Broadband High-Efficiency Electromagnetic Orbital Angular Momentum Beam Generation Based on a Dielectric Metasurface

Abstract

Electromagnetic waves carrying orbital angular momentum (OAM) have motivated a wealth of applications. Achromatic or broadband OAM beams are preferred in many applications and have been extensively explored in previous research endeavors. In view of the low efficiency of the previous reported broadband OAM generators, this work proposes a metasurface composed of high-refractive-index dielectric resonators to achieve broadband OAM beam generation with high efficiency. An efficient method for designing the resonators is presented, which indicates that proper adjustment of the dimensions and rotation of the dielectric resonators can render broadband and high-efficiency full phase control. A broadband high-efficiency OAM generator is engineered based on the resonators from 18 to 28 GHz as a proof-of-concept example and validated by both simulation and experiments. Above 70% polarization conversion efficiency and above 65% operation efficiency are measured throughout the entire design band. Such structure provides an alternative mechanism for realizing broadband high-efficiency microwave, millimeter-wave, terahertz or optical OAM generation and can find potential applications in high-capacity communications and imaging.

High-Performance Transmissive Broadband Vortex Beam Generator Based on Pancharatnam–Berry Metasurface

“…Table I lists the comparison of the proposed vortex-beam generator with previous works in terms of the bandwidth, thickness, transmission or reflection mechanism, efficiency and polarization. Compared to previously reported vortex beam generators [37,[45][46][47][48][49][50][51][52][53], the most significant advantage of the proposed vortex-beam generator is its high-efficiency in wide bandwidth. Moreover, the phase control is totally dependent on the rotation of the meta-atom, which overcomes the intrinsic dispersion of the conventional vortex beam generators [40,41,54].…”

Manipulation of Terahertz Wave Based on Three-Layer Transmissive Pancharatnam-Berry Phase Metasurface

“…Table I demonstrates the comparison of the proposed orbital angular momentum beam generator by using threelayer Pancharatnam-Berry phase coding meta-atoms with previous works in terms of the structure, the number of layer, the thickness, the bandwidth, the polarization and the efficiency. Compared with previously proposed generators of OAM [46][47][48][49][50][51][52][53][54][55][56][57], the significant advantages of our proposed OAM generator are the potential simplicity of design and preparation and its high efficiency in wide bandwidth. Most of the previous designs of OMA generators used the resonance type of meta-atoms structure, and the delicate and time-consuming design is required by using the change of the element structure parameters.…”

Suspended Metasurface for Broadband High-Efficiency Vortex Beam Generation

“…The foundation of these applications is the vortex beam source. Various methods have been proposed to generate vortex beams, such as antenna arrays [6,12], spiral phase plates [13,14], q-plates [15,16], holographic diffraction gratings [17], reflect arrays [18][19][20], metasurfaces [21][22][23][24][25][26][27][28][29], and so on. Almost all methods, apart from the antenna arrays approach, are centered on introducing OAM to the impinging wave, which involves applying the vortex phase to the incident waves, which can be expressed by the term exp(ilΦ), where Φ is the azimuthal angle and l is the OAM order.…”

“…The bandwidth of the vortex beams is also of critical interest in potential applications such as broadband imaging [2]. Literature on broadband vortex generation is mainly based on the metasurface approach, Pancharatnam-Berry (PB) metasurface in particular [24][25][26][27][28][29]. Other methods such as hybrid helix array also exist [30].…”