Alkali halides such as KBr, KI, CsBr, and CsI were added to Dy3+-doped Ge–Ga–S glasses, and their effects on the 1.31-μm emission property were investigated. The intensities of the 1.31-μm emission (6F11/2 · 6H9/2 → 6H15/2) increased at the expense of the 1.75-μm emission intensity (6H11/2 → 6H15/2) with the alkali halide addition. The lifetimes of the 1.31-μm emission level also increased as much as 35 times from 38 μs for Ge–Ga–S glass to 1320 μs for the glass containing 10 mol% CsBr. These enhancements occurred only when the ratio of MX (M = K, Cs; X = Br, I)/Ga was equal to or larger than unity. Raman spectra of Ge–Ga–S–CsBr glasses indicated the formation of [GaS3/2Br]− complexes, which provide the preferred sites for Dy3+. Due to this new local environment of Dy3+, the multiphonon relaxation rates from the Dy3+:6F11/2 · 6H9/2 level decreased by approximately four orders of magnitude. The enhancement in the 1.31-μm emission properties with alkali halide addition supports the potentials of these glasses as hosts for the Dy3+-doped fiber-optic amplifiers.

Fluorescence emissions at both 1.31 and 1.55 m communication windows were observed from Pr 3؉ /Er 3؉ codoped Ge-AsGa-S glasses with a single wavelength pumping at 986 nm. The lifetime of the Er 3؉ : 4 I 11/2 level decreased as the Pr 3؉ concentration increased, and that of the Pr 3؉ : 1 G 4 level increased as the Er 3؉ concentration increased. Energy transfer from the Er 3؉ : 4 I 11/2 level to the Pr 3؉ : 1 G 4 level was responsible for emission of the 1.31 m fluorescence from the Pr 3؉ : 1 G 4 level. Ge-As-Ga-S glasses that have been doped with Pr 3؉ and Er 3؉ cations are promising amplifier materials for both 1.31 and 1.55 m communication windows.

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