Propagation of electromagnetic solitons in nonlinear negative-index materials

The propagation property of electromagnetic solitons in the negative-index material with a nonlinear polarization is investigated numerically. The role of the negative self-steepening and the higher-order nonlinear dispersion effects, which are resulted from the dispersive permeability of negative-index material, in soliton propagation is identified. It is shown that, like the positive self-steepening effect, the negative self-steepening effect also leads to asymmetry of soliton, shift of the center of soliton, and decay of higher-order solitons. The sign of self-steepening determines the direction of shift. The second order nonlinear dispersion effect broadens the pulse, as the linear second order dispersion does.