Preparation of infrared axial gradient refractive index lens based on powder stacking and the sintering thermal diffusion method

Abstract

The gradient refractive index (GRIN) lens is widely used in the visible band, but it is still elusive in the infrared band. In this paper, we propose a new method of fabricating chalcogenide GRIN by spark plasma sintering (SPS) technology based on powder stacking and sintering thermal diffusion. We replaced Se in Ge11.5As24Se64.5 glass with S and prepared several Ge11.5As24Se(64.5-x)Sx glasses as infrared transmission GRIN materials. The maximum refractive index difference (Δn) of the matrix glass is 0.18. The effects of heat treatment temperature and time on diffusion depth and concentration-dependent thermal diffusion coefficient were investigated. The diffusion depth of 100 µm was demonstrated under the condition of 400 °C-48 h by this method. The thickness of the glass layer can be well controlled by powder stacking. The obtained GRIN glass is highly transparent in the near- and mid-infrared wavelength region.