Longitudinal manipulation of local nonseparability in vector beams.

The inherent nonseparability of vector beams presents a unique opportunity to explore novel optical functionalities, expanding new degrees of freedom for optical information processing. In this Letter, we introduce a novel, to the best of our knowledge, method for tailoring the local nonseparability along the propagation axis of vector beams. Employing higher-order Bessel vector beams, the longitudinal control over the local nonseparability is achieved through targeted amplitude modulation of constituent orthogonal polarization components within the main ring region. Experimental demonstrations of diverse longitudinal nonseparability profiles corroborate the efficacy and versatility of our approach, opening avenues for further exploration of the nonseparability manipulation in vector beams.

Spatio-temporal structuring control of a vectorial focal field.

Focal field modulation has attracted a lot of interest due to its potential in many applications such as optical tweezers or laser processing, and it has recently been facilitated by spatial light modulators (SLMs) owing to their dynamic modulation abilities. However, capabilities for manipulating focal fields are limited by the space-bandwidth product of SLMs. This difficulty can be alleviated by taking advantage of the high-speed modulation ability of digital micromirror devices (DMDs), i.e., trading time for space to achieve fine focus shaping. In this paper, we propose a new, to the best of our knowledge, technique for achieving four-dimensional focal field modulation, which allows for independent manipulation of the focal field's parameters (including amplitude, phase, and polarization) in both the space and time domains. This technique combines a DMD and a vector field synthesis system based on a 4-f system. The high-speed modulation ability of DMDs enables versatile focus patterns to be fast switchable during the exposure time of the detector, forming multiple patterns in a single recording frame. By generating different kinds of focal spots and lines at different moments during the exposure time of the detector, we can finally get complete multifocal spots and lines. Our proposed method is effective at improving the flexibility and speed of the focal field modulation, which is beneficial to applications.

Twin curvilinear vortex beams.

We report on a novel curvilinear optical vortex beam named twin curvilinear vortex beams (TCVBs) with intensity and phase distribution along a pair of two- or three-dimensional curves, both of which share the same shape and the same topological charge. The TCVBs also possess the character of perfect optical vortex, namely having a size independent of topological charge. We theoretically demonstrate that a TCVB rather than a single-curve vortex beam can be created by the Fourier transform of a cylindrically polarized beam. The behavior of TCVBs generated through our method is investigated by simulation and experiment, including interference experiments for identifying the vortex property of the TCVBs. The TCVBs may find applications in optical tweezers, such as trapping low refractive index particles in the dark region between two curves and driving them moving along the curvilinear trajectory.

Non-diffracting and self-accelerating Bessel beams with on-demand tailored intensity profiles along arbitrary trajectories.

Owing to their robustness against diffraction, Bessel beams (BBs) offer special advantages in various applications. To enhance their applicability, we present a method to generate self-accelerating zeroth-order BBs along predefined trajectories with tunable z direction intensity profiles. The character of tunable z direction intensity profiles in non-diffracting self-accelerating BBs potentially can attract interest in the regimes of particle manipulation, microfabrication, and free-space optical interconnects.

Radially self-accelerating Stokes vortices in nondiffracting Bessel-Poincaré beams.

We theoretically propose and experimentally generate the nondiffracting Bessel-Poincaré beams whose Stokes vortices radially accelerate during propagation. To this end, we design the Bessel beams whose intensity is specified to be uniformly distributed along the longitudinal direction. By superposing two such Bessel beams having different helical phases and mutually orthogonal polarizations, the synthesized vector beam is endowed with the polarization singularity that can rotate about the optical axis, while the total intensities maintain their profiles. Radially self-accelerating Stokes vortices in the resulting beam can be manipulated by adjusting the predefined parameters in the constituent beams.