Large-scale achromatic flat lens by light frequency-domain coherence optimization

Full-Color Quasi-Achromatic Imaging with a Dual-Functional Metasurface

Achieving broadband achromaticity in the visible spectrum is critical for enhancing the imaging performance of metalenses. However, many previous studies remain constrained by small device sizes or small numerical aperture. In this study, we propose a polarization-multiplexed metalens capable of generating zero- and high-order Bessel beams to achieve quasi-achromatic correction without size limitations. An image subtraction method with the two polarization channels is developed to mitigate the Bessel beam sidelobes to improve imaging quality. Our results demonstrate an effective quasi-achromatic focusing and imaging over a continuous wavelength range of 450-700 nm with long focus depth. The image subtraction method significantly enhances the image clarity and contrast, providing new insights for full-color imaging and detection.

Dispersion-engineered spin photonics based on folded-path metasurfaces

Spin photonics revolutionizes photonic technology by enabling precise manipulation of photon spin states, with spin-decoupled metasurfaces emerging as pivotal in complex optical field manipulation. Here, we propose a folded-path metasurface concept that enables independent dispersion and phase control of two opposite spin states, effectively overcoming the limitations of spin photonics in achieving broadband decoupling and higher integration levels. This advanced dispersion engineering is achieved by modifying the equivalent length of a folded path, generated by a virtual reflective surface, in contrast to previous methods that depended on effective refractive index control by altering structural geometries. Our approach unlocks previously unattainable capabilities, such as achieving achromatic focusing and achromatic spin Hall effect using the rotational degree of freedom, and generating spatiotemporal vector optical fields with only a single metasurface. This advancement substantially broadens the potential of metasurface-based spin photonics, extending its applications from the spatial domain to the spatiotemporal domain.

Beating spectral bandwidth limits for large aperture broadband nano-optics

Flat optics have been proposed as an attractive approach for the implementation of new imaging and sensing modalities to replace and augment refractive optics. However, chromatic aberrations impose fundamental limitations on diffractive flat optics. As such, true broadband high-quality imaging has thus far been out of reach for fast f-numbers, large aperture, flat optics. In this work, we overcome intrinsic spectral bandwidth limitations, achieving broadband imaging in the visible wavelength range with a flat meta-optic, co-designed with computational reconstruction. We derive the necessary conditions for a broadband, 1 cm aperture, f/2 flat optic, with a diagonal field of view of 30° and average system MTF contrast of 20% or larger for a spatial frequency of 100 lp/mm in the visible band (>30% for <70 lp/mm). Finally, we use a coaxial, dual-aperture system to train the broadband imaging meta-optic with a learned reconstruction method operating on pair-wise captured imaging data. Fundamentally, our work challenges the entrenched belief of the inability of capturing high-quality, full-color images using a single large aperture meta-optic.

High-efficiency rectangular transverse air-gap metalens for visible light based on a dual-coupled PB phase

Pancharatnam-Berry (PB) phase modulation leverages the precise linear correspondence between output phase and nanopillar rotation angle, enabling wide application in modulating focal spherical waves. However, the intrinsic material absorption of waveguide structure inevitably brings energy loss within the visible light spectral range, severely limiting focusing efficiency over broad bandwidths under general models of nanopillars. Here, we introduce a dual-coupled metalens composed of an air slot-etched rectangular TiO2 nanopillar, and the extremely narrow air gap along its long axis of nanopillar can be regarded as a high-aspect-ratio rectangular waveguide for strictly confining the incident light. In the visible spectrum of 440∼670 nm, the optical performance of the dual-coupled metalens is tested at the numerical apertures (NAs) of 0.35, 0.44, 0.6, and 0.82. Simulation results indicate that the structure not only meets the basic requirements of PB phase control, but also exhibits ultra-low loss and ultrahigh focusing efficiency. The novel, to the best of our knowledge, structure proposed in this work provides new design inspiration for general phase modulations and efficient micro-optical devices including wide-spectral metalens.

