Fabrication of Integrated Single Frequency DBR Fiber Laser Directly on YDF by Femtosecond Laser

A 1080 nm single-polarization single frequency distributed Bragg reflector (DBR) fiber laser is fabricated by directly inscribing fiber Bragg gratings (FBGs) in ytterbium-doped fiber using a femtosecond laser. The high reflectivity FBG with high birefringence is prepared by femtosecond laser overexposure, serving a polarizing element. The low reflectivity FBG is inscribed by scanning axially along the fiber to narrow the FBG bandwidth. This DBR fiber laser avoided the mode hopping as temperature variation and intracavity fusion loss. A single frequency laser with an output power greater than 11 mW, a linewidth of 32 kHz, and a polarization extinction ratio of 10 dB is achieved at a pump power of 517 mW. The influences of the cavity length and LR-FBG reflectivity on the linewidth and output power are further studied. This provides a reference for optimizing the performance of integrated single-frequency DBR fiber laser prepared by a femtosecond laser.