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

Abstract

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.

Keywords

• variable reflectivity mirrors (vrm)
• pvd
• fesem
• laser induced damage threshold (lidt)