Emission and local structure of rare-earth ions in chalcogenide glasses

Local structures of rare-earth ions in Ge-Ga-S-CsBr glasses were investigated to understand the structural origin on the emission property enhancement. The frequency of the phonon vibration controlling the multiphonon relaxation was changed to 245 cm−1 due to the formation of Ga-Br bonds with CsBr addition to sulfide glasses. Formation of this new chemical bond was also confirmed from the phonon side band spectra of Eu3+ ions. Analyses of the EXASF spectra proved that Tm3+ ions were surrounded by approximately seven S ions in Ge0.25Ga0.10S0.65 glass but were coordinated by ∼6 Br ions in the glass with 10 mol% of CsBr.