Non‐Interleaved Polarization‐Frequency Multiplexing Metasurface for Multichannel Holography

Abstract

spatial resolution, abundant information capacity, and high-level encryption, which could surpass the limitations of conventional holography techniques. [12,13] By etching an array of nano-structures in a metallic film on a substructure, diverse ultra-thin metasurfaces that operate range from microwave to visible light were proposed and fabricated, which can modulate both phase and amplitude of light and generate high-resolution holographic images. Based on the Pancharatnam-Berry phase, a broadband reflective-type metasurface has been developed to generate two symmetrical and helicity-dependent holographic images with high efficiency. [14] Nevertheless, those metasurfaces mentioned above have only one phase channel for information encoding, which cannot meet the increasing demands of multichannel communication and high-density data storage of modern optical technologies.In order to increase the information capacity and density, it is highly desired to achieve multiple information channels over a single metasurface. Recently, polarization multiplexed metasurfaces were proposed and demonstrated with dual-or multi-channels vectorial holographic displays for linearly polarized (LP) or circularly polarized (CP) waves and negligible polarization cross-talk, which provides new avenues for optical encryption and anti-counterfeiting. [15][16][17][18][19][20][21][22][23][24][25][26][27] Besides, frequency multiplexed metasurfaces, whose constituent elements usually possess multiple resonant modes that are each generated individually at different frequencies, can also achieve multiple independent holographic channels. [28][29][30][31][32][33][34][35] More recently, spatial multiplexing [36][37][38] and momentum multiplexing [39] have also been exploited to enhance the channel capacity of metasurfaces. Nevertheless, the aforementioned multiplexing techniques could modulate the only single degree of freedom (DoF) of EM waves. Hence, various compound multiplexing and active driving techniques have been proposed and implemented to further increase the channel capacity of metasurfaces such as polarization and frequency multiplexing, [40][41][42][43] polarization and spatial multiplexing, [44][45][46][47] reconfigurable technique, [46][47][48][49][50][51] and programmable technique. [52][53][54] By virtue of compact geometry, large channel capacity, and lower crosstalk, polarization and frequency multiplexed metasurfaces have been studied extensively, from linear polarization to circular polarization, from microwave, terahertz to optical band. However, in order to relieve the interference between different frequency bands, most frequency multiplexed metasurfaces are constructed by In order to enhance channel capacity in modern wireless communications, diverse multiplexing techniques, such as polarization, frequency, and spatial multiplexing, are proposed and implemented. Here, a non-interleaved polarization-frequency multiplexing metasurface is proposed, which can realize independent controls of orthogonal linearly polarized or c...

Frequency‐Multiplexed Holographic‐Reflective Coding Metasurface for Independent Controls of Surface Wave and Spatially Propagating Wave

“…[40][41][42] In addition, the multiplexed metasurface for mathematical operations and imaging processing is also widely explored, which can be a promising candidate for highly efficient analog processors to implement parallel computing tasks. [43,44] However, these multiplexed metasurfaces are either only based on phase and amplitude modulations to control SPW [31][32][33][38][39][40][41][42][43][44] or based on surface impedance modulation to control SW, [34][35][36][37] and the research on multiplexed metasurface that can control both SPW and SW simultaneously is still very limited. In 2019, we proposed aIn recent years, frequency-multiplexed metasurfaces have received extensive attention due to the increasing demands for device integration and communication capacity.…”

“…[26][27][28][29] The surface impedance of holographic metasurface is modulated periodically to radiate surface waves (SW) to leaky waves with different polarizations and directions. Similar to the reflective (or transmissive) metasurfaces with discrete phase distributions, the value of surface impedance can also be discretized and the radiative properties of the holographic antenna will be maintained, [30] which simplifies the design and fabrication process and provides a possible way for the development of reconfigurable holographic antennas.Recently, with the increasing demands for device integration and communication capacity, more and more multiplexed metasurfaces have been proposed, including the frequencymultiplexed metasurfaces, [31][32][33][34][35] polarization-multiplexed metasurfaces, [36][37][38][39] and space-multiplexed metasurfaces. [40][41][42] In addition, the multiplexed metasurface for mathematical operations and imaging processing is also widely explored, which can be a promising candidate for highly efficient analog processors to implement parallel computing tasks.…”

Spin‐ and Space‐Multiplexing Metasurface for Independent Phase Controls of Quadruplex Polarization Channels

“…To solve this problem, a method combining propagation and geometric phases is proposed to decouple the correlation between phase shifts of LCP and RCP waves, so as to achieve two independent polarization channels, [38][39][40] which provides more degrees of freedom for controlling the CP waves and designing multifunctional metasurfaces. [41][42][43][44] Furthermore, by introducing the concept of chirality-assisted phase and synthesizing with propagation phase and geometric phase, metasurface can be designed to achieve completely independent wavefront manipulation in all four different CP channels in transmission. [45] However, all above mentioned works can only manipulate EM waves in the transmission space or reflection space.…”

Highly Efficient Decoupled Triple‐Channel OAM Generation with a Single‐Layer Shared Aperture Reflective Metasurface

“…In recent years, metasurface-based highly integrated multichannel multiplexing (e.g., frequency-polarization multiplexing) is the general trend for modern wireless communication to realize high information capacity. [19] Many metasurface-based OAM generator have been proposed, which are realized by singlepolarization frequency multiplexing, [20,21] single-band polarization multiplexing, [22,23] dual-linearly polarized (LP) dual-band techniques, [24,25] dual-circularly polarized (CP) dual-band techniques, [26,27] as well as active components loading. [28,29] Nevertheless, these metasurfaces are limited by LP-only or CP-only modulation, which neglect the joint multiplexing of LP-OAM and CP-OAM to further enhance channel capacity.…”

“…[28,29] Nevertheless, these metasurfaces are limited by LP-only or CP-only modulation, which neglect the joint multiplexing of LP-OAM and CP-OAM to further enhance channel capacity. Subarray, [30] radial stitching, [31] and multilayer [19] techniques have been used to achieve independent multiplexing of LP and CP in two different bands. Nonetheless, the commonly used Pancharatnam-Berry (PB) phase meta-atoms for CP channel rely on dynamic rotation to manipulate wavefront, which tend to compress the available space of the lattice and are prone to footprint collisions with LP subunits.…”