Linear momentum increase and negative optical forces at dielectric interface

Abstract

Light carries momenta that can be transferred to objects. Relying on gradient forces created by structured light, one can trap and move microscopic particles. Aside from the conservative action of gradient forces, light always pushes an object along its direction of propagation. Here, we demonstrate that gradientless light fields can exert pulling forces on arbitrary objects in a purely passive dielectric environment and without resorting to non-paraxial illumination, interference of multiple beams, gain or other exotic materials. The forces acting against the flow of light arise naturally due to the appropriate amplification of the photon linear momentum when light is scattered from one dielectric medium into another with higher refractive index. This situation opens up a number of intriguing prospects for optical forces and their effects on surface-bound objects. Here, we demonstrate that this new mechanism can be used to manipulate objects over macroscopic distances along dielectric interfaces. © 2013 Macmillan Publishers Limited.