Natural materials and substances possess a rich variety of electromagnetic properties over the entire electromagnetic spectrum. Despite this diversity, nature does not equip us with a full set of possible material tools for controlling electromagnetic waves and realizing all physically possible effects. Only the use of artificial, engineered substances can give us full control over electromagnetic properties of materials. For instance, while spatial dispersion effects are weak in natural materials, they can be strongly pronounced in artificially engineered composite materials, metamaterials. Metamaterials consist of inclusions whose dimensions are small but comparable with the operating wavelength, which enables existence of strong spatial dispersion effects in them such as bi-anisotropy, magnet-less magnetism, and gyrotropy. This dissertation is devoted to the young and scantily explored field of spatially dispersive metasurfaces. Metasurfaces represent a two-dimensional arrangement of sub-wavelength inclusions engineered to manipulate in a prescribed fashion incident electromagnetic radiation. The first half of the dissertation contains a theoretical review of the research field essential for understanding of the obtained results outlined in the second half. Presentation of novel results can be broken down into three parts. The first part describes a semi-analytical technique for polarizability extraction of an arbitrary electrically small bi-anisotropic scatterer. Subsequently, the technique was exploited for the design of a novel scatterer with extremely pronounced spatial dispersion of the first order. The second part outlines the key ideas behind two designed spatially dispersive metasurfaces: A resonant gradient reflector and an absorber transparent outside the resonance band. It is demonstrated that such shadow-free operation of the metasurfaces requires spatial dispersion effects. The last part presents the exact synthesis of gradient metasurfaces for ideal wavefront control in reflection and transmission regimes. The fundamental importance of spatial dispersion in such metasurfaces is demonstrated. As a proof of concept, an optical metasurface for perfect anomalous reflection is designed and measured.
|Translated title of the contribution||Spatially dispersive metasurfaces|
|Publication status||Published - 2017|
|MoE publication type||G5 Doctoral dissertation (article)|
- spatial dispersion