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.