Abstract
Absorption transition from the ground H state to the superimposed (H, F) states, inverse transition of which leads the Dy: 1.3 μm luminescence, in noncrystalline Ge-As-S alloys is dramatically modified upon a least compositional adjustment by Ga and CsBr. The change in oscillator strength of the Dy: H → F transition in our modified glasses is more sensitive to the local coordination structure of rare-earths compared to other hypersensitive transitions that have been previously observed in solid-state dielectric hosts. Preferential highly symmetric coordination in nearest-neighbouring shell of dysprosium with bromine in [GaSBr] complexes, which are formed spontaneously during vitrification process of the host materials, is believed to be responsible for the behaviour. © 2005 Elsevier B.V. All rights reserved.