光学薄膜损伤阈值是衡量光学薄膜抗激光损伤能力的重要参数,而要实现损伤阈值的测试必须先实现薄膜损伤的判识。利用光声频谱特性研究单层氧化硅薄膜在不同激光能量下的损伤情况,简要地分析了声频法判别薄膜损伤的可行性,建立了激光致薄膜产生的声波采集系统,比较和分析薄膜损伤前后的24~40 kHz高频段曲线,提取频率特征,并提出利用曲线相似函数进行薄膜损伤的识别。实验数据结果表明,该方法简单易行,可实现在线检测,又能准确判别薄膜损伤。

Laser induced damage threshold of optical thin films was always a critical parameter in measuring laser induced damage. The key to testing damage threshold was judging the injury incident accurately. The single oxide films damage with different laser energy was studied by the photo-acoustic method. A brief analysis was given on the thin film damage determined by acoustic frequency. The acoustic acquisition was established. We compared and analysed the frequency spectrum curve from 24~40 kHz between the damaged film and undamaged one. By extracting frequency features and establishing frequency curve similarity function, it is possible to judge whether the optical film is damaged. The experimental result shows that acoustic frequency method can be easily efficient to judge accurately film damage and it can be also used in online inspection conveniently.