Crystal angle measuring and adjusting device and method for off-axis pumping folded laser

Abstract

The invention discloses a crystal angle measuring and adjusting device and method for an off-axis pump folded laser. The device comprises a control terminal, a visible light camera, a precision displacement platform, an electric control displacement platform, a micron pumping source, a collimating focusing lens group, an incident plane-concave end mirror, a 2-micron laser crystal, a high-reflectivity plane-concave end mirror, an output coupling mirror OC, a diaphragm B, a 2-micron total reflective mirror, a helium-neon laser, a red light total reflective mirror and a diaphragm A; the method comprises the steps that the helium-neon laser outputs a red laser beam as a measuring beam, the red light total reflection mirror reflects and outputs the measuring beam, the measuring beam enters the right end face of the 2-micron laser crystal after passing through the high-reflection plano-concave end mirror, then the measuring beam is reflected to the high-reflection plano-concave end mirror through the right end face of the 2-micron laser crystal and then reflected to the diaphragm A through the high-reflection plano-concave end mirror, and the measuring beam is measured through the high-reflection plano-concave end mirror. Collecting an image through a visible light camera, and determining a light spot position through a control terminal; and the 2-micron laser crystal is adjusted by using the light spot position so as to ensure the stable transmission of the laser. The device and the method can realize automatic adjustment of the position and the angle of the crystal.

Description

Technical Field

[0001] The invention belongs to the technical field of 2-micron laser control, and in particular relates to a crystal angle measurement and adjustment device and method for off-axis pumped folded lasers. Background Art

[0002] With the continuous development of science and technology, laser technology has become an indispensable part of modern industry and scientific research. Especially in high-precision, multi-dimensional ultrafast laser systems, laser control technology has become one of the key technologies. With the widespread application of 2-micron lasers in laser radar, high-precision medical treatment, precision material processing and other fields, the requirements for laser debugging efficiency and operation stability are getting higher and higher. Non-collinear pump lasers can adjust the pump beam incident angle and pump spot shape of the gain medium, and can significantly improve the generation efficiency of high-order modes in the cavity, thereby achieving direct generation of high-order modes in the laser. However, the upconversion light intensity of the 2-micron laser is very weak, and it is difficult to capture it with a visible light probe. It cannot be judged by upconversion green light like a 3-micron laser. At the same time, in the design and debugging process of off-axis pump lasers, the alignment accuracy of optical components (such as laser crystals and cavity mirrors) in the laser cavity is a key factor affecting the performance of the laser. Especially for off-axis pumped folded cavity structure lasers, the matching of pump light and laser cavity mode is crucial. However, due to the multiple reflections of the light beam through the crystal in the off-axis pumping mode, a slight deviation in the crystal angle will lead to intracavity mode mismatch, which will seriously affect the laser output performance and even cause the laser to fail to emit light. Therefore, how to efficiently and accurately adjust the angle of the laser crystal and quickly find the beam path when the laser fails has become a core technical issue in the design and application of high-performance lasers.

[0003] At present, the main problems in off-axis pumping configuration are as follows: (1) The matching of the tilt angle of the pump beam and the crystal angle has extremely high requirements on the laser cavity mode. A slight angle deviation will significantly change the beam path in the cavity, which will affect the output performance of the laser. (2) During the debugging process of the laser, traditional crystal alignment relies on manual repeated adjustment and observation of the changes in the output light. This method is time-consuming and difficult to control accurately. (3) During operation, the laser may cause the intracavity beam to be misaligned due to thermal effects, mechanical vibrations or aging of optical components, resulting in a failure to emit light normally. In this case, it is particularly important to quickly restore the laser light output position.

[0004] At present, the following methods are mainly used for crystal adjustment and optical path recovery of off-axis pump lasers: (1) External measurement equipment assistance: Use laser interferometer or wavefront sensor to monitor the optical path status in real time to guide the crystal angle adjustment. This method has high precision, but the equipment is complex and expensive, and is not suitable for industrial application. (2) Manual experience debugging: Adjust the crystal angle and position until the laser emits light. This method is highly dependent on the experience of the debugging personnel and takes a long time to debug, which makes it difficult to meet the requirements of high efficiency and high stability. (3) Fixed cavity structure: Reduce the possibility of optical path misalignment by precisely processing and fixing the optical elements in the cavity. However, this method is difficult to cope with the optical path deviation caused by environmental changes (such as thermal effects) during laser operation. The above methods have failed to achieve efficient adjustment and rapid recovery of laser optical elements under low-cost and easy-to-operate conditions. To this end, it is urgent to provide a low-cost and easy-to-operate crystal angle measurement and adjustment device for off-axis pump folding lasers. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a crystal angle measurement and adjustment device and method for off-axis pumped folded lasers. The device has a reasonable structure, low manufacturing cost, high modularity, and is easy to operate. It can automatically adjust the angle and position of the laser crystal, thereby ensuring the stable output of the laser; the method can realize automatic adjustment of the position and angle of the laser crystal, minimize manual intervention, and restore the normal light output of the laser by automatically adjusting the crystal angle and position.

