Light‐Reconfigurable Three‐Dimensional Liquid–Crystalline Photonic Crystals Enabling Continuous Ultrabroadband Spectral Tunability

Three‐dimensional (3D) photonic crystals (PhCs) enable advanced light manipulation across quantum and nonlinear optics, electronics, nanomaterials, and bionics. However, their practical applications are hindered by their limited tunability and complex fabrication processes. Blue phases (BPs), which can self‐assemble into 3D PhCs with nanoscale periodicity, offer a promising pathway toward reconfigurable photonic materials. Herein, we present a light‐tunable BP platform with a lattice structure that can be continuously and reversibly modulated, achieving a photonic bandgap shift greater than 400 nm that spans the visible to near‐infrared regions without band hopping. This continuous tunability is enabled by photosensitive chiral molecular motors, which undergo photoisomerization and racemization, reducing effective helical twisting power and inducing symmetric lattice expansion. Weak‐light driving minimizes heat generation and suppresses unwanted phase transitions, thereby maintaining structural stability within a single BP. Spatially and temporally programmable 3D superstructures are realized by controlling illumination intensity and employing photolithographic patterning. Our scalable, versatile, and environmentally friendly platform paves the way for next‐generation adaptive photonic devices, including tunable filters, optical switches, modulators, and integrated photonic systems.