Chiral Optical Properties of Plasmonic Kagome Lattices

Kagome lattices can be considered hexagonal lattices with a three-nanoparticle unit cell whose symmetry may lead to the formation of higher-order topological states. This work reports the emergence of polarization-dependent features in the optical band structures of plasmonic Kagome lattices through lattice engineering. By expanding the separations between particles in a unit cell while preserving lattice spacing, we observed additional modes at the K-points of aluminum nanoparticle Kagome lattices. As the rotational symmetry was reduced from 6- to 3-fold, a splitting at the K-point was observed as well as the presence of an additional surface lattice resonance (SLR) band under linear polarization. This SLR band also exhibited a chiral response that depended on the direction of circularly polarized light and resulted in asymmetry in the optical band structure. The polarization-dependent response of plasmonic Kagome lattices can inform the design of systems that support topological states at visible wavelengths.