Optical member of synthetic quartz glass for excimer lasers and method for producing same

A method for producing an optical member for excimer lasers made from synthetic quartz glass which has an OH group-content ranging from 10 to 100 ppm, a chlorine-content of not more than 200 ppm, a hydrogen molecule-content of not more than 1.times.10.sup.16 molecules/cm.sup.3, a uniformity of refractive index distribution of not more than 5.times.10.sup.-6 as expresses in terms of .DELTA.n wherein .DELTA.n represents the refractive index difference between the maximum index and the minimum index, and a birefringence of not more than 5 nm/cm, comprising the steps of:

• flame-hydrolyzing a volatile silicon compound using an oxyhydrogen flame to form fine silica particles;
• depositing the fine silica particles on a heat-resistant substrate to give a porous silica ingot;
• dehydrating and degasifying by heating the porous silica ingot at a temperature of not less than 1400.degree. C. and a high degree of vacuum on the order of not less than 1.times.10.sup.-2 Torr, wherein said dehydrating and degasifying steps occur either sequentially or simultaneously;
• uniformizing the dehydrated and degasified transparent quartz glass to give highly uniform quartz glass free of stria in at least on direction thereof;
• molding the resulting highly uniform quartz glass;
• and
• annealing the molded quartz glass article.