Self-consistent treatment of the full vectorial nonlinear optical pulse propagation equation in an isotropic medium

We derive a propagation equation for the pulse envelope of an electromagnetic field in an isotropic nonlinear dispersive media. The equation is first order in the propagation coordinate. We develop expressions valid without any additional assumptions on the form of the nonlinear polarization. Specific results are given for a Kerr-type nonlinear polarization in the form of a truncated nonlinear differential polynomial. We discuss the applicability of the expansion and determine the conditions for its validity; if and only if the counter-propagating wave is negligible is the expansion valid. We take into account a vectorial character of the electromagnetic field and show that it generates corrections of the same order as the nonparaxial terms. 2003 Elsevier Science B.V. All rights reserved.