[0006] In order to achieve the above-mentioned object, the present invention provides a crystal angle measurement and adjustment device for off-axis pumped folded laser, comprising an automatic control subsystem, a laser cavity system and a laser calibration subsystem;

[0007] The automatic control subsystem includes a control terminal, a visible light camera, a precision displacement platform and an electric control displacement stage;

[0008] The laser cavity system comprises a micron pump source, a collimating and focusing lens group, an incident plano-concave end mirror, a 2μm laser crystal, a high-reflection plano-concave end mirror, an output coupling mirror OC, an aperture B and a 2μm total reflection mirror;

[0009] The laser calibration subsystem includes a helium-neon laser, a red light total reflector and an aperture A;

[0010] The end face of the 2μm laser crystal is highly transparent to the pump light and highly reflective to the measuring light, and the end face is used to reflect the measuring light beam; the 2μm laser crystal is mounted on a precision displacement platform, and the precision displacement platform is used to drive the angle of the 2μm laser crystal to change; the precision displacement platforms are all mounted on the bearing platform of the electric-controlled displacement platform, and the electric-controlled displacement platform is used to adjust the position of the bearing platform;

[0011] The collimating and focusing lens group, the incident plano-concave end mirror, the 2μm laser crystal, the high-reflection plano-concave end mirror and the red light total-reflecting mirror are sequentially spaced from left to right in the transverse direction; the collimating and focusing lens group is used to ensure that the pump light beam has high parallelism when incident on the end face of the 2μm laser crystal; the concave surfaces of the incident plano-concave end mirror and the high-reflection plano-concave end mirror are both located on the side close to the 2μm laser crystal, and the intersection of the axis of the incident plano-concave end mirror and the axis of the high-reflection plano-concave end mirror is located on the rear side of the axis of the collimating and focusing lens group;

[0012] The output coupling mirror OC is arranged at the left part of the rear side of the 2μm laser crystal and is distributed opposite to the high-reflection plano-concave end mirror; the output coupling mirror OC is used to adjust its reflectivity or transmittance to balance the light intensity of the output energy beam and the output light intensity of the 2μm folded laser cavity to control the output power and beam quality of the laser; the aperture A is a barrier with scale marks, which is arranged on the optical path between the output coupling mirror OC and the high-reflection plano-concave end mirror and is used to receive the light spot of the measurement beam reflected by the high-reflection plano-concave end mirror; the 2μm total reflection mirror is arranged at the right part of the rear side of the 2μm laser crystal and is distributed opposite to the incident plano-concave end mirror ; The aperture B is a barrier without scale marks, which is set on the optical path between the incident plano-concave end mirror and the 2μm total reflection mirror, and is used to fix the optical path when the helium-neon laser emits a measuring beam and the 2μm laser crystal is removed, so as to ensure the fixation of the positions of the incident plano-concave end mirror and the high-reflection plano-concave end mirror; the direction of the outgoing optical path of the red light total reflection mirror coincides with the axis of the collimating and focusing lens group, and is used to reflect the measuring beam to the high-reflection plano-concave end mirror; the incident plano-concave end mirror, the 2μm laser crystal, the high-reflection plano-concave end mirror, the output coupling mirror OC and the high-reflectivity end mirror HR cooperate with each other to form a 2μm folded laser cavity;

[0013] The micron pump source is arranged on the left side of the collimating and focusing lens group, and the direction of its outgoing light path coincides with the axis of the collimating and focusing lens group, and is used to emit a pump light beam;

[0014] The helium-neon laser is arranged on the incident light path of the red light total reflector, and is used to emit a detection light beam to the incident light path of the red light total reflector;

[0015] The visible light camera is arranged on one side of the aperture A, and its acquisition window faces the aperture A, and is used to acquire an image of the light spot position on the aperture A in real time and send it to the control terminal;

[0016] The control terminal is respectively connected to the visible light camera, the precision displacement platform and the electric-controlled displacement platform, and is used to calculate the deviation between the spot position and the preset reference position according to the image collected by the visible light camera, calculate the relationship between the spot position and the angle of the 2μm laser crystal according to the image collected by the visible light camera, and perform real-time calculation of the deflection angle of the 2μm laser crystal. At the same time, it is used to feedback control the precision displacement platform and the electric-controlled displacement platform according to the deviation, so as to automatically adjust the angle and position of the 2μm laser crystal to the target posture.

[0017] As a preference, the control terminal is a computer.

[0018] As a preferred embodiment, the control terminal is connected to the visible light camera, the precision displacement platform and the electric-controlled displacement stage through a python platform.

[0019] As a preference, it further comprises a photoelectric detector connected to the control terminal, wherein the photoelectric detector is arranged at the output side of the output coupling mirror OC and is used for detecting the power and stability of the output laser in real time.

[0020] Preferably, the precision displacement platform is a high-precision angle adjustment mechanism driven by a stepping motor or piezoelectric ceramics.

[0021] Preferably, the 2 μm laser crystal is a holmium-doped or thulium-doped crystal, and the pump wavelength is two microns.

[0022] Furthermore, in order to ensure stability during long-term operation, the aperture A and the aperture B are both made of high-temperature resistant metal or wear-resistant alloy material.

[0023] In the present invention, by setting scale marks on the aperture A, the position of the light spot can be accurately identified and the position of the light spot can be recorded. The 2μm laser crystal is made highly transparent to the pump light and highly reflective to the measuring light. At the same time, an incident plano-concave end mirror and a high-reflection plano-concave end mirror are respectively set on both sides thereof, so that the pump light beam incident on the 2μm laser crystal through the incident plano-concave end mirror can pass normally, and is reflected by the high-reflection plano-concave end mirror and then incident on the output coupling mirror O through the aperture A for output. At the same time, it can be ensured that the measuring light beam incident on the 2μm laser crystal through the high-reflection plano-concave end mirror can be directly reflected to the high-reflection plano-concave end mirror, and then reflected to the aperture A. Therefore, the spot position of the measuring light beam on the aperture A can be adjusted by adjusting the angle and position of the 2μm laser crystal, and then the stable output of the laser can be ensured by adjusting the spot position. The 2μm laser crystal is mounted on a precision displacement platform, so that the angle of the 2μm laser crystal can be easily adjusted. Installing the precision displacement platform on the carrier of the electric displacement stage can facilitate the flexible adjustment of the position of the 2μm laser crystal. Setting the collimating focusing lens group between the micron pump source and the incident plano-concave end mirror can ensure that the pump beam has high parallelism when it is incident on the end face of the 2μm laser crystal. The output power and beam quality of the laser can be ensured by setting the output coupling mirror OC.

