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Electromagnetic vortex carries the orbital angular momentum, one of the most fundamental properties of waves. The order of such vortex can be unbounded in principle, thus facilitating high-capability wave technologies for optical communications, photonic integrated circuits and others. However, it remains a key challenge to generate the high-order vortex beams in a reconfigurable, broadband and cost-effective manner. Here, inspired by the balanced-ternary concept, we demonstrate the reconfigurable generation of order-controllable vortices via cascaded -layer metasurfaces. We theoretically showed that different vortex modes can be generated by cascading metasurfaces, each one serving as an individual vortex beam generator for the order of (  = 0,1,2 …, ). As a proof-of-concept demonstration, a reconfigurable generation of 26 different vortex beams, with orders from 1 to 13 and from −1 to −13, is showcased in a broad millimeter-wave region by a cascade of 3 metasurfaces. Our method can be easily extended to vortex beam generator of arbitrary orders in a reconfigurable and easily implementable manner, paving a new avenue towards tremendous practical applications.

Structured light refers to the ability to tailor light in its many degrees of freedom, from the traditional control in time and space to more exotic multi-dimensional control for new forms of light, including vectorial light, toroidal excitations, spatio-temporal vortices, skyrmions, and optical mobius strips to name but a few. While the toolbox for the creation and detection of structured light has advanced tremendously, this has mostly been in the low power regime. More recently, structured light at high-power and high-intensities has emerged, fuelling new science and applications. In this progress report, we showcase the seminal work that has advanced this field, and indicate the open challenges and opportunities that remain.

In spite of a wide range of applications ranging from particle trapping to optical communication, conventional methods to generate vortex beams suffer from bulky configurations and limited performance. Here, we design, fabricate, and experimentally demonstrate orthogonal linear-polarization conversion and focused vortex-beam generation simultaneously by using gap-surface plasmon metasurfaces that enable high-performance linear-polarization conversion along with the complete phase control over reflected fields, reproducing thereby the combined functionalities of traditional half-wave plates, lenses, and q-plates. The fabricated metasurface sample features the excellent capability of orthogonal linear-polarization conversion and focused vortex-beam generation within the wavelength range of 800–950 nm with an averaged polarization conversion ratio of ~80% and absolute focusing efficiency exceeding 27% under normal illumination with the -polarized beam. We further show that this approach can be extended to realize a dual-focal metasurface with distinctly engineered intensity profiles by using segmented metasurfaces, where an orthogonal-polarized beam with Gaussian-distributed intensity and a vortex beam with intensity singularity have been experimentally implemented. The proposed multifunctional metasurfaces pave the way for advanced research and applications targeting photonics integration of diversified functionalities.

Compared with the on-axis vortex beam and the off-axis single vortex beam, the off-axis double vortex beam has more control degrees of freedom and brings rich physical properties. In this work, we investigate theoretically and experimentally the generation, topological charge (TC), and orbital angular momentum (OAM) of off-axis double vortex beams. It is demonstrated that the tilted lens method can detect not only the magnitudes and signs of two TCs of the off-axis double vortex beam but also the spatial distribution of the TCs. Moreover, the average OAM value of the off-axis double vortex beam decreases nonlinearly as the off-axis distance increases, although its TC is independent of the off-axis distance of phase singularities. The results indicate that the average OAM of the off-axis double vortex beam can be easily controlled by changing the relative position of two-phase singularities, thereby realizing the applications of multi-degrees of freedom particle manipulation, optical communication, and material processing.

Controlling the wavefront of light, especially on a subwavelength scale, is pivotal in modern optics. Metasurfaces present a unique platform for realizing flat lenses, called metalenses, with thicknesses on the order of the wavelength. Despite substantial effort, however, suppressing the chromatic aberrations over large operational bandwidths of metalenses still remains a challenge. Here, we develop a systematic design method enabling a simultaneous, polarization-insensitive control of the phase and the group delay of a light beam based on libraries of transmission-mode dielectric meta-elements. Mid-infrared achromatic metalenses are designed and theoretically analyzed to have diffraction-limited focal spots with vanishing chromatic aberrations in the operating wavelength range of 6–8.5 μm, while maintaining high focusing efficiencies of 41% on average. The proposed methodology, which can be used as a general design rule for all spectra, also provides a versatile design scheme for ultrashort pulse focusing and achromatic vortex-beam generation (orbital angular momentum), representing a major advance toward practical implementations of functional metalenses.

