Circular dichroism induced by Fano resonances in planar chiral oligomers

TL;DR

This paper develops a theory showing how planar chiral nanostructures can exhibit controllable circular dichroism in absorption and scattering through modal interference and Fano resonances, independent of total optical loss.

Contribution

It introduces a general analytical framework linking circular dichroism to Fano resonances and modal interference in planar chiral nanostructures, enabling engineered polarization-dependent optical effects.

Findings

Circular dichroism can be controlled by incident polarization handedness.

Fano resonances enable strong polarization-dependent absorption and scattering.

Total optical loss remains polarization-independent despite dichroic effects.

Abstract

We present a general theory of circular dichroism in planar chiral nanostructures with rotational symmetry. It is demonstrated, analytically, that the handedness of the incident field's polarization can control whether a nanostructure induces either absorption or scattering losses, even when the total optical loss (extinction) is polarization-independent. We show that this effect is a consequence of modal interference so that strong circular dichroism in absorption and scattering can be engineered by combining Fano resonances with planar chiral nanoparticle clusters.