强激光系统光束质量的非线性退化及补偿研究

Research on Nonlinear Degeneration and Compensation of Beam Quality in High Power Laser System

为了在强激光非线性传输仿真中综合考虑系统像差等因素,提出了一种基于光线追迹的非线性介质光追方法,并编程实现了线性介质与非线性介质的混合建模。以三片式聚焦系统为例,在系统中加入KDP晶体作为非线性介质,仿真分析了不同激光功率密度下KDP晶体的非线性效应对光束质量的影响。仿真结果表明,当激光功率密度达到1.62×1010 W/cm2时,非线性效应会导致光束质量明显下降。在该仿真结果的基础上提出了在不改变焦面位置的情况下,将元件间隔作为补偿器进行系统优化的方法。优化结果表明,焦斑尺寸较优化前减小2.8μm,规范尺寸下的环围能量提高了16.2%,焦面处的光束质量得到显著改善。

In order to consider factors such as system aberrations into account in the nonlinear propagation simulation of high power laser, a ray-tracing method for nonlinear media is presented, and hybrid modeling for linear and nonlinear media is realized through programming. Three-lens focusing system with KDP crystal as the nonlinear media is taken as an example, and simulation analysis of the influence of nonlinear effect on beam quality is conducted with different laser power densities. The simulation results show that when the laser power density reaches 1.62 × 1010 W/cm2 , the laser beam quality is degenerated evidently by nonlinear effect. Based on the simulation results, an optimization method, which takes the optical component intervals as compensation without changing the position of focal plane, is presented. The optimization results show that the focal spot size decreases by 2.8μm, and the encircled energy under standardized dimension increases by 16.2%, thus the beam quality at focal plane is significantly improved.