Gradient refractive index chalcogenide lens for lightweight infrared dual-band imaging systems

In this study, we report the development of Ge₁₅Se_85-xTe_x (GSTx) chalcogenide glass-based gradient refractive index (GRIN) lenses for lightweight dual-band infrared imaging systems. The GSTx glasses exhibit compatible thermal properties (ΔT_g < 9 °C), significant refractive index contrast (Δn > 0.27), and high transmittance (> 57%). Through systematic dispersion characterization of GSTx glasses, we identify the GST0/GST25 pair as optimal glass sheets. The refractive index profile of the GRIN glass was quantitatively characterized by correlating Raman peak intensity ratios (Ge-Se/Se-Se bond vibrations) with the number of chemical bonds within the glass. Compared to a 4-element homogeneous system, the GRIN-incorporated design achieves 21.4% length reduction and 84.9% weight reduction. Providing a new full-chain solution for lightweight dual-band infrared imaging systems.