Design of photonic directional couplers as phase selectors

Abstract

A phase selector is designed by relatively sliding two coupled identical photonic crystal waveguides (PCWs) of a photonic directional coupler (DC). By solving the coupled equations analytically derived from the tight-binding theory, symmetry breaking in the crossing of dispersion curves can be observed as countersliding two degenerated waveguides along the propagation direction. There exists a different phase shift between two eigenmodes by varying the sliding distance and the operating frequency. Numerical simulations of DCs made of photonic crystal slabs were used to verify the correctness of our theoretical predictions and to discuss thoroughly the underlying physics of the symmetry-breaking system. The design concept is provided for a phase selector or a beam splitter whose output phase difference can be controlled by the sliding distance of two PCWs. (C) 2013 Optical Society of America