Adjustment of refractive index of Ge-Ga-Se glass via Te addition for infrared-imaging applications

After assessing compositional dependence of thermal and optical properties of Ge-Ga-Se glasses, we introduce Te, via replacing Se, into Ge25Ga5Se70 and Ge35Ga5Se60 (mol%) glasses in an attempt to enhance their refractive index. In the case of Se-deficient Ge35Ga5Se60 composition, vitrification is achieved for Te content up to 20 mol%. In the case of Se-sufficient Ge25Ga5Se70 composition, however, formation of bulk glass is realized only when Te content ranges from 25 to 45 mol%. Being proportional to Te content, refractive index of Ge25Ga5Se30Te40 glass is measured to approach 2.855 at 10 μm, which is far superior to that of any commercialized selenide glasses for infrared-imaging applications. This compositionally tailored Ge25Ga5Se30Te40 glass is further verified to be compatible with the conventional precision glass molding process, and infrared-imaging performance of the resulting molded lens is as excellent as the existing selenide-glass-based lenses.