Described is a method of producing synthetic fused silica in which the synthetic flame used in the method has a ratio of the Full Width at Half Maximum (FWHM.sub.vert) vertical luminous intensity to the Full Width at Half Maximum (FWHM.sub.hori) horizontal luminous intensity greater than 10 in a targetless state, the luminous intensities being measured in candela/mm.sup.2.

Described is a process for the production of synthetic fused silica in which the feedstock vapor is reacted from an organosilicon starting compound and any combustible burner auxiliary gases at an air number in the burner of less than or equal to 1.00. Furthermore, one embodiment relates to a corresponding apparatus.

Described is a process for the production of synthetic fused silica in which the feedstock vapor is reacted from an organosilicon starting compound and any combustible burner auxiliary gases at an air number in the burner of less than or equal to 1.00. Furthermore, one embodiment relates to a corresponding apparatus.

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 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.

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.

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.

A microfabrication method is provided with which it is possible to easily form a fine periodic structure on a surface of any substrate. A glass precursor is applied to a substrate, and the glass precursor is irradiated with short-pulse laser light. By the irradiation with short-pulse laser light, the glass precursor is activated to undergo a thermal reaction, and a fine periodic structure can be easily formed on the surface. Furthermore, by oxidizing the substrate on which the fine periodic structure has been formed, the hue of the surface can be improved while maintaining the fine periodic structure.

A microfabrication method is provided with which it is possible to easily form a fine periodic structure on a surface of any substrate. A glass precursor is applied to a substrate, and the glass precursor is irradiated with short-pulse laser light. By the irradiation with short-pulse laser light, the glass precursor is activated to undergo a thermal reaction, and a fine periodic structure can be easily formed on the surface. Furthermore, by oxidizing the substrate on which the fine periodic structure has been formed, the hue of the surface can be improved while maintaining the fine periodic structure.

Doped quartz glass components for use in a plasma-assisted manufacturing process contain at least one dopant which is capable of reacting with fluorine to form a fluoride compound, and the fluoride compound has a boiling point higher than that of SiF.sub.4. The doped quartz glass component has high dry-etch resistance and low particle formation, and has uniform etch removal when used in a plasma-assisted manufacturing process. The doped quartz glass has a microhomogeneity defined by (a) a surface roughness with an R.sub.a value of less than 20 nm after the surface has been subjected to a dry-etching procedure as specified in the description, or (b) a dopant distribution with a lateral concentration profile in which maxima of the dopant concentration are at an average distance apart of less than 30 μm.