Optical absorption properties of TiO2-doped silica glass in UV–VUV region

Optical absorption properties of TiO 2 -doped and non-doped silica glass (type I) were studied to investigate the effect of titanium (Ti) ion doping on absorption spectra changes produced by 7.2eV irradiation. The samples were prepared by polishing down to a thickness of about 100 μm to resolve the absorption bands in the VUV range and to measure the color center created or eliminated in the irradiated surface region. For both kinds of silica glass, the magnitude of the 7.6eV absorption band of a thin sample ( 100 μm), the 7.6eV band magnitude increased even in the early stages of irradiation. These results indicate that the type I silica glass absorbs <7eV light, which is much smaller than band gap energy of SiO 2 glass, and produces ≡Si-Si≡ bonds. The magnitude of these changes were smaller in the TiO 2 -doped silica glass. The molar extinction coefficients of TiO 2 in silica glass were determined in the 4.0-8.0eV range by using 47-150 wt ppm Ti containing samples. To avoid perturbation by absorption due to =Si-Si= bonds, the samples were heated at 950°C in hydrogen atmosphere. Two absorption maxima were observed at 6.2 and 7.6eV, and the corresponding molar extinction coefficients were estimated to be 3.0 x 10 4 and 5.5 x 10 4 Lmol -1 cm -1 , respectively. The 7.6eV absorption in the TiO 2 doped samples prevents bond breaking by VUV photon for type I silica glass.