Constructive and destructive perturbations of dark solitons in mode-locked lasers

The locking mechanism to dark solitons in passive mode-locked (ML) lasers is studied under the presence of perturbative effects. These include higher order dispersion, self-steepening, and Raman gain. Using a recently developed perturbation theory it is found that linear and nonlinear effects may be combined in such a way as to cancel their respect contributions resulting in stable pulses. Parameter values are found where mode-locking occurs and stable pulses, both black and grey, exist. This work explains why there can be wider observable regimes with ML dark soliton pulses. (fast track communication)