Direction-reversible all-optical diode based on a photonic heterostructure

We theoretically and systematically investigate the unidirectional optical transmission properties in photonic heterostructures consisting of nonlinear μ-negative materials and conventional photonic crystals. The analysis results reveal that the optical transmission in such nanostructures is unidirectional as the input intensity increases or decreases. However, the direction of optical transmission reverses when the input intensity exceeds a threshold. Therefore, a new, to the best of our knowledge, type of all-optical diode effect with reversible transmission direction is identified. Further analysis shows that the reversal can be achieved within a narrow band in such nanostructures. The underlying physical mechanism is the input intensity that changes the localized modes of the photonic interface states in the asymmetric photonic heterostructure, thereby reversing the transmission behavior when the input intensity increases or decreases to specific thresholds. These nanostructures can be important for developing novel direction-reversible all-optical diodes with potential applications in optical switching, communications, signal processing, and other fields.