Efficient direct diode-laser frequency doubling in quasi-phase-matched LiNbO(3) waveguides.

We report efficient (22%/W) blue-light generation by direct diode-laser frequency doubling in second-order quasi-phase-matched LiNbO(3) channel waveguides. We address several critical issues of direct diode-laser doubling, which include input coupling, phase-matching bandwidth, and, in particular, the effect of the spectral mode structure of a high-power diode laser on the frequency-conversion efficiency.