To the theory of spherical particles localization in the field of zeroth order Bessel beam: the Rayleigh-Gans approximation

Abstract

Summary form only given. The dielectric particles in electromagnetic field are affected by force of light pressure, which are usually divided into gradient forces and scattering forces. Micromanipulation of particles and their spatial separation are possible, using of these forces (spatial separation require the localization of particle and then its transportation to another spatial region). It is more optimally to use the Bessel beams for the spatial separation of particles. The Bessel beams are characterized by smaller divergence then the Gaussian ones with equal power and width. Their application may increase the distance of transportation more than an order. In this paper the amplitude of gradient force acting on a transparent spherical particle in the field of the zeroth order Bessel beam is calculated. The obtained expression for gradient force amplitude, takes into account heterogeneity of acting radiation in the volume of particle. Optimal conditions (parameters of particle, liquid, and Bessel beam) for localization and transportation of a particle are determined using the solution of kinetic-equation. It was shown, that for some definite relationships between the particle size and the width of Bessel beam the localization region is shifted from the central maximum of the beam. It is cause by the equilibrium the gradient forces from the central maximum and from first interference ring of the Bessel beam. The qualitative comparison of the obtained results with known experimental data is performed.