Empowering structured light to enhance chirality detection and characterization at nanoscale

摘要

We demonstrate that the detection of material chirality is possible by employing a large variety of electromagneticfield structures rather than using the standard method based on two plane waves with oppositecircular polarization. We illustrate that any set of two fields with equal electric and magnetic energydensities and non-zero difference between their helicity densities lie within the proposed category. Thissuggests a one-to-one relation between maximizing the helicity density of fields and maximizing theprobability of chirality detection of nanoparticles. Recently, with the goal of maximizing detection sensitivityand enabling chirality characterization of nanoparticles an upper bound for helicity density of genericelectromagnetic fields has been proposed [1]. Here, we show that nearfields of a spherical Si nanoantennaunder illumination of a Gaussian Beam with circular polarization offers fields reaching the proposedupper bound of the helicity density.