Fig. 1. The schematic diagram illustrates typical fabrication techniques for all-dielectric metasurfaces, categorized into four parts. The first part encompasses standard nanolithography (NL) methods, specifically EBL, FIB lithography, and laser-based nanomanufacturing. The second part shows advanced NL techniques, such as grayscale lithography and scanning probe lithography (SPL). The third part explores mass manufacturing technologies, including molecular self-assembly, DUV lithography, and nanoimprint lithography. The fourth part delves into extreme nanofabrication techniques tailored for high-aspect-ratio, slanted, flexible, and multilayer nanostructures, respectively.

Fig. 2. Comparison of the optical properties of different dielectric materials and their high-efficiency applications across the UV to IR spectrum.

Fig. 3. The illustration clarifies the pattern transfer through the lithography process. Following the exposure of the resist film to a specific radiation source (such as photons, electrons, or ions), the intended pattern is transferred to the resist film through the developer. Subsequently, the pattern is transposed onto the dielectric materials, encompassing two cases. In the first case, the pattern is transferred through etching techniques; after the etching process, the final step involves stripping the resist through chemical or physical methods. In the second case, the dielectric material is deposited into the exposed and developed areas, followed by the lift-off process.

Fig. 4. The utilization of EBL in the fabrication of all-dielectric metasurfaces. (a) The schematic depicts the fabrication process of silicon-based structural color utilizing EBL.^[28] Initially, a PMMA resist film is spin-coated onto the silicon-coated sapphire substrate. Subsequently, the resist is exposed to an electron beam and developed to form PMMA nanostructures. The sample is then transferred to an E-beam evaporator and coated directly with Cr films. After a lift-off process involving immersion in acetone, the PMMA is removed, and the nanostructures are effectively transferred to Cr. The silicon is later etched away using reactive ion etching with CHF3 and SF6 gases. Finally, Si metasurfaces are obtained by immersing the sample in chromium etchant. (b) The top-view SEM image of silicon nanodisks for color printing. The diameters and periods of these three colors are 170/320, 90/200, and 160/300 nm, respectively. The scale bar is 500 nm.^[28] (c) The top-view SEM image displays the C-shaped silicon nanoantenna from nonlinear holographic all-dielectric metasurfaces. The insets include zoomed-in images showing high-resolution side-view SEM images.^[22] (d) The SEM image with a tilted view of 45° presents the fabricated silicon rectangle pillars used for tunable full-color vectorial meta-holography.^[150] (e) Fabrication process of high-efficiency TiO2 metasurfaces^[67]: (I) Application of the resist on fused silica. (II) Recording of the reversed metasurface pattern into the resist using EBL. (III) Deposition of TiO2 through atomic layer deposition (ALD) into the exposed substrate. (IV) Formation of the final thick TiO2 film, exceeding half the width of the maximum feature size after ALD. (V) Removal of residual TiO2 and resist via reactive ion etching with a mixture of Cl2 and BCl3 ions. (VI) Completion of the final metasurface after eliminating remaining resist. (f) The top and side-view SEM image of fabricated ALD-based TiO2 metalenses at visible wavelengths (scale bar, 300 nm)^[15]. (g) The fabrication process (left) of the TiO2 metasurface with lift-off technology^[30]: Top: Patterning of the photoresist with EBL. Middle: Formation of TiO2 film through electron-beam evaporation technology. Bottom: Elimination of the photoresist through lift-off. Corresponding SEM image (right) of one metasurface (scale bar, 500 nm). (h) Tilt view SEM images of the etched TiO2 nanostructures, including circular pillars, crosses, rectangle pillars, crosses, and rectangle pillars.^[101] (i) Fabrication flow of the GaN-based structures for a broadband achromatic metalens in the visible spectra.^[12] (j) SEM image of the on-axis focusing GaN-based metalens, applied in CMOS image sensor.^[151]

