Polarization-selective nanogold absorber by twisted stacking

Metamaterial absorbers show great promise for applications in optical manipulation, photodetection, solar energy harvesting, and photocatalysis. In this work, we present a twisted stacked metamaterial design that serves as a plasmonic perfect absorber with polarization selectivity. Leveraging effective energy localization, the metamaterial realizes a near-unity absorbance of up to 99.6% for right circularly polarized incidence and 97.2% for left circularly polarized incidence. At a longer wavelength in the visible range, the chiral metamaterial becomes more sensitive to the polarization state of the incident wave, retaining an ultrahigh absorption of light (∼94%) for only a given polarization state, that is, light in this polarization state is effectively shielded. A giant circular dichroism signal of up to 7° can be simultaneously observed. Electromagnetic field and charge distribution simulations further reveal that the ultrahigh performance of the design is attributed to the interplay between cavity coupling, magnetic resonances, and plasmonic coupling. Besides switchable and tunable chirality, the plasmonic metamaterial presents a near-perfect absorption band with tunable operational wavelengths. We envision that the high-performance chiral gold metamaterial proposed here can serve as a good candidate for light trapping, chirality sensing, polarized light detection, and polarization-enhanced photocatalysis.