scholarly journals Propagation Properties of Vortex Cosine-Hyperbolic-Gaussian Beams Through Oceanic Turbulence

2021 ◽  
Author(s):  
Mohamed Lazrek ◽  
Zoubir Hricha ◽  
Abdelmajid Belafhal
Keyword(s):  
Dissipation Rate ◽  
Sea Water ◽  
Turbulent Medium ◽  
Average Intensity ◽  
Underwater Communication ◽  
Salinity Fluctuation ◽  
Oceanic Turbulence ◽  
Diffraction Integral ◽  
Beam Parameters ◽  
Propagation Properties

Abstract Based on the extended Huygens–Fresnel diffraction integral, the analytical expression of the average intensity for a vortex cosine hyperbolic-Gaussian beam (vChGB) propagating in oceanic turbulence is derived in detail. From the derived formula, the propagation properties of a vChGB in oceanic turbulence, including the average intensity distribution and the beam spreading are discussed with numerical examples. It is shown that oceanic turbulence influences strongly the propagation properties of the beam in the turbulent medium. The vChGB may propagate within shorter distance in weak oceanic turbulence by increasing the dissipation rate of mean-square temperature and the ratio of temperature to salinity fluctuation or by increasing the dissipation rate of turbulent kinetic energy per unit mass of sea water. Meanwhile, the evolution properties of the vChGB in the oceanic turbulence are affected by the initial beam parameters, namely the decentered parameter b, the topological charge M, the beam waist width ω0 and the wavelength λ. The obtained results can be beneficial for applications in optical underwater communication and remote sensing domain, imaging, and so on.

scholarly journals Propagation Properties of an Off-Axis Hollow Gaussian-Schell Model Vortex Beam in Anisotropic Oceanic Turbulence

2021 ◽  
Vol 9 (10) ◽  
pp. 1139
Author(s):  
Xinguang Wang ◽  
Le Wang ◽  
Shengmei Zhao
Keyword(s):  
Dissipation Rate ◽  
Beam Width ◽  
Average Intensity ◽  
Vortex Beam ◽  
Oceanic Turbulence ◽  
Beam Characteristic ◽  
Anisotropic Coefficient ◽  
Higher Temperature ◽  
Inner Scale ◽  
Propagation Properties

Based on the extended Huygens–Fresnel principle and the power spectrum of anisotropic oceanic turbulence, the analytical expressions of the average intensity and coherence properties of an off-axis hollow Gaussian-Schell model (OAHGSM) vortex beam propagating through anisotropic oceanic turbulence were derived. The effects of turbulent ocean and beam characteristic parameters on the evolution properties of the OAHGSM vortex beam were analyzed in detail. Our numerical simulation results showed that the OAHGSM vortex beam with a larger position factor is more focusable. Meanwhile, the OAHGSM vortex beam eventually evolves into a Gaussian-like beam after propagating through the anisotropic oceanic turbulent channel. The speed of this process can be accelerated by the decrease of the hollow order, topological charge, beam width, and transverse coherence width of the beam. The results also indicated that the normalized average intensity spreads more greatly and the spectral degree of coherence decays more rapidly for the smaller dissipation rate of the kinetic energy per unit mass of fluid, the smaller anisotropic coefficient, the smaller inner scale factor, the larger dissipation rate of the mean-squared temperature, and the higher temperature–salinity contribution ratio.

scholarly journals Effects of Turbulent Atmosphere on the Propagation Properties of Vortex Hermite-cosine-hyperbolic-Gaussian Beams

2021 ◽  
Author(s):  
Zoubir Hricha ◽  
Mohammed Lazrek ◽  
Mohammed Yaalou ◽  
Abdelmajid Belafhal
Keyword(s):  
Turbulent Atmosphere ◽  
Analytical Formula ◽  
Propagation Distance ◽  
Central Peak ◽  
Average Intensity ◽  
Practical Applications ◽  
Diffraction Integral ◽  
Peak Intensity ◽  
Beam Parameters ◽  
Propagation Properties

