Optical Metamaterials Based on Optical Nanocircuits

Here we review the application of the optical nanocircuit paradigm to design and characterize metamaterials with exotic optical properties. The interaction of small nanoparticles with light is equivalently described in terms of optical lumped circuit elements, which relate the equivalent optical voltage across the particles and the optical displacement field current circulating through them. This equivalence goes beyond a simple description of the interaction of an individual nanoparticle with the impinging optical signal, as collections of closely spaced particles may be tailored as complex nanocircuit connections with specific optical response. Inspired by the fascinating concept and potentials of transmission-line metamaterials at microwaves, in which networks of lumped radio-frequency (RF) and microwave circuit elements may provide exotic metamaterial properties, in this paper, we review and discuss how analogous concepts may be translated to optical frequencies at the nanoscale, by applying the nanocircuit paradigm. We present several designs of 0-D, 1-D, 2-D, and 3-D arrays of nanoparticles supporting subwavelength resonances, negative-index propagation, and other exotic optical effects, achieved by suitably combining and connecting nanoparticles operating as optical lumped nanocircuit elements. Fascinating applications of these concepts are proposed in a variety of optical scenarios, considering the influence of natural material dispersion and loss in optical materials.