A Single-Layer Focusing Metasurface Based on Induced Magnetism

Abstract

A transmissive single-layer Huygens unit cell based on induced magnetism is proposed to design low-profile and multi-focus metasurface. The Huygens unit cell consists of a pair of antisymmetric metal elements and a dielectric substrate with only 1.2 mm thickness (λ 0 /6.8 at 37 GHz). The surface currents flowing in the opposite directions form the circulating electric currents to induce the magnetic currents orthogonal to the electric currents. The full coverage of 2π phase is achieved through optimizing the parameters of the metal elements, which solves the problem of the incomplete phase coverage caused by layer number reduction. With Holographic theory, the compensating phase distribution on the metasurface is calculated. The incident plane wave can be converged to designated points in any desired fashion including focal number, location, and intensity distribution, which exhibits outstanding manipulation capability. As the simulations and measured results show, the designed metasurface can achieve good multi-focus focusing characteristics. The focusing efficiency at the center frequency is 43.78%, and the relative bandwidth with 20% focusing efficiency exceeds 20%. The designed metasurface has the advantages of low profile, simple processing, and high efficiency, which has a wide range of application prospects in the fields of millimeter wave imaging, biomedical diagnosis and detection.

Single-Layer Achiral Metasurface with Independent Amplitude–Phase Control for Both Left-Handed and Right-Handed Circular Polarizations

“…Metasurfaces, the artificial planar arrangements of various subwavelength resonators, possess exceptional capability of tailoring the amplitude, phase, and polarization of electromagnetic waves. − Given the merits of low loss, small size, and simple fabrication, metasurfaces have drawn great attention and shown versatile applications, such as vortex beam generators, , focusing lenses, , meta-holograms, − surface plasmon polariton couplers, , etc. − Notably, some efforts are devoted to construction of chiral metasurfaces to acquire desired chiral effects. − For instance, numerous transmission-reflection-selective chiral structures are designed to block one state of the CP waves and transmit orthogonal CP waves. − Some ingenious metasurfaces can achieve circular dichroism by devising the chiral structures or introducing loss resistors into meta-atoms. − Furthermore, a range of schemes are proposed to independently control the wavefronts of LCP waves and RCP waves based on the integrated design of scaling-induced propagation phases and rotation-induced geometric phases. − More strikingly, certain multilayer multifunctional metasurfaces are established to tailor the amplitude and phase of orthogonal CP waves utilizing chiral structures with unequal dimensions working at distinct frequencies. , Nevertheless, most of the existing paradigms increase the complexity of the structures to obtain the intrinsic chirality or combine multilayer achiral structures to get the external chirality, and it is difficult for chiral metasurfaces to manipulate the amplitude and phase of orthogonal CP incident waves independently at the same frequency based on the present design mechanisms. In contrast, there are few studies on chiral phenomena generated by single-layer achiral structures, which means that the immense potential of chiral effects lies in simple achiral structures.…”

“…16,17 Metasurfaces, the artificial planar arrangements of various subwavelength resonators, possess exceptional capability of tailoring the amplitude, phase, and polarization of electromagnetic waves. 18−20 Given the merits of low loss, small size, and simple fabrication, metasurfaces have drawn great attention and shown versatile applications, such as vortex beam generators, 21,22 focusing lenses, 23,24 meta-holograms, 25−28 surface plasmon polariton couplers, 29,30 etc. 31−34 Notably, some efforts are devoted to construction of chiral metasurfaces to acquire desired chiral effects.…”

Soft Actor–Critic-Driven Adaptive Focusing under Obstacles

“…Metasurfaces, as two-dimensional metamaterials [ 1 , 2 ], have attracted extensive attention owing to their ability to generate arbitrary EM arrays by introducing corresponding field discontinuities at interfaces. Several interesting EM devices are based on metasurface technology including couplers [ 3 , 4 ], cloaking [ 5 , 6 , 7 ], focusing or imaging systems [ 8 , 9 , 10 , 11 ], and other devices [ 12 , 13 , 14 , 15 ]. A focusing metasurface is one of the most thought-provoking devices and are of great significance in promoting research in fields such as radar detection, imaging, and 6G communications.…”

Deep Neural Network with Data Cropping Algorithm for Absorptive Frequency‐Selective Transmission Metasurface

“…Metasurfaces with planar periodic metallic patterns arrayed on a subwavelength 2D dielectric substrate have been widely applied in cloaking, [1][2][3][4][5] focusing lens [6,7] and absorber. [8][9][10][11] A metasurface can effectively control electromagnetic (EM) waves by utilizing EM wave-matter interactions to achieve specific functions.…”