Phase-matched second-harmonic generation in a Ta2O5/KTiOPO4 waveguide

Highly efficient phase-matched second-harmonic generation (TEω00-like mode to TE2ω10-like mode) using waveguide modal dispersions is reported. The waveguide is composed of a KTiOPO4 substrate, a Ta2O5 thin-film core, and a SiO2 clad in the strip-loaded configuration. Normalized conversion efficiency of around 1000%/W cm2 and the blue (413 nm) second-harmonic power of 13 mW were achieved with a 4.1-mm-long waveguide. The output beam of the second-harmonic wave showed a single-peak power profile, in spite of being first-order mode in the film thickness directions.