Widely-Chirped High-Repetition-Rate Continuous Wave FM Laser Oscillation in Erbium Fiber Ring Laser

A widely chirped high-repetition-rate continuous wave (CW) FM laser operation in an erbium fiber ring laser is demonstrated by intracavity phase modulation at 3.3 GHz. Continuous wave FM spectrum as wide as 726 GHz at 1.56 µm is generated with a modulator phase retardation of 3.02 rad and a cavity detuning of 24 kHz, corresponding to an FM modulation index of 109. This gives an extremely large chirp rate of 7.51×10 21 Hz/s of the output, highest of all reported so far on FM laser oscillation. The effect of detuning and modulator phase retardation on FM laser oscillation is investigated and compared with the theoretical results.