First Tellurite Composite Fiber with NIR‐Driven Green Persistent Luminescence

Abstract Expanding the excitation range of persistent luminescent (PeL) materials into the near infrared (NIR) region is critical to enable remote, flexible, and compact advanced optical systems. In this study, the fabrication of the first composite fiber based on SrAl ₂ O ₄ :Eu ²⁺ , Dy ³⁺ phosphors embedded in Yb ³⁺ /Tm ³⁺ co‐doped tellurite glass is reported. The fiber is drawn from a translucent, crack‐free composite preform prepared with 0.5 wt.% PeL phosphors. Light propagation in the fiber is demonstrated despite the presence of the PeL phosphors. Long‐lasting green emission from the preform and fiber is driven by 980 nm and suggests the survival of the PeL phosphors during the preform preparation and fiber drawing processes. The presence of the PeL phosphors in the glass matrix is confirmed using SEM/EDS composition analysis. This work offers a practical and scalable approach for integrating NIR‐excitable PeL materials into fiber‐based platforms, opening new opportunities for their application in advanced photonic technologies.