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<p>Mid-wave infrared circular dichroism filters have significant application prospects in fields such as circularly polarized thermal imaging, molecular sensing, and free-space optical communication. However, the circular dichroism of traditional metal chiral structures is usually not very high, which severely restricts the energy efficiency and practical application of devices. To address this bottleneck, this paper proposes and numerically verifies a highly efficient circular dichroism filter based on a bilayer metal chiral metasurface. This design achieves strong coupling enhancement in chiral optical responses by cooperatively regulating the in-plane twist angle and vertical spacing between the anisotropic metasurfaces of the upper and lower layers, breaking the mirror symmetry of the structure and exciting Fabry-Perot resonance modes. Simulation results show that the device achieves a circular dichroism value as high as 0.73 at a wavelength of 3.3&#xa0;μm, with a corresponding circular polarization extinction ratio of 150:1, significantly surpassing the performance limit of traditional metal chiral structures. The proposed bilayer twisted metasurface structure in this work is expected to play an important role in chiral light control, polarization coding, and integrated photonic devices in the mid-wave infrared band.</p>

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Design of high-efficiency mid-wave infrared circular dichroism filter based on double-layer metal chiral metasurfaces

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月7日

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  • Bo Cheng,
  • Hanxiao Shao,
  • Yuxiao Zou,
  • Longleng Lv,
  • Guofeng Song,
  • Kunpeng Zhai

摘要

Mid-wave infrared circular dichroism filters have significant application prospects in fields such as circularly polarized thermal imaging, molecular sensing, and free-space optical communication. However, the circular dichroism of traditional metal chiral structures is usually not very high, which severely restricts the energy efficiency and practical application of devices. To address this bottleneck, this paper proposes and numerically verifies a highly efficient circular dichroism filter based on a bilayer metal chiral metasurface. This design achieves strong coupling enhancement in chiral optical responses by cooperatively regulating the in-plane twist angle and vertical spacing between the anisotropic metasurfaces of the upper and lower layers, breaking the mirror symmetry of the structure and exciting Fabry-Perot resonance modes. Simulation results show that the device achieves a circular dichroism value as high as 0.73 at a wavelength of 3.3 μm, with a corresponding circular polarization extinction ratio of 150:1, significantly surpassing the performance limit of traditional metal chiral structures. The proposed bilayer twisted metasurface structure in this work is expected to play an important role in chiral light control, polarization coding, and integrated photonic devices in the mid-wave infrared band.