Characterization of a metafilm/metasurface

A metafilm (also referred to as a metasurface) is the surface equivalent of a metamaterial. More precisely, a metafilm is a surface distribution of suitably chosen electrically small scatterers. Metafilms are becoming popular as an alternative to full three-dimensional metamaterials. Unfortunately, many papers in the literature present incorrect interpretations and mischaracterizations of these metafilms. In this paper, we discuss an appropriate interpretation and characterization of metafilms and present a correct way to characterize a metafilm. We also present a retrieval approach for determining the uniquely defined quantities (the electric and magnetic polarizability densities of its constituent scatterers) that characterize a metafilm.