[0024] The device has a reasonable structure, low manufacturing cost, high modularity and is easy to operate. It can automatically adjust the angle and position of the laser crystal, thereby ensuring stable laser output. At the same time, it is easy to integrate into existing laser equipment and can flexibly adjust optical path parameters (such as aperture position, laser crystal installation angle, etc.) according to different laser cavity structures, and has good scalability.

[0025] The present invention also provides a method for measuring and adjusting the crystal angle for an off-axis pumped folded laser, using a device for measuring and adjusting the crystal angle for an off-axis pumped folded laser, comprising the following steps:

[0026] Step 1: Start the He-Ne laser and use it to output a red laser beam to the incident light path of the red light total reflector as the measurement beam;

[0027] Step 2: Use the red light total reflection mirror to reflect the measuring beam to the high reflection plano-concave end mirror. At the same time, use the transmission effect of the high reflection plano-concave end mirror to make the measuring beam incident on the right end face of the 2μm laser crystal. Then, use the reflection effect of the right end face of the 2μm laser crystal to reflect the measuring beam to the high reflection plano-concave end mirror. Then use the reflection effect of the high reflection plano-concave end mirror to reflect the measuring beam to aperture A. Use aperture A to receive the light spot in the measuring beam.

[0028] Step 3: Start and adjust the micron pump source to emit pump light to the axis position of the collimating and focusing lens group; use the collimating and focusing lens group to adjust the direction and shape of the pump light beam to a parallel light beam, and then make the parallel pump light beam incident on the incident plano-concave end mirror, and use the transmission effect of the incident plano-concave end mirror to make the pump light beam incident on the 2μm laser crystal, and then pass through the 2μm laser crystal to be incident on the high-reflection plano-concave end mirror, and then after being reflected by the high-reflection plano-concave end mirror, it passes through the aperture A and is incident on the output coupling mirror OC, so as to balance the light intensity of the output light beam and the output light intensity through the output coupling mirror OC, thereby controlling the output power and beam quality of the laser;

[0029] Step 4: Adjust the deflection angle of the 2μm laser crystal, use the visible light camera to collect the image of the spot position on the aperture A in real time, and send it to the control terminal. The control terminal calculates and outputs the deflection angle α of the 2μm laser crystal in real time based on the image collected by the visible light camera;

[0030] When the 2μm folded laser cavity successfully outputs a light beam for the first time, the control terminal calculates and records the current light spot position based on the image captured by the visible light camera, and uses the current light spot position as the preset reference position;

[0031] When the 2μm folded laser cavity cannot output a beam normally, the control terminal calculates the deviation between the current spot position and the preset reference position based on the image captured by the visible light camera, and controls the precision displacement platform and the electric-controlled displacement stage based on the deviation to automatically adjust the deflection angle and position of the 2μm laser crystal until the current spot position is consistent with the preset reference position, so that the 2μm folded laser cavity is restored to a normal output state;

[0032] Step 5: When the output operation of the 2μm folded laser cavity is completed, first adjust the deflection angle and position of the 2μm laser crystal to ensure that the current spot position on aperture A is consistent with the preset reference position, then fix the deflection angle and position of the 2μm laser crystal, and then turn off the micron pump source.

[0033] As a preferred embodiment, in step 4, the calculation process of the deflection angle α is as follows:

[0034] S41: Based on the reflection principle, the offset Δd of the spot position on aperture A after reflection by the high-reflection plano-concave end mirror is calculated according to formula (1) when the 2μm laser crystal is slightly deflected. 平面 ;

[0035] Δd 平面 =2D1·tan(2α) (1);

[0036] Where D1 is the horizontal distance from the right end face of the 2μm laser crystal to the left end face of the high-reflection plano-concave end mirror;

[0037] S42: Calculate the offset Δd of the corrected spot position on aperture A according to formula (2): total ;

[0038] Δd total =ΔD 曲率 +Δd 平面 (2);

[0039] In the formula, Δd 曲率 is the offset of the arc propagation of the light beam caused by the curvature of the concave surface of the high-reflection plano-concave end mirror, Among them, R c is the curvature radius of the concave surface of the high-reflection plano-concave end mirror; D2 is the horizontal distance from the aperture A to the left end surface of the high-reflection plano-concave end mirror;

[0040] S43: transform formula (2) to obtain formula (3);

[0041]

[0042] S44: transform formula (3) to obtain formula (4);

[0043]

[0044] Furthermore, in order to ensure the stability of the reflected light spot and the accuracy of the measurement, in step one, the collimation error of the light beam emitted by the helium-neon laser is less than 0.5 mrad.

[0045] The present invention proposes a crystal angle measurement and calibration technology based on the change of red light reflection position, which uses the principle of geometric optics combined with automatic calculation and feedback control to achieve real-time adjustment of the crystal angle and rapid recovery of the laser optical path. Specifically, it relates to a 2-micron laser control technology, which amplifies the crystal deflection angle through the law of reflection, calculates the tiny angle change of the crystal through the displacement at the aperture, and realizes the integration of angle calculation and optical path control. In the process of adjusting the angle of the 2μm laser crystal, an automatic adjustment method is adopted. The adjustment process collects image data in real time through a visible light camera and sends it to the control terminal. The control terminal determines the spot position according to the image data and calculates the deflection angle; when the laser cavity successfully emits light for the first time, the spot position of the red light on the aperture A is first recorded as a calibration reference point. When the laser fails later, the deviation comparison between the spot position and the preset reference position is performed to realize closed-loop control of the crystal angle, thereby realizing automatic adjustment of the crystal position and angle, which can minimize manual intervention and restore the normal light emission of the laser by automatically adjusting the crystal angle and position.

