OPTICAL PULLING FORCES IN “NANOPARTICLES DIMER IN THE STRUCTURED FIELD” SYSTEM

Abstract

The subject area of this research is optical pulling forces as one of the manifestations of light mechanical action on material objects. In particular, we investigated optical forces acting on a dimer composed of nanoparticles with a small radius as compared to wavelength. The calculation of Lorentz optical forces was carried out by solving self-consistent system of equations, which made it possible to calculate electromagnetic fields in every point of the structure. We worked out analytic formula, representing the dependence of optical force on the parameters of dimer system and structured radiation made up of two crossing plane waves. For the first time we showed that dimer consisting of two equal dipolar particles can experience an optical pulling force (“negative radiation pressure”) in the field of two crossing plane waves. It is shown that the increase of photons momentum (the projection of photons momentum on the direction of structured light propagation) after scattering is responsible for this negative radiation pressure. The corresponding scattering diagram showed the increase of forward scattering, that is the conformation of the considered mechanism of pulling forces origination. Our findings would be very useful for increasing capabilities of optical manipulation of nano- and micro-particles.

Keywords

• optical manipulation
• optical forces
• pulling forces
• nanoparticle
• dimer