Three-dimensional chiral microstructures fabricated by structured optical vortices in isotropic material

Optical vortices,a type of structured beam with helical phase wavefronts and‘doughnut’-shaped intensity distributions,have been used to fabricate chiral structures in metals and spiral patterns in anisotropic polarization-dependent azobenzene polymers.However,in isotropic polymers,the fabricated microstructures are typically confined to non-chiral cylindrical geometry due to the two-dimensional‘doughnut’-shaped intensity profile of the optical vortices.Here we develop a powerful strategy to realize chiral microstructures in isotropic material by coaxial interference of a vortex beam and a plane wave,which produces threedimensional(3D)spiral optical fields.These coaxial interference beams are generated by designing contrivable holograms consisting of an azimuthal phase and an equiphase loaded on a liquid-crystal spatial light modulator.In isotropic polymers,3D chiral microstructures are achieved under illumination using coaxial interference femtosecond laser beams with their chirality controlled by the topological charge.Our further investigation reveals that the spiral lobes and chirality are caused by interfering patterns and helical phase wavefronts,respectively.This technique is simple,stable and easy to perform,and it offers broad applications in optical tweezers,optical communications and fast metamaterial fabrication.

Electromagnetic chirality:from fundamentals to nontraditional chiroptical phenomena

Chirality arises universally across many different fields.Recent advancements in artificial nanomaterials have demonstrated chiroptical responses that far exceed those found in natural materials.Chiroptical phenomena are complicated processes that involve transitions between states with opposite parities,and solid interpretations of these observations are yet to be clearly provided.In this review,we present a comprehensive overview of the theoretical aspects of chirality in light,nanostructures,and nanosystems and their chiroptical interactions.Descriptions of observed chiroptical phenomena based on these fundamentals are intensively discussed.We start with the strong intrinsic and extrinsic chirality in plasmonic nanoparticle systems,followed by enantioselective sensing and optical manipulation,and then conclude with orbital angular momentum-dependent responses.This review will be helpful for understanding the mechanisms behind chiroptical phenomena based on underlying chiral properties and useful for interpreting chiroptical systems for further studies.

Dynamic Airy imaging through high_efficiency broadband phase microelements by femtosecond laser direct writing

Manipulating Airy beams to symmetric Airy beams(SABs)with abruptly autofocusing and self accelerating properties has attracted much attention.With such a particular propagation dynamic,SABs may provide great potential in dynamic signal imaging.On the other hand,the generation of SABs by spatial light modulators suffers from the limitations of phase gradient accuracy,low optical efficiency(<40%),and a bulky footprint.Therefore,exploring imaging applications and optimal generation methods of these Airy-type beams deserves further research.Here,based on the coordinate transformation of SAB,an asymmetric Airy beam(AAB)is realized.Symmetric/asymmetric cubic phase microplates(SCPPs/ACPPs)are designed and fabricated for generating SAB/AAB.The SCPP/ACPP demonstrates superior performance:compact construction(60μm × 60μm × 1.1μm),continuous variation of phase,high efficiency(~81%at 532 nm),and broadband operation from 405 to 780 nm.Dynamic imaging under monochromatic and polychromatic lights is realized by the SAB/AAB,indicating various results at different propagation distances with a certain initial signal.Further investigation reveals that the SCPP on a soft substrate maintains its physical dimensions and optical properties unchanged during stretching.Our work enables wide potential applications in integrated optics,beam manipulation,and imaging.

Phyllotaxis-inspired nanosieves with multiplexed orbital angular momentum

Nanophotonic platforms such as metasurfaces,achieving arbitrary phase profiles within ultrathin thickness,emerge as miniaturized,ultracompact and kaleidoscopic optical vortex generators.However,it is often required to segment or interleave independent sub-array metasurfaces to multiplex optical vortices in a single nano-device,which in turn affects the device’s compactness and channel capacity.Here,inspired by phyllotaxis patterns in pine cones and sunflowers,we theoretically prove and experimentally report that multiple optical vortices can be produced in a single compact phyllotaxis nanosieve,both in free space and on a chip,where one meta-atom may contribute to many vortices simultaneously.The time-resolved dynamics of on-chip interference wavefronts between multiple plasmonic vortices was revealed by ultrafast time-resolved photoemission electron microscopy.Our nature-inspired optical vortex generator would facilitate various vortex-related optical applications,including structured wavefront shaping,free-space and plasmonic vortices,and high-capacity information metaphotonics.

Vortex 4.0 on chip

The orbital angular momentum(OAM)of light has promising applications,ranging from information multiplexing and high-speed optical communication to computation.Dynamically tunable and switchable vortex microlasers combined with direct photocurrent detection of the topological charges of OAM states have paved unexplored routes for the development and integration of fourth-generation(4.0)vortex technology,potentially on chip.