ИСТИНА

The concept of extrinsic chirality, i.e. optical activity of nonchiral media exhibited at oblique illumination, is generalized to include single-particle plasmonic nanostructures. We observe circular dichroism in irregular arrays of two dierent types of metallic nanostructures, non-concentric rings and asymmetrically stacked disks, in the visible and near-infrared regions. By using computer simulations, we show that extrinsic chirality in these systems is, importantly, due to individual nonchiral particles. We propose a mechanism for the chiroptical response of single-particle plasmonic structures.