根据已经建立的紫外准分子激光损伤典型光学材料的理论模型, 研究了准分子激光对透明光学材料(石英玻璃)和非透明光学材料(K9玻璃)的损伤特性, 并结合实验结果证实了理论模型的有效性。研究表明: 在准分子激光对非透明光学材料辐照下, 激光光斑半径越大, 产生的热应力和温度越小; 脉宽越小, 产生的热应力越大; 随着脉冲数的增加, 温度和热应力都逐渐增大。值得注意的是, 当重频增加至45 Hz以上时, 熔融损伤阈值开始低于应力损伤阈值, 这说明当重频增加到一定程度时, 非透明光学材料将首先产生熔融损伤, 而不再是应力损伤。在准分子激光对透明光学材料辐照下, 杂质微粒的半径和掩埋深度对光学材料温度场分布有着重要影响。但当杂质半径和掩埋深度超过一定的数值时, 杂质粒子的存在与表面温度并无联系。理论模型能够较好地解释石英玻璃前/后表面相同的初始损伤形貌特征。

According to the theoretical model of typical optical materials damaged by ultraviolet excimer laser, a numerical simulation was performed to calculate temperature and thermal stress fields using finite element method. The damage effects of excimer laser on transparent optical material (fused silica) and non transparent optical material (K9 glass) were investigated, and the validity of the theoretical model was confirmed by the experimental results. The simulation results indicate that the laser parameters exhibit a great effect on damage effect and damage threshold. It is worth noting that the melting damage threshold is lower than the stress damage threshold when the repetition rate increases to more than 45 Hz. The thermal damage of excimer laser to the strongly adsorbed impurities on the surface of fused silica is also analyzed. The theoretical analysis is in agreement with the same initial damage morphology of fused silica surface.