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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 47539 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Khavasi, Amin; Rejaei, Behzad
- Abstract:
- An important and interesting aspect of graphene plasmons (GPs) is their tunability via gating or chemical doping. This property can be used for controlling the propagation of GPs by using spatially non-uniform conductivity profiles in a single flake of graphene. Conductivity patterns are made by locally adjusting the chemical potential of graphene. The chemical potential in turn can be locally tuned by means of chemical doping or gate voltage. Therefore, it is important to know how GPs propagate on a graphene layer with patterned conductivity. In this thesis we will investigate this problem. First, we consider the scattering problem of GPs normally incident on an arbitrary conductivity profile in a finite region between two semi-infinite graphene sheets with different constant conductivities. Starting with an integro-differential equation governing the current density on graphene, we find an integral equation for transmission and reflection coefficients within the quasi-static approximation. The final integral equation is derived for a variable that has a local nature i.e. it is nonzero only around the region where the conductivity profile is nonuniform. Therefore, the integral equation can be solved in a finite region that is of great importance from a computational point of view. The results from above integral equation has been verified with full-wave simulation. A simple circuit model has been presented for this scattering problem which can be used to design and analyse structures based on one-dimensional conductivity patterns such as graphene-based filters. In the next chapter, the oblique incidence of GPs on an arbitrary conductivity profile in a finite region between two semi-infinite graphene sheets with different constant conductivities has been investigated both via method of moment solution of an integral equation and full wave simulation. It has been shown that reflection has a minima for a specific angle of incidence. The result from previous chapter could be used to obtain dispersion relation of non-edge modes in graphene ribbon waveguides. calculating the phase of reflection of GPs for differnent angles of incidence to the edge of an infinte graphene waveguide and we find this dispersion relation and compare it to the full-wave simiulation results
- Keywords:
- Scattering ; Graphene ; Plasmonic Waveguides ; Terahertz Band ; Oblique Impact ; Graphene-Based Waveguides ; Normal Incidence ; Ribbon Waveguides
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