Polarization Singularities in Non-Coaxial Interference of Vector Beams

The paper investigates the formation of polarization singularities arising from the non-axial interference of vector optical modes of different symmetry. An analytical model of superposition of two spatially shifted beams with arbitrary topological charges and phase parameters is proposed. It is shown that in the region of their overlap polarization features of the V- and C-points type as well as stable configurations of the lemon and star types can arise. On the basis of the Stokes parameters, the features are classified and the conditions of their formation are determined. An analytical relation determining the optimal value of beam displacement for the appearance of a symmetric singularity is proposed. The results are confirmed by numerical modelling and experiment.