Energy transfer betweenEr3+andTm3+ions in a barium fluoride–thorium fluoride glass

Abstract

The up-conversion of infrared radiation into green, red, and 805-nm fluorescence has been studied for ${\mathrm{Er}}^{3+}$ and ${\mathrm{Tm}}^{3+}$ ions in both ${\mathrm{Yb}}^{3+}$-doped and non-${\mathrm{Yb}}^{3+}$-doped ${\mathrm{BaF}}_2$-${\mathrm{ThF}}_4$ fluoride glass over a wide temperature range and several dopant concentrations. It has been found that the addition of ${\mathrm{Tm}}^{3+}$ preferentially quenches the up-conversion efficiency of the green emission corresponding to a transition from the ${}_{}{}^4{}_{}{}^{}\mathrm{S}_{3/2}^{}{}_{}{}^{}$ level of ${\mathrm{Er}}^{3+}$. The decrease in emission amounts to a factor of about 50 for a concentration of 0.5 mol % ${\mathrm{TmF}}_3$ at 300 K. The quenching effect is discussed in terms of energy transfer between ${\mathrm{Er}}^{3+}$ and ${\mathrm{Tm}}^{3+}$ ions. A rate equation model and a Judd-Ofelt analysis used in conjunction with the appropriate optical data lead to an understanding of the up-conversion process. The absolute values of the energy transfer rates and the electron populations in the lower excited states of the excited ${\mathrm{Er}}^{3+}$ and ${\mathrm{Tm}}^{3+}$ ions can be determined. This information should enable researchers to tailor materials to improve the efficiency of the up-conversion and laser devices.