Novel Optical XOR/OR Logic Gates Based on Topologically Protected Valley Photonic Crystals Edges

Valley Photonic Crystals (VPC) have provided a novel topological photonic platform to manipulate light. Here, we construct zigzag and armchair domain walls using two-dimensional silicon VPC, the edges between domains of opposite valley indices link to corresponding topological invariant. We study the light transmission of these edges under defects and sharp bent corners. Based on the Valley-contrasting edges, we design the all-optical logic gates at telecommunication wavelength with XOR/OR function simultaneously. Topologically protected waveguides own high transmission and backscattering-immune features, and coupling of different edge modes result in interference for logic function. Compared with traditional Photonic Crystals logic gates, our device shows outstanding properties including robust transmission, higher contrast ratio and more compact footprint. And it also shows the potential of topological photonics applying in optical logic circuits.