The spectroscopic properties of Er3+-doped TeO2-Nb2O5 glasses with high mechanical strength performance

(100 − x)TeO2 − xNb2O5 (x = 5-20) niobic tellurite glasses doped with 0.5 mol.% Er2O3 were synthesized, and their thermal, mechanical, and spectroscopic properties were measured and compared to the properties of the typical 75TeO2-20ZnO-5Na2O (TZN) tellurite glass. The refractive index (nd), density (ρ), and glass transition temperature (Tg) of bulk glasses increase with the Nb2O5 content. The Vickers microhardness (Hv) of bulk glass in niobic tellurite glasses also increases with the Nb2O5 content. The values (2.5-3.2 GPa) of Hv in the niobic tellurite glasses are 47-88% larger than that (1.7 GPa) in TZN glass. The effect of Nb2O5 content on absorption spectra, the Judd-Ofelt parameters Ωt (t = 2, 4, 6), fluorescence spectra and the lifetimes of Er3+:I13/2 level were also investigated, and the stimulated emission cross-section was calculated from McCumber theory. With increasing Nb2O5 content in the glass composition, the Ωt (t = 2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) of I13/2 of Er3+ increase, while the 4I13/2 lifetimes of Er3+ decreases. Compared with TZN glass, the gain bandwidth properties of Er3+-doped TeO2-Nb2O5 glass is much larger than in tellurite glass based TeO2-ZnO-Na2O system, bismush-based glass, germanate, and silicate glasses, which indicates that TeO2-Nb2O5 glasses are better choice as a practical available host material for broadband Er3+-doped amplifier.