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Orbital angular momentum and topological charge of a Gaussian beam with multiple optical vortices

A.A. Kovalev 1,2, V.V. Kotlyar 1,2, D.S. Kalinkina 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, 813 kB

DOI: 10.18287/2412-6179-CO-632

Pages: 34-39.

Full text of article: Russian language.

Abstract:
Here we study theoretically and numerically a Gaussian beam with multiple optical vortices with unitary topological charge (TC) of the same sign, located uniformly on a circle. Simple expressions are obtained for the Gaussian beam power, its orbital angular momentum (OAM), and TC. We show that the OAM normalized to the beam power cannot exceed the number of vortices in the beam. This OAM decreases with increasing distance from the optical axis to the centers of the vortices. The topological charge, on the contrary, is independent of this distance and equals the number of vortices. The numerical simulation corroborates that after passing through a random phase screen (diffuser) and propagating in free space, the beams of interest can be identified by the number of local intensity minima (shadow spots) and by the OAM.

Keywords:
Gaussian beam, optical vortex, phase singularity, orbital angular momentum, topological charge, random screen, diffuser, scattering medium.

Citation:
Kovalev AA, Kotlyar VV, Kalinkina DS. Orbital angular momentum and topological charge of a Gaussian beam with multiple optical vortices. Computer Optics 2020; 44(1): 34-39. DOI: 10.18287/2412-6179-CO-632.

Acknowledgements:
This work was partly funded by the Russian Foundation for Basic Research under projects 18-29-20003 ("Power, orbital angular momentum and topological charge of a Gaussian beam with phase singularities locates on a circle") and 18-07-01129 ("Appendix A Derivation of the expression for the beam power" and "Appendix B Derivation of the expression for the beam OAM") and by the RF Ministry of Science and Higher Education within the state project of FSRC "Crystallography and Photonics" RAS ("Numerical simulation of propagation in a random medium").

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