Experimental investigation of a high-power 1018 nm fiber laser using a 20/400 μm ytterbium-doped fiber

A 472 W monolithic fiber laser, operating at 1018 nm by employing an active fiber with a low core/cladding diameter ratio of 20/400 μm, is reported in this paper. The slope efficiency and beam quality factor (M2) of the fiber laser are, respectively, 49.4% and 1.17. To realize the setup, the effects of the characteristics of the experimental elements-reflectivity of the output coupling fiber Bragg grating, length of the active fiber, etc.-on the output behavior of the system have been investigated. These are the highest recorded output signal power, efficiency, and beam quality factor in monolithic 1018 nm ytterbium-doped fiber lasers using fibers with a core/cladding diameter ratio of 20/400 μm.