Impact of replacing Na⁺ with Ag⁺ on the optical and spectroscopic properties of Er³⁺-doped tellurite glasses

Abstract

Er3+ doped tellurite glasses have attracted significant interest due to their broad emission band at 1.5 µm, the telecommunication window. Among them, the glasses in the TeO2-ZnO-Na2O system are particularly suitable for waveguide fabrication using ion exchange. This study investigates the impact of substituting Na2O with Ag2O in the tellurite glass doped with Er3+ ions on its optical and spectroscopic properties, as well as its chemical durability when immersed in AgNO3-KNO3-NaNO3 molten salt baths, usually used for Ag+-Na+ exchange. The replacement of Na2O with Ag2O leads to an increase in thermal stability and refractive index due to the depolymerization of the glass network. When immersed in Ag-containing salt baths, the glass surface reacts with the molten salt bath, the reaction of which depends on the glass and molten salt bath composition. Diffusion of Ag+ and preferential etching of TeO2 can be obtained, as well as surface crystallization. The glass with the composition 80 TeO2 – 10 ZnO – 10 Na2O (in mol%) was found to be the most stable in the molten salt bath probably due to its polymerized network and so the most suitable glass for ion exchange processes and waveguide fabrication.