[0046] Compared with the prior art, the present invention has at least the following advantages:

[0047] 1. High precision and high efficiency of crystal angle adjustment: The present invention can achieve high-precision adjustment of the crystal angle through real-time detection of the red light spot position and geometric optical calculation, combined with the automatic control process of the control terminal. Compared with the traditional manual debugging method, the adjustment efficiency can be greatly improved. At the same time, it can ensure that the crystal angle adjustment response time is shorter, and the precise correction of the optical path in the laser cavity during the dynamic adjustment process can be achieved, ensuring the stability of the intracavity mode.

[0048] 2. The efficiency of the first laser debugging is greatly improved; the change in the red light reflection position is used to intuitively monitor the crystal angle deviation, without relying on complex interferometers or manual repeated attempts, which simplifies the debugging process of the first laser cavity light output.

[0049] 3. High reliability of optical path calibration and fault recovery functions; the present invention provides an optical path calibration function, which records the calibration position of the red light spot when the laser cavity emits light for the first time. When the optical path of the laser is misaligned due to vibration, thermal effect, etc., the system automatically adjusts the crystal position and angle by comparing the light spot position deviation to restore the optical path to the calibrated state. In actual tests, when the laser is unable to emit light due to external vibration, the system quickly adjusts the crystal position through the calibration point, shortening the optical path recovery time to less than 2 minutes, significantly improving the operating stability of the laser.

[0050] 4. System intelligence and ease of use: The present invention can be effectively combined with the Python control platform, and can have a friendly user interface and efficient data processing capabilities, and can realize real-time monitoring of crystal angles, automatic adjustment, and intelligent feedback of optical path status, so that users can operate the system through the control terminal interface without professional optical knowledge, and can quickly complete the debugging and maintenance of the laser, which significantly reduces the difficulty of operation and the dependence on the technical level of personnel.

[0051] 5. Applicability and scalability: The present invention is applicable to various types of laser systems, especially off-axis pumped folded cavity lasers, covering high-power lasers in the 2μm band, ultrafast lasers and other precision laser application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic diagram of the structure of the present invention;

[0053] Figure 2 Schematic diagram of the structure of the aperture A in the present invention;

[0054] Figure 3 It is a schematic diagram of the principle of calculating the deflection angle of the present invention.

[0055] In the figure: 1. Automatic control subsystem, 1-1. Control terminal, 1-2. Visible light camera, 1-3. Precision displacement platform, 1-4. Electric control displacement stage; 2. Laser cavity system, 2-1. Micron pump source, 2-2. Collimating and focusing lens group, 2-3. Incident plano-concave end mirror, 2-4. 2μm laser crystal, 2-5. High reflection plano-concave end mirror, 2-6. Output coupling mirror OC, 2-7. Aperture B, 2-8. 2μm total reflection mirror; 3. Laser calibration subsystem, 3-1. He-Ne laser, 3-2. Red light total reflection mirror, 3-3. Aperture A. DETAILED DESCRIPTION

[0056] The present invention will be described clearly and completely below in conjunction with the accompanying drawings. The described embodiments are only part of the embodiments of the present invention, but not all of them.

[0057] like Figures 1 to 3 As shown, the present invention provides a crystal angle measurement and adjustment device for off-axis pumped folded lasers, comprising an automatic control subsystem 1, a laser cavity system 2 and a laser calibration subsystem 3;

[0058] The automatic control subsystem 1 includes a control terminal 1-1, a visible light camera 1-2, a precision displacement platform 1-3 and an electric-controlled displacement stage 1-4; the electric-controlled displacement stage 1-4 is preferably driven by a stepper motor to ensure control accuracy.

[0059] The laser cavity system 2 includes a micron pump source 2-1, a collimating and focusing lens group 2-2, an incident plano-concave end mirror 2-3, a 2μm laser crystal 2-4, a high-reflection plano-concave end mirror 2-5, an output coupling mirror OC2-6, an aperture B2-7 and a 2μm total reflection mirror 2-8;

[0060] The laser calibration subsystem 3 includes a helium-neon laser 3-1, a red light total reflector 3-2 and an aperture A3-3;

[0061] The end face of the 2μm laser crystal 2-4 is highly transparent to the pump light and highly reflective to the measuring light, and the end face is used to reflect the measuring light beam; the 2μm laser crystal 2-4 is mounted on a precision displacement platform, and the precision displacement platform 1-3 is used to drive the angle of the 2μm laser crystal 2-4 to change; the precision displacement platforms 1-3 are all mounted on the bearing platform of the electric-controlled displacement platform 1-4, and the electric-controlled displacement platform 1-4 is used to adjust the position of the bearing platform;

[0062] The collimating and focusing lens group 2-2, the incident plano-concave end mirror 2-3, the 2μm laser crystal 2-4, the high-reflection plano-concave end mirror 2-5 and the red light total reflection mirror 3-2 are sequentially spaced from left to right in the transverse direction; the collimating and focusing lens group 2-2 is used to ensure that the pump light beam has high parallelism when incident on the end face of the 2μm laser crystal 2-4; the concave surfaces of the incident plano-concave end mirror 2-3 and the high-reflection plano-concave end mirror 2-5 are both located on the side close to the 2μm laser crystal 2-4, and the intersection of the axis of the incident plano-concave end mirror 2-3 and the axis of the high-reflection plano-concave end mirror 2-5 is located on the rear side of the axis of the collimating and focusing lens group 2-2;

[0063] The output coupling mirror OC2-6 is arranged on the left side of the rear side of the 2μm laser crystal 2-4 and is distributed opposite to the high-reflection plano-concave end mirror 2-5; the output coupling mirror OC2-6 is used to adjust its reflectivity or transmittance to balance the light intensity and output light intensity of the output energy beam of the 2μm folded laser cavity to control the output power and beam quality of the laser; the aperture A3-3 is a barrier with scale marks, which is arranged on the optical path between the output coupling mirror OC2-6 and the high-reflection plano-concave end mirror 2-5 and is used to receive The light spot of the measuring beam is reflected by the high-reflection plano-concave end mirror 2-5; the 2μm total reflection mirror 2-8 is arranged on the right part of the rear side of the 2μm laser crystal 2-4, and is distributed opposite to the incident plano-concave end mirror 2-3; the aperture B2-7 is a barrier without scale marks, which is arranged on the optical path between the incident plano-concave end mirror 2-3 and the 2μm total reflection mirror 2-8, and is used to fix the optical path when the helium-neon laser 3-1 emits the measuring beam and the 2μm laser crystal 2-4 is removed, so as to ensure that the incident The positions of the plano-concave end mirror 2-3 and the high-reflection plano-concave end mirror 2-5 are fixed. Specifically, when the 2μm laser crystal 2-4 is removed from between the plano-concave end mirror 2-3 and the high-reflection plano-concave end mirror 2-5, the measuring light beam passing through the high-reflection plano-concave end mirror 2-5 is incident on the plano-concave end mirror 2-3, and then after being reflected by the plano-concave end mirror 2-3, it passes through the aperture B2-7 and is incident on the 2μm total reflection mirror 2-8. When the measuring light beam appears on the total reflection mirror 2-8, the positions of the plano-concave end mirror 2-3 and the high-reflection plano-concave end mirror 2-5 are positive. The correct installation position; the outgoing light path direction of the red light total reflection mirror 3-2 coincides with the axis line of the collimating and focusing lens group 2-2, and is used to reflect the measuring light beam to the high-reflection plano-concave end mirror 2-5; the incident plano-concave end mirror 2-3, the 2μm laser crystal 2-4, the high-reflection plano-concave end mirror 2-5, the output coupling mirror OC2-6 and the high-reflectivity end mirror HR2-8 cooperate with each other to form a 2μm folded laser cavity; as a preferred embodiment, the high-reflection plano-concave end mirror 2-5 is a plano-concave mirror with high transmittance to the pump light and high reflectivity to the measuring light.

[0064] The micron pump source 2-1 is arranged on the left side of the collimating and focusing lens group 2-2, and its outgoing light path direction coincides with the axis of the collimating and focusing lens group 2-2, and is used to emit a pump beam; as a preferred embodiment, the micron pump source 2-1 is a semiconductor laser that can be remotely controlled, and its central wavelength can be drift-controlled by adjusting the temperature, and has an external port, specifically RS-232 or USB3.0. Communication protocols can be developed, including but not limited to wavelengths such as 793nm, 976nm, etc., and output power includes but is not limited to 12W.

[0065] The helium-neon laser 3-1 is arranged on the incident light path of the red light total reflector 3-2, and is used to emit a detection light beam to the incident light path of the red light total reflector 3-2;

[0066] The visible light camera 1-2 is arranged on one side of the aperture A3-3, and its acquisition window faces the aperture A3-3, and is used to acquire an image of the light spot position on the aperture A3-3 in real time and send it to the control terminal 1-1;

[0067] The control terminal 1-1 is respectively connected to the visible light camera 1-2, the precision displacement platform 1-3 and the electric-controlled displacement platform 1-4, and is used to calculate the deviation of the spot position from the preset reference position according to the image captured by the visible light camera 1-2 (specifically, the image processing algorithm can be used to convert the position of the spot relative to the preset reference position into a numerical offset), calculate the relationship between the spot position and the angle of the 2μm laser crystal 2-4 according to the image captured by the visible light camera 1-2, and perform real-time calculation of the deflection angle of the 2μm laser crystal 2-4. This process can be calculated through a preset geometric optical model. At the same time, it is used to feedback control the precision displacement platform 1-3 and the electric-controlled displacement platform 1-4 according to the deviation, so as to automatically adjust the angle and position of the 2μm laser crystal 2-4 to the target posture.

[0068] As a preference, the control terminal 1-1 is a computer.

[0069] As a preferred embodiment, the control terminal 1-1 is connected to the visible light camera 1-2, the precision displacement platform 1-3 and the electric control displacement platform 1-4 through a python platform. Preferably, the python platform can communicate with external devices in a wired or wireless manner through high-speed data interfaces such as RS-232 interface, USB interface, Bluetooth interface, network interface LAN and GPIB;

[0070] As a preferred embodiment, it also includes a photodetector connected to the control terminal 1-1, and the photodetector is arranged on the output side of the output coupling mirror OC2-6, and is used for real-time detection of the power and stability of the output laser.

[0071] As a preferred embodiment, the precision displacement platform 1-3 is a high-precision angle adjustment mechanism driven by a stepper motor or piezoelectric ceramics. It is further preferred to use a stepper motor for driving to ensure control accuracy.

[0072] As a preference, the 2μm laser crystals 2-4 are holmium-doped or thulium-doped crystals, and the pump wavelength is two microns, such as Tm:CYA, Tm:YAG, etc.

[0073] In order to ensure stability during long-term operation, the aperture A3-3 and the aperture B2-7 are both made of high-temperature resistant metal or wear-resistant alloy material.

[0074] The device has a reasonable structure, low manufacturing cost, high modularity and is easy to operate. It can automatically adjust the angle and position of the laser crystal, thereby ensuring stable laser output. At the same time, it is easy to integrate into existing laser equipment and can flexibly adjust optical path parameters (such as aperture position, laser crystal installation angle, etc.) according to different laser cavity structures, and has good scalability.

[0075] The present invention also provides a method for measuring and adjusting the crystal angle for an off-axis pumped folded laser, using a device for measuring and adjusting the crystal angle for an off-axis pumped folded laser, comprising the following steps:

[0076] Step 1: Start the He-Ne laser 3-1, and use the He-Ne laser 3-1 to output a red laser beam to the incident light path of the red light total reflector 3-2, and use it as a measurement beam;

[0077] Step 2: Use the red light total reflection mirror 3-2 to reflect the measuring beam to the high reflection plano-concave end mirror 2-5. At the same time, use the transmission effect of the high reflection plano-concave end mirror 2-5 to make the measuring beam incident on the right end face of the 2μm laser crystal 2-4. Then, use the reflection effect of the right end face of the 2μm laser crystal 2-4 to reflect the measuring beam to the high reflection plano-concave end mirror 2-5. Then use the reflection effect of the high reflection plano-concave end mirror 2-5 to reflect the measuring beam to the aperture A3-3. Use the aperture A3-3 to receive the light spot in the measuring beam.

