Single-axial-mode operation of a polarization-coupled stable/unstable-resonator Nd:YAG laser oscillator

We report reliable single-axial-mode (SAM) operation (100 mJ at 1064 nm) of a flash-pumped
Q
-switched polarization-coupled "diffraction-stabilized" Nd:YAG laser oscillator and describe the system, together with a technique for obtaining considerable temporal smoothing of the output waveform at higher energy (200 mJ) without spectral narrowing. A subresonator is crucial to both schemes.