A single frequency narrow linewidth fiber laser based on quasi‐π‐phase‐shifted grating

Abstract

We propose and demonstrate a single frequency narrow linewidth fiber laser composed of the quasi‐π‐phase‐shifted grating (QπPSG) with a short line cavity and a structure of distributed feedback. On the high‐precision displacement platform, quasi‐π phase shift is introduced between two uniform fiber Bragg gratings based on a high‐concentration Erbium‐doped fiber (EDF) by ultraviolet exposure. Coupling the 980 nm pumped light to the QπPSG, the obtained laser is further amplified using a section of low‐concentration EDF. The single frequency lasing is achieved with a central wavelength of 1550.5 nm, and a slope efficiency of about 5.7%.