Tight-binding theory for coupling asymmetric photonic crystal waveguides

Abstract

The physical properties of asymmetric photonic-crystal directional couplers are studied under the tight-binding model, which assumes that the field distribution of photon ic-cryst al waveguides is localized around periodic defects. The couplings of nearby defects between two asymmetric waveguides cause two dispersion relations to split further whereas the couplings of nearby defects within an individual waveguide cause the sinusoidal modulations of the dispersion curves. The field-envelope distributions of the coupler are expressed by using the eigenmodes of the tightbinding equations and are consistent with the comparing results from finite-difference time-domain simulations.