Upconversion and near infrared emission properties of a novel Er3+/Yb3+ codoped fluoro-tellurite glass

A series of Er3+/Yb3+ co-doped novel fluoro-tellurite glasses was prepared following the melt quenching technique. Raman spectroscopy was used to analyze the functional groups present in the glass network and to determine the phonon energy of this glassy system. The optical properties of the glasses were characterized by different techniques such as optical absorption, photoluminescence (visible and near infrared) and time-resolved spectroscopy. Using optical absorption data and Judd-Ofelt theory, several spectroscopic parameters such as transition probabilities, radiative lifetimes and branching ratios were estimated for different Yb2O3 contents. The up-conversion process, after excitation with an infrared radiation at 980 nm, was examined and the different mechanisms involved in these emissions such as excited state absorption, energy transfer processes and cross-relaxation are discussed. The emission cross-section corresponding to the 4I13/2 level was calculated using McCumber theory. The experimental lifetime and the quantum efficiency corresponding to the 4I13/2 level were also determined to evaluate the appropriateness of the host matrix for the fabrication of laser materials and broadband amplifiers. It was found that the effective bandwidth is larger and quantum efficiency and the emission cross-section are higher than those obtained for others vitreous systems, which suggests that the proposed glasses can be nominated as suitable host material for new Er3+/Yb3+codoped broadband optical amplifiers and for the development of optical devices.