Concave surface total reflection position optimization method for bicrystal regeneration amplification structure

Abstract

The invention discloses a concave surface total reflection position optimization method for a bicrystal regeneration amplification structure. The to-be-optimized bicrystal regeneration amplification structure comprises an optical resonant cavity, two gain crystals arranged in series, two concave total reflective mirrors and a Pockels cell. The method comprises the following steps: determining the positions of two gain crystals in a bicrystal regeneration amplification structure in an optical resonant cavity, and setting the initial positions of two concave total reflective mirrors according to the physical cavity length of the optical resonant cavity; establishing a thermal lens effect model of the gain crystal, obtaining thermal lens focal lengths of the gain crystal under different pumping powers, and carrying out substitution optimization on initial positions of the two concave total reflective mirrors; and verifying the optimized position of the concave total reflective mirror, detecting the stability of the optical resonant cavity and the beam quality of the output laser in a set pumping power range, and if the stability and the beam quality meet preset requirements, determining the optimized position of the concave total reflective mirror as a final position.

Description

Technical Field

[0001] This application relates to the field of ultrafast laser technology, and in particular to a method for optimizing the concave total reflection position of a dual-crystal regenerative amplification structure. Background Technology

[0002] In the field of ultrafast laser technology, regenerative amplification systems are widely used in industrial precision machining, medical surgery, and other scenarios due to their ability to achieve exponential increases in pulse energy. Traditional single-crystal regenerative amplification technology is limited by the energy storage limit and thermal management capabilities of a single gain crystal. Under high-power pumping, it is prone to resonant cavity instability and beam quality degradation due to thermal lensing effects, and the output energy is usually limited to the millijoule level and below. It is also difficult to achieve both high average power and stable beam quality. Although traveling-wave amplification schemes can increase energy through multi-stage amplification, the complex mode matching requirements of the system introduce additional losses and alignment difficulties, and still cannot meet the application requirements of high energy and high stability.

[0003] In existing technologies, improvements to the thermal stability of regenerative amplification systems mainly focus on the thermal design of single crystals (such as temperature control and crystal cutting processes). While dual-crystal distributed gain architectures can distribute the heat load, there is still no mature solution for dynamically compensating for beam distortion caused by the thermal lensing effect of dual crystals under different pump powers. Especially in dual-crystal series layouts, the beam needs to pass through the gain medium twice, and the accumulation of the thermal lensing effect will significantly change the optical parameters of the resonant cavity. Traditional fixed cavity mirror designs cannot adaptively compensate for this dynamic change, leading to a decrease in energy extraction efficiency or an increased risk of crystal damage.

[0004] Therefore, a method is urgently needed to solve at least one of the above problems. Summary of the Invention

[0005] This application provides a method for optimizing the concave total reflection position in a dual-crystal regenerative amplification structure. The aim is to address the shortcomings of existing technologies where improvements to the thermal stability of regenerative amplification systems primarily focus on the thermal design of single crystals (such as temperature control and crystal cutting processes). While dual-crystal distributed gain architectures can distribute heat load, there is still no mature solution for dynamically compensating for beam distortion caused by the thermal lensing effect of the dual crystals under different pump powers. Especially in a dual-crystal tandem layout, the beam needs to pass through the gain medium twice, and the cumulative thermal lensing effect significantly alters the optical parameters of the resonant cavity. Traditional fixed-mirror designs cannot adaptively compensate for this dynamic change, leading to problems such as decreased energy extraction efficiency or increased crystal damage risk.

[0006] This application provides a method for optimizing the concave total reflection position of a dual-crystal regenerative amplification structure. The dual-crystal regenerative amplification structure to be optimized includes an optical resonant cavity, two gain crystals placed in series, two concave total reflection mirrors, and a Pockels cell. The method includes: The positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure are determined. The initial positions of the two concave total reflection mirrors are set according to the physical cavity length of the optical resonant cavity. The ray tracing algorithm is used to calculate the spot size of the seed light in the two gain crystals after entering the optical resonant cavity through the input coupling system without thermal lensing effect. It is determined whether the spot size is in the optimal state. If not, the positions of the two concave total reflection mirrors are adjusted until the spot size of the seed light in the two gain crystals is in the optimal state. A thermal lensing effect model of the gain crystal is established to obtain the thermal lens focal length of the gain crystal under different pump powers. Based on the thermal lens focal length, the beam wavefront changes caused by the thermal lensing effect of the two gain crystals under different pump powers are calculated. Based on the goal of compensating for beam distortion caused by the thermal lensing effect, a relationship model between the position parameters of the two concave total reflection mirrors and the beam wavefront changes is established. The initial positions of the two concave total reflection mirrors are optimized based on the relationship model. The optimized position of the concave total reflection mirror is verified. Within the set pump power range, the stability of the optical resonator and the beam quality of the output laser are detected. If the stability and beam quality meet the preset requirements, the optimized position of the concave total reflection mirror is determined as the final position.

[0007] In some embodiments, determining the positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure includes: placing the two gain crystals in series along the optical path transmission direction, so that the seed light passes through the two crystals in sequence; calculating and determining the spacing between the two crystals in the cavity based on the actual length of the gain crystals, the focusing position of the pump light, and the specific mode matching requirements of the optical resonant cavity, to ensure that the transmission direction of the seed light in the two crystals is consistent, and that the center of the seed light spot completely coincides with the focus of the pump light.

[0008] In some embodiments, setting the initial position of the two concave total reflection mirrors according to the physical cavity length of the optical resonant cavity includes: setting the physical cavity length of the optical resonant cavity to 2.2 meters to meet the response time requirements of the intracavity Pockels cell electro-optic switch; based on the physical cavity length, symmetrically arranging the two concave total reflection mirrors on both sides of the two gain crystals, such that the optical path between the two concave total reflection mirrors is exactly equal to the physical cavity length, and the curvature center of the concave total reflection mirror is aligned with the center of the corresponding gain crystal on the optical axis.

[0009] In some embodiments, the step of using a ray tracing algorithm to calculate the spot size of the seed light after it enters the optical resonant cavity through the input coupling system in the absence of thermal lensing, and determining whether the spot size is in the optimal state, includes: simulating the transmission path of the seed light in the optical resonant cavity using a geometric ray tracing algorithm or a Gaussian beam propagation algorithm; calculating the spot radius and energy distribution of the seed light in the two gain crystals; comparing the calculated spot size with the mode field radius of the gain crystals; if the spot radius exceeds a preset ratio range of the mode field radius, determining that the spot size is not in the optimal state, and adjusting the lateral position or angle of the two concave total reflection mirrors until the spot size and the mode field radius reach a matching state.

[0010] In some embodiments, establishing a thermal lensing effect model of the gain crystal and obtaining the thermal lens focal length of the gain crystal under different pump powers includes: based on the thermal properties of the gain crystal and the pump power distribution; the thermal properties include thermal conductivity, coefficient of thermal expansion, and temperature coefficient of refractive index; using finite element analysis or analytical formulas to calculate the temperature field distribution inside the gain crystal under different pump powers; and obtaining the functional relationship between the thermal lens focal length and the pump power based on the refractive index gradient change caused by the temperature field distribution, so as to obtain the thermal lens focal length corresponding to different pump powers.

