title: Ultra-high modulation depth exceeding 2,400% in optically controlled topological surface plasmons.
abstract: Modulating light via coherent charge oscillations in solids is the subject of intense research topics in opto-plasmonics. Although a variety of methods are proposed to increase such modulation efficiency, one central challenge is to achieve a high modulation depth (defined by a ratio of extinction with/without light) under small photon-flux injection, which becomes a fundamental trade-off issue both in metals and semiconductors. Here, by fabricating simple micro-ribbon arrays of topological insulator Bi2Se3, we report an unprecedentedly large modulation depth of 2,400% at 1.5 THz with very low optical fluence of 45 μJ cm(-2). This was possible, first because the extinction spectrum is nearly zero due to the Fano-like plasmon-phonon-destructive interference, thereby contributing an extremely small denominator to the extinction ratio. Second, the numerator of the extinction ratio is markedly increased due to the photoinduced formation of massive two-dimensional electron gas below the topological surface states, which is another contributor to the ultra-high modulation depth.
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Sangwan
authors.initials: S
authors.lastname: Sim
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Houk
authors.initials: H
authors.lastname: Jang
authors.affiliation: Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Nikesh
authors.initials: N
authors.lastname: Koirala
authors.affiliation: Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Brahlek
authors.affiliation: Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Jisoo
authors.initials: J
authors.lastname: Moon
authors.affiliation: Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.|Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Ji Ho
authors.initials: JH
authors.lastname: Sung
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Jun
authors.initials: J
authors.lastname: Park
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Soonyoung
authors.initials: S
authors.lastname: Cha
authors.affiliation: Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.|Institute for Advanced Materials, Devices and Nanotechnology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Seongshik
authors.initials: S
authors.lastname: Oh
authors.affiliation: Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.|Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.|Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Moon-Ho
authors.initials: MH
authors.lastname: Jo
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Jong-Hyun
authors.initials: JH
authors.lastname: Ahn
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Hyunyong
authors.initials: H
authors.lastname: Choi