[0078] Step three: Start and adjust the micron pump source 2-1, and emit pump light to the axial position of the collimating and focusing lens group 2-2; use the collimating and focusing lens group 2-2 to adjust the direction and shape of the pump light beam to a parallel light beam, and then make the parallel pump light beam incident on the incident plano-concave end mirror 2-3, and use the transmission effect of the incident plano-concave end mirror 2-3 to make the pump light beam incident on the 2μm laser crystal 2-4, and then pass through the 2μm laser crystal 2-4 to be incident on the high-reflection plano-concave end mirror 2-5, and then after being reflected by the high-reflection plano-concave end mirror 2-5, it is incident on the output coupling mirror OC2-6 through the aperture A3-3, so as to balance the light intensity of the output light beam and the output light intensity through the output coupling mirror OC2-6, thereby controlling the output power and beam quality of the laser;

[0079] Among them, the measurement beam and the pump beam are cross-distributed, but the two operate independently and do not interfere with each other;

[0080] Step 4: Adjust the deflection angle of the 2μm laser crystal 2-4, use the visible light camera 1-2 to collect the image of the spot position on the aperture A3-3 in real time, and send it to the control terminal 1-1. The control terminal 1-1 calculates and outputs the deflection angle α of the 2μm laser crystal 2-4 in real time according to the image collected by the visible light camera 1-2;

[0081] When the 2μm folded laser cavity successfully outputs a light beam for the first time, preferably in the optimal light output state, the control terminal 1-1 calculates and records the current light spot position according to the image collected by the visible light camera 1-2, and uses the current light spot position as the preset reference position; this process is the calibration process of the preset reference position;

[0082] When the 2μm folded laser cavity cannot output a light beam normally, the control terminal 1-1 calculates the deviation between the current light spot position and the preset reference position according to the image collected by the visible light camera 1-2, and feedback controls the precision displacement platform 1-3 and the electric control displacement platform 1-4 according to the deviation to automatically adjust the deflection angle and position of the 2μm laser crystal 2-4 until the current light spot position is consistent with the preset reference position, so that the 2μm folded laser cavity is restored to a normal output state;

[0083] Step 5: When the output operation of the 2μm folded laser cavity is completed, first adjust the deflection angle and position of the 2μm laser crystal 2-4 to ensure that the current spot position on the aperture A3-3 is consistent with the preset reference position, then fix the deflection angle and position of the 2μm laser crystal 2-4, and then turn off the micron pump source 2-1.

[0084] Principle of measuring the angle of the auxiliary reflection of the measuring beam: In the 2μm folded laser cavity, the measuring beam (such as the red light beam emitted by the helium-neon laser) is introduced as an auxiliary light source. The measuring beam is vertically incident on the 2μm laser crystal 2-4, and forms a reflected beam after being reflected by the end face. The optical path of the reflected beam is directly affected by the angle of the 2μm laser crystal 2-4. When the 2μm laser crystal 2-4 is deflected at a small angle, the emission direction of its reflected beam will change, resulting in a significant shift in the position of the reflected light spot on the distant aperture A3-3. The longer the optical path, the more obvious the shift.

[0085] Specifically, in step 4, the calculation process of the deflection angle α is as follows:

[0086] S41: Based on the reflection principle, the offset Δd of the spot position on the aperture A3-3 after being reflected by the high-reflection plano-concave end mirror 2-5 is calculated according to formula (1) when the 2μm laser crystal 2-4 is slightly deflected. 平面 ;

[0087] Δd 平面 =2D1·tan(2α) (1);

[0088] Wherein, D1 is the horizontal distance from the right end face of the 2μm laser crystal 2-4 to the left end face of the high-reflection plano-concave end mirror 2-5;

[0089] S42: Since the introduced high-reflection plano-concave end mirror 2-5 is a plano-concave mirror, this will introduce further deviation of the light beam. The propagation direction of the reflected light beam is affected by the position and angle of the 2μm laser crystal 2-4. Therefore, the deviation Δd of the corrected spot position on the aperture A3-3 is calculated according to formula (2): total ;

[0090] Δd total =ΔD 曲率 +Δd 平面 (2);

[0091] In the formula, Δd 曲率 is the offset of the arc propagation of the light beam caused by the curvature of the concave surface of the high-reflection plano-concave end mirror 2-5, Among them, R c is the curvature radius of the concave surface of the high-reflection plano-concave end mirror 2-5; D2 is the horizontal distance from the aperture A3-3 to the left end surface of the high-reflection plano-concave end mirror 2-5;

[0092] S43: transform formula (2) to obtain formula (3);

[0093]

[0094] S44: transform formula (3) to obtain formula (4);

[0095]

[0096] In order to ensure the stability of the reflected light spot and the accuracy of the measurement, in step 1, the collimation error of the light beam emitted by the helium-neon laser 3-1 is less than 0.5 mrad.

[0097] The present invention proposes a crystal angle measurement and calibration technology based on the change of red light reflection position, which uses the principle of geometric optics combined with automatic calculation and feedback control to achieve real-time adjustment of the crystal angle and rapid recovery of the laser optical path. Specifically, it relates to a 2-micron laser control technology, which amplifies the crystal deflection angle through the law of reflection, calculates the tiny angle change of the crystal through the displacement at the aperture, and realizes the integration of angle calculation and optical path control. In the process of adjusting the angle of the 2μm laser crystal, an automatic adjustment method is adopted. The adjustment process collects image data in real time through a visible light camera and sends it to the control terminal. The control terminal determines the spot position according to the image data and calculates the deflection angle; when the laser cavity successfully emits light for the first time, the spot position of the red light on the aperture A is first recorded as a calibration reference point. When the laser fails later, the deviation comparison between the spot position and the preset reference position is performed to realize closed-loop control of the crystal angle, thereby realizing automatic adjustment of the crystal position and angle, which can minimize manual intervention and restore the normal light emission of the laser by automatically adjusting the crystal angle and position.

