Experimental study of the longitudinal electric field component on the optical axis in the near field diffraction of high-aperture binary axicons at cylindrical polarization of the incident beam

We consider the diffraction of the laser radiation with a cylindrical polarization (radial and azimuthal) on high-aperture binary axicons with different structures. Theoretical analysis of the diffraction conducted based on the method of plane waves expansion and shown that depending on the polarization either longitudinal or transverse component of the electric field is focused on the optical axis. It is analytically and numerically shown that the introduction of asymmetry in the structure of the axicon corresponds to the introduction of the phase singularities in the incident beam and allows to control distribution of the various components of the electric field in the focal plane. Experimental measurements are conducted for light with radial and azimuthal polarization diffracted in the near-field of high-aperture binary axicons of three configurations - axisymmetric, biaxicon and spiral. The experimental results are qualitatively consistent with the theoretical results of both in the geometry and scale distributions.