Efficient quasi-phase-matched frequency doubling with phase compensation by a wedged crystal in a standing-wave external cavity

In standing-wave enhancement cavities for frequency doubling, second-harmon ic fields are generated in both directions of propagation. To add the field s coherently, one should compensate for the phase shifts introduced by disp ersive elements in the cavity. We experimentally demonstrate phase compensa tion in a compact standing-wave frequency-doubling cavity by use of a wedge d periodically poled KTP crystal. The highest conversion efficiency and sec ond-harmonic power obtained by pumping with a 1064-nm cw Nd:YAG laser were 69.4% and 268 mW, respectively. (C) 1999 Optical Society of America.