Study on high-reflective coatings of different designs at 532 nm

Conventional HfO2/SiO2 and Al2O3/HfO2/SiO2 double stack high reflective(HR) coatings at 532 nm are deposited by electron beam evaporation onto BK7 substrates. The laser-induced damage threshold(LIDT)of two kinds of HR coatings is tested, showing that the laser damage resistance of the double stack HR coatings(16 J/cm2) is better than that of the conventional HR coatings(12.8 J/cm2). Besides, the optical properties, surface conditions, and damage morphologies of each group samples are characterized. The results show that laser damage resistance of conventional HR coatings is determined by absorptive defect,while nodular defect is responsible for the LIDT of double stack HR coatings.