Chiral nanoparticle separation and discrimination using radially polarized circular Airy vortex beams with orbital-induced spin angular momentum

Abstract

We report orbit-induced localized spin angular momentum associated with optical spin–orbit interactions in tightly focused radially polarized circular Airy vortex beams and demonstrate their potential for separation and discrimination of chiral nanoparticles. We find that variations in spin angular momentum density endow these beams with positive and negative annular optical chirality density. Utilizing these extraordinary distributions, particles having different chirality parameters can be separated and discriminated by using two degrees of freedom, i.e., radial trapping position and azimuthal rotation. We also discuss the impacts of longitudinal optical force and topological charge on manipulating chiral particles. Additionally, we conduct a comparative analysis of the optical trapping of a non-chiral particle. Our work is expected to deepen the understanding of spin–orbit interactions and provide valuable insight into vortex beam interactions with chiral particles.