Probing the chiral nature of electromagnetic fields surrounding plasmonic nanostructures

Abstract

We investigate the chiral properties of near fields around plasmonic nanostructures and their relation to the electromagnetic chirality $C$. By combining chiral metal nanoparticles with achiral dye molecules and measuring the circular polarization dependence of the enhanced photoluminescence, we find a correlation between the dissymmetry of the luminescence enhancement and the calculated values of $C$. These effects are strong ($\ensuremath{\sim}$${10}^{\ensuremath{-}1}$), despite the weak circular dichroism of the particles ($\ensuremath{\sim}$${10}^{\ensuremath{-}5}$). We further show that $C$ represents the chiral selectivity of the near-field coupling between an emitter and a nanoantenna.