Helical Plasmonic Nanostructures as Prototypical Chiral Near-Field Sources

Plasmonic nanostructures can generate electromagnetic fields with high optical chirality that interact strongly with chiral molecules. We demonstrate how structures with chiral eigenmodes lead to chiral near-fields of predominantly one handedness. Our theoretical design with multiple metallic helices exhibits very high optical chirality over a large volume. The expected averaged chiroptical interaction is almost 2 orders of magnitude higher than for circularly polarized light.