The present invention relates to a silica glass including bublles in the number of 1×10.sup.7/cm.sup.3 to 1×10.sup.15/cm.sup.3 and having a density of 0.5 g/cm.sup.3 to 1.95 g/cm.sup.3. The present invention also relates to a method for producing a silica glass, including: a step of depositing SiO.sub.2 fine particles generated by flame hydrolysis of a silicon compound, to obtain a silica glass porous body; a step of heating and sintering the silica glass porous body in an inert gas atmosphere, to obtain a silica glass dense body; and a step of performing a foaming treatment to heat the silica glass dense body under a reduced pressure condition.

A method to transfer a layer of harder thin film substrate onto a softer, flexible substrate. In particular, the present invention provides a method to deposit a layer of sapphire thin film on to a softer and flexible substrate e.g. quartz, fused silica, silicon, glass, toughened glass, PET, polymers, plastics, paper and fabrics. This combination provides the hardness of sapphire thin film to softer flexible substrates.

A method to transfer a layer of harder thin film substrate onto a softer, flexible substrate. In particular, the present invention provides a method to deposit a layer of sapphire thin film on to a softer and flexible substrate e.g. quartz, fused silica, silicon, glass, toughened glass, PET, polymers, plastics, paper and fabrics. This combination provides the hardness of sapphire thin film to softer flexible substrates.

A silica glass crucible includes a cylindrical side wall portion, a curved bottom portion, and a corner portion that is provided between the side wall portion and the bottom portion and has a higher curvature than a curvature of the bottom portion, in which a first region provided from a crucible inner surface to a middle in a thickness direction, a second region that is provided outside the first region in the thickness direction and has a different strain distribution from the first region, and a third region that is provided outside the second region in the thickness direction and up to the crucible outer surface and has a different strain distribution from the second region, are provided, and internal residual stresses of the first region and the third region are compressive stresses, whereas an internal residual stress of the second region includes a tensile stress.

A system, device, and method for laser cooling rare earth doped silica glass using anti-Stokes fluorescence is disclosed. The system includes a rare earth doped and codoped with one or more codopants silica glass; a laser that provides radiation to a first surface and through a body of the rare earth doped silica glass, wherein the laser is tuned from a first wavelength to a second wavelength; and a thermally sensitive device that captures images of the rare earth doped silica glass as the laser is tuned and determines a third wavelength between the first wavelength and the second wavelength where the rare earth doped silica glass is maximumly or near maximumly cooled.

A large-size synthetic quartz glass substrate has a diagonal length of at least 1,000 mm. Provided that an effective range is defined on the substrate surface, and the effective range is partitioned into a plurality of evaluation regions such that the evaluation regions partly overlap each other, a flatness in each evaluation region is up to 3 μm. From the quartz glass substrate having a high flatness and a minimal local gradient within the substrate surface, a large-size photomask is prepared.

A large-size synthetic quartz glass substrate has a diagonal length of at least 1,000 mm. Provided that an effective range is defined on the substrate surface, and the effective range is partitioned into a plurality of evaluation regions such that the evaluation regions partly overlap each other, a flatness in each evaluation region is up to 3 μm. From the quartz glass substrate having a high flatness and a minimal local gradient within the substrate surface, a large-size photomask is prepared.

Disclosed is a method of treating the surface of a quartz member. The method can remove a masking material generated by a chemical reaction between the quartz member and an etching solution, thereby completely removing scratches on the surface of the quartz member without interrupting the treatment process unlike existing technologies. The method also embosses the surface of the quartz member, thereby increasing the frictional resistance and surface roughness of the surface of the quartz member depending on the shape or density of protrusions on the surface. In addition, the method prevents deposits on the surface of the quartz member from peeling off.

A method for producing a glass filament, the method including: irradiating a raw yarn containing 70 wt % or more of SiO.sub.2 and having a raw yarn diameter of 100 to 2,000 μm with laser light having a wavelength of 0.7 to 100 μm to heat the raw yarn; and stretching the raw yarn to obtain the glass filament having a hydroxyl group (Si—OH) content of 300 ppm or less and a diameter of 1 to 20 μm.

A method for producing a glass filament, the method including: irradiating a raw yarn containing 70 wt % or more of SiO.sub.2 and having a raw yarn diameter of 100 to 2,000 μm with laser light having a wavelength of 0.7 to 100 μm to heat the raw yarn; and stretching the raw yarn to obtain the glass filament having a hydroxyl group (Si—OH) content of 300 ppm or less and a diameter of 1 to 20 μm.