[0011] In some embodiments, calculating the beam wavefront change caused by the thermal lensing effect of the two gain crystals under different pump powers based on the thermal lens focal length includes: equating the thermal lensing effect of each gain crystal to a thin lens, with the corresponding focal length being the thermal lens focal length; simulating the beam transmission process after passing through the two equivalent thin lenses using the ABCD matrix method, and calculating the change in the beam wavefront curvature radius; and determining the degree of distortion and phase distribution change of the beam wavefront within the gain crystal based on the change in the wavefront curvature radius.

[0012] In some embodiments, establishing a relationship model between the position parameters of the two concave total reflection mirrors and the wavefront variation of the beam, with the goal of compensating for beam distortion caused by thermal lensing, includes: setting the position parameters of the concave total reflection mirrors as variables, with the wavefront distortion of the beam after passing through the optical resonant cavity as the objective function; the position parameters include lateral position, longitudinal spacing, and tilt angle; using matrix optics theory, establishing a mathematical mapping relationship between the position parameters of the concave total reflection mirrors and the wavefront curvature radius and wavefront aberration of the beam, forming a relationship model, which is used to describe the compensation effect of position parameter adjustment on beam distortion caused by thermal lensing.

[0013] In some embodiments, the iterative optimization of the initial positions of the two concave total reflection mirrors according to the relational model includes: solving the relational model using an optimization algorithm to minimize the beam wavefront distortion as the optimization objective; adjusting the position parameters of the two concave total reflection mirrors in each iteration and calculating the adjusted beam wavefront distortion value; terminating the iteration process when the beam wavefront distortion value is less than a preset threshold or the number of iterations reaches a preset upper limit, and determining the optimized concave total reflection mirror position parameters.

[0014] In some embodiments, verifying the optimized concave total reflection mirror position by detecting the stability of the optical resonator and the beam quality of the output laser within a set pump power range includes: sequentially changing the pump power within the set pump power range and running a dual-crystal regenerative amplification system; measuring the beam wavefront aberration of the output laser using a laser interferometer and calculating the beam quality factor value; evaluating the stability of the cavity by monitoring the power loss and output laser energy fluctuation amplitude within the optical resonator; and determining that the optimized concave total reflection mirror position is qualified if the beam quality factor value is less than a preset threshold under all test pump powers and the stability index of the optical resonator meets the preset requirements.

[0015] In some embodiments, the method further includes: training a neural network model using historical pump power-thermal lens focal length-concave mirror position adjustment data, with the input being the real-time pump power value and the output being the predicted concave mirror position compensation amount; and updating the model parameters of the neural network model based on real-time monitored beam wavefront distortion data through an online learning mechanism to achieve dynamic prediction and compensation of the thermal lensing effect.

[0016] This application establishes a relationship model between the thermal lensing effect model and the position parameters of the concave mirror to achieve adaptive compensation for beam distortion caused by thermal lensing in a dual-crystal system, thus solving the problem of resonant cavity instability caused by thermal lensing effect in traditional single-crystal systems at high power. Based on ray tracing algorithms, the beam spot matching in the athermal state is optimized, and the thermal lensing effect is dynamically compensated through iterative optimization to ensure that the seed light is always in the optimal mode field distribution within the dual crystal, significantly improving the single-pulse energy extraction efficiency and breaking through the millijoule energy limit. Stability verification within the pump power range shows that the system can maintain a beam quality factor M at pump powers of 0-100W. 2 The value is lower than the preset threshold, and the energy fluctuation amplitude meets the requirements of industrial applications. It is suitable for applications such as precision machining and strong field physics research that require high-energy and high-stability lasers.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart illustrating the steps of a concave total reflection position optimization method for a dual-crystal regenerative amplification structure provided in an embodiment of this application; Figure 2 This is a schematic block diagram of the structure of a computer device provided in an embodiment of this application.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0023] It should be understood that, in order to clearly describe the technical solutions of the embodiments of the present invention, the terms "first" and "second" are used in the embodiments of the present invention to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0024] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0025] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0026] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0027] In the field of ultrafast laser technology, regenerative amplification systems are widely used in industrial precision machining, medical surgery, and other scenarios due to their ability to achieve exponential increases in pulse energy. Traditional single-crystal regenerative amplification technology is limited by the energy storage limit and thermal management capabilities of a single gain crystal. Under high-power pumping, it is prone to resonant cavity instability and beam quality degradation due to thermal lensing effects, and the output energy is usually limited to the millijoule level and below. It is also difficult to achieve both high average power and stable beam quality. Although traveling-wave amplification schemes can increase energy through multi-stage amplification, the complex mode matching requirements of the system introduce additional losses and alignment difficulties, and still cannot meet the application requirements of high energy and high stability.

[0028] In existing technologies, improvements to the thermal stability of regenerative amplification systems mainly focus on the thermal design of single crystals (such as temperature control and crystal cutting processes). While dual-crystal distributed gain architectures can distribute the heat load, there is still no mature solution for dynamically compensating for beam distortion caused by the thermal lensing effect of dual crystals under different pump powers. Especially in dual-crystal series layouts, the beam needs to pass through the gain medium twice, and the accumulation of the thermal lensing effect will significantly change the optical parameters of the resonant cavity. Traditional fixed cavity mirror designs cannot adaptively compensate for this dynamic change, leading to a decrease in energy extraction efficiency or an increased risk of crystal damage.

[0029] Therefore, a method is urgently needed to solve at least one of the above problems.

[0030] To solve the above problem, please refer to Figure 1 , Figure 1 This is a schematic flowchart illustrating a method for optimizing the concave total reflection position of a dual-crystal regenerative amplification structure according to an embodiment of this application. The dual-crystal regenerative amplification structure to be optimized includes an optical resonant cavity, two gain crystals placed in series, two concave total reflection mirrors, and a Pockels cell. The method is executed by a computer device.

[0031] like Figure 1 As shown, the provided method includes steps S101 to S103. The computer device can be a handheld terminal, a laptop computer, a wearable device, or a robot, etc. This is used to implement steps S101 to S103 and their corresponding embodiments.

[0032] Step S101. Determine the positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure. Set the initial positions of the two concave total reflection mirrors according to the physical cavity length of the optical resonant cavity. Calculate the spot size of the seed light in the two gain crystals after entering the optical resonant cavity through the input coupling system without thermal lensing effect using a ray tracing algorithm. Determine whether the spot size is in the optimal state. If not, adjust the positions of the two concave total reflection mirrors until the spot size of the seed light in the two gain crystals is in the optimal state.

[0033] Specifically, this step aims to construct the reference optical cavity shape for the dual-crystal regenerative amplification system. By precisely controlling the spatial positions of the two concave total reflection mirrors, the spot size of the seed light within the two gain crystals is made to reach the theoretically optimal value. This optimization process ignores the thermal lensing effect and only considers the geometric optical propagation characteristics to ensure that the system has the best mode-matching conditions in the cold cavity state.

[0034] The position of the gain crystal depends on the pump light coupling method (such as end-face pumping or side pumping) and the crystal cooling structure. Two gain crystals (usually Nd:YAG, Ti:Sapphire, etc.) are connected in series along the optical axis in the central region of the resonant cavity, with a fixed spacing of d (generally 10-30 mm) to ensure that the pump spot and the seed spot are highly overlapped in the crystal.

