Complex vector light fields have become a topic of late due to their exotic features, such as their non-homogeneous transverse polarisation distributions and the non-separable coupling between their spatial and polarisation degrees of freedom. In general, vector beams propagate in free space along straight lines, being the Airy-vector vortex beams the only known exception. Here, we introduce a new family of vector beams that exhibit properties that have not been observed before, such as their ability to freely accelerate along parabolic trajectories. We anticipate that these novel vector beams might find applications in fields such as optical manipulation, microscopy, laser material processing, among others.
It is well known that entanglement is invariant to local unitary transformations, this implies the degree of entanglement or non-separability remains constant during free-space propagation, which is true for both quantum and classically-entangled modes. Here we demonstrate an exception to this rule using a carefully engineered vectorial light field, and study its non-separability dynamics upon free-space propagation. We show that the local non-separability between the spatial and polarisation degrees of freedom dramatically decays to zero, while preserving the purity of the state and hence the global non-separability. We show this by numerical simulations and corroborate it experimentally. Our results evince novel properties of classically-entangled modes, point to the need for new measures of non-separability for such vectorial fields, while paving the way to novel applications for customised structured light.
Laser remote sensing represents a powerful tool that enables the accurate measurement of the speed of moving targets. Crucially, most sensing techniques are 2-Dimensional in nature and do not enable direct determination of the full velocity vector of objects moving in 3D. A disadvantage that is very often compensated with two-dimensional techniques that in many cases are hard to implement and in others, require complicated postprocessing analysis. Here we demonstrate a novel technique that enables the direct and simultaneous measurement of both velocity components using a single interrogating beam. This technique is based on the use of complex light beams, whose polarization and spatial degree of freedom are coupled in a non-separable way. We present experimental results of a proof-of-principle experiment by applying our technique to the specific case of helical motion, of great relevance in a wide of research areas.
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