Controlling metamaterial transparency with superchiral fields

The advent of metamaterials has heralded a period of unprecedented control of light. The optical responses of metamaterials are determined by the properties of constituent nanostructures. The current design philosophy for tailoring metamaterial functionality is to use geometry to control the nearfield coupling of the elements of the nanostructures. A drawback of this geometry-focused strategy is that the functionality of a metamaterial is pre-determined and cannot be manipulated easily post-fabrication. Here we present a new design paradigm for metamaterials, in which the coupling between chiral elements of a nanostructure is controlled by the chiral asymmetries of the nearfield, which can be externally manipulated. We call this mechanism dichroic coupling. This phenomenon is used to control the electromagnetic induced transparency displayed by a chiral metamaterial by tuning the chirality of the near fields. This “non-geometric” paradigm for controlling optical properties offers the opportunity to optimally design chiral metamaterials for applications in polarization state control and for ultrasensitive analysis of biomaterials and soft matter.