A cw Nd:YAG laser was quasi-phase-matched frequency doubled by a bulk periodically poled flux-grown KTiOPO<sub>4</sub> crystal in an external resonant cavity. The conversion efficiency and the second-harmonic power with a pump of 225 mW were 55% and 123.5 mW, respectively. The loss of the 1-cm-long crystal, which operated near room temperature, was 1.3% and was dominated by scatter from the cleaved facets of the crystal. No damage, photorefractive or other, was observed at intensites of 370Wmm<sup>-2</sup> , but beam size had to be optimized to eliminate thermal-induced instabilities in the doubling cavity.
© 1998 Optical Society of America
A. Arie, G. Rosenman, A. Korenfeld, A. Skliar, M. Oron, M. Katz, and D. Eger, "Efficient resonant frequency doubling of a cw Nd:YAG laser in bulk periodically poled KTiOPO4," Opt. Lett. 23, 28-30 (1998)