Correlation between defect absorption and nano-second laser-induced damage of HfO2/SiO2 based high reflective coatings at 1064 nm

Abstract

The distribution of defect weak absorption and nanosecond pulse laser induced damage characteristics of HfO2/SiO2 multilayers were investigated. A combination of in-situ measurements of defect weak absorption distribution and laser induced damage threshold (LIDT) map was proposed, whereby the evolution of defect weak absorption and the laser induced damage morphology under laser irradiation was studied. During the laser irradiation, some nodular and scalded defects can be removed or passivated by the low flux laser, and the absorption of these defect types was reduced accordingly. Besides, catastrophic destruction defects with enhanced absorption after laser irradiation would develop into catastrophic damage. Further, two-dimensional scanning of the sample surface was used to study the relationship between defects weak absorption and the LIDT. The results indicated that the correlation of defects weak absorption intensity distribution and LIDT map depended on defect evaluation properties during the laser irradiation.