Abstract The propagation properties of a vortex Hermite-cosh-Gaussian beam (vHChGB) in atmospheric turbulence are investigated based on the extended Huygens–Fresnel diffraction integral and Rytov method. The analytical formula for the average intensity of a vHChGB propagating in turbulent atmosphere is derived in detail. The influence of the turbulence strength on the intensity distribution under the change of beam parameters conditions is illustrated numerically and discussed. Results show the profile of the initial vHChGB remains unchanged within small propagation distance range, and at certain propagation distance a central peak intensity appears, and finally the beam evolves into Gaussian profile–like in far-field. The rising speed of the central peak intensity is faster when the turbulence strength is larger or the beam parameters such as the beam order, the vortex charge and the Gaussian waist width are smaller. With a small decentered parameter b, the beam profile changes faster as the wavelength is larger, whereas the reverse behavior occurs when b is large. The obtained results may be useful for the practical applications of vHChGB in optical communications and remote sensing.

scholarly journals Propagation of Vortex Cosine-hyperbolic-gaussian Beams in Atmospheric Turbulence

2021 ◽  
Author(s):  
Zoubir Hricha ◽  
Mohammed Lazrek ◽  
Mohammed Yaalou ◽  
Abdelmajid Belafhal
Keyword(s):  
Atmospheric Turbulence ◽  
Propagation Distance ◽  
Central Peak ◽  
Average Intensity ◽  
Gaussian Width ◽  
Diffraction Integral ◽  
Constant Strength ◽  
Beam Parameters ◽  
Propagation Properties ◽  
Rytov Method

Abstract In this paper, the propagation properties of a vortex cosh-Gaussian beam (vChGB) in turbulent atmosphere are investigated. Based on the extended Huygens–Fresnel diffraction integral and the Rytov method, the analytical expression for the average intensity of the vChGB propagating in the atmospheric turbulence is derived. The effects of the turbulent strength and the beam parameters on the intensity distribution and the beam spreading are illustrated numerically and analyzed in detail. It is shown that upon propagating, the incident vChGB keeps its initial hollow dark profile within a certain propagation distance, then the field loses gradually its central hole-intensity and transformed into a Gaussian–like beam for large propagation distance. The rising speed of the central peak is demonstrated to be faster when the constant strength turbulence or the wavelength are larger and the Gaussian width is smaller. The obtained results can be beneficial for applications in optical communications and remote sensing.

scholarly journals Nonparaxial Propagation Properties of Specially Correlated Radially Polarized Beams in Free Space

2019 ◽  
Vol 9 (5) ◽  
pp. 997
Author(s):  
Lina Guo ◽  
Li Chen ◽  
Rong Lin ◽  
Minghui Zhang ◽  
Yiming Dong ◽  
...  
Keyword(s):  
Free Space ◽  
Degree Of Polarization ◽  
Average Intensity ◽  
Polarized Beams ◽  
Diffraction Integral ◽  
Spectral Density Matrix ◽  
Potential Applications ◽  
Spectral Degree ◽  
Propagation Properties ◽  
Radially Polarized

A specially correlated radially polarized (SCRP) beam with unusual physical properties on propagation in the paraxial regime was introduced and generated recently. In this paper, we extend the paraxial propagation of an SCRP beam to the nonparaxial regime. The closed-form 3 × 3 cross-spectral density matrix of a nonparaxial SCRP beam propagating in free space is derived with the aid of the generalized Rayleigh–Sommerfeld diffraction integral. The statistical properties, such as average intensity, degree of polarization, and spectral degree of coherence, are studied comparatively for the nonparaxial SCRP beam and the partially coherent radially polarized (PCRP) beam with a conventional Gaussian–Schell-model correlation function. It is found that the nonparaxial properties of an SCRP beam are strikingly different from those of a PCRP beam. These nonparaxial properties are closely related to the correlation functions and the beam waist width. Our results may find potential applications in beam shaping and optical trapping in nonparaxial systems.

scholarly journals Propagations of Sin-Gaussian Beam with Astigmatism through Oceanic Turbulence

