Energy transfer and upconversion in erbium-ytterbium-doped fluoride phosphate glasses

Abstract

The energy-transfer rate coefficient from ytterbium to erbium (K) and upconversion rate coefficient for erbium (C) are determined by analysis of erbium fluorescence decay under different pumping conditions. A simple rate-equation model was used to describe the fluorescence dynamics. Numerical analysis of the model delivered K and C as fit parameters to the experimental curves. Values of K ranging from 0.75-1.42 × 10-16 cm3/s and C from 0.8-1.7 × 10-18 cm3/s were found. The results obtained are of the same magnitude as results for phosphate glasses reported in the literature. Further analysis showed that high erbium concentrations (2 × 1020 cm-3) need a much higher pump intensity to reach threshold due to increased losses caused by upconversion.