Defect-enhanced resonances in photonic lattices

A study of defect-mode propagation in lossless layered photonic media has been performed. We put forward a new proper characteristic of the defect cavity, called the coupling length of the defect, namely, a maximum spatial radius around the defect site, within which the defect mode couples into the tunnelled incident wave. This coupling length allows us to optimize the values of the Q-factor and the transmission coefficient with respect to both the position of the defect and the dielectric permittivity of the defective layer.