Achievement of pure transverse spin angular momentum at the focal plane by tightly focused generalized hybrid...

The transverse spin angular momentum (SAM) observed in evanescent waves, interference fields, and tightly focused vector beams is directly related to both academic research and technical applications. In this work, we theoretically propose and experimentally generate the generalized hybrid polarized vector beam (GHPVB), which superimposes the orthogonal electric field vector components of the two cylindrical vector beams with topological charges m₁ and m₂, with an initial phase difference of ψ between them. First, we investigate the longitudinal SAM separation in weakly focused GHPVBs. It is shown that the superposition effect of the initial phase difference ψ and the Gouy phase difference Δϕ during the focusing process of GHPVBs determines their polarization state transition and SAM evolution. Secondly, we study the three-dimensional SAM distribution in tightly focused GHPVBs. It is found that, unlike the incident field and weakly focused field which can only have longitudinal SAM, under the condition of i^m₁ = i^m₂e^iψ, tightly focused GHPVBs exhibit the pure transverse SAM distribution at the focal plane. The presented work enriches the generation approaches of pure transverse SAM and deepens the understanding and manipulation of the angular momentum properties of light fields. This pure transverse SAM has broad application prospects in regimes such as optical micromanipulation, spin-dependent directional coupling, quantum information processing, and integrated spin-selective devices.