Nonlinear optics of a few-cycle optical pulse: slow-envelope approximation revisited

Using Maxwell-Bloch equations, we analyze the response of an ensemble of two-level atoms driven by a femtosecond optical pulse beyond the traditional approach of slowly varying amplitudes and phases. For optical pulses of a given duration, we show that the off-resonance optical field can evolve into a stable (spatio-) temporal soliton.

I. Introduction

The recent progress in the development of solid-state mode-locked lasers has resulted in the generation of two-cycle optical pulses [1]. Subsequently, such short pulses have been widely exploited to generate a unipolar single-cycle electromagnetic pulse in a variety of nonlinear medium [2]. It has also resulted in theoretical studies in order to determine whether it is possible to describe correctly the dynamics of such pulses within the traditional framework of the slowly varying envelope approximation (SVEA) operating with a quasimonochromatic field [3] [4]– [8].