The spectroscopic properties of Er 3+-doped TeO 2–Nb 2O 5 glasses with high mechanical strength performance

Abstract

(100 − x)TeO 2 − xNb 2O 5 ( x = 5–20) niobic tellurite glasses doped with 0.5 mol.% Er 2O 3 were synthesized, and their thermal, mechanical, and spectroscopic properties were measured and compared to the properties of the typical 75TeO 2–20ZnO–5Na 2O (TZN) tellurite glass. The refractive index ( n d), density ( ρ), and glass transition temperature ( T g) of bulk glasses increase with the Nb 2O 5 content. The Vickers microhardness ( H v) of bulk glass in niobic tellurite glasses also increases with the Nb 2O 5 content. The values (2.5–3.2 GPa) of H v in the niobic tellurite glasses are 47–88% larger than that (1.7 GPa) in TZN glass. The effect of Nb 2O 5 content on absorption spectra, the Judd–Ofelt parameters Ω t ( t = 2, 4, 6), fluorescence spectra and the lifetimes of Er 3+:I 13/2 level were also investigated, and the stimulated emission cross-section was calculated from McCumber theory. With increasing Nb 2O 5 content in the glass composition, the Ω t ( t = 2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) of I 13/2 of Er 3+ increase, while the 4I 13/2 lifetimes of Er 3+ decreases. Compared with TZN glass, the gain bandwidth properties of Er 3+-doped TeO 2–Nb 2O 5 glass is much larger than in tellurite glass based TeO 2–ZnO–Na 2O system, bismush-based glass, germanate, and silicate glasses, which indicates that TeO 2–Nb 2O 5 glasses are better choice as a practical available host material for broadband Er 3+-doped amplifier.