Method for fabricating an optical waveguide

• US 5,556,442 A
• Filed: 06/23/1994
• Issued: 09/17/1996
• Est. Priority Date: 12/06/1991
• Status: Expired due to Fees

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Ishikawa, Shinji, Saito, Masahide, Aikawa, Haruhiko, Hirose, Chisai, Urano, Akira, Kanamori, Hiroo
• Primary Examiner(s): Czaja, Donald E.
• Assistant Examiner(s): Griffin, Steven P.
• Application Number:
  US08/264,301
• Time in Patent Office: 817 Days
• Field of Search: 65/17.3, 65/17.4, 65/17.6, 65/60.1, 65/60.2, 65/60.4, 65/60.5, 65/385, 65/386, 65/399, 65/427, 65/429, 65/31, 65/391, 427/446, 427/162, 427/419.6, 427/419.7, 427/224, 427/314, 427/372.2, 427/375, 385/123, 385/126, 385/127, 385/128, 385/129, 385/130, 385/131, 385/132, 156/62.2
• US Class Current: 65/17.4
• CPC Class Codes: C03B 19/14 by gas- or vapour- phase reaction processes
• CPC Class Codes: C03B 19/1453 Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
• CPC Class Codes: C03C 17/02 with glass C03C17/34, C03C17/44 take precedence
• CPC Class Codes: G02B 2006/12038 Glass (SiO2 based materials)
• CPC Class Codes: G02B 6/13 Integrated optical circuits characterised by the manufacturing method

Abstract

A process for forming film structure using Flame Hydrolysis Deposition (FHD) in which (1) glass soot is deposited on a substrate via FHD to form a first porous vitreous layer having a first bulk density, (2) a second porous vitreous layer having a second bulk density that is larger than the first bulk density is formed from a portion of the first porous vitreous layer, and (3) a third porous vitreous layer having a third bulk density is formed by depositing glass soot containing a refractive index increasing dopant on the second porous vitreous layer by FHD. The first, second and third porous vitreous layers are then heated to form an undercladding layer and a core layer, the undercladding layer being formed from the first and second porous vitreous layers and the core layer being formed from the third porous vitreous layer.

Claims

1. A process for forming an optical waveguide, comprising the steps of:

(a) depositing glass soot on a substrate by Flame Hydrolysis Deposition to form a first porous vitreous layer having a first bulk density,

(b) forming a second porous vitreous layer having a second bulk density in a top surface of the first porous vitreous layer, where the second bulk density is larger than the first bulk density and a surface of said second porous vitreous layer is exposed in the step (b);

(c) depositing glass soot containing a refractive index increasing dopant on the second porous vitreous layer by Flame Hydrolysis Deposition to form a third porous vitreous layer having a third bulk density; and

(d) heating the first, second, and third porous vitreous layers to form an under cladding portion and a core portion comprising transparent glass layers, the under cladding portion being formed from the first and second porous vitreous layers and said core portion being formed from said third porous vitreous layer.

2. A process for forming an optical waveguide according to claim 1 further comprising the steps of:

(e) etching the core portion to form an optical waveguide pattern and expose a part of said under cladding portion;

(f) depositing glass soot on the optical waveguide pattern and the exposed part of the under cladding layer by Flame Hydrolysis Deposition to form a fourth porous vitreous layer; and

(g) heating the fourth porous vitreous layer to form an over cladding layer comprising a transparent glass layer and having a fourth bulk density.

3. A process for forming an optical waveguide according to claim 1, wherein

the refractive index increasing dopant comprises at least one compound selected from a group consisting of GeO₂, P₂ O₅, and Al₂ O₃.

4. A process for forming an optical waveguide according to claim 1 wherein

the second bulk density is above about 0.3 g/cm³.

5. A process for forming an optical waveguide according to claim 1, wherein

the second bulk density is larger than the third bulk density.

6. A process for forming an optical waveguide according to claim 1, wherein

a glass synthesizing burner is used for said Flame Hydrolysis Deposition, and

a heating burner which is separate from the glass synthesizing burner is used to heat the substrate.

7. A process for forming an optical waveguide according to claim 1, wherein

the Flame Hydrolysis Deposition is conducted by using a glass synthesizing burner,

the glass synthesizing burner is fed with a fuel gas and a raw material gas in step (a) and (c),

the forming of said second porous vitreous layer in said step (b) is conducted by said glass synthesizing burner fed with a fuel gas, and

an amount of fuel gas fed to the glass synthesizing burner during said step (b) is greater than the amount of fuel gas fed to the glass synthesizing burner during said step (a).