Analytically decomposing optical force on a spherical particle in Bessel beams into conservative and non-conservative parts

Abstract

Based on the recently developed Cartesian multipole expansion theory, we analytically analyze the conservative and non-conservative nature of the optical force acting on a spherical particle of arbitrary size and isotropic composition immersed in the optical Bessel beams of arbitrary orders and polarizations. It is rigorously proved that the conservative force on the particle in Bessel beams aligns in the radial direction transverse to beam propagation, while the non-conservative force is completely non-radial, lying in the azimuthal and longitudinal directions. To the best of our knowledge, our work provides the first analytical partition between the conservative and non-conservative components of the optical force on a particle of arbitrary size and composition placed in a class of extensively employed optical beams in practical optical manipulation, beyond the small particle limit.