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Boundary conditions and spin of a dense light beam
KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
2006 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 74, no 1, 139-144 p.Article in journal (Refereed) Published
Abstract [en]

A light beam of high photon density and spatially limited cross-section is analysed with respect to its boundary conditions and angular momentum ( spin). For Maxwell's equations in a vacuum state of vanishing electrical field divergence, the exact solutions are found not to be reconcilable with a beam having a limited cross-section and a nonzero spin. Transverse spatial beam derivatives only become possible as an approximation when their characteristic lengths are very large as compared to the relevant wavelengths, but even then there is no spin. A revised electromagnetic theory, based on a nonzero electric field divergence in the vacuum state, leads on the other hand to beam configurations for which there can exist strong transverse derivatives in a boundary region, as well as a nonzero spin. The Poynting vector then has components both in the axial direction of propagation and in the transverse direction along the boundary. The angular momentum, being imagined as an equivalent sum of momenta of the individual photons in the beam interior, is then replaced by a real spin generated and localized in the boundary layer.

Place, publisher, year, edition, pages
2006. Vol. 74, no 1, 139-144 p.
Keyword [en]
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-37577DOI: 10.1088/0031-8949/74/1/020ISI: 000238901200020ScopusID: 2-s2.0-33745495068OAI: diva2:434486
QC 20110815Available from: 2011-08-15 Created: 2011-08-15 Last updated: 2011-08-15Bibliographically approved

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