Focusing properties of cylindrical vector vortex beams with high numerical aperture objective

Focused by a high numerical-aperture objective in free space, the cylindrical vector beam phase-encoded by vortex phase plate with higher topological charge was capable to generate the doughnut-shaped spot in the vicinity of the focal region. The width of the dark focal spot was manipulated by the phase plate with different topological charge. The relationship between the properties of the focal spot and the vortex phase plate was explicitly analyzed for the input beam with different cylindrical vector polarization. Furthermore, the experimental verification was undertaken at the incidence beam λ = 635 nm with the radial and azimuthal polarization. The experimental results are in excellent agreement with the theoretical calculation.