In this paper, a multifunctional coding metasurface (MCMS) has been proposed to realize dual-circularly polarized beams and beam focusing with transmission and reflection. The phase of transmissive wave is controlled by rotating the elements, and the corresponding element, which consists of two quadrate voids etched on a single layer substrate, is designed for the metasurface with Pancharatnam-Berry (PB) phase. The phase distribution of the circularly polarized four-beam is determined according to the convolution theorem of patterns and the phase compensation principle. In order to validate the proposed metasurface, the multifunctional meta-device is fabricated and measured to illustrate the four-beam with left circular polarization in transmissive space and the right circularly polarized four-beam in reflective space by MCMS with x-polarized incidence. The experimental results heavily agree with the simulated data. The MCMS has potential applications in wireless communications due to its low profile, compact, and lightweight features.

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Multifunctional Coding Metasurface With Left and Right Circularly Polarized and Multiple Beams

The Pancharatnam-Berry (PB) phase can be used to control the phase of circularly polarized electromagnetic waves. However, there are few studies on the modulation of dual-circularly polarized multi-beam using the transmissive coding metasurface. A scheme of spin-controlling multi-beam by transmissive coding metasurface is proposed for dual-circular polarization simultaneously. The transmissive coding metasurface (TCMS) can transmit linearly polarized incidence into multi-beam with orthogonally circular polarization. The phase distribution is designed based the convolution theorem, and the elements of metasurface conforming to the PB phase are arranged according to the phase distribution. In order to compensate the emitting spherical waves into plane waves and realize the transmissive waves with dual-circular polarization, an interesting scheme of elements in different regions with different rotating phase are presented based on the principle of phase compensation. TCMS can transmit linearly polarized waves into two left-hand circularly polarized (LHCP) beams and two right-hand circularly polarized (RHCP) beams. The prototype of TCMS is fabricated and measured, and the experimental results agree well with the simulated data. The transmissive metasurface has potential application in holograms and satellite communication. 

Transmissive coding metasurface with dual-circularly polarized multi-beam

Digital coding transmissive metasurface for multi-OAM-beam

This paper presents a new design of linear-polarization metasurface converter with arbitrary polarization rotating angle. The linear-polarization conversion is achieved by first separating the linearly polarized incident wave into two orthogonal circularly polarized waves, then adding an additional phase to one of the circularly polarized waves, and finally recombining these two circularly polarized waves into a linearly polarized wave and reflecting it towards free space. A practical unit cell operating at 10 GHz with sandwich structure is applied to realize the linear-polarization metasurface converter, which consists of a top-layer square patch, a middle-layer ground plane, a bottom-layer 90° quadrature hybrid coupler, and two vias connecting the top layer and bottom layer. The proposed linear-polarization metasurface converter is analyzed theoretically and demonstrated by both simulating and experimental results.

Linear-polarization metasurface converter with an arbitrary polarization rotating angle

A transmission‐type metasurface (MS) based on the combined geometric and transmission phase is proposed and investigated here numerically, which can achieve independently manipulation of the circular polarization (CP) and linear polarization (LP) wavefront at terahertz (THz) region. The unit‐cell of the proposed MS is composed of the dielectric substrate sandwiched with the bilayered inner centrosymmetric‐notched‐elliptic (CNE), outer C‐shaped, and single‐split‐ring (SSR) structures. The proposed MS can convert the normal incident LP wave to its orthogonal one at the lower frequency (f1 = 0.68 THz) after transmission and left‐handed circular polarization to the transmitted right‐handed circular polarization wave or vice versa at the higher frequency (f2 = 1.34 THz). The full 2π phase shifts of the both transmitted LP and CP waves can be realized independently and simultaneously by varying the opening and orientation angles of the outer SSR structure based on the transmission phase and the orientation angle of the inner CNE structure based on geometric phase, respectively. As proofs of concept, anomalous refraction, planar focusing, and vortex beam generation for both LP and CP waves are demonstrated numerically. These findings show great potential applications in imaging and communication systems, providing new possibilities to develop multifunctional THz device for both LP and CP waves.

Terahertz Transmission‐Type Metasurface for the Linear and Circular Polarization Wavefront Manipulation

Quad-Band Transmissive Metasurface with Linear to Dual-Circular Polarization Conversion Simultaneously

Vortex electromagnetic wave carrying orbital angular momentum (OAM) is expected to break through the shortage of spectrum resource because of its multiple independent modes. Nowadays, there are various methods to generate OAM vortex beam. Based on the concepts of digital metasurface and propagation phase, a broadband 3‐bit coding transmission metasurface is designed and illustrated by simulation and measurement. The elements exhibit the different phase by changing the size of metal patch, and the focusing phase is introduced to reduce the divergence of OAM beams. Based on the principle of phase superposition, the wide‐band, high‐purity, and multi‐beam OAM vortex waves can be generated by the transmission‐coding metasurface (TCMS). The experimental results verify that TCMS realizes the multiple OAM beams along different directions simultaneously from 9 to 10.5 GHz, which are consistent with the theoretical results. The high purity more than 90% of OAM mode is demonstrated by both the simulated and measured results. The TCMS provides a potential and effective scheme for OAM multiplexing and multi‐target positioning in wireless systems.

Multiple Orbital Angular Momentum Beams with High‐Purity of Transmission‐Coding Metasurface

A coding transmissive metasurface is presented for −1 mode quad-OAM-beam generation in 9.2–9.4 GHz. The 3bit metasurface is designed based on Pancharatnam−Berry (PB) phase principle, which is fed by a linear horn antenna. To satisfy the phase requirement of quad-OAM-beam, the phase compensation is introduced in the design for transmitting spherical waves into plane waves and promoting the directionality of incidence. The prototype of the metasurface is fabricated and measured. The experimental results coincide with theoretical analysis. Additionally, the OAM efficiency and purity are calculated to reveal the perfect performance of the metasurface. The proposed method has potential application in multi-channel wireless communication systems. 

Quad-OAM-beam based on coding transmissive metasurface

As 2D metamaterials, metasurfaces are well known due to the distinctive manipulation of the amplitude, phase, polarization, and propagation for electromagnetic (EM) waves. However, the existing metasurfaces are mainly designed to control the incident waves. Herein, a coding‐feeding metasurface (CFMS) with two functions of dual‐band emission and diffusion for incidences simultaneously is proposed. The zigzag emission patch and two arc‐split triangle patches for polarization conversion are nested together on a shared aperture of a unit cell for CFMS. The genetic optimization algorithm is introduced for diffusion. A prototype is fabricated and measured to validate the proposed CFMS with dual‐function. The experimental results agree well with the simulated data, which verify the diffusion and emission for CFMS. The CFMS with the lightweight, compact, and low profile has the potential applications in imaging, detection, and wireless communication systems for stealth aircraft.

Guo Shuai Huang

Papers

Quad-Band Transmissive Metasurface with Linear to Dual-Circular Polarization Conversion Simultaneously

Multifunctional Coding Metasurface With Left and Right Circularly Polarized and Multiple Beams

Multiple Orbital Angular Momentum Beams with High‐Purity of Transmission‐Coding Metasurface

Quad-OAM-beam based on coding transmissive metasurface

Coding‐Feeding Metasurface for Diffusion and Dual‐Band Emission