Waveguide–Cavity Coupling System Based on Topological Edge States and Corner States in Kagome Photonic Crystals

Abstract In recent years, the topological edge states (TESs) and topological corner states (TCSs) based on high‐order topological photonic insulators have been researched and applied in various fields. Among them, the combination of topological photonics and waveguide–cavity coupling system has attracted much attention of researchers. In this paper, TESs and TCSs based on Kagome lattice photonic crystals (PCs) with rectangular dielectric columns are obtained. In addition, a topological waveguide–cavity coupling system is proposed, realizing the energy coupling between the TES waveguide and the TCS cavity. To further improve the performance of the system, a sandwich‐like waveguide and an extended waveguide are used to replace the original TES waveguide. Interestingly, the proposed extended waveguide–cavity coupling system cannot only achieve the excitation of two TCSs at different frequencies, but also has stronger electric field intensity, narrower resonance bandwidth, and higher quality factor than the other structures. This work provides a new path to design high‐performance micro‐nanointegrated optical devices such as filters, lasers, and resonators.