On the quasi-soliton propagation of few-cycle optical pulses in isotropic dielectrics

A new combined approach for constructing approximate soliton-like solutions of nonlinear wave equations is proposed. The approach includes the method of analytic continuation of dispersion parameters to the complex plane and the averaged variational principle of the Ritz-Whitham type. Based on this approach, the solution of the nonlinear equation describing the propagation of an optical pulse in a transparent isotropic dielectric is found. The obtained solution involves both envelope solitons and breather-like pulses with duration down to one period of electromagnetic oscillations.