Performance of Yb-doped silicate glass with thermal bleaching

A series of Yb-doped silicate glasses with the composition of 60SiO(2)-12Al(2)O(3)-28CaO-1.0 mol% Yb2O3 are prepared by a conventional melting method under normal processing conditions. These glasses are divided into two groups. One group experienced a total dose 3 kGy radiation under a Co-60 gamma radiation source, and the other group is pristine. The absorption spectra as well as the near-infrared (NIR) luminescence spectra of the glasses (pristine Ybc, irradiated Ybc, heat bleaching Ybc) are investigated. Theoretically, effects of gamma-ray radiation exposure would lead to the formation of color centers in the glass samples. Such radiation-induced color center defects cause a strong broad optical absorption band with widths from 300 to 900 nm, and its tail extends into the NIR region. In this experiment the absorption coefficient of the glass is measured by a ultraviolet-visible spectrophotometer named Lambda35, and the NIR spectrum is measured by a Zolix grating spectrometer named Omni-lambda. Furthermore, a special test system is set up to test the NIR spectrum of the glass at high temperatures. Experimental results show that the absorption coefficient of the glass after irradiation increases significantly in the visible region. The absorption coefficients of the glasses (pristine Ybc, irradiated Ybc) at 400 nm are 0.93 cm(-1) and 2.9 cm(-1) respectively. With a certain temperature treatment, the absorption coefficient of the irradiated glass is 1.89 cm(-1) at 400 nm. Compared with the absorption coefficient obtained before, it is decreased by 35%. The NIR intensities of the glasses (pristine Ybc, irradiated Ybc, heat bleaching Ybc) are 588, 261 and 436 (arbitrary units) respectively. It may be due to the color center defects produced by radiation, that have decomposed under a certain temperature treatment. As a result, this method greatly improve the optical performance of the glass. So thermal bleaching phenomenon will happen in the irradiated glass that experiences in a certain temperature treatment. Finally, results obtained in this paper may provide a theoretical basis for studying the anti-radiation of optical glasses.