Observation of the Inherent Chiral Smith-Purcell Effect via Symmetry Breaking

Juan-Feng Zhu; Fei Chen; Jun-Xuan Chen; Junkang Shan; Ayan Nussupbekov; Febiana Tjiptoharsono; Xuan Dong; Mu Wang; Cheng-Wei Qiu; Zhaogang Dong; Ruwen Peng; Lin Wu

arXiv · 2605.26587

Observation of the Inherent Chiral Smith-Purcell Effect via Symmetry Breaking

Juan-Feng Zhu·Fei Chen·Jun-Xuan Chen·Junkang Shan·Ayan Nussupbekov·Febiana Tjiptoharsono·Xuan Dong·Mu Wang·Cheng-Wei Qiu·Zhaogang Dong·Ruwen Peng·Lin Wu

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Abstract

The Smith-Purcell effect arises when charged particles move near a periodic structure, emitting radiation. Conventional approaches for generating chiral Smith-Purcell radiation rely on metasurface phase engineering or resonant mode interference, typically producing narrow-band, weakly chiral emission. Here, we introduce a resonance-interference-free mechanism that leverages the properties of the charged particles themselves. Using a non-chiral, non-resonant silicon grating, we demonstrate broadband, tunable Smith-Purcell radiation with high chirality, achieving a record-high degree of polarization of 0.87. This is enabled by converting the transverse spin angular momentum of electron-induced evanescent waves into a longitudinal form, producing opposite chirality at different azimuthal angles. Beam twisting or displacement offers precise control over chirality, paving the way for compact chiral light sources, advanced X-ray imaging, and integrated particle diagnostics platforms.

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Juan-Feng Zhu, Fei Chen, Jun-Xuan Chen, Junkang Shan, Ayan Nussupbekov, Febiana Tjiptoharsono, Xuan Dong, Mu Wang, Cheng-Wei Qiu, Zhaogang Dong, Ruwen Peng, Lin Wu. 2026-05-26. Observation of the Inherent Chiral Smith-Purcell Effect via Symmetry Breaking. https://arxiv.org/abs/2605.26587

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