高能激光系统内光路热效应建模与仿真

高能激光系统内光路热效应是影响系统性能的重要因素,介绍了内光路中光学元件、介质气体热效应物理模型,分析了影响热效应的主要因素,并开展了热效应变化规律研究。针对光学元件,重点研究了元件吸收率、元件材料特性、光斑分布对反射镜、窗口镜、分光镜热像差的影响规律,指出吸收率主要影响热像差的大小,而元件基底材料特性和激光分布影响热像差时间和空间变化。针对介质气体,指出介质气体升温后重力引起的自然对流是影响气体热像差的主要物理因素,细致研究了热像差随时间的变化规律,介绍了降低封闭与开放式内光路介质气体热像差的措施与方法。介绍了激光仿真软件平台Easylaser多物理仿真模块,搭建了包含反射镜、窗口镜、分光镜和介质气体的内光路计算模型,通过光-热-力-控多物理耦合仿真,研究了反射镜与窗口镜、介质气体与窗口镜热像差补偿效应,给出了激光传输远场光斑特征,表明了Easylaser的多物理仿真模块具备对内光路热效应综合仿真分析能力。

Modeling and analysis of inner thermal effects in high energy laser system

This paper discusses the thermal effects of optical components and media gas in inner propagation of high energy laser system, which is very important for the performance. The thermal aberration models of optical components and media gas, the influencing factors, and the changing laws are introduced. For optical components, some physical factors are emphatically analyzed, including absorptivity, characters of the materials, and laser spot distributions. The results show that the level of thermal aberrations depends on the absorptivity, and spatio-temporal characters depends on the material and the distribution of laser spot. For media gas, the variation of thermal aberrations depend on switch of physical mechanism, heat conduction and heat convection for temperature increment, and the law of time dependent thermal aberrations are studied carefully. Methods and measures of reducing thermal effect are introduced for closed and opened system. The multi-physical module of a software named Easylaser is introduced and is used to simulate the thermal effects of a laser inner propagation, including reflective mirrors, a optical window, a spectroscope, and media gas. The results show that the aberrations between reflective mirrors and the optical window, and between gas and the optical windows could be complementary. The characters of laser spot in far-field are also simulated. All the results demonstrate that Easylaser can be used to simulate and analyse the thermal effects in high power laser system.