Novel chemical sensors that improve detection and quantification of CO.sub.2 are critical to ensuring safe and cost-effective monitoring of carbon storage sites. Fiber optic (FO) based chemical sensor systems are promising field-deployable systems for real-time monitoring of CO.sub.2 in geological formations for long-range distributed sensing. In this work, a mixed-matrix composite integrated FO sensor system was developed that reliably operates as a detector for gas-phase and dissolved CO.sub.2. A mixed-matrix composite sensor coating on the FO sensor comprising plasmonic nanocrystals and zeolite embedded in a polymer matrix. The mixed-matrix composite FO sensor showed excellent reversibility/stability in a high humidity environment and sensitivity to gas-phase CO.sub.2 over a large concentration range. The sensor exhibited the ability to sense CO.sub.2 in the presence of other geologically relevant gases, which is of importance for applications in geological formations. A prototype FO sensor configuration which possesses a robust sensing capability for monitoring dissolved CO.sub.2 in natural water was demonstrated. Reproducibility was confirmed over many cycles, both in a laboratory setting and in the field.

A co-doped optical fiber is provided having an attenuation of less than about 0.17 dB/km at a wavelength of 1550 nm. The fiber includes a core region in the fiber having a graded refractive index profile with an alpha of greater than 5. The fiber also includes a first cladding region in the fiber that surrounds the core region. Further, the core region has a relative refractive index of about −0.10% to about +0.05% compared to pure silica. In addition, the core region includes silica that is co-doped with chlorine at about 1.2% or greater by weight and fluorine between about 0.1% and about 1% by weight.

A co-doped optical fiber is provided having an attenuation of less than about 0.17 dB/km at a wavelength of 1550 nm. The fiber includes a core region in the fiber having a graded refractive index profile with an alpha of greater than 5. The fiber also includes a first cladding region in the fiber that surrounds the core region. Further, the core region has a relative refractive index of about −0.10% to about +0.05% compared to pure silica. In addition, the core region includes silica that is co-doped with chlorine at about 1.2% or greater by weight and fluorine between about 0.1% and about 1% by weight.

A glass/quartz composite structure comprises quartz grit, quartz powder and glass grit wherein the glass grit is in an amount greater than any other single material by weight of the composite structure (e.g. a combined weight of the quartz grit, quartz powder, glass grit, resin, and coupling agent). Natural stone components, which may include the quartz grit and quartz powder, may be in an amount greater than 30% by weight of the composite structure. The structure may be formed into a 1.2-1.5 cm thick slab for countertops using standard cabinet perimeter support. The slab may be made by mixing the quartz grit, quartz powder, glass grit, and binding resin, pouring the mixture in a mold, and compacting the mixture in the mold. Specific natural mineral components, decorative chips, and/or wet mixture pieces may be added to the composite structure to provide aesthetics of specific natural stones.

A glass/quartz composite structure comprises quartz grit, quartz powder and glass grit wherein the glass grit is in an amount greater than any other single material by weight of the composite structure (e.g. a combined weight of the quartz grit, quartz powder, glass grit, resin, and coupling agent). Natural stone components, which may include the quartz grit and quartz powder, may be in an amount greater than 30% by weight of the composite structure. The structure may be formed into a 1.2-1.5 cm thick slab for countertops using standard cabinet perimeter support. The slab may be made by mixing the quartz grit, quartz powder, glass grit, and binding resin, pouring the mixture in a mold, and compacting the mixture in the mold. Specific natural mineral components, decorative chips, and/or wet mixture pieces may be added to the composite structure to provide aesthetics of specific natural stones.

A glass substrate for a high-frequency device, which contains SiO.sub.2 as a main component, the glass substrate having a total content of alkali metal oxides in the range of 0.001-5% in terms of mole percent on the basis of oxides, the alkali metal oxides having a molar ratio represented by Na.sub.2O/(Na.sub.2O+K.sub.2O) in the range of 0.01-0.99, and the glass substrate having a total content of alkaline earth metal oxides in the range of 0.1-13% in terms of mole percent on the basis of oxides, wherein at least one main surface of the glass substrate has a surface roughness of 1.5 nm 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.

One aspect relates to a process for the preparation of a quartz glass body, including providing a silicon dioxide granulate, wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has a BET surface area in a range from 20 to 40 m.sup.2/g, making a glass melt out of silicon dioxide granulate in an oven and making a quartz glass body out of at least part of the glass melt. The oven has at least a first and a further chamber connected to one another via a passage. The temperature in the first chamber is lower than the temperature in the further chambers. On aspect relates to a quartz glass body which is obtainable by this process. One aspect relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

One aspect relates to a process for the preparation of a quartz glass body, including providing a silicon dioxide granulate, wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has a BET surface area in a range from 20 to 40 m.sup.2/g, making a glass melt out of silicon dioxide granulate in an oven and making a quartz glass body out of at least part of the glass melt. The oven has at least a first and a further chamber connected to one another via a passage. The temperature in the first chamber is lower than the temperature in the further chambers. On aspect relates to a quartz glass body which is obtainable by this process. One aspect relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

Provided is a novel glass filler having a low permittivity. The glass filler provided includes a glass composition, wherein the glass composition includes, in wt %:95≤SiO.sub.2≤99.5; 0≤B.sub.2O.sub.3≤2; 0.01≤Al.sub.2O.sub.3≤4; 0≤R.sub.2O≤4; 0.01≤RO ≤4; and 0≤TiO.sub.2≤4, where RO is at least one selected from MgO, CaO, SrO, and ZnO, and R.sub.2O is at least one selected from Li.sub.2O, Na.sub.2O, and K.sub.2O. This glass filler can have a permittivity of less than 4 at 1 GHz.

The present invention relates to a method for evaluating the thermal expansion properties of a titania-containing glass body. On the basis of measured values, obtained at a certain temperature, for a physical parameter that changes depending on the titania concentration and a physical parameter that changes depending on the fictive temperature, the thermal expansion coefficient of the titania-containing silica glass body and the slope of the thermal expansion coefficient are calculated using a linear relational expression represented by a plurality of physical properties. The thermal expansion properties of the titania-containing silica glass body are evaluated on the basis of the calculated thermal expansion coefficient and thermal expansion coefficient slope.