| In recent years, there have been substantial efforts to design and fabricate millimeter-wave and terahertz (THz) active and passive devices. Operation of microwave and photonic devices in THz range is limited due to limited maximum allowable electron velocity at semiconductor materials, and large dimensions of optical structures that prohibit their integration into nano-size packages, respectively. In order to address these issues, the application of surface plasmons (SPs) is mostly suggested to advance plasmonic devices and make this area comparable to photonics or electronics.;In this research, the feasibility of implementing THz and millimeter-wave plasmonic devices inside different material platforms including: two-dimensional electron gas (2DEG) layers of hetero-structures, silicon wafers and graphene, are elaborated. To this end, an analytical model is developed to describe the propagation of two-dimensional plasmons along electron gas layers of biased hetero-structures. Using this analytical model, the existence of new plasmonic modes along the biased electron gas is reported for the first time. For an independent verification, a novel multi-physics simulator is developed to analyze active terahertz plasmonic structures. It is also anticipated that the solver can offer novel ideas for guiding the SPs inside the future plasmonic circuits.;In a different approach to design plasmonic devices in a widely used material platform, silicon, a THz modulator is proposed. Using a full wave simulator, it is shown that plasmonic wave can propagate along an indented n-type doped silicon wafer (which is later covered with a metallic layer) with large attenuations. However, the signal losses can be prohibited by applying bias voltages onto the metal as the thickness of the depletion layer between the metal and silicon increases.;At the end, an effective method to couple incident waves onto an infinitely thin graphene mono-layer is presented. As will be illustrated, the surface waves along a corrugated metal can efficiently transit into graphene and successfully launch plasmons. |
