Optical transition properties, energy transfer upconversion luminescence, and temperature-sensing characteristics of Tm3+/Yb3+ Co-doped oxyfluoride tellurite glass

The optical transition properties of Tm3+ in oxyfluoride tellurite glass were determined by the Judd–Ofelt theory. The radiative transition rates, fluorescence branching ratios, and intrinsic lifetime for interesting transitions or level were obtained. The optimum doping concentration of Tm3+ for sample was examined, and the optimal concentration for upconversion luminescence was 0.1% Tm2O3. The main reason for concentration quenching was nonradiative energy transfer through the cross-relaxation mechanism. In addition, two-photon processes for near-infrared 3H4→3H6 emission and three-photon processes for blue 1G4→3H6 emission of Tm3+ were confirmed by analyzing the dependence of upconversion intensities on the 980 nm fiber laser. The temperature-sensing properties of Tm3+ in oxyfluoride tellurite glass were investigated using 3F2,3 → 3H6 (698 nm) and 3H4→3H6 (801 nm) excited at 980 nm, and the 3F2,3 and 3H4 states of Tm3+ were thermally coupled levels.