Broad-band excitation of Pr(3+) luminescence by localized gap state absorption in Pr:As(12)Ge(33)Se(55) glass

Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy of Pr(2)S(3)-doped As(12)Ge(33)Se(55) glass have detected two broad peaks in the PL spectrum, centered at ~1340 nn and ~1620 nm, characteristic of the (1)G(4)- > (3)H(5 ) and (3)F(3)- > (3)H(4) transitions, respectively. The 1620-nm band exhibits a strong, broad, below-gap PLE band extending from 500 nm to 1000 nm, which is nearly identical to those previously observed in Er-doped As(12)Ge(33)Se(55) and As(2)S(3 ) glass. This indicates that such broad, below gap PLE bands are not unique to Er-doped systems, but are more general features of rare earth-doped chalcogenide glass. The novel, broad PLE bands are attributed to absorption by below-gap defect and impurity-induced localized states in the host glass that are able to transfer their energy efficiently to the rare earth dopants. A phenomological explanation of the energy transfer process is presented