LASER-DIODE-PUMPED PHASE-LOCKED ND-YAG LASER ARRAYS

Scaling of an efficient and compact diode-end-pumped Nd:YAG laser was demonstrated by two-dimensional phase-locked arrays. The arrays of stable resonators were formed by multiple thermal lenses induced by the simultaneous end-pumping of laser-diode-coupled fibers. Because of partial overlap of each transverse mode, the output was phase locked. Various configurations of pumping fibers were tested to study phase locking. It was found that minimization of the coherently coupled intensity between adjacent array elements gave good prediction for phase difference between modes. When the plane parallel cavity as long as 30 mm was pumped by 2 x 2 laser diode coupled fibers, phase-locked 1.8 W continuous wave 1.06-mu-m output was obtained with 55% slope efficiency. 1.2 W single longitudinal mode output with single lobe beam profile was obtained by using a spatial phase filter and the twisted mode method.