2021 ◽  
Vol 299 ◽  
pp. 03013
Author(s):  
Kaicheng Zhu ◽  
Chang Gao ◽  
Jiahui Li ◽  
Dengjuan Ren ◽  
Jie Zhu
Keyword(s):  
Gaussian Beam ◽  
Coherence Length ◽  
Structure Constant ◽  
Average Intensity ◽  
Oceanic Water ◽  
Fresnel Integral ◽  
Oceanic Turbulence ◽  
Atmosphere Turbulence ◽  
Beam Parameters ◽  
Analytical Expressions

The propagation behaviours of a sin-Gaussian beam (SiGB) with astigmatism in oceanic water is analysed. The analytical expressions for the average intensity of such a beam are derived by using the extended Huygens-Fresnel integral. Its average intensity and on-axial intensity distributions in oceanic water are numerically examined. Then, we mainly focus on the effect of the beam parameters and the medium structure constant on the propagation behaviours for the astigmatic SiGBs in oceanic water, revealing that the evolutions of the intensity distributions can be effectively modulated by adjusting the astigmatic parameter, coherence length and the atmosphere turbulence strength.

scholarly journals Effects of Oceanic Turbulence on Orbital Angular Momenta of Optical Communications

2020 ◽  
Vol 8 (11) ◽  
pp. 869
Author(s):  
Shuang Zhai ◽  
Yun Zhu ◽  
Yixin Zhang ◽  
Zhengda Hu
Keyword(s):  
Dissipation Rate ◽  
Quantum Coherence ◽  
Single Photon ◽  
Beam Width ◽  
Communication Performance ◽  
Oceanic Turbulence ◽  
Angular Momenta ◽  
Optimal Beam ◽  
Lower Temperature ◽  
Inner Scale

The propagation properties of Laguerre-Gaussian beams in oceanic turbulence are investigated for both single-photon and biphoton cases. For single-photon communication, the channel capacity and trace distance are employed, both of which effectively reveal the communication performance via different viewpoints. For the biphoton case, we consider distributions of quantum resources including entanglement and quantum coherence. Turbulence conditions with a larger inner-scale and anisotropic factors, higher dissipation rate of kinetic energy, lower dissipation rate of the mean-squared temperature, and lower temperature-salinity contribution ratio combined with longer wavelength and an appropriate range of optimal beam width are beneficial to communication performances. Our results provide theoretical significance to improve the orbital-angular-momentum communication via oceanic turbulence.

scholarly journals Effects of Anisotropic Turbulence on Propagation Characteristics of Partially Coherent Beams with Spatially Varying Coherence

2018 ◽  
Vol 8 (11) ◽  
pp. 2025 ◽  
Author(s):  
Wentao Dao ◽  
Chunhao Liang ◽  
Fei Wang ◽  
Yangjian Cai ◽  
Bernhard J. Hoenders
Keyword(s):  
Turbulent Medium ◽  
Average Intensity ◽  
Weak Turbulence ◽  
Anisotropic Turbulence ◽  
Turbulence Regime ◽  
Coherence Parameter ◽  
Coherent Beams ◽  
Local Intensity ◽  
Spatially Varying ◽  
Analytical Expressions

Based on the extended Huygens-Fresnel (eHF) principle, approximate analytical expressions for the spectral density of nonuniformly correlated (NUC) beams are derived with the help of discrete model decompositions. The beams are propagating along horizontal paths through an anisotropic turbulent medium. Based on the derived formula, the influence of the anisotropic turbulence (anisotropy factors, structure parameters) on the evolution of the average intensity, the shift of the intensity maxima and the power-in-the-bucket (PIB) are investigated in detail through numerical examples. It is found that the lateral shifting of the intensity maxima is closely related to the anisotropy factors and the strength of turbulence. Our results also reveal that, in the case of weak turbulence, the beam profile can retain the feature of local intensity sharpness, but this feature degenerates quickly if the strength of the turbulence increases. The value of PIB of the NUC beams can be even higher than that of Gaussian beams by appropriately controlling the coherence parameter in the weak turbulence regime. This feature makes the NUC beams useful for free-space communication.

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