Empowered Layer Effects and Prominent Properties in Few‐Layer Metasurfaces

Abstract

applications have been realized based on the metamaterials, such as negative index materials, [3] invisibility cloaks, [4] and zeroindex materials. [5] Nevertheless, metamaterials are usually bulky, difficult to be fabricated, and suffer from high energy losses, which hinder their practical applications in modern photonic systems. In recent years, planar metasurfaces, the 2D equivalents of metamaterials, have attracted plenty of attentions due to their extraordinary abilities in controlling the polarization, amplitude, phase, and dispersion of electromagnetic waves. [6][7][8] Compared with bulk metamaterials, the metasurfaces have many advantages, such as ultrathin thicknesses, low losses, ease of fabrication and integration. Over the past years, single-layer metasurfaces have been widely applied in realizing polarization conversion, [9] beam deflectors, [10,11] metalenses, [12,13] holograms, [14] coding, [15] structural colors, [16,17] nonlinear metasurfaces, [18] and some other applications. Nevertheless, the interactions between lights and ultrathin single-layer metasurfaces are usually limited, resulting in low efficiency and limited controllability in some applications. [19] Moreover, the degrees of freedom for light manipulation provided by a single-layer metasurface are usually not enough in realizing multifunctional devices and some other sophisticated photonic systems.Few-layer metasurface that contains more than one functional layer provides an effective method to overcome the drawbacks of both bulk metamaterials and single-layer metasurfaces. Cheng et al. employed the concept of few-layer metasurfaces to discuss the advantages and emergent functionalities of them in ref. [20]. Few-layer metasurfaces retain the advantages of single-layer metasurfaces and can provide more degrees of freedom to manipulate electromagnetic waves. More importantly, the abundant layer effects, such as the multiple wave interference between layers and the near-field coupling effects, can enhance the interactions between lights and structures and improve the efficiency of few-layer systems. In addition, the combination of different functional layers can produce novel functions that single-layer metasurfaces can hardly realize. For example, by breaking the mirror symmetry along the propagation direction, few-layer metasurfaces can realize asymmetric transmission of linearly polarized lights. [21] By vertically integrating different metasurfaces on one substrate, optical systems with different functions can be miniaturization and integration. Recently, the few-layer metasurfaces have also been extended in the acoustic fields to realize some novel applications, such Metamaterials are 3D artificial structures proposed to surpass conventional natural materials and realize novel functions beyond traditional optical elements. Nevertheless, they are usually bulky and difficult to be fabricated. As 2D equivalents of metamaterials, metasurfaces have been proposed to overcome the drawbacks of metamaterials and fully control the polarizati...

A Dynamically Modulated All‐Dielectric Metasurface Doublet for Directional Harmonic Generation and Manipulation in Transmission

“…The geometry of the metasurface doublet is depicted in Figure a where the bottom layer is embedded in a low‐index glass substrate with refractive index of n sub = 1.5 while the top layer is sitting on top of the substrate in free space. The advances in nanofabrication technologies have made the fabrication of few‐layer metasurfaces feasible and several experimental realization of such metasurfaces has been demonstrated …”

Controllable Polarization Rotator with Broadband High Transmission Using All‐Dielectric Metasurfaces

“…[14][15][16][17][18][19][20][21] To rotate the original polarization of light, a new type of polarization rotators based on plasmonic metasurfaces has been successfully realized for transmission mode. [22][23][24][25][26][27][28][29][30] More recently, it has been reported that polarization rotators composed of properly designed metasurfaces can rotate the polarization angle of the LP light to a desired angle in the same way as can be done with optically active materials. [31][32][33][34][35][36][37][38][39] For instance, Shaltout et al proposed an optical metasurface composed of planar arrays of plasmonic nanoantennas, and the phase difference between the RCP and LCP components was generated by two sets of supercells, leading to the rotation of the polarization angle to a specific value.…”

Ultra‐Sharp Circular Dichroism Induced by Twisted Layered C4 Oligomers

“…These strong chiroptical responses can be obtained by layer‐by‐layer coupling in multilayer metamaterials . For example, multilayers composed of twisted anisotropic gold nanorods are strong, broadband circular polarizers .…”