Three-dimensional structure of polarization singularities of a light field near a dielectric spherical nanoparticle.

We numerically study the structure of polarization singularity lines in a near-field of the sub-wavelength dielectric particle when it is irradiated by a monochromatic elliptically polarized plane wave. For the various values of the ellipticity degree of the incident radiation, we trace the CT and LT-lines on which the polarization ellipse turns into a circle or a line, respectively. The continuous variation of the isotropy parameters of the singularities is visualized along the lines. The main rules of CT and LT-lines deformation, emergence, and vanishing are revealed.