2.8 μm Er3+-Doped Zinc-Tellurite Fiber Lasers Pumped by 976 nm Laser Diode

Erbium-doped high purity zinc-tellurite fiber lasers operating at 2.7– $2.8~\mu \text{m}$ were demonstrated by pumping in the 980 nm Er3+ absorption band. To the best of our knowledge, a maximum pulse energy of $500~\mu \text{J}$ over $\sim 100~\mu \text{s}$ duration with a slope efficiency of 5 % was achieved for the first time in a 50-cm TeO2-ZnO-La2O3-Na2O-Er2O3 glass fiber containing 2.5 mol % Er2O3. Lasers operating at $2.7~\mu \text{m}$ and $2.8~\mu \text{m}$ were also demonstrated with 35-cm and 70-cm gain fibers, respectively, but with lower slope efficiencies. For pumping Er3+-doped zinc-tellurite fibers, we used a low-cost high efficiency diode laser at 976 nm, which already provides an opportunity to implement the milliwatt level of a fiber laser of practical interest.