基于石墨烯振幅可调的宽带类电磁诱导透明超材料设计

基于石墨烯的电控特性提出了一种由金属线谐振器和"H"型谐振器组成的宽带可调的类电磁诱导透明(类EIT)超材料结构.首先,利用CST Microwave Studio软件对该超材料结构的透射特性进行了仿真.该结构在1.05—1.46 THz内的透射窗由金属线谐振器的等离子谐振和"H"型谐振器的电感-电容谐振干涉相消引起,且暗模式谐振器的数量增多导致了透射窗带宽的增加.其次,仿真模拟了该结构在不同石墨烯费米能级下的透射特性.当石墨烯费米能级由0 eV逐渐增加到1.5 eV时,该结构透射窗在1.05—1.46 THz内的平均透射振幅由87%逐渐减少到25%,实现了宽带可调.同时,通过仿真模拟该结构在1.26 THz下的电场分布对其透射机理进行了分析,并实验制备了类EIT超材料结构样品,且利用太赫兹时域光谱对样品进行了透射性能测试,测试结果与仿真分析的趋势基本一致.

Tunable grapheme amplitude based broadband electromagnetically-induced-transparency-like metamaterial

Metamaterials, composed of subwavelength resonators, have extraordinary electromagnetic properties which rely on the sizes and shapes of the resonance structures rather than their compositions. Recently, achieving electromagnetically induced transparency (EIT) in metamaterial system, also called electromagnetically-induced-transparency-like (EIT-like) analogue, has attracted intense attention. Many studies of EIT-like metamaterials have been reported at microwave, terahertz, and optical frequencies numerically and experimentally. However, most of the EIT-like metamaterials can only control the transmission window by changing the structure size of the metamaterial which restricts the practical applications of the EIT-like metamaterial. Therefore, a broadband tunable EIT-like metamaterials based on graphene in terahertz band is presented in this paper, which consists of a cut-wire as the bright resonator and two couples of H-shaped resonators in mirror symmetry as the dark resonators. The transmissivity of the metamaterial structure is simulated by the software CST Microwave Studio. And the simulation results show that the transmission window of this structure is in a frequency range from 1.05 THz to 1.46 THz, which is attributed to the interference between the plasmon resonance of wire resonators and the LC resonance of H-shaped resonators. In addition, increasing the number of dark mode resonators leads to an increase in transmission window bandwidth. Furthermore, a broadband tunable property of transmission amplitude is realized by changing the Fermi level of graphene. When the graphene Fermi level gradually increases from 0 eV to 1.5 eV, the transmission amplitude of the transmission window gradually decreases from 87% to 20%, which realizes the broadband tunability of transmission window. At the same time, the distribution of the electric field at a central frequency of 1.26 THz is simulated to analyse the transmission mechanism. Finally, the EIT metamaterial samples are prepared and the transmission curves of the samples are tested by terahertz time-domain spectroscopy. Such an EIT-like metamaterial not only realizes the broadband EIT property but also realizes the characteristic of the tunable amplitude of the transmission window, which has potential applications in designing the active slow-light devices, terahertz active filtering and terahertz modulator.