In this paper, the influence on optical properties of alkali halides such as CsCI in a covalent glassy matrix has been investigated. Chalcogenide glasses belonging to the (GeS 2 )-(Ga 2 S 3 )-CsCI system with high ratio of CsCI present an entire transparency in the visible range. These glasses maintain good transmission up to 12pm. Furthermore, the thermo-mechanical properties and the glass hygroscopicity have been investigated as function of the CsCI amount. This new generation of glasses presents a great interest for optical application. They could be used both for passive applications (multi-spectral imaging) and active applications for rare-earth doping due to their good transmission in the visible range, increasing optical pumping possibilities.