High-performance achromatic flat lens by multiplexing meta-atoms on a stepwise phase dispersion compensation layer

Flat optics have attracted interest for decades due to their flexibility in manipulating optical wave properties, which allows the miniaturization of bulky optical assemblies into integrated planar components. Recent advances in achromatic flat lenses have shown promising applications in various fields. However, it is a significant challenge for achromatic flat lenses with a high numerical aperture to simultaneously achieve broad bandwidth and expand the aperture sizes. Here, we present the zone division multiplex of the meta-atoms on a stepwise phase dispersion compensation (SPDC) layer to address the above challenge. In principle, the aperture size can be freely enlarged by increasing the optical thickness difference between the central and marginal zones of the SPDC layer, without the limit of the achromatic bandwidth. The SPDC layer also serves as the substrate, making the device thinner. Two achromatic flat lenses of 500 nm thickness with a bandwidth of 650-1000 nm are experimentally achieved: one with a numerical aperture of 0.9 and a radius of 20.1 µm, and another with a numerical aperture of 0.7 and a radius of 30.0 µm. To the best of our knowledge, they are the broadband achromatic flat lenses with highest numerical apertures, the largest aperture sizes and thinnest thickness reported so far. Microscopic imaging with a 1.10 µm resolution has also been demonstrated by white light illumination, surpassing any previously reported resolution attained by achromatic metalenses and multi-level diffractive lenses. These unprecedented performances mark a substantial step toward practical applications of flat lenses.

Binary phase-only gallium oxide diffractive optical element for beam shaping

This study presents an experimentally validated demonstration of an inverse-optimized binary phase-only gallium oxide diffractive optical element (DOE). This DOE transforms an incident Gaussian beam into a square flat-top beam at the working plane. The design methodology for this binary phase-only DOE beam shaper is founded on an efficient process that integrates the modified Gerchberg-Saxton algorithm and the adjoint method. Experimental characterization of the fabricated device on a single crystal [Formula: see text]gallium oxide substrate is conducted at a wavelength of 532 nm, confirming its ability to transform an incident Gaussian beam into a focused square flat-top beam. Such a device holds significant promise for various high-power laser applications, notably in laser welding and similar domains. Furthermore, because of the ultrawide bandgap of gallium oxide, DOEs operating at shorter wavelengths in the UV are also possible based on this technique.

Optical Fresnel zone plate flat lenses made entirely of colored photoresist through an i-line stepper

Light manipulation and control are essential in various contemporary technologies, and as these technologies evolve, the demand for miniaturized optical components increases. Planar-lens technologies, such as metasurfaces and diffractive optical elements, have gained attention in recent years for their potential to dramatically reduce the thickness of traditional refractive optical systems. However, their fabrication, particularly for visible wavelengths, involves complex and costly processes, such as high-resolution lithography and dry-etching, which has limited their availability. In this study, we present a simplified method for fabricating visible Fresnel zone plate (FZP) planar lenses, a type of diffractive optical element, using an i-line stepper and a special photoresist (color resist) that only necessitates coating, exposure, and development, eliminating the need for etching or other post-processing steps. We fabricated visible FZP lens patterns using conventional photolithography equipment on 8-inch silica glass wafers, and demonstrated focusing of 550 nm light to a diameter of 1.1 μm with a focusing efficiency of 7.2%. Numerical simulations showed excellent agreement with experimental results, confirming the high precision and designability of our method. Our lenses were also able to image objects with features down to 1.1 μm, showcasing their potential for practical applications in imaging. Our method is a cost-effective, simple, and scalable solution for mass production of planar lenses and other optical components operating in the visible region. It enables the development of advanced, miniaturized optical systems to meet modern technology demand, making it a valuable contribution to optical component manufacturing.

Portable astronomical observation system based on large-aperture concentric-ring metalens

The core advantage of metalenses over traditional bulky lenses lies in their thin volume and lightweight. Nevertheless, as the application scenarios of metalenses extend to the macro-scale optical imaging field, a contradiction arises between the increasing demand for large-aperture metalenses and the synchronous rise in design and processing costs. In response to the application requirements of metalens with diameter reaching the order of 104λ or even 105λ, this paper proposes a novel design method for fixed-height concentric-ring metalenses, wherein, under the constraints of the processing technology, a subwavelength 2D building unit library is constructed based on different topological structures, and the overall cross-section of the metalens is assembled. Compared to global structural optimization, this approach reduces computational resources and time consumption by several orders of magnitude while maintaining nearly identical focusing efficiency. As a result, a concentric-ring metalens with a designed wavelength of 632.8 nm and a diameter of 46.8 mm was developed, and a quasi-telecentric telescope system composed of aperture stop and metalens was constructed, achieving high-resolution detection within a 20° field of view. In the subsequent experiments, the unique weak polarization dependence and narrowband adaptability of the meta-camera are quantitatively analyzed and tested, and excellent imaging results were finally obtained. Our work not only ensures the narrowband optical performance but also promotes the simplicity and light weight of the metalens based telescopic system, which further advances the deep application of large-diameter metalenses in the field of astronomical observation.

Achromatic metalenses for full visible spectrum with extended group delay control via dispersion-matched layers

Achieving achromaticity across the visible light spectrum is crucial for metalenses in imaging systems. Single-layer metalenses struggle with weak focusing power or small aperture sizes due to inadequate group delay control. Multilayer metalenses offer some improvement but come with increased design and fabrication complexity. Here, we demonstrate a strategy using meta-atoms with material layers engineered for matching dispersion, allowing large and fine adjustments of group delay. Our design substantially broadens the group delay range, allowing us to experimentally demonstrate several polarization-independent metalenses operating across the entire visible spectrum (400-700 nm). We design, fabricate, and characterize achromatic metalenses with aperture diameters of 16 μm, 66 μm, 200 μm, and 400 μm, and numerical apertures of 0.27, 0.11, 0.04, and 0.02, respectively. Among them, the 400-μm diameter, 0.02-numerical-aperture metalens is used to demonstrate full-color imaging capabilities. Our results exhibit diffraction-limited performance, high efficiency, and accurate full-color image reproduction.

Infrared color-sorting metasurfaces

The process of sorting light based on colors (photon energy) is a prerequisite in broadband optical systems, typically achieved in the form of guiding incoming signals through a sequence of spectral filters. The assembly of filters often leads to lengthy optical trains and consequently, large system footprints. In this work, we address this issue by proposing a flat color-sorting device comprising a diffraction grating and a dielectric Huygens' metasurface. Upon the incidence of a broadband beam, the grating disperses wavelengths to a continuous range of angles in accordance with the law of diffraction. The following metasurface with multiple paired Huygens' resonances corrects the dispersion and binds wavelengths to the corresponding waveband with a designated output angle. We demonstrate the sorting efficacy by designing a device with a color-sorting metasurface with two discrete dispersion-compensated outputs (10.8 ± 0.3 μm and 11.9 ± 0.3 μm), based on the proposed approach. The optimized metasurface possesses an overall transmittance exceeding 57% and reduces lateral dispersion by 90% at the output. The proposed color-sorting mechanism provides a solution that benefits the designing of metasurfaces for miniature multi-band systems.

Upper limit on the polarization-assisted amplitude modulation capability of cascaded single-cell wave-plate-like metasurfaces

The Jones matrix method offers a robust framework for designing polarization multiplexed metasurfaces (PMMs). Traditional PMMs design involves initially defining functions and working channels, then mapping feature functions to adjustable parameters of metasurfaces. However, this approach makes it difficult to predict how working channels affect metasurface features. Here, we employ the generalized Malus law and Rodriguez rotation matrix on the Poincare Sphere to analyze diverse working channels' impact on PMMs' amplitude modulation capacity. For single-celled waveplate-like PMMs, up to three distinct images can be displayed. We demonstrate this in both theoretic method and numerical simulations. Our study establishes a framework for multi-channel amplitude modulation design of metasurfaces, applicable in information encryption, optical computation, diffraction neural networks, etc.

Hybrid design scheme for enabling large-aperture diffractive achromat imaging

Diffractive achromats (DAs) combined with image processing algorithms offer a promising lens solution for high-performance ultra-thin imagers. However, the design of large-aperture DAs that align seamlessly with image processing algorithms remains challenging. Existing sequential methods, which prioritize focusing efficiency in DAs before selecting an algorithm, may not achieve a satisfactory match due to an ambiguous relationship between efficiency and final imaging quality. Conversely, image-quality-oriented end-to-end design often entails high computational complexity for both front-end optics and back-end algorithms, impeding the development of large-aperture designs. To address these issues, we present a hybrid design scheme that begins with end-to-end optimization of the DA with the simplest image processing algorithm, i.e., Wiener filter, significantly reducing the back-end complexity. Subsequently, we apply complex algorithm fine-tuning to further enhance image quality. We validate this hybrid design scheme through extensive investigations on several DA imagers. Our results demonstrate a reduction in memory requirement by approximately 50% while maintaining a high imaging quality with a reasonably large aperture. As a case in point, we simulated a DA imager with a 25 mm diameter aperture. Furthermore, our hybrid design scheme provides two crucial insights. Firstly, we find no strong linear correlation between focusing efficiency and imaging quality, which challenges the conventional understanding. Secondly, we establish a prediction formula for imaging quality, benefiting from the hybrid design scheme.

Optical trapping and manipulating with a transmissive and polarization-insensitive metalens

Trapping and manipulating micro-objects and achieving high-precision measurements of tiny forces and displacements are of paramount importance in both physical and biological research. While conventional optical tweezers rely on tightly focused beams generated by bulky microscope systems, the emergence of flat lenses, particularly metalenses, has revolutionized miniature optical tweezers applications. In contrast to traditional objectives, the metalenses can be seamlessly integrated into sample chambers, facilitating flat-optics-based light manipulation. In this study, we propose an experimentally realized transmissive and polarization-insensitive water-immersion metalens, constructed using adaptive nano-antennas. This metalens boasts an ultra-high numerical aperture of 1.28 and achieves a remarkable focusing efficiency of approximately 50 % at a wavelength of 532 nm. Employing this metalens, we successfully demonstrate stable optical trapping, achieving lateral trapping stiffness exceeding 500 pN/(μm W). This stiffness magnitude aligns with that of conventional objectives and surpasses the performance of previously reported flat lenses. Furthermore, our bead steering experiment showcases a lateral manipulation range exceeding 2 μm, including a region of around 0.5 μm exhibiting minimal changes in stiffness for smoothly optical manipulation. We believe that this metalens paves the way for flat-optics-based optical tweezers, simplifying and enhancing optical trapping and manipulation processes, attributing ease of use, reliability, high performance, and compatibility with prevalent optical tweezers applications, including single-molecule and single-cell experiments.

Design of achromatic diffractive lenses

Diffractive lenses can be very thin and light. They usually suffer from chromatic aberration and work only over a narrow range of wavelengths but so-called achromatic diffractive lenses have recently attracted attention. Ways in which the profile of such lenses can be chosen to optimize either the Strehl ratio or the efficiency are compared and the extent to which the performance of the resulting lens designs approaches theoretical limits is investigated. Simple rules are given for the average Strehl ratio and efficiency expected in certain conditions. In other cases they provide approximate guidelines. Some reported simulated and measured efficiencies greatly exceed those that appear credible. This is attributed to failure to take into account radiation scattered to large off-axis angles or to inadequate sampling of the radial profile.

An Improved 3D OPC Method for the Fabrication of High-Fidelity Micro Fresnel Lenses

Based on three-dimensional optical proximity correction (3D OPC), recent advancements in 3D lithography have enabled the high-fidelity customization of 3D micro-optical elements. However, the micron-to-millimeter-scale structures represented by the Fresnel lens design bring more stringent requirements for 3D OPC, which poses significant challenges to the accuracy of models and the efficiency of algorithms. Thus, a lithographic model based on optical imaging and photochemical reaction curves is developed in this paper, and a subdomain division method with a statistics principle is proposed to improve the efficiency and accuracy of 3D OPC. Both the simulation and the experimental results show the superiority of the proposed 3D OPC method in the fabrication of Fresnel lenses. The computation memory requirements of the 3D OPC are reduced to below 1%, and the profile error of the fabricated Fresnel lens is reduced 79.98%. Applying the Fresnel lenses to an imaging system, the average peak signal to noise ratio (PSNR) of the image is increased by 18.92%, and the average contrast of the image is enhanced by 36%. We believe that the proposed 3D OPC method can be extended to the fabrication of vision-correcting ophthalmological lenses.

Dielectric Metasurface Enabled Compact, Single-Shot Digital Holography for Quantitative Phase Imaging

Quantitative phase imaging (QPI) enables nondestructive, real-time, label-free imaging of transparent specimens and can reveal information about their fundamental properties such as cell size and morphology, mass density, particle dynamics, and cellular fluctuations. Development of high-performance and low-cost quantitative phase imaging systems is thus required in many fields, including on-site biomedical imaging and industrial inspection. Here, we propose an ultracompact, highly stable interferometer based on a single-layer dielectric metasurface for common path off-axis digital holography and experimentally demonstrate quantitative phase imaging. The interferometric imaging system leveraging an ultrathin multifunctional metasurface captures image plane holograms in a single shot and provides quantitative phase information on the test samples for extraction of its physical properties. With the benefits of planar engineering and high integrability, the proposed metasurface-based method establishes a stable miniaturized QPI system for reliable and cost-effective point-of-care devices, live cell imaging, 3D topography, and edge detection for optical computing.

