中国物理B ›› 2026, Vol. 35 ›› Issue (6): 67801-067801.doi: 10.1088/1674-1056/ae516d

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Double-layer cross-shaped cylinder terahertz all-dielectric metasurface with a high quality factor and giant chiral response governed by bound states in the continuum

Xinrui Guo(郭昕蕊)1, Jingwei Lv(吕靖薇)1,†, Chao Liu(刘超)1, Qin Yu(俞钦)2, Jianing Shi(时佳宁)1, Qiang Liu(刘强)1, Jianxin Wang(王建鑫)1, Wei Liu(刘伟)1, and Paul K. Chu(朱剑豪)3   

  1. 1 School of Physics and Electronic Engineering, Northeast Petroleum University, Daqing 163318, China;
    2 Dewert OKIN Technology Group Co., Ltd., Jiaxing 314015, China;
    3 Department of Physics, Department of Materials Science and Engineering, and Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
  • 收稿日期:2025-12-18 修回日期:2026-03-07 接受日期:2026-03-13 出版日期:2026-05-28 发布日期:2026-05-28
  • 通讯作者: Jingwei Lv E-mail:lvjingwei2009123@126.com
  • 基金资助:
    The work was jointly supported by the National Natural Science Foundation of China (Grant No. 12304480), Heilongjiang Provincial Natural Science Foundation of China (Grant No. JQ2023F001), and City University of Hong Kong Donation Research Grants, China (DON-RMG 9229021 and 9220061).

Double-layer cross-shaped cylinder terahertz all-dielectric metasurface with a high quality factor and giant chiral response governed by bound states in the continuum

Xinrui Guo(郭昕蕊)1, Jingwei Lv(吕靖薇)1,†, Chao Liu(刘超)1, Qin Yu(俞钦)2, Jianing Shi(时佳宁)1, Qiang Liu(刘强)1, Jianxin Wang(王建鑫)1, Wei Liu(刘伟)1, and Paul K. Chu(朱剑豪)3   

  1. 1 School of Physics and Electronic Engineering, Northeast Petroleum University, Daqing 163318, China;
    2 Dewert OKIN Technology Group Co., Ltd., Jiaxing 314015, China;
    3 Department of Physics, Department of Materials Science and Engineering, and Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
  • Received:2025-12-18 Revised:2026-03-07 Accepted:2026-03-13 Online:2026-05-28 Published:2026-05-28
  • Contact: Jingwei Lv E-mail:lvjingwei2009123@126.com
  • Supported by:
    The work was jointly supported by the National Natural Science Foundation of China (Grant No. 12304480), Heilongjiang Provincial Natural Science Foundation of China (Grant No. JQ2023F001), and City University of Hong Kong Donation Research Grants, China (DON-RMG 9229021 and 9220061).

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摘要： The combination of high-quality-factor ($Q$-factor) bound states in the continuum (BIC) and chiral metasurfaces has attracted much attention in the field of photonics. Here, we design and analyze a “sandwich” all-dielectric metasurface with two silicon cross-shaped cylinders distributed on the upper and lower surfaces of the silica. The transition from symmetry-protected BIC to chiral quasi-BIC (QBIC) is achieved by innovatively breaking both the mirror symmetry and the in-plane inversion symmetry of the structure, resulting in a transmittance-ratio circular dichroism (RCD) close to unity and a high $Q$-factor. In particular, three chiral QBICs (QBIC1, QBIC2, and QBIC3) are realized in the terahertz band without increasing the complexity of the structure at each layer. Multipole decomposition and near-field analysis demonstrate that QBIC1 and QBIC2 are dominated by the toroidal dipole and magnetic quadrupole, while QBIC3 is mainly affected by the electric quadrupole and magnetic quadrupole. In addition, the presence of positive and negative states due to the RCD values of the structure suggests a spin selectivity for different frequency bands. Theoretical assessment shows a maximum $Q$-factor of 3.94$\times10^{4}$, a maximum sensitivity of 245 GHz per refractive index unit (RIU), and a figure of merit of 7927 RIU$^{-1}$. The results reveal a novel approach for selectively modulating circularly polarized light, demonstrating significant potential in biomolecular detection, high-spectral-resolution chiral biosensors, and chemical analysis.

关键词: chiral quasi bound states in the continuum (QBIC), all-dielectric metasurfaces, circular dichroism, sandwich structure

Abstract: The combination of high-quality-factor ($Q$-factor) bound states in the continuum (BIC) and chiral metasurfaces has attracted much attention in the field of photonics. Here, we design and analyze a “sandwich” all-dielectric metasurface with two silicon cross-shaped cylinders distributed on the upper and lower surfaces of the silica. The transition from symmetry-protected BIC to chiral quasi-BIC (QBIC) is achieved by innovatively breaking both the mirror symmetry and the in-plane inversion symmetry of the structure, resulting in a transmittance-ratio circular dichroism (RCD) close to unity and a high $Q$-factor. In particular, three chiral QBICs (QBIC1, QBIC2, and QBIC3) are realized in the terahertz band without increasing the complexity of the structure at each layer. Multipole decomposition and near-field analysis demonstrate that QBIC1 and QBIC2 are dominated by the toroidal dipole and magnetic quadrupole, while QBIC3 is mainly affected by the electric quadrupole and magnetic quadrupole. In addition, the presence of positive and negative states due to the RCD values of the structure suggests a spin selectivity for different frequency bands. Theoretical assessment shows a maximum $Q$-factor of 3.94$\times10^{4}$, a maximum sensitivity of 245 GHz per refractive index unit (RIU), and a figure of merit of 7927 RIU$^{-1}$. The results reveal a novel approach for selectively modulating circularly polarized light, demonstrating significant potential in biomolecular detection, high-spectral-resolution chiral biosensors, and chemical analysis.

Key words: chiral quasi bound states in the continuum (QBIC), all-dielectric metasurfaces, circular dichroism, sandwich structure

中图分类号:  (Multilayers; superlattices; photonic structures; metamaterials)

  • 78.67.Pt
42.25.Ja (Polarization) 33.55.+b (Optical activity and dichroism)