Grayscale Multiple Exposure Method of Digital Projection Lithography for High‐Fidelity Fabrication of Dense Metasurface in Infrared Region

ABSTRACT Digital projection lithography based on digital micromirror device (DMD) provides mask‐free patterning, rapid reconfiguration, and high‐throughput fabrication, making it an efficient option for producing complex and nonperiodic metasurface layouts. However, the diffraction of micromirror arrays and the limited pixel pitch fundamentally constrain its achievable resolution, leading to strong optical proximity effects and pattern distortion when defining the dense, tightly spaced meta‐atoms required for functional metasurfaces operating at optical and infrared wavelengths. Here, we present a grayscale multiple‐exposure digital projection lithography method that overcomes these limitations and enables high‐fidelity fabrication of dense metasurfaces. By decomposing complex layouts into sparse sub‐patterns and applying sequential exposures with pixel‐level grayscale dose modulation, the method effectively suppresses interference between adjacent features and achieves continuous tuning of nanopillar diameters with sub‐pixel precision. Using this strategy, we fabricate silicon metasurfaces for extended depth‐of‐focus focusing and vortex‐beam generation in the mid‐infrared (3–5 µm) regime. The measured focal‐line extension, vortex‐beam ring profile, and overall optical field distributions agree closely with numerical simulations, validating the accuracy of both phase discretization and fabrication. This scalable and cost‐efficient workflow provides a practical solution for high‐resolution, multi‐level metasurface fabrication in the infrared region.