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

Amin, M.; Siddiqui, O.; Farhat, Mohamed

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

Files

PhysRevApplied.13.024046.pdf (2.26 MB)

Type

Article

Authors

Amin, M.

Siddiqui, O.
Farhat, Mohamed

KAUST Department

Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division

Date

2020-02-19

Submitted Date

2019-10-18

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.

Citation

Amin, M., Siddiqui, O., & Farhat, M. (2020). Linear and Circular Dichroism in Graphene-Based Reflectors for Polarization Control. Physical Review Applied, 13(2). doi:10.1103/physrevapplied.13.024046