High-efficiency phase modulation in LCoS-compatible LC-metasurface via spacer integration and Oseen-Frank modeling

A liquid crystal (LC)-tunable metasurface offers a promising route to extend the functionality of liquid crystal on silicon (LCoS) spatial light modulators (SLM) by enabling fast phase control and potential polarization insensitivity. However, prior approaches face two major challenges: absorption losses from indium tin oxide (ITO) electrodes on the coverplate and simplistic modeling of LC reorientations. This work presents an LC-metasurface positioned on the coverplate, with a silicon dioxide (SiO₂) spacer layer introduced to suppress ITO-induced damping. The LC was modeled using the Oseen-Frank framework, incorporating anchoring boundary conditions to capture realistic LC alignment. The fabricated device achieved phase modulation depth >2π between 1590-1615 nm with reflectance exceeding 60%, providing an experimentally validated phase-only modulation solution for a LC-tunable metasurface compatible with commercial LCoS backplanes.