Fig. 5. The utilization of focused ion beam lithography in the fabrication of all-dielectric metasurfaces. (a) FIB gallium ion milling in a Gaussian profile for the direct fabrication of subwavelength nanoholes on silicon through scanning, enabling multicolor generation. The SEM image (right) displays the nanohole, with the corresponding enlarged cross-sectional view as an inset. SEM images (bottom) of color filter arrays, with the right corner in each image showing the cross-section SEM obtained by FIB cutting.^[165] (b) Chiral visible light metasurface patterned in monocrystalline silicon on sapphire using FIB. The SEM image on the left includes FIB paths and directions (curved arrows), and the inset is a tilted SEM image. The right image presents a 3D model of a unit cell.^[166] (c) All-dielectric phase-change reconfigurable metasurface consisting of a period grating fabricated by FIB milling in an amorphous Ge2Sb2Te5 (GST) film on silica. The SEM images depict tilt and cross-sectional views, shown on the left and bottom, respectively.^[167] (d) Schematic of the ZnO metasurface (top) for coherent vacuum ultraviolet light generation. Titled SEM image (bottom) of the FIB milled metasurface with scale bar of 300 nm.^[168] (e) The SEM image of a section of a silicon membrane nano-cantilever array from nanomechanically reconfigurable all-dielectric metasurfaces for sub-GHz optical modulation.^[169] (f) The process involves the stepwise fabrication of a dielectric slab waveguide photonic crystal, as illustrated on the left. On the right, SEM images provide both a top view and a cross-sectional view of dielectric structures fabricated using FIB milling lithography.^[170] (g) Side and top-view SEM images of self-rolled multilayer metasurfaces.^[171] (h) The 3D Archimedean spiral chiral metasurface milled by the gallium FIB and tilted SEM (right) images of the freestanding Au/Si3N4 bilayer film.^[172]

Fig. 6. The utilization of LIL in the fabrication of all-dielectric metasurfaces. (a) Schematic representation (top row) of the interference setup with two, three, four, and six overlapping beams, along with the corresponding light intensity patterns (bottom row)^[198]. (b) Top-view SEM of polarization-independent two-dimensional diffraction metal–dielectric grating.^[199] (c) SEM image (left) of the silicon nanohole array pattern on SOI substrate and the appearance (right) of large-area printed broadband membrane reflectors by LIL. The inset shows the enlarged SEM image.^[200] (d) Mie-resonant silicon-based metasurfaces via single-pulse LIL: Schematic (left) illustrating the four-beam interference setup and the resulting intensity distribution. Mechanism of silicon transformation (middle) utilizing the interference intensity pattern. Top view (right) SEM images of nanoholes (intermediate state, a-Si) and nanoparticles (Mie resonator state, p-Si) patterned from the Si film, respectively. Scale bar = 1 µm.^[93] (e) Metasurface-generated complex 3D optical fields for LIL: Concept (left) of a metamask generating specific diffraction orders to create a desired 3D pattern in the photoresist. Optical image (middle) of the fabricated optimized diamond metamask. Simulated and measured cross-sections (right) of the captured 3D intensity pattern under 514 nm laser illumination.^[201]

Fig. 7. The utilization of LDW in the fabrication of all-dielectric metasurfaces. (a) The patterned pulse LDW approach for creating sub-wavelength features. The schematic illustration (top) shows the pulse LDW system, and the SEM image of fabricated H-shaped arrays with sub-wavelength feature size is visible. Scale bars=5μm. Fabrication flow (bottom) of structures by etching after pulse LDW (Cr used as masks on fused silica substrate), along with SEM images of the H shapes.^[205] (b) The fabrication process of Ge2Sb2Te5 metasurfaces by LDW. The schematic on the left illustrates the laser casting process of a GST film through LDW. The AFM image in the middle showcases the fabricated metasurface with a square array, while the SEM images on the right depict the metasurface on glass and sapphire substrates, respectively.^[206] (c) THz optical pattern recognition enabled by a complex amplitude modulating metasurface through LDW: Schematic (left) of the fabrication of laser-induced graphene C-shaped antennas by LDW with different orientations and angles. Optical and SEM image (right) of the fabricated metasurface.^[207] (d) Polarization-directed growth of spiral nanostructures by LDW with vector beams: Illustration of optical setup (left). Simulated beam profile with different vectors and SEM images of the chiral patterns formed with different vector beams (right).^[208]

