Negative-branch unstable resonator with a phase unifying output coupler for high power Nd:YAG lasers

Abstract

Large symmetrical near-diffraction-limited beams 6 mm in diameter with a divergence angle of 1.2 mrad have been extracted from a 0.6% doped Nd:YAG rod pumped by a Kr-arc lamp using a negative-branch unstable resonator with a phase-unifying output coupler. The slope efficiency was 2.6%, the maximum peak laser power was 300 W and the maximum average laser power was 23 W. The misalignment angle of the output coupler to decrease the laser powers by 20% was 2.75 mrad.