Optical properties of free arsenic and broadband infrared chalcogenide glass

The very large glass forming system, GeSe2–Ga2Se3–CsI, has been recently investigated. The 72GeSe2–18Ga2Se3–10CsI glass composition, which is a stable composition against crystallization and presents good chemical durability, has been selected for different optical measurements. This free-arsenic glass is slightly transparent in the visible up to 12 μm, allowing a great range of applications in thermal imaging. The refractive index has been measured as function of wavelength in the 2–12 μm infrared range at room temperature and the thermo refractive index dn/dT has been determined at 1310 and 1532 nm. Furthermore, the possibility to shape this glass composition by thermal molding without crystallization effect is demonstrated. Also antireflection coating has been optimized for this glass and 97% of average transmission from 8 to 11.5 μm has been achieved.