Propagation and second-harmonic generation of electromagnetic waves in a coupled-resonator optical waveguide

Using both the tight-binding approximation and the finite-difference time domain method, we analyze two types of coupled-resonator optical waveguide (CROW), a coupled-microdisks waveguide and a waveguide composed of coupled defect cavities in a two-dimensional photonic crystal. We find that the dispersion relation of the CROW band can be simply described by a small coupling parameter κ, and the spatial characteristics of the CROW modes remain the same as those of the single-resonator high Q modes. As applications of these unique properties, we demonstrate that CROW’s can be utilized in constructing waveguides without cross talk and enhance the efficiency of second-harmonic generation.