Strategies for Guiding Directional Topological Waveguides With Symmetric Regularity

The advantageous characteristics of topological photonic crystals facilitate the directional manipulation of waveguides. In this study, we propose a topological photonic crystal that breaks C₄ symmetry through rotation, resulting in a symmetric gradient of topological edge state frequencies in both vertical and horizontal directions, thereby enabling precise control over the direction of the edge states. We developed two types of three-channel composite devices informed by our analysis of the transmission characteristics of photonic crystal arrays. These application were experimentally demonstrated in this study. We also construct an eight-path optical device in which topological edge states appear in succession with decreasing wavelengths. These regular transmission waveguides offer new opportunities for device design and the realization of multifunctional effects.