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

Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy of Pr/sub 2/S/sub 3/-doped As/sub 12/Ge/sub 33/Se/sub 55/ glass have detected two broad peaks in the PL spectrum, centered at /spl sim/1340 nn and /spl sim/1620 nm, characteristic of the /sup 1/G/sub 4//spl rarr//sup 3/H/sub 5/ and /sup 3/F/sub 3//spl rarr//sup 3/H/sub 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/sub 12/Ge/sub 33/Se/sub 55/ and As/sub 2/S/sub 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.