One aspect is a process for the preparation of a quartz glass body including providing a silicon dioxide granulate wherein the provision includes providing silicon dioxide powder, and processing the silicon dioxide powder to obtain a silicon dioxide granulate. The silicon dioxide granulate has a larger particle diameter than the silicon dioxide powder. The processing includes processing the silicon dioxide powder to obtain a silicon dioxide granulate I, wherein the silicon dioxide granulate I has a first carbon content wC(1), treating the silicon dioxide granulate I with a reactant to obtain a silicon dioxide granulate II with a further carbon content wC(2), wherein the further carbon content wC(2) is less than the first carbon content wC(1), making a glass melt out of the silicon dioxide granulate and making a quartz glass body out of at least part of the glass melt.

The invention relates to a process for preparing a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate, ii.) Making a glass melt from the silicon dioxide granulate in a melting crucible, and iii.) Making a quartz glass body from at least a part of the glass melt, wherein the melting crucible is comprised in an oven and is made of at least one material comprising tungsten or molybdenum or a combination thereof. The invention further relates to a quartz glass body which can be obtained by this process. Further, the invention relates to a light guide, an illuminant and a formed body, each of which can be obtained by processing the quartz glass body further.

The invention relates to a process for the preparation of a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate obtainable from a silicon dioxide powder, wherein the silicon dioxide granulate has a larger particle size than the silicon dioxide powder, ii.) Making a glass melt out of silicon dioxide granulate and iii.) Making a quartz glass body out of at least part of the glass melt, wherein the melting crucible has at least one inlet and at least one outlet, wherein at least part of the glass melt is removed via the melting crucible outlet. The invention further relates to a quartz glass body which is obtainable by this process. The invention further relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

A diffuser material of synthetically produced, pore-containing quartz glass and a method for the manufacture of a molded body consisting fully or in part thereof. The diffuser material has a chemical purity of at least 99.9% SiO.sub.2, a cristobalite content of not more than 1%, and a density in the range of 2.0 to 2.18 g/cm.sup.3. Starting therefrom, to indicate a diffuser material which is improved with respect to diffuse reflectivity with Lambertian behavior over a wide wavelength range, high material homogeneity and UV radiation resistance, the quartz glass has a hydroxyl group content in the range of at least 200 wt. ppm and at least 80% of the pores have a maximum pore dimension of less than 20 m.

One aspect relates to a process for the preparation of a quartz glass body, including provision of a silicon dioxide granulate, making a glass melt from the silicon dioxide granulate and making a quartz glass body from at least part of the glass melt. The provision includes making a silicon dioxide powder with at least two particles prepared from a silicon-chlorine compound, bringing the silicon dioxide powder into contact with ammonia to obtain a treated silicon dioxide powder, and granulating the treated silicon dioxide powder to obtain a silicon dioxide granulate. The chlorine content of the silicon dioxide powder is greater than the chlorine content of the silicon dioxide granulate. One aspect relates further to a quartz glass body which is obtainable by this process. One aspect also relates to a process for the preparation of a silicon dioxide granulate.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate I prepared from a pyrogenically produced silicon dioxide powder, treating the silicon dioxide granulate I with a reactant at a temperature in a range from 1000 to 1300 C., and making a glass melt out of the silicon dioxide granulate. A quartz glass body is made out of at least a part of the glass melt. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to a light guide, an illuminant, and a formed body, each of which is obtainable by further processing of the quartz glass body. One aspect additionally relates to a process for the preparation of a silicon dioxide granulate II.

An optical fiber has a core region that is doped with one or more viscosity-reducing dopants in respective amounts that are configured, such that, in a Raman spectrum with a frequency shift of approximately 600 cm.sup.1, the fiber has a nanoscale structure having an integrated D2 line defect intensity of less than 0.025. Alternatively, the core region is doped with one or more viscosity-reducing dopants in respective amounts that are configured such that the fiber has a residual axial compressive stress with a stress magnitude of more than 20 MPa and a stress radial extent between 2 and 7 times the core radius.

According to another aspect of the invention a majority of the optical propagation through the fiber is supported by an identified group of fiber regions comprising the core region and one or more adjacent cladding regions. The fiber regions are doped with one or more viscosity-reducing dopants in respective amounts and radial positions that are configured to achieve viscosity matching among the fiber regions in the identified group.

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.

An optical fiber has a core region that is doped with one or more viscosity-reducing dopants in respective amounts that are configured, such that, in a Raman spectrum with a frequency shift of approximately 600 cm.sup.1, the fiber has a nanoscale structure having an integrated D2 line defect intensity of less than 0.025. Alternatively, the core region is doped with one or more viscosity-reducing dopants in respective amounts that are configured such that the fiber has a residual axial compressive stress with a stress magnitude of more than 20 MPa and a stress radial extent between 2 and 7 times the core radius. According to another aspect of the invention a majority of the optical propagation through the fiber is supported by an identified group of fiber regions comprising the core region and one or more adjacent cladding regions. The fiber regions are doped with one or more viscosity-reducing dopants in respective amounts and radial positions that are configured to achieve viscosity matching among the fiber regions in the identified group.

An optical component made of synthetic quartz glass includes a glass structure substantially free of oxygen defect sites and having a hydrogen content of 0.110.sup.16 to 1.010.sup.18 molecules/cm.sup.3, an SiH group content of less than 210.sup.17 molecules/cm.sup.3, a hydroxyl group content of 0.1 to 100 wt. ppm, and an Active temperature of less than 1070 C. The optical component undergoes a laser-induced change in the refractive index in response to irradiation by a radiation with a wavelength of 193 nm using 510.sup.9 pulses with a pulse width of 125 ns and a respective energy density of 500 J/cm.sup.2 at a pulse repetition frequency of 2000 Hz. The change totals a first measured value M.sub.193 nm when measured using the applied wavelength of 193 nm and a second measured value M.sub.633 nm when measured using a measured wavelength of 633 nm. The ratio M.sub.193 nm/M.sub.633 nm is less than 1.7.