Energy transfer induced 2.0 µm luminescent enhancement in Ho3+/Yb3+/Ce3+ tri-doped tellurite glass

Tellurite glasses doped with Ho3+, Ho3+/Yb3+ and Ho3+/Yb3+/Ce3+ ions have been prepared using conventional melt-quenching method, and characterized respectively by the X-ray diffraction (XRD) pattern, differential scanning calorimeter (DSC) curve, UV-vis-IR absorption spectrum, upconversion spectrum, fluorescence spectrum and fluorescence decay curve to investigate the 2.0 µm band spectroscopic properties of Ho3+, thermal stability and structural nature of glass hosts. Under the excitation of 980 nm laser diode (LD), an intense and broad 2.0 µm band infrared emission originated from the 5I7 → 5I8 transition of Ho3+ was observed in the Ho3+/Yb3+ co-doped tellurite glass and increased further with the addition of Ce3+, which is attributed to the energy transfer (ET) from Yb3+ to Ho3+ as well as the cross-relaxation (CR) between Ho3+ and Ce3+. The quantitative analyses of ET mechanism between the doped rare-earth ions, together with the investigation on the changes of upconversion emission intensity and 2.0 µm fluorescence lifetime with Ce3+ were presented to elucidate the observed 2.0 µm band luminescent enhancement. Meanwhile, important spectroscopic parameters, such as radiative transition probability, absorption and emission cross-sections, and gain coefficient for Ho3+:5I7 → 5I8 transition, were calculated from the measured absorption spectrum to evaluate the potential radiative properties. Additionally, the measured DSC curve reveals the good thermal stability and the XRD pattern confirmed the amorphous structure of prepared glass host. The results indicate that Ho3+/Yb3+/Ce3+ tri-doped tellurite glass is a potential active medium for developing 2.0 µm band infrared solid lasers.