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Directly measuring the total orbital angular momentum in astigmatic structured beams and the loss of several degrees of freedom
A.V. Volyar 1, E.G. Abramochkin 2, M.V. Bretsko 1, Ya.E. Akimova 1

1 Physics and Technology Institute of V.I. Vernadsky Crimean Federal University,
295007, Simferopol, Republic of Crimea, Russia, Academician Vernadsky 4;
2 Lebedev Physical Institute,
443011, Samara, Russia, Novo-Sadovaya 221

 PDF, 1797 kB

DOI: 10.18287/2412-6179-CO-1506

Pages: 832-840.

Full text of article: Russian language.

Abstract:
In this article, a model of the astigmatic structured beam obtained by the ABCD matrix method is shown to be simpler and more visual compared to the approach of integral transforms [Volyar AV, Abramochkin EG, Bretsko MV, Khalilov SI, Akimova YE. Control of giant orbital angular momentum bursts of structured Laguerre-Gaussian beams in a medium with general astigmatism. Computer Optics 2024; 48(1): 35-46. DOI: 10.18287/2412-6179-CO-1395]. We study in detail physical mechanisms of shaping super-high orbital angular momentum (OAM) after a cylindrical lens during general astigmatic transformations. We also theoretically substantiate and experimentally confirm a new technique for measuring a total OAM in the structured beam based on a single measurement of the crossed intensity moment as a result of computer processing of the intensity pattern. It is shown that such simplified measurements are based on the degeneracy of the off-diagonal elements W and M of the submatrices, which reduces the number of additional degrees of freedom of the structured beam from ten to seven.

Keywords:
structural light, astigmatic beams, ABCD matrices, orbital angular momentum, intensity moments.

Citation:
Volyar AV, Abramochkin EG, Bretsko MV, Akimova YE. Direct measuring the total orbital angular momentum in astigmatic structured beams and the loss of several degrees of freedom. Computer Optics 2024; 48(6): 832-840. DOI: 10.18287/2412-6179-CO-1506.

Acknowledgements:
This work was partly funded by the Russian Science Foundation under project No. 24-22-00278 (Sections “Complex amplitude of a structured Laguerre-Gaussian beam” and “Astigmatic transformation of a structured Laguerre-Gaussian beam”).

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