Vector vortex beams (VVBs) possess ubiquitous applications from particle trapping to quantum information. Recently, the bulky optical devices for generating VVBs have been miniaturized by using ...metasurfaces. Nevertheless, it is quite challenging for the metasurface‐generated VVBs to possess arbitrary polarization and phase distributions. More critical is that the VVBs' annular intensity profiles demonstrated hitherto are dependent on topological charges and are hence not perfect, posing difficulties in spatially shared co‐propagation of multiple vortex beams. Here, a single‐layer metasurface to address all those aforementioned challenges in one go is proposed, which consists of two identical crystal‐silicon nanoblocks with varying positions and rotation angles (i.e., four geometric parameters throughout). Those four geometric parameters are found to be adequate for independent and arbitrary control of the amplitude, phase, and polarization of light. Perfect VVBs with arbitrary polarization and phase distributions are successfully generated, and the constant intensity profiles independent of their topological charges and polarization orders are demonstrated. The proposed strategy casts a distinct perception that a minimalist design of just one single‐layer metasurface can empower such robust and versatile control of VVBs. That provides promising opportunities for generating more complex vortex field for advanced applications in structural light, optical micromanipulation, and data communication.
A single‐layer dielectric metasurface, consisting of two crystal‐silicon nanoblocks within one unit, is proposed to control the amplitude, phase, and polarization of light independently and arbitrarily. A genetic algorithm is used to obtain the geometric parameters of the metasurface element. The proposed strategy enables perfect vector vortex beam generation with constant annular intensity profiles, arbitrary phase, and polarization distributions.
In the growing list of 2D semiconductors as potential successors to silicon in future devices, metal‐halide perovskites have recently joined the family. Unlike other conversional 2D covalent ...semiconductors such as graphene, transition metal dichalcogenides, black phosphorus, etc., 2D perovskites are ionic materials, affording many distinct properties of their own, including high photoluminescence quantum efficiency, balanced large exciton binding energy and oscillator strength, and long carrier diffusion length. These unique properties make 2D perovskites potential candidates for optoelectronic and photonic devices such as solar cells, light‐emitting diodes, photodetectors, nanolasers, waveguides, modulators, and so on, which represent a relatively new but exciting and rapidly expanding area of research. In this Review, the recent advances in emerging 2D metal‐halide perovskites and their applications in the fields of optoelectronics and photonics are summarized and insights into the future direction of these fields are offered.
Metal‐halide perovskites exhibit great promise in photonics and optoelectronics applications. Here, a timely review of recent advances in 2D metal‐halide perovskites and their applications in the fields of optoelectronics and photonics for triggering new possibilities in the conceptual development of novel 2D metal‐halide perovskite materials, architectures, and devices is presented.
The Majorana fermion, which is its own antiparticle and obeys non-Abelian statistics, plays a critical role in topological quantum computing. It can be realized as a bound state at zero energy, ...called a Majorana zero mode (MZM), in the vortex core of a topological superconductor, or at the ends of a nanowire when both superconductivity and strong spin orbital coupling are present. A MZM can be detected as a zero-bias conductance peak (ZBCP) in tunneling spectroscopy. However, in practice, clean and robust MZMs have not been realized in the vortices of a superconductor because of contamination from impurity states or other closely packed Caroli–de Gennes-Matricon (CdGM) states, which hampers further manipulations of MZMs. Here, using scanning tunneling spectroscopy, we show that a ZBCP well separated from the other discrete CdGM states exists ubiquitously in the cores of free vortices in the defect-free regions of(Li0.84Fe0.16)OHFeSe, which has a superconducting transition temperature of 42 K. Moreover, a Dirac-cone-type surface state is observed by angle-resolved photoemission spectroscopy, and its topological nature is confirmed by band calculations. The observed ZBCP can naturally be attributed to a MZM arising from the chiral topological surface state of a bulk superconductor. Thus,(Li0.84Fe0.16)OHFeSeprovides an ideal platform for studying MZMs and topological quantum computing.
Abstract
Highly confined and low-loss polaritons are known to propagate isotropically over graphene and hexagonal boron nitride in the plane, leaving limited degrees of freedom in manipulating light ...at the nanoscale. The emerging family of biaxial van der Waals materials, such as α-MoO
3
and V
2
O
5
, support exotic polariton propagation, as their auxiliary optical axis is in the plane. Here, exploiting this strong in-plane anisotropy, we report edge-tailored hyperbolic polaritons in patterned α-MoO
3
nanocavities via real-space nanoimaging. We find that the angle between the edge orientation and the crystallographic direction significantly affects the optical response, and can serve as a key tuning parameter in tailoring the polaritonic patterns. By shaping α-MoO
3
nanocavities with different geometries, we observe edge-oriented and steerable hyperbolic polaritons as well as forbidden zones where the polaritons detour. The lifetime and figure of merit of the hyperbolic polaritons can be regulated by the edge aspect ratio of nanocavity.