Claims

1. A crystal angle measurement and adjustment device for off-axis pumped folded lasers, comprising an automatic control subsystem (1) and a laser cavity system (2), characterized in that: Also included is a laser calibration subsystem (3); The automatic control subsystem (1) comprises a control terminal (1-1), a visible light camera (1-2), a precision displacement platform (1-3) and an electric-controlled displacement platform (1-4); The laser cavity system (2) comprises a micron pump source (2-1), a collimating and focusing lens group (2-2), an incident plano-concave end mirror (2-3), a 2μm laser crystal (2-4), a high-reflection plano-concave end mirror (2-5), an output coupling mirror OC (2-6), an aperture B (2-7) and a 2μm total reflection mirror (2-8); The laser calibration subsystem (3) comprises a helium-neon laser (3-1), a red light total reflector (3-2) and an aperture A (3-3); The end face of the 2 μm laser crystal (2-4) is highly transparent to the pump light and highly reflective to the measuring light, and the end face is used to reflect the measuring light beam; the 2 μm laser crystal (2-4) is mounted on a precision displacement platform, and the precision displacement platform (1-3) is used to drive the angle of the 2 μm laser crystal (2-4) to change; the precision displacement platforms (1-3) are all mounted on a bearing platform of an electrically controlled displacement platform (1-4), and the electrically controlled displacement platform (1-4) is used to adjust the position of the bearing platform; The collimating and focusing lens group (2-2), the incident plano-concave end mirror (2-3), the 2μm laser crystal (2-4), the high-reflection plano-concave end mirror (2-5) and the red light total reflection mirror (3-2) are sequentially spaced from left to right in the transverse direction; the collimating and focusing lens group (2-2) is used to ensure that the pump light beam has high parallelism when incident on the end face of the 2μm laser crystal (2-4); the concave surfaces of the incident plano-concave end mirror (2-3) and the high-reflection plano-concave end mirror (2-5) are both located on a side close to the 2μm laser crystal (2-4), and the intersection of the axis of the incident plano-concave end mirror (2-3) and the axis of the high-reflection plano-concave end mirror (2-5) is located on the rear side of the axis of the collimating and focusing lens group (2-2); The output coupling mirror OC (2-6) is arranged at the left part of the rear side of the 2μm laser crystal (2-4) and is distributed opposite to the high-reflection plano-concave end mirror (2-5); the output coupling mirror OC (2-6) is used to adjust its reflectivity or transmittance to balance the light intensity of the output energy beam and the output light intensity of the 2μm folded laser cavity, so as to control the output power and beam quality of the laser; the aperture A (3-3) is a barrier with scale marks, which is arranged on the optical path between the output coupling mirror OC (2-6) and the high-reflection plano-concave end mirror (2-5) and is used to receive the light spot of the measurement beam reflected by the high-reflection plano-concave end mirror (2-5); the 2μm total reflection mirror (2-8) is arranged at the right part of the rear side of the 2μm laser crystal (2-4) and is distributed opposite to the incident plano-concave end mirror (2-3); the aperture B (2-7 ) is a barrier without scale marks, which is arranged on the optical path between the incident plano-concave end mirror (2-3) and the 2μm total reflection mirror (2-8), and is used to fix the optical path when the helium-neon laser (3-1) emits a measuring light beam and the 2μm laser crystal (2-4) is removed, so as to ensure that the positions of the incident plano-concave end mirror (2-3) and the high-reflection plano-concave end mirror (2-5) are fixed; the direction of the exit optical path of the red light total reflection mirror (3-2) coincides with the axis of the collimating and focusing lens group (2-2), and is used to reflect the measuring light beam to the high-reflection plano-concave end mirror (2-5); the incident plano-concave end mirror (2-3), the 2μm laser crystal (2-4), the high-reflection plano-concave end mirror (2-5), the output coupling mirror OC (2-6) and the high-reflectivity end mirror HR (2-8) cooperate with each other to form a 2μm folded laser cavity; The micron pump source (2-1) is arranged on the left side of the collimating and focusing lens group (2-2), and the direction of its outgoing light path coincides with the axis of the collimating and focusing lens group (2-2), and is used to emit a pump light beam; The helium-neon laser (3-1) is arranged on the incident light path of the red light total reflection mirror (3-2) and is used to emit a detection light beam to the incident light path of the red light total reflection mirror (3-2); The visible light camera (1-2) is arranged on one side of the aperture A (3-3), and its collection window faces the aperture A (3-3), and is used to collect an image of the light spot position on the aperture A (3-3) in real time and send it to the control terminal (1-1); The control terminal (1-1) is respectively connected to a visible light camera (1-2), a precision displacement platform (1-3) and an electrically controlled displacement platform (1-4), and is used to calculate the deviation between the light spot position and a preset reference position according to an image collected by the visible light camera (1-2), calculate the relationship between the light spot position and the angle of a 2μm laser crystal (2-4) according to the image collected by the visible light camera (1-2), and perform real-time calculation of the deflection angle of the 2μm laser crystal (2-4), and at the same time, is used to feedback control the precision displacement platform (1-3) and the electrically controlled displacement platform (1-4) according to the deviation, so as to automatically adjust the angle and position of the 2μm laser crystal (2-4) to a target posture.

2. A crystal angle measurement and adjustment device for off-axis pumped folded laser according to claim 1 or 2, characterized in that: The control terminal (1-1) is a computer.

