Optimization of Dy3+-doped Ge–Ga–As–S–CsBr glass composition and its 1.31 μm emission properties

An optimum glass composition for practical fiber fabrication was investigated for Ge–Ga–As–S–CsBr glasses. Dy3+ was doped into the glasses and its emission properties were examined. The best composition for practical use was 0.7[Ge0.25As0.1S0.65]–0.15GaS3/2–0.15CsBr. This glass also exhibited high resistance against the attack of liquid water. The lifetime and quantum efficiency of the 1.31 μm emission from Dy3+ increased approximately 17 and 4 times, respectively, compared to those obtained from other sulfide glasses. This is due to the formation of [GaS3/2Br]− units. The frequency of the effective phonon which dominates the multiphonon relaxation process decreased from 375 to 245 cm−1 with the addition of CsBr.