A multi-stage solid laser amplifier wavefront pre-compensation system and method

Abstract

The application discloses a multi-stage solid laser amplifier wavefront pre-compensation system and method, which comprises a seed laser source, a spatial light modulator, a 4f relay imaging system, a wavefront sensor and N-stage laser amplifier stages; after the signal light beam emitted by the seed laser source is phase-modulated by the spatial light modulator, the signal light beam sequentially passes through the 4f relay imaging system and is incident to the laser amplifier stages for amplification; the wavefront sensor is arranged at the output end of the last-stage laser amplifier stage and is used for measuring the wavefront distortion information of the signal light beam after multi-stage amplification; and the spatial light modulator applies conjugate phase compensation to the signal light beam under a low-power condition according to the wavefront distortion information measured by the wavefront sensor. The 4f relay imaging system is used for mapping the dispersed thermal aberration in the multi-stage amplifier to the same equivalent phase plane, and the multi-stage sequential optimization strategy is combined, so that high-quality wavefront pre-compensation of the output light beam of the multi-stage solid laser amplifier is realized.

Description

Technical Field

[0001] This invention relates to the field of solid-state laser technology, and in particular to a wavefront pre-compensation system and method for a multi-stage solid-state laser amplifier. Background Technology

[0002] High-power lasers have a wide and urgent application demand in fields such as industrial processing, space communication, and cutting-edge scientific research. Fiber lasers and solid-state lasers are currently the two main technical routes for achieving high-power laser output. Fiber lasers, with their excellent thermal management capabilities and good beam quality, have become an important development direction in the field of high-power lasers. However, limited by the extremely small mode field area and long interaction length in fiber waveguides, the power improvement of fiber lasers faces fundamental constraints from nonlinear effects such as stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS). These nonlinear effects not only limit further increases in output power but also severely degrade the linewidth characteristics and beam quality of the laser, making it difficult for fiber lasers to simultaneously achieve excellent time-frequency domain characteristics while pursuing higher power.

[0003] Compared to fiber lasers, solid-state lasers, such as rod-shaped or slab-shaped solid-state laser amplifiers, have a much larger mode field volume than optical fibers. This significantly reduces the light intensity density within the gain medium, effectively suppressing nonlinear effects and providing a feasible way to overcome the power bottleneck of fiber lasers. Multi-stage solid-state laser amplification systems based on the master oscillator power amplifier (MOPA) structure, which amplify low-power seed sources through multi-stage power cascades, have become the mainstream technology for achieving high-power laser output at the hundred-watt and even kilowatt levels, demonstrating irreplaceable advantages in applications requiring high-power, high-beam-quality laser sources. However, the large mode field area advantage of solid-state rod amplifiers is accompanied by high sensitivity to thermal effects. Under high-power pumping conditions, the relatively low surface area to volume ratio of the rod-shaped gain medium leads to a significant temperature gradient, resulting in thermally induced wavefront distortion. This is the main obstacle restricting solid-state amplifiers from further increasing power while maintaining beam quality. Traditional thermal management methods mainly focus on optimizing the spatial parameters of the incident beam, achieving efficient spatial overlap with the pump distribution by adjusting the beam size and divergence angle. However, the effectiveness of these methods is fundamentally limited by geometric constraints and insufficient adaptability under variable heat load conditions.

[0004] Adaptive optics technology, which uses wavefront correction devices such as spatial light modulators (SLMs) or deformable mirrors (DMs) to dynamically correct distorted wavefronts, is an effective means of improving beam quality in solid-state lasers. Among these, SLMs have a much larger number of modulation units than DMs, enabling finer wavefront control with higher spatial resolution and thus exhibiting greater compensation potential. However, existing compensation schemes typically place the correction device at the output of an amplifier chain or within a single amplification stage, facing two significant challenges: First, the aberrations generated by the gain media in multi-stage amplifiers are spatially separated and cumulative, making it difficult to accurately characterize and uniformly compensate for using a single correction plane. Conventional local correction methods cannot effectively handle this non-local cumulative distortion. Second, limited by the optical damage threshold of the correction device, even with water-cooling structures, the power level it can withstand is usually limited to the tens of watts, making it unsuitable for direct application in high-power laser paths. This severely restricts the practical application of adaptive optics technology in high-power solid-state laser systems.

