Conversion mechanisms of peroxy linkage defect in silica optical fiber

We present first principles calculations on conversion of a peroxy linkage (POL, Si  O  O  Si) defect. GW and Bethe-Salpeter equation methods are introduced. POL defect has different reaction paths when interacts with H2. It will convert into silanol (SiOH+SiOH) at the ground state (S0) and likely to transfer into SiOOH + SiH at the triplet state (T1). Optical absorption strength of hydrogen-induced defects is higher than the POL defect between 6 and 8 eV and would be more easily lead to a laser-induced damage phenomenon. Our results not only display a better understanding of how H2 molecular interacts with the POL defect, but also provide a guidance to figure out these defects in silica fiber.