3. The crystal angle measuring and adjusting device for off-axis pumped folded laser according to claim 2, characterized in that: The control terminal (1-1) is connected to a visible light camera (1-2), a precision displacement platform (1-3) and an electric-controlled displacement stage (1-4) via a python platform.

4. The crystal angle measuring and adjusting device for off-axis pumped folded laser according to claim 3, characterized in that: It also includes a photoelectric detector connected to the control terminal (1-1), which is arranged at the output side of the output coupling mirror OC (2-6) and is used to detect the power and stability of the output laser in real time.

5. The crystal angle measuring and adjusting device for off-axis pumped folded laser according to claim 4, characterized in that: The precision displacement platform (1-3) is a high-precision angle adjustment mechanism driven by a stepping motor or piezoelectric ceramics.

6. The crystal angle measuring and adjusting device for off-axis pumped folded laser according to claim 4, characterized in that: The 2 μm laser crystal (2-4) is a holmium-doped or thulium-doped crystal, and the pump wavelength is two microns.

7. The crystal angle measuring and adjusting device for off-axis pumped folded laser according to claim 1, characterized in that: The aperture A (3-3) and the aperture B (2-7) are both made of high temperature resistant metal or wear-resistant alloy material.

8. A method for measuring and adjusting the crystal angle of an off-axis pumped folded laser, using a device for measuring and adjusting the crystal angle of an off-axis pumped folded laser as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Start the helium-neon laser (3-1), and use the helium-neon laser (3-1) to output a red laser beam to the incident light path of the red light total reflection mirror (3-2), and use it as a measurement beam; Step 2: using the red light total reflection mirror (3-2) to reflect the measuring light beam to the high reflection plano-concave end mirror (2-5), and at the same time, using the transmission effect of the high reflection plano-concave end mirror (2-5) to make the measuring light beam incident on the right end face of the 2μm laser crystal (2-4), then using the reflection effect of the right end face of the 2μm laser crystal (2-4) to reflect the measuring light beam to the high reflection plano-concave end mirror (2-5), and then using the reflection effect of the high reflection plano-concave end mirror (2-5) to reflect the measuring light beam to the aperture A (3-3), and using the aperture A (3-3) to receive the light spot in the measuring light beam; Step 3: Start and adjust the micron pump source (2-1) to emit pump light to the axial position of the collimating and focusing lens group (2-2); use the collimating and focusing lens group (2-2) to adjust the direction and shape of the pump light beam to a parallel light beam, then make the parallel pump light beam incident on the incident plano-concave end mirror (2-3), use the transmission effect of the incident plano-concave end mirror (2-3) to make the pump light beam incident on the 2μm laser crystal (2-4), then pass through the 2μm laser crystal (2-4) to make it incident on the high-reflection plano-concave end mirror (2-5), then reflect from the high-reflection plano-concave end mirror (2-5) through the aperture A (3-3) and make it incident on the output coupling mirror OC (2-6), so as to balance the light intensity of the output light beam and the output light intensity through the output coupling mirror OC (2-6), thereby controlling the output power and beam quality of the laser; Step 4: Adjust the deflection angle of the 2 μm laser crystal (2-4), use the visible light camera (1-2) to collect an image of the spot position on the aperture A (3-3) in real time, and send it to the control terminal (1-1), and the control terminal (1-1) calculates and outputs the deflection angle α of the 2 μm laser crystal (2-4) in real time based on the image collected by the visible light camera (1-2); When the 2μm folded laser cavity successfully outputs a light beam for the first time, the control terminal (1-1) calculates and records the current light spot position according to the image collected by the visible light camera (1-2), and uses the current light spot position as a preset reference position; When the 2μm folded laser cavity cannot output a light beam normally, the control terminal (1-1) calculates the deviation between the current light spot position and the preset reference position according to the image collected by the visible light camera (1-2), and feedback controls the precision displacement platform (1-3) and the electric control displacement platform (1-4) according to the deviation to automatically adjust the deflection angle and position of the 2μm laser crystal (2-4) until the current light spot position is consistent with the preset reference position, so that the 2μm folded laser cavity is restored to a normal output state; Step 5: When the output operation of the 2μm folded laser cavity is completed, first adjust the deflection angle and position of the 2μm laser crystal (2-4) to ensure that the current spot position on the aperture A (3-3) is consistent with the preset reference position, then fix the deflection angle and position of the 2μm laser crystal (2-4), and then turn off the micron pump source (2-1).

9. The method for measuring and adjusting the crystal angle for off-axis pumped folded laser according to claim 8, characterized in that: In step 4, the calculation process of the deflection angle α is as follows: S41: Based on the reflection principle, according to formula (1), when the 2μm laser crystal (2-4) is slightly deflected, after being reflected by the high-reflection plano-concave end mirror (2-5), the offset Δd of the light spot position on the aperture A (3-3) is calculated: 平面 ; Δd 平面 =2D1·tan(2α) (1); Where D1 is the horizontal distance from the right end face of the 2μm laser crystal (2-4) to the left end face of the high-reflection plano-concave end mirror (2-5); S42: Calculate the offset Δd of the corrected spot position on aperture A (3-3) according to formula (2): total ; Δd total =Δd 曲率 +Δd 平面 (2); In the formula, Δd 曲率 is the deviation of the arc propagation of the light beam caused by the curvature of the concave surface of the high-reflection plano-concave end mirror (2-5), Among them, R c is the curvature radius of the concave surface of the high-reflection plano-concave end mirror (2-5); D2 is the horizontal distance from the aperture A (3-3) to the left end surface of the high-reflection plano-concave end mirror (2-5); S43: transform formula (2) to obtain formula (3); S44: transform formula (3) to obtain formula (4); 10. The method for measuring and adjusting the crystal angle for off-axis pumped folded laser according to claim 9, characterized in that: In step one, the collimation error of the light beam emitted by the helium-neon laser (3-1) is less than 0.5 mrad.

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