Photonic realization of non-Hermitian skin effect using topological ring cavities

Abstract

Non-Hermitian skin effect (NHSE) describes that all eigenmodes of a non-Hermitian Hamiltonian are located at the boundary of the system. Being one of the key characteristics of non-Hermitian physics, the realization of NHSE could pave the road to future applications. In this work, in analogy to the Hatano-Nelson (HN) model, we successfully construct a feasible design of photonic NHSE by using the topological ring cavities composed of photonic crystals with distinct topological properties, where the topological interface states replace the bulk states in HN model. By introducing material loss into the linkers, we propose a feasible way to tune the non-reciprocal coupling between topological ring cavities as well as the corresponding NHSE. The localization of topological interface states can be influenced by NHSE whose localization strength can be manipulated with the difference of material losses introduced. Owing to its topology nature, we verify the robustness of the proposed structure against local defects. Our proposal can also be extended to two-dimensional (2D) NHSE and higher-ordered NHSE, where we believe it will be an ideal platform to study non-Hermitian physics and intriguing applications in topological photonics.