All-optical diode based on the self-collimation characteristics of the near-infrared photonic crystal heterojunctions

The unidirectional light transmission characteristics of a two-dimensional square-lattice photonic crystal heterostructure consisting of rectangular metal rods and air holes immersed in silicon are studied by the finite-difference time-domain method. Compared with all-optical photonic crystal diodes based on the directional bandgap mismatch, this kind of diode can be designed to confine the light wave to travel along a certain direction owing to self-collimation behavior. The working frequencies of this diode are within the photonic crystal's passband, so a higher light transmittance can be obtained. This wideband high-contrast diode has the advantages of combination with other functional devices in the complex integrated optical circuits.