Fluorine-doped SiO2 glasses for F2 excimer laser optics:: fluorine content and color-center formation

Color-center formation in F-doped, OH-free synthetic SiO2 glasses by irradiation with F-2 excimer lasers (157 nm) was examined as a function of the F content. The concentration of photoinduced E' centers was reduced to similar to 1/20 by 1 mol.% F-2 doping and remained almost constant on further doping to 7.3 mol.%. The absorption edge was considerably shifted to a lower wavelength (157.4 nm --> 153 nm for a 5-mm-thick sample) by 1-mol.% doping and decreased only slightly on further doping. The intensities of the Raman bands that are due to three- and four-membered ring structures were significantly reduced by 1-mol.% F doping. These results strongly suggest that elimination of strained Si-O-Si bonds by F doping plays a central role in the improvement of radiation resistance of SiO2 glasses to Pt laser light. (C) 1999 Optical Society of America.