One aspect is a method for producing a hollow porous quartz glass base material. Even when the hollow porous quartz glass base material is produced in large weight and high bulk density, the ease of target extraction is maintained and target extraction is performed stably. The method includes preparing a heat resistant substrate, which has an outer surface on which SiO.sub.2 particles are deposited, the outer surface having a surface roughness in which the maximum height Rz is less than 9 μm and the arithmetic average roughness Ra is less than 1 μm. The heat resistant substrate is rotated and SiO.sub.2 particles are deposited on the outer surface of the heat resistant substrate to form a glass particulate deposit. The heat resistant substrate is extracted from the glass particulate deposit to produce the base material.

A mold includes a lower mold core and an upper mold core. The lower mold core has a first outside surface and a first molding surface including a first molding portion and a first supporting portion surrounding the molding portion. The upper mold core has a second molding surface opposite to the first molding surface and encloses a molding cavity with the first molding surface. The lower mold core includes a first gas inlet on the first outside surface, a first gas outlet on the first supporting portion, and a first gas channel in the lower mold core, the first gas channel connecting the first gas inlet and the first gas outlet. Gas flow out from the first gas outlet to separate the glass product from the lower mold core before the glass product is completely cooled down, which can avoid many adverse effects during the glass product process.

A mold includes a lower mold core and an upper mold core. The lower mold core has a first outside surface and a first molding surface including a first molding portion and a first supporting portion surrounding the molding portion. The upper mold core has a second molding surface opposite to the first molding surface and encloses a molding cavity with the first molding surface. The lower mold core includes a first gas inlet on the first outside surface, a first gas outlet on the first supporting portion, and a first gas channel in the lower mold core, the first gas channel connecting the first gas inlet and the first gas outlet. Gas flow out from the first gas outlet to separate the glass product from the lower mold core before the glass product is completely cooled down, which can avoid many adverse effects during the glass product process.

A method for the production of synthetic quartz glass using a special cleaning device is provided. The method includes (a) evaporating a production material containing a polymerizable polyalkylsiloxane compound while forming a production material vapor, (b) passing the production material vapor resulting from step (a) through a cleaning device to purify the production material vapor, (c) supplying the purified production material vapor resulting from step (b) to a reaction zone in which the purified production material vapor is converted to SiO.sub.2 particles through oxidation and/or through hydrolysis, (d) depositing the SiO.sub.2 particles resulting from step (c) on a deposition surface, and optionally drying and vitrifying the deposited SiO.sub.2 particles resulting from step (d) to form synthetic quartz glass. The cleaning device includes a bulk of porous silica particles which have a BET specific surface area of at least 2 m.sup.2/g. A device for carrying out the method is also provided.

An additive manufacturing process includes forming an object material stack using sheet materials without use of binder material between the sheet materials and forming features of the cross-sectional layers of a 3D object in the corresponding sheet materials. Another process involves forming features of the cross-sectional layers of a 3D object in soot layers of a laminated soot sheet. A manufactured article includes three or more glass layers laminated together without any binder material between the glass layers. At least one of the glass layers is composed of silica or doped silica, and at least one feature is formed in at least one of the glass layers.

Laser waveguides, methods and systems for forming a laser waveguide are provided. The waveguide includes an inner cladding layer surrounding a central axis and a glass core surrounding and located outside of the inner cladding layer. The glass core includes a laser-active material. The waveguide includes an outer cladding layer surrounding and located outside of the glass core. The inner cladding, outer cladding and/or core may surround a hollow central channel or bore and may be annular in shape.

Annealing treatments for modified titania-silica glasses and the glasses produced by the annealing treatments. The annealing treatments include an isothermal hold that facilitates equalization of non-uniformities in fictive temperature caused by non-uniformities in modifier concentration in the glasses. The annealing treatments may also include heating the glass to a higher temperature following the isothermal hold and holding the glass at that temperature for several hours. Glasses produced by the annealing treatments exhibit high spatial uniformity of CTE, CTE slope, and fictive temperature, including in the presence of a spatially non-uniform concentration of modifier.

A glass substrate for a high-frequency device, which contains, in terms of mole percent on the basis of oxides: 40 to 75% of SiO.sub.2; 0 to 15% of Al.sub.2O.sub.3; 13 to 23% of B.sub.2O.sub.3; 2.5 to 11% of MgO; and 0 to 13% of CaO, and having a total content of alkali metal oxides in the range of 0.001-5%, where at least one main surface of the glass substrate has a surface roughness of 1.5 um or less in terms of arithmetic average roughness Ra. and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.

A glass substrate for a high-frequency device, which contains, in terms of mole percent on the basis of oxides: 40 to 75% of SiO.sub.2; 0 to 15% of Al.sub.2O.sub.3; 13 to 23% of B.sub.2O.sub.3; 2.5 to 11% of MgO; and 0 to 13% of CaO, and having a total content of alkali metal oxides in the range of 0.001-5%, where at least one main surface of the glass substrate has a surface roughness of 1.5 um or less in terms of arithmetic average roughness Ra. and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.

A laser sintering device for producing parts composed of powder materials is disclosed, the device including a mechanism which allows for porosity control during production of parts made with the materials. A method of producing a three-dimensional object is also provided, which includes the steps of disposing a layer of a powder material on a target surface, applying pressure to a powder material layer and directing an energy beam over a selected area of the powder material layer, wherein the powder is sintered or melted, and repeating the steps to form the three-dimensional object. The resultant three-dimensional objects made of powder material are also described.