Phototunable Polarization Volume Gratings Driven by Chiral Hydrazone Switches

ABSTRACT Polarization volume gratings (PVGs) have gained significant attention in recent years because of their potential use as diffraction couplers in augmented reality technologies. In most cases, PVGs have either fixed optical properties or they are tunable with electric fields. Light‐responsive strategies have been constrained by the shortcomings of azobenzene‐based dopants, including moderate thermal stability of the E / Z isomer ratio and increased visible‐light absorption upon UV irradiation (positive photochromism). In this work, we introduce negatively photochromic, chiral hydrazone photoswitches into PVGs, enabling light‐driven reversible modulation of their optical properties. We show that external irradiation with UV and blue light induces reversible changes in the isomer ratio, resulting in corresponding modulation of the diffraction efficiency and spectral response of the gratings within the visible range. These findings highlight the potential for dynamically tunable optical components, offering pathways toward versatile and energy‐efficient photonic devices.