Electro-optical characterization of Ge–Se–Te glasses

Chalcogenide bulk glasses Ge20Se80−xTex for xϵ(0,15) have been prepared by systematic replacement of Se by Te. Selected glasses have been doped with Ho, Er and Pr, and samples have been characterized by transmission spectroscopy, measurements of dc electrical conductivity and low-temperature photoluminescence. Absorption coefficients have been derived from measured transmittance and estimated reflectance. Arrhenius plots of dc electrical conductivity, in the measured temperature range 300–460 K, are characterized by single activation energies roughly equal to the half of the optical gap. Activation energies deduced from Arrhenius plots reveal a systematic decrease with increasing Te content. Similarly, both absorption and low-temperature photoluminescence spectra reveal shifts of absorption edge and/or dominant luminescence band to longer wavelength due to Te → Se substitution. Samples doped with Ho and Er exhibit a strong luminescence at 1200 and 1540 nm due to 5I6 → 5I8 and 4I13/2 → 4I15/2 transitions of Ho3+ and Er3+ ions, respectively. Pr doped samples exhibit only a relatively weak luminescence peak at 1590 nm, which we tentatively assign to 3F3 → 3H4 transition of Pr3+ ions. Absorption of the base glass luminescence at 1460 and 1520 nm has been observed at low temperature on samples doped with Pr and Er, respectively.