Broadband digital coding metasurface holography

Abstract

Digital coding metasurfaces composed of subwavelength meta-atoms can flexibly control electromagnetic waves to achieve holography, which has great potential in millimeter-wave imaging systems and data storage. In this paper, we propose a 3-bit reflective digital coding metasurface. The incident linearly polarized waves can be transformed into cross-polarized components with distinct phase responses by adjusting the rotational and open angles of the coding elements. The 3-bit phase performance can be retained over a wide bandwidth from 12 to 18 GHz by simultaneously changing the rotational and open angles. Based on the proposed broadband metasurface, broadband holography is successfully demonstrated with the optimization of a modified Gerchberg–Saxton algorithm. As a proof of concept, five schemes with different holograms integrating the letters “S,” “E,” “U,” “X,” and “Z” are simulated from 12 to 18 GHz. Good simulation results validate the performance of the proposed broadband holography, showing a relative bandwidth of 40%. Two prototypes superposing the holograms of letters “U” and “X” are fabricated and measured in a near-field microwave anechoic chamber. The experimental results corroborate well with simulated results, further supporting the demonstration. We believe that the proposed broadband holography based on the digital coding metasurface paves a way to wideband applications for microwave imaging, information processing, and holographic data storage.

Electromagnetic Brain–Computer–Metasurface Holography

“…A 1-bit programmable metasurface consisting of 30*30 digital elements is used to manipulate the EM waves in the Fresnel near-field region to realize the EM holography. According to the contents of GUI buttons, the optimized holograms are calculated by using the modified Gerchberg–Saxton (GS) algorithm ,, and prestored in an FPGA, which establishes a mapping relationship between the holograms and visual buttons. The corresponding coding sequences of the holograms will be output to the programmable metasurface in realizing the metasurface holography when the FPGA receives the commands from the BCI.…”

“…11 Due to the unprecedented abilities to record and reconstruct the EM wavefronts, metasurface holography has attracted much attention and is widely utilized in 2D or three-dimensional (3D) imaging technologies. 12,13 Different types of metasurface holography have been presented, including phase-only holography, 14,15 amplitude-only holography, 16 complex amplitude holography, 17 and orbital angular momentum (OAM) holography. 18−20 However, only fixed holographical images can be reconstructed once the passive metasurfaces are fabricated.…”

“…The concept of digital coding and programmable metasurfaces was further proposed in 2014, exploring a close link between the EM physical response and digital information. , A number of fascinating works have been successively realized, such as harmonic manipulations, − self-adaptive beam scanning, , reprogrammable plasmonic topological insulators, and programmable diffractive deep neural networks (D 2 NN) . Due to the unprecedented abilities to record and reconstruct the EM wavefronts, metasurface holography has attracted much attention and is widely utilized in 2D or three-dimensional (3D) imaging technologies. , Different types of metasurface holography have been presented, including phase-only holography, , amplitude-only holography, complex amplitude holography, and orbital angular momentum (OAM) holography. − However, only fixed holographical images can be reconstructed once the passive metasurfaces are fabricated. To address this drawback, reprogrammable metasurface holography was demonstrated subsequently, which can flexibly reconstruct arbitrary holographical images in real time under the control of a high-speed field programmable gate array (FPGA). − This technology may enhance the visual immersion and reality in 2D and 3D imaging.…”

Wide Band Beam Steering Digital Metasurface Reflectarray Antenna for Millimeter Wave Applications

“…Also, using the PIN diodes at millimeter waves introduces the extreme insertion loss and the reliability of the PIN diodes adds more constraints to proper functioning of the antennas [18]. To address these issues, low cost passive metasurface reflectarray antennas are presented [19], [20]. A digital metasurface reflectarray antenna using three bit quantization for x-band applications is presented in [21].…”

Coding acoustic metasurfaces for tunable focusing in three-dimensional space

“…For coding metamaterials, they have great applications in the flexible manipulation of waves due to their powerful reconfigurability. [22][23][24][25] By combining metasurfaces and coding metamaterials, coding metasurfaces possessing the advantages of compact structure and powerful reconfigurability can be obtained. Coding metasurfaces were originally designed to manipulate electromagnetic waves.…”