[0005] To address the issue of insufficient power handling capability of the aforementioned correction devices, existing research has proposed wavefront pre-compensation architectures. However, most existing pre-compensation schemes are only applied to single-stage amplification structures, and their improvement in overall output power is very limited due to the limited energy storage and extraction efficiency of the single-stage gain medium. To extend the pre-compensation architecture to multi-stage amplification systems, it is necessary to solve the problem of unified characterization and centralized compensation of spatial separation aberrations generated by each stage of gain medium. Thermally induced aberrations of different amplification stages are physically separated and continuously accumulate and couple during the stage-by-stage transmission. How to completely characterize these non-locally distributed accumulated aberrations on a single equivalent plane and apply effective pre-compensation through iterative algorithms is the core technical challenge in realizing multi-stage pre-compensation. Summary of the Invention

[0006] To address the technical problems in existing wavefront compensation methods for multi-stage solid-state laser amplifiers, such as the dispersed sources of thermally induced aberrations, the difficulty in characterizing cumulative distortion with a single correction plane, and the limited power handling capability of wavefront modulation devices, this invention provides a wavefront pre-compensation system and method for multi-stage solid-state laser amplifiers, which can achieve high-quality wavefront pre-compensation for the output beam of multi-stage solid-state laser amplifiers.

[0007] A multi-stage solid-state laser amplifier wavefront pre-compensation system includes a seed laser source, a spatial light modulator, a 4f relay imaging system, a wavefront sensor, and an N-stage laser amplification stage, where N≥2; A 4f relay imaging system is arranged before the first laser amplification stage, between two adjacent laser amplification stages, and after the Nth amplification stage. The signal beam emitted from the seed laser source is phase-modulated by a spatial light modulator and then sequentially passes through the corresponding 4f relay imaging system to be amplified by each laser amplification stage; the signal beam output from the Nth amplification stage is received by a wavefront sensor after passing through a 4f relay imaging system. The wavefront sensor is used to measure the residual wavefront distortion information of the signal beam after multi-stage amplification; the spatial light modulator, based on the residual wavefront distortion information measured by the wavefront sensor, operates under low power conditions (power density threshold below 200 W / cm²). 2 By applying conjugate phase compensation to the signal beam, wavefront pre-compensation of the output beam is achieved.

[0008] This invention avoids the power handling limitations of wavefront modulators by placing them in low-power seed optical paths, and combines them with a 4f relay imaging system to image the front faces of each gain medium onto the same equivalent phase plane, thereby achieving a unified mapping of spatially separated aberrations. Furthermore, it employs a step-by-step sequential optimization strategy to suppress the accumulation of aberrations along the amplification chain, thus effectively maintaining the beam quality of the solid-state laser under high-power output conditions.

[0009] Furthermore, the 4f relay imaging system sequentially images the front end face of the laser gain medium in each laser amplification stage onto the same equivalent phase plane; wherein, the position of the equivalent phase plane corresponding to the front end face of the laser gain medium in the nth laser amplification stage is determined by the lens focal length of the 4f relay imaging system after the nth laser amplification stage, as well as the length and refractive index of the laser gain medium. .

[0010] Furthermore, the spatial light modulator employs phase wrapping technology to apply conjugate phase compensation to the signal beam.

[0011] Preferably, a step-by-step sequential optimization strategy is used for wavefront pre-compensation, including: after the nth laser amplification stage is turned on, using a wavefront sensor to measure the residual wavefront distortion information of the current output beam, iteratively updating the compensation phase of the spatial light modulator, so that the nth stage... After the beam quality is restored to the target level after the first stage of amplification, the second stage is then activated. Laser amplification stage; among which .

[0012] Furthermore, in the step-by-step sequential optimization strategy, the first... Residual wavefront distortion information measured by the wavefront sensor after the laser amplification stage is turned on. Represented as: ; in, This represents the surface distribution of the spatial light modulator (SLM) when the n-1th level is enabled. For the first Thermal aberrations introduced by the laser amplification stage; ; The compensation phase is iteratively updated according to the gradient descent criterion: ; in, This represents the surface distribution of the spatial light modulator (SLM) after the (k+1)th iteration with the nth stage amplifier turned on. This represents the k-th iteration result of the spatial light modulator (SLM) with the n-stage amplifier turned on; This represents the wavefront information measured by the wavefront sensor in the k-th iteration; Let k be the number of iterations, where k takes values ​​of 0, 1, ... Let be the learning rate.

