Optical nonlinearity in thin films exposed to low-intensity light

Optical nonlinearity in semiconducting and insulating thin-film structures is studied by waveguide methods under self-action conditions at a light intensity less than 0.1 W/cm² and a wavelength of 630 nm. The optical properties vs. light intensity are similar for semiconducting and insulating films, multilayer thin-film structures, and semiconductor-doped glass films. It is demonstrated that the optical nonlinearity and the nonlinear optical constants depend on the interface condition.