Nonlinear optical properties of glasses in the system Ge/Ga-Sb-S/Se

We report n2 measurements of selected chalcogenide glasses using a modified Z-scan technique. Measurements were made with picosecond pulses emitted by a 10 Hz Q-switched, mode-locked Nd:YAG laser at 1064 nm under conditions suitable to characterize ultrafast nonlinearities. The nonlinear index increases significantly up to 246 times the n2 for fused silica with an increase of SbS3 units and also very slightly with the replacement of Ge by Ga or S by Se. We have attributed the variation of n2 to the total number of electronic lone pairs and to the position of the absorption band gap, which are induced by the presence of GaS4 units or Se-Se bonds in the glass structure.