Surface Alignment of Liquid Crystal Films on Nanometer-Thick 3D-Printed Line Patterns with Arbitrary Topologies: Implications for Polarization Gratings, Q‑Plates, and Beam Steerers

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