[0035] The initial position of the total reflection mirror is set based on the total physical cavity length L of the resonant cavity (usually 0.5-2 m). Two concave total reflection mirrors (radii of curvature R1, R2) are symmetrically arranged on both sides of the crystal. The initial position satisfies the near-confocal or near-concentric condition, so that the eigenmode of the resonant cavity has a small waist radius at the crystal.

[0036] The propagation path of the seed light after entering the resonant cavity via the input coupler (usually a combination of thin-film polarizers or waveplates) is simulated using the ABCD matrix method or finite element ray tracing simulation (such as Zemax or Code V). The 1 / e of the beam path within the two crystals is then calculated. 2 The spot radii ω1 and ω2 are determined, and their matching degree M with the pump spot is evaluated. 2 .

[0037] The optimal spot size must satisfy the following conditions: the spot radius should be approximately 0.7-0.9 times the pump spot radius to achieve maximum gain extraction efficiency; the difference in spot size between the two crystals should be less than 10% to ensure gain balance. If these conditions are not met, the position of the concave total reflection mirror should be finely adjusted along the optical axis (step size 0.1-0.5 mm), and the calculation should be recalculated until the objective function F = |ω1- ω2| + α*|ω1- ωp| (where ωp is the pump spot radius and α is the weighting coefficient) is minimized.

[0038] Step S102. Establish a thermal lensing effect model for the gain crystal and obtain the thermal lens focal length of the gain crystal under different pump powers. Based on the thermal lens focal length, calculate the beam wavefront changes caused by the thermal lensing effect of the two gain crystals under different pump powers. Based on the goal of compensating for beam distortion caused by the thermal lensing effect, establish a relationship model between the position parameters of the two concave total reflection mirrors and the beam wavefront changes. Optimize the initial positions of the two concave total reflection mirrors based on the relationship model.

[0039] Specifically, the core of this step lies in quantifying the thermal lensing effect induced by pump power and establishing an explicit relationship between the position of the concave total reflection mirror and the wavefront distortion of the beam, achieving dynamic compensation through a numerical optimization algorithm. This model equates the thermal lens to a thin lens with a variable focal length, adjusting the position of the concave mirror in real time to counteract wavefront distortion and maintain the stability of the resonant cavity.

[0040] The thermal lensing effect model is established by using finite element thermal analysis (such as COMSOL) to solve for the internal temperature field distribution ΔT(r,z) of the crystal. Combined with the thermo-optical coefficient dn / dT and stress birefringence, the focal length fth of the thermal lens is calculated. ; Where K e Let fth be the thermal conductivity, η be the thermal conversion coefficient, Pabs be the absorbed pump power, α be the absorption coefficient, and l be the crystal length. Discrete fth data at different pump powers (10-100 W) are obtained through experimental calibration (e.g., probe beam method), and the fth(P) interpolation function is established.

[0041] The wavefront distortion of the beam is calculated by equating the thermal lens to a thin lens with a focal length of fth, and using Collins' formula to calculate the wavefront curvature variation of the Gaussian beam: ΔR = (fth * R0) / (fth - R0), where R0 is the radius of curvature of the incident beam wavefront. For a dual-crystal system, the total wavefront distortion is the cumulative effect of passing through the crystal twice: ΔRtotal = ΔR1 + ΔR2.

[0042] The position parameter-wavefront relationship model establishes the relationship between the displacement (Δx1, Δx2) of the concave total reflection mirror and the compensated wavefront curvature Reee: ; Where A, B, and C are the optical transfer matrix coefficients, obtained through ray tracing simulation fitting. The optimization objective is to minimize the residual wavefront distortion: min|Reee-R0|.

[0043] The iterative optimization algorithm employs gradient descent or a genetic algorithm, using the position of the concave mirror as the variable and the stability parameters g1*g2 of the resonant cavity (g being the mirror's g-parameter) within the range of 0-1 as a constraint. Iteratively, it solves for the optimal (Δx1, Δx2). The focal length of the thermal lens is updated in each iteration until the objective function converges (tolerance < 10).-4 ).

[0044] Step S103. Verify the optimized position of the concave total reflection mirror. Within the set pump power range, detect the stability of the optical resonator and the beam quality of the output laser. If the stability and beam quality meet the preset requirements, determine the optimized position of the concave total reflection mirror as the final position.

[0045] Specifically, this step evaluates the actual performance of the optimized concave mirror position under different pump powers through experimental testing and simulation cross-verification, ensuring that the resonant cavity operates stably for a long time and that the output beam quality meets the application requirements.

[0046] Stability testing is performed by monitoring the Q-value of the resonant cavity's intrinsic mode and output power fluctuations within the pump power sweep range (e.g., 20-80 W). A photodetector is used to record pulse sequences, and energy stability is calculated. Simultaneously, a Hartmann wavefront sensor is used to measure the residual wavefront error RMS value (target < λ / 10) after thermal lens compensation in real time.

[0047] Beam quality assessment via M 2 The instrument measures the M of the output beam. 2 Factors are used to verify whether they are close to the diffraction limit (e.g., M). 2 <1.3). The far-field spot distribution is measured using the knife-edge method or a CCD camera to ensure that there is no thermal astigmatism or ellipticization.

[0048] For example, the preset thresholds include: the resonant cavity's stable operating range covering the target pump power range; and the beam quality M. 2 <1.5; Energy extraction efficiency >40% (relative to small signal gain). If any metric fails to meet the standard, return to step S102 to adjust the weight coefficient α or optimize the algorithm parameters, and iterate again.

[0049] The optimized concave total reflection mirror position coordinates (x1, x2) are encoded as motor drive parameters and integrated into the closed-loop control system. Real-time fine-tuning (response frequency > 10 Hz) is achieved using piezoelectric ceramics or stepper motors to cope with transient fluctuations in pump power.

[0050] This method transforms the thermal lensing effect of bicrystalline materials into quantifiable optical parameters through a closed-loop process of "cold cavity pre-optimization - thermal effect modeling - dynamic compensation - experimental verification". It also achieves real-time compensation by actively adjusting the position of the concave mirror, ultimately breaking through the energy and power bottleneck of traditional single-crystal systems.

[0051] In some embodiments, determining the positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure includes: placing the two gain crystals in series along the optical path transmission direction, so that the seed light passes through the two crystals in sequence; calculating and determining the spacing between the two crystals in the cavity based on the actual length of the gain crystals, the focusing position of the pump light, and the specific mode matching requirements of the optical resonant cavity, to ensure that the transmission direction of the seed light in the two crystals is consistent, and that the center of the seed light spot completely coincides with the focus of the pump light.

[0052] This embodiment solves the core problem of crystal spatial positioning in a dual-crystal tandem layout. Through geometric optical constraints and mode matching principles, it ensures that the seed light maintains collinear transmission within the two gain crystals and achieves complete spatial mode overlap with the pump light, laying an optical benchmark for subsequent thermal lens compensation.

