Optical nonlinearity in glasses: the origin and photo-excitation effects

Linear and nonlinear optical properties in oxide and chalcogenide glasses have been studied comparatively. Applying a semiconductor concept to these glasses, we show that maximal nonlinear refractive-index at optical communication wavelengths is similar to 10(-4) cm(2)/GW, which can be obtained in materials with bandgap energy of similar to 1.6 eV. It is also shown for SiO2 and As2S3 that linear and nonlinear optical excitations induce different photostructural changes, which are attributable to different photo-electronic transition probabilities.