Use of resonators with graded reflectivity mirrors in transverse flow CO2laser sources

Abstract

The design and the use of positive branch unstable resonators with variable reflectivity mirrors are described in the case of two different transverse flow CO, lasers: a TEA source for LIDAR Doppler applications and a high average power DC excited source for industrial applications. In the first case, Ge and ZnSe mirrors with Gaussian and super-Gaussian reflectivity profiles have been employed. In the second one, ZnSe mirrors with Gaussian and super-Gaussian reflectivity profiles have been employed as well as partial hard-edge reflectivity mirrors with and without phase compensation. Beams with 40 mm diameter and full-angle divergence of about 1 mrad were typically obtained in both cases. The TEA source was operating in single longitudinal mode with 1J per pulse energy, while 1 kW output power was obtained from the industrial source.