Methods for determining the orbital angular momentum of a laser beam
V. V. Kotlyarab, A. A. Kovalevab, A. P. Porfirevab
a IPSI RAS - Branch of the FSRC “Crystallography and Photonics” RAS, 443001, Samara, Russia, Molodogvardeyskaya 151
b Samara National Research University, 443086, Russia, Samara, Moskovskoye Shosse 34
We propose and study numerically and experimentally two methods for determining the orbital angular momentum (OAM) of paraxial laser beams. One method is based on registering the intensity in the Fresnel zone, numerically averaging this intensity over the polar angle at discrete radii, and solving a system of linear equations to find squared modules of the coefficients of the light field expansion in terms of basis functions. The other method is based on registering two intensity distributions in the Fourier plane of two cylindrical lenses rotated 90 degrees relative to each other, and calculating the first-order moments of the measured intensities. The experimental error of the OAM determination is about 1% for small fractional OAM (up to 4), and about 8% for large fractional OAM (up to 30).
paraxial laser beam, fractional orbital angular momentum, fractional topological charge, optical vortex, cylindrical lens, superposition of spatial modes.
|Russian Academy of Sciences - Federal Agency for Scientific Organizations
|Russian Science Foundation
|Russian Foundation for Basic Research
|This work was partly funded by the RF Ministry of Science and Higher Education within the state project of FSRC “Crystallography and Photonics” RAS under agreement 007-ÃÇ/×3363/26 (“Simulation”), the Russian Science Foundation under Project # 17-19-01186 (“Determining the OAM by measuring a single distribution of the beam intensity” and “Determining the OAM by measuring the intensity in the focus of two cylindrical lenses”, and the Russian Foundation for Basic Research under projects ## 18-29-20003, 18-07-01129 (“Paraxial laser beams carrying fractional OAM”).
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V. V. Kotlyar, A. A. Kovalev, A. P. Porfirev, “Methods for determining the orbital angular momentum of a laser beam”, Computer Optics, 43:1 (2019), 42–53
Citation in format AMSBIB
\by V.~V.~Kotlyar, A.~A.~Kovalev, A.~P.~Porfirev
\paper Methods for determining the orbital angular momentum of a laser beam
\jour Computer Optics
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