Single Gradientless Light Beam Drags Particles as Tractor Beams

TLDR

Light beams normally exert a pushing force on particles. The study investigates whether nonparaxial gradientless beams can pull particles toward the light source. The pulling force is achieved by tuning the strong nonparaxiality of a Bessel beam to generate stable tractor‑beam trajectories. The authors show that nonparaxial gradientless Bessel beams can pull particles toward the source, creating stable tractor‑beam trajectories. © 2011 American Physical Society.

Abstract

Usually a light beam pushes a particle when the photons act upon it. We investigate the optical forces by nonparaxial gradientless beams and find that the forces can drag suitable particles all the way towards the light source. The major criterion of realizing the backward dragging force is the strong nonparaxiality of the light beam, which contributes to the pulling force owing to momentum conservation. The nonparaxiality of the Bessel beam can be manipulated to possess a dragging force along both the radial longitudinal directions, i.e., a "tractor beam" with stable trajectories is achieved. © 2011 American Physical Society.