Abstract-Terahertz spectroscopy of graphene complementary split ring resonators with gate tunability

Satoru Suzuki, Yoshiaki Sekine and Kazuhide Kumakura

http://iopscience.iop.org/article/10.7567/JJAP.56.095102/meta

Polarized transmission and reflection spectra in the terahertz region were obtained from a graphene complementary split ring resonator device. The complementary structure combined with an ion gel gate electrode rendered the optical properties of the device tuneable. The oscillator strength at the intraband plasmon resonance was largely enhanced with the gate-voltage-induced doping, and absorption exceeded 2.3%/layer of the interband transition. The resonance frequency could also be largely increased with the gate voltage. These results suggest the possibility of graphene-based metamaterials with tuneable permeability or permittivity and tuneable resonance frequencies.

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

Satoru Suzuki¹ and Hiroki Hibino¹

1 NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation, 3-1, Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
http://scitation.aip.org/content/aip/journal/jap/117/17/10.1063/1.4919703
J. Appl. Phys. 117, 174302 (2015); http://dx.doi.org/10.1063/1.4919703

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.