Optical forces from evanescent Bessel beams, multiple reflections and Kerker conditions in magnetodielectric spheres and cylinders

TL;DR

This paper investigates optical forces exerted by evanescent Bessel beams on magnetodielectric particles near surfaces, revealing interference effects, trapping conditions, and Kerker conditions for cylinders, with implications for optical manipulation.

Contribution

It provides analytical solutions for optical forces on magnetodielectric particles near surfaces and extends Kerker conditions to cylinders, highlighting interference and scattering effects.

Findings

Vertical force can push particles away from the surface due to interference.

Wavelength determines the trapping capability of the evanescent beam.

Kerker conditions for cylinders are similar to spheres and relate to force minima.

Abstract

In this work we address, first, the optical force on a magnetodielectric particle on a flat dielectric surface due to an evanescent Bessel beam and, second, the effects on the force of multiple scattering with the substrate. For the first question we find analytical solutions showing that due to the interference of the excited electric and magnetic particle dipoles, the vertical force unusually pushes the object out from the plane. The incident wavelength rules whether the illumination constitutes, or not, an optical trap. As for the second problem, we make a 2D study with a single evanescent plane wave, and we present the Kerker conditions, (so far established for spheres), for magnetodielectric cylinders; showing that in $p$-polarization those are practically reproduced and are associated to minima of the horizontal and vertical forces.