Fig. 8. The utilization of two-photon lithography in the fabrication of all-dielectric metasurfaces. (a) Dielectric metasurfaces in the optical diffraction with a fine structure: SEM images of fabricated dielectric particle/inverted counterpart structures and corresponding optical diffraction patterns.^[209] (b) SEM images of the device for controlling 3D optical fields via inverse Mie scattering.^[210] (c) SEM images of an inverse-designed near-infrared polarization beam splitter fabricated by two-photon LDW.^[211] (d) SEM image of a two-photon LDW-printed hologram on the single-mode fiber facet (scale bar is 20 µm).^[214] (e) Realization of a helix-based perfect absorber for IR spectral range using two-photon LDW: Fabrication process (left) of dielectric templates. Zoom-in SEM image (right) of a single-turn metallic helix.^[216] (f) Inverse design and 3D printing of a metalens on an optical fiber tip for two-photon LDW: SEM image (left) of the fabricated metalens on top of the fiber. Schematic of the homebuilt two-photon polymerization setup (right). The inset shows the SEM image of the pattern “NU” produced by the metalens using the homemade setup.^[215]

Fig. 9. The utilization of grayscale lithography in the fabrication of all-dielectric metasurfaces. (a) Grayscale lithography enables the creation of height-gradient-tunable nanostructure arrays, as illustrated in the schematic (top). This method utilizes grayscale EBL, ALD, and a transfer process for assembling nano-configurations with varying heights. The bottom row displays typical SEM images of TiO2 nanopillars with height variations, showcasing the structural color metasurface after implementing height regulation.^[233] (b) FIB grayscale lithography facilitates color printing using Mie voids in a silicon substrate. The top part illustrates conically shaped voids with varying diameters and depths in a bulk silicon wafer. In the middle, optical microscope and SEM images showcase selected sizes and depths of Mie voids. The bottom section presents an optical microscope image of the color-printed image.^[234] (c) Two-photon grayscale LDW is employed for 3D-printed low-index nanopillars, as outlined in the schematic of the fabrication process (left). The right side features a tilted view SEM of the 3D printed colorful painting, revealing pillars with varying heights, diameters, and periodicities.^[236] (d) Custom multispectral filter arrays are fabricated using EBL and laser grayscale lithography. The left section demonstrates a dose-modulated pixel array by EBL, displaying the dose-modulated pattern, optical micrograph, and corresponding AFM data. The middle part outlines the fabrication flow of photolithography-based multispectral filter arrays using a binary photomask. The right side presents an optical micrograph (transmission) of a different region of the wafer, with a labeled equivalent exposure pattern (inset).^[237]

Fig. 10. The utilization of multistep lithography in the fabrication of all-dielectric metasurfaces. (a) A versatile metasurface with self-cleaning and dynamic color response, fabricated through EBL and laser lithography: Two super wettability states switchable with hydrophobic treatment or O2 hydrophilic treatment (left).^[238] Illustration of the multistep fabrication process for the sample (right). (b) Schematic of the fabrication process for the synthetic aperture metalens using EBL and photolithography.^[221] (c) Hybrid metal–dielectric metasurfaces: Stepwise fabrication process of stacked hybrid nanoantenna metasurfaces (left). SEM images of the fabricated metasurfaces (right).^[222]

Fig. 11. The utilization of scanning probe lithography in the fabrication of all-dielectric metasurfaces. (a) SPL for imaging and patterning applications.^[239] (b) Nanopatterning achieved through combined thermal SPL and dry etching, along with corresponding SEM images of silicon fabrication using a SiO2 hard mask.^[240] (c) Fabrication of a tunable metasurface based on VO2 using electric-field SPL with precise depth control: Topography image of square patterns modulated by different tip bias voltages and followed by sonication. The scale bar is 2 µm (left). Schematic representation of the main steps in fabricating the designed metasurface (right).^[241]

