Measurements of nonlinear properties on semiconductor-doped sol-gel films

The nonlinear properties have been investigated using the m-line technique. A laser beam is coupled into the waveguide through a grating obtained by ion milling on the substrate before the film deposition. The transmitted intensity is plotted against the incidence angle. At high intensities the m-line associated with the excitation of the guided mode is shifted and its shape is changed in respect to the low energy case. This allows to deduce the nonlinear coefficient through a calculation based on a nonlinear distributed coupler model. An OPO-laser pumped by the third harmonic of a seeded Nd:YAG laser was used as source.