Symmetry-Breaking-Induced Quasi-Bound States in the Continuum in All-Dielectric Terahertz Metasurface for High-Sensitivity Refractive Index Sensing and Theoretical Virus Differentiation

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Abstract
Bound states in the continuum (BIC) have recently attracted extensive research interest, owing to their exceptional capability for light confinement and high quality-factor (Q-factor) resonances. In this work, we design an all-dielectric terahertz metasurface based on the symmetry-breaking properties of silicon rectangular pillars. Numerical simulations demonstrate that breaking the in-plane inversion (C2) symmetry transforms the BIC into a quasi-BIC (q-BIC), which features a high Q-factor and a narrow resonance linewidth. Through far-field multipole decomposition and near-field electromagnetic field distribution analysis, the excitation mechanism of the q-BIC mode is elucidated, revealing that the magnetic dipole (MD) contribution remains predominant over a certain range of asymmetry. Furthermore, the q-BIC resonance exhibits high sensitivity to the change in refractive index, achieving a theoretical sensitivity of 110 GHz/RIU even with an analyte thickness of only 15 μm. When MS2 and PRD1 bacteriophages are employed as model analytes with distinct effective refractive indices, the sensor produces a larger resonance frequency shift for MS2 than for PRD1, demonstrating its capability for theoretical dielectric discrimination based on refractive index differences. These findings provide a valuable reference for the development of all-dielectric terahertz metasurface platforms for label-free refractive index sensing and model virus differentiation.
Funding Information
  • National Natural Science Foundation of China (62605179)
  • National Natural Science Foundation of China (62475121)
  • National Natural Science Foundation of China (62435010)
  • National Natural Science Foundation of China (62165006)
  • Jiangxi Provincial Department of Science and Technology (20262BAC260001)
  • Jiangxi Provincial Department of Science and Technology (20252BEJ730361)
  • Jiangxi Provincial Department of Science and Technology (20242BAB20065)
  • Jiangxi Provincial Department of Science and Technology (20224ACB202004)
  • Jiangxi Province Ganpo Juncai Support Plan—High-Level and High-Skilled Leading Talent Training Project (2024–069)
  • Key Research and Development Program Project of Jiangxi Province (20243BBI91011)
  • Science and Technology Project Foundation of the Education Department of Jiangxi Province (GJJ2401207)
  • Nanchang City Key Laboratory of Optic-electronic Detection and Information Processing (2019-NCZDSY−008)
  • Jiangxi Science and Technology Normal University (2024BSQD39)
  • Jiangxi Science and Technology Normal University (2022BSQD02)

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