Temperature quenching characteristics of infrared-to-visible frequency up-conversion (UC) in erbium doped zinc tellurite glasses under infrared excitation 797 nm are presented. A comprehensive 4-level model has been developed and the derived rate equations have been exploited to examine the thermal quenching of efficiency and emission intensity for the UC. The green (4 S 3/2 → 4 I 15/2) and red (4 F 9/2 → 4 I 15/2) emissions over a temperature range 10-340 K and at concentration 2.0 mol% have

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... en studied. The green emission shows a continuous increase with decrease of temperature while the red emission is not that sensitive to temperature. In addition, the temperature dependence on the multi-phonon relaxation rates is fitted with 4 phonons processes. These features are attributed to the non-radiative (NR) energy transfer processes, trapped impurity effects and thermal assisted hopping. It is further indicated that to achieve higher infrared to visible up-converted efficiency in zinc tellurite glasses the NR channels for energy and charge transfer by phonon and impurity mediated process has to be minimized. Our results on pump power dependent emission intensity, quantum efficiency, luminescence intensity and NR multi-phonon relaxation rates are in conformity with other findings. The present systematic study provides useful information for further development of UC lasers. 1 Introduction In the new millennium, there has been a renaissance to study the rare-earth (RE) doped glass materials for photonic applications, e.g. phosphors, display monitors, X-ray imaging, scintillators, lasers and amplifiers for fiber-optic communications 1,2. The RE ions, especially erbium, have played an important role in the development of broadband erbium-doped fiber amplifiers in optical communication technology during the past few decades 3. In recent years, tellurite glasses are of growing interest due to their unusual large infrared transparency, high linear and non-linear refractive indices, good thermal and mechanical stability and corrosion resistance, suitable as a matrix for active element doping, a wide transmission window, lowest cutoff phonon energy and the highest emission cross-section over the entire range of emission wavelength. These notable features make them promising candidates for photonic applications such as window materials, optical memory and UC laser 4,5. Improving the UC efficiency is the key issue in tellurite glasses. The quantum efficiency, radiative transition rate and lifetimes of excited states are greatly influenced by the optical properties of the host