High conversion efficiency single-pass second harmonic generation in a zinc-diffused periodically poled lithium niobate waveguide

We report a modified technique for the fabrication of zinc-diffused channel waveguides using z-cut electric-field periodically poled LiNbO3. Unlike previous work, the diffusion was carried out using metallic zinc at atmospheric pressure. By optimizing the thermal diffusion parameters, channel waveguides that preserve the existing periodically poled domain structures, support both TE and TM modes, and enhance photorefractive damage resistance were obtained. Nonlinear characterisation of the channel waveguides was investigated via second harmonic generation of a 1552nm laser with a maximum conversion efficiency of 59%W-1.cm-2 at 14.6oC. Using a pulsed source a second harmonic conversion efficiency of 81% was achieved.