415W Single-Mode CW Thulium Fiber Laser in all-fiber format

High power Tm lasers at 2um region is a great source of interest for many application including optical pumping of hybrid (fiber-solid state) lasers, bio-medical, remote sensing and plastic welding. Cladding-pumped single-mode Tm-doped fiber lasers demonstrate significant advantages over solid state Tm lasers. Over last several years multiple groups [1,2] using different techniques demonstrated power scaling of fiber bas ed Tm laser to above 100W level. In this paper, we report a development of a single mode all-fiber format Tm fiber laser with M -value of < =1.1, emission linewidth of <1 nm at 1940nm and output power exceeding 400W CW. This is a highest CW output power for a single-mode Tm fiber laser reported up to date.