Buried annealed proton-exchanged waveguide in periodically-poled MgO:LiTaO₃ fabricated by surface activated bonding for high-power wavelength conversion

Watt-class UV laser lights with symmetric spatial modes are suitable for high-resolution industrial applications. Channel waveguides with a guided mode of several ten microns diameter in MgO:LiTaO 3 enhance integration capability while avoiding photorefractive damages during high-power wavelength conversion. We focused on buried waveguides fabricated by proton exchange, surface-activated bonding (SAB), and proton diffusion processes in periodically-poled (PP) MgO:LiTaO 3 . In this work, the mode profiles were simulated using the proton diffusion coefficients estimated by secondary ion mass spectrometry. Using the simulation results, the buried waveguides with a mode diameter larger than 30 μ m were fabricated. By adopting designed PP structures, second harmonic generation (SHG) devices at a wavelength of 532 nm were fabricated. The nonlinear coupling coefficient was estimated to be 0.15 W −1/2 cm −1 . Compared to the conventional annealed proton-exchanged waveguide SHG device without SAB, symmetric guided modes were obtained while maintaining the nonlinear coupling coefficient.