Type-II second-harmonic generation and sum-frequency mixing in uniform KTiOPO₄ channel waveguides

Type-II second-harmonic generation was investigated in channel waveguides fabricated in potassium titanyl phosphate (KTiOPO4) crystals by ion exchange. The birefringence of the guided-wave structure was used to provide phasematching. A green (509 nm) output power of 0.25 mW was produced by frequency doubling the 1018-nm output of a titanium laser; this power is 200 times greater than what would be obtained in the corresponding bulk interaction. Phasematching for second-harmonic generation was found to have broad tolerances with respect to temperature and wavelength. Blue light at 483 nm was produced by sum-frequency mixing of 1064-nm and 883-nm light.