Design of ultrahigh-contrast all-optical diodes based on coupled nonlinear photonic crystal defects

We design and investigate the unidirectional transmission behavior of coupled photonic crystal defects with instantaneous Kerr nonlinearity. Theoretical analysis based on coupled-mode theory and numerical simulations based on finite-difference time-domain techniques indicate that ultrahigh-contrast all-optical diodes can be achieved by properly misaligning the frequencies of the coupled cavities. The transmission contrasts of such configurations composed of three and four cavities are demonstrated to be as high as 518 and 7015, with 42.8% and 46.3% forward transmissions, respectively. (C) 2011 Elsevier B.V. All rights reserved.