[0053] First, place two identical gain crystals (e.g., 5×5×10 mm in size). 3 Nd:YVO4 crystals are placed in series along the optical axis, with the crystal spacing d determined based on the Rayleigh range of the pump light, typically set to 20-40 mm to avoid thermal coupling. A He-Ne aligned laser is used to establish a reference optical path. The crystal attitude is precisely adjusted using a four-dimensional adjustment frame (pitch, yaw, xy translation) to ensure that the propagation direction deviation of the seed light within the two crystals is less than 0.1 mrad. The position of the light spot is monitored on the rear face of the crystal using a CCD camera. Combined with Zemax simulation data of the pump light focusing lens (focal length 50-100 mm), the coordinates of the pump light focus are calculated. By fine-tuning the lateral position of the crystals, the overlap error between the center of the seed light spot and the pump focus is made less than 5 μm. Finally, the crystal position is fixed to ensure mode matching efficiency in the cold cavity state.

[0054] In some embodiments, setting the initial position of the two concave total reflection mirrors according to the physical cavity length of the optical resonant cavity includes: setting the physical cavity length of the optical resonant cavity to 2.2 meters to meet the response time requirements of the intracavity Pockels cell electro-optic switch; based on the physical cavity length, symmetrically arranging the two concave total reflection mirrors on both sides of the two gain crystals, such that the optical path between the two concave total reflection mirrors is exactly equal to the physical cavity length, and the curvature center of the concave total reflection mirror is aligned with the center of the corresponding gain crystal on the optical axis.

[0055] This embodiment addresses the timing requirements of the electro-optic switch for a 2.2-meter-long resonant cavity by achieving initial optical path matching through a symmetrical concave mirror layout. This ensures that the switching window of the Pockel cell is synchronized with the photon round-trip time, while also guaranteeing the optical coaxiality between the curvature center of the concave mirror and the center of the gain crystal.

[0056] By precisely setting the total physical cavity length of the optical resonator to 2200 mm, which corresponds to a photon round-trip time of approximately 14.7 ns, matching the 1 / 4 wavelength voltage rise time (<10 ns) of a Pockels cell (such as a BBO crystal), the vertex spacing of two concave total reflection mirrors (radii of curvature R1=R2=500 mm) was measured using a laser tracker. A stepper motor was used to drive the mirror mounts, ensuring the distance between the two mirrors was precisely equal to 2200 mm with an error of ±0.5 mm. An autocollimator was used to adjust the orientation of the concave mirrors, aligning their optical axes with the line connecting the center of the gain crystal, with a coaxial deviation of less than 30 arcsec. A crosshair target was placed at the center of the crystal, and the concentricity of the reflected image from the concave mirrors was observed to verify that the alignment accuracy between the center of curvature and the crystal center was better than 0.1 mm, ensuring that the resonator was in a near-symmetric stable region in the initial state.

[0057] In some embodiments, the step of using a ray tracing algorithm to calculate the spot size of the seed light after it enters the optical resonant cavity through the input coupling system in the absence of thermal lensing, and determining whether the spot size is in the optimal state, includes: simulating the transmission path of the seed light in the optical resonant cavity using a geometric ray tracing algorithm or a Gaussian beam propagation algorithm; calculating the spot radius and energy distribution of the seed light in the two gain crystals; comparing the calculated spot size with the mode field radius of the gain crystals; if the spot radius exceeds a preset ratio range of the mode field radius, determining that the spot size is not in the optimal state, and adjusting the lateral position or angle of the two concave total reflection mirrors until the spot size and the mode field radius reach a matching state.

[0058] This embodiment quantifies the mode field distribution of the seed light in the crystal through numerical simulation, establishes a matching criterion between the spot size and the mode field radius of the gain crystal, and optimizes mode matching by iteratively adjusting the position of the concave mirror, thus avoiding the blindness of manual debugging.

[0059] Code for Gaussian beam ABCD matrix transmission was written using MATLAB. Input parameters included: seed light wavelength 1064 nm, initial beam waist radius 0.5 mm, concave mirror curvature radius 500 mm, and initial focal length of the crystal thermal lens set to ∞ (no thermal effect). Simulations calculated the spot radii ω1 and ω2 of the seed light entering the cavity from the input coupler (thin-film polarizer) within the two crystals. The calculation results were compared with the crystal mode field radius ω0 (determined by the pump spot radius of 0.4 mm and the crystal size), and an optimal criterion was set: 0.7ω0 ≤ ω1,2 ≤ 0.9ω0. If the spot radius exceeded this range, the lateral position (0.05 mm step) or tilt angle (10 μrad step) of the concave total reflection mirror was fine-tuned using piezoelectric ceramics, and the calculation was recalculated until the criterion was met. Finally, the position coordinates of the concave mirror were recorded as the initial optimization point, improving the mode matching efficiency to over 98%.

[0060] In some embodiments, establishing a thermal lensing effect model of the gain crystal and obtaining the thermal lens focal length of the gain crystal under different pump powers includes: based on the thermal properties of the gain crystal and the pump power distribution; the thermal properties include thermal conductivity, coefficient of thermal expansion, and temperature coefficient of refractive index; using finite element analysis or analytical formulas to calculate the temperature field distribution inside the gain crystal under different pump powers; and obtaining the functional relationship between the thermal lens focal length and the pump power based on the refractive index gradient change caused by the temperature field distribution, so as to obtain the thermal lens focal length corresponding to different pump powers.

[0061] This embodiment accurately predicts the focal length of the thermal lens under different pump powers through multiphysics coupling simulation, and correlates the thermal property parameters with the spatial distribution of the pump light to provide real-time focal length data for dynamic compensation, overcoming the coarseness of traditional empirical formulas.

[0062] Establish a 3D thermo-mechanical-optical coupling model of the gain crystal in COMSOL Multiphysics. Input parameters: thermal conductivity K of Nd:YVO4 crystal. e =5.1 W / (m*K), coefficient of thermal expansion α=1.5×10 -6 K -1 The temperature coefficient of refractive index is dn / dT = 3.0 × 10⁻⁶. -6 K -1 The pump light was set to a Gaussian distribution (wavelength 808 nm, spot radius 0.4 mm), and the power was gradually increased from 10 W to 100 W. A steady-state solver was used to calculate the internal temperature field ΔT(r,z) of the crystal, with the highest temperature rise located at the crystal center. The refractive index change Δn(r) = (dn / dT)ΔT + Δnstress was calculated based on the thermal stress distribution, and the optical path difference OPD(r) was obtained by integration. The parabolic coefficient of OPD was fitted, and the focal length fth(P) of the thermal lens was extracted, establishing a discrete data table. Experiments verified the use of the probe beam method (He-Ne light passing laterally through the crystal) to measure the actual focal length.

[0063] In some embodiments, calculating the beam wavefront change caused by the thermal lensing effect of the two gain crystals under different pump powers based on the thermal lens focal length includes: equating the thermal lensing effect of each gain crystal to a thin lens, with the corresponding focal length being the thermal lens focal length; simulating the beam transmission process after passing through the two equivalent thin lenses using the ABCD matrix method, and calculating the change in the beam wavefront curvature radius; and determining the degree of distortion and phase distribution change of the beam wavefront within the gain crystal based on the change in the wavefront curvature radius.

[0064] This embodiment equates the complex thermal lensing effect to a thin lens sequence, and uses matrix optics to quickly calculate the change in beam wavefront curvature, quantify the cumulative distortion of the dual crystals, and provide input variables for the compensation model.

