Rare earth dopants as probes of localized states in chalcogenide glasses

The recently observed phenomenon of broad band excitation of rare earth dopants in chalcogenide glasses indicates an interaction between the rare earth ions and localized background defect states ill the glass. Low temperature (5 K) photoluminescence and photoluminescence excitation spectroscopy of Er2S3-doped As12Ge33Se55 samples show similarities in excitation lineshape, Stokes shift, and spectral position to the intrinsic luminescence of an undoped As12Ge33Se55 sample. Fatiguing of the broad band excitation has been observed in Er-doped As12Ge33Se55 and As2S3 samples. These results indicate that the broad excitation band involves interaction with the same native defects in the host glass which give rise to important optical, electrical, and magnetic resonance properties of the chalcogenides. A model for the energy transfer process from the host glass to the rare earths, mediated by intrinsic defect states in the glass is presented. Some features of existing models for the behavior of chalcogenide glasses will be evaluated in light of our results. (C) 1998 Elsevier Science B.V.