单脉冲飞秒脉冲激光对单层和高反光学薄膜的损伤

用电子柬蒸发的方法在BK7玻璃上制备了ZrO2单层膜和ZrO2／SiO2高反膜，利用掺Ti：sapphire飞秒激光系统输出的中心波长为800nm，脉宽为50fs的激光脉冲对这两种样品进行了激光损伤阈值测试．实验结果表明，ZrO2单层膜的阂值比ZrO2／SiO2高反膜的高；这与传统的纳秒脉冲激光的损伤情况相反．利用光离化和碰撞离化激发电子到导带，形成电子等离子体基本模型并对此现象进行了解释．同时，用显微镜对样品的损伤形貌进行了观测，对损伤的特点进行了表征．

Single-shot laser-induced damage test was performed in air employing Ti:sapphire laser pulses with duration 50 fs, center wavelength 800 nm. ZrO<inf>2</inf> single layer and ZrO<inf>2</inf>/SiO<inf>2</inf> high-reflective (HR) coating served as targets, which were prepared by electron beam evaporation technology on BK7 glasses. It was found that the LIDT of the ZrO<inf>2</inf> single layer was higher than ZrO<inf>2</inf>/SiO<inf>2</inf> HR coating. A theoretical model based on conduction band electrons produced by photoionization and impact ionization was applied to discuss the phenomenon. Meanwhile, damage morphologies of the samples were observed by Leica optical microscopy to show the damage characters.