Broadband Circular Polarizers Via Coupling In 3d Plasmonic Meta-Atom Arrays

We report broadband circular polarizers achieved by engineering the electromagnetic coupling between 3D meta-atoms in large-area arrays. The 3D meta-atoms are composed of bulk Au/Au nanocrystal (NC) bilayer helical arms, tailored in their number, length, and curvature through a one-step patterning process and postfabrication chemical and thermal treatments. By tuning the meta-atom array periodicity, hybridization originating from dipole-dipole and quadrupole-quadrupole interactions broadens the chiral response. We demonstrate circular polarizers operating at wavelengths spanning 2.5 to 5 mu m, with a maximal transmission difference between left- and right-hand circularly polarized light of 43%.