熔融石英基片热形变及其对光束质量的影响分析

Thermal deformation of fused silica substrates and its influence on beam quality

熔融石英基片受高能激光辐照后,受热产生的热形变会恶化系统出射的光束质量。为了研究光束质量的恶化情况,采用COMSOL有限元分析软件,建立了在连续高能激光辐照下熔融石英基片热形变分析模型,并针对基片在不同的夹持方式下的热形变进行了比较分析,得到了基片受热后的温度分布和形变分布情况,并利用VirtualLab软件定量分析了熔融石英基片热形变对光束质量的影响。结果表明,采用四周固定的方式,热形变量是最小的;基片的热形变会对光束质量造成影响,激光辐照时间越长,热形变量越大,对光束质量影响越大;当基片被激光辐照20s后,采用夹板固定的基片最大形变量达到415.90nm,光束质量因子M_x^2由1.0036恶化至1.4571;采用四周固定的基片最大形变量达到98.38nm,光束质量因子M_x^2由1.0036恶化至1.0064。这一结果对后续激光合束系统搭建以及光束质量优化有重要的指导意义。

When fused quartz substrates are irradiated by high energy laser, the thermal deformation caused by heating would deteriorate the beam quality emitted by the system. In order to study the deterioration of beam quality, COMSOL finite element analysis software was used. The thermal deformation analysis model of fused quartz substrates irradiated by continuous high energy laser was established. The thermal deformations of the substrates under different clamping modes were compared and analyzed. The temperature distribution and deformation distribution of the substrate after heating were obtained. The effect of thermal deformation of fused quartz substrates on beam quality was quantitatively analyzed by VirtualLab software. The results show that, the thermal deformation is the smallest in boundary fixation. The thermal deformation of the substrate will affect the beam quality. The longer the laser irradiation time, the greater the thermal deformation, the greater the impact on the beam quality. When the substrate is irradiated by laser for 20s, the maximum deformation of the substrate of splint fixation is 415.90nm. The beam quality factor is deteriorated from 1.0036 to 1.4571. The maximum deformation of the substrate of boundary fixation is 98.38nm. The beam quality factor is deteriorated from 1.0036 to 1.0064. This result has important guiding significance for the subsequent laser beam combining system construction and beam quality optimization.