High Efficiency Ultrathin Transmissive Metasurfaces

Abstract

introducing abrupt phase changes via an ultrathin sheet of subwavelength resonators (usually known as meta-atoms). The first such metasurface was proposed by Yu and Capasso [2] Afterward, significant number of novel metasurfaces have been proposed in microwave, [3] terahertz, [4] near-infrared, [5] and visible ranges. [6] These metasurfaces are utilized for realizing many applications such as focusing with subwavelength planar lenses, [7] optical cloaking, [8,9] generating nondiffracting beams, [10] manipulating phase profiles having orbital angular momentum (OAM), [11] photon spin Hall effect, [12] and performing computation with the coding metasurfaces. [13,14] Although metasurfaces have proved their unique freedom in wavefront manipulation, most metasurfaces generally suffer from low efficiencies. This is especially critical for transmissive metasurfaces where both the magnetic and electric resonances should be precisely controlled. For example, the efficiency of the first ever demonstrated metasurface was only 5%. [2] A few transmissive metasurfaces have since been introduced with higher efficiencies based on the Huygens' principle [15,16] or meta-transmit arrays. [17,18] However, the operation of these metasurfaces is severely restricted, e.g., may require specific polarization, added complexity in manufacturing, or demand complex, costly computations for each distinct phase.Recently, it has been demonstrated that metasurfaces can be realized based on the photon spin Hall effect. [19][20][21][22] Spin Hall effect is a phenomenon where moving electrons with opposite spins can be transversely separated. Spin Hall effect can be intrinsic based on spin-orbit coupling of electrons [23] or extrinsic due to the spin-dependent scatterings by impurities. [24] Both of these could be utilized to achieve extraordinary wave propagation. It is known that the experimentally observed intrinsic phenomena are usually very weak. [23] On the contrary, extrinsic spin Hall is observed in a special class of metasurfaces, [12] which utilizes subwavelength scatterers to achieve full phase control in the range of 0-2 π. The transmission/ reflection phase control of a cross-polarized wave is achievable through the rotation of the designed scatterers, which in fact make it more promising than the other types of meta-atoms that require phase dispersions to achieve phase control. The maximum achievable efficiency of such metasurfaces was theoretically predicted to be 25% in a single layer structure since only electric responses can be realized in such structures. [25,26] This limitation was overcome by designing reflective metasurfaces with ground planes, [27][28][29] where both the electric and the Metasurfaces offer unprecedented freedom to manipulate electromagnetic waves at deeply subwavelength scales. However, realizing a highly efficient metasurface, yet simple enough to conceptualize, design, and fabricate, is a challenging task. In this paper, a novel approach is proposed for designing meta-atoms which can achieve full phase cont...

Superscattering from Subwavelength Corrugated Cylinders

“…In other words, tensor impedance metasurfaces make it possible to manipulate polarization of scattered waves [33,37] and thereby may advance functionality of the scatterer. Although the problem of polarization control by metasurfaces is of much current interest [38][39][40][41], it deserves detailed consideration, which is beyond the scope of the present investigation. In the following, we are aimed at enhancing scattering of the TE z and TM z waves from a cylinder by means of surface impedance, which induces no cross-polarization coupling.…”

Ultrathin Single Layer Metasurfaces with Ultra‐Wideband Operation for Both Transmission and Reflection

“…By appropriately controlling the wave characteristics, it is possible to achieve intriguing applications in microwave,4 acoustics,5 and optics regimes 6,7. So far these metasurfaces have been successfully employed for many applications, such as realization of orbital angular momentum (OAM) waves,8 photons spin Hall Effect,9 Bessel beams,10 optical cloaking,11 and holography,12 to name a few.…”

Active Anisotropic Coding Metasurface with Independent Real‐Time Reconfigurability for Dual Polarized Waves

“…Further improvement of the reflection efficiency may be achieved by increasing the thickness of substrate to lower the resonant strength of the meta-atom or by loading with low-loss diodes instead. Besides, since the anisotropic metasurfaces also show powerful abilities to control the polarization states of the EM wave, [18] it is promising to use active coding metasurface to dynamically and simultaneously manipulate the phase functions and the polarization states. [30] The meta-atom, incorporated with electrically driven varactors along each direction, can work independently for x-and y-excitation with negligible polarization cross-talk, as evidenced by the reflection properties of the meta-atom ( Figure S2 in the Supporting Information) and the surface current distributions ( Figure S3 in the Supporting Information).…”

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admt.201900930.

Metasurfaces, planar arrays composed of subwavelength engineered phase-shifting scatters, have been an emerging platform for advanced and functional control of electromagnetic (EM) waves by manipulating the local properties of amplitude, phase, and polarization of the reflected or transmitted waves. [12][13][14][15][16][17][18][19] Nowadays, with the rapid development of modern wireless and optical technologies, increasing demands on high communication speed/quality, large data storage capacity are urgently required. [12][13][14][15][16][17][18][19] Nowadays, with the rapid development of modern wireless and optical technologies, increasing demands on high communication speed/quality, large data storage capacity are urgently required.

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