Response Time Improvement of Liquid Crystal Reflectarray Using Chiral Dopant With Polar Group

In this letter, a response-time-improvement method for liquid crystal reflectarrays (LCRAs) is proposed by doping a small amount of chiral molecules with a polar group into nematic liquid crystals (NLCs). The dopant introduces additional intermolecular interactions that accelerate molecular relaxation and thus shorten the decay time, while an overdrive (OD) voltage is applied to mitigate the rise-time increase. LC cells with various chiral-dopant concentrations are characterized, where it is found that the concentration of 0.5 wt% yields the shortest effective decay time. An LCRA prototype using this concentration was fabricated and measured, achieving a significantly reduced decay time, while the rise time is effectively shortened by the OD technique. This work represents the first investigation of chiral-dopant effects on both rise and decay times within a reflectarray configuration, providing guidance for high-speed chiral LCRA design.