Asymmetric Gain-Guided Pulses

In many practical problems dealing with optical amplification a frequency dependence of the gain (that usually is broader compared to the considered signal bandwidth) is assumed to be symmetric and is approximated by the Lorentzian spectral shape [1]–[2]. This is often a justified assumption in the spectral region near the peak of the gain curve. There are, however, relatively less explored possibilities to use edges of the gain profile where amplification is not symmetric. In recent work of the Cornell group [3] a new type of asymmetric nonlinear pulse propagation was demonstrated distinguished by the presence of a dynamically-evolving gain spectrum. The dynamic change of the gain and spectral broadening led to quasi-stable regimes where pulse was partially propagating at the edge of the material gain curve. We anticipate that our analysis of much more simple model might provide useful insight into characteristics of nonlinear pulse propagation in a medium with spectrally asymmetric amplification, beyond standard parabolic gain curve approximations.