[0013] Furthermore, in the wavefront distortion information measured by the wavefront sensor, only astigmatic aberration and spherical aberration are compensated, and the first... Residual wavefront distortion information measured by the wavefront sensor after the laser amplification stage is turned on. The approximate expression using Zernike polynomial expansion is: ; in, Z 5 and Z 11 These are the astigmatic and spherical aberration terms in the Zernike polynomial, respectively. c 5 and c 11 These are the corresponding coefficients.

[0014] Furthermore, each 4f relay imaging system consists of two lenses. The signal beam is transmitted via the 4f system between the output of the preceding laser amplification stage and the input of the following laser amplification stage, suppressing the conversion of phase distortion to amplitude distortion during beam propagation.

[0015] Under the paraxial approximation, the optical field transformation between the object and image planes in a 4f relay imaging system is controlled only by the scaling of the lateral coordinates, while the spatial field distribution remains unchanged. For two focal lengths respectively... and The optical field transformation of a 4f system composed of lenses can be expressed as: ; in, This is the scaling factor.

[0016] Because the refractive index of the laser gain medium differs from that of free space, the position of the equivalent plane does not perfectly coincide with the front face of the crystal geometry. Considering the optical path within the gain medium, the equivalent plane is located behind the first lens in the corresponding 4f system. Among them For crystal length, is the refractive index of the crystal.

[0017] Preferably, each laser amplification stage uses an end-face pumped solid-state laser gain medium, which is a laser crystal or laser ceramic doped with rare-earth ions, and the pump source is a laser diode.

[0018] A wavefront precompensation method for a multi-stage solid-state laser amplifier, using the aforementioned multi-stage solid-state laser amplifier wavefront precompensation system, includes the following steps: S1, the signal beam emitted by the seed laser source; S2. After the signal beam is initially compensated by the spatial light modulator, it enters the first-stage laser amplification stage for amplification after passing through the first 4f relay imaging system. S3. The signal beam amplified by the first stage is transmitted to the front end of the second stage laser amplification stage through the second 4f relay imaging system. The second 4f relay imaging system images the front end of the laser gain medium in the first stage laser amplification stage onto the front end of the second stage laser amplification stage. S4. The signal beam is amplified sequentially through each laser amplification stage, and the light field is relayed between adjacent laser amplification stages through a 4f relay imaging system. S5. Sequentially turn on the first to Nth laser amplification stages. When each laser amplification stage is turned on, the wavefront sensor measures the wavefront distortion information of the output beam of the current stage laser amplifier; and iteratively update the compensation phase of the spatial light modulator based on the wavefront distortion information measured by the wavefront sensor.

[0019] Further, in step S3, the distance between the equivalent plane position corresponding to the front end surface of the laser gain medium in the first-stage laser amplification stage and the first lens of the second 4f relay imaging system is... ,in This is the focal length of the first lens in the 4f structure. The length of the laser gain medium. denoted as the refractive index of the laser gain medium.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention maps thermally induced aberrations generated in multiple spatially separated laser amplification stages to the same equivalent phase plane through a cascaded 4f relay imaging system. This enables the dispersed aberrations in the multi-stage amplification system to be uniformly corrected by a single low-power wavefront modulation device, avoiding the complex structure of setting wavefront correctors separately in each amplification stage.

[0021] 2. This invention adopts a step-by-step sequential optimization strategy, which completes wavefront compensation step by step during the sequential activation of each amplification stage. This decomposes the global optimization problem into a series of low-dimensional optimization steps, effectively suppressing the accumulation of aberrations along the amplification chain and improving the optimization convergence speed and compensation robustness.

[0022] 3. This invention places the spatial light modulator in the low-power optical path before the amplification stage, avoiding optical damage to the wavefront modulator caused by high-power laser, and breaking through the limitation of the power handling capacity of the wavefront modulator on the wavefront correction application of high-power laser systems.

