Surface plasmon polaritons () are electromagnetic waves, coupled to free electron oscillations, that propagate along the interface between a dielectric and a conductor with a negative real part of permittivity. The most attractive feature of surface plasmons is their enhanced and spatially confined electromagnetic fields at conductor-dielectric interfaces. Because of this, have been exploited in many applications such as chemo- and bio- sensors, integrated photonic circuits and enhancement of weak optical processes. However, practical applications of are hindered by their short propagation length, resulting from the power dissipation in the metal. Recently, considerable efforts have been devoted to increase the propagation length by introducing novel structures for waveguides or compensating the loss by using active mediums such as dyes, semiconductors, multiple quantum wells (MQWs), quantum dots, etc. In this thesis, a GaAs semiconductor layer is used as the gain medium which provides enough gain and is simple to fabricate. Studies carried on active plasmonic waveguides so far, have generally used simplistice models for the gain medium. Although these methods can be useful to obtain the general behavior of the active waveguide, they do not provide accurate results and can not account for some physical phenomena such as gain saturation due to increase in optical intensity. In this thesis a more comprehensive model, based on both rate and quantum mechanical gain equations, that covers the effects of frequency, temperature, field's intensity and bias value is used in order to analyze two proposed active semiconductor waveguides. One of these waveguides is a semiconductor/metal/dielectric structure and the other one is a metal/semiconductor/metal structure. Both waveguides are studied in an optical frequency range for different dimensions by applying several different values of electrical pumps. For wave amplification, saturation of the gain due to increase in the field intensity is theoretically analyzed and validated by simulations. It is also shown that when a sufficient proportion of the field is distributed within the GaAs layer, which ensures robust coupling between semiconductor gain medium and wave there is a profound impact on the propagation of the wave. In the latter part of this thesis, a double electrode waveguide incorporating a ferroelectric layer is proposed that can be used to control and increase the propagation length of the supported mode. For ferroelectric waveguide three cases based on the direction of Keywords: Surface plasmon polariton waveguide, active semiconductor medium, quantum mechanical gain equations, rate equations, ferroelectric.
