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Catenary optics enables metasurfaces with higher efficiency and wider bandwidth, and is highly anticipated in the imaging system, super-resolution lithography, and broadband absorbers. However, the periodic boundary approximation without considering aperiodic electromagnetic crosstalk poses challenges for catenary optical devices to reach their performance limits. Here, perfect control of both local geometric and propagation phases is realized through field-driven optimization, in which the field distribution is calculated under real boundary conditions. Different from other optimization methods requiring a mass of iterations, the proposed design method requires less than ten iterations to get the efficiency close to the optimal value. Based on the library of shape-optimized catenary structures, centimeter-scale devices can be designed in ten seconds, with the performance improved by ~15%. Furthermore, this method has the ability to extend catenary-like continuous structures to arbitrary polarization, including both linear and elliptical polarizations, which is difficult to achieve with traditional design methods. It provides a way for the development of catenary optics and serves as a potent tool for constructing high-performance optical devices.

Wide-angle imaging and spectral detection play vital roles in tasks such as target tracking, object classification, and anti-camouflage. However, limited by their intrinsically different architectures, as determined by frequency dispersion requirements, their simultaneous implementation in a shared-aperture system is difficult. Here, we propose a novel concept to realize reconfigurable dual-mode detection based on electrical-control tunable metasurfaces. As a proof-of-concept demonstration, the simultaneous implementation of wide-angle imaging and polarization-spectral detection in a miniature shared-aperture meta-optical system is realized for the first time via the electrical control of cascaded catenary-like metasurfaces. The proposed system supports the imaging (spectral) resolution of approximately 27.8 line-pairs per millimeter (lp·mm−1; ∼80 nm) for an imaging (spectral) mode from 8 to 14 μm. This system also bears a large field of view of about 70°, enabling multi-target recognition in both modes. This work may promote the miniaturization of multifunctional optical systems, including spectrometers and polarization imagers, and illustrates the potential industrial applications of meta-optics in biomedicine, security, space exploration, and more.

Abstract Reconfigurable metasurfaces have exhibited significant potential in wireless communication owing to their capacity to transmit information without relying on traditional complex radio frequency (RF) chain transmitters. Nonetheless, the majority of metasurface‐based wireless communication systems modulate signals only in the time domain. Here, an amplitude‐phase reconfigurable metasurface is proposed to establish a wireless communication system that can simultaneously transmit different messages to users by encoding digital signals within the spatial domain. By changing the bias voltages of varactors integrated in the meta‐atom, the reconfigurable metasurface can achieve independent 3‐bit phase and 1‐bit amplitude coding. Through a beamforming methodology, the proposed metasurface generates diverse scattering beams with suppressed sidelobe levels, which not only enables multiple channels through space coding but also reduces signal leakage in undesired directions. Numerical simulations and experiments are carried out to verify the beamforming scheme, and a dual‐channel wireless communication system is established. The results show that two distinct images can be simultaneously retrieved by two separate users, which demonstrates the dual‐channel transmission capability of the wireless communication system. The proposed strategy opens up an avenue for implementing multi‐channel wireless communication systems, which indicates its great potential in multiple‐user collaborative wireless communication and radar systems.

Abstract Metasurfaces, 2D arrays of nanostructures, have gained significant attention in recent years due to their ability to manipulate light at the subwavelength scale. Their diverse applications range from advanced optical devices to sensing and imaging technologies. However, the mass production of dielectric metasurfaces with tailored properties for visible light has remained a challenge. Therefore, the demand for efficient and cost‐effective fabrication methods for metasurfaces has driven the continuing development of various techniques. In this research article, a high‐throughput production method is presented for multifunctional dielectric metasurfaces in the visible light range using one‐step high‐index TiO2‐polymer composite (TPC) printing, which is a variant of nanoprinting lithography (NIL) for the direct replication of patterned multifunctional dielectric metasurfaces using a TPC material as the printing ink. The batch fabrication of dielectric metasurfaces is demonstrated with controlled geometry and excellent optical response, enabling high‐performance light‐matter interactions for potential applications of visible meta‐displays.

