Abstract-Analytical method for the diffraction of an electromagnetic wave by subwavelength graphene ribbons

 

Mahdi Rahmanzadeh, Amin Khavasi, and Behzad Rejaei

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-38-3-953

Theoretical study of arrays of graphene ribbons is currently of high interest due to its potential application in beam splitters, absorbers, and polarizers. In this paper, an analytical method is presented for diffraction analysis of graphene ribbon arrays. Previous analytical studies were carried out in the regime where the lateral separation between the ribbons is much smaller than the wavelength of the incident wave. As such, they cannot be used to calculate the reflection coefficients of higher diffracted orders. In contrast, the method proposed here can predict the electromagnetic response of graphene ribbon arrays even when the array constant is larger than the wavelength. To reach our results, we first derive an analytical expression for the surface density of the electric current induced on the ribbons by an incident, transverse-magnetic, plane wave. Next, closed-form and analytical expressions are obtained for the reflection coefficients of the zeroth and higher diffracted orders. The results are in excellent agreement with those obtained from full-wave simulations. The method presented facilitates the design of tunable gratings with many potential applications in the terahertz regime and optics.

© 2021 Optical Society of America

Abstract-Investigation of multiband plasmonic metamaterial perfect absorbers based on graphene ribbons by the phase-coupled method

Hongju Li, Chuansheng Ji, Yongze Ren, Jigang Hu, Meng Qin, Lingling Wang,

https://www.sciencedirect.com/science/article/pii/S0008622318309138

We develop an original phase-coupled method to realize multispectral metamaterial near-unity absorbers based on spatially separated graphene ribbon arrays with mid-infrared plasmonic resonances. The results both from the coupled-mode theory and finite-difference time-domain simulations reveal that in addition to the single-band absorption enabled by the bi-layer identical ribbon arrays, the outstanding dual-band perfect absorption is observed with the change in the phase between bi-layer ribbons only by varying the spacer thickness. The spectral positions of absorption peaks are tuned handily by small changes in ribbon widths and chemical potentials of graphene. Moreover, the triple-band absorber is achieved handily by the same principle and such absorbers are robust for nor-normal incident angles. The transfer matrix method is also utilized to uncover further the underlying physics of the phased-coupled-induced multispectral absorbers. Theoretical analysis are in excellent agreement with numerical calculations. The phase-coupled method thus provides new opportunities for obtaining multi-channel metamaterial perfect absorbers.

Abstract-Terahertz wavefront control by tunable metasurface made of graphene ribbons

Takumi Yatooshi¹, Atsushi Ishikawa^1,a) and Kenji Tsuruta¹
http://scitation.aip.org/content/aip/journal/apl/107/5/10.1063/1.4927824?TRACK=RSS
1 Department of Electrical and Electronic Engineering, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan
a) Electronic mail: a-ishikawa@okayama-u.ac.jp.
Appl. Phys. Lett. 107, 053105 (2015); http://dx.doi.org/10.1063/1.4927824

We propose a tunable metasurface consisting of an array of graphene ribbons on a silver mirror with a SiO2 gap layer to control reflected wavefront at terahertz frequencies. Thegraphene ribbons exhibit localized plasmon resonances depending on their Fermi levels to introduce abrupt phase shifts along the metasurface. With interference of the Fabry-Perotresonances in the SiO2 layer, phase shift through the system is largely accumulated, covering the 0-to-2π range for full control of the wavefront. Numerical simulations prove that wide-angle beam steering up to 53° with a high reflection efficiency of 60% is achieved at 5 THz within a switching time shorter than 0.6 ps.

Abstract-Probing terahertz surface plasmon waves in graphene structures

Oleg Mitrofanov^1,2, Wenlong Yu³, Robert J. Thompson¹, Yuxuan Jiang³, Igal Brener^2,4, Wei Pan⁴, Claire Berger^3,5, Walter A. de Heer³, and Zhigang Jiang³

¹Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
²Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
³School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
⁴Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
⁵CNRS/Institut Néel, BP166, 38042 Grenoble, France

Epitaxial graphene mesas and ribbons are investigated using terahertz (THz) near-field microscopy to probe surface plasmon excitation and THz transmission properties on the sub-wavelength scale. The THz near-field images show variation of graphene properties on a scale smaller than the wavelength, and excitation of THz surface waves occurring at graphene edges, similar to that observed at metallic edges. The Fresnel reflection at the substrate SiC/air interface is also found to be altered by the presence of graphene ribbon arrays, leading to either reduced or enhanced transmission of the THz wave depending on the wave polarization and the ribbon width.

© 2013 Author(s).All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License