Over the past decade, the field of optical manipulation has been “shaped” by intelligent design of nonconventional optical beams. In particular, optical beams carrying angular momentum have provided a new twist to optical tweezers, enabling dynamical spin and rotation of trapped particles. Although optical vortex beams, nondiffracting Bessel beams, and recently, self-accelerating Airy beams have each played a unique role in the arena of particle trapping and manipulation, combining their features would certainly lead to a more powerful tool.
A few years ago, we designed and demonstrated diffraction-resisting Bessel-like beams that travel along arbitrary trajectories. With the similar method, the singular beam was shaped in this paper, which owns the form of a higher-order Bessel function with a preserving OAM and a nonexpanding dark “hole” in the main lobe of the beam. The beam can propagate along an arbitrary trajectory, including parabolic, hyperbolic and even three-dimensional (3D) spiraling trajectories. Experimentally, not only we observe such a curved singular beam, but also we employ it to optically trap and rotate microparticles in a 3D spiral motion under the combined action of radiation pressure, gradient force, and the OAM. Our findings may open up new avenues for shaped light in various applications.