Sub-Pulses Releasing From Noise-Like Pulses in a Passively Mode-Locked Fiber Laser

In this letter, we experimentally demonstrate various low-amplitude sub-pulses releasing from the rectangular-shaped noise-like pulses (NLPs) in a passively mode-locked fiber laser. Via incorporating a several hundred meters highly nonlinear fiber (HNLF) in the cavity, a series of continuous wave (CW) components are observed in the output optical spectrum, and sub-pulses formation results from the interactions among the CW components and the random ultrashort pulses in NLPs wave packet. A novel type of harmonic sub-pulses with 952.5874 MHz repetition rate is achieved, corresponding to the around 2994th harmonic of the fundamental cavity frequency. The obtained results contribute to further understanding the nature and formation mechanism of sub-pulses in NLPs regime.