Tunable plasmonic chirality via an out-of-plane plasmonic system

In this paper, the property of a chiral plasmonic metasurface with a rectangle-semicircular-notched nanostructure in the visible region is investigated. By varying the offset height of chiral plasmonic structures, we can manipulate and tune the chiral optical response and coupling between the structure and the incident light. The maximum circular dichroism (CD) of up to 0.91, reciprocal switching between chiral and achiral, and the near-perfect absorption have been verified with numerical simulation using the finite element method. Furthermore, we find that this structure can also operate for CD and circular polarization filtering by adjusting the geometric parameter of the structure and the surrounding environment. This property can be extended to various rectangle-circular-based nanostructures. The effect originates from the internal abundant resonant modes of the equivalent dipole in the formation of chirality. This work opens up new possibilities, to our knowledge, for fabricating chirality-functional devices, such as chiral sensing.