ABSTRACT
In this paper, the topological characteristics of two non-axial, parallel Gaussian vortex beams, with the same and opposite topological charges, are discussed based on the Huygens–Fresnel principle and Debye approximation. Topological behaviors in both conservation and non-conservation of topological charge and index are analyzed in the focal plane of the composite field. The distribution of newly generated phase singularities is found to be quite different for the vortices of same charge and opposite charge. Comparison and analysis for both cases are also given in this paper.
