Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-751, Republic of Korea.
Center for Quantum Beam-based Radiation Research, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea.
Sci Rep. 2017 Feb 20;7:42833. doi: 10.1038/srep42833.
Graphene, which is a two-dimensional crystal of carbon atoms arranged in a hexagonal lattice, has attracted a great amount of attention due to its outstanding mechanical, thermal and electronic properties. Moreover, graphene shows an exceptionally strong tunable light-matter interaction that depends on the Fermi level - a function of chemical doping and external gate voltage - and the electromagnetic resonance provided by intentionally engineered structures. In the optical regime, the nonlinearities of graphene originated from the Pauli blocking have already been exploited for mode-locking device applications in ultrafast laser technology, whereas nonlinearities in the terahertz regime, which arise from a reduction in conductivity due to carrier heating, have only recently been confirmed experimentally. Here, we investigated two key factors for controlling nonlinear interactions of graphene with an intense terahertz field. The induced transparencies of graphene can be controlled effectively by engineering meta-atoms and/or changing the number of charge carriers through electrical gating. Additionally, nonlinear phase changes of the transmitted terahertz field can be observed by introducing the resonances of the meta-atoms.
石墨烯是一种由碳原子以六边形晶格排列而成的二维晶体，由于其出色的机械、热学和电子性能而引起了广泛关注。此外，石墨烯表现出异常强的可调谐光物质相互作用，这取决于费米能级——化学掺杂和外部栅极电压的函数——以及通过有意设计的结构提供的电磁共振。在光学波段，石墨烯的非线性源于泡利阻塞，已经被用于超快激光技术中的锁模器件应用，而由于载流子加热导致电导率降低而产生的太赫兹波段的非线性，最近才在实验上得到证实。在这里，我们研究了控制石墨烯与强太赫兹场相互作用的两个关键因素。通过工程化的亚原子结构和/或通过电门控改变载流子的数量，可以有效地控制石墨烯的诱导透明。此外，通过引入亚原子结构的共振，可以观察到透射太赫兹场的非线性相位变化。
