Direct laser engineering of silver nanostructures in zinc–phosphate glass for enhanced Nd ³⁺ photoluminescence

Abstract Femtosecond direct laser writing (DLW) was employed to control the formation of silver nanostructures in ZnO–P 2 O 5 glass co‐doped with Ag + and Nd 3+ ions, aiming to establish the relationship between local structure, processing parameters, and optical functionality. By varying the writing speed between 1 and 10 µm/s, the silver species evolved from sub‐nanometer nanoclusters to small (≤2 nm) nanoparticles. Ag K‐edge X‐ray absorption fine structure (XAFS) analysis revealed the coexistence of Ag + –O complexes and metallic Ag atoms, quantifying the structural transformation induced by DLW. The microstructural evolution was correlated with pronounced photoluminescence (PL) enhancement of Nd 3+ ions: tracks written at 2–4 µm/s exhibited up to a 24‐fold increase in PL intensity at 875 nm. This enhancement originated from local electric‐field amplification and energy transfer processes mediated by the laser‐induced Ag nanostructures. The relative contributions of Ag nanoclusters and nanoparticles to the observed plasmon‐assisted PL were analyzed. These results demonstrate DLW as a powerful tool for spatially engineering and studying structure–property relationships in rare‐earth‐doped glass systems with embedded plasmonic nanostructures.