Effects of the Processing Technology of CVD-ZnSe, Cr2+:ZnSe, and Fe2+:ZnSe Polycrystalline Optical Elements on the Damage Threshold Induced by a Repetitively Pulsed Laser at 2.1 µm

Abstract

Polycrystalline zinc selenide (ZnSe) and Cr2+ or Fe2+ doped ZnSe are key optical elements in mid-infrared laser systems. The laser-induced damage of the optical elements is the limiting factor for increasing the power and pulse energy of the lasers. In the present work, the optical damage of the ZnSe, Cr2+:ZnSe, and Fe2+:ZnSe samples induced by a repetitively pulsed Ho3+:YAG laser at 2091 nm was studied. The probability of the optical damage and the laser-induced damage threshold (LIDT) were determined for the samples manufactured using different processing techniques. The highest LIDT was found in ZnSe samples annealed in an argon atmosphere. It was also found that the samples annealed in a zinc atmosphere or with hot isostatic pressing resulted in a decrease in the LIDT. The Cr2+-doped ZnSe had the lowest LIDT at 2.1 µm compared to Fe2+-doped or undoped ZnSe. The LIDT fluence of all tested ZnSe samples decreased with the increase in the pulse repetition rate and the exposure duration. The results obtained may be used to improve the treatment procedures of ZnSe, Cr2+:ZnSe, and Fe2+:ZnSe polycrystals to further increase their LIDT.