Photonic integrated circuits (PICs) have attracted significant interest in communication, computation, and biomedical applications. However, most rely on highly integrated PICs devices, which require a low-loss and high-integration guided wave path. Owing to the various dimensions of different integrated photonic devices, their interconnections typically require waveguide tapers. Although a waveguide taper can overcome the width mismatch of different devices, its inherent tapering width typically results in a long length, which fundamentally limits the efficient interconnection between devices with a high scaling ratio over a short distance. Herein, we proposed a highly integrated on-chip metalens that enables optical interconnections between devices with high width-scaling ratios by embedding a free-form metasurface in a silicon-on-insulator film. The special geometric features endow the designed metalens with high coupling efficiency and high integration. The device has a footprint of only 2.35 μm in the longitudinal direction and numerical aperture of 2.03, enabling beam focusing and collimation of less than 10 μm between devices with width-scaling ratio of 11. For the fundamental transverse electric field (TE0) mode, the relative transmittance is as high as 96% for forward incidence (from wide to narrow waveguides), whereas the metalens can realize wavefront shaping for backward incidence, which can be used in optical phase arrays. This study provides new ideas for optical interconnect design and wavefront shaping in high-integration PICs. Our design approach has potential applications in directional radiators, LiDAR, on-chip optical information processing, analogue computing, and imaging.

Super-resolution (SR) microscopy has dramatically enhanced our understanding of biological processes. However, scattering media in thick specimens severely limits the spatial resolution, often rendering the images unclear or indistinguishable. Additionally, live-cell imaging faces challenges in achieving high temporal resolution for fast-moving subcellular structures. Here, we present the principles of a synthetic wave microscopy (SWM) to extract three-dimensional information from thick unlabeled specimens, where photobleaching and phototoxicity are avoided. SWM exploits multiple-wave interferometry to reveal the specimen’s phase information in the area of interest, which is not affected by the scattering media in the optical path. SWM achieves ~0.42 λ/NA resolution at an imaging speed of up to 106 pixels/s. SWM proves better temporal resolution and sensitivity than the most conventional microscopes currently available while maintaining exceptional SR and anti-scattering capabilities. Penetrating through the scattering media is challenging for conventional imaging techniques. Remarkably, SWM retains its efficacy even in conditions of low signal-to-noise ratios. It facilitates the visualization of dynamic subcellular structures in live cells, encompassing tubular endoplasmic reticulum (ER), lipid droplets, mitochondria, and lysosomes.

Metalenses have gained significant attention and have been widely utilized in optical systems for focusing and imaging, owing to their lightweight, high-integration, and exceptional-flexibility capabilities. Traditional design methods neglect the coupling effect between adjacent meta-atoms, thus harming the practical performance of meta-devices. The existing physical/data-driven optimization algorithms can solve the above problems, but bring significant time costs or require a large number of data-sets. Here, we propose a physics-data-driven method employing an “intelligent optimizer” that enables us to adaptively modify the sizes of the meta-atom according to the sizes of its surrounding ones. The implementation of such a scheme effectively mitigates the undesired impact of local lattice coupling, and the proposed network model works well on thousands of data-sets with a validation loss of 3×10−3. Based on the “intelligent optimizer”, a 1-cm-diameter metalens is designed within 3 hours, and the experimental results show that the 1-mm-diameter metalens has a relative focusing efficiency of 93.4% (compared to the ideal focusing efficiency) and a Strehl ratio of 0.94. Compared to previous inverse design method, our method significantly boosts designing efficiency with five orders of magnitude reduction in time. More generally, it may set a new paradigm for devising large-aperture meta-devices.

Usual methods for optical encryption suffer from a tradeoff between the level of security and the complexity of operation given by multiple optical measurements or digital postprocessing. Here, the authors show a multi-d.o.f. metasurface-based vector optical manipulation protocol enabling secure decryption in real time.

Dielectric metasurfaces are crucial for enhancing optical nonlinear generation, particularly membrane metasurfaces with multipolar resonances and compact size. Investigating silicon dimer-hole membrane metasurfaces, Rahmani, and Xu show how bound states in the continuum (BICs) can be formed and transformed into quasi-BICs by adjusting hole gaps. This innovation enables efficient conversion of infrared images to visible range, promising applications in nonlinear photonics and near-infrared imaging technologies.

Imaging polarimetry is one of the most widely used analytical technologies for object detection and analysis. To date, most metasurface-based polarimetry techniques are severely limited by narrow operating bandwidths and inevitable crosstalk, leading to detrimental effects on imaging quality and measurement accuracy. Here, we propose a crosstalk-free broadband achromatic full Stokes imaging polarimeter consisting of polarization-sensitive dielectric metalenses, implemented by the principle of polarization-dependent phase optimization. Compared with the single-polarization optimization method, the average crosstalk has been reduced over three times under incident light with arbitrary polarization ranging from 9 μm to 12 μm, which guarantees the measurement of the polarization state more precisely. The experimental results indicate that the designed polarization-sensitive metalenses can effectively eliminate the chromatic aberration with polarization selectivity and negligible crosstalk. The measured average relative errors are 7.08%, 8.62%, 7.15%, and 7.59% at 9.3, 9.6, 10.3, and 10.6 μm, respectively. Simultaneously, the broadband full polarization imaging capability of the device is also verified. This work is expected to have potential applications in wavefront detection, remote sensing, light-field imaging, and so forth.

Abstract High flexibility, porosity, and antibacterial activity are extremely desired for wearable health monitoring, which is beneficial to simultaneously promote wearing comfort and safety. In this study, an antibacterial nanofibers‐based triboelectric generator (AN‐TENG) composed of the flexible chitosan/polyvinylpyrrolidone modified with halloysite nanotubes (CTS/PVP/HNTs) nanofibers and cube‐arrays structured Ecoflex film is proposed for simultaneously energy harvesting and self‐powered human motion monitoring. The open‐circuit voltage (280 V), short‐circuit current (3.98 μA), and transferred charge (51 nC) of the CTS/PVP/HNTs nanofibers TENG at the optimal compound concentration are increased by 90.8%, 86.92%, and 96.2%, respectively, compared to the CTS/PVP nanofibers one (size: 3 cm × 3 cm, mechanical force: 10 N @1 Hz), revealing good real‐time monitoring ability for human wrist, elbow, and finger motion. An antibacterial test is carried out to evaluate the antibacterial activity and the antibacterial rate of the nanofibers against Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538) based on the current national standard GB/T 31402–2015, indicating good antibacterial properties of the nanofibers. This research offers an ingenious strategy to establish an antibacterial nanofibers‐based TENG for self‐powered motion monitoring and energy harvesting and offers a new insight to improve the practical security of wearable electronic devices.

The spin angular momentum (SAM) and orbital angular momentum (OAM) are unique properties of vortex beams and widely used in optical communication and sensing, wherein unambiguous detection of them is of significance. However, the existing methodologies mostly require complicated optical setups, bulky devices, multiple measurements and suffer from limited detection range and ability. Here, we propose a novel angular momentum (AM) detection mechanism that based on optical symmetry transformation for single-shot AM detection within a large mode space. We first give a detailed theoretical derivation and then carry numerical verification. Subsequently, an ultra-compact metasurface is designed so that an OAM mode high up to 150 orders can be determined with a single-shot measurement. Finally, a spin-decoupled metasurface combining the propagation and geometric phase is constructed, which allows simultaneous discrimination of SAM and OAM. Our proposed method may be promising for a wide range of applications in AM measurements and polarization singularity detection.

Abstract Graphene is a promising candidate for the next‐generation infrared array image sensors at room temperature due to its high mobility, tunable energy band, wide band absorption, and compatibility with complementary metal oxide semiconductor process. However, it is difficult to simultaneously obtain ultrafast response time and ultrahigh responsivity, which limits the further improvement of graphene photoconductive devices. Here, a novel graphene/C60/bismuth telluride/C60/graphene vertical heterojunction phototransistor is proposed. The response spectral range covers 400–1800 nm; the responsivity peak is 106 A W−1; and the peak detection rate and peak response speed reach 1014 Jones and 250 µs, respectively. In addition, the regulation of positive and negative photocurrents at a gate voltage is characterized and the ionization process in impurities of the designed phototransistor at a low temperature is analyzed. Tunable bidirectional response provides a new degree of freedom for phototransistors' signal resolution. The analysis of the dynamic change process of impurity energy level is conducted to improve the device's performance. From the perspective of manufacturing process, the ultrathin phototransistor (20–30 nm) is compatible with functional metasurface to realize wavelength or polarization selection, making it possible to achieve large‐scale production of integrated spectrometer or polarization imaging sensor by nanoimprinting process.

Multi-wavelength imaging ability is important for bio-imaging, to obtain multi-modal information of biological activities. We propose a multi-wavelength super-resolution imaging method, employing the Bloch surface waves (BSWs) supported by one-dimensional photonic crystal as subwavelength structured illumination fields. Here 488 nm (blue), 532 nm (green), and 632.8 nm (red) are chosen as the illumination wavelengths, and a two-dimensional equilateral triangular grating is designed to couple the incident plane waves to the BSWs in the all-dielectric photonic crystal. The triangular grating ensures a more uniform resolution improvement along with whole lateral directions and provides better imaging quality compared with lattice grating. In our demonstration, the resolution improvements are above 2.4 fold for the three wavelengths, and lateral resolutions are below 120 nm in the Rayleigh criterion. Moreover, as the illumination device is composed of a periodic planar structure, the larger field of view is achievable. The proposed method could achieve multi-wavelength wide-field super-resolution surface imaging while maintaining high speed, good imaging quality and bio-compatibility.

