Nonlinear optical properties of chalcogenide glasses at telecommunication wavelength using nonlinear imaging technique

Infrared chalcogenide glasses are studied with respect to their nonlinear optical properties. These glasses are transparent from the end of the visible region to wavelengths above 10 μm depending on the composition. Using a quarter-wavelength phase object at the entry of a 4f coherent imaging system, we show that it is possible to characterize the value of the nonlinear refractive index of materials placed in the Fourier plane of the setup. Experimental and simulated images are presented in order to validate our approach. We report that the use of a dephasing object maximizes the transmission variations in the detected image and increases significantly the sensitivity of the measurement compared to top-hat beams (by a factor of 6). Moreover, by adding this type of object at the entry of our imaging system it is possible to determine the sign of the refractive nonlinearity. Different chalcogenide bulk glasses are characterized in the picosecond domain at 1.06 μm and 1.55 μm. Refractive nonlinearity three orders of magnitude above the nonlinearity of silica glass is obtained.