Компьютерная оптика (Oct 2020)

Toroidal polarization vortices in tightly focused beams with singularity

  • S.S. Stafeev,
  • V.V. Kotlyar

DOI
https://doi.org/10.18287/2412-6179-CO-734
Journal volume & issue
Vol. 44, no. 5
pp. 685 – 690

Abstract

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In this paper, we numerically investigated tight focusing of cylindrical vector beams of the sec-ond order using Richards-Wolf formulae. It was shown that intensity rings where the Poynting vector was equal to zero appeared not only in the focal plane but also in nearby planes. For example, a lens with numerical aperture NA=0.95 was shown to generate periodical toroidal vortices with a 0.8-mkm period along the z-axis at a distance of about 0.45 mkm from the axis. The vortices were generated pairwise, with the closest-to-focus vortex having clockwise helicity and the subsequent being anti-clockwise. The vortices were also characterized by saddle points. When focusing an optical beam passed through a narrow annular aperture, no toroidal vortices were observed.

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