Abstract
In this paper, metasurfaces with both cross-polarization conversion and vortex beam-generating are proposed. The proposed finite metasurface designs are able to change the polarization of incident electromagnetic (EM) waves to its cross-polarization. In addition, they also can modulate the incidences into beams carrying orbital angular momentum (OAM) with different orders ( and ) by applying corresponding transmission phase distribution schemes on the metasurface aperture. The generated vortex beams are at 5.14 GHz. The transmission loss is lower than 0.5 dB while the co-polarization level is −10 dB compared to the cross-polarization level. The measurement results confirmed the simulation results and verified the properties of the proposed designs.
Highlights
The orbital angular momentum of electromagnetic waves has been explored in recent years for its potential applications in wireless communications [1,2,3] and imaging [4,5]
The topological charge corresponds to the orbital angular momentum (OAM) mode and, theoretically, the OAM mode is vast
Amplitude nulls can be observed due to the phase singularity at the center of OAM carrying beams, and along with the donut-shaped field distribution verified the characteristic of the vortex beams
Summary
The orbital angular momentum of electromagnetic waves has been explored in recent years for its potential applications in wireless communications [1,2,3] and imaging [4,5]. EM wave carrying orbital angular momentum has a helical wavefront and an amplitude singularity in the propagating direction. The helical wavefront can be expressed by the term exp(ilΦ), where Φ is the azimuthal angle and l is the topological charge. The OAM in EM waves is typically generated using techniques like spiral phase plates [6,7], spiral reflectors [8], antennas [9,10,11], dieletric resonators [12], computer-induced holograms [13], transformation electromegnetics [14] and metasurfaces [15,16]. The spiral phase plate method gives the incident wave different phase retardation according to the term exp(ilΦ) by modulating the length of the wave path in corresponding areas. The antenna array approach usually use a circular antenna array to excite array elements with the same amplitude but different phases
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