title: A broadband terahertz ultrathin multi-focus lens.
abstract: Ultrathin transmission metasurface devices are designed on the basis of the Yang-Gu amplitude-phase retrieval algorithm for focusing the terahertz (THz) radiation into four or nine spots with focal spacing of 2 or 3 mm at a frequency of 0.8 THz. The focal properties are experimentally investigated in detail, and the results agree well with the theoretical expectations. The designed THz multi-focus lens (TMFL) demonstrates a good focusing function over a broad frequency range from 0.3 to 1.1 THz. As a transmission-type device based on metasurface, the diffraction efficiency of the TMFL can be as high as 33.92% at the designed frequency. The imaging function of the TMFL is also demonstrated experimentally and clear images are obtained. The proposed method produces an ultrathin, low-cost, and broadband multi-focus lens for THz-band application.
authors.affiliation: Department of Physics, Harbin Institute of Technology, Harbin, 150001, P.R. China.|Department of Physics, Capital Normal University, Beijing Key Laboratory of Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing, 100048, P.R. China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Physics, Capital Normal University, Beijing Key Laboratory of Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing, 100048, P.R. China.
authors.forename: Jiasheng
authors.initials: J
authors.lastname: Ye
authors.affiliation: Department of Physics, Harbin Institute of Technology, Harbin, 150001, P.R. China.|Department of Physics, Capital Normal University, Beijing Key Laboratory of Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing, 100048, P.R. China.
authors.forename: Xinke
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory for Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences, Beijing, 100083, P.R. China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Kan
authors.affiliation: Department of Physics, Harbin Institute of Technology, Harbin, 150001, P.R. China.|Department of Physics, Capital Normal University, Beijing Key Laboratory of Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing, 100048, P.R. China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang