Optical Quadratic Nonlinearity in Corona-Poled Glass Film Waveguides

Although there has been active research on the optical quadratic nonlinearity that appears in poled glass, its origin has not been clarified. There have been many reports on bulk glass but little research on poled glass thin film waveguides. Waveguide structures are important for future applications to optical IC devices, and clarifying the origin of the nonlinearity is very important. In this work we report experiments on phase-matched blue second-harmonic generation in a corona-poled Corning 7059 glass film waveguide with a titanium sapphire laser as a fundamental wave and investigate the origin of its nonlinearity. After relaxation of the nonlinearity optical constant once the poling has been measured, the analysis is performed using a biexponential function, and the origin is elucidated by separating the fast and the slow relaxation components. In particular, an etching experiment has been carried out noting the latter component, and it has been shown that the charge distribution generated in the waveguide by the poling and the interface between the glass film and glass substrate play important roles in generating quadratic nonlinearity. It has also been confirmed by X-ray photoelectron spectroscopy that sodium diffuses in Pyrex glass substrate as a result of poling.