Trapping of Rayleigh Spheroidal Particles Using Tightly Focused Higher-Order Vector Vortex Beams

Abstract

Considering the advantages of higher-order vector vortex beams (HOVVBs) with their diverse intensity distribution of the focal field and adjustable longitudinal field component, we investigated the optical forces and torques on Rayleigh spheroidal particles induced by tightly focused HOVVBs based on the Rayleigh scattering model and dipole approximation. It was found that the maximal optical forces were obtained when the major axis of the Rayleigh spheroidal particles was parallel to the x–y plane. We achieved the three-dimensional stable trapping of Rayleigh spheroidal particles at the focus by using an HOVVB. Further analysis showed that the optical torque caused the major axis of the spheroidal particle to rotate towards the x–y plane, which is conducive to the large-scale stable trapping of Rayleigh spheroidal particles in the two-dimensional plane. Moreover, the optical torque Γx could achieve a maximum of 0.869 pN·nm at φ0 = 90° and 270°, while Γy could achieve a maximum of 0.869 pN·nm at φ0 = 0° and 180° for the case of θ0 = 30°. Our findings provide a clear strategy for extending the degrees of freedom in the control of the beam. We envision a significant role for these results in optical micro-manipulation.