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 HfO 2 /SiO 2 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.

Functional gradient films on aluminum alloy to improve its laser‐induced damage ability and reduce pollutant particles’ generation

“…Laser‐induced damage of dielectric materials can be attributed to photo‐ionization, 29 the valence‐electron density, 30 and the free‐electron density 31 . Plasma spark test methods, combined with inverse estimations of the damage threshold from multi‐pulse lasers, and the measurements of point areas induced by multi‐pulse lasers, have been used to assess damage 32 . However, the detector receiving the flash signal emitted from the film sample or surrounding areas can be easily obscured by subjective factors and the capability of the facilities 33 .…”

“…31 Plasma spark test methods, combined with inverse estimations of the damage threshold from multi-pulse lasers, and the measurements of point areas induced by multi-pulse lasers, have been used to assess damage. 32 However, the detector receiving the flash signal emitted from the film sample or surrounding areas can be easily obscured by subjective factors and the capability of the facilities. 33 Furthermore, the plasma spark test associated with other steps is tedious and complex, which could reduce the experimental accuracy.…”

Evaluation damage threshold of optical thin-film using an amplified spontaneous emission source

“…To achieve the precise measurement of the LIDT, many researchers have focused on the test method of the laser acting on medium 9 , the detection of damage morphology 10,11 , the calculation method of the LIDT 12 , and so on. However the uniformity of the irradiation source for damage threshold test has not been paid enough attention to.…”