Metasurfaces, which are ultrathin planar artificial materials flexibly controlling the phase, amplitude, and polarization of the light, have facilitated the high integration and miniaturization of hyperspectral imaging systems. However, the pushbroom hyperspectral imaging systems based on metasurfaces usually face the large smile and keystone, which reduces the spectral uniformity and the fidelity of the spectral information. Moreover, the employment of many metasurfaces would cause manufacturing difficulties. In this paper, a planar hyperspectral imager only using two metasurfaces is proposed to achieve a spectral resolution of 3.5 nm in 850-1000 nm band with the near diffraction-limited focusing capability, and its maximum of smile and keystone reach to 124.4 μm and 33.6 μm for the image plane size of 4.75 mm × 1.35 mm and pixel size of 26 μm × 26 μm, respectively. This imager can provide a promising avenue for portable environmental monitoring systems and wearable electronic consumer products.

Plasmonic imaging technology can offer a novel way for nanofabrication, with the advantages of low-cost, high yield, and large area, having potentially promising applications in various nanostructures manufacturing. However, the previous studies mainly focus on the simulation and experimental research of fixed period or fixed structure size metasurface fabrication, which limits the range of its applications. In this paper, we proposed and analyzed the imaging characteristics of the reflective plasmonic structures, selected the best structure in the fabrication process by parameter analyses, and concluded that the air gap has the most significant influence on imaging quality of plasmonic imaging technology. Then we experimentally demonstrated its ability in fabricating multi-scale patterns. A 10mm × 16 mm large-scale structural color metasurface with periods from 414.3 to 580 nm has been designed and manufactured. Furthermore, the feasibility of fabricating metasurface whose radius varies from 75 to 150 nm is also verified under the same condition. The proposed method is expected to have widespread applications in multi-functional metasurface devices.

Abstract With inherent orthogonality, both the spin angular momentum (SAM) and orbital angular momentum (OAM) of photons have been utilized to expand the dimensions of quantum information, optical communications, and information processing, wherein simultaneous detection of SAMs and OAMs with a single element and a single-shot measurement is highly anticipated. Here, a single azimuthal-quadratic phase metasurface-based photonic momentum transformation (PMT) is illustrated and utilized for vortex recognition. Since different vortices are converted into focusing patterns with distinct azimuthal coordinates on a transverse plane through PMT, OAMs within a large mode space can be determined through a single-shot measurement. Moreover, spin-controlled dual-functional PMTs are proposed for simultaneous SAM and OAM sorting, which is implemented by a single spin-decoupled metasurface that merges both the geometric phase and dynamic phase. Interestingly, our proposed method can detect vectorial vortices with both phase and polarization singularities, as well as superimposed vortices with a certain interval step. Experimental results obtained at several wavelengths in the visible band exhibit good agreement with the numerical modeling. With the merits of ultracompact device size, simple optical configuration, and prominent vortex recognition ability, our approach may underpin the development of integrated and high-dimensional optical and quantum systems.

Structured illumination microscopy (SIM) is one of the most powerful and versatile super-resolution methods due to its live-cell imaging ability of subcellular structures with high speed. In this paper, we propose an alternative SIM assisted by Bloch surface wave (BSW). Through replacing the conventional laser interference fringes with sub-diffraction BSW counterparts with higher spatial frequency, the imaging resolution of SIM could be enhanced greatly and the super-resolution imaging capability down to 80 nm could be achieved. Compared with traditional wide-field fluorescence microscopy, this BSW SIM demonstrates 2.78 times enhancement in imaging resolution, which surpasses general SIM with only 2 times improvement. Moreover, the structured illumination intensity could be boosted drastically, which is beneficial to nonlinear super-resolution imaging techniques, such as saturated SIM. This BSW SIM would provide a super-resolution, wide field of view approach for surface super-resolution fluorescent imaging while maintaining high imaging speed and good bio-compatibility.

Theoretically, the topological charge l in the vortex can be any integer or fraction, thus the vortex carrying different topological charges can form an infinitely orthogonal orbital angular momentum state space, which can provide new dimensional resources for optical communication. However, high-capacity optical communication requires low delay, thus real-time detection of the OAM is significant for communication. Metasurfaces have the characteristics of low loss, ultra-thin, easy integration, and flexible phase controls, which provide a meaningful way to realize integrated OAM generation and detection. Here, an optimized streamlined metasurface (OSM) is presented, which can detect high-order vortex beams in a single, simple, and rapid manner by photon momentum transformation (PMT). Since different vortices are converted into focusing modes with distinct azimuthal coordinates on a transverse plane through PMT, a single measurement can determine OAMs in an ample mode space. In addition, the OSM can detect more and higher order OAMs compared with a discrete metasurface (DM) at the same size, due to its better wavefront sampling capabilities. With the merits of an ultra-compact device size, simple optical structure, and outstanding vortex recognition ability, our approach may underpin the development of integrated optics and quantum systems.

Breaking the diffraction limit to realize imaging at the nanoscale is challenging in scientific research. Traditional sub-diffraction focusing metalens is obtained by arranging artificially selected unit cells, of which the design process is passive and complex. This paper brings up an inverse design idea of planar sub-diffraction focusing metalens based on super-oscillatory theory to solve these problems, starting from a desired focusing performance. The sub-diffraction focusing metalens is then obtained by iterative topology optimization with different initial structures. We introduce the adjoint-based topology inverse optimization into the structural design of sub-diffraction focusing metalens, which provides another way to design a sub-diffraction metalens for far-field unmarked super-resolution imaging. Based on this idea, we achieve a sub-diffraction focusing characterized by a focal radius of 0.75 times the Rayleigh diffraction limit, optimizing from a diffraction-limited focusing metalens. Moreover, focal radii between 0.63 and 0.73 times the Rayleigh diffraction limit are achieved by optimizing 11 sets of random initial metasurface structures with even no focusing performance. The results indicate that our method is independent of the initial structure distribution, which can be extended to the inverse design of other functional metasurfaces in imaging, lithography, and other fields.

Abstract Low symmetric two dimensional (2D) semiconductors are of great significance for their potential applications in polarization‐sensitive photodetection and quantum information devices. However, their real applications are limited by their photo‐detecting wavelength ranges, which are restricted by their fundamental optical bandgaps. Recently, intercalation has been demonstrated to be a powerful strategy to modulate the optical bandgaps of 2D semiconductors. Here, the authors report the self‐driven oxygen (O2) intercalation induced bandgap reduction from 1.75 to 1.19 eV in gallium telluride (GaTe) in air. This bandgap shrinkage provides the long‐wavelength detection threshold above ≈1100 nm for O2 intercalated GaTe (referred to as GaTeO2), well beyond the cut‐off wavelength at ≈708 nm for pristine GaTe. The GaTeO2 photodetectors have a high photoresponsivity, and highly anisotropic photodetection behavior to even sub‐waveband radiation. The dichroic ratio (Imax/Imin) of photocurrent is about 1.39 and 2.9 for 600 nm and 1100 nm, respectively. This findings demonstrates a broadband photodetector utilizing GaTe after breaking through its bandgap limitation by self‐driven O2 intercalation in air and further reveal its photoconductivity anisotropic nature. This provides design strategies of 2D materials‐based high‐performance broadband photodetectors for the exploration of polarized state information.

Wave plates as important polarization control devices are widely used in the applications of biomedical imaging, fiber optical communication, astronomy, semiconductor industry and aerospace etc. To make the wave plate actively tunable, we propose a rectangular antenna-based metasurface based on the phase-changing material Ge2Sb2Te5 (GST) with high transmittance and polarization conversion rate. Before the GST phase transition, the metasurface operates as a quarter-wave plate in the wavelength range of 10.0-11.9 μm. After the GST turning into crystalline state, the metasurface operates as a half-wave plate in the wavelength range of 10.3-10.9 μm. The physical mechanism for the high transmittance efficiency and polarization conversion rate attributes to the combination of the electric dipole and magnetic dipole resonances. Moreover, the adjustable wavelength range can be further extended by changing the geometry of antenna-based GST to selectively enhancing or suppressing the electric and magnetic resonances. This work provides a new strategy for tunable wave plate, which would have the potential in the application of multi-functional integrated optical systems.

Summary: Although tremendous efforts have been devoted to investigating the analogy between the surface plasmon polariton and its spoof counterparts, it remains elusive that a single thin spoof plasmonic metalens realizes wide-angle focusing and wide field-of-view (FOV) imaging. Here, we propose a spoof plasmonic metasurface that can impart arbitrary phase with high transmittance, which comprises two-dimensional (2D) gradient spoof-insulator-spoof waveguides. With the developed catenary field and dispersion theory, their intrinsic physics is theoretically analyzed. As a proof of concept, a spoof plasmonic metalens with a thickness of 0.15λ has been elaborately designed and experimentally demonstrated for wide-angle (∼170°) focusing and wide FOV (∼40°) imaging. To the best of our knowledge, it is the first experimental demonstration of wide FOV imaging of a 2D object with single thin and planar metalens in the microwave regime. The proposed method offers a promising solution to compact cameras, integrated imaging, and detection systems. : Optical Imaging; Electromagnetic Waves; Surface Subject Areas: Optical Imaging, Electromagnetic Waves, Surface

In recent years, with the development of photonic crystals, metamaterials, metasurfaces, and other related disciplines, the relationship between the structures and functionalities of artificial optical/electromagnetic materials and devices has become a research hotspot. This article reviews the optical/electromagnetic properties and performance of typical artificial micro/nanostructures. Based on the analogy of mechanics and optics/electromagnetism, the concept of “Electromagnetic Architectures” is proposed. In particular, we reviewed several typical methods for the study of optical/electromagnetic structural‐functional relationships, including semi‐classical analytical models, heuristic optimization methods, deep neural networks, topological optimization methods, etc. The viewpoint of this paper may push further researches on the structural‐functional relationship of artificially structured materials and devices, and find broad application prospects in imaging, communication, photonic chips, among many others.

Monolithic integrated mode converters with high integration are essential to photonic integrated circuits (PICs), and they are widely used in next-generation optical communications and complex quantum systems. It is expected that PICs will become more miniaturized, multifunctional, and intelligent with the development of micro/nano-technology. The increase in design space makes it difficult to realize high-performance device design based on traditional parameter sweeping or heuristic design, especially in the optimal design of reconfigurable PIC devices. Combining the mode coupling theory and adjoint calculation method, we proposed a design method for a switchable mode converter. The device could realize the transmission of TE0 mode and the conversion from TE0 to TE1 mode with a footprint of 0.9 × 7.5 μm2 based on the phase change materials (PCMs). We also found that the mode purity could reach 78.2% in both states at the working wavelength of 1.55 μm. The designed method will provide a new impetus for programmable photonic integrated devices and find broad application prospects in communication, optical neural networks, and sensing.

We demonstrate the generation of a space-variant vector beam with catenary-shaped polarization states based on the polarization interferometry. With a spatial light modulator and a common path interferometric configuration, two orthogonally circularly polarized beams with different phase modulation overlap each other, yielding the vector beams. In addition, the polarization states of this vector beam are scalable to the arbitrary spatial distribution because of its great flexibility and universal applicability. It is expected that this vector beam may have many potential and intriguing applications in the micro/nano material processing, liquid crystal elements fabrication and optical micro-manipulation, and so on.

Summary: Recently, metasurface-based multichannel optical vortex arrays have attracted considerable interests due to its promising applications in high-dimensional information storage and high-secure information encryption. In addition to the well-known wavelength and polarization multiplexing technologies, the diffraction angle of light is an alternative typical physical dimension for multichannel optical vortex arrays. In this paper, based on angular multiplexing, we propose and demonstrate multichannel optical vortex arrays by using ultrathin geometric metasurface. For a circularly polarized incident light, the desired optical vortex arrays are successfully constructed in different diffraction regions. Moreover, the diffraction angle of the optical vortex array can be regulated by changing the illumination angle of incident light. Capitalizing on this advantage, the angular-multiplexed recombination of optical vortex array is further investigated. The combination of the diffraction angle of light and optical vortex array may have significant potential in applications of optical display, free-space optical communication, and optical manipulation.

Abstract Optical metasurfaces enable novel ways to locally manipulate light's amplitude, phase, and polarization, underpinning a newly viable technology for applications, such as high‐density optical storage, holography, and displays. Here, a high‐security‐level platform enabled by centimeter‐scale plasmonic metasurfaces with full‐color, high‐purity, and enhanced‐information‐capacity properties is proposed. Multiple types of independent information can be embedded into a single metamark using full parameters of light, including amplitude, phase, and polarization. Under incoherent white light, the metamark appears as a polarization‐ and angle‐encoded full‐color image with flexibly controlled hue, saturation, and brightness, while switching to multiwavelength holograms under coherent laser illumination. More importantly, for actual applications, the extremely shallow functional layer makes such centimeter‐scale plasmonic metamarks suitable for cost‐effective mass production processes. Considering these superior performances of the presented multifunctional plasmonic metasurfaces, this work may find wide applications in anticounterfeiting, information security, high‐density optical storage, and so forth.

