OPTICAL CONVERTER AND METHOD FOR MANUFACTURING THE SAME

• US 20100067846A1
• Filed: 11/30/2007
• Published: 03/18/2010
• Est. Priority Date: 12/01/2006
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Tokushima, Masatoshi
• Granted Patent: US 8,170,383 B2
• Time in Patent Office: Days
• US Class Current: 385/14
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/136 by etching

Abstract

An optical converter comprises: a first waveguide, a second waveguide, and a tapered waveguide arranged between both the waveguides, wherein heights of a core of the first waveguide and a core of the second waveguide are different; both ends in a direction of wave guiding of a core of the tapered waveguide are respectively connected to the core of the first waveguide and the core of the second waveguide; cross-sectional shapes and refractive indexes of cores of two waveguides that are connected change continuously or in a stepwise manner at each connection part; and a cross-sectional shape and refractive index of the core of the tapered waveguide change continuously or in a stepwise manner along a direction of wave guiding.

Claims

1. An optical converter comprising:

a first waveguide, a second waveguide, and a tapered waveguide arranged between both the waveguides, wherein heights of a core of said first waveguide and a core of said second waveguide are different;

both ends in a direction of wave guiding of a core of said tapered waveguide are connected to said core of said first waveguide and said core of said second waveguide respectively;

cross-sectional shapes and refractive indices of cores of two waveguides that are connected change continuously or in a stepwise manner at each connection part; and

a cross-sectional shape and refractive index of said core of said tapered waveguide change continuously or in a stepwise manner along a direction of wave guiding.

2. The optical converter according to claim 1, wherein said core of the first waveguide and said core of the second waveguide have different widths.

3. The optical converter according to claim 1, wherein directions of wave guiding of two waveguides that are connected match at each connection part.

4. The optical converter according to claim 1, wherein width of said core of said tapered waveguide changes monotonically along a direction of wave guiding or is a combination of a portion that changes monotonically and a portion that is constant.

5. The optical converter according to claim 1, wherein height of said core of said tapered waveguide changes monotonically along a direction of said waveguide or is a combination of a portion that changes monotonically and a portion that is constant.

6. The optical converter according to claim 1, wherein bottom faces of said cores of said first waveguide, said second waveguide, and said tapered waveguide are all on the same plane.

7. The optical converter according to claim 1, wherein the length in a direction of wave guiding of said tapered waveguide is at least 10 times the larger of:

a difference between the width of said core of said first waveguide and the width of said core of said second waveguide, and a difference between the height of said core of said first waveguide and the height of said core of said second waveguide.

8. The optical converter according to claim 1, wherein a top face of said core of said tapered waveguide includes an inclined plane forming an angle between 0 degrees and 90 degrees with a bottom face, and a direction of a normal to said inclined plane projected on said bottom face matches the direction of wave guiding of said tapered waveguide.

9. The optical converter according to claim 1, wherein an angle between said inclined plane and said bottom face of said core of said tapered waveguide is less than or equal to 30 degrees.

10. The optical converter according to claim 1, wherein

said top face of said core of said tapered waveguide includes a concave face and a convex face;

a tangential plane at an arbitrary position of said concave face and said convex face forms an angle less than or equal to 30 degrees with said bottom face of said core of said tapered waveguide; and

a direction of a normal to said tangential plane projected on said bottom face matches the direction of wave guiding.

11. The optical converter according to claim 1, wherein

a refractive index of a core is greater than or equal to 3, and

a refractive index of cladding is less than or equal to 2.

13. An optical integrated circuit comprising said optical converter according to claim 1, on a single Silicon on Insulator SOI substrate.

12. An optical converter comprising a tapered waveguide arranged between a first waveguide and a second waveguide, wherein

both ends in a direction of wave guiding of a core of said tapered waveguide are connected to a core of said first waveguide and a core of said second waveguide respectively;

at each connection part, cross-sectional shapes and refractive indices of cores of two waveguides that are connected change continuously or in a stepwise manner; and

a cross-sectional shape and refractive index of said core of said tapered waveguide change continuously or in a stepwise manner along a direction of wave guiding.

18. An optical integrated circuit comprising said optical converter according to claim 12, on a single Silicon on Insulator SOI substrate.

14. A method of manufacturing an optical converter comprising:

fabricating core material including a stepped structure in which a thick film and a thin film are connected via a taper in a direction of thickness, to form a tapered waveguide; and

a process of forming a waveguide core of in a wire shape so as to intersect a normal to a tangential plane of a top face of a core of said tapered waveguide, in a direction of a projection of said normal projected on a bottom face of said core of said tapered waveguide.

15. The method of manufacturing an optical converter according to claim 14, comprising, in a range in which a tapered portion intersects the stepped structure, a process of fabricating such that a width of said core of said tapered waveguide decreases monotonically along a direction from a lower side of the stepped structure to a higher side of the stepped structure, or a process of fabricating to have a combination of a portion in which said width decreases monotonically and a portion in which said width is constant.

16. The method of manufacturing an optical converter according to claim 14, comprising,

a process of fabricating, in a range in which said tapered portion intersects the stepped structure, such that the width of said core of said tapered waveguide is constant;

and

a process of fabricating such that the width of said core of said tapered waveguide, in a portion in which thickness of said stepped structure is large, decreases monotonically.

17. A method of manufacturing an optical integrated circuit for a single SOI substrate, comprising a method of manufacturing said optical converter according to claim 14.