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RESEARCH PRODUCT

<title>Advances in silica-based glasses for UV and vacuum UV laser optics</title>

subject

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The origins of pre-existing and laser-induced ultraviolet (UV) and vacuum ultraviolet (VUV) optical absorption in state-of-the-art glassy silicon dioxide and the ways to improve it are reviewed. The main causes of pre-existing absorption in UV/VUV are oxygen vacancies, hydroxyl (silanol) groups, and strained bonds/localized states due to glassy disorder. The main absorption bands induced by UV/VUV excimer lasers are due to oxygen vacancies and due to silicon and oxygen dangling bonds (E'-centers and non-bridging oxygen hole centers, respectively). The optimized glasses are achieved via an intricate balance between a good stoichiometry, use of network modifiers (F or OH) to reduce the number of strained bonds, minimized number of Si-OH-related absorbers and using of interstitial hydrogen for annealing of photoinduced defects. The optimization is different for KrF, ArF or F2 excimer laser energies. The most significant advance to increase VUV transparency and laser toughness is fluorine doping. F-doped ("modified") silica glasses show superior transparency and radiation resistance in VUV region and are suitable for photomask substrates in F2-laser based microlithography or for deep-UV optical fibers.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.