Vortex beams carrying orbital angular momentum (OAM) are considered to hold significant prospects in fields such as super-resolution imaging, high-capacity communications, and quantum optics. Therefore, the techniques of vortex beam generation have attracted extensive studies, in which the development of metasurfaces brings new vigor and vitality to it. However, the generation of reconfigurable vortex beams by metasurfaces at the incidence of arbitrary polarized electromagnetic (EM) waves holds challenges. In this study, an efficient and reconfigurable strategy utilizing PB phase-modulated circularly polarized waves and dynamic phase-modulated linearly polarized waves is proposed, enabling a polarization-locked fully polarization vortex beams generator. Based on this strategy, we designed and fabricated a prototype of the vortex beam generator for full polarization, which verifies the rotating Doppler effect and generates a time-varying vortex beam. All the results have been verified by simulation and measurements. In addition, the proposed strategy can be easily extended to other frequency regions and holds potential in areas such as information encryption, biosensing, and OAM multiplexing communication.

We propose a practical method of producing a single mode electron vortex beam suitable for use in a scanning transmission electron microscope (STEM). The method involves using a holographic “fork” aperture to produce a row of beams of different orbital angular momenta, as is now well established, magnifying the row so that neighboring beams are separated by about 1 µm, selecting the desired beam with a narrow slit, and demagnifying the selected beam down to 1–2 Å in size. We show that the method can be implemented by adding two condenser lenses plus a selection slit to a straight-column cold-field emission STEM. It can also be carried out in an existing instrument, the monochromated Nion high-energy-resolution monochromated electron energy-loss spectroscopy-STEM, by using its monochromator in a novel way. We estimate that atom-sized vortex beams with ≥20 pA of current should be attainable at 100–200 keV in either instrument.

Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer. In the case of 3D trapping with a single beam, this is termed optical tweezers. Optical tweezers are a powerful and noninvasive tool for manipulating small objects, and have become indispensable in many fields, including physics, biology, soft condensed matter, among others. In the early days, optical trapping was typically accomplished with a single Gaussian beam. In recent years, we have witnessed rapid progress in the use of structured light beams with customized phase, amplitude, and polarization in optical trapping. Unusual beam properties, such as phase singularities on-axis and propagation invariant nature, have opened up novel capabilities to the study of micromanipulation in liquid, air, and vacuum. We summarize the recent advances in the field of optical trapping using structured light beams.

We report an atmospheric multichannel data transmission system with channel separation by vortex beams of various orders, including half-integer values. For the demultiplexing of the communication channels, a multichannel diffractive optical element (DOE) is proposed, being matched with the used vortex beams. The considered approach may be realized without digital processing of the output images, but only based on the numbers of informative diffraction orders, similar to sorting. The system is implemented based on two spatial light modulators (SLMs), one of which forms a multiplexed signal on the transmitting side, and the other implements a multichannel DOE for separating the vortex beams on the receiving side. The stability of the communication channel to atmospheric interference and the crosstalk between the channels are investigated.

As an inherent degree of freedom, total angular momentum (TAM) of photons consisting of spin angular momentum and orbital angular momentum has inspired many advanced applications and attracted much attention in recent years. Probing TAM and tailoring beam’s TAM spectrum on demand are of great significance for TAM-based scenarios. We propose both theoretically and experimentally a TAM processor enabling tunable TAM manipulation. Such a processor consists of a set of quasi-symmetric units, and each unit is composed of a couple of diffraction optical elements fabricated through polymerized liquid crystals. Forty-two single TAM states are experimentally employed to prove the concept. The favorable results illustrate good TAM state selection performance, which makes it particularly attractive for high-speed large-capacity data transmission, optical computing, and high-security photon encryption systems.