Tight focusing of vortex beams in presence of primary astigmatism.

The tight focusing of vortex carrying beams is studied using the Debye-Wolf diffraction integral in the presence of primary astigmatism. The roles of topological charge, polarization distribution of the input beam, and handedness of the beam polarization are investigated in the intensity distribution of the focal plane of a high-numerical-aperture lens. The effect of tight focusing in the presence of astigmatism on the dark core of the azimuthally polarized beam is also investigated and compared with the dark core of a circularly polarized vortex beam. The effect of an aberration has been discussed in the context of the fluorescent spot size in the focal plane of a stimulated emission depletion microscope for two different polarization setups.