Cost-effective photolithography-based dual liquid crystal alignment for versatile electro-optic applications

Abstract

Nematic liquid crystals (NLCs) containing rod-shaped molecules exhibit remarkable birefringence and tunability. Therefore, they are of high interest for numerous electro-optic applications. Uniform molecular orientation is of utmost importance for their effective use. Current techniques for LC alignment, such as mechanical rubbing or photo-alignment, have limitations in creating specifically complex LC orientation patterns. To address this issue, we have developed a cost-effective photolithography-based technique for dual LC alignment which combines planar and vertical alignments. Our process involves inexpensive exposure systems and a lift-off process and employs commercially-available alignment materials, thereby reducing production costs. We utilized this process to generate a tunable phase grating with diffraction efficiencies which can be varied through voltage application, thus demonstrating the potential of dual alignment. Furthermore, we investigated smart windows that are insensitive to polarization, utilizing a two-dimensional grating structure, achieving high haze values and dynamic shading without relying on incident polarization.