Surface Alignment\nof Liquid Crystal Films on Nanometer-Thick\n3D-Printed Line Patterns with Arbitrary Topologies: Implications for\nPolarization Gratings, Q‑Plates, and Beam Steerers

Liquid crystal films play a key role in advancing next-generation\noptical and photonic devices that require a precise in-plane modulation\nof optical anisotropy. This study employs multiphoton direct laser\nwriting, a high-resolution three-dimensional (3D) printing method,\nto fabricate pseudoperiodic patterns of lines and grooves on glass\nsurfaces for the in-plane alignment of liquid crystal films. Single\nlayers of lines with submicron thickness and line spacing were fabricated\nin less than half an hour and forced the in-plane alignment of a liquid\ncrystal film with a thickness of about 10 μm. We validate the\nmethod on patterns with singular topologies designed to induce the\nnucleation of disclination defects with a predetermined spatial arrangement,\norientation, and topological strength. Compared to other surface patterning\nmethods, high-resolution 3D printing provides the unique advantage\nof direct surface fabrication, enabling the creation of nonflat geometries\nsuch as terraces and lenses and expanding the design and functionalities\nof liquid crystal devices. We anticipate that this method will be\nused to create thin-film devices such as polarization gratings, beam\nsteerers, and q-plates for manipulating polarized and structured light.