Gradient, scattering and other kinds of longitudinal optical forces exerted by off-axis Bessel beams in the Rayleigh regime in the framework of generalized Lorenz-Mie theory

After Arthur Ashkin's pioneering work in optical levitation and manipulation, the study of optical forces exerted by laser beams on particles has become an active field of research. The present paper is a contribution to this issue. The interest of Bessel beams is that their intensity does not have any longitudinal gradient along the direction of propagation leading to a trivial separation between gradient and scattering forces. Beside the classical gradient and scattering forces, we shall however exhibit a new kind of optical forces associated with the existence of non zero axicon angles. (C) 2020 Elsevier Ltd. All rights reserved.