Abstract-Active substrate integrated terahertz waveguide using periodic graphene stack

Yanfei Dong^1,a), Peiguo Liu¹, Dingwang Yu¹, Bo Yi¹ and Gaosheng Li¹
 HIDE AFFILIATIONS
1 State Key Laboratory of Complex Electromagnetic Environmental Effects on Electronics & Information System, National University of Defense Technology, Changsha 410073, China
a) Author to whom correspondence should be addressed. Electronic mail:dongyanfeicool@126.com
AIP Advances 5, 117237 (2015); http://dx.doi.org/10.1063/1.4936651

http://scitation.aip.org/content/aip/journal/adva/5/11/10.1063/1.4936651?TRACK=RSS
The transmission properties of a substrate integrated waveguide (SIW) based on periodicgraphene stacks have been theoretically investigated in the terahertz (THz) region. The effects of the dielectric-graphene-dielectric structure of the stack on the propagation properties are shown to be significant and different from the conventional active SIW based on active components. By varying the graphenechemical potential, the cut-off frequency of the proposed waveguide can be dynamically tuned from 3 to 3.7 THz. Moreover, the tunable waveguide displays low leakage loss and single-mode propagation with −120 dB stop-band attenuation.These primary results are very promising for THz integration devices and SIW-based systems.

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.

Abstract-Self-biased Reconfigurable Graphene Stacks for Terahertz Plasmonics

J. S.Gomez-Diaz, C. Moldovan, S. Capdevilla, J. Romeu, L. S. Bernard, A. Magrez, A. M. Ionescu, J. Perruisseau-Carrier

(Submitted on 13 May 2014)

http://arxiv.org/abs/1405.3320

The gate-controllable complex conductivity of graphene offers unprecedented opportunities for reconfigurable plasmonics at THz and mid-IR frequencies. However, the requirement of a gating electrode close to graphene and the single `control knob' that this approach offers for graphene conductivity limits the practical implementation and performance of graphene-controllable plasmonic devices. Herein, we report on graphene stacks composed of two or more graphene monolayers separated by electrically thin dielectrics and present a simple and rigorous theoretical framework for their characterization. In a first implementation, two graphene layers gate each other, thereby behaving as a controllable single equivalent layer but without any additional gating structure. Second, we show that adding an additional gate --a third graphene layer or an external gate-- allows independent control of the complex conductivity of each layer within the stack and hence provides enhanced control on the stack equivalent complex conductivity. The proposed concepts are first theoretically studied and then demonstrated experimentally via a detailed procedure allowing extraction of the parameters of each layer independently and for arbitrary pre-doping. These results are believed to be instrumental to the development of THz and mid-IR plasmonic devices with enhanced performance and reconfiguration capabilities.