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The optical vortex beams are specially-structured light fields with helical wavefronts expressed as exp (imϕ), where m represents the topological charge with ϕ defined as the azimuthal angle. Further, the concepts of vector vortex beams are naturally developed with their polarization states varying across the fields. Simultaneously, richer application scenarios are expected from vortex beams due to their phase singularities and additional degrees of freedom in the angular momentum and/or polarization states. This article reviews the major advances in laser material processing with vector vortex beams since the beginning of this century. Typical fabricating schemes for additive, subtractive manufactures and material modifications are summarized. In section 2, the advances in the subtractive and material modifications are categorized into three sub-sections as: microstructure imprinted on the surface, microstructures inscribed inside the material and the applications in the optical storage. As numerous techniques to generate these novel beams were available in 2000s, vector vortex beams were soon applied to imprint laser-induced periodic surface structure (LIPSS) patterns due to the well-known relations of LIPSS with local polarization states of laser beams. In subsection 2.1, we survey the works on LIPSS induced by vector vortex beams on the surfaces of glass, silicon and metals, i.e. three common materials of dielectric, semiconductor and conductor. Commercially available ultrafast Ti:Sapphire lasers delivering femtosecond pulses are mostly employed in these activities due to the possibility to induce multiscale micro/nanostructures. Besides, several works to induce vortex-related microstructures are also included. In subsection 2.2, advances in hole drilling with either expected or unexpected concomitant results by Bessel beams are reviewed. Since applying the novel vector vortex beams in the optical storage is a related cutting-edge topic but still in development, simulations and conception advances in this topic are surveyed in subsection 2.3. Section 3 is devoted to the related works on additive fabrications. The concept and recent advances in optical caustics of vortex beams are briefly introduced in subsection 3.1. Compared with the 3D point-by-point scanning scheme, further applications based on flexibly shaped vortex beams reviewed in subsection 3.2 are presented to significantly accelerate the fabricating speed by more than two orders of magnitudes. Miscellaneous works with other vector beams are introduced in section 4. Finally, we discuss the limitations of the current advances and we envision that the applications of vector vortex beams will be further developed through richer collaborations of professionals in various fields.
Vector vortex beams generation with vortex retarders (VR)[5]. (a) Setup; (b) Vector vortex beams of different orders
Machining results on glass with tightly focused vortex beams. (a) Annular rings ablated by linearly polarized beams[16]; Polarization-sensitive structures produced on fused silica galss with (b) mixed and (c) radially- or azimuthally-polarized beams[17]
LIPSS imprinted on Silicon wafer with different vector vortex beams of various polarization state[21]. (a) Radial; (b) Azimuthal; (c) Spiral; (d) Linear. Insets (b1) and (b2) show the zoom-in LSFLs in the peripheral regions and the grooves in the internal region marked in (b)
Twisted nanoneedles on (a) Tantalum sheet[34] and (b) nanocones on Silicon surface[35]
Machining results with ultrafast Bessel beams. (a) Nanochannels in glass[38]; (b) Waveguiding tubes fabricated by Bessel vortex beams[42] ;(c) Vector Bessel vortex beams;[43] (d) Nanorods by vector Bessel vortex beams[44]
(a) Schematics of 3D structurally polarized Bessel beams generation and twisted nanograting inscribing; (b) The SEM of inscribed microstructures[48]
Twisted magnetization structures induced by vector Gaussian vortex beams [55]. (a) Schematic of magnetization generation at subdiffraction-limited scale; (b) Simulation of the light-induced twisted 3D magnetizations
Caustics of Bessel vortex beams in different theories. (a) Any hyperboloid formed by the rays emitting from a circle in the initial plane; (b) Ideal nondiffracting tubular caustics as deduced in Berry’s work[60] (red dashed line); (c) Expanding tubular caustics (blue lines) in reference [61]
Globally analytical caustics of axially symmetric vortex beams[63]. (a) Vortex beams; (b) Bessel vortex beams; (c) Vortex beams generated from parabolic vortex toroidal lens
Comparison of different light fields with and without vortices [63]. (a) and (b) Bessel-like beams; (c) Abruptly autofocusing vortex beams. Column 1 and 2 represent, respectively, the intensity profiles along propagation in simulations and in the experiments; Column 3 illustrates the differences between the global caustics of the abruptly autofocusing vortex beams with and without the OAM
Vortex beams designed by solving the inverse problem[63]. (a) Quartic; (b) Logarithmic; (c) Parabolic; (d) Exponential tubular profiles
Polymer microtubes fabricated with different vortex beam-based schemes. (a) Uniform tube size enabled by scanning the focused vortex beams[67]; (b) Controllable tube profiles by dynamic hologram-assisted axial scan of the focused vortex beams[69]; (c) Cylindrical micro-tubes fabricated by Bessel vortex beams[70]; (d) Bowl-shaped microstructures fabricated by abruptly autofocusing vortex beams with tailored parabolic caustics highlighted by the yellow rays[71]
Schematics of the setup to generate arbitrary vector beams with a single liquid crystal spatial light modulator[72]
(a) Patterns fabricated on LiNbO3 with vector beam arrays [75]; (b) Dynamically trajectory assisted fabrications of periodic nested microstructures; (c) Polygonal and spiral fan-leaf-like structures [76]; (d) Chinese character “Nan” and irregular quadrilateral grid structures [77]
Multi-scaled micro/nano-structures fabricated on SiC surface with specially designed vector beams[78]. (a) Radial-hybrid vector beams; (b) Spiral-hybrid vector beams