Chiral Plasmonic Core-Shell Nanohelices

Abstract

Chirality is a geometrical property of objects with a mirror image that cannot be superimposed on itself. Chiral three-dimensional structures have recently received interest due to possible applications in nanophotonic technologies. For instance, chiral plasmonic planar metamaterials, have shown to significantly improve biosensing [1]. For possible applications in the visible wavelength regime, it is necessary that chiral plasmonic structures have nanoscale geometries. Recently, researchers showed a successful technique to fabricate nanometer sized metallic helices using electron beam induced deposition [2]. In this work, we fabricate core-shell (fused silica-gold) nanohelices using this technique and study the influence of geometrical parameters on optical activity. Here, optical activity is defined as \((T_{LCP} - T_{RCP})/(T_{LCP} + T_{RCP})\) with T LCP (T RCP ) representing the transmission of left- (right-) handed circularly polarized light. A trend is observed when performing transmission measurements: short helices show a less strong optical response compared to tall helices. Preliminary simulations (FDTD) are used to describe the effect of gold shell thickness.