Synergistic Dual‐Excitation‐Induced Reversible Photochromism and Luminescence Modulation in BaTiO 3 Nanocrystal‐Embedded Glass

Photochromic glasses have attracted increasing interest for photonic information storage and optical modulation because of their transparency and reversible color switching. However, most reported photochromic systems are predominantly governed by either valence‐state conversion or defect‐mediated carrier trapping, while simultaneously coupling both processes to achieve strong reversible coloration in a transparent glass ceramic for multifunctional photonic applications remains challenging. Here, we report a transparent BaTiO 3 nanocrystal‐embedded glass that exhibits reversible photochromism under both 365 nm light and x‐ray irradiation, attributed to Ti 3 + formation and oxygen‐vacancy‐related trap states. The resulting broad absorption enables pronounced modulation of Eu 3 + emission, with attenuation contrasts of 49.5% under 365 nm stimulation and 85.1% under x ‐ray irradiation. The photochromic states can be efficiently erased by thermal treatment or 532 nm laser illumination, allowing reversible and repeatable optical switching. Additionally, the intrinsic radioluminescence of Eu 3 + provides an integrated optical response that couples photochromism, luminescence modulation, and x‐ray sensitivity within a single transparent glass platform, enabling proof‐of‐concept demonstrations of reversible all‐optical information storage and dual‐mode x‐ray imaging. This work establishes nanocrystal‐embedded photochromic glass as a promising transparent photonic platform for multifunctional optical and radiation‐responsive applications.