Broadband, angle-dependent optical characterization of asymmetric self-assembled nanohole arrays in silver

Abstract

Plasmonic nanostructured materials made of nanohole arrays in metal are signi cant plasmonic devices exhibiting resonances and strong electromagnetic con nement in the visible and near-infrared range. As such, they have been proposed for use in many applications such as biosensing and communications. In this work, we introduce the asymmetry in nanoholes, and investigate its in uence on the electromagnetic response by means of broadband experimental characterization and numerical simulations. As a lowcost fabrication process, we use nanosphere lithography, combined with tilted silver evaporation, to obtain a 2D hexagonal array of asymmetric nanoholes in Ag. Our experimental set-up is based on a laser, widely tunable in the near-infrared range, with precise polarization control in the input and in the output.We next resolve the circular polarization degree of the transmitted light when the nanohole array is excited with linear polarization. We attribute the disbalance of left and right transmitted light to the asymmetry of the nanohole, which we support by numerical simulations. We believe that the optimization of such simple plasmonic geometry could lead to multifunctional at-optic devices.