Geometric effects on far-field coupling between multipoles of nanoparticles in square arrays

Metallic nanoparticles organized in regular arrays exhibit an extraordinary spectral feature that arises from electromagnetic coupling between localized surface plasmons and constructive interference from diffracted far-field radiation. A rapid semianalytical description of coupling between dipoles and scattering modes is applied to examine the influence of nanoparticle size, dielectric, and interparticle separation on the occurrence, resonant wavelength, and intensity of the extraordinary spectral feature. Introducing a dynamic polarizability that includes higher-order electric poles into the description accurately characterizes plasmon resonances of larger particles. Previously unrecognized patterns and periodic variations in the extraordinary feature were observed to result from modulations in polarizability, as well as from interference of scattered modes that were distinguishable for the first time using the rapid semianalytic solution. Streamlined rational design of metamaterials with optimum optical properties using the rapid semianalytic coupled dipole approximation is considered. (C) 2011 Optical Society of America