A diffuser material of synthetically produced, pore-containing quartz glass and a method for the manufacture of a molded body consisting fully or in part thereof. The diffuser material has a chemical purity of at least 99.9% SiO.sub.2, a cristobalite content of not more than 1%, and a density in the range of 2.0 to 2.18 g/cm.sup.3. Starting therefrom, to indicate a diffuser material which is improved with respect to diffuse reflectivity with Lambertian behavior over a wide wavelength range, high material homogeneity and UV radiation resistance, the quartz glass has a hydroxyl group content in the range of at least 200 wt. ppm and at least 80% of the pores have a maximum pore dimension of less than 20 μm.

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.

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 coating film-attached glass comprising a glass substrate, and a coating film provided on at least a part of a surface of the glass substrate, in which a region from the surface of the glass substrate on the coating film side to a predetermined depth is a modified layer, and the modified layer has a microcrystalline structure at least in part.

A coating film-attached glass comprising a glass substrate, and a coating film provided on at least a part of a surface of the glass substrate, in which a region from the surface of the glass substrate on the coating film side to a predetermined depth is a modified layer, and the modified layer has a microcrystalline structure at least in part.

The present application provides a process of fabrication of erbium and ytterbium-co-doped multielements silica glass based cladding-pumped fiber for use as a highly efficient high power optical amplifier.

A silica-titania glass substrate comprising: (i) a composition comprising 5 weight percent to 10 weight percent TiO.sub.2; (ii) a coefficient of thermal expansion (CTE) at 20° C. in a range from −45 ppb/K to +20 ppb/K; (iii) a crossover temperature (Tzc) in a range from 10° C. to 50° C.; (iv) a slope of CTE at 20° C. in a range from 1.20 ppb/K.sup.2 to 1.75 ppb/K.sup.2; (v) a refractive index variation of less than 140 ppm; and (vi) 600 ppm OH group concentration or greater. The substrate can have a mass of 1 kg or greater and less than 0.05 gas inclusions per cubic inch via a method comprising (i) forming the substrate from soot particles comprising SiO.sub.2 and TiO.sub.2, and (ii) subjecting the substrate to an environment having an elevated temperature and an elevated pressure for a period of time until the substrate comprises less than 0.05 gas inclusions per cubic inch.

A silica-titania glass substrate comprising: (i) a composition comprising 5 weight percent to 10 weight percent TiO.sub.2; (ii) a coefficient of thermal expansion (CTE) at 20° C. in a range from −45 ppb/K to +20 ppb/K; (iii) a crossover temperature (Tzc) in a range from 10° C. to 50° C.; (iv) a slope of CTE at 20° C. in a range from 1.20 ppb/K.sup.2 to 1.75 ppb/K.sup.2; (v) a refractive index variation of less than 140 ppm; and (vi) 600 ppm OH group concentration or greater. The substrate can have a mass of 1 kg or greater and less than 0.05 gas inclusions per cubic inch via a method comprising (i) forming the substrate from soot particles comprising SiO.sub.2 and TiO.sub.2, and (ii) subjecting the substrate to an environment having an elevated temperature and an elevated pressure for a period of time until the substrate comprises less than 0.05 gas inclusions per cubic inch.

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.

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.