Enthalpy Relaxation Mediated Control of NIR Emission in Bi‐Doped Glass

Abstract Bi‐doped materials exhibit significant potential in optical fiber communications, biomedical imaging, and therapeutic applications owing to their tunable broadband near‐infrared (NIR) luminescence. However, precise control of the NIR emission feature remains a persistent challenge for Bi‐doped materials. This study introduces an enthalpy relaxation‐mediated strategy to tune and optimize the optical characteristics of Bi‐doped glasses. By thermally triggered structural relaxation, the compactness of glass networks can be precisely controlled, enabling tailorable optical properties and enhanced luminescence stability. Guided by this mechanism, Bi‐doped optical fibers with tunable amplified spontaneous emission (ASE) have been successfully fabricated. Additionally, NIR light‐emitting diode (LED) with superior thermal stability and radiation‐resistant X‐ray imaging system have been developed, facilitating advancements in high‐resolution NIR and X‐ray imaging technologies. These findings not only validate the enthalpy relaxation‐mediated strategy for optimizing optical performance but also highlight the broad application prospects of Bi‐doped materials in optical communications and imaging technologies.