Laser-induced damage threshold detection for optical thin films by scattered light of He-Ne laser

Precise measurement of the laser-induced damage threshold can be used to effectively evaluate the laser damage resistance of optical thin films. The determination of laser-induced damage threshold is dependent on the criteria to judge whether damage happens to the optical thin film or not. A measurement system with He-Ne laser scattered light was set up to detect the laser-induced damage threshold of optical thin films. The damage level of thin films was judged by measuring the variation of He-Ne laser scattered light energy at the same point on a sample. The damage threshold measurement for the diamond-like carbon films (DLC) and HfO2/SiO2 reflective coatings was performed. The measured result was compared with that of plasma spark method. Both of them have a preferable consistency. The analysis shows that the He-Ne laser scattering measurement system can be used effectively to determine laserinduced damage and it can be used in online inspection conveniently.