Optical tractor beam for a cluster of plasmonic and dielectric and chiral Mie objects

Abstract

A light beam pushes any object towards the direction of its propagation as light or quantum of light, photon, carries momentum. However, a light beam can also pull a particle backward towards the source — regarded as an optical tractor beam. Despite a series of phenomenal works being done in the field of optical manipulation using optical tractor beams, optical setup that can enable the optical pulling of all objects (i.e., dielectric, plasmonic and chiral) is still extremely rare. This work stands as the very first proposal of a simple and generic all-optical setup, where attaining optical tractor beam effect over all objects within a cluster is facilitated. Such optical pulling effect is observed only over a dielectric substrate (but not over plasmonic substrate) when two simple plane waves superimpose appropriately maintaining certain conditions. The emergence of such counterintuitive force has been explained based on distinct physical phenomena. For instance, in case of the dielectric and chiral nanoparticles, origin of the pulling force has been explained based on the field induced multipole radiation; whereas, in case of the plasmonic scatterer, the pulling has been explained based on the reversal of induced current density within the object.