Enhanced 1.80 μm fluorescence in Er3+/Yb3+/Tm3+ tri-doped tellurite glass for fiber lasers

Improving the lasing emission property of rare-earth doped vitreous material is a research topic. In this paper, Er3+/Yb3+/Tm3+ tri-doped tellurite glasses with and without WO3 component were synthesized using melt-quenching technique and the effect of WO3 addition on the 1.80 μm band fluorescence of Tm3+ was investigated. The obtained samples were characterized by X-ray diffraction (XRD) pattern, differential scanning calorimeter (DSC) curve, Raman spectrum, UV/Vis/NIR absorption spectrum, near-infrared emission spectrum and fluorescence decay curve. The XRD pattern confirmed amorphous structural nature of synthesized tellurite glass, the DSC curve revealed good thermal stability with ΔT>100 °C and the Raman spectrum displayed a stretching vibration band around 920 cm−1 for glass host with WO3. Under the excitation of 980 nm laser diode (LD), the intense 1.80 μm band fluorescence of Tm3+ originated from the 3F4→3H6 transition was observed in the Er3+/Yb3+/Tm3+ tri-doped tellurite glass and the intensity increases further with the addition of a certain amount of WO3, which is attributed to the enhanced energy transfers from Yb3+ (Er3+) to Tm3+ ions due to the increased phonon energy of glass host. The energy transfer mechanism between them was elucidated by analyzing fluorescence decay behavior of Tm3+ and quantitatively calculating energy transfer coefficient as well as phonon contribution ratio. Meanwhile, based on the absorption spectrum, some important spectroscopic parameters such as Judd-Ofelt parameter, spontaneous radiative transition probability, fluorescence branching ratio, absorption and emission cross-sections, and gain coefficient spectrum were calculated to reveal spectroscopic properties of doped Tm3+ ions. The obtained results indicate that Er3+/Yb3+/Tm3+ tri-doped tellurite glass with an appropriate amount of WO3 is a promising gain medium applied for the 1.80 μm band solid-state lasers.