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Intrinsic chiral optical vortex emission from the interactions between free electrons with bound states in the continuum

Jing Li1,2,3,*, Zihan Wang1,2,*, Wu Wen1,2, Haoyu Mo1,2, Qingyao Liang1,2, Tianxiang Hong1,2, Yuhan Jiang1,2, and Yunquan Liu1,2,3,4,5,†

  • *These authors contributed equally to this work.
  • †Contact author: Yunquan.liu@pku.edu.cn
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Phys. Rev. Research 7, 043049 – Published 15 October, 2025

DOI: https://doi.org/10.1103/9jmn-z1fj

Abstract

We present an approach for free-electron-driven optical vortex emission through interaction with the quasi-bound states in the continuum (quasi-BICs). Based on a unified framework for free electron-nanophotonic interaction and time domain simulations, we show that the free electron beam can efficiently excite the quasi-BIC under the phase-matching condition. The intrinsic k-space polarization anisotropy associated with the quasi-BIC imprints a geometric phase onto the emission, and thus generates an intrinsic optical vortex. We then reveal a link between the topological charge of the quasi-BIC and the emitted optical vortex by analyzing the far-field polarization structure and phase distribution. This mechanism offers a promising approach to creating nanoscale electron-beam-driven structured light sources without the need for complex chiral nanostructures, thereby advancing the interdisciplinary study of free-electron optics and nanophotonics.

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Phys. Rev. Research 7, 043049– Published 15 October, 2025
  • Received 7 January 2025
  • Accepted 25 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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