Optical Waveguide SHG Devices Using LiNbO₃ Epitaxial Grown and Ultraprecision Machining Technique

Abstract

Quasi-phase-matched second-harmonic generation (QPM-SHG) devices using LiNbO₃ optical waveguides show great potential as low noise and high beam quality blue-violet light sources applicable for high-density optical disks. Optical waveguides with a step index profile are desired for achieving strong confinement and sufficient overlap between the propagation modes in order to realize a high conversion efficiency. Liquid phase epitaxy of LiNbO₃ is a novel technique which yields a step index thin-film waveguide structure by doping ZnO in the film. Ultraprecision machining is a powerful technique for processing three-dimensional optical waveguides. The maximum SHG power of 50 mW at 425 nm wavelength was obtained using a ridgetype waveguide device which was fabricated from a periodically domain-inverted MgO: LiNbO₃ crystal by ultraprecision machining.