Optical Absorption and NIR Photoluminescence of Nd3+-Activated Strontium Phosphate Glasses

Strontium phosphate glasses with various concentrations of Nd2O3 have been prepared by melt quenching method. Absorption and photoluminescence spectra and lifetime measurements have been carried out to obtain the optical properties of these glasses. From the absorption spectrum, intensity and radiative parameters have been evaluated using Judd–Ofelt analysis. Near-infrared photoluminescence spectra consist of three bands centered at 875 nm, 1056 nm and 1327 nm, among which the highest intensity has been noticed for the band at 1056 nm that corresponds to the 4F3/2 → 4F11/2 transition of Nd3+ ion. Laser parameters such as branching ratio, band width, stimulated emission cross section and gain bandwidth for the 4F3/2 → 4F11/2 transition are found to be 0.52, 28 nm, 2.31 × 10−20 cm2 and 6.5 × 10−26 cm3, respectively. Decay curves of the 4F3/2 level of Nd3+ ions exhibit a single exponential nature at lower concentrations, while they become non-exponential at higher concentrations (≥ 0.1 mol.%) due to non-radiative energy transfer processes. This feature is also associated with shortening of lifetime from 307 μs to 82 μs when the Nd3+ ion concentration increases from 0.1 mol.% to 4.0 mol.%. The results have been compared with those of barium and magnesium phosphate glasses and commercial glasses. The results suggest that these glasses have potential applications as infrared laser materials at 1.05 μm.