提出利用镀膜合束的方法对三路光束进行合束用于高功率红外激光合束系统设计。考虑系统中关键元件使用的红外材料ZnSe易受热效应影响, 采用光机热耦合分析方法, 研究了在温度边界条件固定时, 各波段激光所产生的耦合热效应对各路激光波前畸变的影响, 同时定性分析了系统中存在的激光偏置热效应。研究结果显示, 系统中各波段的激光波前畸变均方根值(RMS)均满足设计要求(各波段波前畸变小于λ/8); 激光偏置造成的波面高频成分增大了长波激光波前畸变量, 但高频成分对系统波前畸变影响依然满足要求; 轴向温差可在35 s达到平衡, 对光束波前造成主要影响的是各块镜片的面型畸变。根据分析结果搭建了实验平台, 利用系统中短波400 W激光进行实验, 采集了该条件下的面型并与仿真结果进行了对比, 实验结果验证了该分析方法计算结果的准确性。

A beam combination method based on the optical coating was proposed for three light paths to design a high power infrared laser multi-band beam combination system. As the ZnSe used as substrate materials of a beam combination mirror was easy to be susceptible to thermal effects, the optical-mechanical-thermal coupling analysis was used to research the influence of coupled thermal effect caused by laser irradiation in different wave bands on laser wavefront distortion of each band under the fixed temperature boundary conditions. Meanwhile, the thermal effect caused by beam biased was analyzed qualitatively. Simulation results show that the wavefront distortion (Root Mean Square, RMS) of each band laser is able to satisfy the design requirements(the wavefront distortion needs to be less than λ/8). The high-frequency component increases the distortion of a long wave laser, but it still meets the system requirement. The axial temperature difference reaches the equilibrium after 35 s, so the main factor of wavefront distortion is the surface distortion of every mirror. An experimental testbed was set up based on the analysis results, and the experiments were carried out on a 400 W short wavelength laser. The surface data were obtained and compared with that of the simulation, and the results validate the feasibility of the proposed analytical method.