Behavior of an optical vortex immediately behind a spherical lens illuminated by circularly polarized light

In this paper we show that when focusing light with right circular polarization, an optical vortex with a topological charge equals to two is formed immediately behind a spherical lens for two transverse projections of the electric field and an optical vortex with a topological charge of unity for the longitudinal projection of the electric vector. This is proven by the fact that when illuminating a lens with an optical vortex with a topological charge of – 2 and right-hand circularly polarization, a ring-shaped intensity distribution is formed at the focus and a local intensity maximum occurs on the optical axis. This intensity maximum on the optical axis is the result of mutual compensation of the optical vortex with a topological charge of – 2 incident on the lens with the optical vortex with a topological charge of 2 formed after the spherical lens. Optical vortices with charges 2 and – 2 formed at the focus of light with linear polarization are responsible for the elliptical shape of the focal spot elongated along the direction of linear polarization.