On the differences between helicity and chirality

Mackinnon, N. (2019) On the differences between helicity and chirality. Journal of Optics, 21(12), 125402. (doi: 10.1088/2040-8986/ab4db9)

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Abstract

The optical helicity and the optical chirality are two quantities that are used to describe chiral electromagnetic fields. In a monochromatic field, the two quantities are proportional to one another, and the distinction between the two is therefore largely unimportant. However, in a polychromatic field, no such proportionality holds. This paper explicitly examines both the helicity and chirality densities in various polychromatic fields: the superposition of two circularly polarised plane-waves of different frequencies, a chirped pulse of circularly polarised light, and an "optical centrifuge" consisting of two oppositely chirped circularly polarised beams of opposite handedness. Even in the simplest case there can be significant qualitative differences between the two quantities -- they may have opposite signs, or one may be zero while the other is not. The origin of these differences lies in the different frequency scaling of the two quantities, which is made relevant by the presence of multiple frequency components in the fields.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:MacKinnon, Neel
Authors: Mackinnon, N.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Journal of Optics
Publisher:Institute of Physics Publishing Ltd.
ISSN:2040-8978
ISSN (Online):2040-8986
Published Online:15 October 2019
Copyright Holders:Copyright © 2019 IOP Publishing Ltd
First Published:First published in Journal of Optics 21(12):125402
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172865EPSRC DTP 16/17 and 17/18Tania GalabovaEngineering and Physical Sciences Research Council (EPSRC)EP/N509668/1Research and Innovation Services