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

Abstract

Silica glass is an important optical material in deep-ultraviolet (DUV, λ≲300nm) and vacuum-ultraviolet (VUV, λ≲200nm) 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 F2 laser photolithography and DUV optical fibers for ArF laser transmission is presented.