US 4,227,907 AGranted

Laser photochemical synthesis coating of optical fiber

AssigneeThe United States of America as represented by the Secretary of the Army

InventorJames A. Merritt

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Abstract

Disclosed is a method to prepare and coat an optical fiber with Si.sub.3 ub.4. The Si.sub.3 N.sub.4 is synthesized from SiF.sub.4 +NH.sub.3 and/or SiH.sub.4 +NF.sub.3 by laser photochemical reaction (LPR) techniques in a controlled atmosphere chamber. The silicon fiber which is a representative optical fiber is drawn from a preform at about 2000.degree. C. in a standard fiber drawing furnace. Immediately after drawing of fiber, the fiber is passed through a chamber with a controlled atmosphere containing SiX.sub.4 and NX.sub.3 gases, wherein X equals hydrogen or fluorine. A laser is used to irradiate the atmosphere and the Si.sub.3 N.sub.4 is coated on the optical fiber to a thickness of about 0.02-0.20 micrometer which hermetically seals the fiber and enhances and maintains the mechanical strength thereof.

Claims2

Dependent claims

In a method of producing an optical fiber of high mechanical strength from a high purity fused silica preform rod wherein the preform rod is heated to its yield point at about 2000.degree. C., a fiber is drawn from the heated preform, and the drawn fiber is immediately hermetically sealed with a layer of silicon nitride of about 0.02 to about 0.20 micrometer thickness, the improvement in said method of hermetically sealing the drawn fiber at room temperature by a laser photochemical reaction process which comprises:

(a) placing a drawn silicon fiber in a reaction chamber provided with a salt window transparent to laser radiation;
(b) introducing and maintaining a controlled atmosphere of SiX.sub.4 and NX.sub.3 gases, wherein X is selected from hydrogen and fluorine, in said reaction chamber and;
(c) irradiating said controlled atmosphere with a predetermined wavelength of a laser to produce Si.sub.3 N.sub.4 which coats and hermetically seals said drawn silicon fiber with a layer of said Si.sub.3 N.sub.4 of about 0.02 to about 0.20 micrometer thickness.

Dependencies are inferred from the claim text.