Hughes Aircraft Company

Antonio C Pastor

Ricardo C Pastor

Luisa E Gorre

Remedios K Chew

Gregory L Tangonan

Joseph A Wysocki

Anthony L Gentile

Bor-Uei Chen

Shi-Yin Wong

Roger R Turk

Arlie G Standlee

Kaneto Arita

James A Harrington

M Robinson

A preform for preparation of optical fibers is prepared by inserting a rod of a higher index of refraction fluoride glass into the bore of a hollow cylinder of a lower index of refraction fluoride glass fiber. This preform precursor is processed to collapse the hollow cylinder inwardly to form a composite preform having a high-refractive index core and a low-refractive index casing. The preparing of the glasses and processing to a preform are accomplished in a reactive environment that reacts and removes oxygen and hydrogen containing species from the glass, the reactive environment being, for example, Cl.sub.2, CCl.sub.4, SF.sub.6, BF.sub.3, CF.sub.4, or the decomposition products of a liquefied solid fluorocarbon. The preform is then drawn to an optical fiber.

Preparation of fluoride glass optical preforms and fibers

Cylindrical rods of titanium carbide or other refractory material with uniform, high density are prepared by hot pressing plates from powders of the material, with a uniaxial pressing pressure applied to the broad faces of the plate. Bars of square cross section are then cut from the plate and machined to cylindrical rods. The process is particularly suited to the preparation of refractory material preforms to be used in single crystal growth by the float zone method. Titanium carbide rods having a highly uniform density of about 96% that of the theoretical maximum can be readily prepared and then grown into titanium carbide crystals.

Fabrication of rods of uniform high density from powders of refractory

Fine single crystals of low-melting point materials are prepared by slowly withdrawing a glass crystal growth capillary tube containing the material from a heating apparatus which precisely maintains the molten material at a temperature just above its melting point. Temperature control of the molten material in the crystal growth tube, prior to solidification, is attained by enclosing the crystal growth tube in a temperature control tube containing the molten material being solidified. Preferably, the inside diameter of the temperature control tube is slightly larger than the outside diameter of the crystal growth tube, and both tubes reach into a reservoir of the molten material to be grown as a crystal, so that the molten material is drawn upwardly into the crystal growth tube and the space between the crystal growth tube and the temperature control tube by capillary action.

Growth of glass-clad single crystal fibers

A method is disclosed for growing thermally unstable ferroelectric materials having the formula MH.sub.2 XO.sub.4, where M is potassium, rubidium, cesium or ammonium; H is hydrogen or deuterium and X is phosphorus or arsenic. The ferroelectric material is heated to melt temperature in a constant volume cylindrical chamber (10) which is moisture-free. Improved crystal formation is accomplished by axially cooling the melt from the bottom end (18) of the chamber by thermal conduction along the chamber longitudinal axis predominantly and only minimally by radial thermal conduction through the sides (16) of the chamber. The axial cooling produces a crystal interface which is flat and perpendicular to the chamber axis and which gradually progresses toward the chamber top to provide uniform growth of a single crystal of ferroelectric material.

Method for growing single crystals of thermally unstable ferroelectric

An apparatus and method pulling a shaped crystalline fiber of a given crystal-forming material from a liquid reservoir of the material. The apparatus includes a vessel in which the liquid material is maintained as a liquid reservoir at a temperature above the melting point or crystal-forming temperature of the material. A die is provided having an inner-tubular surface which includes a crystal shaping portion which is tapered. The liquid flows from the reservoir through the die so that the liquid flows from the narrow end of the shaping portion to the wide end of the shaping portion. The temperature of the liquid crystal growth material is selectively lowered at the top end of the die to form crystalline material which is continually pulled from the crystal-liquid interface. The apparatus is operated to maintain the crystal-liquid interface within the crystal shaping portion of the die to provide accurate shaping of the crystal by the tubular surface and to maintain accurate alignment of the crystal fiber with the die.

Shaped crystal fiber growth method

An improvement of the method for preparing cupric ion-free cuprous chloride powder in which copper metal is added to a highly acidified solution of cupric chloride to reduce the cupric ions to cuprous ions and oxidize the copper metal to cuprous ions. The improvement involves applying an electromotive force to the solution by immersing interconnected copper and platinum electrodes in the solution. The electromotive force is applied only after the reduction of cupric ions is near completion. The electromotive force is applied for a sufficient time to insure essentially complete reduction of cupric ions in the solution. Cuprous chloride is then separated from the cupric ion-free solution by evaporation and isolated by conventional techniques to provide an improved cuprous chloride powder product which is essentially free of cupric ions. The electromotive force is also applied during the evaporation of the acidified solution to prevent possible cupric ion formation. Removal of anion impurities from the cupric ion-free cuprous chloride powder is also disclosed.

