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    Polarization insensitive and broadband terahertz absorber using graphene disks

    , Article Plasmonics ; Volume 12, Issue 2 , 2017 , Pages 393-398 ; 15571955 (ISSN) Arik, K ; AbdollahRamezani, S ; Khavasi, A ; Sharif University of Technology
    Springer New York LLC  2017
    Abstract
    We demonstrate design and characterization of a polarization-independent ultra-broadband absorber of light consisting of periodic array of graphene disks on top of a lossless quarter-wavelength dielectric spacer placed on a metallic reflector. The absorber is duly designed based on impedance matching concept by proposing a fully analytical circuit model resulting in a normalized bandwidth of 100 % in the terahertz regime. © 2016, Springer Science+Business Media New York  

    Beam manipulation by hybrid plasmonic-dielectric metasurfaces

    , Article Plasmonics ; 2019 ; 15571955 (ISSN) Arik, K ; Hemmatyar, O ; Kavehvash, Z ; Sharif University of Technology
    Springer  2019
    Abstract
    A hybrid plasmonic-dielectric metasurface is proposed in order to manipulate beam propagation in desired manners. The metasurface is composed of patterned hybrid graphene-silicon nano-disks deposited on a low-index substrate, namely silica. It is shown that the proposed hybrid metasurface simultaneously benefits from the advantages of graphene-based metasurfaces and dielectric ones. Specially, we show that the proposed hybrid metasurface not only provides reconfigurability, just like previously proposed graphene-based metasurfaces, but also similar to dielectric metasurfaces, is of low loss and CMOS-compatible. Such exceptional features give the metasurface exceptional potentials to realize... 

    Beam manipulation by hybrid plasmonic-dielectric metasurfaces

    , Article Plasmonics ; Volume 15, Issue 3 , 2020 , Pages 639-645 Arik, K ; Hemmatyar, O ; Kavehvash, Z ; Sharif University of Technology
    Springer  2020
    Abstract
    A hybrid plasmonic-dielectric metasurface is proposed in order to manipulate beam propagation in desired manners. The metasurface is composed of patterned hybrid graphene-silicon nano-disks deposited on a low-index substrate, namely silica. It is shown that the proposed hybrid metasurface simultaneously benefits from the advantages of graphene-based metasurfaces and dielectric ones. Specially, we show that the proposed hybrid metasurface not only provides reconfigurability, just like previously proposed graphene-based metasurfaces, but also similar to dielectric metasurfaces, is of low loss and CMOS-compatible. Such exceptional features give the metasurface exceptional potentials to realize... 

    Design and simulation of a dynamically tunable 1× 2 power splitter using MZI configuration in the telecom regime

    , Article OSA Continuum ; Volume 2, Issue 4 , 2023 , Pages 956-977 ; 25787519 (ISSN) Arik, K ; Akbari, M ; Khavasi, A ; Sharif University of Technology
    Optica Publishing Group (formerly OSA)  2023
    Abstract
    We propose an ultra-broadband, ultra-compact and a dynamically tunable 1 × 2 power splitter on a silicon on Insulator (SOI) platform with a 220 nm thick silicon light-guiding layer, using two multimode interference (MMI) couplers connected with graphene-based waveguides as the phase-tuning section through a Mach-Zehnder Interferometer (MZI) configuration. First, we theoretically present and demonstrate a novel design for the MMI couplers by combining the plane wave expansion method (PWEM) and the mode expansion conjecture concept. To verify the proposed theory, a center-fed 1 × 2 MMI coupler and a 2 × 2 MMI coupler, respectively, as the input and output sections of our proposed device, are... 