[0065] Each crystal's thermal lens is equivalent to a thin lens with a focal length fth, placed at the geometric center of the crystal. The beam transmission matrix is ​​constructed by inputting the beam parameters q0 = z0 + iπω0. 2 The output q1 is calculated using the matrix M1 = [[1,0],[-1 / fth,1]] of the first crystal. Then, considering the free-space transport matrix M2 = [[1,d],[0,1]] of the crystal spacing d, and using the matrix M3 of the second crystal, q2 is finally obtained. The change in wavefront curvature radius ΔR = |R2-R0|, where R = Re(q). The ΔR values ​​are calculated for different pump powers (20 W, 40 W, 60 W), and the ΔR-P curve is plotted. When P = 60 W, the cumulative wavefront distortion of the dual crystals can reach λ / 4 (@1064 nm), requiring compensation.

[0066] In some embodiments, establishing a relationship model between the position parameters of the two concave total reflection mirrors and the wavefront variation of the beam, with the goal of compensating for beam distortion caused by thermal lensing, includes: setting the position parameters of the concave total reflection mirrors as variables, with the wavefront distortion of the beam after passing through the optical resonant cavity as the objective function; the position parameters include lateral position, longitudinal spacing, and tilt angle; using matrix optics theory, establishing a mathematical mapping relationship between the position parameters of the concave total reflection mirrors and the wavefront curvature radius and wavefront aberration of the beam, forming a relationship model, which is used to describe the compensation effect of position parameter adjustment on beam distortion caused by thermal lensing.

[0067] This embodiment establishes an explicit mathematical relationship between the displacement of the concave mirror and the wavefront curvature after compensation, transforming the mechanical adjustment parameters into optical performance indicators, and providing objective functions and constraints for the optimization algorithm.

[0068] Detailed implementation: Define the position parameter vector of the concave total reflection mirror as p = [x1, y1, θ1, x2, y2, θ2] T Where x and y are lateral displacements, and θ is the tilt angle. Using matrix optics, the wavefront transformation matrix Mmirror(p) = [[1,0],[-2 / (Rcosθ),1]] after the beam emitted from the crystal is reflected by the concave mirror. The total transmission matrix Mtotal = Mmirror(p)*Mthermal, where Mthermal is the thermal lensing effect matrix. The objective function F(p) = |R eee (p) - Rideal| 2 +β*(p - p0) 2, where the second term is Tikhonov regularization to prevent over-adjustment. The Jacobian matrix J is constructed using symbolic operations (Mathematica) to form a linearized relationship model: ΔR = J * Δp.

[0069] In some embodiments, the iterative optimization of the initial positions of the two concave total reflection mirrors according to the relationship model includes: solving the relationship model using an optimization algorithm with minimizing the beam wavefront distortion as the optimization goal; during each iteration, adjusting the position parameters of the two concave total reflection mirrors and calculating the beam wavefront distortion value after adjustment; when the beam wavefront distortion value is less than a preset threshold or the number of iterations reaches a preset upper limit, terminating the iterative process and determining the optimized position parameters of the concave total reflection mirrors.

[0070] In this embodiment, a numerical optimization algorithm is used to automatically search for the optimal positions of the concave mirrors, with the goal of minimizing the wavefront distortion. By iterative calculation, local optima are avoided to achieve precise compensation of the thermal lens effect.

[0071] Initialize the position of the concave mirror p0, set the learning rate η = 0.01, and the convergence threshold ε = 10 -6 . In each iteration k, calculate the objective function F(pk) and the gradient at the current position pk F(pk) = J *ΔR. Update the position: pk+1 = pk - η F(pk). At the same time, check the stability condition of the optical resonator: 0 < g1 * g2 < 1, where g i = 1 - L / (R i + Δx i ). If the stability condition is not satisfied, reduce η and re-iterate. Terminate when |F(pk+1) - F(pk)| < ε or the number of iterations k > 500. Finally, obtain the optimized position popt, and the wavefront distortion is reduced from λ / 4 to below λ / 20.

[0072] In some embodiments, the verification of the optimized position of the concave total reflection mirror includes detecting the stability of the optical resonator and the beam quality of the output laser within a set pump power range, including: sequentially changing the pump power within the set pump power range and operating the double-crystal regenerative amplifier system; measuring the beam wavefront aberration of the output laser using a laser interferometer and calculating the beam quality factor value; evaluating the stability of the cavity by monitoring the power loss in the optical resonator and the fluctuation amplitude of the output laser energy; if the beam quality factor value is less than a preset threshold and the stability index of the optical resonator meets the preset requirements at all tested pump powers, determine that the optimized position of the concave total reflection mirror is qualified.

[0073] This embodiment comprehensively evaluates the robustness of the optimized system through wide-range pump power testing, and ensures the effectiveness of the compensation scheme under actual operating conditions by combining interferometry and energy stability monitoring.

[0074] An experimental platform was built, using a fiber-coupled semiconductor laser (power adjustable from 0-100 W, in 10 W increments) as the pump source. At each power point, a regenerative amplification system was run, and the output pulse energy was monitored using an energy meter (Ophir PE50). Energy stability σ was calculated by recording 1000 pulses. The output beam wavefront was measured using a Fizeau interferometer (wavelength 632.8 nm), and the peak-to-valley value PV and root-mean-square (RMS) aberrations were calculated. Beam quality M² was determined by measuring the beam waist and far-field divergence angle using the double-knife-edge method. Acceptance criteria were set as follows: σ < 1.5%, RMS < λ / 10, M² < 1.5%. 2 The resonant cavity exhibited a voltage rating of <1.3 and showed no loss of lock-up at any of the tested power levels. If a power point did not meet the requirements, the thermal lens data for that point was extracted, and the system was re-optimized using Example 7. Final verification showed that the system performance met the requirements within the 20-80 W range.

[0075] In some embodiments, the method further includes: training a neural network model using historical pump power-thermal lens focal length-concave mirror position adjustment data, with the input being the real-time pump power value and the output being the predicted concave mirror position compensation amount; and updating the model parameters of the neural network model based on real-time monitored beam wavefront distortion data through an online learning mechanism to achieve dynamic prediction and compensation of the thermal lensing effect.

[0076] This embodiment introduces machine learning technology to establish an end-to-end prediction model of pump power, thermal lens, and concave mirror position. Through real-time data feedback, online adaptive compensation is achieved, thereby improving the system's response speed to transient thermal effects.

[0077] By collecting historical data—pump power P (10-100 W, step size 5 W), corresponding thermal lens focal length fth, and optimal concave mirror position adjustment Δp—a dataset of 200 groups, {P, fth, Δp}, was constructed. A three-layer backpropagation neural network was designed: one node in the input layer (P), 20 nodes in the hidden layer (ReLU activation), and six nodes in the output layer (Δp). The Adam optimizer was used for training, with mean squared error (MSE) as the loss function. After training, the model inference time was <1 ms. Deployed on an FPGA controller, it reads pump power sensor data in real time and outputs Δp to drive the piezoelectric ceramic to adjust the concave mirror. Every hour of operation, new wavefront sensor data is collected, and the actual residual distortion is calculated. If the deviation > λ / 15, model fine-tuning (transfer learning) is triggered, and the network weights are updated.

[0078] Embodiments of this application also provide a concave total inversion position optimization device for a dual-crystal regenerative amplification structure. This device is used to execute the aforementioned concave total inversion position optimization method for a dual-crystal regenerative amplification structure. The device can be configured in a server or terminal.

