Circular Polarization near the Tight Focus of Linearly Polarized Light

We have considered the tight focusing of light with linear polarization. Using the Richards–Wolf formalism, it is shown that before and after the focal plane, there are regions in which the polarization is circular (elliptical). When passing through the focal plane, the direction of rotation of the polarization vector is reversed. If before the focus in a certain area there was a left circular polarization, then directly in the focus in this area there will be a linear polarization, and after the focus in a similar area there will be a right circular polarization. This effect allows linearly polarized light to be used to rotate dielectric microparticles with little absorption around their center of mass