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Vortex energy flow in the tight focus of a non-vortex field with circular polarization

V.V. Kotlyar 1,2, S.S. Stafeev 1,2, A.G. Nalimov 1,2

1 IPSI RAS – Branch of the FSRC "Crystallography and Photonics" RAS,

Molodogvardeyskaya 151, 443001, Samara, Russia,

2 Samara National Research University, Moskovskoye shosse, 34, 443086, Samara, Russia

 PDF, 647 kB

DOI: 10.18287/2412-6179-CO-582

Pages: 5-11.

Full text of article: Russian language.

Abstract:
Using Richards-Wolf formulas, we show that an axisymmetric circularly polarized vortex-free field can be focused into a sharp subwavelength focal spot, around which there is a  region where the light energy flow propagates along a spiral. This effect can be explained by the conversion of the spin angular momentum of the circularly polarized field into the orbital angular momentum near the focus, although the on-axis orbital angular momentum remains zero. It is also shown that a linearly polarized optical vortex with topological charge 2 forms near the focal plane an on-axis reverse energy flow (defined by the negative longitudinal component of the Poynting vector) whose amplitude is comparable with the direct energy flow.

Keywords:
Richards-Wolf formulae, relation between spin angular momentum and orbital angular momentum, reverse energy flow, linear polarization.

Citation:
Kotlyar VV, Stafeev SS, Nalimov AG. Vortex energy flow in the tight focus of a non-vortex field with circular polarization. Computer Optics 2020; 44(1): 5-11. DOI: 10.18287/2412-6179-CO-582.

Acknowledgements:
This work was supported by the Russian Science Foundation under project No. 17-19-01186 ("Theoretical background"), the RF Ministry of Science and Higher Education under the government project of FSRC «Crystallography and Photonics» RAS, ("Numerical simulation").

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