Reconfigurable Photonic Valley Filter in Hybrid Topological Heterostructures

Abstract Topological photonics has emerged as an important branch of photonics for its excellent ability to robustly manipulate light. As a widely used topological photonic platform, valley photonic crystals have attracted great attention recently due to the unique opportunities the valley degree of freedom provides to potentially encode and process binary photonic information. However, an efficient and controllable way to generate pure valley current is still lacking. Here, a perfect photonic valley filter with on‐demand routing and switching functionalities by exploiting the unique physics of magneto‐optic and valley photonic crystal is proposed. Particularly, an additional width degree of freedom is introduced by inserting an intermediate layer with matched Dirac points at specific valleys between two domains of topologically distinct photonic crystals. The resultant three‐layer topological heterostructures support large‐area valley polarized states with tunable mode width. Moreover, perfect photonic valley filters to generate and guide the pure valley current through reconfigurable propagation paths by only changing the directions of external magnetic fields are also demonstrated. The work not only lays a solid foundation on the principle and design of photonic valley filters, the great reconfigurability of the design also provides broad application prospects in photonic integrated networks and on‐chip integrated communication systems.