Liu Xueying, Xie Yinong, Qiu Jinlin, Chen Wei, Liu Yineng, Zhu Jinfeng
Institute of Electromagnetics and Acoustics and Key Laboratory of Electromagnetic Wave Science and Detection Technology, Xiamen University, Xiamen 361005, China.
Key Laboratory of Grain Information Processing and Control, College of Information Science and Engineering, Henan University of Technology, Zhengzhou 450001, China.
Nanophotonics. 2023 Nov 6;12(23):4319-4328. doi: 10.1515/nanoph-2023-0500. eCollection 2023 Nov.
Graphene aerogels have implied great potential for electromagnetic wave absorption. However, the investigation of their design for broadband absorption in the terahertz (THz) range remains insufficient. Here, we propose an anisotropic honeycomb stack metamaterial (AHSM) based on graphene to achieve ultrawideband THz absorption. The absorption mechanism is elucidated using the effective medium method, offering deeper physics insights. At low THz frequencies, the impedance matching from the air to the AHSM can be improved by reducing the chemical potential of graphene for high absorption. There is a suppression of absorption at the intermediate frequencies due to constructive interference, which can be avoided by shortening the sizes of honeycomb edges. With the aim to elevate absorption at high frequencies, one can increase the stack layer number to enhance multiple reflections and destructive interference within the metastructure. Based on the above principles, we design an AHSM that achieves a broadband absorbance of over 90 % from 1 THz to 10 THz. This absorption can tolerate a wide range of incident angles for both TE and TM wave excitations. Our research will provide a theoretical guide to future experimental exploration of graphene aerogels for THz metamaterial absorber applications.
石墨烯气凝胶在电磁波吸收方面展现出了巨大潜力。然而，对其在太赫兹（THz）频段的宽带吸收设计的研究仍显不足。在此，我们提出一种基于石墨烯的各向异性蜂窝堆叠超材料（AHSM），以实现超宽带太赫兹吸收。利用有效介质方法阐明了吸收机制，提供了更深入的物理见解。在低太赫兹频率下，通过降低石墨烯的化学势可改善从空气到AHSM的阻抗匹配，从而实现高吸收。由于相长干涉，在中频处吸收会受到抑制，可通过缩短蜂窝边缘尺寸来避免这种情况。为提高高频处的吸收，可增加堆叠层数，以增强亚结构内的多次反射和相消干涉。基于上述原理，我们设计了一种AHSM，在1太赫兹至10太赫兹范围内实现了超过90%的宽带吸收率。这种吸收对于TE波和TM波激发都能容忍很宽的入射角范围。我们的研究将为未来石墨烯气凝胶用于太赫兹超材料吸收器应用的实验探索提供理论指导。
