Spatial Homeotropic and Planar Liquid Crystal Alignment Patterning

Liquid crystals (LCs) require precise alignment for advanced photonic applications, with photoalignment offering a powerful route for complex spatial patterning. While recent studies demonstrate that Brilliant Yellow (BY) photoalignment layers can induce out‐of‐plane (homeotropic) anchoring via a two‐step illumination process, these approaches typically necessitate thick BY films that limit device transparency. In this work, we present an optimized two‐step laser illumination technique utilizing a spatial light modulator (SLM) and local exposure to circularly polarized laser light to precisely pattern alternating planar and homeotropic domains. Crucially, we introduce the application of an AC electric field across the LC layer during the second illumination step. This field reorients the LC, strongly minimizing the phase retardation of the propagating laser beam and significantly reducing the required exposure dose to induce homeotropic alignment. Utilizing this technique, we relax the need for thick films, successfully demonstrating versatile micro‐patterns–such as gratings and checkerboards–using a highly transparent alignment layer. Furthermore, we demonstrate that this approach enables improved in‐plane rewritability of the planar aligned regions. Ultimately, this methodology provides a highly controllable and transparent platform for developing next‐generation spatially patterned LC devices.