Achieving asymmetry parameter‐insensitive resonant modes through relative shift–induced quasi‐bound states in the continuum

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Abstract
High‐Q resonances in metasurfaces, stemming from symmetry‐protected bound states in the continuum (BICs), have proven to be effective for achieving high‐performance optical devices. However, the properties associated with symmetry‐protected BICs are inherently limited, as even a slight variation in the asymmetry parameter leads to a noticeable shift in the resonance location. Herein, we introduce the concept of relative shift–induced quasi‐BICs (QBICs) within dimerized silicon (Si) meta‐lattices (DSMs), which can be excited when a nonzero relative shift occurs, a result of in‐plane inversion symmetry breaking and Brillouin zone folding within the structure. These QBICs have resonance locations that remain insensitive to variations in asymmetrical parameters. Additionally, their Q‐factors can be flexibly tuned, benefiting from the inverse square dependence on asymmetrical parameters. In experiment, six DSMs with different relative shifts are fabricated and the asymmetry parameter‐insensitive resonant modes under two orthogonal polarization states are experimentally observed in the optical communication waveband. Our results offer unique opportunities for constructing high‐Q resonators with enhanced performances, which can be applied in various optical fields.
Funding Information
  • National Natural Science Foundation of China (62375113)

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