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

In this work, we demonstrated that a single pump source in the 1.57-1.72 mu m band can enable mid-infrared 2.8 mu m lasing in Er-doped fluoride fiber via ground state absorption and excited-state absorption. The efficiency evolution of 2.8-mu m 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 mu m Er fiber lasers pumped by near-infrared fiber lasers.