Equilibrium orientations of oblate spheroidal particles in single tightly focused Gaussian beams

Based on a hybrid discrete dipole approximation (DDA) and T-matrix method, a powerful dynamic simulation model is used to find plausible equilibrium orientation landscapes of micro- and nano-spheroids of varying size and aspect ratio. Orientation landscapes of spheroids are described in both linearly and circularly polarized Gaussian beams. It's demonstrated that the equilibrium orientations of the prolate and oblate spheroids have different performances. Effect of beam polarization on orientation landscapes is revealed as well as new orientation of oblate spheroids. The torque efficiencies of spheroids at equilibrium are also studied as functions of tilt angle, from which the orientations of the spheroids can be affirmed. This investigation elucidates a solid background in both the function and properties of micro-and nano-spheroidal particles trapped in optical tweezers.