High-power hundred-nanosecond 532  nm laser employing a dual-rod configuration for cavity length extension and conjugate compensation

A nanosecond-long-pulse, high-beam-quality, high-power 532 nm laser was developed by employing two serially cascaded Nd:YAG modules with a 0.8% doping concentration, positioned at optically conjugate planes for thermal lens compensation. The laser employed single acousto-optic Q-switching to generate the fundamental pulsed output and intracavity second-harmonic generation (SHG) to obtain a 532 nm laser output. Through the integration of beam propagation theory and experimental validation, an optimized resonator configuration was devised. The laser produced an average output power of 85.24 W at 532 nm under a repetition rate of 14.5 kHz, corresponding to a second-harmonic conversion efficiency of 65.3%. The generated green pulses exhibited a pulse duration of 133.5 ns. The beam quality factors of the 532 nm laser were measured to be <i>M</i><i>x</i>2=9.05 and <i>M</i><i>y</i>2=9.29, respectively, while a root-mean-square (RMS) power fluctuation was 0.74% over 2 h. Subsequently, the stable 532 nm laser beam was coupled into an optical fiber with a core diameter of 200 µm and a numerical aperture (NA) of 0.06. This configuration yielded an average output power of 77.66 W, corresponding to a coupling efficiency of 91.1%.