Ambient‐Light‐Activated Rewritable Optical Patterning in Transparent Long‐Afterglow Garnet Ceramics

ABSTRACT Reversible optical patterning under ambient conditions remains a formidable challenge due to the stringent requirements for high transparency, robust re‐writability, and efficient excitation by ubiquitous light sources. Herein, we demonstrate sunlight‐activated rewritable optical information storage in transparent long‐afterglow Y 3 Al 2 Ga 3 O 12 :Ce (YAGG:Ce) garnet ceramics fabricated via solid‐state sintering with tetraethyl orthosilicate (TEOS) as a sintering aid. Through systematic optimization of TEOS concentration (0.6–1.2 wt.%), we achieve precise control over porosity and oxygen‐vacancy traps. The optimally processed ceramic (0.8 wt.% TEOS) exhibits an exceptional combination of properties, enabling high‐contrast optical pattern writing using a simple white‐light flashlight or direct sunlight. The stored patterns can be retained over extended periods, consistent with the long afterglow behavior, and can be rapidly erased over multiple cycles without observable fatigue. Furthermore, we introduce a thermally stimulated reading modality based on trap depth analysis (with the shallowest trap depth of ∼0.90 eV estimated by the initial rise method considering the quantum tunneling effect, and the dominant trap depth of ∼1.15 eV estimated from the thermoluminescence peak at 575 K), where faded information can be effectively recovered by mild heating at 60°C. By integrating ambient light operability, reversibility, and high optical clarity in a robust ceramic host, this work establishes a new paradigm for sustainable, high‐resolution, and dynamic photonic storage and display platforms.