Coupled edge states in sandwiched topological photonic structures

In this work, the coupling effect of topological edge states is investigated in sandwiched topological photonic structures. To this end, we first construct a topological photonic structure based on the two-dimensional Su-Schrieffer-Heeger square lattice, analyzing the existence form of the topological edge states along a single boundary between trivial and nontrivial regions. Subsequently, two kinds of sandwiched structures, i.e. symmetric and asymmetric structures, are built to investigate the coupling effect between two topological edge states. Numerical and theoretical results indicate that the coupling effect between two topological edge states leads to mode hybridization, thereby affecting the dispersion curves, the existence form, and transmission characteristic of the topological edge states. Our research findings may provide new ideas for the study of multimode topological photonics and also offer new methods for the manipulation of light.