7-core Yb-doped fiber laser with femtosecond pulse inscribed fiber Bragg gratings

Abstract

We report on the investigation of a 7-core Yb-doped fiber laser based on femtosecond pulse written fiber Bragg gratings. The fabricated FBG arrays are used as a complex high-reflective mirrors, whereas output coupling is provided by ~4% Fresnel reflection from the normally cleaved end of the fiber. At cladding pumping by a 976-nm laser diode, the cores generate independently with linear total power growth up to 33 W at 50 W pump power. The individual generation spectra slowly broaden to ~0.15 nm whereas net spectrum at maximum power is ~0.2 nm broad thus demonstrating highpower narrowband generation in multicore active fiber.