Effects of Fano resonance on optical chirality of planar plasmonic nanodevices

TL;DR

This study demonstrates how Fano resonance influences the optical chirality of planar plasmonic nanodevices, revealing a switch in circular polarization preference, with experimental and theoretical insights enabling better control of chiral nanostructures.

Contribution

It provides the first experimental observation and theoretical explanation of Fano resonance effects on optical chirality in planar plasmonic nanodevices.

Findings

Fano resonance causes a change in circular polarization preference.

Experimental and theoretical analysis confirms the effect.

Enhanced control over chiral nanodevice properties.

Abstract

The effects of Fano resonance on the optical chirality of planar plasmonic nanodevices in the visible wavelength range are experimentally observed and theoretically explained. The nanodevice consists of a nanodisk at the center with six gold nanorods with an orientation angle to exhibit optical chirality under dark-field illumination. The chiral response induced by the gold nanorods are affected by the presence of the nanodisk with different diameters which causes Fano resonance. An intriguing change to the opposite selection preference of different handedness of the circularly polarized light has been clearly observed experimentally. This change of the preference is understood based on the extended coupled oscillator model. Moreover, electrostatic analysis and the time-dependent simulations provide a further understanding of the phenomenon. The observed and understood effects of Fano resonance on optical chirality enables effective manipulation of chiral characteristics of planar subwavelength nanodevices.