Effect of annealing and dopants concentration on the optical properties of Nd³⁺:Al³⁺ co-doped sol–gel silica glass

Nd³⁺ in SiO₂ glass samples co-doped with aluminum at different concentrations have been synthesized by a sol–gel method. The effect of annealing temperature and concentration of dopants on the optical properties of the samples were investigated. Red-shift in absorption peaks was observed with annealing. Judd–Ofelt analysis shows the change in local environment of the Nd³⁺ ions with heat treatment. The fluorescence intensity of peaks at 880 nm and 1060 nm which result from the ⁴F_3/2 →⁴I_9/2 and ⁴I_11/2 states increased significantly with increase in annealing temperature as well as aluminum concentration. - Highlights: • Red-shift in absorption peaks observed after annealing due to nephelauxetic effect. • The Judd–Ofelt parameter Ω₂ increased and Ω₆ decreased with annealing. • PL intensity increases with annealing. • PL intensity increases with increasing Al content. • Nd³⁺ ion environment more diverse for higher Al content.