Influence of spherical aberration on the tightly focusing characteristics of vector vortex beams.

For a tightly focusing imaging system, the aberration of the lens will result in a distorted focusing spot and undermine the system performance. In this paper, the expression of the tightly focused light field of Laguerre-Gaussian vector vortex beam (LGVVB) is deduced. Then the intensity distribution, focal shift and spot size that influenced by spherical aberration are calculated in detail. Since the vector vortex beams have multiple degrees of freedom to control the form of the intensity distribution on the focal plane, the effects of aberration on the focal spot are analyzed when some key parameters are changed. The results show the Pancharatnam topological charge is the most influential parameter to change the light distribution on the focal plane. According to the change rule, a scheme is proposed to minimize the effect of aberration by jointly adjusting the parameters of the LGVVB.