Customized linear refractive index GRIN prepared by rapid sintering of multilayer chalcogenide glass powders

Abstract Gradient refractive index (GRIN) lenses have recently become a hot topic in compact imaging and achromaticity. Current research focuses on exploiting GRIN materials and upgrading the preparation technology. In this study, infrared (IR) GRIN materials were successfully prepared by spark plasma sintering of multilayer chalcogenide glass (ChGs) powders. ChGs powders were derived from the Ge 20 Se 80‐x Te x series glasses ( x = 0–28 mol%) with a maximum refractive index difference (Δ n ) of 0.25. The similar glass transition temperatures (Δ T g < 10°C) promote efficient sintering of multilayer powders. Six‐, eight‐, and ten‐layer powders of different compositions were rapidly sintered with a thickness of 600, 300, and 200 µm per layer, respectively. Such tiny layer thickness enables the GRIN materials to exhibit nearly linear refractive index variation. Energy dispersive spectroscopy line scans well characterized the gradient variation of GRIN. The maximum deviation of the refractive index gradient from the fitted target line was only ± 0.016 for the 10‐layer GRIN. The sintered GRIN shows excellent IR transparency, which is of great interest for mid‐wave and long‐wave infrared imaging.