Hybrid topological evolution of multi-singularity vortex beams: generalized nature for helical-Ince-Gaussian and Hermite-Laguerre-Gaussian modes.

A generalized family of scalar structured Gaussian modes including helical-Ince-Gaussian (HIG) and Hermite-Laguerre-Gaussian (HLG) beams is presented with physical insight upon the hybrid topological evolution nature of multi-singularity vortex beams carrying orbital angular momentum. Considering the physical origins of intrinsic coordinates aberration and the Gouy phase shift, a closed-form expression is derived to characterize the general modes in astigmatic optical systems. Moreover, a graphical representation, singularities hybrid evolution nature (SHEN) sphere, is proposed to visualize the topological evolution of the multi-singularity beams, accommodating HLG, HIG, and other typical subfamilies as characteristic curves on the sphere surface. The salient properties of SHEN sphere for describing the precise singularities splitting phenomena, exotic structured light fields, and Gouy phase shift are illustrated with adequate experimental verifications.