Gamma Radiation Effects on the Optical Properties of Yb-doped Silicate Glasses

A series of Yb-doped silicate glasses were prepared by a conventional melting method under normal processing conditions. The effects of gamma-ray (from a 60Co γ source) radiation on the absorption and emission properties of all glass samples were investigated. The radiation exposure leaded to the formation of color centers in glass samples. Such radiation-induced photodarkening caused a strong broad optical absorption band, which had a maximum wavelength centered at around 400 nm and the tail extended into the near infrared region. In addition, a minor part of the Yb3+ ions were converted into Yb2+ by trapping free electrons during irradiation based on the radiation induced absorption (RIA) spectra. The excitation energy could be transfered from Yb3+ ions to radiation-induced defects through cooperative upconversion or multiphoton absorption processes under 960 nm LD pumping. Such energy transfer processes resulted in a decrease of the upper state lifetime of Yb3+ ion which was accompanied by an increase in oxygen deficient center ODC(2) defect fluorescence at around 476 nm. Photobleaching effect was observed in irradiated Yb-doped glasses during the fluorescence measurement at room temperature.