Unidirectional Wave Propagation in a Topological Plasmonic Ring Resonator via a Symmetry-Broken Excitation Scheme

Topological plasmonics provide insights for the manipulation of light. Analogous to the exotic nature of topological edge states in topological photonics, topological plasmonics combine concepts from topology and plasmonics. By utilizing topological protection, plasmons can be made to propagate without significant scattering or decay, even in the presence of nano- or mesoscale defects or disorders. Herein, we present a study of the design, characterization, and manipulation of topological plasmonic chains of nanodiscs based on the Su–Schrieffer–Heeger model made into a ring geometry. The investigation focuses on exploring the unique properties of these resonators and their potential to support topologically protected edge modes within the continuum of rotationally symmetric optical modes of a ring. To observe the topological edge modes in rotationally symmetric chains, we employed a symmetry-breaking excitation technique based on electron beams. It analyzes the influence of parameters, such as dimerization and loop numbers, on the presence of topological modes. Additionally, we explore the manipulation of electron impact positions to control the direction of propagation and selectively excite specific bulk or edge modes. The findings contribute to a deeper understanding of topological effects by numerically investigating their design principles and exploring techniques to manipulate topological edge modes. The insights gained from this study have implications for the development of nanoscale plasmonic systems with customized functionalities. These findings potentially impact various areas, including nanophotonics, nanosensing (e.g., biosensors and chemical detection), as well as nanooptical communication components, such as nanowaveguides, resonators, modulators, and quantum information processing.