High-efficiency broadband vortex beam generator based on transmissive metasurface

Abstract

Vortex beam has attracted growing attention in recent years due to its remarkable abilities in the communication system since it is believed to be an effective way to improve the channel capacity efficiency. However, available vortex beam generators suffer from the issues of complex configurations, low efficiency as well as narrow bandwidths, especially for the transmissive case. Here, we proposed a broadband transmissive metasurface to generate vortex beam with 1 l = in a broad band ranging from 8GHz to 13 GHz. We enhance the working bandwidth by carefully designing the meta-atoms which provide high transmittances along with similar slopes of the phase responses within a large frequency interval. More importantly, the designed vortex beam generator exhibits very high working efficiencies (more than 83% within the whole working band). Our finding opens a door for the design of high-efficiency broadband transmissive vortex beam generators and operating at other frequency domains.

Broadband and High-Efficiency Manipulation of Transmitted Vortex Beams via Ultra-Thin Multi-Bit Transmission Type Coding Metasurfaces

“…The function of the proposed SRR is exactly similar to complementary SRR, as presented in Ref. [40,47], which interacts with the incoming EM field leading to current transfer resulting in electric field perpendicular to the original one.…”

“…Further, since we claimed that our devices are highly efficient, thus a quantitative estimation of the efficiency is necessary. For this purpose, we calculate the working efficiency [37,40] of the proposed designs employing the formula as: Further, the power reflected and absorbed can be calculated using (4) and 5 83 t   ' is for design 'CV2' and for normal incidence only. For oblique incidences and for design CV3, the efficiency degrades slightly but it still has the numerical values η ≥ 77% which is still acceptable.…”

Metasurface Spiral Focusing Generators with Tunable Orbital Angular Momentum Based on Slab Silicon Nitride Waveguide and Vanadium Dioxide (VO2)

“…Recently, 2D metamaterials (also called metasurfaces), two-dimensional artificial structures consisting of arrays of subwavelength metal or dielectric optical elements with periodic arrangement, have obtained an increasing popularity for their special capability of flexibly manipulating the amplitude, polarization and phase of the transmitted or reflected electromagnetic waves at nanoscale [26][27][28][29][30][31][32][33][34][35]. So far, there have been significant works in the development of metasurfaces for generating vortex beams [36][37][38][39][40][41][42][43][44]. However, these works usually fail to achieve adjustable topological charge, which means that, once it is manufactured, its topological charge is fixed.…”

Focused vortex-beam generation using gap-surface plasmon metasurfaces

“…In particular, it is highly desired to efficiently integrate multiple diversified functionalities into a single design and supply additional degrees of freedom to control the wavefronts (i.e. phase and polarization) of the output vortex beams while maintaining the advantages of planar profiles, compactness, and relative ease of fabrication [17][18][19][20][21][22].…”