Focus shaping of circularly polarized Bessel–Gaussian vortex beam with binary axicon for nanoparticle trapping

Based on the vector Debye approximation theory, focusing on circularly polarized Bessel–Gaussian vortex (CPBGV) beam by a binary axicon has been investigated. Different focal segments are generated in the focal region of the binary axicon by adjusting beam and axicon parameters. Optical cages can be formed in the focal region with on-axis longitudinal intensity when the topological charge m = −1 with the left–hand CPBGV beam. Tighter focal segments can be achieved in the focal region of the binary axicon by introducing a central obstruction, decreasing the numerical aperture of the axicon, or increasing the numerical aperture of the optical system. These findings indicate that the focused CPBGV beam, when modulated with a binary axicon, shows great promise for applications in nanoparticle trapping.