Babinet to the half: coupling of solid and inverse plasmonic structures

We study the coupling between the plasmonic resonances of solid and inverse metallic nanostructures. While the coupling between solid-solid and inverse-inverse plasmonic structures is well-understood, mixed solid-inverse systems have not yet been studied in detail. In particular, it remains unclear whether or not an efficient coupling is even possible and which prerequisites have to be met. We find that an efficient coupling between inverse and solid resonances is indeed possible, identify the necessary geometrical prerequisites, and demonstrate a novel solid-inverse plasmonic electromagnetically induced transparency (EIT) structure as well as a mixed chiral system. We furthermore show that for the coupling of asymmetric rod-shaped inverse and solid structures symmetry breaking is crucial. In contrast, highly symmetric structures such as nanodisks and nanoholes are straightforward to couple. Our results constitute a significant extension of the plasmonic coupling toolkit, and we thus envision the emergence of a large number of intriguing novel plasmonic coupling phenomena in mixed solid-inverse structures.