Laser damage resistance of 248 nm HR films

Abstract

HfO2/ SiO2 high reflection(HR) films with conventional quarterwave design were deposited by electron beam evaporation on fused silica substrate for the wavelength 248 nm. Two kinds of protective layer were designed and prepared to resist laser induced damage. For one sample half wavelength thick SiO2 were deposited on conventional quarterwave (HL)11H films as a protective layer, for the other sample Al2O3/MgF2 coatings were deposited as protective layers. Laser induced damage were tested. Through changes of the damage morphology, causes of laser resistance improvement and problems still exist were analyzed.