Dual-band angular dispersion and polarization manipulation based on extrinsic chirality in a metasurface

This paper presents a metasurface with dual-band extrinsic chirality based on a metal-insulator-metal (MIM) structure. The metasurface utilizes mirror-symmetric split-ring resonators as fundamental building blocks. Under oblique microwave incidence, the in-plane mirror symmetry is effectively broken, inducing chiral electromagnetic resonance modes at two distinct frequencies. The selective coupling and suppression of left- and right-handed circularly polarized waves by the meta-atoms generate strong circular dichroism with opposite signs at the two frequencies. Concurrently, the different sensitivities of the resonant modes to incident angle variations result in mirror-symmetric frequency shifts for the two cross-polarization components within the bands, enabling flexible angular dispersion control. Under TM-polarized wave incidence, varying the incident and azimuth angles can excite significant phase dispersion, leading to rich polarization state evolution over the entire Poincaré sphere across the entire operating frequency band. By introducing the "incident angle" as a control dimension, this work provides a new, to the best of our knowledge, approach for multi-band, reconfigurable chiral responses and dynamic polarization manipulation, holding significant promise for applications in electromagnetic communication, polarization imaging, and related fields.