Optical forces generated by evanescent standing waves and their usage for sub-micron particle delivery

摘要

Recently a non-contact organization of sub-micron colloidal particles in the vicinity of liquid-solid interface attracted great attention in connection with the development of imaging techniques using total internal reflection. We focus here on the theoretical description of the optical forces acting on a sub-micron particle placed in an interference field created by two counter-propagating evanescent waves. We study the behavior of nanoparticles by means of Rayleigh approximation, and also the behaviour of sub-micron particles by Lorentz-Mie scattering theory. Numerical results show how these forces depend on the particle size and angle of incidence of both beams. The alternating dependence on the bead size was proven experimentally, and the sub-micron beads behavior was experimentally studied in the motional evanescent standing wave. Self-organization of the beads into linear chains was also observed.