Pulse dynamics in dispersive nonlinear medium in presence of traveling refractive-index wave

The dynamics of wave packets propagating in nonlinear waveguides in presence of a traveling refractive-index wave is investigated. It is shown that the regime of self-steepening is possible in these waveguides not only at the trailing edge of the wave packet, but also at its leading edge. Nonreciprocal effects are typically observed when the optical pulse and the wave of optical inhomogeneity are either co- or counterpropagating.