基于石墨烯编码超构材料的太赫兹波束多功能动态调控

提出了一种基于石墨烯带的太赫兹波段的1 bit编码超构材料,可以实现太赫兹波束的数目、频率、幅度等参数多功能动态调控.该结构由金属薄膜、聚酰亚胺、硅、二氧化硅、石墨烯带组成.通过对石墨烯带施加两种不同的电压,可以实现一定频率范围内相位差接近180?的"0"和"1"数字编码单元,进而构成1 bit动态可控的编码超构材料.全波仿真结果表明,不同序列的编码超构材料能够实现波束数目从单波束、双波束、多波束到宽波束的调控.相同序列的编码超构材料,通过施加石墨烯带的不同电压能够实现宽频段波束频率的偏移.对于000000或者111111周期序列的编码超构材料,通过施加石墨烯带的不同电压还能够实现波束幅度的调控.因此这种基于石墨烯带的编码超构材料为灵活调控太赫兹波提供了一种新的途径,将在雷达隐身、成像、宽带通信等方面具有重要的意义.

Dynamic multifunctional control of terahertz beam based on graphene coding metamaterial

Terahertz (THz) waves have aroused tremendous research interest due to its some unique features and widespread applications in broadband communication, military radar, non-destructive detection, biomedical, security check, etc. With the development of THz applications, dynamic control beam of THz wave with wide bandwidth and multifunction has become a key issue in the field THz technology. The metamaterial with a kind of artificial material provides an approach to controlling the terahertz beam. However, the characteristics of metamaterials based on the equivalent medium parameters are limited by the structural configuration, which usually causes disadvantageous problems including the real-time dynamic control, narrow bandwidth, modulating efficiency, complicated design, etc. The coding metamaterial based digital elements provide an approach to wideband and flexible control terahertz wave by different sequences. However, the THz waves are still hard to tune in dynamic ways due to the limitation of material properties and processing capability. Graphene with a new two-dimensional material has excellent photoelectric properties such as tunable band gap, flexibly dynamic performance, and low material loss. Therefore, the graphene with coding metamaterial can offer a new way of dynamically controlling beam. In this paper, we design a 1 bit coding metamaterial based on graphene ribbon, which can be expected to realize multi-modulation to the number of beams, frequency and amplitude of THz wavers. The mechanism of controlling electromagnetic wave by coding metamaterial can be explained by the reflective array antenna. And the characteristics of the proposed metamaterial based on the graphene ribbon and the far-field scattering of coding metamaterial are simulated using the CST Microwave Studio. A composite structure which consists of gold metal, polyimide, silicon, silicon dioxide, graphene ribbon is designed and characterized in the THz range. The simulation results show that by gating different graphene ribbons, the coding state (digital element) on each column can be independently controlled as well, thus the ‘0’ and ‘1’ digital elements with a phase difference of 180° in a certain frequency range can be realized, and then the coding sequence on metamaterials is dynamically modulated. Full-wave simulation results also show that different-sequence coding metamaterials can achieve the control of the number of scattering THz beams, from one, double, multi scattering in a wide frequency range (from 1.7 to 2.2 THz). For coding sequence ‘010101...’ realized by gating different voltages on coding elements ‘0’ and ‘1’, the frequency at which double scattering beams are produced, presents shift. For the coding metamaterial of periodic sequence of 000000 or 111111 with different voltage for different graphene ribbon, which can be expected to realize amplitude modulation from -12 dB to -23 dB of THz beam steering at f₁=1 THz. Therefore, this graphene coding metamaterial can control the THz beam flexibly and may offer widespread applications in stealth, imaging, and broadband communication of THz frequencies.