Orbital angular momentum dichroism caused by the interaction of electric-magnetic dipole moments in chiral metal nanoparticles

TL;DR

This study investigates how light with orbital angular momentum influences circular dichroism in chiral plasmonic nanoparticles, revealing enhanced dichroism due to electric-magnetic mode interactions and partial spatial excitation.

Contribution

It introduces a numerical analysis of orbital angular momentum effects on dichroism in chiral plasmonic structures, highlighting the role of electric-magnetic mode interactions.

Findings

Enhanced circular dichroism with vortex beams and spin angular momentum.

Dichroism attributed to electric-magnetic mode interactions and higher-order modes.

Partial excitation of nanoparticles influences the dichroic response.

Abstract

Circular dichroism (CD) caused by the response of a chiral object to circularly polarized light has been well established, and the strong CD of plasmonic meta-molecules has also become of interest in recent years; however, their response if the light also has orbital angular momentum is unclear. In this paper, the dichroism of a plasmonic cuboid-protuberance chiral structure under the illumination of a light beam with both orbital and spin angular momentums is numerically investigated. Distinguished spectra are observed under the different momentums. The circular dichroism under the combination of vortex beam and light spin is enhanced. This phenomenon is attributed to the partial spatial excitation of the nanoparticle, and the strong dichroism is simultaneously caused because of the interaction of the induced electric and magnetic modes and other higher-order modes caused by the partial excitation of the vortex beam. This research provides further insight into chiral light-matter interactions and the dichroism of light with orbital angular momentum.