SEMICONDUCTOR-BASED HYBRID PLASMONICS
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As the typical size of electronic devices approaches the nanometer range, the size mismatch between such devices and optical components—which are typically in the micrometer range—poses a challenge for the two technologies integration on the same chip. For conventional dielectric waveguides, the mode cannot be confined to sizes smaller than half the wavelength due to the diffraction limitation. One possible and promising technological development to resolve this issue is the so-called surface plasmon polaritons (SPPs). Given the growing importance of optical plasmonics in semiconductors for a wide variety of applications; it is essential to devise a modal which is directly interpretable in physical terms. In the optical regime metals have a complex permittivity, which means that SPPs suffer from large propagation loss. To mitigate this loss, semiconductors can be used instead of metal, but their application is limited in the far-infrared regime because the permittivity has a negative real part. Semiconductors are therefore promising materials for developing efficient terahertz (THz) waveguides. The frequency of a THz wave occupies the electromagnetic spectra between microwave and infrared ranges and acts as a bridge. As a result THz semiconductor-based hybrid plasmonics has become one of the most promising applications in the plasmonics field. This thesis presents a theoretical study and develops the physics and mathematics of SPPs in semiconductors at optical frequencies, taking into account the different properties of these semiconductors. It also investigates the modal properties of a hybrid plasmonic waveguide operating at a THz regime in different types of structures. The analytical results are compared to conventional hybrid waveguides previously reported. Numerical solutions are also obtained for proposed novel hybrid terahertz plasmonic waveguide structures. Moreover, a theoretically study of the optical properties of a superconductorinsulator- superconductor waveguide both at THz and telecommunication frequencies were performed. These novel studies provide insight into the fundamental nature of optical plasmon semiconductors. A primary focus of the thesis is geometries which exhibit the capability of supporting SPPs.