  Electron transport in a graphene quantum well can be analogous to photon
transmission in an optical fiber. In this work, we present a detailed
theoretical analysis to study the transport characteristics of graphene
waveguides under the influence of different edge orientations. Non-equilibrium
Green's function approach in combination with tight-binding Hamiltonian has
been utilized to investigate the conductance properties of straight armchair
and zigzag oriented graphene waveguides. Conductance plateaus at integer steps
of $4e^2/h$ have been observed in both orientations while the zigzag oriented
waveguides present a wider first quantized plateau compared to that in the
armchair oriented ones. Using various geometric and physical parameters,
including side-barrier and waveguide width, and the metallic properties of
terminals, we investigate the conductance profile of waveguides. In addition to
the observation of valley-symmetry in both edge orientations, this article
explores the critical influence of drain contacts on waveguide conductance.
Furthermore, we extended our transport study to three different highly bent
waveguide configurations, such as U-shape, L-shape and split-shape waveguides,
in order to explore their applications in graphene-based ballistic integrated
circuit devices. In the end, we also calculated the conductance of larger
graphene waveguides using the scalable tight-binding model, in order to compare
the results obtained from the original model.
