Interest in the field of plasmonics has been primarily driven by the need to guide and confine light in the subwavelength scale. The past few years has witnessed a huge interest in this field largely due to the may advances that have occured in nanofabrication techniques. The field of plasmonics is often touted as the next generation platform that could interface nanoscale electronics and Si photonics. With current electronic systems nearing saturation, the migration to photonic systems would become inevitable. Crucial to achieving this integration is to design reliable plasmonic components within nanophotonics circuits. This however requires an accurate estimation of the electromagnetic response of these components. Numerical modeling tools are one way to gauge this response. By and large the thesis deals with numerically analysing the propagation and near field characteristics of plasmon based components for Si photonics. The two principal EM modelling tools used in this regard are the boundary element method as well as the finite difference time domain.Two main kind of active plasmonic active devices were investigated: integrated modulators, and free space radiation photodetectors. The critical issue of an efficient coupling of light into a very confined guided plasmonic mode was first investigated so as to isolate the main modal governing contributions. Next, a new structure of plasmon assisted modulator was proposed and a complete optical design taking into the technological constraints of a CMOS foundry is provided and discussed. Finally a design optimizing the radiative coupling to the absorption of a Ge dot, using a plasmonic dipolar antenna, is studied. In particular the radiative engineering of the supporting SOI substrate is shown to have a tremendous
