title: Asymmetric excitation of surface plasmons by dark mode coupling.
abstract: Control over surface plasmons (SPs) is essential in a variety of cutting-edge applications, such as highly integrated photonic signal processing systems, deep-subwavelength lasing, high-resolution imaging, and ultrasensitive biomedical detection. Recently, asymmetric excitation of SPs has attracted enormous interest. In free space, the analog of electromagnetically induced transparency (EIT) in metamaterials has been widely investigated to uniquely manipulate the electromagnetic waves. In the near field, we show that the dark mode coupling mechanism of the classical EIT effect enables an exotic and straightforward excitation of SPs in a metasurface system. This leads to not only resonant excitation of asymmetric SPs but also controllable exotic SP focusing by the use of the Huygens-Fresnel principle. Our experimental findings manifest the potential of developing plasmonic metadevices with unique functionalities.
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Xueqian
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Li
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Yuehong
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Gu
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Tian
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Chunmei
authors.initials: C
authors.lastname: Ouyang
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
authors.forename: Yongmin
authors.initials: Y
authors.lastname: Liu
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Shuang
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Xixiang
authors.identifier: 0000-0002-3478-6414
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.
authors.forename: Jiaguang
authors.initials: J
authors.lastname: Han
authors.affiliation: Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.; School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Weili
authors.initials: W
authors.lastname: Zhang
keywords: Surface plasmons; asymmetric excitation; coupling; dark mode; near field; terahertz