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.

中文翻译：

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用于动态控制太赫兹波前的栅极调谐石墨烯元器件

太赫兹 (THz) 波前的动态控制对于许多应用来说至关重要，但可用的机制需要在太赫兹范围内难以找到的亚微米尺寸的可调元件。在这里，不同于本地调优机制，我们提出了一种替代方法来构建波前控制元器件，结合专门设计的超表面和全球调谐石墨烯层。耦合模式理论 (CMT) 分析表明，石墨烯作为一种可调节的损耗来驱动整个元器件从一个功能相过渡到另一个通过中间状态的功能相，表现出明显的远场 (FF) 反射波前。作为概念验证，我们设计/制造了一个石墨烯元器件，并通过实验证明它可以在适当的门控电压下将正常入射的太赫兹波反射到具有不同极化的预先设计的方向。我们最终设计了一个石墨烯元器件，并在数值上证明它可以在选通时产生具有连续变化的偏振分布的矢量太赫兹光束。这些发现为实现广泛的太赫兹应用铺平了道路，例如传感、成像和无线通信。