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 1064 nm, two types of variable reflectivity laser mirrors with (HfO2/SiO2) and (ZrO2/SiO2) materials are fabricated by electron beam evaporation method. The central reflectivity of R0 =30 and 35 % for two super Gaussian orders of n=3 and 4 is manufactured and qualified by ellipsometry and laser beam scan methods. The Laser-induced damage threshold experiments demonstrated that, the VRMs with multilayers of HfO2/SiO2, have a higher Laser-induced damage threshold than ZrO2/SiO2, which was 10 J/cm2 and 7 J/cm2, 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.

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

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