Light-Controlled Polarization Volume Grating via Liquid Crystal Elastomer Actuation

Abstract

Tunable optical elements are fundamental to modern photonics, yet conventional tuning approaches rely on rigid components and electronic control, limiting their integration into flexible, lightweight, or remotely operated systems. This work presents a light-controlled optomechanical polarization volume grating (PVG) achieved by monolithically integrating a liquid crystal polymer (LCP) diffraction grating onto a photoactive, azo-dye-doped liquid crystal elastomer (LCE) substrate. The LCE exhibits reversible, anisotropic photomechanical deformation under 450-nm illumination, reaching approximately 10% strain. The LCP PVG, engineered for the green spectral region (~550 nm), demonstrates a first-order diffraction efficiency of 92%. Upon integration, light-induced LCE deformation mechanically modulates the grating period, yielding reversible, bidirectional spectral tuning: redshift for parallel alignment and blueshift for perpendicular alignment, with the tuning direction selectable through initial alignment design. This wireless, all-optical device establishes a proof-of-concept for soft, light-driven adaptive optics, with pathways toward enhanced performance through material optimization and applications in compact optical systems, LiDAR, and augmented reality displays.