Laser-Induced Damage of HfO₂/SiO₂ Irregular High Reflectivity Films by 1064 nm and 532 nm Lasers

Regular film system is a common thin film structure,but it is often unable to meet the ideal laser transmission effect and instrument use effect.Therefore,under the requirements of the laser system and transmission window,the irregular film system is optimized based on the design basis of the regular film system for obtaining a good laser transmission effect.The HfO₂/SiO₂ irregular high-reflectivity film was prepared by the electron beam thermal evaporation method,and the laser-induced damage of the film was tested by pulses of 1064 nm&10 ns,and 532 nm&10 ns,respectively.The damage morphology was characterized by Nikon L150 optical microscope and ZY-GO white light interferometer.The laser-induced damage threshold and damage morphology at these two wavelengths are compared.The results are as follows:the typical damage morphology of laser-induced damage at two wavelengths shows pits under low-energy pulse irradiation,with a certain area of ablation area around it,and shows material delamination under high-energy pulse irradiation;in the process of film damage testing of two wavelengths,the damage threshold of 1064 nm laser is 5.64 J/cm²,and the damage threshold of 532 nm laser is 1.54 J/cm²,and the damage usually starts near the peak of the electric field;the damage morphology at different wavelengths may be related to the thermal stress caused by defect absorption,and the damage morphology is approximately circular in 1064 nm’s damage test,irregular damage morphology at 532 nm.The following conclusions can be drawn from the analysis:the anti-laser damage ability of the film under 1064 nm laser is better than that under 532 nm laser;the damage morphologies under 1064 nm and 532 nm laser are both concave damage;the interface field strength and peak field strength of the film under 1064 nm laser are both higher than that under 532 nm laser.