对卡塞格林式多程放大器中环形光束传输的数值模拟

利用光线追迹法以及分步傅里叶-贝塞耳变换法,考虑了光阑对光束的拦截和通光作用以及激光放大过程中的增益饱和效应,对环形腔调Q钕玻璃激光系统振荡器输出的光束经卡塞格林式放大器多程放大后的光场演化过程进行了数值模拟,并进行了实验验证。分析得出现有系统中输入输出镜的阶跃反射率分布是导致输出环形光束质量不好的主要原因,并重点对放大器的腔镜部分进行了优化设计,提出了反超高斯反射率分布的输入镜与超高斯反射率分布的输出镜相组合的腔镜对结构。数值模拟结果表明,该腔镜对的使用可大大改善输出环形光束的质量。

Numerical Simulation for Transformation of Annular Laser Beam in Cassegrain Multi-Pass Amplifier

Taking account of the transmission characteristics of the diaphragm and the saturation of the gain in the process of light amplifying, the evolution of the beam inside the Cassegrain multi-pass amplifier is numerically simulated by using the ray-tracing and split-step fast Fourier-Bessel transform (SSFFT) methods, the annular beam is coming from Q-switched Nd∶glass laser with ring cavity. Preliminary experimental verification has been carried out. Analysis indicates that the staircase-like features of the input and output mirror reflections are responsible for the poor quality of the output annular beam, and special attention has been paid on optimizing amplifier configuration. As a result, a new type of amplifier configuration is proposed, whose input mirror has an anti-super Gaussian reflection distribution and output mirror has a super-Gaussian reflection distribution. The simulated results indicate that the use of the mirror couple can improve the quality of the output annular beam considerably.