Three-dimensional chiral meta-atoms

We show that the chirality of artificial media, made of a planar periodic arrangement of three-dimensional metallic meta-atoms, can be tailored. The meta-atoms support localized plasmon polaritons and exhibit a chirality exceeding that of pseudo-planar chiral metamaterials by an order of magnitude. Two design approaches are investigated in detail. The first is the referential example for a chiral structure, namely a Moebius strip. The second example is a cut wire - split-ring resonator geometry that can be manufactured with state-of-the-art nanofabrication technologies. Driven into resonance these meta-atoms evoke a polarization rotation of $30^\circ$ per unit cell.