Anomalous transversal motion of spheroidal microparticles driven by radiation pressure and torque

We numerically consider spheroidal dielectric micropaticles subject to radiation forces induced by a plane linearly polarized wave. Since the symmetry is lifted by the spheroidal shape of the particles the effects of both net radiation force and torque are taken into account. It is found that in the case of oblate spheroids there is a specific ratio of the semi-axes leading to anomalious dispersion of particles in the transversal plane perpendicular to the wave propagation direction. Such an effect results in a departure from the initial condition in the transversal plane by distances $\approx 10^{-2}~\mathrm{m}$ during a travel time $T=1000~\mathrm{s}$ while the particles are transported by mean distance $\langle z\rangle \approx 1.5~\mathrm{m}$ in the beam propagation direction.