Effect of BaF 2 on the structural and spectroscopic properties of Er 3+ /Yb 3+ ions codoped fluoro-tellurite glasses

Abstract In this work, we investigate the effect of BaF 2 on the structural and optical properties of Er 3+ /Yb 3+ co-doped fluoro-tellurite glasses prepared by the melt quenching technique. Good thermal stability and low phonon energy of this glassy system were found using differential scanning calorimetry and Raman spectroscopy, respectively. Infrared measurements showed a significant shift of infrared longwave transmission limit by increasing fluoride content. By Judd-Ofelt theory, the local environment surrounding the Er 3+ ions was analyzed and several spectroscopic parameters such as radiative lifetimes, quantum efficiency, optical bandgap, effective bandwidth, emission cross-section and figure of merit of 4 I 13/2 → 4 I 15/2 transition were estimated and optimized with respect to the BaF 2 content. Due to the strong absorption of Yb 3+ at nearly 1000 nm, a high quantum efficiency of Er 3+ emission at 1530 nm (>100%) was detected and an upconversion mechanism was suggested to explain this significant enhancement. The results show some remarkable spectroscopic parameters attributed to the 4 I 13/2 → 4 I 15/2 transition, which have a major importance in many optical devices, and the investigated glass may be proposed in particular for conception of luminescent concentrators for germanium-based solar cells.