Coupling-Controlled Photonic Topological Ring Array

Photonic topological insulators with boundary states present a robust solution to mitigate structure imperfections. By alteration of the virtual boundary between trivial and topological insulators, it is possible to bypass such defects. Coupled resonator optical waveguides (CROWs) have demonstrated their utility in realizing photonic topological insulators, as they exhibit distinct topological phases and band structures. With this characteristic, we designed and experimentally validated a CROW array capable of altering its topological phase by adjusting the coupling strength. This array functions partially as a topological insulator and partially as a topologically trivial array, guiding light along the virtuous boundary between these two regions. By altering the shape of the topological insulator, we can effectively control the optical path. This approach promises practical applications, such as optical switches, dynamic light steering, optical sensing, and optical computing.