Theory and Fundamental Limit of Quasiachromatic Metalens by Phase Delay Extension

The periodic extension of phase difference is commonly applied in device design to obtain phase compensation beyond the system's original phase modulation capabilities. Based on this extension approach, we propose the application of quasiphase delay matching to extend the range of dispersion compensation for meta-atoms with limited height. Our theory expands the limit of frequency bandwidth coverage and relaxes the constraints of aperture, NA, and bandwidth for metalenses. By applying the uncertainty principle, we explain the fundamental limit of this achromatic bandwidth and obtain the achromatic spectrum using perturbation analysis. To demonstrate the effectiveness of this extended limit, we simulate a quasiachromatic metalens with a diameter of 2 mm and a NA of 0.55 in the range of 400-1500 nm. Our findings provide a novel theory for correcting chromatic aberration in large-diameter ultrawide bandwidth devices.

3D nanoprinting for fiber-integrated achromatic diffractive lens

Achromatic performance is crucial for numerous multi-wavelength optical fiber applications, including endoscopic imaging and fiber sensing. This paper presents the design and nanoprinting of a fiber-integrated achromatic diffractive lens within the visible spectrum (450-650 nm). The 3D nanoprinting is achieved by a high-resolution direct laser writing technology, overcoming limitations in the optical performance caused by the lack of an arbitrary 3D structure writing capability and an insufficient feature resolution in the current manufacturing technology for visible light broadband achromatic diffractive lenses. A three-step optimization algorithm is proposed to effectively balance optical performance with writing difficulty. The characterization results demonstrate excellent achromatic focusing performance, paving the way towards the development of nanoprinted flat optical devices for applications such as optical fiber traps, miniature illumination systems, and integrated photonic chips.

Deep learning enhanced achromatic imaging with a singlet flat lens

Correction of chromatic aberration is an important issue in color imaging and display. However, realizing broadband achromatic imaging by a singlet lens with high comprehensive performance still remains challenging, though many achromatic flat lenses have been reported recently. Here, we propose a deep-learning-enhanced singlet planar imaging system, implemented by a 3 mm-diameter achromatic flat lens, to achieve relatively high-quality achromatic imaging in the visible. By utilizing a multi-scale convolutional neural network (CNN) imposed to an achromatic multi-level diffractive lens (AMDL), the white light imaging qualities are significantly improved in both indoor and outdoor scenarios. Our experiments are fulfilled via a large paired imaging dataset with respect to a 3 mm-diameter AMDL, which guaranteed with achromatism in a broad wavelength range (400-1100 nm) but a relative low efficiency (∼45%). After our CNN enhancement, the imaging qualities are improved by ∼2 dB, showing competitive achromatic and high-quality imaging with a singlet lens for practical applications.

Fabricable concentric-ring metalens with high focusing efficiency based on two-dimensional subwavelength unit splicing

To address the challenges posed by computational resource consumption and data volume in the development of large-aperture metalenses, a design method for concentric-ring metalens based on two-dimensional unit splicing is proposed in this paper. In the method, the unit structure library is constructed through global traversal under the machining process constraints. The phase matching is performed for two polarization states with specific weights and the design of binary-height, concentric-ring structures with arbitrary polarization sensitivity is realized, whose focusing efficiency (the encircled power within 3×FWHM of the focal spot divided by the near-field outgoing power) is up to 90%. Based on this method, a polarization-insensitive metalens with a design wavelength of 10µm, diameter of 2 cm, and numerical aperture of 0.447 is obtained. The method combines the advantages of lower computation requirements for a building block array of a metalens and lower structure data for a concentric-ring metalens. Consequently, it becomes possible to reduce calculation and processing costs by several orders of magnitude during the development process of metalenses with diameters ranging from 103 to 105 wavelengths. The resulting focusing efficiency can approach the upper limit achievable through global structural optimization and significantly surpass that of binary-height Fresnel lenses.

