Passive Harmonically Mode-Locked Erbium-Doped Fiber Laser

Passive harmonically mode-locked erbium-doped fiber ring laser with scalable repetition rates up to 1.2 gigahertz is experimentally demonstrated, to the authors' best knowledge, which is hitherto maximum repetition rate from only-erbium-doped fiber laser. Owing to the acousto-optic effect, stable passive harmonically mode-locking can only occur at some certain discrete repetition rates corresponding to resonant frequencies of transversal acoustic wave induced by propagating optical pulses in fibers. Passively mode-locked fiber laser has been under intense investigation due to its simplicity and compactness for the past few years.