Anomalous coupling between photonic crystal waveguides

The dispersion curves of the two coupled photonic crystal waveguides (PCWs) can intersect and change parities in a triangular photonic crystal (see F. S.-S. Chien etc., Opt. Express 12, 1119 (2004)). The PCWs are decoupled at the crossing point. We show that this anomalous coupling between two PCWs is caused by light being less localized at defects. Light can couple to the next nearest neighbors or even the next and next nearest neighbors.