Extreme hypersensitivity observed from ⁶H_15/2 → ⁶F_11/2 transition of Dy³⁺ in inorganic noncrystalline solids

Absorption transition from the ground ⁶H_15/2 state to the superimposed (⁶H_9/2, ⁶F_11/2) states, inverse transition of which leads the Dy³⁺: 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 Dy³⁺: ⁶H_15/2 → ⁶F _11/2 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 [GaS_3/2Br]^- complexes, which are formed spontaneously during vitrification process of the host materials, is believed to be responsible for the behaviour.