Optical studies of Dy3+ doped tellurite glass: Observation of yellow-green upconversion

Optical absorption and fluorescence spectra of Dy3+ doped tellurite glass have been studied and Judd–Ofelt theory has been used to derive its optical properties. The effect of temperature on the fluorescence yield and fluorescence quenching for higher concentrations of Dy3+ has been studied and the mechanism involved discussed. It is found that the fluorescence intensity is larger at lower temperature. The lifetime of the 4F9/2 level has been measured and found to decrease with concentration as well as temperature. Intense upconversion has also been observed in the yellow-green region when pumped with NIR (∼862 nm) radiation. An explanation of the same involving energy transfer is offered.