[0023] 4. This invention only compensates for the dominant aberration modes (astigmatism and spherical aberration) that cause beam quality degradation, which greatly reduces the dimensionality of the optimization variables and significantly improves the optimization efficiency while ensuring the compensation effect. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structural principle of the multi-stage solid-state laser amplifier wavefront pre-compensation system according to an embodiment of the present invention.

[0026] Figure 2 This is an experimental optical path diagram of the wavefront pre-compensation system for a multi-stage solid-state laser amplifier according to an embodiment of the present invention.

[0027] Figure 3 The beam power and beam quality before and after compensation in this embodiment of the invention. A comparison chart of factors.

[0028] Figure 4 This is a comparison diagram of the Zernike coefficient compensation for wavefront distortion before and after in an embodiment of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be noted that, unless otherwise specified, the features in the following embodiments and implementation methods can be combined with each other.

[0031] like Figure 1 As shown, a multi-stage solid-state laser amplifier wavefront pre-compensation system includes a seed laser source for input laser light, a spatial light modulator (SLM), a 4f relay imaging system, a wavefront sensor (WFS), and N-stage laser amplification stages (AMP1, AMP2, ..., AMPN), where N ≥ 2, and a wedge plate. The signal beam emitted from the seed laser source is first pre-compensated and modulated by the spatial light modulator; the modulated beam then passes through a cascaded transmission link composed of multiple 4f relay imaging systems, and is incident on each stage of the laser amplification stage for power amplification; finally, the beam is split by the power attenuation device wedge plate, and the attenuated laser light is transmitted to the wavefront sensor to measure the wavefront distortion information of the multi-stage amplified signal beam; the spatial light modulator iteratively updates its compensated phase distribution based on the feedback signal from the wavefront sensor.

[0032] Its wavefront pre-compensation principle is as follows: the front end face of the laser gain medium in each laser amplification stage ( , ... The two beams, each serving as the object plane of the corresponding 4f relay imaging system, are mapped to the same equivalent phase plane after successive imaging transformations. At this equivalent plane, the thermally induced aberrations introduced by each gain medium are uniformly characterized. The spatial light modulator, located at the conjugate position of this equivalent plane, applies a phase distribution conjugate to the total aberrations to the seed beam under low power conditions, allowing the pre-compensated beam to gradually cancel out the phase distortions introduced by each gain medium during subsequent amplification. Simultaneously, the wavefront sensor detects the residual wavefront error of the output beam in real time, forming a closed-loop feedback loop to iteratively optimize the loading phase of the spatial light modulator until the output beam quality meets the requirements. Through the above principles, this invention achieves a unified characterization and sequential compensation of the accumulated aberrations generated by multiple spatial separation amplification stages.

[0033] like Figure 2 The diagram shown illustrates a specific experimental optical path for this invention. In this embodiment, a three-stage laser amplification structure is used to conduct a verification experiment on this invention.

[0034] A narrow-linewidth seed laser source outputs a laser beam with a center wavelength of 1064 nm and a linewidth of 10 kHz. This beam is boosted to 20 W by a pre-amplifier stage and used as the seed beam. The seed beam is then expanded to a diameter of 5.82 mm and incident on a water-cooled liquid crystal spatial light modulator (Hamamatsu X15223-03BR), where a pre-compensated wavefront distribution is applied. The spatial light modulator employs phase wrapping technology to achieve wavefront modulation, with a minimum modulation pixel size of 10. It can achieve high-precision fitting of aberration distribution.

[0035] The first 4f system behind the spatial light modulator serves both beam-shrinking imaging and zero-order diffraction suppression—an aperture mask is placed at the Fourier plane to filter out zero-order diffracted light. After filtering, the incident light power to the first-stage laser amplification stage is 16.7 W, and the beam radius is... =0.58 mm, with a fill factor of 0.82 relative to the 878 nm, 175 W pump laser diode (LD1). The first-stage laser amplification stage uses a 3×3×25 mm... 3 The laser consists of 0.2 at.% doped Nd:YVO4 crystal. The second and third laser amplification stages (LD2, LD3) use 914 nm pump laser diodes with a maximum output power of 450 W, which are then incident on a 4×4×40 nm gain medium after passing through a coupling lens. 0.5 at.% doped Nd:YVO4 crystal.

