Tri-layer ceramic optical fibers and method of making

Patent metadata

Field	Value
Publication number	US-2025060529-A1
Application number	US-202418802701-A
Country	US
Kind code	A1
Filing date	Aug 13, 2024
Priority date	Aug 14, 2023
Publication date	Feb 20, 2025
Grant date	—

Abstract

A tri-layer optical fiber. The fiber has a core which is preferably a single crystal and outer cladding, to reduce signal loss. The cladding process begins with high porosity particles, and is known to introduce porosity in the cladding and at the core/cladding interface. The porosity increases refraction and signal loss. The invention interposes a film layer intermediate the core and cladding. The film layer is sputter coated and preferably of the of same material as the cladding. The film prevents diffusion of the porous cladding into the core, minimizing porosity and improving signal transmission.

First claim

What is claimed is:

1 . An optical fiber comprising:
a crystalline core; a ceramic cladding circumscribing the core; an insulative film intermediate and separating the core and cladding and substantially preventing the grain boundary of the core from growing onto the cladding during a cladding process.

2 . A fiber according to claim 1 wherein the film is a sputter coated film.

3 . A fiber according to claim 2 wherein the film is a ceramic film.

4 . A fiber according to claim 3 wherein the film is a YAG film.

5 . A fiber according to claim 4 wherein the film has a thickness of 10 nm to 5000 nm.

6 . A fiber according to claim 4 having a diameter of 20 microns to 5 mm

7 . An optical fiber comprising:
a positively doped crystalline core; a ceramic cladding circumscribing the core; a film intermediate and separating the core and cladding and substantially preventing the grain boundary of the core from growing onto the cladding during a cladding process.

8 . A fiber according to claim 7 wherein the core comprises YAG crystalline material.

9 . A fiber according to claim 8 wherein the core comprises a single YAG crystal.

10 . A fiber according to claim 9 wherein the film comprises amorphous YAG.

11 . A fiber according to claim 10 wherein the cladding comprises YAG.

12 . A fiber according to claim 11 wherein the cladding comprises polycrystalline YAG.

13 . A fiber according to claim 7 wherein the core, film and cladding comprise a mutually identical material.

14 . A method for making a tri-layer optical fiber comprising, in order, the steps of:
sputter coating crystal particles onto a crystalline core to encase the crystalline core with an insulative film; coextruding the core and film with cladding material to form a tri-layer cladded fiber; and sintering the tri-layer cladded fiber to reduce porosity in the cladding.

15 . A method according to claim 14 furthering comprising the step of hot isostatically pressing the tri-layer fiber to further reduce porosity of the cladding.

16 . A method according to claim 15 wherein the step of sputter coating an insulative film comprises the step of sputter coating an amorphous insulative film.

17 . A method according to claim 16 wherein the step of sputter coating the crystal particles to form an insulative film on the crystalline core comprises cathode sputter coating.

18 . A method according to claim 17 wherein the film has a thickness ranging from of 10 nm to 5000 nm.

19 . A method according to claim 18 wherein the core comprises a single YAG crystal.

20 . A method according to claim 19 wherein the core, particles and cladding comprise a mutually identical YAG material.

Assignees

• Us Gov Air Force

Inventors

• Kim Hyunjun
• Hay Randall
• Averett Kent
• Bowers Cynthia
• Gray Benjamin
• Sirn Brian

Classifications

• C23C14/34

  Sputtering · CPC title

• C23C14/08

  Oxides (C23C14/10 takes precedence) · CPC title

• G02B6/03694 Primary

  Multiple layers differing in properties other than the refractive index, e.g. attenuation, diffusion, stress properties · CPC title

• C04B2235/6567

  Treatment time · CPC title

• C04B2235/6565

  Cooling rate · CPC title