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 BaF2 on the structural and optical properties of Er3+/Yb3+ 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 Er3+ 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 4I13/2→4I15/2 transition were estimated and optimized with respect to the BaF2 content. Due to the strong absorption of Yb3+ at nearly 1000 nm, a high quantum efficiency of Er3+ 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 4I13/2→4I15/2 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.