Nano Lett. 2018 May 9;18(5):2957-2963. doi: 10.1021/acs.nanolett.8b00351. Epub 2018 Apr 9.
Active metasurfaces composed of electrically reconfigurable nanoscale subwavelength antenna arrays can enable real-time control of scattered light amplitude and phase. Achievement of widely tunable phase and amplitude in chip-based active metasurfaces operating at or near 1550 nm wavelength has considerable potential for active beam steering, dynamic hologram rendition, and realization of flat optics with reconfigurable focal lengths. Previously, electrically tunable conducting oxide-based reflectarray metasurfaces have demonstrated dynamic phase control of reflected light with a maximum phase shift of 184° ( Nano Lett. 2016 , 16 , 5319 ). Here, we introduce a dual-gated reflectarray metasurface architecture that enables much wider (>300°) phase tunability. We explore light-matter interactions with dual-gated metasurface elements that incorporate two independent voltage-controlled MOS field effect channels connected in series to form a single metasurface element that enables wider phase tunability. Using indium tin oxide (ITO) as the active metasurface material and a composite hafnia/alumina gate dielectric, we demonstrate a prototype dual-gated metasurface with a continuous phase shift from 0 to 303° and a relative reflectance modulation of 89% under applied voltage bias of 6.5 V.
由电可重构纳米级亚波长天线阵列组成的主动超表面可以实现对散射光幅度和相位的实时控制。在工作于或接近 1550nm 波长的基于芯片的主动超表面中实现广泛可调谐的相位和幅度，对于主动光束转向、动态全息渲染以及实现具有可重构焦距的平面光学具有相当大的潜力。此前，基于电可调谐导电氧化物的反射阵超表面已经展示了对反射光的动态相位控制，最大相移为 184°（Nano Lett. 2016,16,5319）。在这里，我们引入了一种双门控反射阵超表面架构，实现了更宽的（>300°）相位可调性。我们探索了具有双门控超表面元件的光物质相互作用，这些元件包含两个独立的电压控制 MOS 场效应通道，串联连接形成单个超表面元件，从而实现更宽的相位可调性。我们使用氧化铟锡（ITO）作为有源超表面材料和复合氧化铪/氧化铝栅介质，演示了一个原型双门控超表面，在 6.5V 的外加电压偏置下，连续相移从 0 到 303°，相对反射率调制为 89%。
