Robust chirality via merging accidental BICs with net zero topological charge

Hui Hu; Chaobiao Zhou; Yukang Zhang; Meng-Xia Hu; Juntian Peng; Huawei Tang; Lujun Huang; Jianlong Liu; Chunying Guan; Zheng Zhu; Xiaoshuang Chen; Wei Lu; Xiangping Li; Zi-Lan Deng; Guanhai Li; Jinhui Shi; Cheng-Wei Qiu

doi:10.1186/s43593-026-00126-z

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Robust chirality via merging accidental BICs with net zero topological charge

eLight Vol. 6, (2026)

Research Article | Updated：2026-07-21

- Robust chirality via merging accidental BICs with net zero topological charge
- Affiliations：
- Author bio：
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- DOI：10.1186/s43593-026-00126-z
  CLC：
- Received：25 October 2025，
  
  Revised：2026-01-29，
  
  Accepted：04 February 2026，
  
  Online First：19 March 2026，
  
  Published：2026-12
- Accepted：
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Hui Hu, Chaobiao Zhou, Yukang Zhang, et al. Robust chirality via merging accidental BICs with net zero topological charge[J]. eLight, 2026, 6.
DOI：

Hui Hu, Chaobiao Zhou, Yukang Zhang, et al. Robust chirality via merging accidental BICs with net zero topological charge[J]. eLight, 2026, 6. DOI： 10.1186/s43593-026-00126-z.

摘要

Abstract

Chiral metasurfaces leveraging bound states in the continuum (BICs) offer a powerful route for enhancing light–matter interactions. However

existing quasi-BIC architectures typically face a fundamental

trade-off between high quality (Q) factors and wide-angle chiral operation. Most designs confine strong circular dichroism (CD) to isolated points in momentum space (k-space) and often rely on intricate three-dimensional (3D) meta-atoms

rendering them highly sensitive to fabrication imperfections and angular misalignment. Here

we experimentally realize a planar dielectric metasurface that supports a wide k-domain chirality arising from accidental BICs with a net zero-topological-charge (ZTC). By lifting a Dirac-type degeneracy through controlled in-plane and out-of-plane symmetry breaking

we induce a deterministic topological evolution in which the same-handed circularly polarized (C) points migrate toward and accumulate near the Γ point

while the opposite-handed singularities annihilate or shift to higher k-space. This mechanism delivers record-level performance—an ultrahigh Q-factor (~ 10

)

near-unity linear and nonlinear CD (0.99/0.999)

and robust angular coverage (|

/2π

/2π|

0.06)—all within a fabrication-friendly

single-layer dielectric platform. These results establish a new regime for chiral photonics

unifying high chiral purity

angular robustness

and topological stability in a scalable planar architecture.

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references

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