GeS2-Ga2S3-AgI glasses with high nonlinear optical properties

We report on the study of nonlinear optical properties of AgI-doped chalcogenide glasses based on Ge-Ga-S and their possible relation to the structural changes caused by the presence of AgI in the base glass structure. The nonlinear optical response of the glasses has been measured using 35 ps, 1064 nm laser pulses and the corresponding nonlinear absorption, refraction and third-order susceptibility χ⁽³⁾ have been determined. They were found to increase dramatically with AgI concentration, resulting in very strong enhancement of the third-order nonlinear response. Analysis of reduced isotropic Raman spectra revealed that structural changes take place upon adding Ga₂S₃ in the GeS₂ glass structure. Further alloying the Ge-Ga-S glass with AgI causes subtle structural changes assigned to the formation of mixed chalcohalide species which are presumably related to the huge increase of the third-order susceptibility χ⁽³⁾.