Nanophotonics (Mar 2022)

Gate-tuned graphene meta-devices for dynamically controlling terahertz wavefronts

  • Li Qiushi,
  • Cai Xiaodong,
  • Liu Tong,
  • Jia Min,
  • Wu Qiong,
  • Zhou Haoyang,
  • Liu Huanhuan,
  • Wang Qianqian,
  • Ling Xiaohui,
  • Chen Cong,
  • Ding Fan,
  • He Qiong,
  • Zhang Yuanbo,
  • Xiao Shiyi,
  • Zhou Lei

DOI
https://doi.org/10.1515/nanoph-2021-0801
Journal volume & issue
Vol. 11, no. 9
pp. 2085 – 2096

Abstract

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Dynamical controls on terahertz (THz) wavefronts are crucial for many applications, but available mechanism requests tunable elements with sub-micrometer sizes that are difficult to find in the THz regime. Here, different from the local-tuning mechanism, we propose an alternative approach to construct wavefront-control meta-devices combining specifically designed metasurfaces and globally tuned graphene layers. Coupled-mode-theory (CMT) analyses reveal that graphene serves as a tunable loss to drive the whole meta-device to transit from one functional phase to another passing through an intermediate regime, exhibiting distinct far-field (FF) reflection wavefronts. As a proof of concept, we design/fabricate a graphene meta-device and experimentally demonstrate that it can reflect normally incident THz wave to pre-designed directions with different polarizations under appropriate gating voltages. We finally design a graphene meta-device and numerically demonstrate that it can generate vectorial THz beams with continuously varying polarization distributions upon gating. These findings pave the road to realizing a wide range of THz applications, such as sensing, imaging, and wireless communications.

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