Layered plasmonic cloaks to tailor the optical scattering at the nanoscale

We discuss the rich scattering features offered by thin and thick plasmonic layers covering dielectric nanoparticles and their potential optical applications. The frequency position of scattering dips and peaks may be controlled to a large degree using plasmonic layers, which may dramatically vary the total scattering signature in the frequency range of interest. We show that complex and exotic spectra may be obtained using a single composite nanosphere, including dipole-dipole Fano resonances and electromagnetic induced transparency effects. The described phenomena are observable at any angle of observation, in the total scattering cross section and for realistic plasmonic materials, since they are based on purely dipolar fields. Enhanced field amplitudes are associated with these anomalous scattering features, which may be used to efficiently boost weak optical nonlinear effects. Exciting applications of these nanostructures are envisioned, such as efficient and tunable sensors, all-optical switches and memories, optical tagging and biomolecular imaging.