Metasurfaces enable the design of optical elements by engineering the wavefront of light at the subwavelength scale. Due to their ultrathin and compact characteristics, metasurfaces possess great potential to integrate multiple functions in optoelectronic systems for optical device miniaturisation. However, current research based on multiplexing in the 2D plane has not fully utilised the capabilities of metasurfaces for multi-tasking applications. Here, we demonstrate a 3D-integrated metasurface device by stacking a hologram metasurface on a monolithic Fabry–Pérot cavity-based colour filter microarray to simultaneously achieve low-crosstalk, polarisation-independent, high-efficiency, full-colour holography, and microprint. The dual functions of the device outline a novel scheme for data recording, security encryption, colour displays, and information processing. Our 3D integration concept can be extended to achieve multi-tasking flat optical systems by including a variety of functional metasurface layers, such as polarizers, metalenses, and others.

The past few decades have witnessed growing research interest in developing powerful nanofabrication technologies for three-dimensional (3D) structures and devices to achieve nano-scale and nano-precision manufacturing.

This study demonstrates a full‐color printing concept based on the interference effect in pixelized metal–dielectric–metal Fabry–Perot (FP) resonance cavities. The pixel color for printing is determined by the thickness of the dielectric layer in each microscale FP cavity. Abundant colors with controllable brightness and saturation are achieved by varying both the thickness and the filling density of the FP cavities using grayscale lithography. Enabled by the wide color gamut, a vivid full‐color image can be reproduced at the microscopic scale with high resolution by correlating the colors with the dimensional parameters of the FP cavities through a layout‐generation algorithm. The colorization strategy based on interference effects provides a new opportunity to use artificial structures for color printing and also has the potential to be scaled up for large‐volume application in consumable products using replica patterning techniques such as grayscale photolithography, nanoimprinting, and soft lithography.

many irreplaceable advantages of high storage capacity, miniaturization, multi plicity, and integration capability. [6][7][8][9][10][11] Among various microoptics/nano optics devices, metasurface, consisting of planar subwavelength structures, has emerged as a particularly powerful plat form for modulating light parameters such as amplitude, [12,13] phase, [14][15][16] wavelength, [17][18][19][20] polarization, [4,[21][22][23] and hybrid parameters, [24,25] which provides the possibility of potential applications of information encryption, data storage, and optical communication. [26][27][28] Microprint and holography are often used as two separate optical encryption strategies applied in independent meta surface devices, which can be achieved by controlling over plasmonic [29][30][31][32][33][34] or all dielectric [35][36][37][38][39][40] structures at the nanoscale. To strengthen optical information secu rity, other parametric freedoms such as polarization, [41][42][43][44][45] wavelength, [17,[46][47][48][49] and spatial freedom [50][51][52] have been explored to achieve multiplexed microprint or holography encryption devices. Very recently, attempts have been imple mented to combine the microprint and holography in a single device. [53][54][55] However, although the combination of holography and microprints brings about the increase of encrypted dimen sions, crosstalk between different channels remains a thorny problem, and devices will not transmit repeatedly between senders and receivers once fabricated. Fabry-Pérot (FP) cavity resonators with narrow spectral linewidth can effectively sup press crosstalk and can be integrated to act as color filters, [56,57] which provides a potential solution. However, significant chal lenges such as realtime encryption, transmission security, and data compactness still need to be overcome.Here, we propose a novel type of metasurfacebased device that combines color FP cavitybased microprint and helicity multiplexed metahologram. Such devices have the encryption dimensions of microprint, holography as well as helicity at the same time by independently manipulating the amplitude, phase, and polarization of the incident light. A specific algo rithmic framework is developed to combine holography with structural color, and the particle swarm optimization (PSO) algorithm is built to optimize the conversion efficiencies of metasurface elements. Furthermore, enabled by a microprint of editable quick response (QR) code, a realtime encryption Optical encryption with multichannel, high complexity, and artistry characteristics has become one of the most significant approaches for modern information security. Recently emerged metasurface-based optics consisting of planar subwavelength metamaterials has been engineered as an ideal platform for optical encryption because of its capability of manipulating various optical parameters and enhancing information storage capacity. However, limited encrypted channels and insufficient real-time encryption abilities hinder its practical applicatio...

COMMUNICATIONDue to its advantage and promising applications, many recent studies have been focused on the design of F-P cavities-based spectral fi lters. [ 35,36 ] For example, Aydin and coworkers proposed a perfect absorber comprised of planar Ag/SiO 2 /Ag cavity with a maximum absorption intensity of ≈97% and a narrow bandwidth of ≈17 nm. [ 37 ] Furthermore, the location of the absorption peak is tunable in the visible light range just by controlling the dielectric spacer thickness. Yang et al. obtained three primary RGB (red, green, and blue) refl ective colors with a low sensitivity to the incidence angle by fabricating asymmetrical resonant cavities comprised of an a-Si dielectric fi lm sandwiched by a thin chromium (Cr) layer and a thick silver (Ag) layer. [ 38 ] In their structure, Cr is adopted as the absorptive layer to absorb the incident light and the RGB fi lters are achieved by adjusting the thickness of the constituent layers. However, it is noteworthy that the purity and brightness of the existing proposed color fi lters to date are not suffi ciently high due to the narrow absorption peak and the relatively low refl ectivity in the wavelength range of the color we are interested in.In this work, F-P cavities-based refl ective color fi lters consisting of a layer of thin nickel (Ni) fi lm and a thick aluminum (Al) fi lm, separated by a silicon dioxide (SiO 2 ) dielectric layer, are demonstrated. We use a thin nickel (Ni) layer as a broadband absorber to obtain abundant structural colors with high saturation and brightness operating at visible range. Combined with grayscale patterning techniques, we also demonstrated that high-resolution, high-contrast monolithic color printing could be achieved enabled by this refl ective color-fi lter confi guration.The schematic confi guration of the proposed refl ective color fi lter is shown in Figure 1 a. It is an asymmetric F-P type resonator comprised of Ni/SiO 2 /Al triple-layer fi lm stacks, in which the refl ectivity of Ni and Al is very different. Ni was chosen to be the top metal because of its relatively uniform and appropriate refl ectivity and absorption in the entire visible light range which is essential to achieve broadband absorption for purer and brighter refl ective colors, as indicated by the simulated refl ectance and transmittance spectra in Figure 1 b. Al was adopted as a highly refl ective mirror at the bottom. SiO 2 is a lossless dielectric material in the visible range, which was used as the spacer layer, and its optical thickness d determines the position of the absorption and refl ectance peaks. Comparing to other designs using Ag as absorber and mirror, both Ni and Al in the confi guration have better adhesion property with SiO 2 and are also inexpensive for practical applications.Metal-based refl ective color fi lters, which display various colors by selectively refl ecting a specifi c wavelength in the visible region, have attracted tremendous interest in recent years as a crucial component for diverse applications, such as optical ...