Drift of non-spherical optical particles driven by counter-propagating beams in a viscous medium

https://doi.org/10.1016/j.photonics.2025.101489

We consider spheroidal dielectric microparticles subject to radiation forces and torques induced by two linearly polarized weakly-focused counter-propagating Gaussian beams. 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 anomalous drift of particles both in the lateral and the longitudinal direction. Such an effect results in displacement from the initial condition by distance up to 70μm.