[0079] The server can be a standalone server, a server cluster, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDNs), and big data and artificial intelligence platforms. The terminal can be an electronic device such as a mobile phone, tablet, laptop, desktop computer, user digital assistant, or wearable device.

[0080] The concave total inversion position optimization device for dual-crystal regenerative amplification structures includes: The initial determination unit is used to determine the positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure. The initial positions of the two concave total reflection mirrors are set according to the physical cavity length of the optical resonant cavity. The ray tracing algorithm is used to calculate the spot size of the seed light in the two gain crystals after entering the optical resonant cavity through the input coupling system without thermal lensing effect. It is then determined whether the spot size is in the optimal state. If not, the positions of the two concave total reflection mirrors are adjusted until the spot size of the seed light in the two gain crystals is in the optimal state. The model building unit is used to establish a thermal lensing effect model of the gain crystal and obtain the thermal lens focal length of the gain crystal under different pump powers. Based on the thermal lens focal length, it calculates the beam wavefront changes caused by the thermal lensing effect of the two gain crystals under different pump powers. Based on the goal of compensating for beam distortion caused by the thermal lensing effect, it establishes a relationship model between the position parameters of the two concave total reflection mirrors and the beam wavefront changes, and optimizes the initial positions of the two concave total reflection mirrors based on the relationship model. The position verification unit is used to verify the optimized position of the concave total reflection mirror. Within the set pump power range, it detects the stability of the optical resonator and the beam quality of the output laser. If the stability and beam quality meet the preset requirements, the optimized position of the concave total reflection mirror is determined as the final position.

[0081] In some embodiments, determining the positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure includes: placing the two gain crystals in series along the optical path transmission direction, so that the seed light passes through the two crystals in sequence; calculating and determining the spacing between the two crystals in the cavity based on the actual length of the gain crystals, the focusing position of the pump light, and the specific mode matching requirements of the optical resonant cavity, to ensure that the transmission direction of the seed light in the two crystals is consistent, and that the center of the seed light spot completely coincides with the focus of the pump light.

[0082] In some embodiments, setting the initial position of the two concave total reflection mirrors according to the physical cavity length of the optical resonant cavity includes: setting the physical cavity length of the optical resonant cavity to 2.2 meters to meet the response time requirements of the intracavity Pockels cell electro-optic switch; based on the physical cavity length, symmetrically arranging the two concave total reflection mirrors on both sides of the two gain crystals, such that the optical path between the two concave total reflection mirrors is exactly equal to the physical cavity length, and the curvature center of the concave total reflection mirror is aligned with the center of the corresponding gain crystal on the optical axis.

[0083] In some embodiments, the step of using a ray tracing algorithm to calculate the spot size of the seed light after it enters the optical resonant cavity through the input coupling system in the absence of thermal lensing, and determining whether the spot size is in the optimal state, includes: simulating the transmission path of the seed light in the optical resonant cavity using a geometric ray tracing algorithm or a Gaussian beam propagation algorithm; calculating the spot radius and energy distribution of the seed light in the two gain crystals; comparing the calculated spot size with the mode field radius of the gain crystals; if the spot radius exceeds a preset ratio range of the mode field radius, determining that the spot size is not in the optimal state, and adjusting the lateral position or angle of the two concave total reflection mirrors until the spot size and the mode field radius reach a matching state.

[0084] In some embodiments, establishing a thermal lensing effect model of the gain crystal and obtaining the thermal lens focal length of the gain crystal under different pump powers includes: based on the thermal properties of the gain crystal and the pump power distribution; the thermal properties include thermal conductivity, coefficient of thermal expansion, and temperature coefficient of refractive index; using finite element analysis or analytical formulas to calculate the temperature field distribution inside the gain crystal under different pump powers; and obtaining the functional relationship between the thermal lens focal length and the pump power based on the refractive index gradient change caused by the temperature field distribution, so as to obtain the thermal lens focal length corresponding to different pump powers.

[0085] In some embodiments, calculating the beam wavefront change caused by the thermal lensing effect of the two gain crystals under different pump powers based on the thermal lens focal length includes: equating the thermal lensing effect of each gain crystal to a thin lens, with the corresponding focal length being the thermal lens focal length; simulating the beam transmission process after passing through the two equivalent thin lenses using the ABCD matrix method, and calculating the change in the beam wavefront curvature radius; and determining the degree of distortion and phase distribution change of the beam wavefront within the gain crystal based on the change in the wavefront curvature radius.

[0086] In some embodiments, establishing a relationship model between the position parameters of the two concave total reflection mirrors and the wavefront variation of the beam, with the goal of compensating for beam distortion caused by thermal lensing, includes: setting the position parameters of the concave total reflection mirrors as variables, with the wavefront distortion of the beam after passing through the optical resonant cavity as the objective function; the position parameters include lateral position, longitudinal spacing, and tilt angle; using matrix optics theory, establishing a mathematical mapping relationship between the position parameters of the concave total reflection mirrors and the wavefront curvature radius and wavefront aberration of the beam, forming a relationship model, which is used to describe the compensation effect of position parameter adjustment on beam distortion caused by thermal lensing.

[0087] In some embodiments, the iterative optimization of the initial positions of the two concave total reflection mirrors according to the relational model includes: solving the relational model using an optimization algorithm to minimize the beam wavefront distortion as the optimization objective; adjusting the position parameters of the two concave total reflection mirrors in each iteration and calculating the adjusted beam wavefront distortion value; terminating the iteration process when the beam wavefront distortion value is less than a preset threshold or the number of iterations reaches a preset upper limit, and determining the optimized concave total reflection mirror position parameters.

[0088] In some embodiments, verifying the optimized concave total reflection mirror position by detecting the stability of the optical resonator and the beam quality of the output laser within a set pump power range includes: sequentially changing the pump power within the set pump power range and running a dual-crystal regenerative amplification system; measuring the beam wavefront aberration of the output laser using a laser interferometer and calculating the beam quality factor value; evaluating the stability of the cavity by monitoring the power loss and output laser energy fluctuation amplitude within the optical resonator; and determining that the optimized concave total reflection mirror position is qualified if the beam quality factor value is less than a preset threshold under all test pump powers and the stability index of the optical resonator meets the preset requirements.

[0089] In some embodiments, the method further includes: training a neural network model using historical pump power-thermal lens focal length-concave mirror position adjustment data, with the input being the real-time pump power value and the output being the predicted concave mirror position compensation amount; and updating the model parameters of the neural network model based on real-time monitored beam wavefront distortion data through an online learning mechanism to achieve dynamic prediction and compensation of the thermal lensing effect.

[0090] It should be noted that those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the model training device and each module described above can be referred to the corresponding process in the aforementioned embodiment of the concave total reflection position optimization method for dual-crystal regeneration amplification structure, and will not be repeated here.

[0091] The aforementioned concave total reflection position optimization device for dual-crystal regeneration amplification structures can be implemented as a computer program, which can be used in, for example... Figure 2 It runs on the computer device shown.

[0092] Please see Figure 2 , Figure 2 This is a schematic block diagram of the structure of a computer device provided in an embodiment of this application. The computer device includes a processor, a memory, and a network interface connected via a device bus, wherein the memory may include a storage medium and internal memory.

