Chiral light by symmetric optical antennas

TL;DR

This paper demonstrates that symmetric optical nanoantennas can produce circular dichroism, challenging the traditional view that chirality is necessary, with implications across biology, chemistry, and materials science.

Contribution

It reveals that simple symmetric nanoantennas can generate circular dichroism through phase-lagged dipole modes, expanding the understanding of chiral light interactions.

Findings

Symmetric nanoantennas can produce circular dichroism.

Two dipole-like modes with phase lag suffice for dichroism.

Experimental and theoretical validation of the phenomenon.

Abstract

Chirality is at the origin of life and is ubiquitous in nature. An object is deemed chiral if it is non-superimposable with its own mirror image. This relates to how circularly polarized light interacts with such object, a circular dichroism, the differential absorption of right and left circularly polarized light. According to the common understanding in biology, chemistry and physics, the circular dichroism results from an internal chiral structure or external symmetry breaking by illumination. We show that circular dichroism is possible with simple symmetric optical nanoantennas at symmetric illumination. We experimentally and theoretically demonstrate that two electromagnetic dipole-like modes with a phase lag, in principle, suffice to produce circular dichroism in achiral structure. Examples of the latter are all visible spectrum optical nanoantennas, symmetric nanoellipses and nanodimers. The simplicity and generality of this finding reveal a whole new significance of the electromagnetic design at a nanoscale with potential far reaching implications for optics in biology, chemistry and materials science.