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

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Cameron, Robert P and Speirits, Fiona C and Gilson, Claire R and Allen, L and Barnett, Stephen M (2015) The azimuthal component of Poynting's vector and the angular momentum of light. Journal of Optics, 17 (12). 125610. ISSN 2040-8978 (https://doi.org/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.

ORCID iDs

Cameron, Robert P ORCID logoORCID: https://orcid.org/0000-0002-8809-5459, Speirits, Fiona C, Gilson, Claire R, Allen, L and Barnett, Stephen M;
  • Item type:Article
    ID code:54883
    Dates:
    Date
    Event
    29 October 2015
    Published
    12 August 2015
    Accepted
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:11 Dec 2015 01:51
    Last modified:11 Nov 2024 11:15
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/54883
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