Thermal diffusion preparation and rebonding behavior of Ge20Se80-xTex infrared gradient glass

Gradient refractive index materials (GRINs) are rapidly evolving in optical achromats and compact imaging systems. And GRINs with multi-band imaging mean higher integration for advanced optical imaging systems. In this paper, GRINs covering mid-wave infrared (MWIR) and long-wave infrared (LWIR) were prepared by thermal diffusion method based on Ge20Se80-xTex glasses. Similar glass transition temperatures (ΔTg = 1 °C) and coefficients of thermal expansion (ΔCTE = 5.47 ppm/K) permit efficient bonding and diffusion processes between the glasses. The GRINs were visualized by infrared imagers, and the axial diffusion results were accurately characterized by Raman spectroscopy and energy dispersive spectrometer (EDS). The refractive index difference (Δn) of the GRINs reaches 0.23 and the diffusion depth reaches 3.53 mm. Diffusion coefficients and activation energy were calculated and discussed. Dispersion property is initially evaluated by Abbe number and partial dispersion.