Broadband L+ near-infrared luminescence in bismuth/germanium co-doped silica glass prepared by the sol–gel method

Abstract

Bismuth (Bi) and germanium (Ge) co-doped silica glass and fiber, as novel amplification media, have attracted extensive attention due to their L+ near-infrared (NIR) luminescence to broaden the communication band. However, the underlying mechanism of bismuth NIR luminescence remains elusive, which poses a constraint on the development of Bi/Ge co-doped silica glass and fiber. In this study, Bi/Ge co-doped silica glass was prepared by a sol–gel method and the influence of Ge and Bi doping concentrations on luminescence properties was systematically investigated. Through an analysis of the glass network structure, a direct correlation between bismuth near-infrared active luminescence centers (BAC) for L+ band emission and the germanium oxygen vacancy defects (Ge-ODC) was found. The formation mechanism of BAC-Ge was proposed. This paper provides insights into bismuth NIR luminescence behavior, especially in the L+ band and serves as a valuable reference for the precise design of bismuth-doped silica fiber for L+ band amplifying applications.