The azimuthal component of Poynting's vector and the angular momentum of light

Cameron, R. P., Speirits, F. C. , Gilson, C. R. , Allen, L. and Barnett, S. M. (2015) The azimuthal component of Poynting's vector and the angular momentum of light. Journal of Optics, 17(12), 125610. (doi: 10.1088/2040-8978/17/12/125610)

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Abstract

The usual description in basic electromagnetic theory of the linear and angular momenta of light is centred upon the identification of Poynting's vector as the linear momentum density and its cross product with position, or azimuthal component, as the angular momentum density. This seemingly reasonable approach brings with it peculiarities, however, in particular with regards to the separation of angular momentum into orbital and spin contributions, which has sometimes been regarded as contrived. In the present paper, we observe that densities are not unique, which leads us to ask whether the usual description is, in fact, the most natural choice. To answer this, we adopt a fundamental rather than heuristic approach by first identifying appropriate symmetries of Maxwell's equations and subsequently applying Noether's theorem to obtain associated conservation laws. We do not arrive at the usual description. Rather, an equally acceptable one in which the relationship between linear and angular momenta is nevertheless more subtle and in which orbital and spin contributions emerge separately and with transparent forms.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Barnett, Professor Stephen and Speirits, Dr Fiona and Cameron, Dr Robert and Gilson, Dr Claire
Authors: Cameron, R. P., Speirits, F. C., Gilson, C. R., Allen, L., and Barnett, S. M.
College/School:College of Science and Engineering > School of Mathematics and Statistics > Mathematics
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
Copyright Holders:Copyright © 2015 IOP Publishing Ltd
First Published:First published in Journal of Optics 17(12):125610
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
663801NOVEL MANIFESTATIONS OF OPTICAL ACTIVITYStephen BarnettEngineering & Physical Sciences Research Council (EPSRC)EP/M004694/1S&E P&A - PHYSICS & ASTRONOMY