Improvement of vacuum-ultraviolet transparency of silica glass by modification of point defects

Silica glass is an important optical material in deep-ultraviolet (DUV, lambda less than or similar to 300 nm) and vacuum-ultraviolet (VUV, lambda less than or similar to 200 nm) spectral regions. However, DUV-VUV transparency of silica glass is significantly influenced by the presence of structural imperfections (point defects). This article describes point defects in silica glasses of low metallic impurity contents ("synthetic" silica glasses), and optical and chemical properties of these point defects. It is shown that controlled doping with specific point defects can improve the transparency and radiation hardness of silica glass in DUV-VUV spectral region. Such doped species include network modifiers that relax the glass structure and mobile interstitial hydrogen molecules. Utilization of these techniques in developing photomask substrates for F-2 laser photolithography and DUV optical fibers for ArF laser transmission is presented.