Abstract
A caustic vector vortex optical field is experimentally generated and demonstrated by a caustic-based approach. The desired caustic with arbitrary acceleration trajectories, as well as the structured states of polarization (SoP) and vortex orders located in different positions in the field cross-section, is generated by imposing the corresponding spatial phase function in a vector vortex optical field. Our study reveals that different spin and orbital angular momentum flux distributions (including opposite directions) in different positions in the cross-section of a caustic vector vortex optical field can be dynamically managed during propagation by intentionally choosing the initial polarization and vortex topological charges, as a result of the modulation of the caustic phase. We find that the SoP in the field cross-section rotates during propagation due to the existence of the vortex. The unique structured feature of the caustic vector vortex optical field opens the possibility of multi-manipulation of optical angular momentum fluxes and SoP, leading to more complex manipulation of the optical field scenarios. Thus this approach further expands the functionality of an optical system.
Highlights
The caustic vector vortex optical field is space-variantly modulated in both phase and SoP in the field cross-section, and it propagates with acceleration trajectories in free space
An appropriate radially dependent phase profile ψ(ρ) as a function of the polar radius of the initial optical field (which is included in A(ρ), i.e., A(ρ) = A0circ(ρ/r0)exp[-iψ(ρ)] in Eq (1) where A0 is a constant, circ(.) is the circular function, and r0 is the radius of the vector field, which is truncated by the spatial light modulator (SLM)) has been adopted to generate the desired caustic with arbitrary convex acceleration trajectories
Our results indicate that the distribution of SoP in the cross-section of a vector vortex optical field rotate during propagation in free space due to the existence of a vortex
Summary
Evolution of distribution of SoP, spin and orbital angular momentum flux density in a caustic vector vortex optical field. The experimental observations confirm the theoretical predictions for the corresponding intensity distributions of different polarization components in the vector vortex optical field at a propagation distance of z = 4 7 cm, as shown in Fig. 3(a),(b) for the case with n = 2 and m = 2, and n = 2 and m = 3. The results clearly indicate that the spatial distribution of SoP in the field cross-section can be dynamically manipulated during propagation by choosing the initial vortex and polarization topological charges, as well as the applied caustic phase. The intensity distribution of the polarization component in the x-direction of a vector vortex optical field with n = 20 and m = 1 is experimentally observed at different propagation distances using an x-linear polarization analyzer
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