Multimodal Stimuli‐Responsive Luminescence and Photochromism of Cr ³⁺ ‐Doped Gallate β‐Alumina

Abstract Smart optical materials responsive to thermal, mechanical, and optical stimuli hold significant potential across diverse fields, including optics, sensing, data storage, and information encryption. However, integrating multi‐stimuli‐responsiveness into a single platform remains challenging. Here, a smart material is designed through Cr 3+ doping into defect‐tolerant gallate β‐alumina. This material demonstrates invisible near‐infrared (NIR) short‐lived photoluminescence (PL), super long‐lasting NIR persistent luminescence (PersL, over 144 h), repeatable NIR mechanoluminescence (ML), and ultrafast photochromism (within 2 s). The material also exhibits multimodal responsiveness to X‐ray, UV, visible, NIR light, and thermal disturbance, enabling precise spatiotemporal control of optical properties for applications in bio‐mechanical monitoring, bio‐imaging, information storage, and anti‐counterfeiting technology. A flexible film is engineered incorporating as‐synthesized smart material, demonstrating capabilities in bio‐stress monitoring, encryption, and six‐mode anti‐counterfeiting applications. Additionally, NIR bio‐imaging application further highlights its potential in biomedicine. These findings provide valuable insights into the design of highly integrated, multi‐stimuli‐responsive smart optical materials and devices, particularly for applications in biomedical and information encryption.