Emission properties of the Er3+:4I11/2→4I13/2 transition in Er3+- and Er3+/Tm3+-doped Ge–Ga–As–S glasses

Ge–Ga–As–S glasses were investigated to develop efficient host materials for the Er3+:2.7 μm fiber lasers. Ge30Ga1As9S60 and Ge30Ga2As6S62 (all in at.%) glasses show good thermal stability and high rare-earth solubility up to 0.3 mol%. Mid-infrared emission with a peak wavelength of 2.76 μm and bandwidth of ∼120 nm was observed in Er3+- and Er3+/Tm3+-doped Ge30Ga2As6S62 glasses. Codoping of Tm3+ significantly reduced the lifetime of the Er3+:4I13/2 level due to the energy transfer of Er3+:4I13/2→Tm3+:3F4. Thus, the population inversion between the 4I11/2 and 4I13/2 levels in Er3+ became possible. In Er3+-doped glasses, the rate of cross-relaxation for the 4I11/2 level was approximately 11 times faster than that for the 4I13/2 level.