Temperature and wavelength dependence of the thermo-optical properties of tellurite and chalcogenide glasses

Abstract

The refractive index and the temperature coefficient of the optical path length change of tellurite (80TeO2:20Li2O) and chalcogenide glasses (72.5Ga2S3:27.5La2O3) were determined as a function of temperature (up to 150°C) and wavelength (in the range between 454 and 632.8nm). The tellurite glass exhibits the usual refractive index dispersion in the wavelength range analyzed, while anomalous refractive index dispersion was observed for the chalcogenide glass between 454 and 530nm. The dispersion parameters were determined by means of the single-effective oscillator model. In addition, a strong dependence of the temperature coefficient of the optical path length on the photon energy and temperature was found for the chalcogenide glass. The latter was correlated to the shift of the optical band gap (or electronic edge) with temperature, which was interpreted by the electron-phonon interaction model.