Printable Bifocal Microlenses from Ferroelectric Nematic Liquid Crystal Droplets

Multifocal lenses are essential for enhancing stereoscopic image display and increasing the depth of field in optical devices. Traditional liquid crystal lenses face challenges in achieving planar alignment at both interfaces, which limits their use for multifocal lenses. Here, we demonstrate printable bifocal microlens arrays formed by submillimeter plano-convex droplets of ferroelectric nematic liquid crystals deposited on rubbed polymer-coated glass substrates, promoting uniform planar alignment. These droplets exhibit two polarization-dependent focal lengths, corresponding to the extraordinary and ordinary refractive indices of the material. Computer simulations corroborate the observed director structures and optical behaviors across the nematic, antiferroelectric smectic, and ferroelectric nematic phases. Our findings reveal a straightforward method for self-assembled bifocal lenses, offering potential applications in autostereoscopic displays and devices requiring an enhanced depth of field without complex fabrication processes.