Method of forming planar optical waveguides

• US 3,934,061 A
• Filed: 07/18/1973
• Issued: 01/20/1976
• Est. Priority Date: 03/30/1972
• Status: Expired due to Term

• Current Assignee: Corning Glass Works Inc. (Corning Incorporated)
• Original Assignee: Corning Glass Works Inc. (Corning Incorporated)
• Inventors: Keck, Donald B., Schultz, Peter C.
• Primary Examiner(s): Martin, William D.
• Assistant Examiner(s): Schmidt, William H.
• Application Number:
  US05/380,482
• Time in Patent Office: 916 Days
• Field of Search: 65/18, 65/60, 117/23, 117/70 B, 117/124 A, 117/125, 117/169 A, 350/96 WG, 427/163, 427/165, 427/167, 427/193, 427/223, 427/255, 427/402, 427/419
• US Class Current: 427/163.2
• CPC Class Codes: C03B 19/14 by gas- or vapour- phase reaction processes
• CPC Class Codes: C03B 37/014 made entirely or partially by chemical means , e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] C03C17/02 takes precedence
• CPC Class Codes: C03C 17/02 with glass C03C17/34, C03C17/44 take precedence
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: C03C 23/0025 by a laser beam
• CPC Class Codes: G02B 6/13 Integrated optical circuits characterised by the manufacturing method

Abstract

A method of producing a planar optical waveguide by applying to at least a portion of one flat surface of a substantially flat glass substrate having a predetermined desired index of refraction a first coating of glass having an index of refraction greater than that of said glass substrate. Thereafter a second coating of glass having an index of refraction less than that of the first coating of glass is applied over the exposed surface of the first coating of glass. The thickness of the first coating of glass being determined as a function of the highest mode order and the wavelength of light to be propagated within a waveguide having infinite width, and the indices of refraction of the substrate and each of the applied coatings.

Claims

1. A method of forming a planar optical waveguide for light propagation comprising the steps of:

providing a substantially flat glass substrate having a predetermined desired index of refraction,

applying a first coating of glass having an index of refraction greater than that of said glass substrate to at least a portion of one flat surface of said substrate to thereby form a film thereon, said first coating of glass having an outer exposed surface substantially parallel to said one flat surface of said substrate, the thickness of said first coating being defined by said surfaces, the width of said first coating being the dimension perpendicular to both said thickness and the light propagation axis of said first coating, and

applying a second coating of glass having an index of refraction less than that of said first coating of glass over at least said outer exposed surface of said first coating of glass to thereby form a film thereon, the thickness of said first coating of glass for any desired finite width thereof being equal to or less than the thickness a of a coating having an infinite width, thickness a being determined in accordance with one of the following equations

for TM_Om modes where m is an even integer ##EQU13## for TM_Om modes where m is an odd integer ##EQU14## for TE_Om modes where m is an even integer ##EQU15## for TE_Om modes where m is an odd integer ##EQU16## where m ≦

10 and is the highest mode order to be propagated within a waveguide the first coating of which has a thickness a and an infinite width, λ

is the wavelength of light to be propagated within said waveguide the first coating of which has a thickness a and an infinite width, n₂ is the index of refraction of said first coating, and one of n₁ and n₃ being the index of refraction of said substrate while the other of n₁ and n₃ being the index of refraction of said second coating of glass, said thickness of said first coating of glass being so determinable where the propagation constant of said waveguide is equal to or less than K₁, where K₁ is greater than K₃, where

space="preserve" listing-type="equation">K.sub.1 = 2π

n.sub.1 /λ

,

and

space="preserve" listing-type="equation">K.sub.3 = 2π

n.sub.3 /λ

the thickness of each said substrate and said second coating of glass being at least about two times the thickness of said first coating of glass.

2. The method of claim 1 wherein said first coating of glass is formed by the steps comprising:

depositing a layer of glass soot on at least a portion of one flat surface of said substrate by flame hydrolysis, and

heating said soot until it sinters.

