Spectroscopic properties and local structure of Eu3+ in Ge-Ga-S-CsBr (or CsCl) glasses

Abstract

Spectroscopic properties and local structure of Eu3+ in GeGa-S-CsBr (or CsCl) glasses were investigated using fluorescence measurements and several spectroscopic methods. Fluorescence from Eu3+:D-5(0) --> F-7(2) was observed only from glasses with CsBr/Ga ratios greater than unity and disappeared at temperatures above 140 K. Phonon sideband (PSB) spectra revealed that Eu3+ ions are located next to halogen ions, which form part of well-structured complexes such as EuCl3, tetrahedral [GaS3/2Cl](-), subunits and/or Ga2Cl6. These new bonds showed reduced coupling strength compared with Eu3+-S bonds in Ge-Ga-S glass. Fluorescence line narrowing experiments showed little site-to-site variation of Eu3+ ions.