New sulfo-bromide glasses of the (60-x)GaS3/2·xGaBr3·10GeS2 ·30LnS3/2 composition (Ln=La and Er
x=0, 5, 10, 15 and 20) were prepared. Their thermal and optical properties were measured. The bromide-modified glasses exhibited more prominent thermal stability than sulfide glasses of the 60GaS3/2·10GeS2·30LnS3/2 composition (GGLS). As bromides were added to the GGLS glass, the color of the glass changes from red-orange for GGLS glass to pale yellow for bromide-modified sulfide glasses, and consequently the band gaps shifted to shorter wavelengths. As a result, the Er3+ green up-conversion luminescence intensities at around 525 and 550 nm in the bromide-modified glasses became stronger compared with those in pure GGLS glasses. © 2001 Elsevier Science B.V. All rights reserved.