Around 2 μm fluorescence and energy transfer in Tm3 +/Ho3 + co-doped tellurite glass

In this work, the near-infrared photoluminescence properties in Tm3 +/Ho3 + co-doped tellurite glass was investigated. The tellurite glass with composition TeO2-ZnO-Na2O-La2O3 was synthesized using conventional melt-quenching technique and characterized by UV/Vis/NIR absorption and near-infrared emission spectroscopies, fluorescence decay measurement and differential scanning calorimeter (DSC) analysis. Under the excitation of 808 nm laser diode (LD), a broadband 2.0 μm band luminescence ranging from 1600 to 2200 nm with a full width at half maximum (FWHM) of 362 nm was observed, which was contributed by 1.85 μm fluorescence from Tm3 +: 3F4 → 3H6 and 2.05 μm fluorescence from Ho3 +: 5I7 → 5I8. The fluorescence emission of Ho3 + was originated from the energy transfer from Tm3 + to Ho3 + ions, and the energy transfer mechanism was elucidated by analyzing fluorescence decay behavior of Tm3 + and quantitative calculation of phonon contribution joined in the energy transfer process. Meanwhile, based on the absorption spectrum, some important spectroscopic parameters such as Judd-Ofelt intensity parameter, spontaneous radiative transition probability, fluorescence branching ratio, absorption and emission cross-sections, and gain coefficient spectrum were calculated to reveal the spectroscopic properties of doped tellurite glass. Furthermore, from the DSC curve it can be derived that the investigated glass possesses a good thermal stability with ΔT(= Tx − Tg) larger than 152 °C. These results indicate that Tm3 +/Ho3 + co-doped tellurite glass could be a promising gain medium applied for  2.0 μm near-infrared band broad fiber amplifiers and tunable fiber lasers.