Soleymani Sina, Güngördü M Zeki, Kung Patrick, Kim Seongsin M
Electrical and Computer Engineering Department, University of Alabama, Tuscaloosa, 35487, USA.
Sci Rep. 2019 Feb 4;9(1):1249. doi: 10.1038/s41598-018-37562-y.
Infrared metasurface anomalous reflector with ultra-high efficiency and broad band operation is designed via multi-sheet graphene layer with triangular holes. The anomalous reflection angle covers the range of 10° to 90° with the efficiency higher than 80%, over a broad spectral range from 7 μm-40 μm of infrared spectrum. It reaches above 92% at the center wavelength in the spectral response. By increasing the periodicity of phase gradient, we can expand this frequency band even further without losing efficiency. The compact design of metasurface affords the adjustability of the electrochemical potential level of graphene by means of gating. Additionally, the impact of the number of graphene sheets for the optimum efficiency of the proposed structure is investigated. By adding the secondary graphene metasurface with opposite direction of phase gradient, we demonstrated the tunability of the reflection angle from θ to -θ with bias voltage.
通过具有三角形孔的多层石墨烯层设计了具有超高效率和宽带运行的红外超表面异常反射器。异常反射角覆盖10°至90°的范围，在7μm - 40μm的宽红外光谱范围内效率高于80%。在光谱响应的中心波长处达到92%以上。通过增加相位梯度的周期性，我们可以在不损失效率的情况下进一步扩展该频带。超表面的紧凑设计通过门控提供了石墨烯电化学势水平的可调性。此外，还研究了石墨烯层数对所提出结构最佳效率的影响。通过添加具有相反相位梯度方向的二次石墨烯超表面，我们展示了反射角随偏置电压从θ可调至 -θ。