Fig. 12. The utilization of UV lithography in the fabrication of all-dielectric metasurfaces. (a) The schematic diagram illustrates the production of large-area metalenses utilizing photolithographic stepper technology. An accompanying photograph of the fabricated metalens (upper right) showcases a 2 cm diameter. A SEM image of the metalens center (center right) reveals the nanocylinder constituting the metalens. Scale bar: 2 µm.^[267] (b) The fabrication process of wafer-scale membrane-based metasurfaces for mid-infrared photonics and biosensing. In the top right photograph, a fully processed 4 in. silicon wafer is depicted, showcasing large-area metasurfaces. The bottom right provides a high-magnification SEM image of the metasurface unit cell, revealing the thin Al2O3 membrane in blue and the Ge resonators in orange.^[269] (c) The left image illustrates the fabrication process of an all-glass, large metalens at visible wavelengths utilizing DUV projection lithography. On the right, zoomed-in SEM images showcase the nanopillars of the metalens, while a photograph displays the fabricated 1 cm metalenses on a 4 in. SiO2 wafer.^[268] (d) Photograph of the 12 in. silicon metasurface wafer, meticulously fabricated through the Multiple-Projects Wafer (MPW) line at Microelectronics IME for the production of polarizing bandpass filters. A detailed examination of the wafer center is presented in the zoomed-in view (left). Additionally, a tilted SEM image and a cross-sectional TEM image showcase a single silicon pyramid with intricate details (right).^[270] (e) Image of a metasurface-based subtractive color filter crafted on a 12 in. glass wafer through a CMOS platform. In the top-right section, there are photo images of the central die subsequent to wafer dicing. The bottom-right segment illustrates the schematic of the fabrication process for layer transfer onto the glass wafer.^{[100, 271]} (f) The left column depicts CMOS-compatible a-Si metalenses on a 12 in. glass wafer designed for fingerprint imaging, with the central circled region on the wafer highlighting the metalens. The right column showcases SEM images captured at both the central and outer zones of the metalens.^[272] (g) The fabrication process of an all-glass 100-mm-diameter visible metalens for imaging the cosmos is depicted in the top panel. The bottom-left section features a photograph of the metalens, providing a size comparison with a table tennis racket, along with a SEM image showcasing the fused silica nanopillars constituting the metalens. In the bottom-right section, a photograph of the astro-imager is presented, consisting solely of a 100-mm-diameter metalens, an exchangeable optical filter, and a cooled CMOS monochromatic sensor. Additionally, an acquired image of the Moon is displayed.^[136]

Fig. 13. The utilization of nanoimprint lithography in the fabrication of all-dielectric metasurfaces. (a) The fabrication process of an all-dielectric heterogeneous metasurface, designed as an efficient ultra-broadband reflector, is depicted on the left. The cross-sectional SEM image on the right provides a detailed view of the fabricated metasurface.^[279] (b) Schematic representation of the fabrication process for silicon nanostructures with adjustable geometries through soft nanoimprint lithography and reactive ion etching (left). The initial imprinted SU8 nanostructure is presented in the first column before etching. The second column displays the results after well-controlled etching times, showcasing the tunable meta-atom geometries (right).^[280] (c) Single-step manufacturing of hierarchical dielectric metalenses in the visible. SEM images depict the master mold, soft mold, and final plum pudding metalens, respectively. Scale bars: 1 µm. Scale bars of inset optical micrographs: 100 µm.^[281] (d) The TiO2 nano-PER metahologram is fabricated through a one-step process of nanoparticle-embedded-resin printing. The initial row showcases the SEM image of the master mold meticulously crafted using EBL on a silicon substrate. The subsequent image displays the intricate final structure of the printed TiO2 nano-PER. In the second row, the successful replication of the TiO2 nano-PER metahologram is exhibited on diverse substrates, including flexible polycarbonate (PC) and ultrathin polypropylene (PP). Scale bars: 1 µm.^[126] (e) Illustration depicting the achievement of high-aspect-ratio metalenses through nanoimprint lithography utilizing water-soluble stamps (left). SEM images showcasing the replicated metalens (right).^[282] (f) Schematic illustration depicting the fabrication of a metalens through multilayer nanoimprint lithography and solution phase epitaxy. The inset images on the right showcase SEM images of the ZnO metalens.^[283]

