Lucent Technologies Inc.

Fitel USA Corporation

At&t Bell Laboratories

Agere Systems Inc.

Furukawa Electric Na

Suhas Dattatreya Bhandarkar

John Burnette MacChesney

David Wilfred Johnson

Thomas Edward Stockert

Edwin Arthur Chandross

Michael Philip Bohrer

Yoram De Hazan

Thomas Michael Putvinski

David W Johnson, Jr

Debra Anne Fleming

Glen Robert Kowach

Harish C Chandan

John C Alonzo

Henry Du

Frank J McNally

Deok-Yang Kim

Charles C Bahr, Jr

Silica sol techniques are described for making thick silica or silica based films useful for planar optical waveguides. The process involves coating of a colloidal silica sol onto a substrate, drying the sol, and consolidating the dried sol to form the planar waveguide. Coating is performed in a simple operation, either by dipping, or preferably by spin coating. In a preferred embodiment the substrate is coated with a wetting agent prior to spin coating. It is found that the wetting agent substantially improves the thickness uniformity of the layer. Thick waveguide layers may be produced by repeating the coating process one or more times to produce a layer with the desired thickness. Buried waveguides are produced by forming a doped core layer, patterning the doped core layer and using the coating technique of the invention to form the cladding material.

Manufacture of planar waveguides using sol-gel techniques

The use of large dense vitreous spherical (LDVS) silica powders for making sol-gel silica bodies has been found to have important advantages. Among these are higher gel strength, higher silica loading, more rapid aging and drying of the gel, a reduction in the amount of organic additives leading to reduced process time required for organic burn-off, and easier removal of contaminant particles due to their larger size. It was also discovered that combining LDVS particles with conventional non-spherical, lower density, aggregate particle mixtures, further improves the process.

Manufacture of silica bodies using sol-gel techniques

The use of silica powders having large particle sizes in making sol-gel silica bodies has been found to have important advantages. Among these are higher gel strength, higher silica loading, more rapid aging and drying of the gel, a reduction in the amount of organic additives leading to reduced process time required for organic burn-off, and easier removal of contaminant particles due to their larger size. It was also discovered that spherical particle morphology contributes to the improved properties.

A silica sol-gel fabrication process is provided which allows improved control of the shrinkage that takes place during the drying of a gel body. In particular, the invention makes it possible to attain extremely low shrinkage through the completion of the drying stage, e.g., below 1% linear shrinkage, in relatively large sol-gel bodies of (dry weight) 1 kg or more, typically 10 kg or more, or even 40 kg or more, compared to the much higher shrinkages typically encountered. Specifically, use of a particular polymeric additive makes it possible for a gel body to experience linear shrinkage at least 55% less than an identical process without the polymeric additive.

Process for fabricating sol-gel article involving low-shrinkage formulation

A sol-gel process for fabricating bulk, germanium-doped silica bodies useful for a variety of applications, including core rods, substrate tubes, immediate overcladding, pumped fiber lasers, and planar waveguides, is provided. The process involves the steps of providing a dispersion of silica particles in an aqueous quaternary ammonium germanate solution&mdash;typically tetramethylammonium germanate, gelling the dispersion to provide a gel body, and drying, heat treating, and sintering the body to provide the germanium-doped silica glass.

Sol-gel process for fabricating germanium-doped silica article

A silica-water dispersion suitable for use as a sol for sol-gel fabrication is produced from a silica-water mixture with addition of alkaline agent. The agent functions to increase viscosity so as to improve dispersing efficiency during shear mixing.

Process entailing sol-gel production of silica glass

Silica sols exhibiting desirable yield-dilatancy are fabricated. A mixture comprising silica, water, and a pH-adjusting agent is provided, and the mixture is shear-mixed. The desirable properties of the resultant sol are attained by using a concentration of pH-adjusting agent that provides a viscosity within a particular range during shear mixing. The requisite pH range, however, changes depending on the properties of the silica mixture. A discovered technique for determining this changing pH range is by selecting the pH based on the silica surface area per unit volume of the mixture.

Processing entailing sol-gel fabrication of silica glass

The invention reflects discovery of a liquid phase doping technique that, unlike previous techniques, exhibits very little fluorine depletion upon subsequent heating. The invention involves the steps of providing a silica sol comprising a tetraalkylammonium hydroxide and a di-, tri-, or tetraalkylammonium fluoride, the sol having pH of about 10 to about 14, adding a gelling agent to the sol to induce gelation, casting or extruding the sol to form a gel body, and then drying, heat treating, and sintering the body. Advantageously, the fluorine-containing compound is tetramethylammonium fluoride.

Process for fabricating fluorine-doped sol-gel article

A silica body useful for forming an optical fiber preform exhibits an ultimate strength of at least 20 MPa at 10 wt. % water loss. The body attains this strength, it is believed, by precipitation of silica at the contact sites of adjacent silica particles, thereby forming neck regions. The resultant network provides the strength to the gel body, such that the body is capable of being dried under more severe conditions than a gel body formed by previous sol-gel methods and is also more robust toward handling. The controlled precipitation is attained by inducing gelation and initiating drying at a pH of about 10.5 or higher, at which silica remains highly soluble. By gelling and drying at this pH level, the solubilized silica appears to precipitate in a controlled manner at the point of contact of adjacent silica particles, since such sites are the minimum free energy sites for precipitation.

Method for forming article using sol-gel processing

A method for forming a dielectric oxide layer on selected areas of a substrate is disclosed. The dielectric oxide layer is formed on selected areas of the substrate using a sol process. The substrate has an area of a first material and an area of a second material which is different from the first. The first material is coated with a layer of a first compound. The layer of the first compound has a hydrophobic top surface. The second material is coated with a layer of a second compound. The layer of the second compound has a hydrophilic top surface. A layer of hydrous oxide is formed over the second compound by applying an aqueous sol solution on the surface of the substrate. The substrate is then heated to remove the first compound and the second compound from the surface of the substrate. Thereafter, the substrate with the layer of hydrous oxide thereon, is sintered to form the dielectric oxide layer.

Process for forming patterned dielectric oxide films

In accordance with the invention a planar waveguide device is fabricated by providing a substrate with an undercladding, depositing a particulate layer of core glass on the undercladding, consolidating the particulate layer by low temperature viscous sintering, patterning the consolidated layer to form an optical waveguide and applying an overcladding. The glass layers can be deposited quickly and economically by slurry dipping, centrifuging or electrophoresis. In a preferred embodiment the substrate is silicon, and the core glass is sodium-boro-silicate.

Method for making planar optical waveguides

Incidence of breakage in optical fiber drawn from sol-gel produced preforms is reduced by treatment of the still-porous glass by use of a chlorine-containing, oxygen-free gas mixture. Improved satisfaction of proof-rest requirements to at least 100 kpsi is assured by size reduction of unassimilated discrete particles in the fiber.

Manufacture of high proof-test optical fiber using sol-gel

Optical fiber drawn from preforms including sol-gel-derived glass is found to contain small refractory particles of the order of a micron in size. These particles initiate fiber breaks with the result that fiber may not meet proof-test tensile strength requirements. An effective separation method relies upon density and/or size difference from suspended sol particles for separation in the ungelled sol. A preferred separation procedure is centrifugation.

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Glen Gardner, NJ, United States of America

Suhas Dattatreya Bhandarkar