Frequency-Domain and Spatial-Domain Reconfigurable Metasurface

Abstract

The recently proposed digital reconfigurable metasurfaces make it possible to manipulate electromagnetic (EM) waves flexibly. However, most existing reconfigurable metasurfaces can only exhibit a relatively single performance in the spatial domain. Here, we propose a general frequency- and spatial-domain reconfigurable metasurface (FSRM) that can manipulate the EM waves and realize reconfigurable functions in multifrequency bands. In the frequency domain, FSRM can convert different linearly polarized (LP) incident waves into left- and right-hand circularly polarized reflected waves, in which PIN diodes are used to switch the polarization conversions in different frequency bands. When the polarization direction of the incident LP wave is 45° from the +x-axis, the FSRM modulates the incident waves as a 1-bit programmable metasurface in the spatial domain. Two-dimensional beam scanning, vortex beams with orbital angular momentums, and specific beams with desired transmission directions are demonstrated via real-time adjustment of the digital coding state. To validate the modulation methodology, an FSRM prototype is fabricated and measured, which could respond to different functions for different polarization incidences. The measured results agree well with the theoretical analyses. The proposed FSRM will provide new opportunities for smart material designs.

Tunable Metasurfaces: The Path to Fully Active Nanophotonics

“…Adapted with permission. [ 217 ] Copyright 2020, American Chemical Society. c) Addressable meta‐atoms for OAM generation.…”

“…[ 216 ] An active 1‐bit 16 × 16 unit cell metasurface has been demonstrated to encode various different functions (Figure 8b). [ 217 ] The conversion of linearly polarized light to circularly polarized light in different frequency bands was shown in the frequency domain, whereas in the spatial domain, the reflection phase can be encoded, leading to flexible beam steering and switching between different OAM beams. Other similar work has also been demonstrated, [ 218 ] and there are also examples of this functionality in the THz regime.…”

Angular‐Adaptive Reconfigurable Spin‐Locked Metasurface Retroreflector

“…[ 15 ] The metasurfaces provide a flexible platform to achieve versatile wave functionalities with high performances and extraordinary capabilities that are otherwise difficult or even impossible by natural materials. [ 16 , 17 , 18 , 19 ]…”

Graphene‐Based Microwave Metasurfaces and Radio‐Frequency Devices

“…[30][31][32] As a straightforward way to achieve EM reconfigurability, the incorporation with active lumped elements (PIN or varactor diodes) at the subwavelength scale has been initially validated in metamaterials at radio frequencies and then extended to other applicative scenarios. [33][34][35][36][37][38][39][40] However, the development of reconfigurable metamaterials within active lumped elements still faces severe challenges in terms of flexibility, bandwidth, efficiency, and costs due to the mandatory need of bias networks and control logics that are crucial for practical applications of tunable metasurfaces.…”