Engineering the spectral response of nanodipole antennas loaded with plasmonic core-shell particles via efficient numerical modeling techniques

An efficient computational framework is presented for the spectral response engineering of nanodipole antennas loaded with plasmonic core-shell particles. It is demonstrated that plasmonic coreshell particles can function as tunable nanoloads that allow the customization of the nanodipole's optical response in a fully controlled manner. The proposed loading scheme is based on the observation that if we insert a spherical particle in the gap defined by the arms of the nanodipole, then the loaded gap can be treated as an equivalent load characterized by an effective permittivity similar to that generated by a mixing procedure. As a consequence, when this particle load exhibits Drude dielectric properties the gap is characterized by an effective Lorentzian response. The characteristics of this Lorentzian function are what determine the optical response of the loaded nanodipole. Furthermore, it is demonstrated that the employment of plasmonic core-shell particle loads, due to the fact that their electromagnetic properties are a function of the shell and the core material as well as their volume fraction, provide greater flexibility for the engineering of the aforementioned Lorentzian, and thus allow for a wider variety of tuning options for the nanoantenna.