单脉冲和多脉冲飞秒激光对单层光学薄膜的损伤
Single-pulse and multi-pulse femtosecond laser damage of optical single films
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摘要: 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。Abstract: Laser-induced damage of a single 500 nm HfO2 film and a single 500 nm ZrO2 film were studied with single- and multi-pulse 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 HfO2 single film was higher than that of the ZrO2 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.
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Key words:
- femtosecond /
- laser-induced damage threshold /
- single-pulse /
- multi-pulse /
- optical film /
- multiphoton ionization
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