基于传热学理论,利用有限元法对KrF准分子激光辐照K9玻璃样品中的热力效应进行了数值分析,并比较了脉冲数目和重频对损伤效果的影响。研究表明,较低的准分子激光能量就能够使K9玻璃在表面和体内产生热应力损伤,热应力损伤在光斑区域内主要由压缩热应力控制,在光斑边缘和材料内部则主要由拉伸热应力控制。在激光脉冲结束时刻,产生的温度和热应力最大,且热应力以热冲击波的形式在材料内传播,随时间变化而来回振荡,逐渐减弱。这种热应力的反复冲击会对材料产生持续的损伤增长效应,增加了材料的损伤时间,并使材料更容易断裂。脉冲数目和重复频率对损伤效果有着较大影响,在高重复频率下,损伤累积效应明显。

A numerical simulation is performed to calculate temperature and stress distributions in K9 glass sample irradiated by KrF excimer laser using finite element method, and the relationship between laser parameters and damage effect is also studied. The simulation results indicate that the damage of K9 glass irradiated by KrF excimer laser is thermal stress damage when the incident laser energy is low. The stress damage in laser spot area is dominated by compressive stress, and the damage near the edge of the spot or inside the K9 glass is dominated by tensile stress. The thermal stress as shock wave oscillates obviously inside the K9 glass sample. It is shown that repetition frequency and the number of pulses affect damage considerably, and the accumulation of multi-shot laser induced damage in K9 glass is obvious.