We report on a compact,high-efficiency mid-infrared continuous-wave(CW)Fe∶ZnSe laser pumped by a 2.9 μm fiber laser under liquid nitrogen cooling.A maximum output power of 5.5 W and a slope efficiency of up to 66.3％with respect to the launched pump power were obtained.The overall optical-to-optical(OTO)conversion efficiency,calculated from the output of the 2.9 μm fiber laser to the 4 μm laser,was as high as～54.5％.The OTO efficiency and the slope efficiency are,to the best of our knowledge,the highest ever reported in Fe∶ZnSe lasers.A rate-equation-based numerical model of CW operation was established,and the simulation agreed well with the experiment,identifying the routes used in the experiment for such high efficiency.
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