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Research on the propagation of partially coherent cosh-Gaussian beams through an ABCD optical system in non-Kolmogorov turbulence by effective tensor approach

Ma Hongjie, Li Jinsong, Chen Yueyang

Optica Applicata

2021

Vol. 51, nr 1

147--158

An efficient tensor approach is used to study the propagation of partially coherent cosh-Gaussian beams through an ABCD optical system in non-Kolmogorov turbulence. Analytical expressions for the average intensity of the beam propagation are derived. The properties of the average intensity are investigated with a numerical example. One finds that the propagation of the beam with larger spatial coherence length is less affected by distance when the propagation distance is long enough, and as the Ch-parameter increases, the beam propagation is less effected by turbulent atmosphere. It is also found that the average intensity distribution of the cosh-Gaussian beams with larger spatial correlation length is more affected by the structure constant of turbulence (i.e., turbulence level). By choosing a suitable Ch-parameter and spatial coherence length, the partially coherent cosh-Gaussian beams can be better transmitted in non-Kolmogorov turbulence. Our results will be useful in free-space communication.

The polarization and coherence behavior of the flat-topped array beam through non-Kolmogorov turbulence

Golmohammady Shole, Ghafary Bijan

Optica Applicata

2019

Vol. 49, nr 1

75--88

In the present paper, investigation on the polarization and coherence fluctuations of a flat-topped array beam in non-Kolmogorov atmospheric optics links has been presented. For this purpose, the spectral degree of polarization and coherence at the receiver plane is analytically formulated via the extended Huygens–Fresnel integral and the unified theory of polarization and coherence. The influences of the laser beam parameters and the power law exponent that describes the non-Kolmogorov spectrum of the statistical propagation properties of a partially coherent flat-topped array laser beam has been studied in detail. For the employed parameters, it can be concluded that the increase in the structure constant of turbulence (which is equivalent to the increase in turbulence strength) leads to a fast reduction in the spectral degree of coherence. Moreover, when the power law exponent is 3.1, the spectral degree of coherence exhibits a minimum value in comparison with the Kolmogorov atmospheric turbulence.

Effects of inner and outer scale on beam spreading for a Gaussian wave propagating through anisotropic non-Kolmogorov turbulence

Gao C., Li X.

Optica Applicata

2017

Vol. 47, nr 1

63--74

Experimental results and empirical research have shown that atmospheric turbulence can present the anisotropic property not only at a few meters above the ground but also at high altitudes of up to several kilometers. This paper investigates beam spreading for a Gaussian wave propagating along a horizontal path in weak anisotropic non-Kolmogorov turbulence. Mathematical expressions for the long-term beam spreading radius were obtained based on the generalized von Kármán spectrum for anisotropic turbulence. The final model includes an anisotropic factor, which parameterizes the asymmetry of a turbulence cell, the spectral power law for non-Kolmogorov turbulence, the inner and outer scale of turbulence, and other essential optical parameters of a Gaussian wave. Numerical simulations indicate that the long-term beam spreading radius decreases with an increase in the anisotropic factor. We also analyze how the geometrical optics approximation may cause large errors for a small spectral power law value.