Hybrid-filtering-controlled pulse dynamics in mode-locked fiber lasers

We numerically investigate the resembling pulse regimes in mode-locked fiber lasers through hybrid filtering implemented using super-Gaussian and sinusoidal spectral filters (SSFs). By modulating the saturation energy and filter bandwidth of the SSF, several stable regimes of resembling pulses including single, bounded, overlapped double resembling, and bounded triple resembling pulses can be produced. We explore the pulse characteristics of different single and bounded resembling pulses, such as the pulse intervals, chirps, optical spectra, and regime formation. During the transition between different mode-locked regimes, chaotic and pulsating pulses emerge, similar to the scenario of transitions induced by a single filter. Further study shows that synchronous and asynchronous power oscillations are produced in the pulse intensity and optical spectra when the laser operates at three typical pulsating states and one chaotic state. This paper reveals the effect of hybrid filtering on multipulse dynamics and proposes a method for modulating the mode-locking resembling pulses in fiber lasers.