Full-space-manipulated multifunctional coding metasurface based on "Fabry-Pérot-like" cavity

Phase and amplitude simultaneously coding metasurface with multi-frequency and multifunctional electromagnetic modulations

The integration of multiple functionalities into a single, planar, ultra-compact metasurface has presented significant opportunities for enhancing capacity and performance within compact 5G/6G communication systems. Recent advances in multifunctional metasurfaces have unveiled comprehensive wavefront manipulations utilizing phase, polarization transmission/reflection, and coding apertures. Despite these developments, there remains a critical need for multifunctional metasurfaces with expanded channel capabilities, including multiple operational frequencies, minimal crosstalk, and high-efficiency computable array factors. This study introduces a multifunctional metasurface that integrates phase- and amplitude simultaneous coding meta-atoms at dual frequencies. By altering the polarization of electromagnetic (EM) waves, it is possible to reshape the wave-fronts of reflected waves at these frequencies. The coding metasurface proficiently manipulates both x and y linearly polarized waves through phase and amplitude coding at dual frequencies, thereby enabling distinct functionalities such as anomalous reflection, reflection imaging, and vortex wave beam generation. Both theoretical analysis and full-wave simulation confirm the anticipated functionalities of the designed devices, paving the way for advancements in integrated communication systems with diverse functionalities.

Programmable multifunctional metasurface for polarization, phase, and amplitude manipulation

Metasurfaces have shown extraordinary capability in individually manipulating various electromagnetic (EM) properties, including polarization, phase, and amplitude. However, it is still a challenge to manipulate these EM properties in one metasurface simultaneously. In this paper, a programmable multifunctional metasurface (PMFMS) is demonstrated with polarization, phase, and amplitude manipulation abilities. By controlling tunable coding states and changing the direction of incident waves, the PMFMS can operate as a transmission cross-polarization converter, spatial wave manipulator, and low-RCS radome. Besides, the PMFMS possesses an ultra-wideband property, which can operate from 6.5 to 10.2 GHz with 44.3% relative bandwidth. More importantly, multiple functionalities can also be achieved in reflection operating mode by reassembling the PMFMS. As a proof of concept, the PMFMS is fabricated and experimentally verified. Measured results are in good agreement with simulated results. Benefiting from multifunctional EM manipulations in an ultra-wideband, such a design can be applied in wireless communication systems, radar detection, and EM stealth platform.

VO2-enabled transmission-reflection switchable coding terahertz metamaterials

Coding metamaterials have offered unprecedented degrees of freedom to manipulate electromagnetic waves in time and frequency domains in terms of various coding sequences, however, it is still challenging to realize dynamic coding metamaterials in the terahertz range. Here, we propose VO₂-enabled transmission-reflection switchable coding terahertz metamaterials consisting of multilayered gold and VO₂ patterns. The insulator-to-metal transition of VO₂ leads to switch between the refractive and reflective scattering beams by changing the temperature. The four 2-bit elements are used to construct coding metasurface-based OAM generator with l = 1. Remarkably, the transmission-reflection switching functionality of the coding metasurface can be achieved at different frequencies. In addition, the novel designs in our work can achieve EM waves manipulation and provide a useful method to dynamically switch transmission-reflection response in the THz frequency regime.

Generating diverse functionalities simultaneously and independently for arbitrary linear polarized illumination enabled by a chiral transmission-reflection-selective bifunctional metasurface

A multifunctional metasurface is capable of manipulating electromagnetic waves and achieving kaleidoscopic functions flexibly, which significantly improves the integration and utilization of a single metasurface and has become one of the hotspots in electromagnetics. However, the majority of designs to date can only operate for limited polarization states in half-space and are difficult to show diverse functions at the same time, which restrict the widespread applications of multifunctional metadevices. Herein, an inspiring strategy of a chiral transmission-reflection-selective bifunctional metasurface is proposed to generate two independent functions in co-polarized reflection channel for left-handed circular polarized (LCP) incidence utilizing rotation-induced geometric phase modulation and in co-polarized transmission channel for right-handed circular polarized (RCP) incidence utilizing scaling-induced propagation phase modulation, and both functions appear concurrently under arbitrary linear polarized (LP) incident waves. To verify the feasibility of this methodology, three proof-of-concept metadevices composed of a dual-mode orbital angular momentum (OAM) generator, a bifocal metalens and an integrated metadevice of OAM generator and metalens are constructed and their performances in simulations and experiments are in good accordance with the theoretical ones. This exotic design of bifunctional metasurface will open up a promising way for multifunctional metadevices in engineering applications.

