Large-scale As-Sb-S chalcogenide glasses with ultrahigh gradient refractive index

• A six-layer spherical GRIN lens with a diameter of 40 mm was obtained from a series of As 40-x Sb x S 60 glasses and a record refractive index difference (Δ n ) of 0.33 (@2μm) could be achieved. • An unprecedented diffusion depth of 6,000 µm was obtained between the two pieces of As 40-x Sb x S 60 (0 ≤ x ≤ 30) glasses via an innovative high-temperature melting process. • The continuous refractive index gradient distribution in the order of millimeter greatly expanding the effective size of GRIN optical elements. • A valuable strategy is proposed to facilitate the realization large-scale IR GRIN lens. Gradient refractive index (GRIN) infrared lens provided additional degrees of freedom for correcting chromatic and spherical aberrations in optical design by combining an internally customized refractive index distribution with the surface curvature of optical elements. However, high-performance GRIN infrared lenses are still faced with multiple bottlenecks including complex processing processes, limited fabrication size, unsatisfying refractive index difference and inferior interface quality, which restrict their wide applications. In this study, a group of novel infrared lens with high plasticity and large refractive index difference were developed based on the As 40- x Sb x S 60 system. Planar and spherical infrared GRIN lenses were successfully fabricated using precision molding technology, with a maximum refractive index difference (Δ n ) of 0.33 at a wavelength of 2 μm. In addition, a maximum diffusion depth of 6000 μm between two pieces of glass was achieved using a high-temperature melt diffusion process. The successful preparation of large-scale Δ n GRIN optical lens with controllable size and shape provides a new solution for realizing high performance and lightweight infrared optical systems.