On the resilience of scalar and vector vortex modes in turbulence

Author(s):

Cox, Mitchell A.; Rosales-Guzman, Carmelo; Lavery, Martin P. J.; Versfeld, Daniel J. & Forbes, Andrew

Abstract:

“Free-space optical communication with spatial modes of light has become topical due to the possibility of dramatically increasing communication bandwidth via Mode Division Multiplexing (MDM). While both scalar and vector vortex modes have been used as transmission bases, it has been suggested that the latter is more robust in turbulence. Using orbital angular momentum as an example, we demonstrate theoretically and experimentally that the crosstalk due to turbulence is the same in the scalar and vector basis sets of such modes. This work brings new insights about the behaviour of vector and scalar modes in turbulence, but more importantly it demonstrates that when considering optimal modes for MDM, the choice should not necessarily be based on their vectorial nature.”

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Publication: Opt. Express
Issue/Year: Opt. Express, Volume 24; Number 16; Pages 18105-18113; 2016
DOI: 10.1364/OE.24.018105

Pre-turbulence compensation of orbital angular momentum beams based on a probe and the Gerchberg–Saxton algorithm

Author(s):

Fu, Shiyao; Zhang, Shikun; Wang, Tonglu & Gao, Chunqing

Abstract:

“We propose a scheme that uses a probe Gaussian beam and the Gerchberg-Saxton (GS) algorithm to realize the pre-turbulence compensation of beams carrying orbital angular momentum (OAM). In the experiment, spatial light modulators are utilized to simulate the turbulent atmosphere and upload the retrieval holograms. A probe Gaussian beam is used to detect the turbulence. Then, the retrieval holograms, which can correct the phase distortion of the OAM beams, are obtained by the GS algorithm. The experimental results show that single or multiplexed OAM beams can be compensated well. The compensation performances under different iterations are also analyzed.”

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Publication: Opt. Lett.
Issue/Year: Opt. Lett., Volume 41; Number 14; Pages 3185-3188; 2016
DOI: 10.1364/OL.41.003185

Programmable simulator for beam propagation in turbulent atmosphere

Author(s):

Carolina Rickenstorff, José A. Rodrigo, and Tatiana Alieva

Abstract:

“The study of light propagation though the atmosphere is crucial in different areas such as astronomy, free-space communications, remote sensing, etc. Since outdoors experiments are expensive and difficult to reproduce it is important to develop realistic numerical and experimental simulations. It has been demonstrated that spatial light modulators (SLMs) are well-suited for simulating different turbulent conditions in the laboratory. Here, we present a programmable experimental setup based on liquid crystal SLMs for simulation and analysis of the beam propagation through weak turbulent atmosphere. The simulator allows changing the propagation distances and atmospheric conditions without the need of moving optical elements. Its performance is tested for Gaussian and vortex beams.”

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Publication: Optics Express
Issue/Year: Vol. 24, Issue 9, pp. 10000-10012 (2016)
DOI: 10.1364/OE.24.010000

Orbital-angular-momentum crosstalk and temporal fading in a terrestrial laser link using single-mode fiber coupling

Author(s):

Funes, Gustavo; Vial, Matias & Anguita, Jaime A.

Abstract:

“Using a mobile experimental testbed, we perform a series of measurements on the detection of laser beams carrying orbital angular momentum (OAM) to evaluate turbulent channel distortions and crosstalk among receive states in an 84-m roofed optical link. We find that a receiver assembly using single-mode fiber coupling serves as a good signal selector in terms of crosstalk rejection. From the recorded temporal channel waveforms, we estimate average crosstalk profiles and propose an appropriate probability density function for the fluctuations of the detected OAM signal. Further measurements of OAM crosstalk are described for a horizontal 400-m link established over our campus.”

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Publication: Opt. Express
Issue/Year: Opt. Express, Volume 23; Number 18; Pages 23133-23142; 2015
DOI: 10.1364/OE.23.023133

Hypergeometric-Gaussian modes

Author(s): Ebrahim Karimi, Gianluigi Zito, Bruno Piccirillo, Lorenzo Marrucci, and Enrico Santamato

Abstract:

“We studied a novel family of paraxial laser beams forming an overcomplete yet nonorthogonal set of modes. These modes have a singular phase profile and are eigenfunctions of the photon orbital angular momentum. The intensity profile is characterized by a single brilliant ring with the singularity at its center, where the field amplitude vanishes. The complex amplitude is proportional to the degenerate (confluent) hypergeometric function, and therefore we term such beams hypergeometric-Gaussian (HyGG) modes. Unlike the recently introduced hypergeometric modes [Opt. Lett. 32, 742 (2007)], the HyGG modes carry a finite power and have been generated in this work with a liquid-crystal spatial light modulator. We briefly consider some subfamilies of the HyGG modes as the modified Bessel Gaussian modes, the modified exponential Gaussian modes, and the modified Laguerre-Gaussian modes.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 32, Issue 21, pp. 3053-3055
DOI: 10.1364/OL.32.003053