Fiber Ring Laser Operated by Dynamic Local Phase Shifting of a Chirped Grating

An ultranarrow linewidth erbium-doped fiber ring laser is presented. It is based on the filtering properties of a phase-shifted chirped fiber Bragg grating, which is inserted inside the cavity of the laser. A dynamic control of the phase shifting, which is induced by a magnetostrictive transducer, permits both tunable continuous-wave and actively Q-switched operation. The use of a chirped grating overcomes the limitations imposed by the narrow spectra of uniform gratings observed in previously reported ring lasers based on intracavity transmission filters.