[0036] In the second-stage laser amplification stage, the beam radius is 0.61 mm and the fill factor is 0.83. In the third-stage laser amplification stage, after the signal power reaches a sufficiently high level, a beam radius of 0.7 mm and a fill factor of 0.63 are used to reduce the internal thermal effects of the crystal. The beam radius between each amplification stage is controlled by selecting an appropriate 4f system magnification.

[0037] After three stages of amplification, the output beam is imaged by the final 4f system, and after power attenuation by a half-wave plate (HWP) and a polarizing beam splitter (PBS), it is incident on the measurement plane of the wavefront sensor. The wavefront distribution applied to the spatial light modulator is dynamically updated based on real-time feedback from the wavefront sensor.

[0038] This embodiment employs a step-by-step sequential optimization strategy for wavefront compensation. After the first-stage laser amplification stage is activated, the wavefront distortion of the output beam is measured using a wavefront sensor. The compensation phase of the spatial light modulator is iteratively updated until the beam quality after the first-stage amplification is restored to the target level. Then, the second-stage laser amplification stage is activated, and so on. Compared to the method of performing uniform compensation after all amplification stages have been running at full power, the step-by-step sequential compensation strategy in this embodiment effectively avoids overcompensation and enhances convergence stability.

[0039] like Figure 3 As shown, in this embodiment, the seed beam undergoes power amplification through three stages of laser amplification. Under uncompensated conditions, the output power reaches 302 W, and the beam quality factor is [missing information]. The values ​​progressively deteriorate to 1.32 (after the first stage of amplification), 1.61 (after the second stage of amplification), and 1.86 (after the third stage of amplification). With the wavefront pre-compensation system of this invention, the entire amplification process... The value remains below 1.3, and the beam quality factor is maintained at around 1.25 when the final output power is 302 W. Compared with the uncompensated case, the compensation architecture of this invention effectively suppresses the accumulation of thermally induced aberrations during power amplification and maintains near-diffraction-limited beam quality.

[0040] like Figure 4 As shown, in this embodiment, the aberration measurements of the uncompensated laser output and the laser output using a step-by-step compensation strategy are compared. , These represent the astigmatism coefficient and spherical aberration after step-by-step magnification, respectively, without compensation. , These represent the aberration coefficients newly generated after the beam quality is restored under the successive compensation strategy, following the next stage. The astigmatism coefficient is the result of the final compensation. The aberration coefficient decreased from a significant value before compensation to near zero. Others were also significantly suppressed. Aberrations below the order of magnitude were not compensated because their impact on beam quality was negligible. The above results demonstrate that the strategy of compensating only for astigmatism and spherical aberration, which are the dominant factors degrading beam quality, is effective. This strategy significantly reduces the dimensionality of the optimization variables while ensuring compensation effectiveness, thus substantially improving optimization efficiency.

[0041] The combined output power of 302 W and beam quality factor of 1.25 demonstrate that the wavefront pre-compensation architecture proposed in this invention can simultaneously achieve high power amplification and beam quality maintenance, providing an effective technical solution for beam quality control of high-power multi-stage solid-state lasers.

[0042] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wavefront pre-compensation system for a multi-stage solid-state laser amplifier, characterized in that, It includes a seed laser source, a spatial light modulator, a 4f relay imaging system, a wavefront sensor, and an N-stage laser amplification stage, where N≥2; A 4f relay imaging system is arranged before the first laser amplification stage, between two adjacent laser amplification stages, and after the Nth amplification stage. The signal beam emitted from the seed laser source is phase-modulated by a spatial light modulator and then sequentially passes through the corresponding 4f relay imaging system to be amplified by each laser amplification stage; the signal beam output from the Nth amplification stage is received by a wavefront sensor after passing through a 4f relay imaging system. The wavefront sensor is used to measure the residual wavefront distortion information of the signal beam after multi-stage amplification; The spatial light modulator applies conjugate phase compensation to the signal beam under low power conditions based on the residual wavefront distortion information measured by the wavefront sensor, thereby achieving wavefront pre-compensation of the output beam.

2. The multi-stage solid-state laser amplifier wavefront pre-compensation system according to claim 1, characterized in that, The 4f relay imaging system sequentially images the front end face of the laser gain medium in each laser amplification stage onto the same equivalent phase plane; wherein, the position of the equivalent phase plane corresponding to the front end face of the laser gain medium in the nth laser amplification stage is determined by the lens focal length of the 4f relay imaging system after the nth laser amplification stage, as well as the length and refractive index of the laser gain medium. .

