Narrow-Linewidth Erbium-Doped Fiber Laser with Ultrashort Random Distributed Feedback Based on Disordered Structures Fabricated by Femtosecond Laser Radiation

A narrow-linewidth erbium-doped fiber laser with random distributed feedback (RDFB) was demonstrated. A record-short 2-mm RDFB sample was fabricated using femtosecond inscription technique of disordered structures directly within the fiber. Despite its compact size, this structure provides a reflectivity equivalent to ~10 km of standard single-mode fiber. In a ring cavity configuration, the laser showed stable single-frequency operation over the entire pump power range. The central lasing wavelength was 1549.8 nm, the emission linewidth at half maximum was 0.6 kHz, and the maximum output power was 10.1 mW.