Lateral forces on circularly polarizable particles near a surface

Abstract

Optical forces allow manipulation of small particles and control of nanophotonic structures with light beams. While some techniques rely on structured light to move particles using field intensity gradients, acting locally, other optical forces can push particles on a wide area of illumination but only in the direction of light propagation. Here we show that spin orbit coupling, when the spin of the incident circularly polarized light is converted into lateral electromagnetic momentum, leads to a lateral optical force acting on particles placed above a substrate, associated with a recoil mechanical force. This counterintuitive force acts in a direction in which the illumination has neither a field gradient nor propagation. The force direction is switchable with the polarization of uniform, plane wave illumination, and its magnitude is comparable to other optical forces. ; This work has been supported, in part, by EPSRC (UK). A.V.Z. acknowledges support from the Royal Society and the Wolfson Foundation. N.E. acknowledges partial support from the US Office of Naval Research Multidisciplinary University Research Initiative Grant No. N00014-10-1-0942. A.M. acknowledges support from the Spanish Government (contract Nos TEC2011-28664-C02-02 and TEC2014-51902-C2-1-R). ; Rodríguez Fortuño, FJ.; Engheta, N.; Martínez Abietar, AJ.; Zayats, AV. (2015). Lateral forces on circularly polarizable particles near a surface. Nature Communications. 6(8799):1-7. https://doi.org/10.1038/ncomms9799 ; S ; 1 ; 7 ; 6 ; 8799 ; Novotny, L. & Hecht, B. Principles of Nano-Optics Cambridge University Press (2011). ; Jackson, J. D. Classical Electrodynamics Wiley (1998). ; Ashkin, A. & Dziedzic, J. M. Optical levitation by radiation pressure. Appl. Phys. Lett. 19, 283 (1971). ; Ashkin, A. Acceleration and trapping of particles by radiation pressure. Phys. Rev. Lett. 24, 156–159 (1970). ; Omori, R., Kobayashi, T. & Suzuki, A. Observation of a single-beam gradient-force optical trap for dielectric particles in air. Opt. Lett. 22, ...