摘要： Mid-infrared lasers operating at wavelengths above ~3 μm are required for many applications. The lasers of a particular interest are those that can provide high average power and high quality of the output beam. A promising approach to realize such lasers is the use of gas-filled hollow-core fibers (HCF), which combine mid-infrared light guidance with all the advantages of well-established silica fiber technology. Recent progress in silica HCFs for mid-infrared spectral range has resulted in demonstration of various gas fiber lasers at wavelengths from 2.8 to 4.6 μm [1-5]. However, those lasers use bulk elements to couple the pump into a HCF, thus losing such advantages as compactness and alignment-free operation, which are expected from fiber lasers. In this work we demonstrate an all-fiber gas Raman laser operating in a single transversal mode at 4.42 μm and generating average output power as high as 360 mW. The Raman laser was constructed using silica-based fibers only (Fig.1a). A pump source was a high-power erbium-doped fiber laser emitting 2-ns pulses with 75-kHz repetition rate at 1.56 μm. The output fiber of the pump laser was fusion spliced to a revolver-type HCF. In spite of a large difference in mode field diameters of the solid-core and hollow-core fibers (20 and 55 μm, respectively), a 3-dB splice losses were obtained. The splice point was mechanically stable and no splice loss degradation was observed when HCF was filled by molecular hydrogen up to pressure of 50 atm. By using a 3.2-m-long hydrogen-filled revolver-type HCF we realized an efficient 1.56 to 4.42 μm Raman conversion in a single-pass single-cascade scheme. When 2.3 W of the pump average power was coupled to the HCF, the Raman laser generated as high as 360 mW of average power at 4.42 μm (Fig.1b). The quantum conversion efficiency was as high as 46 %. A beam quality factor of the output radiation at λ=4.42 μm was evaluated to be M2=1.4. Our results demonstrate that gas fiber Raman lasers based on revolver hollow-core silica fibers are a viable solution for the development of all-fiber mid-infrared lasers that combine a compact alignment-free design with high power single mode operation. An application area of such laser sources includes, but is not limited to, a high-average-power mid-infrared supercontinuum generation, which is of high importance for numerous applications in science, biomedicine and technology.