Correlation between the nonlinear refractive index and structure of germanium-based chalcogenide glasses

The nonlinear refractive index (n2) of new germanium-based sulfo-selenide glasses has been measured at 1064 nm using Z-scan technique, with picosecond pulses emitted by a 10 Hz Q-switched mode-locked Nd:Yag laser. We have determined the impact of the progressive replacement of S by Se on the nonlinear properties of these glasses. The value of n2 strongly increases with the substitution of S by Se, up to 350 times the n2 for fused silica. X-ray photoelectron spectroscopy (XPS) indicates that the increase of Ge–Se bond units in the glass network is responsible for the increase of n2. The suitability of these glasses for optical switching at telecommunication wavelengths based on such nonlinear properties has been also confirmed.