Multifocal multilevel diffractive lens by wavelength multiplexing

Flat lenses with focal length tunability can enable the development of highly integrated imaging systems. This work explores machine learning to inverse design a multifocal multilevel diffractive lens (MMDL) by wavelength multiplexing. The MMDL output is multiplexed in three color channels, red (650 nm), green (550 nm), and blue (450 nm), to achieve varied focal lengths of 4 mm, 20 mm, and 40 mm at these three color channels, respectively. The focal lengths of the MMDL scale significantly with the wavelength in contrast to conventional diffractive lenses. The MMDL consists of concentric rings with equal widths and varied heights. The machine learning method is utilized to optimize the height of each concentric ring to obtain the desired phase distribution so as to achieve varied focal lengths multiplexed by wavelengths. The designed MMDL is fabricated through a direct-write laser lithography system with gray-scale exposure. The demonstrated singlet lens is miniature and polarization insensitive, and thus can potentially be applied in integrated optical imaging systems to achieve zooming functions.

Design of achromatic hybrid metalens with secondary spectrum correction

Metasurface can be used in combination with singlet refractive lens to eliminate chromaticity, in which the metasurface usually works as a dispersion compensator. Such a kind of hybrid lens, however, usually has residual dispersion due to the limit of meta unit library. Here, we demonstrate a design method that considers the refraction element and metasurface together as a whole to achieve large scale achromatic hybrid lens with no residual dispersion. The tradeoff between the meta-unit library and the characteristics of resulting hybrid lenses is also discussed in detail. As a proof of concept, a centimeter scale achromatic hybrid lens is realized, which shows significant advantages over refractive lenses and hybrid lenses designed by previous methods. Our strategy would provide guidance for designing high-performance macroscopic achromatic metalenses.

Recent advanced applications of metasurfaces in multi-dimensions

Unlike traditional optical components, which rely on the gradual accumulation of light along the optical path over a distance much larger than the wavelength to form a wavefront, metasurfaces manipulate light field properties on the wavelength thickness by specially arranging various meta-atoms. Due to the ease of integration and compact planar structure, metasurfaces play a key role in the light field manipulations. Here, we review the recent advances of metasurfaces in multi-dimensions, including light wavelength, polarization, orbital angular momentum(OAM), and angular response. Progress in these fields has brought new applications in areas such as imaging, display, communication, and information encryption, etc. Finally, we also discuss the challenges and prospects of metasurfaces applications.

Design of a centimeter-scale achromatic hybrid metalens with polarization insensitivity in the visible

Achromatic metalenses formed using previous design methods face a compromise between diameter, numerical aperture, and working wave band. To address this problem, the authors coat the refractive lens with a dispersive metasurface and numerically demonstrate a centimeter-scale hybrid metalens for the visible band of 440-700 nm. By revisiting the generalized Snell law, a universal design of a chromatic aberration correction metasurface is proposed for a plano-convex lens with arbitrary surface curvatures. A highly precise semi-vector method is also presented for large-scale metasurface simulation. Benefiting from this, the reported hybrid metalens is carefully evaluated and exhibits 81% chromatic aberration suppression, polarization insensitivity, and broadband imaging capacity.

Advance of large-area achromatic flat lenses

A new framework of light coherence optimization is proposed to design non-ideal broadband achromatic lenses, enabling large-scale flat lenses' implementation and high performance. The strategy paves the way for practical planar optical devices and full-color imaging systems.

Phase-assisted angular-multiplexing nanoprinting based on the Jacobi-Anger expansion

Featuring with ultracompactness and subwavelength resolution, metasurface-assisted nanoprinting has been widely researched as an optical device for image display. It also provides a platform for information multiplexing, and a series of multiplexed works based on incident polarizations, operating wavelengths and observation angles have emerged. However, the angular-multiplexing nanoprinting is realized at the cost of image resolution reduction or the increase of fabrication difficulty, hindering its practical applications. Here, inspired by the Jacobi-Anger expansion, a phase-assisted design paradigm, called Bessel metasurface, was proposed for angular multiplexing nanoprinting. By elaborately designing the phase distribution of the Bessel metasurface, the target images can be encoded into the desired observation angles, reaching angular multiplexing. With the merits of ultracompactness and easy fabrication, we believe that our design strategy would be attractive in the real-world applications, including optical information storage, encryption/concealment, multifunctional switchable optical devices, and 3D stereoscopic displays, etc.