Chirality-selective transparency induced by lattice resonance in bilayer metasurfaces

Chiral optical responses of bilayer metasurfaces made of twisted metallic nanorods are investigated in detail with focus on the collective effect due to lattice resonance (LR). Using an analytical approach based on the coupled dipole method (supported by full wave simulation), we find optical chirality is dramatically increased by the coupling between localized surface plasmon resonances and LR. The collective effect results in significant chiral signal even for metasurfaces made of achiral unit cells. The interlayer coupling generally destroys the Wood's anomaly and the associated transparency. While making use of Pancharatnam-Berry (PB) phase and propagation phase, one can modulate the optical activity effectively and achieve chirality-selective transparency induced by LR in a designed structure with a g-factor of absorption as high as 1.99 (close to the upper limit of 2). Our studies not only reveal a new mechanism of modulating chiral optical response by combination effects from PB phase, propagation phase, and LR, but also give a quantitative relationship between the geometry configuration and chiral optical properties, thus providing helpful guidance for device design. (C) 2021 Chinese Laser Press

Automated summary

The study reveals that optical chirality can be significantly increased by coupling between localized surface plasmon resonances and lattice resonances, even for metasurfaces made of achiral unit cells. Interlayer coupling generally destroys Wood's anomaly and transparency. By utilizing Pancharatnam-Berry phase and propagation phase, chirality-selective transparency can be achieved in a designed structure with a high absorption g-factor close to the upper limit of 2.