Deng Yuwang, Zhou Qingli, Zhang Pujing, Jiang Nan, Ning Tingyin, Liang Wanlin, Zhang Cunlin
Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Beijing Advanced Innovation Center for Imaging Theory and Technology, Department of Physics, Capital Normal University, Beijing 100048, China.
Shandong Provincial Engineering and Technical Center of Light Manipulations & Shandong Provincial Key Laboratory of Optics and Photonic Device, School of Physics and Electronics, Shandong Normal University, Jinan 250358, China.
ACS Appl Mater Interfaces. 2021 Mar 24;13(11):13565-13575. doi: 10.1021/acsami.0c22862. Epub 2021 Mar 15.
We have demonstrated the active manipulation of metamaterial-induced transparency (MIT) in a terahertz hybrid metamaterial with graphene overlayer under photoexcitation. It is found that the introduction of graphene can greatly modify the resonant dips and transparency window through the formed depolarization field around unequal-length double bars to weaken dipole resonances and their destructive interference. Transient control of MIT behaviors is determined by the photogenerated carrier dynamics, which influences the distributions of currents and electric fields in the resonant region to hinder the near-field coupling of two bright modes. Optical modulation depth is sensitive to bar spacing due to an anomalous increased double-bar coupling involving intracell and intercell interaction. Heterointerface formed by the added graphene with substrate could further enhance terahertz response via effective separation of the photoexcited carriers. Theoretical calculation based on the coupled Lorentz oscillator model reveals that the photoinduced terahertz response mainly originates from the coupling and damping in hybrid structures. Our findings could facilitate the development of graphene-based dynamical terahertz modulators and optoelectronic devices.
我们已经证明了在光激发下，通过在太赫兹混合超材料上覆盖石墨烯，可以对超材料诱导透明（MIT）进行主动操控。研究发现，石墨烯的引入可以通过在不等长双杆周围形成的退极化场极大地改变共振凹陷和透明窗口，从而减弱偶极子共振及其相消干涉。MIT行为的瞬态控制由光生载流子动力学决定，光生载流子动力学影响共振区域中的电流和电场分布，从而阻碍两个亮模式的近场耦合。由于涉及胞内和胞间相互作用的异常增加的双杆耦合，光学调制深度对杆间距敏感。添加的石墨烯与衬底形成的异质界面可以通过光激发载流子的有效分离进一步增强太赫兹响应。基于耦合洛伦兹振荡器模型的理论计算表明，光致太赫兹响应主要源于混合结构中的耦合和阻尼。我们的研究结果可能会促进基于石墨烯的动态太赫兹调制器和光电器件的发展。
