On the super-Gaussian unstable resonators for high-gain short-pulse laser media

High-mode-volume, high-energy (70-mJ), high-brightness (1.6*10/sup 14/ W cm/sup -2/ Sr/sup -1/) laser beams have been extracted from a high-gain short-pulse XeCl laser with a super-Gaussian unstable resonator. These results are obtained by increasing the cavity magnification factor to 6.6 and the output mirror peak reflectivity to 78%. The output beam divergence is seen to decrease from an initial value of approximately 0.2 mrad down to nearly diffraction limited after 6 ns for the short gain build-up time of the active medium. >