Phase separation in highly photosensitive tin-codoped silica optical fibers and fiber preforms exposed to UV radiation

Sn-doped silicate fibers exhibit extremely high photosensitivity when exposed to 248 nm KrF excimer laser. Electron micrograph probing has shown that nanoscale phase separation occurs in fibers and fiber preforms after UV exposure. This phenomenon has been observed only in SnO₂-doped germanosilicate and phosphosilicate fibers and fiber preforms when the SnO₂ concentration is high. At low SnO₂ concentrations no phase separation has been observed. SnO₂ codoped glasses are the first optical fibers to exhibit phase separation.