Significant Enhancement of Unidirectional Transmission in Asymmetrically Confined Photonic Crystal Defect Pairs

By carrying out the two ideas of asymmetrical confinement and asymmetrical response into the photonic crystal (PC) structures that contain two or more nonlinear defects, we find that significantly unidirectional transmission can be
achieved while the transmission for the positive launch direction maintains at large values. Our analyses are supported by the simulation results based on the finite-difference time-domain technique.