Laser-induced damage threshold detection for optical thin films and research on damage morphology

Abstract

Laser-induced damage threshold of prepared diamond like carbon films(DLC) and HfO₂/SiO₂ reflective coatings are detected respectively by He-Ne laser scattered measurement system and plasma spark test method. He-Ne laser scattered measurement system is to judge the damage of thin films by measuring energy change of He-Ne scattering light on the same sample spot. Plasma spark testing method is to judge the damage by observing whether plasma spark occurs or not. Different damage morphology is observed by 1000 multiple microscope. When the laser energy is lower than its damage threshold, some slight ablition comes about; when the laser energy is stronger than its damage threshold, the abscin of thin films and the change in fundus' colour are observed. The results are in accordance with the observation on Zygo GPI interferometer. The two testing methods are compared based on the analysis of the damage morphology. When the plasma spark occurs, there is no damage on thin films, which shows that there is no definite relationship between the plasma spark and the degree of damage on thin films. However the judgement of damage made by using He-Ne laser scattered measurement system is quantitative. This system can judge laser-induced damage effectively.