Transformation Optics Using Graphene: One-Atom-Thick Optical Devices Based on Graphene

Metamaterials and transformation optics have received considerable attention in the recent years, as they have found an immense role in many areas of optical science and engineering by offering schemes to control electromagnetic fields. Another area of science that has been under the spotlight for the last few years relates to exploration of graphene, which is formed of carbon atoms densely packed into a honey-comb lattice. This material exhibits unconventional electronic and optical properties, intriguing many research groups across the world including us. But our interest is mostly in studying interaction of electromagnetic waves with graphene and applications that might follow. Our group as well as few others pioneered investigating prospect of graphene for plasmonic devices and in particular plasmonic metamaterial structures and transformation optical devices. In this thesis, relying on theoretical models and numerical simulations, we show that by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a flake of graphene, one can have this material as a one-atom-thick platform for infrared metamaterials and transformation optical devices. Varying the graphene chemical potential by using static electric field allows for tuning the graphene conductivity in the terahertz and infrared frequencies. Such design flexibility can be exploited to create patches with differing conductivities within a single flake of graphene. Numerous photonic functions and metamaterial concepts are expected to follow from such platform. This work presents several numerical examples demonstrating these functions. Our findings show that it is possible to design one-atom-thick variant of several optical elements analogous to those in classic optics. Here we theoretically study one-atom-thick metamaterials, one-atom-thick waveguide elements, cavities, mirrors, lenses, Fourier optics and finally a few case studies illustrating transformation optics on a single sheet of graphene in mid-infrared wavelengths

Antenna Design Concepts Based on Transformation Electromagnetics Approach

Using the idea of wave manipulation via coordinate transformation, we demonstrate the design of novel antenna concepts. The manipulation is enabled by composite metamaterials that realize the space coordinate transformation. We present the design, realization and characterization of three types of antennas: a directive, a steered beam and a quasi-isotropic one. Numerical simulations together with experimental measurements are performed in order to validate the concept. Near-field cartography and far-field pattern measurements performed on a fabricated prototype agree qualitatively with Finite Element Method (FEM) simulations. It is shown that a particular radiation can be transformed at ease into a desired one by modifying the electromagnetic properties of the space around it. This idea can find various applications in novel antenna design techniques for aeronautical, telecommunication and transport domains

\u3cem\u3ePTM\u3c/em\u3e Metamaterials via Complex-Coordinate Transformation Optics

We extend the transformation-optics paradigm to a complex spatial coordinate domain, in order to deal with electromagnetic metamaterials characterized by balanced loss and gain, giving special emphasis to parity-time (PT) symmetric metamaterials. We apply this general theory to complex-source-point radiation and anisotropic transmission resonances, illustrating the capability and potentials of our approach in terms of systematic design, analytical modeling, and physical insights into complex-coordinate wave objects and resonant states