[Direct sensitization up-conversion mechanism from Yb3+ to Ho3+ and Tm3+ in fluoride].

ABSTRACT

The direct sensitization up-conversion processes from Yb3+ to Ho3+ and Tm3+ in fluoride were studied. The properties of the up-converted spectra of Yb3+ /Ho3+ and Ho3+ /Yb3+ /Tm3+ co-doped fluorides pumped by a 980 nm laser were compared. Their up-conversion mechanism has been analyzed and discussed. Two strong up-conversion luminescence bands have been observed, which were the transitions of 5 F4 5 S2 (Ho3+) -->18 (Ho3+) in the Yb3+ /Ho3+ co-doped fluoride system and 3 H4 (Tm3+) --> 3 H6 (Tm3+) in the Ho+ /Yb3+ /Tm3+ co-doped fluoride system. The addition of Tm3+ into Yb3+ /Ho3+ co-doped fluoride decreases the up-converted emission intensities of Ho3+ in the visible region.