Streamlines and topological transformation of modified vector Bessel-Gauss beams.

We characterize the streamline patterns of the transverse electric (TE) and transverse magnetic (TM) modes of the vector-modified Bessel-Gauss (BG) beam, which is the Fourier-transformed version of the ordinary BG beam. We derive analytical expressions to approximate the streamline patterns produced by the superposition of TM and TE modes. An analysis of the effect on the streamlines of the vector BG beams produced by some polarization devices, e.g., linear retarders and spiral polarizers, is presented. Additionally, we study the geometrical phase induced by linear retarders into the TM mode of the field. This work contributes to the description and understanding of the vector structure of the focal field of Bessel-Gauss beams.