Trapping dielectric Rayleigh particles with tightly focused pin-like vortex beam

Optical force exerted on the dielectric Rayleigh particles and tightly focused properties of circular polarized pin-like vortex beam are studied numerically in this paper. Firstly, we drive the expressions study the tightly focused properties of pin-like vortex beam. The numerical results show that the focal length keeps almost unchanged and the maximum intensity decreases with the increase of scaling factor. Then, the optical force exerted on the Rayleigh particle is studied based on the Rayleigh scattering model. The results show that smaller topological charges number and scaling factor of the pin-like vortex beams have greater longitudinal gradient force, transverse gradient force and trapping stiffness. Meanwhile, the trapping position in the beam propagation direction remains almost unchanged. The exponential parameter of the pin-like vortex beams has great influence on the propagation properties and tightly focused characteristics. Therefore, the stability of particle manipulation can be improved by changing the topological charges and scaling factor of the pin-like beams. These results have potential applications for optical trapping, optical storage and optical imaging.