Effect of orientation on plasmonic coupling between gold nanorods.

Radiative coupling of induced plasmonic fields in metal nanoparticles has drawn increasing attention in the recent literature due to a combination of improved experimental methods to study such phenomena and numerous potential applications, such as plasmonic nanoparticle rulers and plasmonic circuitry. Many groups, including ours, have used a near-exponential fit to express the size scaling of plasmonic coupling. First, we show experimental agreement between previously simulated nanorod coupling and plasmonic coupling in electron beam lithography (EBL) fabricated nanorods using the near-exponential expression. Next, we study the effect of nanoparticle orientation on plasmonic coupling using EBL and DDA simulations. We develop a mathematical relationship that is consistent with our findings and quantitatively describes plasmonic coupling between nanorods as a function of orientation, separation, induced dipole strength, and the dielectric constant of the medium. For applications utilizing plasmonic coupling to become viable with particle shapes that do not have spherical symmetry, such as nanoprisms and nanorods, comparison of the experimental and theoretical results of how particle orientation affects plasmonic coupling is essential.