Ultra‐Broadband Emission in Bi/Ge Co‐Doped Silica Glass and Fiber via Bismuth Coordination Engineering

Abstract Bismuth (Bi) and Germanium (Ge) co‐doped silica glass and fiber, as advanced gain media with broadband near‐infrared (NIR) emission and amplification, have promise for extending communication bandwidth. However, efficiently modulating the NIR emissions of bismuth to cover the C+L communication bands remain a significant challenge. In the study, a high‐temperature and high‐pressure reduction treatment on Bi/Ge co‐doped silica glass is employed to tailor the coordination environment around bismuth active center. This method facilitated the creation of new bismuth NIR luminescence centers, resulting in the luminescence spectrum with a peak position at 1550 nm and a FWHM exceeding 350 nm. The changes in the bismuth coordination environment are elucidated using HRTEM, photoluminescence decay, temperature‐dependent emission, EXAFS and CW‐EPR. Furthermore, the feasibility of this method in Bi/Ge co‐doped silica fiber is validated, and obtained >5 dB amplification in the range of 1400–1700 nm. This coordination engineering method holds significant potential for widespread application in Bi/Ge co‐doped silica glass and optical fiber is believed. It presents a promising prospect for expanding communication bandwidth by effectively modulating the NIR emissions of bismuth to cover the S to U communication band.