Orbital angular momentum state variation of vortex beams propagating in a plasma sheath turbulence

Abstract

The presence of turbulent media is one of the major problems in the free-space communications. This arises from the sever distortion of spatial modes which leads to data degradation. In recent years, utilizing pseudo-nondiffracting beams has been proposed as an efficient way for mitigating the disturbance induced by turbulence. In this regard, this paper is intended to theoretically investigate anisotropic plasma turbulence (PT) effects on the orbital angular momentum (OAM) spectra and phase evolutions of different kinds of pseudo-nondiffracting vortex beams (VB), including Bessel-Gaussian (BG) and Hypergeometric-Gaussian (HGG) beams. For this purpose, using the modified von Karman spectrum in the frame of Rytov theory, the orbital OAM-spectra of VBs propagating in anisotropic PT are derived, and the effects of anisotropy and source beams parameters on the mode probability of transmitted VBs are studied. Our numerical analysis reveals that when propagating VBs carrying OAM come across PT, under influences of such random medium, their OAM-spectra spread, and several side-band modes which induce phase perturbations are generated. As well as, the propagation performance of pseudo-nondiffracting VBs in an anisotropic PT is better than isotropic one. Furthermore, it is found out that under the equivalent PT conditions BG beams are less influenced by PT in comparison with HGG beams. We expect our results to provide advances on turbulence-resilient communications, free-space optical data transmissions, and imaging.