Fig. 14. The utilization of self-assembly in the fabrication of all-dielectric metasurfaces. (a) Illustration of the primary fabrication steps for the flexible, all-dielectric metasurface utilizing nanosphere lithography. The accompanying images on the right showcase SEM images of self-assembled polystyrene (PS) spheres (top) and Si cylinders (bottom) formed after RIE. Scale bars: 1 µm.^[285] (b) Illustration of the self-assembly-based nanosphere lithography technique for the large-scale fabrication of all-dielectric metasurface perfect reflectors, accompanied by a camera image depicting the pattern of PS spheres on an SOI substrate (left column). SEM images showcase PS spheres with a diameter initially at 820 nm and subsequently downscaled to 560 nm after etching (middle column). The top and tilted views exhibit the final metamaterial, comprising an array of Si cylinders. Scale bar: 2 µm.^[98] (c) Image of large-scale metasurfaces created through grayscale nanosphere lithography. A grayscale pattern is produced by the DMD system utilizing a 365 nm I-line UV light source, transmitted through a projection system incorporating an objective lens. The schematic depicts the air–water interface for nanosphere self-assembly, while the SEM image showcases the close-packed nanosphere monolayer after self-assembly, with a scale bar of 5 µm. Additionally, an optical image of the fabricated metalens is presented. Scale bar: 200 µm.^[232] (d) The left panel illustrates the schematic, while the right panel displays the SEM image of the self-assembly process of nanostructured glass metasurfaces through templated fluid instabilities. The fabrication initiates with thermal or ultraviolet nanoimprinting of the requisite pattern on a substrate, as shown in the top section (scale bar, 400 nm). Subsequently, a thin-film deposition of high-index optical glass is performed in the middle section (scale bar, 1 µm). The final step involves annealing to induce the dewetting process, depicted in the bottom section (scale bar, 1 µm). A schematic of the dewetting process is also provided. An optical photograph showcases a large area (20cm×11cm) EPFL logo-shaped metasurface on a polymer substrate, with an inset SEM image revealing the corresponding nanostructure (scale bar, 1 µm).^[286]

Fig. 15. Multilayer dielectric metasurface nanofabrication. (a) A depiction of the sequential steps involved in the fabrication of bilayer chiral silicon metasurfaces. The right image provides a perspective and an oblique-view SEM representation of the accomplished chiral metasurfaces.^[303] (b) Bilayer metasurfaces for comprehensive light manipulation involve a meticulous fabrication process, as illustrated on the left. The SEM image on the right depicts the a-Si nanobrick array and the Ag nanobrick array, showcasing the intricate details. Scale bars: 1 µm.^[103] (c) The fabrication process of multilayer non-interacting dielectric metasurfaces for multiwavelength meta-optics is depicted on the left. The inset displays an optical microscope image of the alignment marks from the two layers. Scale bar: 30 µm. An SEM image of silicon nano-posts before PDMS spin coating is presented on the right. Scale bar: 300 nm.^[307] (d) The hybrid achromatic metalens, composed of a phase plate and nanopillar, is designed for broadband, near-infrared imaging and fabricated using two-photon lithography.^[304] (e) Multilayer achromatic metalenses (MAMs) with high numerical aperture produced through 3D printing. The left image presents a tilted view of the fabricated multilayer achromatic metalenses, showcasing deconstructed MAMs with single, double, and triple (full) layers. The right SEM image offers an enlarged view of the full MAM and sectioned MAM.^[305] (f) Inverse-designed multilayered metaoptics using 3D printing, implemented in a low-index polymer. The SEM of the measured sample is displayed in the right panel.^[306]

