Composite polarization vortices using Bessel phase engineering

This paper explores an innovative approach in Bessel beam phase engineering to produce polarization vortices. Higher-order Bessel beams have both circulating and radial phase gradients. Radial phase discontinuity exists in different sections on the cross-section of the Bessel beam. This discontinuity gives rise to the circular diffraction pattern of the Bessel beam. Typically, different sections of the beam exhibit phase gradients that circulate in the same direction. By engineering this circulation, phase singularities can be formed. In this article, composite polarization vortices are generated by tuning the circulation in the alternate direction. A common-path polarization interferometer is used to generate a polarization vortex, surrounded by a ring of generic C-points. Polarization vortices make a chain of the same index polarity around the centre in contrast to the index rule followed by polarization vortex lattices generated by multi-beam interference. Phase-shifting techniques can be used to control the location and separatrix orientation of the composite vortices. The presence of composite polarization vortices in the field distribution is detected using Stokes fields