A method of forming an optical fiber, including: exposing a soot core preform to a dopant gas at a pressure of from 1.5 atm to 40 atm, the soot core preform comprising silica, the dopant gas comprising a first halogen doping precursor and a second halogen doping precursor, the first halogen doping precursor doping the soot core preform with a first halogen dopant and the second halogen precursor doping the soot core preform with a second halogen dopant; and sintering the soot core preform to form a halogen-doped closed-pore body, the halogen-doped closed-pore body having a combined concentration of the first halogen dopant and the second halogen dopant of at least 2.0 wt %.

One aspect is a process to producing a synthetic quartz glass, including an annealing treatment that includes: putting a synthetic quartz glass as a parent material into a heat treatment furnace; elevating a temperature in the heat treatment furnace to a prescribed keeping temperature that is equal to or higher than the annealing point; keeping the keeping temperature; annealing the synthetic quartz glass; and taking the synthetic quartz glass out of the heat treatment furnace. The process includes determining an annealing rate v [° C./h] of the annealing step based on a value of S/V [mm.sup.2/mm.sup.3], wherein S [mm.sup.2] is the surface area of the synthetic quartz glass as a parent material and V [mm.sup.3] is the volume thereof and a target birefringence Re [nm/cm] for the synthetic quartz glass after the annealing, and the annealing step is performed at the determined annealing rate v.

One aspect is a process to producing a synthetic quartz glass, including an annealing treatment that includes: putting a synthetic quartz glass as a parent material into a heat treatment furnace; elevating a temperature in the heat treatment furnace to a prescribed keeping temperature that is equal to or higher than the annealing point; keeping the keeping temperature; annealing the synthetic quartz glass; and taking the synthetic quartz glass out of the heat treatment furnace. The process includes determining an annealing rate v [° C./h] of the annealing step based on a value of S/V [mm.sup.2/mm.sup.3], wherein S [mm.sup.2] is the surface area of the synthetic quartz glass as a parent material and V [mm.sup.3] is the volume thereof and a target birefringence Re [nm/cm] for the synthetic quartz glass after the annealing, and the annealing step is performed at the determined annealing rate v.

The present disclosure relates to a glass cloth, prepreg, and printed circuit board.

There is provided a glass cloth including woven glass yarns each containing a plurality of filaments, wherein a bulk dissipation factor of a glass in the glass yarns is 0.0010 or less, a tensile strength of warp yarns per thickness of the glass cloth as represented by the following formula (A) is in the range of 0.50 to 6.0:

warp direction tensile strength (N/25 mm) of the glass cloth/thickness of the glass cloth (m)(A) a coefficient of variation of the warp direction tensile strength of the glass cloth is in the range of 15% or less, and a dissipation factor of the glass cloth at 10 GHz is in the range of greater than 0 and 0.0010 or less.

A photodarkening-resistant ytterbium-doped quartz optical fiber and a method for prpearing such a fiber are provided. Glass of a photodarkening-resistant ytterbium-doped quartz optical fiber core rod includes at least Yb.sub.2O.sub.3, Al.sub.2O.sub.3, P.sub.2O.sub.5, SiO.sub.2. The proportions of Yb.sub.2O.sub.3, Al.sub.2O.sub.3, and P.sub.2O.sub.5 in the entire substance are Yb.sub.2O.sub.3: 0.05-0.3 mol %, Al.sub.2O.sub.3: 1-3 mol %, and P.sub.2O.sub.5: 1-5 mol %, respectively. In the preparation method for the photodarkening-resistant ytterbium-doped quartz optical fiber, a sol-gel method and an improved chemical vapor deposition method are combined. By using the molecular-level doping uniformity and the low preparation loss thereof respectively, ytterbium ions, aluminum ions and phosphorus ions are effectively doped in a quartz matrix, thereby effectively solving the problems in the optical fiber of high loss, photodarkening caused by cluster or the like, and a central refractive index dip.

In an exemplary embodiment, a quartz glass crucible 1 includes: a cylindrical crucible body 10 which has a bottom and is made of quartz glass; and a first crystallization-accelerator-containing coating film 13A which is formed on an inner surface 10a so as to cause an inner crystal layer composed of an aggregate of dome-shaped or columnar crystal grains to be formed on a surface-layer portion of the inner surface 10a of the crucible body 10 by heating during a step of pulling up the silicon single crystal by a Czochralski method. The quartz glass crucible is capable of withstanding a single crystal pull-up step undertaken for a very long period of time.

A process for producing a glass body, the process including flowing oxygen gas from a burner in a furnace at a flow rate of greater than 12.0 standard liters per minute and flowing a precursor gas mixture from the burner. The process further including oxidizing the precursor gas mixture with the oxygen gas to form glass particles and depositing the glass particles on a collection cup to form the glass body.

The present disclosure provides a method to fabricate three-dimensional transparent glass utilizing polymer plasticity, including the following steps. In step 1, synthesize polymer-glass powder composite containing dynamic chemical bonds, the bond exchange catalyst is added during the synthesis process, and then cure to obtain a two-dimensional sheet shape I, the bond exchange catalyst is used to activate a dynamic chemical bond in step 2. In step 2, shape the two-dimensional sheet shape I obtained in step 1 into a complex three-dimensional shape II under the conditions of the effect of an external force and the activable dynamic chemical bond. In step 3, pyrolyze the composite precursor at high temperature to obtain transparent glass with complex three-dimensional shape II. The present disclosure provides a method in shaping the transparent glass with complex geometries by unique polymer plasticity in lower temperature.

Provided is a silica glass member for hermetic sealing of an ultraviolet SMD LED element to be suitably used for hermetic sealing of, and as a transmission window material for, a surface mount-type package (SMD) having an ultraviolet LED mounted thereon and configured to emit ultraviolet light in a wavelength range of from 200 nm to 350 nm. The silica glass member for hermetic sealing includes a silica glass substrate, which is homogeneously and integrally formed without an internal boundary, wherein the silica glass substrate has: a first surface on an inside opposed to an SMD LED element; and a second surface on an outside corresponding to the first surface, wherein an outer peripheral portion of the first surface has formed therein a substrate joining plain surface for joining to the container outer periphery joining plain surface, and wherein the second surface on the outside corresponding to the first surface has formed therein a lens-like convex portion configured to process emitted light from the ultraviolet SMD LED element.

Provided is a silica glass member for hermetic sealing of an ultraviolet SMD LED element to be suitably used for hermetic sealing of, and as a transmission window material for, a surface mount-type package (SMD) having an ultraviolet LED mounted thereon and configured to emit ultraviolet light in a wavelength range of from 200 nm to 350 nm. The silica glass member for hermetic sealing includes a silica glass substrate, which is homogeneously and integrally formed without an internal boundary, wherein the silica glass substrate has: a first surface on an inside opposed to an SMD LED element; and a second surface on an outside corresponding to the first surface, wherein an outer peripheral portion of the first surface has formed therein a substrate joining plain surface for joining to the container outer periphery joining plain surface, and wherein the second surface on the outside corresponding to the first surface has formed therein a lens-like convex portion configured to process emitted light from the ultraviolet SMD LED element.