Simultaneous reduction of microwave reflection and infrared emission enabled by a phase gradient metasurface

Metasurfaces have shown promising applications in radar-infrared compatible stealth because of its superior electromagnetic wave control capabilities, but, to date, the majority of designs still suffer from the defects of large thickness, limited working bandwidth, relatively high infrared emissivity and so on. Here, an exotic phase gradient metasurface (PGM) is proposed to achieve low microwave reflection and low infrared emission concurrently, which has a small thickness of about 0.10λ₀. The microwave reflection reduction larger than 10 dB in 14-20 GHz is attributed to the anomalous reflection for arbitrary LP incident waves, and the infrared emissivity less than 0.28 from 3 to 14 µm is due to the indium-tin-oxide (ITO) with low infrared emissivity and high filling ratio. Also, the designed PGM can also realize beam deflection for orthogonal CP waves because of the meta-atoms' isotropic characteristics. Our methodology is fully verified by numerous simulations and experiments and may open a new avenue for radar-infrared compatible stealth research.

Broadband trifunctional metasurface and its application in a lens antenna

Multifunctional metasurfaces have attracted extensive attention due to their ability to achieve diversified wavefront controls in flat devices. To date, most designs through metasurface are confined to realize one or two functionalities. In this work, we implement a broadband trifunctional metasurface by using different meta-atoms of the same type. The meta-atoms can independently manipulate the amplitude and phase of transmitted waves and the phase of reflected waves in a wide frequency range. Thus, they help the metasurface achieving the functionalities of beam deflection, diffuse scattering, and beam focusing according to the polarization and the direction of incident waves. The metasurface is applied to a metalens antenna, which features broadband, low side-lobe, and stealth. The metalens antenna works at the frequency range 9.8 GHz to 11.6 GHz with gain over 25 dBi. Experiments verify the functions of the trifunctional metasurface and are in good agreement with the designs. Our approach provides a solid platform for high-efficiency wideband metadevices with diverse functionalities.

Ultra-thin and high-efficiency full-space Pancharatnam-Berry metasurface

Full-space metasurfaces (MSs) attract significant attention in the field of electromagnetic (EM) wave manipulation due to their advantages of functionality integration, spatial integration and wide applications in modern communication systems. However, almost all reported full-space metasurfaces are realized by multilayer dielectric cascaded structures, which not only has the disadvantages of high cost and complex fabrication but also is inconvenient to device integration. Thus, it is of great interest to achieve high-efficiency full-space metasurfaces through simple design and easy fabrication procedures. Here, we propose a full-space MS that can efficiently manipulate the circularly polarized (CP) waves in dual frequency bands by only using a single substrate layer, the reflection and transmission properties can be independently controlled by rotating the optimized meta-structures on the metasurface. Our full-space metasurface has the potential to design multifunctional devices. To prove the concept, we fabricate the device and measured it in microwave chamber. For the reflection mode, our metasurface can behave as a CP beam splitter at the frequency of f₁ = 8.3 GHz and exhibit high efficiencies in the range of 84.1%-84.9%. For the transmission mode, our metasurface acts as a meta-lens at the frequency of f₂ = 12.8 GHz for the LCP incidence, and the measured relative efficiency of the meta-lens reaches about 82.7%. Our findings provide an alternative way to design full-space metasurfaces and yield many applications in EM integration systems.

Achieving circular-to-linear polarization conversion and beam deflection simultaneously using anisotropic coding metasurfaces

An anisotropic coding metasurface (CM) is proposed for achieving circular-to-linear polarization conversion and beam deflection. Different phase coding consequences were independently achieved for two orthogonal linear polarized (LP) waves. Thus by elaborately designing coding sequences of the metasurfaces, different functions can be achieved, respectively for waves polarized along two orthogonal directions. More importantly, for circularly polarized (CP) wave, anisotropic CM can achieve circular-to-linear polarization conversion and beam deflection simultaneously. As a proof, a 1-bit anisotropic CM with 0101…/0101… and 0000…/1111… coding sequences respectively for two orthogonal LP waves was designed. The simulation results indicated that the incident CP wave is deflected into two x-polarized waves in x-o-z plane and two y-polarized waves in y-o-z plane. Both the simulation and experimental results verify the circular-to-linear polarization conversion performance of the anisotropic coding metasurfaces. The proposed anisotropic coding metasurfaces have the potential for the applications of multifunctional devices.