The enhanced near-infrared fluorescence of Nd3+-doped tellurite glass

Tellurite glasses with different concentrations of Nd3+ ions and WO3 oxide were prepared using melt-quenching technique. The prepared glasses were characterized by the absorption spectrum, emission spectrum, Raman spectrum, fluorescence decay curve and DSC curve measurements, together with Judd-Ofelt intensity parameter, radiative transition probability and fluorescence branching ratio calculations to reveal the effects of Nd3+ and WO3 concentration on the structure, photo-luminescence and thermal stability. Under the excitation of 808 nm LD, three near-infrared band fluorescence emissions at around 0.9, 1.06 and 1.34 mu m, corresponding to the transitions from the F-4(3/2) -> I-4(9/2) -> I-4(11/3) and I-4(13/2) levels respectively, are observed, and the fluorescence intensities increase with the increase of doped Nd3+ concentration up to 0.6 mol%. Furthermore, the fluorescence intensities continue to increase greatly with the introduction of WO3 oxide. Compared with 0.6 mol% Nd3+-doped glass without WO3 oxide, the luminescent intensity of 1.06 mu m band increases by about 95% in the glass with 9 mol% amount of WO3, which is mainly attributed to the rapid population of Nd3+ ions in the excited level F-4(3/2) due to the enhanced multi-phonon relaxation process with the increased phonon energy of glass host. Therefore, the enhanced luminescent intensity as well as the good thermal stability demonstrated by DSC curve indicate that the prepared 0.6 mol% Nd3+-doped tellurite glass with 9 mol% amount of WO3 oxide is a potential gain medium applied for near-infrared band solid-state lasers and fiber amplifiers.