Plasmonic Waveguides and Antennas

The field of plasmonics has received great attention during the past years. Plasmonic devices are characterized by their small electrical size which enabled researchers to overcome the challenge of the size mismatch between the bulky photonic devices and the small electronic circuits. Plasmonic metals are characterized by their lossy dielectric nature which is different from the highly conductive classical metals. Consequently, the design of plasmonic devices necessitates upgrading the existing solvers to incorporate their material properties at the optical frequency range. In this thesis, a plasmonic transmission line mode solver is developed in which the propagation characteristics of plasmonic waveguides are calculated. Specifically, the solver calculates the propagation constant, losses, and mode profile(s) of the propagating mode(s). The transmission lines can have any topology and are assumed to be placed within a stack of flat layers. The solver is developed using the Method of Moments technique which is characterized by its tremendously decreased number of unknowns compared to the finite element/difference methods leading to much faster calculation time. The solver is tested on several plasmonic transmission lines of various topologies, number of metallic strips and/or surrounding media. These transmission lines include rectangular strip, circular strip, triangular strip, U-shaped strip, horizontally coupled strips, and vertically coupled strips. The obtained results are compared with those calculated by the commercial tool “CST”. Very good agreement between both solvers is achieved. The solver is also used to study the effect of varying the geometrical parameters of various plasmonic transmission lines on their propagation characteristics. The second line presented within this thesis is concerned with the design of plasmonic wire-grid nano-antenna arrays. The basic element of this array is a nano-rod, whose propagation characteristics are first obtained using the developed solver. The arrays are then optimized using “CST”. Within this thesis, three nano-antenna arrays are proposed: a five-element wire-grid array, an eleven-element wire-grid array, and a circularly polarized wire-grid array. The first and second arrays provide linearly polarized radiation. The third design presents a novel circularly polarized wire-grid array. All the presented antennas are characterized by their high directivity which increases by increasing the number of radiators. The proposed arrays are designed to operate at 193.55 THz making them suitable for inter-/intra-chip optical communication in which they replace the lossy transmission lines. The thesis also presents two prototypes of fabricated wire-grid arrays designed for operation at 400 THz. The transmission from the periodic arrays are measured and compared with simulations. In general a good agreement between simulations and measurements is obtained with some differences for the resonance locations and amplitudes which can be due to the dimensions of the fabricated antenna which is different from the designed ones.