Optical cloaking of cylindrical objects by using covers made of core-shell nanoparticles

In this Letter, we propose an engineered design of optical cloaks based on the scattering cancellation technique and intended to reduce the observability of cylindrical objects. The cover, consisting of a periodic arrangement of core-shell nanospheres, is designed in such a way to exhibit near-zero values of the real part of the homogenized effective permittivity at optical frequencies. Full-wave numerical simulations, considering the measured data of the dielectric function of the plasmonic material composing the shell, show that the cloak is able to reduce by about 6 dB the scattering cross section of a finite-length cylinder at around 740 THz with a -3 dB fractional bandwidth of about 7%. We show also that this result is not significantly affected by the perturbation of the periodic alignment of the core-shell nanospheres, due to possible fabrication issues or to an amorphous arrangement.