Linear and Circular Dichroism in Graphene-Based Reflectors for Polarization Control

M. Amin, O. Siddiqui, and M. Farhat
Phys. Rev. Applied 13, 024046 – Published 19 February 2020

Abstract

We present an ultrathin graphene metascreen that possesses dispersive optical activity in the early terahertz spectrum. The metascreen design consists of periodically etched L-shaped voids on a graphene substrate backed by a conductive plane. The specific unit-cell design is based on chirality and leads to highly asymmetric radiations from the plasmon-polariton surface currents, leading to linear and circular dichroism. Hence the incident linearly or circularly polarized electric fields are effectively absorbed by the metasurface in different proportions. Consequently, the metasurface assumes half- and quarter-wave-plate behaviors in different parts of the reflected optical spectrum. In particular, we show via full-wave simulations that the dichroic metascreen supports perfect linear-to-circular polarization conversion (circular dichroism) in two adjacent terahertz frequency bands. In two other terahertz bands, it rotates the incoming linearly polarized wave vector by 90 (linear dichroism). Moreover, since graphene has a variable refractive-index dependence on its chemical potential, the dispersion characteristics can be shifted to neighboring frequencies within the early terahertz spectrum. We further demonstrate an angularly stable response for incident angles varying between 0 and 45. The tunable linear and circular dichroism characteristics are well suited for applications in sensing, imaging, and spectroscopy at terahertz frequencies.

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  • Received 18 October 2019
  • Revised 10 January 2020
  • Accepted 31 January 2020

DOI:https://doi.org/10.1103/PhysRevApplied.13.024046

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsAtomic, Molecular & Optical

Authors & Affiliations

M. Amin1,*, O. Siddiqui1, and M. Farhat2

  • 1College of Engineering, Taibah University, Madinah 41411, Saudi Arabia
  • 2Division of Computer, Electrical, and Mathematical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia

  • *masharif@taibahu.edu.sa

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Vol. 13, Iss. 2 — February 2020

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