Chiral effects in low-cost plasmonic arrays of elliptic nanoholes

In this work we present an approach to induce chiral effects in well-known plasmonic nanohole arrays with triangular unit cell. Arrays with circular nanoholes in metals can exhibit interesting light-matter interaction mechanisms such as surface plasmon polaritons and extraordinary optical transmission. Moving from circular to elliptical shape and tilting the ellipse away from the lattice symmetry lines, a symmetry breaking induces a different absorption of the circularly polarized light of opposite handedness, i.e. circular dichroism. We numerically investigate circular dichroism at normal incidence in elliptic nanoholes in Au in the spectral range 400–1000 nm. We focus on its dependence on the elliptic nanohole tilt, and further proceed with the ellipse radii optimization. The optimized circular dichroism reaches 84%, and we report on the near field absorption distribution at the wavelengths of this maximum value.