Selective transverse mode operation of an all-fiber laser with a mode-selective fiber Bragg grating pair

We propose a novel approach for achieving selective transverse mode operation of few-mode all-fiber lasers. Lasing in a specific transverse mode is enabled by employing a pair of few-mode fiber Bragg gratings as an efficient transverse mode selector. As a proof-of-principle, we have implemented a ytterbium-doped all-fiber laser operating in the second-order (LP₁₁) transverse mode. The achieved output power is 81 mW, and the slope efficiency is as high as 54%. This simple and compact all-fiber laser is also capable of delivering cylindrical vector beams through appropriate polarization control. Furthermore, the approach has great scalability and can be applied to other working modes and spectral regimes.