Effect of Al₂O₃ and La₂O₃ on structure and spectroscopic properties of Nd-doped sol–gel silica glasses

Nd³⁺-doped sol-gel silica glasses with enhanced spectroscopic properties via co-doped Al₂O₃ and La₂O₃ are reported. Co-doped Al₂O₃ and La₂O₃ not only significantly increases the fluorescence intensity and prolongs the fluorescence lifetimes of Nd³⁺, but also has a large σ_ems × τ_f of the Nd-doped sol-gel silica glasses. The Judd–Ofelt parameters were evaluated from the absorption spectrum of Nd³⁺-doped glass, and these were used to predict the effects of various Al₂O₃ and La₂O₃ contents. The structures resulting from co-doping Al³⁺, La³⁺, and Nd³⁺ ions in silica glass were analyzed by using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). It showed that La₂O₃ could change the chemical environment of Nd³⁺ ion and depolymerize the silica glass network. These results suggest that La/Al/Nd co-doped silica glass is a potentially useful material for developing optical devices and an ideal choice for lasers.