Study of optical absorption, visible emission and NIR-vis luminescence spectra of Tm3+/Yb3+, Ho3+/Yb3+ and Tm3+/Ho3+/Yb3+ doped tellurite glasses

Tm3+/Yb3+, Ho3+/Yb3+ co-doped and Tm3+/Ho3+/Yb3+ triply doped TeO2-Bi2O3-ZnO-Li2O-Nb2O5 (TBZLN) tellurite glasses were prepared by melt quenching method. Judd-Ofelt intensity parameters (Ωλ, λ=2, 4 and 6), radiative transition probabilities, branching ratios and radiative lifetimes of Tm3+, Ho3+ ions in co-doped TBZLN glasses were calculated from the optical absorption spectra. Excitation, visible luminescence and decay lifetimes in visible region were also investigated. The stimulated emission and gain cross-sections for the Tm3+:3F4→3H6 (1700 nm) and Ho3+:5I7→5I8 (1956 nm) transitions in co-doped TBZLN glasses have been analyzed and compared with those of other reported glasses. Up-conversion luminescence was observed in TBZLN glasses under 980 nm laser excitation and energy transfer mechanisms have been discussed. Finally, CIE color co-ordinates were calculated and it is observed that the color co-ordinates fall in blue and green regions for Tm3+/Yb3+ and Ho3+/Yb3+ co-doped TBZLN glasses, respectively. A subsequent shift in color co-ordinates from green to greenish-yellow region has been observed with an increase in the concentration (0.1, 0.5 and 1.0 mol%) of Tm3+ ions in Tm3+/Ho3+/Yb3+ triply doped TBZLN glasses.