Coexistence and competition between different soliton-shaping mechanisms in a laser

There exist two distinctive types of soliton-shaping mechanisms in mode-locked fiber lasers: one is the balance between the fiber nonlinear Kerr effect and the linear cavity dispersion, and the other one is that caused by the laser gain saturation and dispersion. We show both numerically and experimentally that as the net cavity group velocity dispersion approaches zero, the two types of soliton-shaping mechanisms coexist in a laser. Depending on the laser operation, either of them could dominate the pulse shaping in a laser. And as a result of their competition, the stable soliton formed in the cavity dispersion regime could have different temporal and spectral profiles.