Analysis and design of terahertz antennas based on plasmonic resonant graphene sheets

Resonant graphene antennas used as true interfaces between terahertz (THz) space waves and a source/detector are presented. It is shown that in addition to the high miniaturization related to the plasmonic nature of the resonance, graphene-based THz antenna favorably compare with typical metal implementations in terms of return loss and radiation efficiency. Graphene antennas will contribute to the development of miniature, efficient, and potentially transparent all-graphene THz transceivers for emerging communication and sensing application. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768840

Reconfigurable terahertz plasmonic antenna concept using a graphene stack

The concept and analysis of a terahertz (THz) frequency-reconfigurable antenna using graphene are presented. The antenna exploits dipole-like plasmonic resonances that can be frequency-tuned on large range via the electric field effect in a graphene stack. In addition to efficient dynamic control, the proposed approach allows high miniaturization and good direct matching with continuous wave THz sources. A qualitative model is used to explain the excellent impedance stability under reconfiguration. These initial results are very promising for future all-graphene THz transceivers and sensors. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767338

Contributions to the modeling and design of reconfigurable reflecting cells embedding discrete control elements

This paper presents new contributions to the modeling and design of reflecting cells embedding discrete control elements such as microelectromechanical system (MEMS) or diodes. First, a rigorous assessment of the different possibilities to simulate and measure the reconfigurable cell in a periodic environment is proposed. Strategies to efficiently model a cell comprising discrete control elements are then presented and discussed in terms of versatility, required assumptions, and computational effort. The most efficient method allows computing all reconfigurable states cell parameters, including information such as the total and dissipated power in each MEMS or diode, in a few minutes using a commercial full-wave solver and adequate post-processing. Finally, the benefit of such an efficient modeling is illustrated by the optimization of an element phase states distribution using a particle swarm optimizer. The concepts presented are also directly applicable to reconfigurable transmitting cells

Self-biased reconfigurable graphene stacks for terahertz plasmonics

The gate-controllable complex conductivity of graphene offers unprecedented opportunities for reconfigurable plasmonics at terahertz and mid-infrared frequencies. However, the requirement of a gating electrode close to graphene and the single 'control knob' that this approach offers limits the practical implementation and performance of these devices. Here 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 allows independent control of the complex conductivity of each layer within the stack and provides enhanced control on the stack equivalent complex conductivity. These results are very promising for the development of THz and mid-infrared plasmonic devices with enhanced performance and reconfiguration capabilities.Peer ReviewedPostprint (published version

Unit cells for dual-polarized and polarization-flexible reflectarrays with scanning capabilities

We present the analysis and design of reflecting cells capable of dynamically and independently control the reflection phase of each component of a dual-polarized impinging wave. Such capability is of significant interest for the future implementation of dual-polarized and polarization-flexible reflectarrays with scanning capabilities. The presented cells are controlled by varactor diodes and operate in lower X-band (8 GHz). Simulated and measurement results demonstrate good performances in terms of phase range, losses and bandwidth. For example, a range of 300deg is achieved under normal incidence at 8 GHz with maximum and average reflection loss of 3.3 dB and 1.4 dB, respectively