Nanoscale chirality enhancement using topology-designed three-dimensional dielectric nanogap antennas

We have explored, using topology optimization, three-dimensional (3D) chiral-nanogap antennas for circular-to-linear polarization conversion between far and near fields. The topology-designed 3D nanogap structures exhibit a giant chiral dissymmetry (g=−1.70) in gap-mode intensity against the handedness of the incident polarization. We have found that the linearly polarized gap field, designed for counterpropagating circularly polarized light, retains optical chirality localized at the subwavelength mode volume. With the nanoscale-chirality enhancement demonstrated, machine-aided designs of 3D chiral nanostructures offer a promising platform for amplifying chiral light-matter interactions with structured light at the nanoscale.