Abstract: Cristobalite-containing silica glass is provided wherein .alpha.-cristobalite in the shape of a small sphere or a small, round-edged or sharp-edged, three-dimensional region is dispersed in the silica glass matrix. The diameter of each .alpha.-cristobalite sphere or region is, in the range of 0.1 um to 1000 um, and the content of the .alpha.-cristobalite is at least 10 wt. %. The cristobalite-containing silica glass is produced by heating a mixture of two kinds or more of crystalline silicon dioxide powder with melting points different from each other by 20.degree. C. or more. The mixture contains silicon dioxide having the highest melting point in the range of 10 wt. % to 80 Wt. % and is heated at temperatures ranging from the lowest melting point to a temperature lower than the highest melting point.

Abstract: A process for producing opaque silica glass in which a quartz raw material grain having a particle size of 10 to 350 .mu.m is filled into a heat resistant mold, the quartz raw material grain is heated in a non-oxidizing atmosphere from a room temperature up to a temperature lower by 50.degree. to 150.degree. C. than a temperature at which the above raw material grain is melted at a temperature-increase speed not exceeding 50.degree. C./minute, then, slowly heated up to a temperature higher by 10.degree. to 80.degree. C. than the temperature at which the quartz raw material grain is melted at the speed of 10.degree. C./minute or less, and the heated quartz raw material grain is further maintained at the temperature higher by 10.degree. to 80.degree. C. than the temperature at which the quartz raw material grain is melted, followed by cooling down to the room temperature.

Abstract: A synthetic quartz glass optical member for an ultraviolet laser, where the quartz glass has a hydroxyl content of 10-100 ppm, a chlorine content of 200 ppm or less, a hydrogen content of 1.times.10.sup.16 molecules/cm.sup.3 or less, a homogeneity of refractive index of 5.times.10.sup.-6 or less in terms of .DELTA.n, and a birefringence of 5 nm/cm or less.

Abstract: This invention relates to an optical member made of highly transparent, high-purity synthetic silica glass, to a method for manufacturing a blank or an optical member of such glass, and to the optical members themselves. The optical members have an absolute refractive index, n.sub.d, of 1.460 or more and a hydrogen molecule concentration of at least 5.times.10.sup.16 molecules/cm.sup.3 uniformly distributed throughout the glass and are particularly well suited for use in apparatus in which they are exposed to a high-power laser beam such as that produced by an excimer laser.

Abstract: A synthetic quartz glass optical member for an ultraviolet laser, suitably applicable as a stepper lens of a lithographer using an excimer laser beam and other optical members, wherein the quartz glass has a hydroxyl content of 10 to 100 ppm, a chlorine content of 200 ppm or less, a hydrogen content of 1.times.10.sup.16 molecules/cm.sup.3 or less, a homogeneity of refractive index of 5.times.10.sup.-6 or less in terms of .DELTA.n, and a birefringence of 5 nm/cm or less. The optical member can be produced by subjecting a volatile silicon compound to flame hydrolysis with oxyhydrogen flame, depositing the formed particulate silica on a heat-resistant support to prepare a porous silica matrix, heating the matrix in a vacuum as high as 1.times.10.sup.-2 Torr or above to a temperature of 1,400 .degree. C.

Abstract: The invention relates to lenses, prisms or other optical members which are subjected to high-power ultraviolet light having a wavelength of about 360 nm or less, or ionizing radiation, particularly optical members for use in laser exposure apparatus for lithography, and to blanks for such optical members. The homogeneity of the refractive index distribution and the resistance to optical deterioration when the optical members are exposed for a long period of time to short wavelength ultraviolet light from a laser beam are improved. The optical members are made of high-purity synthetic silica glass material containing at least about 50 wt. ppm of OH groups, and are doped with hydrogen.

Abstract: The invention relates to lenses, prisms or other optical members which are subjected to high-power ultraviolet light having a wavelength of about 360 nm or less, or ionizing radiation, particularly optical members for use in laser exposure apparatus for lithography, and to blanks for such optical members. The homogeneity of the refractive index distribution and the resistance to optical deterioration when the optical members are exposed for a long period of time to short wavelength ultraviolet light from a laser beam are improved. The optical members are made of high-purity synthetic silica glass material containing at least about 50 wt. ppm of OH groups, and are doped with hydrogen.