An asymmetric (4+1) annulation of 3‐diazooxindoles/4‐diazooxisoquinolines with para‐quinone methides, catalyzed by a chiral phosphoric acid, has been described. A wide range of ...spirodihydrobenzofuran‐2,3′‐oxindoles/2,4′‐oxisoquinoline derivatives were afforded with excellent diastereo‐ and enantioselectivities. In this study, the possible reaction pathway was proposed and the synthetic applications were shown by a tenfold scale‐up conversion as well as the further transformations into other structurally more complex spirocyclic compounds. The significance of this protocol is highlighted by its metal‐free participation with heterocyclic diazo compounds as the direct nucleophile and extremely high efficiency in a straightforward and mild reaction process to access the structurally‐diverse spiro‐heterocyclic 2,3‐dihydrobenzofuran derivatives with good to excellent stereocontrol.
Carbon dioxide electroreduction (CO2RR) is a sustainable way of producing carbon‐neutral fuels. Product selectivity in CO2RR is regulated by the adsorption energy of reaction‐intermediates. Here, we ...employ differential phase contrast‐scanning transmission electron microscopy (DPC‐STEM) to demonstrate that Sn heteroatoms on a Ag catalyst generate very strong and atomically localized electric fields. In situ attenuated total reflection infrared spectroscopy (ATR‐IR) results verified that the localized electric field enhances the adsorption of *COOH, thus favoring the production of CO during CO2RR. The Ag/Sn catalyst exhibits an approximately 100 % CO selectivity at a very wide range of potentials (from −0.5 to −1.1 V, versus reversible hydrogen electrode), and with a remarkably high energy efficiency (EE) of 76.1 %.
Tin heteroatoms on a silver catalyst generate very strong and atomically localized electric fields, as disclosed by differential phase contrast‐scanning transmission electron microscopy (DPC‐STEM). This results in a 100 % selectivity for CO at a wide range of potentials (−0.5 V to −1.1 V vs. RHE).
Metasurfaces, artificial 2D structures, have been widely used for the design of various functionalities in optics. Jones matrix, a 2×2 matrix with eight parameters, provides the most complete ...characterization of the metasurface structures in linear optics, and the number of free parameters (i.e., degrees of freedom, DOFs) in the Jones matrix determines the limit to what functionalities we can realize. Great efforts have been made to continuously expand the number of DOFs, and a maximal number of six has been achieved recently. However, the realization of the ultimate goal with eight DOFs (full free parameters) has been proven as a great challenge so far. Here, we show that by cascading two layer metasurfaces and utilizing the gradient descent optimization algorithm, a spatially varying Jones matrix with eight DOFs is constructed and verified numerically and experimentally in optical frequencies. Such ultimate control unlocks opportunities to design optical functionalities that are unattainable with previously known methodologies and may find wide potential applications in optical fields.
Abstract
The colour gamut, a two-dimensional (2D) colour space primarily comprising hue and saturation (HS), lays the most important foundation for the colour display and printing industries. ...Recently, the metasurface has been considered a promising paradigm for nanoprinting and holographic imaging, demonstrating a subwavelength image resolution, a flat profile, high durability, and multi-functionalities. Much effort has been devoted to broaden the 2D HS plane, also known as the CIE map. However, the brightness (B), as the carrier of chiaroscuro information, has long been neglected in metasurface-based nanoprinting or holograms due to the challenge in realising arbitrary and simultaneous control of full-colour HSB tuning in a passive device. Here, we report a dielectric metasurface made of crystal silicon nanoblocks, which achieves not only tailorable coverage of the primary colours red, green and blue (RGB) but also intensity control of the individual colours. The colour gamut is hence extruded from the 2D CIE to a complete 3D HSB space. Moreover, thanks to the independent control of the RGB intensity and phase, we further show that a single-layer silicon metasurface could simultaneously exhibit arbitrary HSB colour nanoprinting and a full-colour hologram image. Our findings open up possibilities for high-resolution and high-fidelity optical security devices as well as advanced cryptographic approaches.
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