Chirality and chiroptical effects in plasmonic nanostructures: Fundamentals, recent progress, and outlook

Strong chiroptical effects recently reported result from the interaction of light with chiral plasmonic nanostructures. Such nanostructures can be used to enhance the chiroptical response of chiral molecules and could also significantly increase the enantiomeric excess of direct asymmetric synthesis and catalysis. Moreover, in optical metamaterials, chirality leads to negative refractive index and all the promising applications thereof. In this Progress Report, we highlight four different strategies which have been used to achieve giant chiroptical effects in chiral nanostructures. These strategies consecutively highlight the importance of chirality in the nanostructures (for linear and nonlinear chiroptical effects), in the experimental setup and in the light itself. Because, in the future, manipulating chirality will play an important role, we present two examples of chiral switches. Whereas in the first one, switching the chirality of incoming light causes a reversal of the handedness in the nanostructures, in the second one, switching the handedness of the nanostructures causes a reversal in the chirality of outgoing light. Due to the recent development of bottom-up and top-down approaches for material design and fabrication at the nanoscale, giant chiroptical effects have been reported from plasmonic nanostructures. These effects are exhibited both in the linear and in the nonlinear optical regimes and are sensitive to the chirality of nanostructures, the chirality of the experiments and the chirality of light itself.