Abstract:We investigate a topological charge (TC) detection schema for an optical communication system employing Gaussian vortex beam (GVB). In this scenario, the transmitter maps the electrical message symbols to the TCs of GVBs. Thus obtained optical signal propagates in turbulent atmosphere arriving at the receiver, where a detection process is implemented to determine the TC of GVB by correlating the imaginary part of the mutual coherence function (MCF) of the incoming beam against the stored profiles. The feasibil… Show more
“…al have proposed that vortex beam can carry a spiral phase factor exp(in j) (n is the topological charge and j denotes the azimuthal angle) and each photon in the beam has an orbital angular momentum (OAM) of n, where is the reduced Planck constant. Meanwhile, vortex beam can improve the channel capacity of communication system by OAM coding or OAM multiplexing [12,13]; and can resist affects caused by turbulent atmosphere [5,[14][15][16][17][18][19][20] due to characteristics of itself. Moreover, elliptical beam also is a special beam, characterized by having elliptical intensity distribution [21][22][23][24].…”
We obtained the analytical formulas of partially coherent electromagnetic elliptical vortex beam (PCEEVB) propagating through atmospheric turbulence with the help of the extended Huygens-Fresnel principle and explored the normalized average intensity distribution of PCEEVB in turbulence. It is worth noting that the PCEEVB appears new characteristics such as self-rotating, self-splitting, and self-healing in turbulence. It can be also found that the number of peaks caused by splitting of beams is relevant to the topological charge n. What’s more, reducing the ellipticity, magnifying the topological charge, and increasing the initial coherent length δ0 can improve the anti-turbulence ability of PCEEVB in turbulence. The multi-phase screen simulation results are consistent with the theoretical results. Our results will have significant implications for laser communications, laser radar, and laser remote sensing.
“…al have proposed that vortex beam can carry a spiral phase factor exp(in j) (n is the topological charge and j denotes the azimuthal angle) and each photon in the beam has an orbital angular momentum (OAM) of n, where is the reduced Planck constant. Meanwhile, vortex beam can improve the channel capacity of communication system by OAM coding or OAM multiplexing [12,13]; and can resist affects caused by turbulent atmosphere [5,[14][15][16][17][18][19][20] due to characteristics of itself. Moreover, elliptical beam also is a special beam, characterized by having elliptical intensity distribution [21][22][23][24].…”
We obtained the analytical formulas of partially coherent electromagnetic elliptical vortex beam (PCEEVB) propagating through atmospheric turbulence with the help of the extended Huygens-Fresnel principle and explored the normalized average intensity distribution of PCEEVB in turbulence. It is worth noting that the PCEEVB appears new characteristics such as self-rotating, self-splitting, and self-healing in turbulence. It can be also found that the number of peaks caused by splitting of beams is relevant to the topological charge n. What’s more, reducing the ellipticity, magnifying the topological charge, and increasing the initial coherent length δ0 can improve the anti-turbulence ability of PCEEVB in turbulence. The multi-phase screen simulation results are consistent with the theoretical results. Our results will have significant implications for laser communications, laser radar, and laser remote sensing.
“…As a special kind of light field, optical vortex not only has a spiral wavefront phase structure, but also has a definite photon orbital angular momentum in the process of propagation, which provides an important theoretical basis for the application of optical vortex. Due to the uniqueness of the vortex field, the vortex beams are investigated as promising resources and have been applied in many research fields, including particle trapping [25], optical manipulation [26], high-resolution lithography [27,28], and optical communications [29][30][31][32]. As far as we know, propagation of a controllable anomalous hollow beam carrying optical vortex within uniaxial crystals has been discussed and analyzed [33].…”
Propagation of a recently proposed controllable anomalous hollow vortex (CAHV) beam is investigated. Based on the integral formula of generalized Huygens-Fresnel diffraction, analytical expression for the CAHV beam through a paraxial ABCD optical system is derived. The factors that affect the intensity pattern are determined by the beam’s controllable parameters a, cx, cy, and the topological charge m. Results show that the Gaussian distribution features are controlled by parameter a, and the horizontal and vertical stretching deformations of the beam are adjusted by parameters cx and cy, respectively. For a controllable anomalous hollow (CAH) beam, when propagating in free space, it could initially maintain anomalous hollow property and the size of the spot increases with the increase of the propagation distance. Due to the CAHV beam carries the optical vortex, a dark hollow channel appears in the center of the beam during propagation, and the channel structure changes with the increase of topological charge. Additionally, the Poynting vector of CAHV beam proves the direction of energy flow corresponding to the intensity distribution. Results obtained in this paper could have potential applications in particle trapping and optical control.
“…One of the prime interests of wireless optical communication is to find laser beams that are either nondiffracting or have well-defined orbital angular momentum (OAM) along a propagation channel. The applications of these special beams are found very promising in various fields, such as optical trapping, metrology, and wireless optical communication [1][2][3][4][5][6]. Unfortunately, OAM can be susceptible to atmospheric turbulence when distributing through the free space [7].…”
We establish propagation models for distributing autofocusing hypergeometric-Gaussian (HyGG) beams via non-Kolmogorov atmospheric turbulence in the single-photon and biphoton cases. Analytical expressions of the channel capacity and entanglement are employed to explore the communication performance in turbulence. It can be demonstrated that in the single-photon case, a lower hollowness parameter and larger topological charge could contribute to the anti-interference ability of HyGG beams. Such an anti-interference ability could be affected by the autofocusing distance more severely for beams with larger topological charges. In addition, the channel capacity of beams at a certain distance decays rapidly at first before it grows steadily with the increase in the power-law exponent of the non-Kolmogorov spectrum. For the biphoton case, the higher hollowness parameter, larger power-law exponent of the non-Kolmogorov spectrum and larger topological charge make HyGG beams maintain a high concurrence at longer distances. We believe that our results could serve as a reference for improving the quality of orbital-angular-momentum communication of HyGG beams via atmospheric turbulence.
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