Kim Teun-Teun, Oh Sang Soon, Kim Hyeon-Don, Park Hyun Sung, Hess Ortwin, Min Bumki, Zhang Shuang
School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 16419, Republic of Korea.
Sci Adv. 2017 Sep 29;3(9):e1701377. doi: 10.1126/sciadv.1701377. eCollection 2017 Sep.
Active control of polarization states of electromagnetic waves is highly desirable because of its diverse applications in information processing, telecommunications, and spectroscopy. However, despite the recent advances using artificial materials, most active polarization control schemes require optical stimuli necessitating complex optical setups. We experimentally demonstrate an alternative-direct electrical tuning of the polarization state of terahertz waves. Combining a chiral metamaterial with a gated single-layer sheet of graphene, we show that transmission of a terahertz wave with one circular polarization can be electrically controlled without affecting that of the other circular polarization, leading to large-intensity modulation depths (>99%) with a low gate voltage. This effective control of polarization is made possible by the full accessibility of three coupling regimes, that is, underdamped, critically damped, and overdamped regimes by electrical control of the graphene properties.
由于电磁波偏振态在信息处理、电信和光谱学等领域有着广泛应用，因此对其进行主动控制极具吸引力。然而，尽管近期在使用人工材料方面取得了进展，但大多数主动偏振控制方案都需要光学刺激，这就需要复杂的光学装置。我们通过实验证明了一种替代方法——对太赫兹波的偏振态进行直接电调谐。将手性超材料与石墨烯门控单层片相结合，我们发现具有一种圆偏振的太赫兹波的传输可以通过电控制，而不影响另一种圆偏振的传输，从而在低栅极电压下实现了高强度调制深度（>99%）。通过对石墨烯特性进行电控制，使三种耦合状态（即欠阻尼、临界阻尼和过阻尼状态）完全可达，从而实现了对偏振的有效控制。
