Switching of short pulses in nonlinear directional couplers: effects due to the dispersion of the coupling coefficient

Abstract

Nonlinear directional couplers have attracted considerable attention because of their potential applications in all-optical switching (see, for example, Refs.1 and 2, and references therein). The conventional way of analyzing pulse switching in an evanescent-field nonlinear coupler is based on solving the linearly coupled nonlinear Schrödinger equations.1,2 Recently, it has been found that these equations are valid only when the dispersion properties of the coupling coefficient can be ignored.3,4 In many practical situations, however, the coupling-coefficient dispersion can be important and must be included in the analysis.3,4 It has been shown, both theoretically3-5 and experimentally,6 that a dispersive coupling coefficient can cause pulse distortion, or even pulse breakup. In this paper, using a two-core fiber as an example, we first identify the situations under which the coupling-coefficient dispersion is important, and then demonstrate how the coupling-coefficient dispersion affects the switching dynamics of short pulses in a nonlinear coupler.