second fast control mirror lens rotates 1° counterclockwise around its horizontal axis. Every 1° rotation is used to determine whether the change in the center of mass of the spot meets the error range by detecting the spot position through the charge-coupled element. If it does, laser coupling into the cavity is achieved.

4. The self-compensating cavity matching method for ultrastable lasers based on fast-reflection mirrors as described in any one of claims 1-3, characterized in that: A first beam splitter, a half-wave plate, a polarizing beam splitter, a first fast control mirror, a second fast control mirror, a quarter-wave plate, an entrance mirror, and an FP cavity are sequentially arranged on the laser optical axis. A second beam splitter is placed in the reflection path of the polarizing beam splitter, and a charge-coupled device (CCD) is placed in the transmission path of the second beam splitter. After the laser beam enters the first beam splitter, the transmitted light is directed towards the FP cavity, reflected by the FP cavity, passes through the quarter-wave plate, is reflected by the polarizing beam splitter, passes through the second beam splitter, and then enters the CCD to detect the centroid of the signal light spot. The CCD measures the change in the position of the centroid of the reflected light spot. The charge-coupled element drives the piezoelectric ceramic to move through the piezoelectric ceramic actuator, thereby driving the first fast control mirror and / or the second fast control mirror to rotate around its own vertical axis and / or horizontal axis to adjust the laser direction so that the laser is recoupled into the FP cavity.

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