Scattering engineering at the extreme: Physical bounds, anomalies and singularities in passive and active metamaterial structures

This paper presents our recent theoretical advances in extreme scattering engineering using metamaterials and nanostructures. Here, and in our conference talk, we will first briefly discuss the fundamental limitations (or lack thereof) on the possibility of reducing or enhancing the electromagnetic scattering cross section of a material body, as well as other bounds stemming from passivity, causality and reciprocity. We will then present our recent work on extreme scattering effects, anomalies and singularities in passive and active open systems, including embedded eigenstates, exceptional points, optical vortices, etc. We will also discuss the relation of these effects with emerging concepts of topological physics. These singularities enable intriguing electromagnetic phenomena, such as light trapping, unidirectional invisibility, slow light, enhanced emission/absorption, which may have important practical implications for nanophotonic devices and systems.