[0093] The storage medium may store operating devices and computer programs. The computer program includes program instructions that, when executed, cause the processor to perform any embodiment of a concave total inversion position optimization method for a dual-crystal regenerative amplification structure.

[0094] The processor provides computing and control capabilities, supporting the operation of the entire computer device.

[0095] Internal memory provides an environment for the execution of computer programs in non-volatile storage media. When executed by a processor, the computer program enables the processor to perform any method based on the concave total inversion position optimization system for dual-crystal regenerative amplification structures.

[0096] This network interface is used for network communication, such as sending assigned tasks. Those skilled in the art will understand that... Figure 2 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the terminal to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0097] It should be understood that the processor can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among these, a general-purpose processor can be a microprocessor or any conventional processor.

[0098] In one embodiment, the processor is configured to run a computer program stored in memory to perform the following steps: The positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure are determined. The initial positions of the two concave total reflection mirrors are set according to the physical cavity length of the optical resonant cavity. The ray tracing algorithm is used to calculate the spot size of the seed light in the two gain crystals after entering the optical resonant cavity through the input coupling system without thermal lensing effect. It is determined whether the spot size is in the optimal state. If not, the positions of the two concave total reflection mirrors are adjusted until the spot size of the seed light in the two gain crystals is in the optimal state. A thermal lensing effect model of the gain crystal is established to obtain the thermal lens focal length of the gain crystal under different pump powers. Based on the thermal lens focal length, the beam wavefront changes caused by the thermal lensing effect of the two gain crystals under different pump powers are calculated. Based on the goal of compensating for beam distortion caused by the thermal lensing effect, a relationship model between the position parameters of the two concave total reflection mirrors and the beam wavefront changes is established. The initial positions of the two concave total reflection mirrors are optimized based on the relationship model. The optimized position of the concave total reflection mirror is verified. Within the set pump power range, the stability of the optical resonator and the beam quality of the output laser are detected. If the stability and beam quality meet the preset requirements, the optimized position of the concave total reflection mirror is determined as the final position.

[0099] In some embodiments, determining the positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure includes: placing the two gain crystals in series along the optical path transmission direction, so that the seed light passes through the two crystals in sequence; calculating and determining the spacing between the two crystals in the cavity based on the actual length of the gain crystals, the focusing position of the pump light, and the specific mode matching requirements of the optical resonant cavity, to ensure that the transmission direction of the seed light in the two crystals is consistent, and that the center of the seed light spot completely coincides with the focus of the pump light.

[0100] In some embodiments, setting the initial position of the two concave total reflection mirrors according to the physical cavity length of the optical resonant cavity includes: setting the physical cavity length of the optical resonant cavity to 2.2 meters to meet the response time requirements of the intracavity Pockels cell electro-optic switch; based on the physical cavity length, symmetrically arranging the two concave total reflection mirrors on both sides of the two gain crystals, such that the optical path between the two concave total reflection mirrors is exactly equal to the physical cavity length, and the curvature center of the concave total reflection mirror is aligned with the center of the corresponding gain crystal on the optical axis.

[0101] In some embodiments, the step of using a ray tracing algorithm to calculate the spot size of the seed light after it enters the optical resonant cavity through the input coupling system in the absence of thermal lensing, and determining whether the spot size is in the optimal state, includes: simulating the transmission path of the seed light in the optical resonant cavity using a geometric ray tracing algorithm or a Gaussian beam propagation algorithm; calculating the spot radius and energy distribution of the seed light in the two gain crystals; comparing the calculated spot size with the mode field radius of the gain crystals; if the spot radius exceeds a preset ratio range of the mode field radius, determining that the spot size is not in the optimal state, and adjusting the lateral position or angle of the two concave total reflection mirrors until the spot size and the mode field radius reach a matching state.

[0102] In some embodiments, establishing a thermal lensing effect model of the gain crystal and obtaining the thermal lens focal length of the gain crystal under different pump powers includes: based on the thermal properties of the gain crystal and the pump power distribution; the thermal properties include thermal conductivity, coefficient of thermal expansion, and temperature coefficient of refractive index; using finite element analysis or analytical formulas to calculate the temperature field distribution inside the gain crystal under different pump powers; and obtaining the functional relationship between the thermal lens focal length and the pump power based on the refractive index gradient change caused by the temperature field distribution, so as to obtain the thermal lens focal length corresponding to different pump powers.

[0103] In some embodiments, calculating the beam wavefront change caused by the thermal lensing effect of the two gain crystals under different pump powers based on the thermal lens focal length includes: equating the thermal lensing effect of each gain crystal to a thin lens, with the corresponding focal length being the thermal lens focal length; simulating the beam transmission process after passing through the two equivalent thin lenses using the ABCD matrix method, and calculating the change in the beam wavefront curvature radius; and determining the degree of distortion and phase distribution change of the beam wavefront within the gain crystal based on the change in the wavefront curvature radius.

[0104] In some embodiments, establishing a relationship model between the position parameters of the two concave total reflection mirrors and the wavefront variation of the beam, with the goal of compensating for beam distortion caused by thermal lensing, includes: setting the position parameters of the concave total reflection mirrors as variables, with the wavefront distortion of the beam after passing through the optical resonant cavity as the objective function; the position parameters include lateral position, longitudinal spacing, and tilt angle; using matrix optics theory, establishing a mathematical mapping relationship between the position parameters of the concave total reflection mirrors and the wavefront curvature radius and wavefront aberration of the beam, forming a relationship model, which is used to describe the compensation effect of position parameter adjustment on beam distortion caused by thermal lensing.

[0105] In some embodiments, the iterative optimization of the initial positions of the two concave total reflection mirrors according to the relational model includes: solving the relational model using an optimization algorithm to minimize the beam wavefront distortion as the optimization objective; adjusting the position parameters of the two concave total reflection mirrors in each iteration and calculating the adjusted beam wavefront distortion value; terminating the iteration process when the beam wavefront distortion value is less than a preset threshold or the number of iterations reaches a preset upper limit, and determining the optimized concave total reflection mirror position parameters.

[0106] In some embodiments, verifying the optimized concave total reflection mirror position by detecting the stability of the optical resonator and the beam quality of the output laser within a set pump power range includes: sequentially changing the pump power within the set pump power range and running a dual-crystal regenerative amplification system; measuring the beam wavefront aberration of the output laser using a laser interferometer and calculating the beam quality factor value; evaluating the stability of the cavity by monitoring the power loss and output laser energy fluctuation amplitude within the optical resonator; and determining that the optimized concave total reflection mirror position is qualified if the beam quality factor value is less than a preset threshold under all test pump powers and the stability index of the optical resonator meets the preset requirements.

[0107] In some embodiments, the method further includes: training a neural network model using historical pump power-thermal lens focal length-concave mirror position adjustment data, with the input being the real-time pump power value and the output being the predicted concave mirror position compensation amount; and updating the model parameters of the neural network model based on real-time monitored beam wavefront distortion data through an online learning mechanism to achieve dynamic prediction and compensation of the thermal lensing effect.

[0108] It should be noted that those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the processor described above can be referred to the corresponding process in the method embodiments of the above embodiments, and will not be repeated here.

[0109] The embodiments of this application also provide a computer-readable storage medium storing a computer program, the computer program including program instructions, and the processor executing the program instructions to implement the steps of the concave total inversion position optimization method for dual-crystal regenerative amplification structures provided in the above embodiments of this application.

