Generation of transform-limited pulse train in new scheme of harmonically mode-locked Er-doped fiber ring lasers

A new scheme of an amplitude modulated harmonically mode-locked Er-doped fiber ring laser is proposed, and the lasing characteristics are experimentally investigated. The transform-limited sech(2) pulses at the repetition frequency of 1.64 GHz are stably generated. The pulse width and spectral bandwidth are independent of both the amplitude modulated (AM) modulation signal frequency and the AM modulation depth.