m-lines technique application for studying of optical nonlinearities in thin films at a low light intensity

Abstract

In the range of a light intensity below 0:1 W/cm2 nonlinear optical properties of semiconductor and dielectric thin films are studied at a wavelength of 632.8 nm. Optical nonlinearity was investigated by the technique of the spatial Fourier spectroscopy of guided modes excited in these thin-film structures in the self-effect case. The nonlinear refractive index and the absorption coefficient were found to be about 10 3 cm2/W for semiconductor films and multilayer structures and about 10 6 cm2/W for quartz glass films. Origin of this optical nonlinearity is considered as a photo-induced modification of surface states in the optical band gap.