Upconversion luminescence in Tm3+/Yb3+co-doped lead tungstate tellurite glasses

This work reports the upconversion luminescence properties of Tm3+/Yb3+ ions in lead tungstate tellurite (LTT) glasses. Judd–Oflet intensity parameters have been obtained from the absorption band intensities of Tm3+ singly-doped and Tm3+/Yb3+ co-doped LTT glasses. The spontaneous emission probabilities, radiative lifetimes and branching ratios for 1G4 and 3H4 emission levels of Tm3+ have been determined. Upconversion luminescence has been observed by exciting the samples at 980 nm (Yb3+:2F7/2→2F5/2) at room temperature. Four upconversion emission bands corresponding to the 1G4→3H6 (477 nm), 1G4→3F4 (651 nm), 1G4→3H5 (702 nm) and 3H4→3H6 (810 nm) transitions have been identified. The relative variation in the intensities of upconversion bands, the different channels responsible for upconversion spectra and the effect of Yb3+ ions concentration on the upconversion luminescence of Tm3+ ions have also been discussed.