In this paper, the instability of electrostatic twisted modes carrying orbital angular momentum in the moving electron–positron–ion plasma is investigated. In the kinetic theory approach, the general dispersion relation of twisted modes is derived by using Laguerre–Gaussian perturbed distribution function and electrostatic potential in the paraxial limit. Utilizing the obtained general dispersion relation for a specific case of electron–positron (e–p) shell with temperature anisotropy interacted with moving ion background, the effects of angular mode number, electrons and positrons temperature, and positron concentration on the group velocity and instability growth rate of twisted waves are illustrated, numerically. The results of the present investigation will greatly attribute to the understanding of e–p jet dynamic in astrophysical environments and laboratory experiments where the twisted modes can play a central role as a perturbed term.
In this paper, we investigate the strong modification and reshaping of the Laguerre-Gaussian (LG) beam using a tailored magnetized plasma photonic crystal (PPC), based on the angular spectrum expansion and 4×4 matrix method. It is numerically shown that by manipulating both external magnetic field and plasma number density, the reflected and transmitted beam shape is perfectly controlled. In addition, to show the domain role of magnetized PPC birefringence in the shaping of the twisted beam (TB), vertical incidence and oblique incidence of the LG beam are analyzed. We believe that these results open the door to use PPC structures in modulating the shape of a reference TB for new optical traps. Meanwhile, this study gives a new insight into the diagnostic of plasma systems using analyses of TB shapes.
In this paper, we explore what happens to the intensity profile, phase distribution, and centroid position of a vortex beam (VB) when it passes through a cold collision-less magnetized plasma layer. For this purpose, we utilize angular spectral expansion accompanied by a 4 × 4 matrix method to obtain the total transmission coefficient, intensity and phase profiles, and centroid shifts of VBs in the output plane. Based on numerical analyses, it is found that the evolution of transverse intensity as well as the distortion of the phase profile of transmitted VBs are greatly affected by variation of radial and angular mode numbers, external magnetic field, plasma number density, and incident angle. In addition, displacement of the VB centroid under variation of angular mode numbers is presented quantitatively. It is expected that the results of this study will give more insight into VB communication, radar probing, and plasma diagnostics.
This paper is devoted to the study of vortex beam transmission from an adjustable magnetized plasma-ferrite structure with negative refraction index. We use the angular spectral expansion technique together with the $$4\times 4$$ 4 × 4 matrix method to find out the transmitted intensity and phase profiles of incoming Laguerre-Gaussian beam. Based on numerical analysis we demonstrate that high transparency and large amount of Faraday rotation in the proximity of resonance frequency region, reverse rotation of spiral wave front, and side-band modes generation during propagation are the remarkable features of our proposed structure. These controllable properties of plasma-ferrite metamaterials via external static magnetic field and other structure parameters provide novel facilities for manipulating intensity and phase profiles of vortex radiation in transmission through the material. It is expected that the results of this work will be beneficial to develop active magneto-optical devices, orbital angular momentum based applications, and wavefront engineering.
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