Photoinduced effects in undoped and rare-earth doped chalcogenide glasses: review

Abstract

The mechanisms of metastable photoinduced anisotropy and photorefraction in chalcogenide glasses are proposed based on increased polarizability of these materials (increased cubic susceptibility χ (3)). Flexible intrinsic structural units (oppositely charged chalcogen pairs) are suggested to be the origin of photoinduced anisotropy, and account for its re-orientation reversibility. I suggest that inflexible, photo-created, charged cation trapping sites dominate the mechanism of photorefraction. An increase of photoinduced anisotropy in glasses doped with Pr 3+ ions is reported and attributed to Pr 3+-induced increase of polarizability of charged chalcogen pairs, when Pr 3+ ions adhere to the negatively charged component of these pairs. The Boson peak in the Raman spectra of glasses increases with Pr 3+-doping confirming an increase of polarizability of intrinsic structural units into which Pr 3+ ions are incorporated. The Boson peak also increases after prolonged irradiation of chalcogenide glasses with near-gap-light indicating a light-induced creation of bonds with increased polarizability (e.g. broken bonds), which cause photorefraction. Fatigue of host and Pr 3+-dopant photoluminescence in chalcogenide glasses induced by prolonged irradiation with near-gap-light is discussed in correlation with accompanying photorefraction.