Mirrors for high-power cw argon lasers

An investigation was made of the characteristics of mirrors for a high-power cw argon laser operating in the visible range. The mirrors were made by three different methods, namely by thermal resistive sputtering, by electron-beam evaporation, and by cathode sputtering. For the best samples, the scattering coefficients were 0.04–0.1% and the absorption coefficients were 0.02–0.03%, independently of the method used to make them. The optical strength was not directly related to the scattering and absorption in the coatings, but depended on the method of preparation. Cathode-sputtered mirrors were found to have the best operating qualities in high-power cw argon lasers. The question of thermal focusing of a laser due to surface absorption in the exit mirror is discussed.