单脉冲和多脉冲飞秒激光对单层光学薄膜的损伤

 利用掺钛的蓝宝石飞秒激光系统输出的单脉冲和多脉冲飞秒激光(中心波长800 nm，脉宽50 fs，靶面聚焦直径Ф 40 μm)，分别对BK7玻璃基底上厚约500 nm的单层HfO₂和单层ZrO₂薄膜进行辐照，得到了这两种薄膜在1-on-1和1 000-on-1测试方法下的激光损伤阈值。实验发现，两种方法下HfO₂单层膜的阈值均比ZrO₂单层膜的阈值高。从简化的Keldysh多光子离化理论出发，认为HfO₂薄膜材料的带比ZrO₂的宽是导致上述结果的主要原因。同时，同一种薄膜的多脉冲下的阈值比单脉冲下的低，原因是多脉冲下，飞秒激光对光学薄膜的损伤存在累积效应。

Single-pulse and multi-pulse femtosecond laser damage of optical single films

Laser-induced damage of a single 500 nm HfO_2 film and a single 500 nm ZrO_2 film were studied with single-and multipulse femtosecond laser.The laser-induced damage thresholds(LIDT) of both samples by the 1-on-1 method and the 1 000-on-1 method were reported.It was discovered that the LIDT of the HfO_2 single film was higher than that of the ZrO_2 single film by both test methods,which was explained by simple Keldysh' s multiphoton ionization theory.The LIDT of multi-pulse was lower than that of single-pulse for both samples as a result of accumulative effect.