Hollow ingots of transparent synthetic vitreous silica glass of external diameter greater than 400 mm and internal diameter greater than 300 mm are disclosed. The ingots are substantially free from bubbles or inclusions greater than 100 m in diameter, have no more than 100 ppB of any individual metallic impurity, and have chlorine concentration less than 5 ppM. Also disclosed are methods for producing such ingots, in which a porous soot body of density greater than 0.4 g/cm.sup.3 is deposited on an oxidation resistant mandrel. The soot body is dehydrated on a mandrel comprising graphite, carbon fiber reinforced carbon, silicon carbide, silicon impregnated silicon carbide, silicon carbide-coated graphite or vitreous silica, either under vacuum or in the presence of a reducing gas, and then sintered to transparent pore-free glass under vacuum or in an atmosphere of helium.

A doped silica-titania (DST) glass article that includes a glass article having a glass composition comprising a silica-titania base glass containing titania at 7 to 14 wt. % and a balance of silica, and a dopant selected from the group consisting of (a) F at 0.7 to 1.5 wt. %, (b) B.sub.2O.sub.3 at 1.5 to 5 wt. %, (c) OH at 1000 to 3000 ppm, and (d) B.sub.2O.sub.3 at 0.5 to 2.5 wt. % and OH at 100 to 1400 ppm. The glass article has an expansivity slope of less than about 1.3 ppb/K.sup.2 at 20 C. For DST glass articles doped with F or B.sub.2O.sub.3, the OH level can be held to less than 10 ppm, or less than 100 ppm, respectively. In many aspects, the DST glass articles are substantially free of titania in crystalline form.

The present invention relates to a method of manufacturing an optical fiber preform for obtaining an optical fiber with low transmission loss. A core preform included in the optical fiber preform comprises three or more core portions, which are each produced by a rod-in-collapse method, and in which both their alkali metal element concentration and chlorine concentration are independently controlled. In two or more manufacturing steps of the manufacturing steps for each of the three or more core portions, an alkali metal element is added. As a result, the mean alkali metal element concentration in the whole core preform is controlled to 7 atomic ppm or more and 70 atomic ppm or less.

The Ti.sup.3+ ions present in Ti-doped silica glass cause a brown staining of the glass, causing inspection of the lens to become more difficult. Known methods for reducing Ti.sup.3+ ions in favor of Ti.sup.4+ ions in Ti-doped silica glass include a sufficiently high proportion of OH-groups and carrying out an oxygen treatment prior to vitrification, which both have disadvantages. In order to provide a cost-efficient production method for Ti-doped silica glass, which at a hydroxyl group content of less than 120 ppm shows an internal transmittance (sample thickness 10 mm) of at least 70% in the wavelength range of 400 nm to 1000 nm, the TiO.sub.2SiO.sub.2 soot body is subjected to a conditioning treatment with a nitrogen oxide prior to vitrification. The blank produced in this way from Ti-doped silica glass has the ratio Ti.sup.3+/Ti.sup.4+510.sup.4.

There is provided a method for producing a low-loss alkali metal-doped silica core optical fiber having excellent hydrogen resistance. The method for producing the optical fiber according to the present invention includes a drawing step of drawing an optical fiber preform in a drawing furnace to produce a silica glass-based optical fiber including a core region containing an alkali metal with an average concentration of 0.5 atomic ppm or more and a cladding region that surrounds the core region and a heating step of heating the optical fiber in a heating furnace through which the optical fiber drawn from the drawing furnace passes.

A quartz glass fibre includes a fibre core of quartz glass produced by modified chemical vapor deposition (MCVD). A fluorine-doped radial layer is provided on the fibre core. A cladding layer of quartz glass contains chlorine and covers the fluorine-doped radial layer to define a hydrogen barrier around the fibre core in response to being irradiated by defect-generating ultra-violet (UV) radiation. The cladding layer has at least one of a combination of E defects and non-bridging oxygen hole center (NBOHC) defects and a combination of SiOH and SiH compounds.

A method of manufacturing a quartz glass fibre includes producing a quartz glass primary preform by modified chemical vapor deposition (MCVD) in a quartz glass substrate tube and inserting the quartz glass primary preform into a glass jacketing tube. Defect-generating UV radiation is irradiated into the cross-sectional area of the glass jacketing tube while combining the quartz glass primary preform with the glass jacketing tube in the jacketing process to form a cladding layer to a secondary preform. A quartz glass fibre is pulled from the secondary preform.

Ultralow expansion titania-silica glass. The glass has high hydroxyl content and optionally include one or more dopants. Representative optional dopants include boron, alkali elements, alkaline earth elements or metals such as Nb, Ta, Al, Mn, Sn Cu and Sn. The glass is prepared by a process that includes steam consolidation to increase the hydroxyl content. The high hydroxyl content or combination of dopant(s) and high hydroxyl content lowers the fictive temperature of the glass to provide a glass having a very low coefficient of thermal expansion (CTE), low fictive temperature (T.sub.f), and low expansivity slope.

A method for producing a silica glass blank co-doped with titanium and fluorine for use in EUV lithography includes (a) producing a TiO.sub.2SiO.sub.2 soot body by flame hydrolysis of silicon- and titanium-containing precursor substances, (b) fluorinating the TiO.sub.2SiO.sub.2 soot body to form a fluorine-doped TiO.sub.2SiO.sub.2 soot body, (c) treating the fluorine-doped TiO.sub.2SiO.sub.2 soot body in a water vapor-containing atmosphere to form a conditioned soot body, and (d) vitrifying the conditioned soot body to form the blank. The blank has an internal transmission of at least 60% in the wavelength range of 400 to 700 nm at a sample thickness of 10 mm, a mean OH content in the range of 10 to 100 wt. ppm and a mean fluorine content in the range of 2,500 to 10,000 wt. ppm. Titanium is present in the blank in the oxidation forms Ti3.sup.+ and Ti.sup.4+.

A process of forming a titania-silica glass body, the process including exposing a titania-doped silica soot body to a constant steam pressure step during which the partial steam pressure is at a first partial pressure of steam P1 that is from about 0 Torr to about 760 Torr and exposing the soot body to a ramp-up steam pressure step during which the partial steam pressure increases from the first partial pressure of steam P1 to a second partial pressure of steam P2, the second partial pressure of steam P2 being from about 50 Torr to about 760 Torr. The second partial pressure of steam P2 being greater than the first partial pressure of steam P1. The process further including heating the soot body during the constant steam pressure step and during the ramp-up steam pressure step and increasing the temperature during at least one of the constant steam pressure step and the ramp-up steam pressure step.