Transition radiation in photonic topological crystals: quasi-resonant excitation of robust edge states by a moving charge

Abstract

We demonstrate, theoretically and experimentally, that a traveling electric charge passing from one photonic crystal into another generates edge waves -- electromagnetic modes with frequencies inside the common photonic bandgap localized at the interface -- via a process of transition edge-wave radiation (TER). A simple and intuitive expression for the TER spectral density is derived and then applied to a specific structure: two interfacing photonic topological insulators with opposite spin-Chern indices. We show that TER breaks the time-reversal symmetry and enables valley- and spin-polarized generation of topologically protected edge waves propagating in one or both directions along the interface. Experimental measurements at the Argonne Wakefield Accelerator Facility are consistent with the excitation and localization of the edge waves. The concept of TER paves the way for novel particle accelerators and detectors.

arXiv comment6 pages, 3 figures

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Cited by in corpus (4)

• Observation of enhanced free-electron radiation from photonic flatband resonances
• Modification of transition radiation by three-dimensional topological insulators
• Development and high-power testing of an X-band dielectric-loaded power extractor
• Free-electron radiation engineering via structured environments