Angularly Tunable Circular Dichroism in a Bilayer Plasmonic Metasurface via Interlayer Coupling

We present a theoretical and computational study of a bilayer scythe-shaped metasurface designed to enhance chiroptical responses in the near-infrared region. The structure demonstrates pronounced differences in transmittance for left- and right-circularly polarized (LCP and RCP) light, directly related to the interlayer rotation angle. We show that circular dichroism (CD) increases with this rotation angle, reaching a maximum at 24°, indicating a significant enhancement of the chiral light-matter interaction at this specific geometry. Detailed analysis of the electric field distribution reveals distinct patterns for LCP and RCP light, providing insight into the underlying mechanism of the enhanced chiroptical response. Specifically, LCP light exhibits a stronger electric field intensity along the edges of the scythe meta-atoms compared to RCP light. Furthermore, the CD value increases as the interlayer distance decreases, highlighting the crucial role of interlayer coupling in enhancing the chiroptical performance. These results demonstrate that the chiroptical response of the bilayer and synthetic metasurface can be precisely controlled through its geometric parameters. This control enables the design of novel metasurfaces with potential applications in advanced nanophotonics, chiral sensing, and polarization control. The ability to tailor the chiroptical response by adjusting the metasurface configuration opens new avenues for developing compact and efficient optical devices.