Circular dichroism in gold helix metamaterials and gold gyroid structures at optical frequencies

Using the finite-difference time-domain method, we investigate the polarization properties of artificially designed chiral metamaterials such as helix and gyroid structures. With regards to the helix metamaterial, we show how the band structure clearly explains the circular polarization dependency of the transmission along the chiral axis. Complementary to the numerical calculations, we introduce a new analytical model that exploits similarities in the chiral properties of helix and gyroid metamaterials to provide a basis for future theoretical work on complex gyroid metamaterials. A comparison between the band structures of dielectric and gold gyroid structures also reveals strong light-matter interaction similar to plasmonic excitations as well as its potential application at optical frequencies.