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.

A method for manufacturing a quartz glass substrate with a coating formed includes: surface roughening for a base surface of the quartz glass substrate, on which the sprayed coating is formed; and a heating treatment of heating the substrate after the surface roughening. The base surface is 0.9 μm or more and 5.0 μm or less in arithmetic mean roughness (Ra) in the surface roughening. The heating treatment is performed at a temperature that is equal to or higher than a strain point (temperature at which the viscosity reaches 10.sup.13.5 Pa.Math.sec) of the quartz glass.

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.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein Th is at least about 50° C., preferably 50° C.<Th.sub.h<250° C.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50° C., preferably 50° C.<T.sub.h<250° C.

In an imprint mold-forming synthetic quartz glass substrate (1) of rectangular shape having dimensions L1 and L2 with L1≥L2, a circular region is delineated on the substrate back surface by a circle of radius R with L2−2R≥10 mm. When approximation analysis is performed from the 1st to 8th term in the Zernike polynomials on the circular region, a coefficient of the 4th term is equal to or greater than −(2R/100,000×1) μm.

The invention relates to a process for preparing a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate, ii.) Making a glass melt from the silicon dioxide granulate in a melting crucible, and iii.) Making a quartz glass body from at least a part of the glass melt, wherein the melting crucible is comprised in an oven and is made of at least one material comprising tungsten or molybdenum or a combination thereof. The invention further relates to a quartz glass body which can be obtained by this process. Further, the invention relates to a light guide, an illuminant and a formed body, each of which can be obtained by processing the quartz glass body further.

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.

A system and method for sintering a thin, high purity fused silica glass sheet having a thickness of 500 μm or less, includes a step of rastering a beam of a laser across a sheet of high purity fused silica soot; wherein a pattern of the rastering includes tightly spacing target locations on the sheet such that the laser sinters the soot and simultaneously forms tiny notches on a first major surface of the sheet when viewed in cross-section, wherein the tiny notches are crenellated such that at least some of the notches have generally flat bottom surfaces and at least some respective adjoining caps have generally plateau top surfaces offset from the bottom surfaces by steeply-angled sidewalls.

A quartz glass crucible 1 having a cylindrical side wall portion 10a, a bottom portion 10b, and a corner portion 10c connecting the side wall portion 10a and the bottom portion 10b to each other includes a transparent layer 11 made of quartz glass, and a bubble layer 12 made of quartz glass and formed outside the transparent layer 11. A ratio of an infrared transmittance of the corner portion 10c at a maximum thickness position of the corner portion 10c to an infrared transmittance of the side wall portion 10a is 0.3 or more and 0.99 or less, and an absolute value of a rate of change in infrared transmittance in a height direction along a wall surface of the crucible from a center of the bottom portion 10b toward an upper end of the side wall portion 10a is 3%/cm or less.