3. The multi-stage solid-state laser amplifier wavefront pre-compensation system according to claim 1, characterized in that, The spatial light modulator employs phase wrapping technology to apply conjugate phase compensation to the signal beam.

4. The multi-stage solid-state laser amplifier wavefront pre-compensation system according to claim 1, characterized in that, A step-by-step sequential optimization strategy is employed for wavefront pre-compensation, including: after the nth laser amplification stage is activated, measuring the residual wavefront distortion information of the current output beam using a wavefront sensor, and iteratively updating the compensation phase of the spatial light modulator to ensure that the wavefront pre-compensation is achieved. After the beam quality is restored to the target level after the first stage of amplification, the second stage is then activated. Laser amplification stage; among which .

5. The multi-stage solid-state laser amplifier wavefront pre-compensation system according to claim 4, characterized in that, In the stepwise sequential optimization strategy, the first Residual wavefront distortion information measured by the wavefront sensor after the laser amplification stage is turned on. Represented as: ； in, This represents the surface distribution of the spatial light modulator (SLM) when the n-1th level is enabled. For the first Thermal aberrations introduced by the laser amplification stage; ; The compensation phase is iteratively updated according to the gradient descent criterion: ； in, This represents the surface distribution of the spatial light modulator (SLM) after the (k+1)th iteration with the nth stage amplifier turned on. This represents the k-th iteration result of the spatial light modulator (SLM) with the n-stage amplifier turned on; This represents the wavefront information measured by the wavefront sensor in the k-th iteration; Let k be the number of iterations, where k takes values ​​of 0, 1, ... Let be the learning rate.

6. The multi-stage solid-state laser amplifier wavefront pre-compensation system according to claim 5, characterized in that, In the wavefront distortion information measured by the wavefront sensor, only astigmatism and spherical aberration are compensated, and the first... Residual wavefront distortion information measured by the wavefront sensor after the laser amplification stage is turned on. The approximate expression using Zernike polynomial expansion is: ； in, Z 5 and Z 11 These are the astigmatic and spherical aberration terms in the Zernike polynomial, respectively. c 5 and c 11 These are the corresponding coefficients.

7. The multi-stage solid-state laser amplifier wavefront pre-compensation system according to claim 1, characterized in that, Each 4f relay imaging system consists of two lenses.

8. The multi-stage solid-state laser amplifier wavefront pre-compensation system according to claim 1, characterized in that, Each laser amplification stage uses an end-pumped solid-state laser gain medium, which is a laser crystal or laser ceramic doped with rare-earth ions, and the pump source is a laser diode.

9. A wavefront pre-compensation method for a multi-stage solid-state laser amplifier, characterized in that, The wavefront pre-compensation system for a multi-stage solid-state laser amplifier according to any one of claims 1 to 8 includes the following steps: S1, the signal beam emitted by the seed laser source; S2. After the signal beam is initially compensated by the spatial light modulator, it enters the first-stage laser amplification stage for amplification after passing through the first 4f relay imaging system. S3. The signal beam amplified by the first stage is transmitted to the front end of the second stage laser amplification stage through the second 4f relay imaging system. The second 4f relay imaging system images the front end of the laser gain medium in the first stage laser amplification stage onto the front end of the second stage laser amplification stage. S4. The signal beam is amplified sequentially through each laser amplification stage, and the light field is relayed between adjacent laser amplification stages through a 4f relay imaging system. S5. Sequentially turn on the first to Nth laser amplification stages. When each laser amplification stage is turned on, the wavefront sensor measures the wavefront distortion information of the output beam of the current stage laser amplifier; and iteratively update the compensation phase of the spatial light modulator based on the wavefront distortion information measured by the wavefront sensor.

10. The wavefront pre-compensation method for a multi-stage solid-state laser amplifier according to claim 9, characterized in that, In step S3, the distance between the equivalent plane position corresponding to the front end surface of the laser gain medium in the first-stage laser amplification stage and the first lens of the second 4f relay imaging system is... ,in The focal length of the first lens. The length of the laser gain medium. denoted as the refractive index of the laser gain medium.

Images