Configurational Entropy Engineering of Bi‑Doped Glass Fiber Enabling Ultrabroadband Emission

Bismuth (Bi)-doped silica, the most promising candidate for the L-band and beyond, is fundamentally hindered by the thermodynamic aggregation of inactive bismuth ions. These ions form detrimental atomic clusters that act as quenching centers, inducing high unsaturable loss (UL).

Here, a configurational entropy engineering is reported to overcome this limitation in Bi-doped silica fiber. Distinct from compositional high-entropy alloys, this approach utilizes kinetic manipulation to trap the glass network in a high-energy, disordered configurational state. This effectively suppresses the growth of element aggregation domains, preventing energy dissipation from the bismuth active center.