High-efficiency, low-threshold mid-infrared Er-doped fiber lasers based on optimized pump wavelength in 1.6-1.7 μm

In this work, we demonstrated that a single pump source in the 1.57-1.72 μm band can enable mid-infrared 2.8 μm lasing in Er-doped fluoride fiber via ground state absorption and excited-state absorption. The efficiency evolution of 2.8-μm fiber lasers with respect to pump wavelength was experimentally investigated. The high slope efficiency of ⪆50% and low laser threshold of ⪅0.1 W have been achieved with optimized fiber doping concentration and pump wavelength. This pioneer work paves the way for the further power scaling of mid-infrared 3 μm Er fiber lasers pumped by near-infrared fiber lasers.