On the performance of a phase-unifying unstable resonator for excimer lasers

Abstract

The performance of a high-gain short-pulse XeCl laser fitted with an unstable cavity using a phase-unifying output coupler has been investigated. It is shown that high-mode-volume nearly diffraction limited laser beams can be extracted by properly tailoring the cavity parameters. In fact, the XeCl laser performance was strongly dependent on the percentage of HCl used in the laser mixture and then, on the laser gain. The sensitivity of the output beam parameters (energy, pulse-length and divergence) to mirror misalignment was relatively low. The misalignment angle of the phase-unifying mirror to decrease the normalized output energy by 50% was 4.4 mrad.