Chirality in Nature and Science

Abstract

Geometrical chirality in molecules or plasmonic nanostructures can lead to unique optical responses such as circular dichroism or optical rotatory dispersion. It is important to distinguish between such chiral responses and the underlying chiral geometry. In this chapter, we first discuss the geometrical properties of chiral objects from a mathematical point of view including planar chirality, the quantification of chirality, and different handedness definitions. After a short introduction to localized plasmons, we thoroughly derive the electromagnetic properties of geometrically chiral objects. Starting from the Born-Kuhn model for chiral media, we derive the chiral constitutive equations and, subsequently, the chiral wave equation. This wave equation provides the basis for a theoretical discussion of the resulting chiral far-field responses. Exemplary, we analyze the circular dichroism response of sugars and simple plasmonic nanostructures. Additionally, a short review of modern techniques for the fabrication of chiral plasmonic nanostructures is given.