Imaging ellipsometry for structured and plasmonic materials

For approximately a decade, imaging ellipsometers have been available commercially. These allow one to measure the properties of graphene flakes, organic layers on amorphous substrates, plasmonic structures, among many other examples. These imaging ellipsometers opened a path to recognize and interpret pattern formations on surfaces or mapping field enhancement. However, for a full understanding of the optical response of patterned substrates, one should be aware that the well-known Fresnel reflection and transmission equations are, strictly speaking, not correct anymore. In this contribution, the ellipsometric response is explained in detail using heuristic physical arguments, hopefully without getting lost in the complexities of numerical computations.