Stabilization of ultra-short pulses in cubic nonlinear media

We study the propagation of ultra-short pulses in a cubic nonlinear medium. Using multiple-scale technique, we derive a new wave equation that preserves the nonlocal dispersion present in Maxwell's equations. As a result, we are able to understand how ultra-short nonlinear shocks are stabilized by dispersive terms. A delicate balance between dispersion and nonlinearity leads to a new type of solitary waves. Their stability is confirmed by numerical simulations of full Maxwell's equations.