High Efficiency Polarization‐Encoded Holograms with Ultrathin Bilayer Spin‐Decoupled Information Metasurfaces

Abstract

Information metasurfaces, including digital coding and programmable metasurfaces, have reformed the design theory of metasurfaces from effective medium to coding pattern, and bridged the physical and digital world. Metasurface hologram has shown great potential in imaging and manipulating electromagnetic waves. In this work, bilayer information metasurfaces are proposed to achieve polarization‐encoded holograms in microwave regime. The designed metasurfaces consist of 3‐bit spin‐decoupled meta‐atoms, which possess ultrathin profiles (0.14λ0) and high cross‐polarization transmittance (over 0.8). The incident wave, which is right‐handed circularly polarized or left‐handed circularly polarized, is encoded with code “0” or “1”. The spin‐decoupled design is combined with diffuse scattering and holographic technology. Based on this, a novel algorithm is proposed to generate coding sequences according to the code of incident wave, to achieve different functionalities for corresponding circularly polarized channels. In this way, polarization‐encoded holograms, including diffuse scattering holograms (code “00”), single channel holograms (code “01” or “10”), and spin‐selective holograms (code “11”), are achieved. Simulated and measured results show that the maximum imaging efficiency can reach up to 65.1%, verifying the high efficiency of this holographic technology. This work is expected to open a way of realizing more complicated and higher efficiency information metasurface holography.

Metasurface Holography in the Microwave Regime

“…The improved GSW algorithm is used to calculate the interface phase distribution in order to achieve identical multiplexed functionality for both the transmitted co-and cross-polarized components. A bilayer spin-decoupled information metasurface, shown in Figure 6a, has also been designed as an ultrathin structure with the amplitude of cross-polarization transmittance higher than 0.8 [111]. In this case, the incidence could be an RCP or LCP wave encoded with code "0" or "1".…”

“…The spin-decoupled design was creatively combined with diffuse scattering and holographic technology in order to achieve different functionalities for corresponding circularly polarized channels. [111]. Copyright 2020 John Wiley and Sons.…”

“…(a) A spin-selective transmission polarization-encoded hologram. Reprinted with permission from ref [111]…”

Multidimensionally Manipulated Active Coding Metasurface by Merging Pancharatnam–Berry Phase and Dynamic Phase

“…The proposal of the generalized Snell's laws [3] leads to the unprecedented development of metasurface, and many fascinating phenomena are achieving, such as random diffusions, [4][5][6] orbital angular momentum, [7] beam deflection, [8][9][10][11] vortex beams, [12][13][14] wavefront manipulation, [15][16][17] and holograms. [18][19] Recently, the concept of coding metasurface (CM) was proposed, which used the binary code to characterize the phase. [20] By introducing active materials into the metasurface, diversified functionalities can be achieved rapidly and effectively.…”

Broadband Spin-Selective Wavefront Manipulations Based on Pancharatnam–Berry Coding Metasurfaces

“…Metasurfaces are composed of two-dimensional (2D) subwavelength artificial elements and have attracted much attention in recent years due to their powerful ability in the manipulations of electromagnetic (EM) waves. − However, most of the traditional metasurfaces have no chirality, and thus they have the same amplitude and/or phase responses for both left- and right-handed circularly polarized (CP) waves. , The proposal of Pancharatnam–Berry (PB) metasurfaces makes it possible to control the left- and right-handed CP waves independently because the introduction of the propagation and geometric phases can break the locked spin-flipped phase limitation. − Many fantastic works have been proposed on the basis of PB metasurfaces, such as the broadband spin-decoupled reflector antenna, multichannel vectorial hologram, − multiple-input multiple-output antenna with information encryption, near-field and far-field optical imaging, , polarization-insensitive cloaking, and even helicity-delinked manipulations of surface waves …”