1.3-μm-emission properties and local structure of Dy3+ in chalcohalide glasses

Spectroscopic properties and local structure of rare-earth ions in Ge–Ga–S glasses with the addition of alkali halides were investigated. The intensity of the 1.31-μm emission from Dy3+ (6F11/2·6H9/2 → 6H15/2) increased sharply when the appropriate amount of alkali halides was added, at the expense of the 1.75-μm emission intensity (6H11/2 →6H15/2). The lifetimes of the 1.31-μm emission level also increased as much as 35 times from 38 μs for Ge–Ga–S glass (0.1 at.% Dy3+) to 1320 μs for glass containing 10 mol% of CsBr. These enhancements occurred only when the ratio of MX(M = K,Cs and X = Br, I)/Ga was equal to or larger than unity. Phonon side band (PSB) showed that the several local phonon modes, with the frequencies around 100 cm–1, were coupled to 4f electrons of Eu3+. The nearest neighbors of Eu3+ ions are composed of halogen ions that are part of well-structured complex such as EuCl3, tetrahedral ⟦GaS3/2Cl〉– subunit and/or Ga2Cl6. A small amount of As was added to increase the resistivity against the recrystallization during re-heating. The best composition for practical usage was 0.7 ⟦Ge0.25As0.10S0.65〉–0.15 GaS3/2–0.15 CsBr. This glass also exhibited high resistance against the attack of liquid water and is therefore a potential material for efficient fiber-optic amplifiers. [Copyright &y& Elsevier]