Broadband absorber in the terahertz region (0.1-10 THz) has attracted considerable attentions due to its important applications in detecting, imaging, and electromagnetic stealth. Recently, terahertz absorber with broadband features has been widely investigated, however, the achievement of ultrabroad bandwidth is still challenging due to the limitations of complex structural design and fabrication processes. In this paper, an ultrabroadband terahertz absorber covering the entire terahertz regime (0.1-10 THz) based on the heavily doped silicon has been designed and fabricated, which is composed of double-layer binary gratings filled with the SU-8 photoresist. Antireflection techniques (SU-8 layer) were utilized to further promote the performance of the terahertz absorber at high frequencies through matching the impedance between free space and doped-silicon substrate. The measured absorption exceeding 87% within the frequency range of 0.3-10 THz has verified the proposed approach in designing the ultrabroadband terahertz absorber. Furthermore, the designed absorber remains high performance in the case of wide-angle incidence even up to 60°. Benefiting from the simple structure, the absorber is easy to be fabricated by common optical lithography. We believe that the results of this paper could broaden the application areas of terahertz absorbers.

The emergence of the metasurface has spawned an ultrathin, compact, and planner way to generate the orbital angular momentum (OAM) beam array. Several types of OAM beam array generators based on the metasurface have been reported, however, most of them only performed at the certain wavelength for lack of the wavelength-dependent modulation, which restricted the flexibility and capacity of the generators. Here, we propose a single-layered metasurface to realize the generation of the wavelength-dependent three-dimensional (3-D) volumetric vortex beam array. The metasurface is composed by two different nanoantennas, which shows the distinct properties of wavelength selectivity and wavelength-dependent phase modulation. By employing such properties, 3-D volumetric vortex beams operating at different wavelengths can be multiplexed. Our design may facilitate the development of the optical multiplexing, and the wavelength-dependent control of the OAM light will improve the capacity and the security of the optical information.

Abstract In this article, a dual-band wide-angle metamaterial perfect absorber is proposed to achieve absorption at the wavelength where laser radar operates. It is composed of gold ring array and a Helmholtz resonance cavity spaced by a Si dielectric layer. Numerical simulation results reveal that the designed absorber displays two absorption peaks at the target wavelength of 10.6 μm and 1.064 μm with the large frequency ratio and near-unity absorptivity under the normal incidence. The wide-angle absorbing property and the polarization-insensitive feature are also demonstrated. Localized surface plasmons resonance and Helmholtz resonance are introduced to analyze and interpret the absorbing mechanism. The designed perfect absorber can be developed for potential applications in infrared stealth field.

Abstract Catenary functions are exciting and fundamental building blocks in constructing various kinds of waves in subwavelength structures. Here, a simple yet powerful approach inspired by catenary optics is proposed to realize efficient manipulation of electromagnetic waves in terms of both amplitude and phase. By properly engineering the catenary electromagnetic fields and frequency dispersion, lightweight metafilm‐based broadband absorbers with polarization‐independent bandwidth covering 0.65–6.2 GHz are experimentally achieved, and the bandwidth is further broadened to 0.9–40 GHz. With the same approach, a large‐scale flat antenna based on generalized reflection is demonstrated in the satellite communication system. To enable the batch manufacturing, a flexible substrate–based microfabrication process is developed with a minimum feature size of down to sub‐micrometer and total size up to almost 1 m. These results may provide important guidance for the design of metasurface‐based devices.

We theoretically investigate metasurface spatiotemporal dynamics by introducing laser chaotic dynamics into metasurface domain. The spatiotemporal dynamics takes advantage of both the time-dependent dynamics of optical chaos and the local spatial regulation capability of metasurface. Specifically, an optical spatiotemporal dynamic phenomenon, termed as vector-polarization optical chaos (VPOC), is demonstrated through asymmetric photonic spin-orbit interactions between all-dielectric metalens and chaotic polarization light from the vertical-cavity surface-emitting laser. The VPOC has spatially inhomogeneous polarization distribution with dynamically varied spatial structure and polarization singularity, while the corresponding intensity time series is temporally chaotic, characterized by positive largest Lyapunov exponent and finite correlation dimension. We found that the two nonlinear indices keep invariant for different polarization-resolved intensity time series due to the circular symmetry of metalens. Our results open an avenue for emerging spatiotemporal optical dynamics with metasurface and may find exciting applications in spatiotemporal light control, free-space secure optical communication, and optical chaos integrated chip.

