Analysis of periodic pulse evolutions in a passively mode-locked ring dye laser

Complex pulse evolutions, observed in a passively mode-locked continuous phase modulated ring dye laser, that are highly sensitive to the frequency chirping processes in the laser cavity are investigated. For particular values of intracavity group velocity dispersion, the pulse evolutions are periodic and reminiscent of soliton evolutions. A numerical model of the laser that successfully simulates the qualitative features of the real laser output temporally and spectrally is described. A careful investigation of the numerical model shows that, in the case of strong mode locking, the observed periodic pulse evolutions are not solitonlike, but result from a combination of frequency chirp and spectral walkoff. A distinct regime is identified where solitonlike pulse evolutions are sustained, and the transition between the two modes of operation is related to the strength of the mode locking