Third-order optical nonlinearity in Ge-Se-Te chalcogenide glasses

Abstract

We have prepared GexSe10Te90-x glasses with a composition of x from 17.5 to 26.25 and measured their properties using various diagnosis tools. It was found that, all the glasses have a transmittance more than 40% at a wavelength range from 2 to 15 μm, and linear refractive index n0 decreases but optical bandgap energy Eg increases with decreasing Te contents in the glasses. We also analysed the evolution of n2 and β as a function of Ge content, both the evolution of n2 and β are close to the prediction by Sheik-Bahae et al. for optical nonlinearity of semiconductors. In all cases, the nonlinear optical refractive index n2 measured at 3.0 μm is larger than that at 2.5 μm due to the two-photon resonance effect, and a maximum nonlinear index is 2.46 × 10−13 cm2/W at composition of Ge17.5Se10Te72.5. Such larger nonlinearity around 10−13 cm2/W observed in the present paper is one order of the magnitude larger than that in S- and Se-based chalcogenide glasses, demonstrating potentials of Te-based glasses for the applications as mid- and far-infrared nonlinear optical devices.