Abstract

The insertion of variable reflectivity mirrors in unstable resonators has been shown^1,2 to be a solution of the detrimental effects from edge diffraction by hard apertures. We describe experimental results obtained with a pulsed low-magnification Cassegrain Nd:YAG laser using a mirror with a parabolic reflectivity profile. Such a profile was selected because it yields a fundamental mode which matches the laser medium, thus allowing an optimized extraction efficiency. The parabolic reflectivity mirror was made with a profiled layer deposited on a transparent substrate. The experimental results show a smooth near-field beam intensity distribution and a narrow single-lobe far-field pattern. Output pulses of up to 150 mJ have been obtained with a 4-mm rod.

© 1987 Optical Society of America