Fabrication of π phase-shifted fiber Bragg grating and its application in narrow linewidth 1.5 μm Er-doped fiber lasers

Using a π phase-shifted fiber Bragg grating (PSFBG) as narrow band filtering component is an important method for narrow linewidth fiber lasers, which have lots of applications in fiber sensors, optical communication, coherent detection and combination. In this paper, we design and fabricate two π PSFBGs by π phase-shifted phase mask. A narrow linewidth 1.5 μm Er-doped fiber ring laser employing one of the two π PSFBGs is set up, and the characteristics of the laser power and spectrum are investigated experimentally. A maximum laser power about 2.22 W at 1549.5 nm with linewidth ∼1 GHz is achieved, and the maximum slope efficiency is 35.8%. To the best of our knowledge, it is the highest power for GHz-level C-band fiber lasers. Further, high-efficient, high-power, single-longitudinal-mode fiber lasers could be achieved by optimizing the π PSFBG and the structure of the cavity.