Solitons in normally dispersive mode-locked lasers

Soliton pulses in normally dispersive mode-locked lasers are considered using a nonlinear Schrödinger equation, appropriately modified to model power (intensity) and energy saturations. Strongly chirped, localized pulses are obtained when the effects of nonlinearity, dispersion, saturated gain, filtering, and loss form an appropriate balance. In the case of constant dispersion, perturbation theory yields a set of uncoupled equations for the amplitude and the phase of the soliton pulse. In dispersion-managed (DM) systems, an asymptotic multiple-scale theory is used to analyze the dynamics. This equation, which describes solitons in the anomalous regime, also admits higher-order solitons, the so-called antisymmetric soliton or bisoliton, in both constant dispersion and DM systems. Such pulses have been observed in recent experiments.