Up-conversion luminescence of Tm3+/Yb3+ co-doped oxy-fluoride glasses

The oxy-fluorosilicate glasses co-doped with Yb3+/Tm3+ were prepared. The absorption spectra were recorded. The Tm3+ ion showed two absorption bands, with one at 774 nm due to (1)G(4)-> H-3(6) transition and the other at 667 nm due to (1)G(4)-> F-3(4) transition. The energy transfer between Tm3+ ion and Yb3+ ion and the up-conversion fluorescence of Tm3+ ion were investigated using 980 nm LD excitation. The results showed that the blue and red emissions were three-photon absorption processes corresponding with (1)G(4)-> H-3(6) and (1)G(4)-> F-3(4) transition, respectively. Compared with the fluorescence intensities of the different Tm3+ doping concentration samples, 0.2 mol.% is the optimal concentration for the oxy-fluorosilicate glass. When the concentration was more than 0.2 mol.%, the cross relaxation of Tm3+ ions (H-3(5)+H-3(5)-> H-3(6)+F-3(2)) enhanced resulting in the decrease of up-conversion luminescence intensities and leading to the concentration quenching.