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 1G4→3H6 transition and the other at 667 nm due to 1G4→3F4 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 1G4→3H6 and 1G4→3F4 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 (3H5+3H5→3H6+3F2) enhanced resulting in the decrease of up-conversion luminescence intensities and leading to the concentration quenching.