Dy3+-doped GeSe2–Ga2Se3–CsI chalcohalide glasses were prepared. The thermal stabilities, optical properties, emission properties, and structure of the glasses were investigated. Upon excitation with a 808-nm diode laser, 1.32-μm near-infrared fluorescence was observed with a broad full width at half-maximum of about 90 nm. It was found the 1.32-μm fluorescence lifetime of the Dy3+-doped GeSe2–Ga2Se3–CsI glass depends on the I/Ga molar ratio and the amount of Ga2Se3 and CsI. The longest lifetime is >2.5 ms. It is noted that the value is significantly higher than those in other Dy3+-doped glasses. The enhancement of lifetime can be attributed to a decreased local phonon mode, which dominates the multiphonon relaxation. Meanwhile, it is interesting to note that the GeSe2–Ga2Se3–CsI glasses have shown good infrared transmittance. As a result, Dy3+-doped GeSe2–Ga2Se3–CsI glasses have been considered to be an attractive host for a 1.3-μm optical fiber amplifier.
