Enlargement of mode size in annealed proton-exchanged periodically-poled MgO doped stoichiometric LiTaO3 waveguide for high power second harmonic generation

Abstract

Abstract Watt-class wavelength conversion is expected by enlarging the mode size of the channel waveguides to dozens of micrometers to avoid optical damage with high-power pump lasers. In this work, uniform periodically-poled (PP) structures in MgO doped stoichiometric LiTaO3 were fabricated by applying voltage with a SiO2 insulation layer. Annealed proton-exchanged waveguides with a full width at 1/e 2 maximum in a width of 43 μm with an in-depth of 28 μm were obtained by proton exchanging for 4 h and thermal diffusion for 75 h. This waveguide can be excited by pump waves with a power of 8.6 W considering the optical damage threshold. Second harmonic generation with a wavelength of 515 nm was conducted in the low power region of about 35 mW to investigate the basic characteristics. Normalized wavelength conversion efficiency in the 15 mm long PP structures was estimated to be 4.3% W−1.