Chalcogenide glass thin-film optics for infrared applications

Chalcogenide glasses are increasingly used in infrared-transparent optical systems for space applications due to their relatively low density (compared to Ge or ZnSe), tunable spectral and thermo-mechanical properties, and molding capability. Remaining challenges include their application to thin-film optics and coatings. The high refractive indices of chalcogenide glasses (n > 2.7) suggest the possibility for high reflecting coatings based on few periods of alternating layers with high index contrast. As2Se3 thin film deposited by thermal evaporation is investigated using ellipsometry which show optical properties consistent with bulk material. Also we demonstrate a novel method for fabrication of antireflection coating using porous chalcogenide. Possibility of negligible extinction coefficient and low refractive index of this porous coating promises broadband suppression of undesired Fresnel reflections at the interface from infrared optics.