Ce-regulated redox-defect coupling for high-contrast photochromism in Bi-based glass toward rewritable multimodal optical storage and encryption

The rapid growth of artificial intelligence is driving demand for secure and rewritable optical information technologies. Bi-based photochromic glasses are promising, yet achieving high optical contrast, stable rewritability, and controllable formation of low-valence Bi species remains challenging. Here, Ce partially replaces Sb to regulate the multivalent redox environment, while Eu 3+ provides luminescent readout. The optimized glass containing 0.2 mol% CeO 2 exhibits a coloration contrast of 24.85% within 30 s, 4.3 times that of the Ce-free glass, and reaches 70.86% after 130 s of 465 nm irradiation. It exhibits a relative transmittance recovery of 99.66% after heating at 300 °C for 5 min and retains 98% of its coloration contrast after 50 writing–bleaching cycles. Photochromism-induced optical attenuation enables a reversible Eu 3+ emission modulation of 84.78% in the optimized glass. Combined X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and high-resolution transmission electron microscopy (HRTEM) analyses indicate that Ce substitution regulates charge redistribution among Bi/Sb/Ce redox centers and oxygen-related localized states, facilitating reversible Bi 3+ reduction and the photoinduced formation of low-valence Bi-related nanoclusters. The coupled coloration and luminescence responses enable rewritable pattern recording, dual-mode optical verification, and matrix-based information encoding and reconstruction, providing an integrated Bi-based glass medium for multimodal optical storage and encryption.