Generation of high-power blue light in periodically poled LiNbO_3

We report the generation of $450-\mathrm{mW}$ average blue ($473-\mathrm{nm}$) power by frequency doubling of a diode-pumped $946-\mathrm{nm}$ Nd:YAG laser. We achieved pulsed operation at a high repetition rate ($\sim 160 \mathrm{kHz}$) by driving the relaxation oscillations of the laser. A 40% conversion efficiency to the second harmonic was obtained in a single-pass, extracavity, first-order, quasi-phase-matched process in which periodically poled lithium niobate (period $4.5 \mathit{\mu }\mathrm{m}$, thickness $0.5 \mathrm{mm}$, and length $15 \mathrm{mm}$) at 140 °C was used. The resulting high-power blue beam was circular in profile and nearly diffraction limited, indicating that photorefractive effects do not appear to limit device performance.