Two‐Photon Grayscale Lithography (2GL) of High Mechanical and Optical Quality 3D Silica Glass Microstructures

ABSTRACT Two‐photon grayscale lithography (2GL) is the latest evolution in two‐photon polymerization laser 3D printing, combining unmatched surface quality and throughput by continuous laser power modulation that dynamically controls the print feature size (voxel) to smoothly blend contours despite coarse slicing. To reconstruct shapes, 2GL solves an inverse problem requiring parametrization of the voxel size and their underlying print parameters, which is specific to a given feedstock resist and so far, only available for a few commercial polymers. This paper establishes a 2GL 3D‐printing route for the rapid manufacturing of complex silica glass micro‐ and nanostructures of unprecedented quality and accuracy, substantially advancing glass micro‐fabrication. This is enabled by a pre‐glass polyhedral oligomeric silsesquioxane (POSS) resist, engineered for high polymerization sensitivity and dynamic range. Together with a routine to identify optimal grayscale parameters for such custom resists, we realize the use of the 2GL process at maximal print speed while maintaining high loading of the silicon‐oxygen POSS‐cluster source. Mechanical resonators with quality factors > 1 000, optical components with < 3 nm roughness and nanoscale diffractive patterns are demonstrated, opening new pathways in photonics, precision mechanics, and metamaterials. The introduced grayscale parameter identification routine provides a framework for extending 2GL‐printing to a broader material range.