3. The method of claim 2 wherein said second coating of glass is formed by the steps comprising:

depositing a second layer of glass soot over at least said outer exposed surface of said first coating by flame hydrolysis, and

heating said first coating and said second layer of glass soot until said second layer of soot sinters.

4. The method of claim 1 wherein said first and second coatings of glass are formed by the steps comprising:

depositing a first layer of doped fused silica soot over at least a portion of one flat surface of said substrate by flame hydrolysis,

depositing a second layer of fused silica soot over at least said outer exposed surface of said first soot layer by flame hydrolysis, and

heating the structure so formed until said first and second layers of soot sinter forming said first and second coatings respectively.

5. The method of claim 4 wherein said first coating is fused silica doped with at least one material selected from the group consisting of titanium oxide, tantalum oxide, tin oxide, niobium oxide, zirconium oxide, aluminum oxide, lanthanum oxide, and germanium oxide.

6. The method of claim 4 wherein said first coating is fused silica doped with not more than 20 percent by weight titanium oxide.

7. The method of claim 1 wherein the width to thickness ratio of said first coating is equal to or less than ten.

8. The method of claim 1 wherein the first or second coating of glass is applied by chemical vapor deposition.

9. The method of claim 1 wherein the first or second coating of glass is formed by applying a glass frit and thereafter sintering said frit.

10. The method of claim 1 wherein said second coating is fused silica and said first coating is fused silica doped with not more than 40 percent by weight of dopant.

11. A method of forming a planar optical waveguide for light propagation comprising the steps of:

providing a substantially flat glass substrate having a predetermined desired index of refraction,

applying a first coating of a glass having an index of refraction greater than that of said glass substrate to at least a portion of one flat surface of said substrate to thereby form a film thereon, said first coating of glass having an outer exposed surface substantially parallel to said one flat surface of said substrate, the thickness of said first coating being defined by said surfaces, the width of said first coating being the dimension perpendicular to both said thickness and the light propagation axis of said first coating, and

applying a second coating of glass having an index of refraction substantially equal to that of said substrate over at least said outer exposed surface of said first coating of glass to thereby form a film thereon,

the thickness of said first coating of glass for any desired finite width thereof being equal to or less than the thickness a of a coating having infinite width, thickness a being determined in accordance with the following equation

space="preserve" listing-type="equation">2a/λ

(n.sub.2.sup.2 - n.sub.1.sup.2).sup.1/2 = m+1,

where m ≦

10 and is the highest mode order to be propagated within a wave-guide the first coating of which has a thickness a and an infinite width, λ

is the wavelength of light to be propagated within said waveguide the first coating of which has a thickness a and an infinite width, n₂ is the index of refraction of said first coating, and n₁ is the index of refraction of said substrate and said second coating of glass, said thickness of said first coating of glass being so determinable where the propagation constant of said waveguide is equal to or less than K₁, where

space="preserve" listing-type="equation">K.sub.1 = 2π

n.sub.1 /λ

,

and

the thickness of each said substrate and said second coating of glass being at least about two times the thickness of said first coating of glass.

12. The method of claim 11 wherein said first and second coatings of glass are formed by the steps comprising:

depositing a first layer of doped fused silica soot over at least a portion of one flat surface of said substrate by flame hydrolysis,

depositing a second layer of fused silica soot over at least said outer exposed surface of said first soot layer by flame hydrolysis, and

heating the structure so formed until said first and second layers of soot sinter forming said first and second coatings respectively.

13. The method of claim 12 wherein said first coating is fused silica doped with at least one material selected from the group consisting of titanium oxide, tantalum oxide, tin oxide, niobium oxide, zirconium oxide, aluminum oxide, lanthanum oxide, and germanium oxide.

14. The method of claim 12 wherein said first coating is fused silica doped with not more than 20 percent by weight titanium oxide.