Fluorine passivation of ODC defects in amorphous germanium dioxide

•The interaction of atomic fluorine with GODC in α-GeO2 results in the formation of Ge-F-Ge and GE′ center.•The GODC defects in α-GeO2 prefer to be passivated by the molecular fluorine.•The addition of fluorine decreases the optical absorption, refractive index and the electron energy loss of the fully passivated configurations in the near-ultraviolet region.•The presence of the fluorine decreases the dangling bonds, which have been predict usefulness of fluorine passivation. We present first-principle calculations on the interaction of atomic and molecular fluorine with germanium oxygen-deficient center (GODC) in amorphous germanium dioxide (a-GeO2). The interaction of atomic fluorine with GODC in a-GeO2 results in the formation of Ge-F-Ge and GE′ center. The reaction pathways and the energy barriers have been investigated to understand the formation of the fully passivated configurations which are obtained by the interaction of molecular fluorine with GODC in a-GeO2. Our results indicate that the GODC defects prefer to be passivated by the molecular fluorine. It is found that in the near-ultraviolet region, the optical absorption of the fully passivated configurations is significantly reduced by doping of fluorine. These results help to better understand the mechanism of how atomic and molecular fluorine passivate GODC defects and optimize the optical characteristics in F/Ge co-doped silica optical fiber.