PLASMONIC CLOAKING: SCATTERING CANCELLATION WITHOUT ISOLATION

We review here some of the salient features of the plasmonic cloaking technique, which uses the anomalous properties of plasmonic metamaterial layers to suppress and cancel the scattering from a dielectric or conducting object. In particular, we focus our attention on penetrable obstacles, for which the peculiar properties of this technique ensure that the cloaked regions are not necessarily isolated from the surrounding. This may enable to exploit one of the most intriguing applications of plasmonic cloaking: the possibility to sense the surrounding from within the cloak, lowering a receiving system's scattering and near-field disturbance, without necessarily affecting its capability to measure and "sense" the external world. In other words, the plasmonic cloak may allow external fields to penetrate into the cover, but it may at the same time ensure the suppression of most of the reaction and scattered fields from the sensor. This may allow "sensing" the external world, or receive an external signal, from inside the cloak in a variety of schemes of interest for near-field sensing and imaging. We review here the main applications of this technique to several scenarios of interest, and some of their connections with anomalous scattering mechanisms and cloaking scenarios.