Three-Dimensional Simultaneous Arbitrary-Way Orbital Angular Momentum Generator Based on Transformation Optics

Abstract

In wireless communications, people utilize the technology of diversity against multipath fading, so as to improve the reliability of communication equipment. One of the long-standing problems in diversity antennas is the limited number of diversity in a certain space. In this paper, we provide a solution to this issue by a three-dimensional (3D) simultaneous arbitrary-way orbital angular momentum (OAM) generator (3D SAWOG) based on transformation optics. The proposed 3D SAWOG consists of a metamaterial block and a group of transformation cylinders, by which arbitrary-way planar wavefronts can be converted to helical wavefronts with various topological charges simultaneously. The 2D four-way OAM generator and the 3D SAWOG are analyzed, designed, and simulated. The simulation results validate the performance of a 3D SAWOG successfully, indicating that the proposed model possess a high mode purity and expansibility. The SAWOG can be used as a novel diversity antenna array due to the orthogonal property among different modes, which could provide more degrees of freedom than traditional dual-polarization antennas, further improving the reliability of the communication systems.

Long-range optical pulling force device based on vortex beams and transformation optics

“…TO devices have been also used to generate vortex beams [33,34], the design of which, however, needs anisotropic materials [34]. For such designs, due to azimuthally varying refractive index at the input and output ports of the device [33,34], index-matching can't be applied, which may result in reflections and backscattering of the light on the input/output boundaries.…”

“…TO techniques have been utilized to design optical devices which can control the behavior of electromagnetic field, such as waveguides and wave shifters\splitters\combiners, invisibility and illusion devices, flat lenses, low-profile highly directive antennas, and many other remarkable devices [31,32]. TO devices have been also used to generate vortex beams [33,34], the design of which, however, needs anisotropic materials [34]. For such designs, due to azimuthally varying refractive index at the input and output ports of the device [33,34], index-matching can't be applied, which may result in reflections and backscattering of the light on the input/output boundaries.…”

“…The analysis and design of optical forces in graded-index media operating in geometrical optics regime, have been done through force tracing method [38,39]. TO devices have been also used to generate vortex beams [40,41], the design of which, however, needs anisotropic materials [41]. For such designs, due to azimuthally varying refractive index at the input/output ports of the device [40,41], index matching cannot be applied, which may result in reflections and backscattering of the light on the input/output boundaries.…”

Multifunctional graphene metasurface to generate and steer vortex waves

“…In telecommunication, orbital angular momentum (OAM) is important to enhance the channel capacity since it can provide infinite state[28, 29]. Three-dimensional metamaterial can be used to generate OAM wave [30]. Metasurface, which can be considered as two dimensional metamaterial, can bring outstanding performance in sub-wavelength thickness.…”

Broadband Generation of Orbital Angular Momentum Carrying Beams in Rf Regimes

“…Understanding how to generate OAM beams flexibly and simply is an essential issue. Compared to optical OAM generators [13][14][15][16][17][18][19][20], radio frequency (RF) OAM generators are still in the initial research stage.…”