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 Dy 3+ ( 6 F 11/2 · 6 H 9/2 → 6 H 15/2 ) increased sharply when the appropriate amount of alkali halides was added, at the expense of the 1.75-μm emission intensity ( 6 H 11/2 → 6 H 15/2 ). 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.% Dy 3+ ) 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 Eu 3+ . The nearest neighbors of Eu 3+ ions are composed of halogen ions that are part of well-structured complex such as EuCl 3 , tetrahedral 〚GaS 3/2 Cl〛 – subunit and/or Ga 2 Cl 6 . 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 〚Ge 0.25 As 0.10 S 0.65 〛–0.15 GaS 3/2 –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.