Radial Gradient Refractive Index (GRIN) infrared lens based on spatially resolved crystallization of chalcogenide glass

While widely used in the visible, radial gradient refractive index (GRIN) lenses are still elusive in the IR waveband. In this paper we introduce a new method based on spatially resolved crystallization of chalcogenide glass to produce such lenses. Optical and structural properties of 80 GeSe2-20 Ga2Se3 glass ceramic samples are measured. A shift of refractive index is induced by increasing the density of nanocrystals. By placing the sample into a tailored thermal profile, spatially controlled crystallization is achieved. To our knowledge this constitutes the first fabrication of an optically functional radial GRIN in the IR. We also introduce a method to characterize the index profile non-destructively, which is a necessary step for embedding GRIN into commercial systems. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement