Novel optical XOR/OR logic gates based on topologically protected valley photonic crystals edges

Abstract

Valley photonic crystals (VPCs) have provided a novel topological photonic platform to manipulate light. In this work, we construct zigzag and armchair domain walls using two-dimensional silicon VPCs, the edges between domains of opposite valley indices link to the corresponding topological invariant. We study the light transmission of these edges with defects and sharp bent corners. We design all-optical logic gates at telecommunication wavelength with both XOR and OR functions based on the valley-contrasting edges. Topologically protected waveguides own high transmission and backscattering-immune features, and the coupling process of different edge modes results in interference for logic functions. Compared with traditional photonic crystal logic gates, our device shows outstanding properties, including robust transmission, higher contrast ratio and more compact footprint. Furthermore, our work also shows the potential of topological photonics to be applied in optical logic circuits.