Spectral sidebands and multipulse formation in passively mode-locked lasers

Pulses in passively mode-locked lasers are often accompanied by dispersive waves that form spectral sidebands due to spatial inhomogeneities in the laser cavity. Here we present an explicit calculation of the amplitude, frequency, and precise shape of the sidebands accompanying a solitonlike pulse. We then extend the study to the global steady state of mode-locked lasers with a variable number of pulses, and present experimental results in a mode-locked fiber laser that confirm the theory. The strong correlation between the temporal width of the sidebands and the measured spacing between the pulses in a multipulse operation suggests that the sidebands have an important role in the interpulse interaction.