A high power narrow linewidth 1018 nm fiber laser based on a single mode–few mod

We demonstrate an all-fiber high-power Yb-doped 1018 nm fiber laser with a Gaussian-shaped output beam profile based on a mismatched structure, which consists of a pair of single-mode fiber Bragg gratings and a section of few-mode double-cladding gain fiber. The output power is up to 107.5W with an