300-W high-brightness Yb-doped fiber laser near 980 nm based on a 3 × 1 fiber signal combiner

In this paper, a 300-W-level fiber laser near 980 nm is demonstrated with the M 2 factor of about 5.27 by using a 3 × 1 fiber signal combiner. This fiber laser is fabricated by beam combining three elementary step-index Yb-doped fiber lasers near 980 nm with a 3 × 1 fiber signal combiner. Then, about 296-W power was achieved from the output fiber of 50-μm core diameter, and the corresponding M 2 factor is about 5.27. It is also demonstrated that the beam quality with an M 2 factor of about 3 can be expected by optimizing the beam quality of elementary fiber lasers.