A differentiated plane wave as an electromagnetic vortex

J. H. Hannay, J. F. Nye

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)

Abstract

Differentiating a complex scalar plane wave with respect to its direction produces an isolated straight vortex line and has a natural extension, described in earlier papers, to the vector waves of electromagnetism - a differentiated plane wave (DPW). It epitomizes destructive interference and will be shown to have the local structure of an electromagnetic vortex. In this paper its polarization structure and Poynting vector field are compared and contrasted with that of the family of linear polynomial waves, of which it is a special member. By definition this wider family has a general linear complex vector function of position multiplying a plane wave, but the function must be such that the combination satisfies Maxwell's equations. This forces translational invariance of the function along the wavevector direction - in other words the wave is 'non-diffracting'. In a natural sense all possible polarizations are exhibited once only. But the DPW has a distinctive polarization structure only partly explored previously. Both classes of waves share similar Poynting vector fields, which can be 'elliptic' (helix-like flow lines) or 'hyperbolic', of a repulsive nature, unexpected for a vortex. Both classes can be considered as a limit in the superposition of three closely parallel ordinary plane waves in destructive interference, and this derivation is supplied in full here.

Original languageEnglish
Article number045603
Number of pages12
JournalJournal of Optics
Volume17
Issue number4
DOIs
Publication statusPublished - 1 Apr 2015

Keywords

  • diffraction
  • electromagnetic vortex
  • optical vortex
  • polarization
  • singular optics
  • wave propagation
  • wave vortex

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