Thirty years ago, Coullet et al. proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex. Since then, optical vortices have been widely studied, inspired by the hydrodynamics sharing similar mathematics. Akin to a fluid vortex with a central flow singularity, an optical vortex beam has a phase singularity with a certain topological charge, giving rise to a hollow intensity distribution. Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics. These amazing properties provide a new understanding of a wide range of optical and physical phenomena, including twisting photons, spin-orbital interactions, Bose-Einstein condensates, etc., while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible. Hitherto, owing to these salient properties and optical manipulation technologies, tunable vortex beams have engendered tremendous advanced applications such as optical tweezers, high-order quantum entanglement, and nonlinear optics. This article reviews the recent progress in tunable vortex technologies along with their advanced applications.

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Optical vortices 30 years on: OAM manipulation from topological charge to multiple singularities

We originally exploit the vortex beams with patterns of closed polygons [namely, polygonal vortex beams (PVBs)] generated by a quasi-frequency-degenerate (QFD) Yb:CALGO laser resonator with astigmatic transformation. The PVBs with peculiar patterns of triangular, square, and parallelogram shapes carrying large orbital angular momentums (OAMs) are theoretically investigated and experimentally obtained in the vicinity of the SU(2) degenerate states of laser resonator. The PVBs in QFD states are distinct from the vortex beams with patterns of isolated spots arrays located on the triangle-, square-, and parallelogram-shaped routes [namely, polygonal-spots-array vortex beams (PSA-VBs)] under normal SU(2) degenerate states. Beam profile shape of PVB or PSA-VB and OAM can be controlled by adjusting the cavity length and the position of pump spot. The simulated and experimental results validate the performance of our method to generate PVB, which is of great potential for developing applications such as particle trapping and manipulation.

Polygonal Vortex Beams

We introduce a class of spiraling anomalous vortex beam (AVB) arrays in strongly nonlocal nonlinear media. The general analytical formula for the arrays is derived, and its propagation properties are analyzed. It is shown that the spiraling AVB arrays can present three different propagation states (shrink, expansion, and the dynamical bound state) depending on the absolute value of the transverse velocity parameter ($0l|\ensuremath{\xi}|l1,\phantom{\rule{0.16em}{0ex}}|\ensuremath{\xi}|g1$, and $|\ensuremath{\xi}|=1$). Accordingly, we propose the concept of array breathers and array solitons. The topological charge of the vortex and the number of the constituent AVB also play important roles in the evolution of the AVB arrays. It is found that the light intensity of the central region of the array's field under an in-phase incident condition is not zero during propagation if and only if the ratio between the two parameters is an integer. By using the derived analytical expression, a series of numerical examples is exhibited to graphically illustrate these typical propagation properties. In addition, we give a variety of array forms of multibeam interaction. Our results may provide insight into vortex beam arrays and may be applied in optical communication and particle control.

Spiraling anomalous vortex beam arrays in strongly nonlocal nonlinear media

Research on spatially-structured light has seen an explosion in activity over the past decades, powered by technological advances for generating such light, and driven by questions of fundamental science as well as engineering applications. In this review we highlight work on the interaction of vector light fields with atoms, and matter in general. This vibrant research area explores the full potential of light, with clear benefits for classical as well as quantum applications.

Vectorial light-matter interaction -- exploring spatially structured complex light fields

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Optical vortex lattice: an exploitation of orbital angular momentum

We propose an approach for creating optical vortex array (OVA) arranged along arbitrary curvilinear path, based on the coaxial interference of two width-controllable component curves calculated by modified holographic beam shaping technique. The two component curve beams have different radial dimensions as well as phase gradients along each beam such that the number of phase singularity in the curvilinear arranged optical vortex array (CA-OVA) is freely tunable on demand. Hybrid CA-OVA that comprises of multiple OVA structures along different respective curves is also discussed and demonstrated. Furthermore, we study the conversion of CA-OVA into vector mode that comprises of polarization vortex array with varied polarization state distribution. Both simulation and experimental results prove the performance of the proposed method of generating a complex structured vortex array, which is of significance for potential applications including multiple trapping of micro-sized particles.

Xiangzheng Yuan

Papers

Generation of optical vortex array along arbitrary curvilinear arrangement.

Multi-plane unequal interval imaging based on polarization multiplexing