Quasi-continuous metasurfaces are widely used in various optical systems and their subwavelength structures invalidate traditional design methods based on scalar diffraction theory. Here, a novel vector iterative Fourier transform algorithm (IFTA) is proposed to realize the fast design of quasi-continuous metasurface beam splitters with subwavelength structures. Compared with traditional optimization algorithms that either require extensive numerical simulations or lack accuracy, this method has the advantages of accuracy and low computational cost. As proof-of-concept demonstrations, several beam splitters with custom-tailored diffraction patterns and a 7 × 7 beam splitter are numerically demonstrated, among which the maximal diffraction angle reaches 70° and the best uniformity error reaches 0.0195, showing good consistency with the target energy distribution and these results suggest that the proposed vector IFTA may find wide applications in three-dimensional imaging, lidar techniques, machine vision, and so forth.

Despite their great potential for energy-saving applications, it is still challenging to design passive radiative cooling (RC) materials with simultaneous high performance and simple structures based on traditional design philosophy. To solve the contradiction between optimization speed and corresponding performance, we present a flexible hybrid optimization strategy based on a genetic algorithm (GA) in conjunction with the transfer matrix method and introducing the calculation of radiative cooling power density in the evaluation function of the GA. As a demonstration, an optimized coating with 1.5-μm-overlapping MgF2 and Si3N4 layers on top of a silver film was numerically designed. Based on a detailed analysis of the material’s electromagnetic properties and cooling performance, this coating achieved a radiative cooling power density of 62 W/m2 and a temperature reduction of 6.8 °C at an ambient temperature of 300 K. Our optimization strategy may have special significance in the design of high-performance RC materials or other multi-spectral engineering materials with simple structures.

As two-dimensional metamaterials, metasurfaces have received rapidly increasing attention from researchers all over the world. Unlike three-dimensional metamaterials, metasurfaces can be utilized to control the electromagnetic waves within one infinitely thin layer, permitting substantial advantages, such as easy fabrication, low cost, and high degree of integration. This paper reviews the history and recent development of metasurfaces, with particular emphasis on the theory and applications relating to the frequency response, phase shift, and polarization state control. Based on the current status of various applications, the challenges and future trends of metasurfaces are discussed.

Chiral metamaterials represent a special type of artificial structures that cannot be superposed to their mirror images. Due to the lack of mirror symmetry, cross-coupling between electric and magnetic fields exist in chiral mediums and present unique electromagnetic characters of circular dichroism and optical activity, which provide a new opportunity to tune polarization and realize negative refractive index. Chiral metamaterials have attracted great attentions in recent years and have given rise to a series of applications in polarization manipulation, imaging, chemical and biological detection, and nonlinear optics. Here we review the fundamental theory of chiral media and analyze the construction principles of some typical chiral metamaterials. Then, the progress in extrinsic chiral metamaterials, absorbing chiral metamaterials, and reconfigurable chiral metamaterials are summarized. In the last section, future trends in chiral metamaterials and application in nonlinear optics are introduced.

Gradient–index metamaterial is crucial in the spatial manipulation of electromagnetic wave. Here we present an efficient approach to extend the bandwidth of phase modulation by utilizing the broadband characteristic of low-quality (Q) meta-surface in the reflection mode. The dispersion of the meta-surface is engineered to compensate the phase difference induced by frequency change. Meanwhile, a thin gradient index cover layer is added on the top of meta-surface to extend the phase modulation range to cover the entire [0, 360°]. As a proof of concept, anomalous nearly perfect reflection with relative bandwidth near 40% is demonstrated in the microwave regime.

We present the design, fabrication and experimental demonstration of an electrically active absorber at microwave frequency. Unlike those proposed before, simulation and experiment data present that its working frequency and absorbing intensity can be both but separately controlled. The electromagnetic coupling analysis reveals that the feature arises from the dividable frequency and amplitude modulation on an active magnetic resonator controlled by varactor and pin diodes. Such separable modulating behaviors are further confirmed by the equivalent LC circuit model. It is believed that this will be an important step towards smart application of active absorber.