Broad band excitation of Dy/sup 3+/ emission by localized tail state absorption in chalcogenide glasses

We have previously reported investigations of Er-doped and Pr-doped Ge/sub 33/As/sub 12/Se/sub 55/ glasses, both of which displayed exceptionally broad rare earth photoluminescence (PL) bands. In addition, the photoluminescence excitation (PLE) spectra of both the 1640 nm Pr(3+) emission (/sup 3/F/sub /spl rarr///sup 3/H/sub 4/) and the 1540 nm Er/sup 3+/ emission (/sup 4/I/sub 13/2//spl rarr//sup 4/I/sub 15/2/) exhibit nearly identical broad excitation bands from /spl sim/500-1000 nm. On the basis of their line shapes, these broad PLE bands were attributed to absorption by defect- or impurity-related localized band tail states in the host glass, which then transferred their energy to the rare earth atoms. We present here a parallel investigation of Dy-doped Ge/sub 33/As/sub 12/Se/sub 55/ glass. This is an excellent system in which to test our hypothesis concerning the origin of the broad PLE bands because the Dy atoms have a series of emissions ranging from 2800 nm to 1150 nm, all terminating in the ground slate. In addition, Dy-doped chalcogenide glasses are of technological interest because of possible application in fiber amplifiers.