Investigation of the laser induced damage thresholds of all-dielectric and metal-dielectric mirrors for a continuous wave at 10.6 μm

Abstract

Thin films have many applications in the field of optics and photonics. One of these applications is the fabrication of high-reflection mirrors for high-power lasers. High-power lasers also require mirrors with high laser induced damage threshold (LIDT). In this research, firstly, considering the principles of simulation, we have tried to design two types of mirrors, all-dielectric and metal-dielectric. Therefore, they are suitable in terms of both the reflectance spectrum and LIDT at 10.6 μm. To simulate and fabricate these two types of mirrors, ZnSe and Ge have been used as substrates and for thin film layers, Ge and ZnS have been used. In metal-dielectric mirrors, gold layers have also been used on the substrate as the metal layers. After design and simulation, the process of mirrors' fabrication was done by electron beam evaporation technique and the reflectance spectrum of the samples was taken, which shows the reflectance of all-dielectric mirrors is more than 99% and that of Metal-dielectric mirrors is more than 99.9%. Finally, measuring the LIDT of these two types of mirrors was performed based on ISO21254-1 2011 standard which shows that the metal-dielectric mirror with ZnSe substrate is the most suitable mirror for continuous lasers at 10.6 μm.