All Fiber Actively Mode-Locked Ytterbium-Doped Laser With Large Range Temporal Tunability

An all-fiber ytterbium-doped laser widely tunable in duration and repetition rate is reported, which is actively mode locked based on a high speed in-cavity intensity modulator. The laser can generate a stable pulse train with a duration adjustable from 31 to 910 ps, and a repetition rate ranging from 13.12 MHz to 6.2 GHz (from the basic to the 475th-order harmonic) without changing the cavity construction. The cavity supermode suppression ratio is as good as 45 dB, and the signal-to-noise ratio is better than 48 dB at the 475th-harmonic mode locking. To the best of our knowledge, it is the highest order (475th) harmonic mode locking achieved in an all-normal-dispersion ytterbium-doped fiber laser, with the widest tuning range of repetition rate and pulsewidth.