Multicolor upconversion emission and energy transfer mechanism in Er~(3+)/Tm~(3+)/Yb~(3+) codoped tellurite glasses

摘要

A novel Er~(3+), Tm~(3+) and Yb~(3+) codoped tellurite glasses with composition of TeO_2-Bi_2O_3-ZnO-Na_2O was prepared by conventional melt-quenching technique to realize the multicolor upconversion (UC) emissions. The absorption spectrum, UC emission spectrum, Raman spectrum, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) curves were measured to characterize the prepared glass samples. Under the excitation of 980 nm laser diode (LD), bright multicolor luminescence composed of red, green and/or blue UC emissions corresponding to the transitions ~4F_(9/2)→~4I_(15/2), ~2H_(11/2)(~4S_(3/2))→~4I_(15/2) of Er~(3+) and ~1G_4→~3H_6 of Tm~(3+) were observed in the Er~(3+)/Yb~(3+), Tm~(3+)/Yb~(3+) and Er~(3+)/Tm~(3+)/Yb~(3+) codoped glass samples, which were mainly attributed to the successive energy transfers from Yb~(3+) to Er~(3+) and Tm~(3+), respectively. The energy transfer mechanisms from the Yb~(3+):~2F_(5/2) level to Er~(3+):~4I_(11/2) and Tm~(3+):~3H_5 levels were further investigated by quantitatively calculating the energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the difference (ΔT = T_X -T_g) between the glass crystallization onset temperature (T_x) and the transition temperature (T_g) which increase slightly with rare-earth (RE) doped concentration, was larger than 140 ℃ for all glass samples. Furthermore, the amorphous nature of glass structure was demonstrated by the measured XRD curves. The excellent thermal stability and multicolor luminescent characteristic indicate that the present investigated Er~(3+)/Tm~(3+)/Yb~(3+) codoped tellurite glasses could be used in the fields of solid state multicolor displays and other luminescent devices.