31%-efficient blue second-harmonic generation in a periodically poled MgO:LiNbO_3 waveguide by frequency doubling of an AlGaAs laser diode

We present a method of controlling the shape of the domain-inverted structure in an off-cut $\mathrm{MgO}:{\mathrm{LiNbO}}_3$ crystal by utilizing a two-dimensional high-voltage application. With this technique a periodically domain-inverted structure with a period of $3.2 \mathit{\mu }\mathrm{m}$ and a thickness of $2.0 \mathit{\mu }\mathrm{m}$ was fabricated over a 10-mm interaction length. This structure has made possible sufficient overlaps between propagation modes and domain inversion in the waveguide. Using this structure, we demonstrated cw blue second-harmonic generation of 17.3 mW of power at a wavelength of 426 nm with single-pass 55-mW cw AlGaAs laser diode input, which corresponded to 31% power-conversion efficiency.