Irradiation induced defects in fluorine doped silica

The role of fluorine doping in the response to UV pulsed laser and γ radiation of silica preforms and fibers was studied using electron spin resonance (ESR) spectroscopy. Exposure to radiation mainly generates E′ centers, with the same effectiveness in fibers and in preforms. The E′ concentration in F-doped silica fibers is found to increase with UV energy fluence till a saturation value, consistently with a precursor conversion process. These results show the fluorine role in reducing the strained Si–O bonds thus improving the radiation hardness of silica, also after drawing process.