Enhanced Nonlinearity Enabled Via Doped Enz Metastructures: Theory & Potential Applications
Synthetic composite structures, known as metamaterials, have been increasingly applied in the past two decades in numerous applications for obtaining electromagnetic characteristics far beyond those available in naturally occurring materials. In particular, epsilon-near-zero (ENZ) media are a special category of metamaterials which have been shown to exhibit exotic wave-matter interaction properties, rendering them suitable for various applications. It has been recently theoretically and experimentally demonstrated that a 2D ENZ body (i.e. infinitely extended along a given direction) doped with a dielectric inclusion is equivalent to a magnetic ENZ medium for an outside observer, a concept coined “photonic doping”. In this dissertation, I theoretically extend this concept for additional classes of inclusions and propose several potential applications harnessing the peculiar electromagnetic characteristics of such structures.
First, I theoretically demonstrate that a nonmagnetic linear ENZ host doped with a single Kerr dielectric inclusion is effectively perceived as an ENZ medium with enhanced magnetic nonlinearity. As an application of this concept, an ENZ slab doped with a Kerr dielectric rod is deployed for designing nonlinear absorbers where the absorption bandwidth may be tailored, in addition to dynamically shifting the absorption spectrum.
Subsequently, doping ENZ media by infinitesimally thin PEC inclusions is studied. Such “zero-area” PEC inclusions are theoretically shown to be capable of shaping the electric field distribution inside the ENZ medium while maintaining the magnetic field distribution intact, enhancing the nonlinearity of a Kerr nonlinear ENZ host, and designing soft surfaces with arbitrary geometry, which behave as a perfect magnetic conductor and perfect electric conductor for the TM and TE polarizations, respectively.
Furthermore, compact and tunable resonators formed by an air gap separating two doped ENZ slabs are shown to provide a mechanism for highly tunable radiation enhancement or suppression.
Finally, the transient response of ENZ media doped by dielectrics with time-varying permittivity is numerically studied to understand the time scale required for reaching steady-state field distributions and the various factors which affect the transient response time, such as the loss, size, geometry of the ENZ host, and the dielectric inclusion properties.