[0110] The computer-readable storage medium may be an internal storage unit of the computer device described in the foregoing embodiments, such as the hard disk or memory of the computer device. The computer-readable storage medium may also be an external storage device of the computer device, such as a plug-in hard disk, SmartMedia Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the computer device.

[0111] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for optimizing the concave total reflection position in a dual-crystal regenerative amplification structure, characterized in that, The dual-crystal regenerative amplification structure to be optimized includes an optical resonant cavity, two gain crystals placed in series, two concave total reflection mirrors, and a Pockels cell; the method includes: The positions of the two gain crystals in the optical resonant cavity of the dual-crystal regenerative amplification structure are determined. The initial positions of the two concave total reflection mirrors are set according to the physical cavity length of the optical resonant cavity. The ray tracing algorithm is used to calculate the spot size of the seed light in the two gain crystals after entering the optical resonant cavity through the input coupling system without thermal lensing effect. It is determined whether the spot size is in the optimal state. If not, the positions of the two concave total reflection mirrors are adjusted until the spot size of the seed light in the two gain crystals is in the optimal state. A thermal lensing effect model of the gain crystal is established to obtain the thermal lens focal length of the gain crystal under different pump powers. Based on the thermal lens focal length, the beam wavefront changes caused by the thermal lensing effect of the two gain crystals under different pump powers are calculated. Based on the goal of compensating for beam distortion caused by the thermal lensing effect, a relationship model between the position parameters of the two concave total reflection mirrors and the beam wavefront changes is established. The initial positions of the two concave total reflection mirrors are optimized based on the relationship model. The optimized position of the concave total reflection mirror is verified. Within the set pump power range, the stability of the optical resonator and the beam quality of the output laser are detected. If the stability and beam quality meet the preset requirements, the optimized position of the concave total reflection mirror is determined as the final position.

2. The method according to claim 1, characterized in that, Determining the positions of the two gain crystals within the optical resonant cavity in the dual-crystal regenerative amplification structure includes: Two gain crystals are placed in series along the optical path transmission direction so that the seed light passes through the two crystals in sequence. Based on the actual length of the gain crystal, the focusing position of the pump light, and the specific requirements for mode matching of the optical resonator, the spacing between the two crystals in the cavity is calculated and determined to ensure that the transmission direction of the seed light in the two crystals is consistent and that the center of the seed light spot completely coincides with the focus of the pump light.

3. The method according to claim 1, characterized in that, The initial positions of the two concave total reflection mirrors are set according to the physical cavity length of the optical resonant cavity, including: The physical cavity length of the optical resonant cavity is set to 2.2 meters to meet the response time requirements of the Pockel cell electro-optic switch within the cavity; Based on the physical cavity length, two concave total reflection mirrors are symmetrically arranged on both sides of two gain crystals, so that the optical path between the two concave total reflection mirrors is exactly equal to the physical cavity length, and the curvature center of the concave total reflection mirror is aligned with the center of the corresponding gain crystal on the optical axis.

4. The method according to claim 1, characterized in that, The step of using a ray tracing algorithm to calculate the spot size of the seed light after it enters the optical resonant cavity through the input coupling system in the absence of thermal lensing, and determining whether the spot size is in the optimal state, includes: The propagation path of the seed light in the optical resonant cavity is simulated using either a geometric ray tracing algorithm or a Gaussian beam propagation algorithm. The spot radius and energy distribution of the seed light within the two gain crystals were calculated. The calculated spot size is compared with the mode field radius of the gain crystal. If the spot radius exceeds the preset ratio range of the mode field radius, it is determined that the spot size is not in the optimal state. The lateral position or angle of the two concave total reflection mirrors is adjusted until the spot size and the mode field radius reach a matching state.

5. The method according to claim 1, characterized in that, The establishment of a thermal lensing effect model for the gain crystal, and the acquisition of the thermal lens focal length of the gain crystal under different pump powers, includes: Based on the thermal properties of the gain crystal and the pump power distribution; the thermal properties include thermal conductivity, coefficient of thermal expansion and temperature coefficient of refractive index; The temperature field distribution inside the gain crystal under different pump powers is calculated using finite element analysis or analytical formulas. Based on the refractive index gradient change caused by the temperature field distribution, the functional relationship between the focal length of the thermal lens and the pump power is obtained, so as to obtain the focal length of the thermal lens corresponding to different pump powers.

6. The method according to claim 5, characterized in that, The calculation of the beam wavefront variation caused by the thermal lensing effect of the two gain crystals under different pump powers, based on the focal length of the thermal lens, includes: The thermal lensing effect of each gain crystal is equivalent to a thin lens, and the corresponding focal length is the focal length of the thermal lens. The ABCD matrix method was used to simulate the transmission process of a light beam after passing through two equivalent thin lenses, and the change in the wavefront curvature radius of the light beam was calculated. The degree of distortion and phase distribution of the beam wavefront within the gain crystal are determined based on the change in the wavefront curvature radius.

7. The method according to claim 6, characterized in that, The model establishing the relationship between the position parameters of the two concave total reflection mirrors and the beam wavefront variation, based on the beam distortion caused by compensating for thermal lensing effect, includes: The position parameters of the concave total reflection mirror are set as variables, with the wavefront distortion of the beam after passing through the optical resonant cavity as the objective function; the position parameters include lateral position, longitudinal spacing and tilt angle. Using matrix optics theory, a mathematical mapping relationship is established between the position parameters of the concave total reflection mirror and the wavefront curvature radius and wavefront aberration of the beam, forming a relational model. This model is used to describe the compensation effect of position parameter adjustment on beam distortion caused by thermal lenses.

8. The method according to claim 7, characterized in that, The iterative optimization of the initial positions of the two concave total reflection mirrors based on the relational model includes: An optimization algorithm is used to solve the relational model, with the goal of minimizing beam wavefront distortion. In each iteration, the position parameters of the two concave total reflection mirrors are adjusted, and the adjusted beam wavefront distortion value is calculated. When the beam wavefront distortion value is less than the preset threshold or the number of iterations reaches the preset upper limit, the iteration process is terminated, and the optimized concave total reflection mirror position parameters are determined.

9. The method according to claim 1, characterized in that, The optimized concave total reflection mirror position is verified, and within a set pump power range, the stability of the optical resonator and the beam quality of the output laser are detected, including: The pump power is changed sequentially within the set pump power range to run the dual-crystal regenerative amplification system; The wavefront aberration of the output laser beam is measured using a laser interferometer, and the beam quality factor value is calculated. The stability of the optical resonant cavity is evaluated by monitoring the power loss and output laser energy fluctuation amplitude within the cavity. If the beam quality factor is less than the preset threshold under all test pump powers, and the stability index of the optical resonator meets the preset requirements, the optimized concave total reflection mirror position is deemed qualified.

10. The method according to claim 1, characterized in that, The method further includes: A neural network model is trained using historical pump power, thermal lens focal length, and concave mirror position adjustment data. The input is the real-time pump power value, and the output is the predicted concave mirror position compensation amount. By using an online learning mechanism, the model parameters of the neural network model are updated based on real-time monitored beam wavefront distortion data, thereby enabling dynamic prediction and compensation of the thermal lensing effect.

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