Effects of classical nonlocality on the optical response of three-dimensional plasmonic nanodimers

We examine the optical scattering from a variety of axially symmetric plasmonic nanoparticle dimers separated by nanoscale gaps, quantifying the role of classical nonlocality on their optical properties. Due to the rotational symmetry of the analyzed structures, a high degree of accuracy is achieved using a computational approach termed 2.5D modeling, in which a small number of simulations on a two-dimensional domain can replace a memory-and time-intensive simulation on a three-dimensional domain. We find that scattered light from dimers consisting of nanoparticles with flat surfaces, such as nanodisks, exhibits pronounced spectral shifts due to the nonlocality of the electron fluid; these significant shifts persist even at relatively large (>1 nm) gap dimensions, where quantum tunneling effects are believed to be negligible. The 2.5D modeling technique accurately incorporates all responses due to any nonaxially symmetric eigenmodes of the system, such as dipolar and quadrupolar modes, thereby providing a complete characterization of the system for any excitation. (C) 2013 Optical Society of America