    Beam focusing using two-dimensional graphene-based meta-reflect-array

    , Article 24th Iranian Conference on Electrical Engineering, ICEE 2016, 10 May 2016 through 12 May 2016 ; 2016 , Pages 613-616 ; 9781467387897 (ISBN) Zangeneh Nejad, F ; Abdollahramezani, S ; Arik, K ; Khavasi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    A highly efficient two-dimensional meta-reflect-array manipulating the phase and amplitude of far-infrared electromagnetic wave is proposed. The reflect array consists of patterned graphene nano-disks resides on a subwavelenght thick optical cavity to enhance the interaction of electromagnetic wave. It is shown that the reflected wave from each unit cell can almost cover the 2π range phase shift by changing the radius of the graphene nano-disks while at the same time maximizes its amplitude. Proposing a transmission line model for the proposed structure, we realize a meta lens as a flat optics functionality. © 2016 IEEE  

    Tunable leaky-wave radiation by graphenecovered corrugated surfaces

    , Article Applied Optics ; Volume 57, Issue 30 , 2018 , Pages 8971-8977 ; 1559128X (ISSN) Tavakol, M. R ; Saba, A ; Arik, K ; Khavasi, A ; Sharif University of Technology
    OSA - The Optical Society  2018
    Abstract
    we propose a graphene-covered subwavelength metallic grating where the Fermi level of graphene is sinusoidally modulated as a leaky-wave antenna at terahertz frequencies. This structure can convert spoof surface plasmon guided waves to free-space radiation due to the tunability of graphene. Analysis and design of the proposed leaky-wave antenna are discussed based on sinusoidally modulated surface impedance. The surface impedance is obtained by an analytical circuit model. The sinusoidal surface impedance is realized using modulation of the conductivity of graphene by applying a bias voltage. The proposed leaky-wave antenna is capable of electronic beam scanning with an almost constant gain... 

    Design and Simulation of Electromagnetic Wave Broadband Absorbers Using Metallic and Graphene-based Structures Based on Circuit Theory

    , M.Sc. Thesis Sharif University of Technology Arik, Kamaloddin (Author) ; Khavasi, Amin (Supervisor) ; Rejaei, Behzad (Co-Advisor)
    Abstract
    In this dissertation, we design and simulate Electromagnetic (EM) wave absorbers using periodic array of ultra-thin metallic ribbons, metallic disks and graphene disks based on circuit theory. The equivalent circuit for EM structures significantly eliminates the requirement of systems with advanced hardwares. Firstly, we categorize the metallic absorbers in the literature in two types: narrowband absorbers and broadband absorbers. Surface plasmon polariton, magnetic resonance, interference theory and localized surface plasmon are employed to illustrate the mechanism behind the narrowband absorption. Therefore, they will be the basis for classifying the narrowband absorbers in this work.... 

    Design of mid-infrared ultra-wideband metallic absorber based on circuit theory

    , Article Optics Communications ; Volume 381 , 2016 , Pages 309-313 ; 00304018 (ISSN) Arik, K ; Abdollahramezani, S ; Farajollahi, S ; Khavasi, A ; Rejaei, B ; Sharif University of Technology
    Elsevier B.V  2016
    Abstract
    An ultra-broadband absorber of light is proposed by using periodic array of ultra-thin metallic ribbons on top of a lossless quarter-wavelength dielectric spacer placed on a metallic reflector. We propose a fully analytical circuit model for the structure, and then the absorber is duly designed based on the impedance matching concept. As a result, normalized bandwidth of 99.5% is realized by the proposed absorbing structure in mid-infrared regime. Performing a numerical optimization algorithm, we could also reach to normalized bandwidth of 103%  

    Circuit model for plasmons on graphene with one-dimensional conductivity profile

    , Article IEEE Photonics Technology Letters ; Volume 28, Issue 3 , 2016 , Pages 355-358 ; 10411135 (ISSN) Farajollahi, S ; AbdollahRamezani, S ; Arik, K ; Rejae, B ; Khavasi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    The scattering of graphene surface plasmons normally incident on a line discontinuity in graphene surface conductivity is investigated. The effect of the length of the transition region on the reflection and transmission coefficients is studied. It is shown that the reflection coefficient is reduced by widening the transition region. Based on the results obtained, a transmission line model is derived for the graphene sheet in which the discontinuity is represented by a simple circuit. This model is next used to design graphene-based bandpass and bandstop filters with arbitrary bandwidth in the terahertz regime