Modification of the local phonon modes and electron–phonon coupling strengths in Dy3+-doped sulfide glasses for efficient 1.3 μm amplification

The effect of changes in the local phonon modes and electron–phonon coupling strengths on the 1.31 μm fluorescence efficiency of Dy3+-doped sulfide glass was investigated. An addition of 10 mole% CsBr resulted in a sharp increase in the 1.31 μm emission intensity at the expense of the 1.75 μm emission. The lifetime of the 1.31 μm emission level (6F11/2–6H9/2) increased to 1.58 ms, which was more than 40 times larger than that of the Ge–Ga–S host. Quantum efficiency increased from 17% to approximately 100%. These changes in the optical characteristics resulted from the large changes in the local phonon modes and electron-coupling strengths through the addition of CsBr to Ge25Ga10S65 glass.