ANALYTICAL AND NUMERICAL MODELING OF DEVICE TECHNOLOGIES FOR NANOSCALE COMMUNICATIONS IN THE TERAHERTZ AND OPTICAL BANDS
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design and manufacture novel nanoscale devices, which are able to perform simpletasks, such as computing, data storing, sensing and actuation. The integrationof several of these nano-devices into a single entity will enable the developmentof advanced nanomachines. By means of communication, nanomachines will beable to organize themselves in networks, or nanonetworks, and complete morecomplex tasks in a distributed fashion, such as wireless nanosensor networks foradvanced health monitoring and drug delivery systems, wireless networks on chipfor massive multi-core computing architectures and, ultimately, the Internet ofNano-Things. However, traditional communication technologies and techniquescannot simply be reused to enable the communication between nanomachines, dueto the capabilities of nano-devices and the physics of the wireless channel. Inthis context, the objective of this thesis is to establish the theoretical foundationsof high frequency electromagnetic (THz) and optical wireless communicationsat the nanoscale. Imposed by the size constraints of nanomachines, first, aunified mathematical framework is developed to investigate the performancein transmission and reception of metallic nano-dipole antennas at infrared andvisible optical frequencies. Starting from the study of the propagation propertiesof surface plasmon polariton (SPP) waves on the metallic nano-dipoles, a newantenna theory for nano-structures is derived. Motivated by these results, theuse of wireless optical communication for on-chip networks is proposed. To assessthe feasibility of this paradigm, new frequency and time domain channel modelsthat capture the propagation of optical wireless signals on chip are developed, bycombining tools from ray tracing and communication theory. In order to increasethe communication distance, there is a need to reduce the system frequency, whilestill keeping the size of the nano-antennas small. For this, the use of the THz-bandis motivated. In order to close the THz gap, a new on-chip plasmonic THz sourcebased on a high-electron-mobility transistor (HEMT) with asymmetric boundaryconditions is proposed and analytically and numerically modeled. A new multiphysicssimulation platform that self-consistently solves the Hydrodynamic Modelequations and the Maxwell?s equations is developed and used to study the impactof different design elements on the radiated fields.