Thermal effects of a laser beam tube consisting of a window and nonflowing gas

Abstract

High-energy laser systems include an optical train and a gas medium that must be capable of transporting and directing the beam. The optical train is termed a laser beam tube. Because of the finite absorption of laser energy, the thermal effects of the beam tube make the beam diffuse and cause degradation of the laser beam's quality. We study systematically a beam tube consisting of a laser window made from white bijou (i.e., Al2O3) or fused silica and a tube of nonflowing nitrogen or helium gas. The results show that the thermal effects of the window and the gas on the beam neutralize each other; in particular, in some cases they compensate for each other completely, such that the beam tube has no effect on the beam quality in spite of the fact that separately each has a severe effect. We explain how to acquire the specific cases.

The influence of high-frequency phase and correction distance on the phase correction effect

“…The key factors that cause this phenomenon are the tilting of cavity mirrors [1,2], the thermal deformation of cavity mirrors [3,4], the non-uniformity of gain medium [5,6], etc. An adaptive optics (AO) system can effectively improve beam quality by using a Shack-Hartmann sensor (S-H) to measure the wavefront phase and an optical deformable mirror (DM) to compensate the distorted wavefront [7,8].…”