Dynamic of Si nanoparticles inside of a quadrupolar trap: Analysis of the angular momentum transfer

Abstract

We investigate the dynamics of Si spherical nanoparticles for different infrared wavelengths in a system based on two circularly polarized counter-propagating Gaussian beams. Through the analysis of the dipolar and quadrupolar forces, we obtain several conditions under which these nanoparticles describe different types of attractive or repulsive spirals at focus plane depending on the efficiency of the quadrupole trap obtained. We demonstrate that these spirals are generated by the angular momentum transfer from the electromagnetic field to the particles, and this is mainly due to the interference forces dipole–dipole and quadrupole–dipole. Through the adequate selection of the wavelength, angular momentum transfer can only take place with quadrupolar– dipolar interference forces. We study particle dynamics by solving the deterministic and non-deterministic over-damped Langevin equation.