利用时间分辨激光光度计实时测量纳秒脉冲激光诱导熔石英体损伤过程中的透射、反射和散射变化量;通过在同一区域多次动态测量直至损伤产生,获得了多脉冲累积破坏的时间分辨过程。结果表明:在损伤出现前的脉冲辐照过程中,熔石英透过率已明显下降,后向反射率同步上升,甚至可达70%;后向反射率的上升量与透过率的损失量几乎相同;在多脉冲辐照过程中,只要脉冲辐照中出现后向反射,就会产生损伤;受激布里渊散射对多脉冲诱导熔石英体损伤具有促进作用。

In this study, a time-resolved laser photometer was applied to measure the real-time variations in transmission, reflection, and scattering during the nanosecond laser irradiation of bulk fused silica. The time-resolved process of multi-pulse accumulative damage can be obtained via the multiple dynamic measurements in a single region till the damage occurs. The results show that the transmission considerably decreases during the pulse irradiation process prior to the occurrence of damage, and the backward reflectivity simultaneously increases, even up to 70%. The increase in the backward reflectivity is almost equal to the decrease in the transmission. The statistical analysis results show that as long as there exists backward reflection during multi-pulse irradiation, damage can occur. Stimulated Brillouin scattering promotes the multi-pulse-induced damage in bulk fused silica.