Pulsating soliton with broadened Kelly sidebands in an ultrafast fiber laser

We experimentally observed a novel pulsating soliton state with broadened Kelly sidebands in an ultrafast laser. Through simulations, we found that the synchronized and unsynchronized resonant dispersive waves coexisted in the laser. The incoherent interaction between the unsynchronized dispersive waves and soliton resulted in oscillation of the intensity and central wavelength of the soliton. The frequencies of the Kelly sidebands oscillated with the soliton, resulting in their spectral broadening when measured by an optical spectrum analyzer. The numerical results agreed qualitatively well with the experiments. Our results are novel and useful for understanding the chaotic dynamics and designing of the ultrafast fiber laser.