Thermal Effect Simulation Of Non-uniformly Pumped High-energy Slab Laser

Optoelectronic countermeasures are an important part of modern combat,and laser countermeasures are the core part of this field.In order to improve their optoelectronic countermeasures,various countries have successively carried out a large number of laser weapon research and development and experimental work.At present,with the development of semiconductor laser technology,semiconductorpumped slab lasers have gradually become one of the most commonly used lasers in laser weapons.This article mainly focuses on the simulation and analysis of the thermal effect of the slab laser,provides suggestions for improving the performance of the slab laser and the research and development of new slab lasers,and lays the foundation for the all-digital simulation of laser weaponsThis article first introduces the working principle of the slab laser and the concept and production method of the thermal effect.The current development status of the slab laser at home and abroad and the research status of the slab laser thermal effect at home and abroad have been combed,and it is found that although the current slab laser The method has been improved many times,but the thermal effect of the laser is still the biggest problem that affects the beam quality;in the research of thermal effect,there is still a lot of room for improvement in the authenticity of the theoretical model.In addition,from the perspective of the completeness of the model,the laser gain There is a lack of thermal effect models for the entire process of laser beam output.Aiming at the authenticity of the thermal effect theoretical model,this paper establishes a non-uniform pump light field model that is more in line with the real situation based on the output beam characteristics of the semiconductor laser array.According to the Lambert-Beer absorption law,a more accurate heat source model in the lath medium is established,based on the internal heat source model and the nonuniform pump light field model.The temperature distribution and stress distribution equations of the slat medium are deduced;the calculation methods of thermally induced wavefront distortion and thermally induced stress birefringence are further analyzed,and the calculation formula of the thermal lens focal length of the slat medium is deduced.According to the established theoretical model and derived calculation formula,and according to the real crystal parameters and the working mode of the slab laser,the temperature field and stress field of the slab medium under four different pump powers of 100 W,200W,400 W,and 800 W are simulated.,The thermal expansion effect and the thermally induced wavefront distortion effect that has the greatest impact on the quality of the laser beam.According to the simulation results,it is found that the temperature,stress and thermal expansion are mainly concentrated on the end face of the medium,that is,the thermal effect is mainly generated on the end face of the medium and changes with the increase of pump power.Finally,the thermal effects of four different pump power laser beams of 100 W,200W,400 W,and 800 W on the subsequent collimating and focusing system after being output from the slab medium are simulated,and it is found that the center of the collimating and focusing lens is most seriously affected by heat,along the radial direction.The outward influence gradually weakens.In addition,the influence of thermal influence on the output laser beam is to move the focus position of the laser beam forward,and the higher the laser beam power,the greater the forward movement.The RMS radius of the focused spot becomes smaller as the power increases.And gradually deformed.After that,a collimated beam expanding optical system that corrects the thermally induced wavefront distortion and matches the simulated slab laser is designed.The wave image is smaller than the Rayleigh criterion,which can achieve 5 times the beam expansion and0.25 times the compressed beam divergence.