title: Experimental Realization of a Reflections-Free Compact Delay Line Based on a Photonic Topological Insulator.
abstract: Electromagnetic (EM) waves propagating through an inhomogeneous medium are generally scattered whenever the medium's electromagnetic properties change on the scale of a single wavelength. This fundamental phenomenon constrains how optical structures are designed and interfaced with each other. Recent theoretical work indicates that electromagnetic structures collectively known as photonic topological insulators (PTIs) can be employed to overcome this fundamental limitation, thereby paving the way for ultra-compact photonic structures that no longer have to be wavelength-scale smooth. Here we present the first experimental demonstration of a photonic delay line based on topologically protected surface electromagnetic waves (TPSWs) between two PTIs which are the EM counterparts of the quantum spin-Hall topological insulators in condensed matter. Unlike conventional guided EM waves that do not benefit from topological protection, TPSWs are shown to experience multi-wavelength reflection-free time delays when detoured around sharply-curved paths, thus offering a unique paradigm for compact and efficient wave buffers and other devices.
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Kueifu
authors.initials: K
authors.lastname: Lai
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Tsuhsuang
authors.initials: T
authors.lastname: Ma
authors.affiliation: Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.|Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742-3285, USA.
authors.forename: Xiao
authors.initials: X
authors.lastname: Bo
authors.affiliation: Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.|Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742-3285, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Anlage
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Gennady
authors.initials: G
authors.lastname: Shvets