On/Off Switching of Valley Topological Edge States in the Terahertz Region

Topological photonic devices provide a powerful platform to control the flow of light because their topologically protected edge states can be immune to backscattering and be robust to impurities, disorders, and defects. As one of the topological photonic systems, valley photonic crystals have attracted great attention because they can achieve a large bandgap and be easily combined with modern micro-nano fabrication technology. Terahertz photonic devices are of enormous interest in next-generation communications. Here, we design a valley photonic crystal consisting of a triangular lattice with three metal rod scatterers. By rotating the three metal rods in opposite directions to break the inversion symmetry, we achieve a bandgap width of up to 70% and observe the transport of the edge states in the terahertz region. By replacing part of the structure with phase change material VO ₂ , on/off switching of the terahertz photonic topological edge states is realized, and the attenuation can be also modeled by adjusting the size of the VO ₂ region. The proposed regime has potential applications in sensing and 6G communications.