High-Power Mid-Infrared 2.8-μm Ultrafast Raman Laser Based on Methane-Filled Anti-Resonant Fiber

High-power mid-infrared 2.8- $\mu \text{m}$ ultrafast laser has potential applications in the fields of laser surgery due to its wavelength overlap with the absorption peak of water. In this work, we demonstrate a 2.8- $\mu \text{m}$ picosecond Raman laser in a methane-filled hollow-core anti-resonant fiber (HC-ARF) with average power of 4 W, pulse energy of 40 $\mu \text{J}$ , and beam quality of 1.47. The laser beam quality improvement at mid-infrared Raman conversion in methane-filled HC-ARF is firstly observed. This work heralds a promising approach to generate mid-infrared ultrafast Raman laser with multi-Watt level average power and high beam quality.