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Abrasive properties of cocoon shaped silica particles fabricated by a sol–gel method have been studied. Since silicon wafers are polished with slurry by the mechanism of Chemical Mechanical Polishing, polishing rates may depend on various chemical and mechanical factors, such as particle concentration in slurry, slurry pH and kinds of basic compounds for controlling the slurry pH.

Erbium-doped silica-based glass for optical amplifiers is fabricated from silica powders by a compression-forming method using a cold isostatic pressing (CIP) technique. Silica powders are prepared from slurry containing fumed silica with submicrometer diameter and erbium source by granulating using a spray drier. The average diameter of the granulated powders is 50 μ and about 150 times as large as that of the fumed silica. The silica powders are packed in a rubber mold and are compressed by CIP. It is found from thermal analysis that the compressed powders can be degreased PVP at 600°C. After degreasing at 600°C, the compressed powders are sintered by a sintering process using an electric furnace or a gas burner. The compressed powders can be vitrified by using not the electric furnace but the gas burner. The existence of Er ions in the glass sintered by the gas burner is confirmed from UV-VIS spectra.

Photosensitive organic-titania hybrid materials have been prepared from metal alkoxides and various organic ester compounds with \(C{=}C\) double bonds. The refractive index of the film increases with the decrease of the concentration of the organic ester compound, and the highest refractive index of 1.62 is obtained when 2-hydroxymethyl acrylate (HOA) is used as the organic ester and the molar ratio of HOA to Ti is 0.5. The material with the highest refractive index is exposed to femtosecond pulse using the multi-beam laser interference technique. After laser irradiation, the irradiated parts of the material are photopolymerized and periodic structures can be obtained by development of the unirradiated parts. In the case of laser irradiation of 120 μ J total energy for 5 min, the periodic structure obtained corresponds to 2D photonic crystal structure which is composed of two parts; the material with the highest refractive index and the air.

In order to produce an excellent abrasive, a fabrication method for cocoon shaped silica particles has been studied. The particles are prepared from TMOS, water, ammonia and methanol by a sol–gel method. The method is to add the methanol solution of TMOS at a constant supply rate to a mixture of water, ammonia and methanol. Effects of various reaction conditions such as temperatures, supply rates of TMOS, and amounts of TMOS are studied on the diameter and shape of the particles. The diameter and shape are resulted in depending strongly on temperatures. High temperature makes particles with the high aspect ratio and the small diameter. And the mechanism of forming the cocoon shaped particle is also discussed. It is concluded that the primary particles are generated at the beginning stage of reaction and two of them become the cocoon shaped particle. For the polishing efficiency, particles have high polishing efficiency with the diameter between 40 nm and 210 nm. As a result, best diameter of particles for abrasive is 40–100 nm with respect to polishing efficiency and surface finish.

Photosensitive hybrid titania films have been prepared from titanium butoxide modified with β-diketone and methacrylic acid. When this film is exposed to UV light, the β-diketonato chelate from the alkoxide and β-diketone is dissociated, and the unsaturated hydrocarbon of methacrylic acid is polymerized. These structural changes in the gel film have led to a difference between the solubility of irradiated and unirradiated parts in the film; therefore, a fine patternable hybrid titania film has been fabricated.

We report on a fabrication of photonic crystal structures in organic-inorganic hybrid films by a laser interference technique. Films containing the methacrylic group, which is photopolymerable by an adequate laser light, are prepared using a sol-gel technique from a mixture of organosilicate alkoxide and zirconium alkoxide modified by methacrylic acid. For the photopolymerization, the coated films on glass substrate are exposed to the interference light which is arranged with a square lattice in about 1 μm spacing. From microscopic images of microstructures produced by the photopolymerization, the influence of changes in conditions such as pre-bake temperature, photoinitiator and irradiation energy (laser power and duration time) on periodic structure is investigated. Adjusting the conditions, 2D and 3D photonic crystal structures with the micrometer-order period are formed in organo-silicate-zirconate hybrid materials.

A new hybridized process for preparing optical fibers has been developed. The process consists of overcladding a VAD-derived core rod with commercial silica powder by cold isostatic pressing (CIP) technique. Single-mode optical fibers were fabricated by the process which used the core rod having a ratio of core to cladding radius of 3 and silica powder of average particle diameter of 10μm. The losses were 0.36dB/km at 1.3μm and 0.23dB/km at 1.55μm. The points for the process are following; (1) Silica powder was granulated by spray dryer from slurry containing poly-vinyl-alcohol (PVA) to be packed uniformly into a rubber mold for CIP forming. (2) To prevent the core rod from breaking in the compression, a rubber mold with a structure in which both ends of the core rod were pressed by hydrostatic pressure was used. This CIP process provided the hybridized soot preform which consisted of the core rod and a porous body around it from silica powder in one step. (3) It was very important that 10μm silica powder was used because it was easy to purify into high-purity glass. (4) To remove PVA which was added in granulating, heat treatment was carried out at 500°C in an atmosphere of dry air. The heat-treated porous body containing 25ppm carbon was consolidated into the overcladding glass for low-loss optical fibers. Further, a relation between the pore diameter and purification of the porous body was studied. As a result, pores with more than 0.2μm diameter were presumed to be required for making high-purity glass by chlorine purification.

A CIP hybridized process for fabrication of a single-mode optical fiber with a small core eccentricity error has been studied. As a result, a process for fabrication of an optical fiber with a core eccentricity error of less than 0.3μm has been developed. In this study, we also clarified the following. (1) A hybridized soot preform with an outer diameter noncircularity of less than 0.4% was prepared by packing granular silica particles with a high packing density into a rubber mold with a thick wall. (2) A soot preform with a noncircularity of less than 0.06% and an outer diameter fluctuation of less than 0.11mm was made by means of a grinding treatment in which the outer surface of the soot preform was ground around a core rod. (3) A single-mode optical fiber with a core eccentricity error of less than 0.3μm was also fabricated from the soot preform ground above.

A new hybridized process for preparing optical fibers has been developed. The process consists of overcladding a VAD-derived core rod with commercial silica powder by extrusion shaping technique. The single-mode optical fiber was fabricated by the process which used a core rod having a ratio of core/cladding diameter of 1/3.15 and silica powder of average particle diameter of 10μm. The transmission losses were 0.40dB/km at 1.3μm and 0.26dB/km at 1.55μm. In this study, we also clarified as follows: (1) The lamination which occurs at extrusion can disappear by using an extension cylinder with bolts. (2) Bubbles in the optical fiber preform do not occur by using plastic material in which surface active agent is added in the mixture consisting of silica powder, water and methyl-cellulose. (3) The soot preform which consists of a core rod and a porous body around it can be extruded by using an extruder which is reconstructed a commercially available one for hybridized extrusion.