On the feeding mechanisms for graphene-based THz plasmonic nano-antennas

Graphene, thanks to its ability to support Surface Plasmon Polariton (SPP) waves in the Terahertz (THz) band (0.1- 10 THz), enables the miniaturization and electrical tunability of miniature antennas suited for wireless communication among nanosystems. Despite graphene antennas have been extensively analyzed by means of modeling and simulation, no experimental proof is available to date. One of the main reasons for this is the lack of adequate signal generators and feeding mechanisms able to contact the nano-antenna with a reasonable efficiency. In this paper, two recently proposed feeding mechanisms for graphene-based THz plasmonic antennas are described. The first technique is based on the optical excitation of SPP waves by means of optical downconversion with photoconductive materials, whereas the second approach relies on electrical excitation of SPP waves on the antenna by means of a high-electron-mobility transistor. While fundamentally different, the two feeding mechanisms are able to effectively couple to a graphene-based plasmonic nanostructure and, thus, can be utilized to excite plasmonic nano-antennas in practical setups.