Normal modes of twin core periodic structures

Propagation in a nonlinear coupler is, for each initial excitation, like that in a linear coupler with a specified periodic refractive index in the direction of propagation. Such a periodic structure supports two normal periodic modes. In this paper we present the modal field expressions and propagation constants of the periodic modes in such a power-induced–like periodic structure and show that each initial excitation on a twin core nonlinear coupler leads to propagation of one of the periodic modes of the self-induced periodic structure.