Chiral Optical Properties of Plasmonic Kagome Lattices

Abstract

Kagome\nlattices can be considered hexagonal lattices with a three-nanoparticle\nunit cell whose symmetry may lead to the formation of higher-order\ntopological states. This work reports the emergence of polarization-dependent\nfeatures in the optical band structures of plasmonic Kagome lattices\nthrough lattice engineering. By expanding the separations between\nparticles in a unit cell while preserving lattice spacing, we observed\nadditional modes at the <i>K</i>-points of aluminum nanoparticle\nKagome lattices. As the rotational symmetry was reduced from 6- to\n3-fold, a splitting at the <i>K</i>-point was observed as\nwell as the presence of an additional surface lattice resonance (SLR)\nband under linear polarization. This SLR band also exhibited a chiral\nresponse that depended on the direction of circularly polarized light\nand resulted in asymmetry in the optical band structure. The polarization-dependent\nresponse of plasmonic Kagome lattices can inform the design of systems\nthat support topological states at visible wavelengths.