Fractional orbital angular momentum of a Gaussian beam with an embedded off-axis optical vortex
V.V. Kotlyar, A.A. Kovalev, A.P. Porfirev, E.G. Abramochkin

 

Image Processing Systems Institute оf RAS, – Branch of the FSRC “Crystallography and Photonics” RAS, Samara, Russia,
Samara National Research University, Samara, Russia,
Samara Branch of P.N. Lebedev Physical Institute of Russian Academy of Sciences, Samara, Russia

Full text of article: Russian language.

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Abstract:
We theoretically and experimentally study asymmetric Gaussian optical vortices generated via diffracting a Gaussian beam by an off-axis spiral phase plate or amplitude "fork" hologram. It is shown that depending on the magnitude of the off-axis shift the laser beam can acquire a  crescent-shaped cross-section, which rotates on propagation. We obtain an analytical expression for the orbital angular momentum (OAM) of such a beam, which appears to be fractional. We show that with increasing off-axis shift, the OAM decreases parabolically. The experimental results are in qualitative agreement with theory and numerical simulation.

Keywords:
fractional orbital angular momentum, Gaussian beam, optical vortex, spiral phase plate.

Citation:
Kotlyar VV, Kovalev AA, Porfirev AP, Abramochkin EG. Fractional orbital angular momentum of a Gaussian beam with an embedded off-axis optical vortex. Computer Optics 2017; 41(1): 22-29. DOI: 10.18287/2412-6179-2017-41-1-22-29.

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