Fig. 16. Flexible dielectric metasurface nanofabrication. (a) Stretchable all-dielectric metasurfaces with polarization-insensitive and full-spectrum response are depicted in this study. The sample fabrication process is schematically illustrated on the left. The middle graphic portrays the conceptual image of the stretchable TiO2 metasurface. The SEM images of the TiO2 metasurface after the lift-off and transfer are provided as insets on the right. Scale bar: 1 µm. The reflection spectra as a function of strain. The insets show corresponding dynamic colors.^[308] (b) The fabrication of highly tunable elastic dielectric metasurface lenses involves several key steps, as depicted in the schematic on the left. SEM images on the right provide a detailed view of the nano-posts before spin coating the initial PDMS layer and after they are embedded in PDMS.^[309] (c) Decoupling the optical function from the geometrical form is achieved through conformal flexible dielectric metasurfaces. The schematic depicts a dielectric metasurface layer conforming to the surface of a transparent object with arbitrary geometry. The side view illustrates a thin dielectric metasurface layer altering its optical response to a desired one (middle). Optical images showcase two flexible metasurfaces conformed to a convex glass cylinder and a concave glass cylinder (right). Scale bar, 2 mm.^[102] (d) The schematic on the left illustrates the nanoimprint procedure of dielectric metasurfaces with sub-100-nm resolution. On the right, the replication of the metasurface onto a flexible substrate.^[253] (e) Flexible, all-dielectric metasurface fabricated via nanosphere lithography.^[285]

Fig. 17. Slanted dielectric metasurface nanofabrication. (a) Detection of intrinsic chiral bound states in the continuum (BICs). Schematic representation of the slant-perturbation metasurface designed to achieve intrinsic chiral BICs. Side-view (left) and cross-sectional (right) SEM images showcasing the fabricated metasurface. Scale bar: 300 nm. Reflection spectra measurements for two metasurface samples under LCP and RCP incidence, respectively (top right). Comparison of CDs and Q-factors between some typical experimental works and this work (right bottom).^[84] (b) The illustration presents slanted TiO2 metagratings designed for large-angle, high-efficiency anomalous refraction in the visible spectrum. The top left depicts the schematic of the slanted TiO2 metagrating. In the top right, side-view SEM images showcase TiO2 gratings with varying etching angles. The bottom section displays the improved TiO2 metagrating, with SEM images depicting the structure before and after the re-deposition of the SiO2/TiO2 bilayer on the left. The right-bottom section provides experimentally recorded angle-dependent power distributions passing through the metagrating before (open squares) and after (dots) the redeposition.^[104]

Fig. 18. High-aspect-ratio dielectric metasurface nanofabrication. (a) The diagram illustrates the fabrication process of a high-efficiency broadband achromatic metalens designed for near-infrared biological imaging. A highly directional etching process is employed to create TiO2 nanostructures. The bottom-left images showcase SEM images of the achromatic metalens with varying resolutions, while the images on the right depict the focusing efficiencies of the developed TiO2 metalenses.^[101] (b) The nanoimprint lithography process is employed in the manufacturing of high-aspect-ratio TiO2 meta-atoms.^[310] (c) A high-aspect-ratio inverse-designed holey metalens is depicted in the image. The top section displays an SEM image on the side I of the holey metalens. In the middle, cross-sectional SEM images offer a detailed view of a holey metalens. The bottom section outlines the fabrication workflow employed for the production of holey metalenses.^[311] (d) Bifunctional manipulation is achieved through high-aspect-ratio dielectric metasurfaces. High-quality tri-layer meta-atoms with high aspect ratios (as shown in the inset) are produced using the Bosch process. The achievement of a high-aspect-ratio etch is only viable under these balanced conditions (depicted on the left). The top-view and bottom-view SEM images illustrate the fabricated metasurface (right).^[312]

Fig. 19. Advanced applications, such as imaging^{[12, 313–315" target="_self" style="display: inline;">–315]}, display^{[26, 28]}, analog computing^{[316, 317]}, metrology^{[43, 318–320" target="_self" style="display: inline;">–320]}, communications^{[321–323" target="_self" style="display: inline;">–323]}, and light sources^{[17, 133]} utilizing dielectric meta-devices, have emerged in the past years.

Fig. 20. Prospects for the bright future of all-dielectric metadevices/optics with wafer-scale mass fabrication, including (i) metalenses, (ii) AR and VR, (iii) optical sensors, (iv) color/holographic displays, (v) AI-based spectrometer/advanced imaging, (vi) telekinesis and telepathy, and (vii) satellite communications/LIDAR.