Large optical anisotropy for terahertz light of stacked graphene ribbons with slight asymmetry

Abstract

The optical properties of stacked graphene microribbons in the terahertz region were simulated by the finite element method. The microribbons, which couple with terahertz light through the excitation of plasmons, were stacked with micrometer-scale vertical spacing (∼0.1λ or larger). Reflection and absorption spectra were found to strongly depend on the direction of incident light (forward or backward incidence), when the stacking structure was made slightly asymmetric by changing the ribbon width or the chemical potentials in each layer. At a certain frequency, light reflection is almost completely suppressed only for one incidence direction. The high directivity is considered to be due to the phasing effects of electromagnetic waves emitted from each layer like in a Yagi-Uda antenna.

Terahertz spectroscopy of graphene complementary split ring resonators with gate tunability

“…13) Anisotropy of the optical properties is especially very important in directional devices. 22,23)…”

Transmission, reflection, and absorption spectroscopy of graphene microribbons in the terahertz region

“…9,10) Moreover, the resonance frequency of graphene patterns can be tuned by the field effect. By utilizing the strong coupling and tunability, THz light detectors, 11,12) antennas, [13][14][15][16] and biosensors 17) could be realized.…”

“…On the other hand, reflection and absorption spectra can depend on the direction of incidence light when the sample is asymmetric. 16) In this work, we measured both transmission and reflection spectra in the THz region of graphene microribbons on a dielectric substrate. An absorption spectrum was also derived from the transmission and reflection spectra.…”