Sandwich-Type Planar Chiral Metamaterials for Tuning Circular Dichroism

Chiral metasurfaces exhibit significant circular dichroism (CD) and chiral signal enhancement, which has the potential to be used in novel nano-optical devices. This work describes a bilayer resonant planar chiral metasurface (PCM) composed of И and N-shaped gold nanoparticles. It is found that in the near-infrared region, the structure has obvious optical active and chiral near-field enhancement. To explore the origin of chirality, linear superposition theory is applied to analyze chiral response intuitively and concisely. What’s more, the dependence of the CD spectra on the PCM parameters was thoroughly explored, showing that the CD properties of the proposed PCM arrays strongly depend on the geometric parameters and material type. The bilayer PCM array proposed in this paper not only has a strong chiral signal but also is easy to prepare experimentally. More importantly, the spectrum of PCM can be adjusted by simply adjusting the particle rotation angle and changing the material of the dielectric layer, which has broad potential application prospects in the fields of chiral molecular biosensing and asymmetric information transmission.