Method for preparing cupric ion-free cuprous chloride

This invention provides a method for conversion of congruently melting polycrystalline fibers to single crystal fibers. The method is particularly useful for production of fibers ranging from about 30 .mu.m to about 1,000 .mu.m in diameter, which are capable of infrared (IR) transmission and of functioning in nonlinear optical applications. The polycrystalline fiber is converted to a single crystal fiber by creating a melt zone near one end of said polycrystalline fiber and then causing said melt zone to travel a length of said polycrystalline fiber at least once, so that the fiber continuously melts and recrystallizes into a single crystal along the length so that such length becomes one continuous crystal. In another embodiment of the invention, the method described above is utilized to improve the surface characteristics of a single crystal. In yet another embodiment of the invention, the method disclosed above is utilized to produce a fiber comprised of a polycrystalline core surrounded by a single crystal sleeve or large grained crystal sleeve which evidences single crystal behavior. This method is particularly useful for production of fibers ranging from about 30 .mu.m to 1,000 .mu.m in diameter, which are capable of infrared (IR) transmission. If the sleeve is a sufficiently large proportion of the fiber produced, this method is particularly useful for production of fibers which may be capable of functioning in nonlinear optical applications.

Fabrication of single crystal fibers from congruently melting

The specification discloses new and improved processes for forming water-free metal or non-metal oxide materials, which may then be melted and formed into optical components in vitreous or crystal form, which are free of the hydrogen-impurity absorption in the near infrared wavelength range. In one process, a water-free oxide is prepared by reacting a chosen nonpolar compound containing the desired metal or non-metal with an aprotic oxygen-containing compound to form the oxide as a precipitate in a chosen aprotic nonaqueous liquid solvent which provides a water-free environment during the formation of the oxide, to prevent the inclusion of water and water-derived impurities in the oxide as formed. Then the oxide-containing precipitate is subjected to a reactive atmosphere process by exposing the powder to a chosen gas phase reactive atmosphere comprising atomic halogen at a predetermined elevated temperature for a predetermined period of time, to remove traces of water and water-derived impurities from the oxide.

Process for preparation of water-free oxide material

The specification discloses new and improved processes for forming water-free metal or non-metal oxide materials, which may then be melted and formed into optical components in vitreous or crystal form, which are free of the hydrogen-impurity absorption in the near infrared wavelength range. In one process a water-free oxide is prepared by reacting a chosen organic compound containing oxygen bonded to an atom of the metal or non-metal, with a chosen organic acid anhydride to form an intermediate product which is then decomposed to form the desired oxide and to simultaneously regenerate the organic acid anhydride. The regenerated organic acid anhydride reacts with and removes traces of water and water-derived impurities during the formation of the desired oxide and prevents the inclusion of these impurities in the oxide as formed.

The specification discloses a process for forming a water-free rare earth oxychloride powder by exposing a water-containing rare earth oxide powder to a reactive atmosphere of chlorine and oxygen at 1000.degree. C. for 24 hours to remove water impurities from the oxide powder and to simultaneously convert the oxide powder to the oxychloride powder.

Process for preparation of water-free oxychloride material

The specification discloses a process for converting the surface layer of a body of vitreous silica to the more stable crystalline form of silica known as cristobalite. The surface of the body of vitreous silica is exposed to a gas phase reactive atmosphere comprising atomic iodine at a predetermined elevated temperature for a predetermined period of time to convert the surface layer of the vitreous silica to polycrystalline cristobalite and thus passivate and enhance the stability of the treated surface. The disclosed process is particularly useful for forming improved crucibles, such as those used in crystal growth from a melt.

Process for surface conversion of vitreous silica to cristobalite

An apparatus and process for growing large single halide crystals that are ultra pure is described. A bicameral apparatus and process is employed in which the crystals are grown in a reactive chamber positioned within an inert chamber. A radial seal is provided on the furnace chamber to facilitate the reaction and maintenance of an inert atmosphere around and about a crystal growth assembly wherein crystals are grown from a melt under a reactive atmosphere.

Bicameral mode crystal growth apparatus and process

The specification describes a process for depositing a film of controlled composition on a substrate by using a metallo-organic photoresist in which the organic portion is combusted by heating in a reactive atmosphere to leave a residual deposit of a desired substance on the substrate. The film may be formed as a patterned or unpatterned layer. In addition, the residual deposit may be subsequently subjected to a chemical reaction to alter its composition.

Process for depositing a film of controlled composition using a

Disclosed is a method of producing metal halide and metal chalcogenide crystals for infrared window application which exhibits a high conversion ratio.

Method of growing metal halide and chalcogenide crystals for use as

A process for suppressing the out-diffusion of Li.sub.2 O from LiNbO.sub.3 and LiTaO.sub.3 waveguide structures by exposing the structures to a Li.sub.2 O-rich environment at sufficient vapor pressure that Li.sub.2 O diffuses into the structure as a compensation process and a solid-solid surface interaction occurs. In one embodiment of the invention, the out-diffusion of Li.sub.2 O from LiNbO.sub.3 and LiTaO.sub.3 crystals into which Ti has been diffused is eliminated by annealing the structure in a high purity powder of LiNbO.sub.3 or LiTaO.sub.3. In a second embodiment, the Li.sub.2 O out-diffusion is partially suppressed by annealing the structure in molten LiNO.sub.3. In a third embodiment of the invention, a waveguide structure comprising a Li.sub.2 O-rich guiding layer is formed by annealing LiNbO.sub.3 or LiTaO.sub.3 crystals in a high purity powder of LiNbO.sub.3 or LiTaO.sub.3, which not only suppresses Li.sub.2 O out-diffusion but also promotes Li.sub.2 O in-diffusion into the crystals.

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Santa Monica, CA, United States of America

Antonio C Pastor