Super-Gaussian reflectivity unstable resonator for excimer lasers

High-mode-volume, good optical quality laser beams of 55 mJ, of 19 ns duration and with a brightness of 3×1013 W cm−2 Sr−1, have been extracted from a high-gain, short-pulse XeCl laser, with an unstable resonator using a super-Gaussian reflectivity mirror. The misalignment angle of the output coupler to decrease the normalized output energy by 20% was 3.5 mrad.