Sulfide glasses based on GeGaS are stabilized by the addition of a fourth element: antimony. They show very weak crystallization upon heating as compared to standard GeGaS glass. Because of the low phonon energy inherent in sulfide glasses, the 1.3 micrometers emission of Dy3+ ions can be observed. This transition is characterized in terms of emission cross-section and quantum efficiency. Refractive indices are measured for various concentrations of cesium halides in standard GeGaS glass.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.