Quality Assessment of Variable Reflectivity Laser Mirrors with High Laser –Induced Damage Threshold and Structural Analysis

Abstract: We report the results of an experimental study on the fabrication of a multilayer variable reflectivity laser mirror and the morphological analysis of optical thin film layers. In a design procedure, a series of variable reflectivity laser mirrors are fabricated and characterized with different methods. In this research, based on pulsed solid-state Nd:YAG lasers at ۱۰۶۴ nm, two types of variable reflectivity laser mirrors with (HfO۲/SiO۲) and (ZrO۲/SiO۲) materials are fabricated by electron beam evaporation method. The central reflectivity of R۰ =۳۰ and ۳۵ % for two super Gaussian orders of n=۳ and ۴ is manufactured and qualified by ellipsometry and laser beam scan methods. The Laser-induced damage threshold experiments demonstrated that, the VRMs with multilayers of HfO۲/SiO۲, have a higher Laser-induced damage threshold than ZrO۲/SiO۲, which was ۱۰ J/cm۲ and ۷ J/cm۲, correspondingly. Also, in a novel and exact FESEM approach, the morphological structure of the VRM thin layers was monitored which gives a deeper insight into the layer structure and helped us to calibrate the PVD device for shaped VRM.

کلیدواژه ها:

Variable Reflectivity Mirrors (VRM) ، PVD ، FESEM ، Laser induced damage threshold (LIDT)