Perturbation induced morphological transformations invector-field singularities

In this paper, we report the morphological transformations of vector-field singularities (V-points) under symmetric and asymmetric perturbation using a diamond-shaped diffracting aperture. The number of null intensity points in the diffraction pattern depicts the magnitude of the polarization singularity index. Also, under symmetric perturbation, a higher-order V-point singularity disintegrates into |η| number of unit-index singularities following the index conservation rule. Asymmetric perturbations, realized by laterally shifting the aperture, lead to the formation of pairs of generic elliptic-field singularities (C-points) that are more fundamental and stable. In this process, the helicity and polarization singularity index are both conserved. This may find application in the context of singularimetry, where weak fields are measured by considering them as perturbations of unstable optical beams [Phys. Rev. Lett.109, 183903 (2012)PRLTAO0031-900710.1103/PhysRevLett.105.053904].