Photonic crystal waveguide

• US 6,643,439 B2
• Filed: 12/26/2001
• Issued: 11/04/2003
• Est. Priority Date: 12/27/2000
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Yamada, Koji, Takahashi, Junichi, Takahashi, Chiharu, Notomi, Masaya, Shinya, Akihiko, Yokohama, Itaru
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): VALENCIA, DANIEL E
• Application Number:
  US10/033,766
• Publication Number:
  US 20020118941A1
• Time in Patent Office: 678 Days
• Field of Search: 385/125, 385/129
• US Class Current: 385/125
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02B 6/13 Integrated optical circuits characterised by the manufacturing method

Abstract

A two-dimensional photonic crystal slab waveguide is provided in which a line defect is formed, wherein a first width which is a distance between centers of nearest two lattice points located on both sides of the line defect is different from a second width which is a corresponding distance in a normal two-dimensional photonic crystal slab waveguide. In addition, a two-dimensional photonic crystal slab waveguide is provided in which low refractive index columns in a optical waveguide part are placed at positions shifted from normal positions in a normal two-dimensional photonic crystal slab.

Claims

1. A two-dimensional photonic crystal slab waveguide in which a part of holes in a lattice structure of a two-dimensional photonic crystal slab do not exist linearly so that a line defect is formed, wherein:

a first width which is a distance between centers of nearest two lattice points located on both sides of said line defect is different from a second width which is a distance between centers of nearest two lattice points located on both sides of a line defect in a normal two-dimensional photonic crystal slab waveguide which simply lacks holes of a single line, wherein said first width is a value from 0.5 times to 0.85 times of said second width.

2. The two-dimensional photonic crystal slab waveguide as claimed in claim 1, said lattice structure is formed by air-hole triangle lattices.

3. The two-dimensional photonic crystal slab waveguide as claimed in claim 1, said two-dimensional photonic crystal slab waveguide includes an oxide cladding or a polymer cladding.

4. The two-dimensional photonic crystal slab waveguide as claimed in claim 3, wherein said two-dimensional photonic crystal slab waveguide is formed by using a Silicon-On-Insulator (SOI) substrate.

5. A two-dimensional photonic crystal slab waveguide in which a part of holes in a lattice structure of a two-dimensional photonic crystal slab do not exist linearly so that a line defect is formed, wherein:

a first width which is a distance between centers of nearest-two lattice points located on both sides of said line defect is different from a second width which is a distance between centers of nearest two lattice points located on both sides of a line defect in a normal two-dimensional photonic crystal slab waveguide which simply lacks holes of a single line;

wherein said first width is wider than said second width in which a single-mode appears in a high frequency side of a light line of cladding in a dispersion relation of waveguiding modes of said two-dimensional photonic crystal slab waveguide having said first width, and said first width is a value from 1.3 times to 1.6 times of said second width.

6. The two-dimensional photonic crystal slab waveguide as claimed in claim 5, said lattice structure is formed by air-hole triangle lattices.

7. The two-dimensional photonic crystal slab waveguide as claimed in claim 5, said two-dimensional photonic crystal slab waveguide includes an oxide cladding or a polymer cladding.

8. The two-dimensional photonic crystal slab waveguide as claimed in claim 7, wherein said two-dimensional photonic crystal slab waveguide is formed by using a Silicon-On-Insulator (SOI) substrate.

9. A two-dimensional photonic crystal slab waveguide in which dielectric cylindrical or polygon columns having lower refractive index than that of a dielectric thin-film slab are provided in said dielectric thin-film slab in a two-dimensional lattice pattern, and said dielectric thin-film slab is sandwiched by a top cladding layer and a bottom cladding layer which have lower refractive index than that of said dielectric thin-film slab, wherein:

dielectric columns in an optical waveguide part in said two-dimensional photonic crystal slab waveguide are located at positions which are shifted in an optical propagation direction from positions at which said dielectric columns should be positioned in a normal two-dimensional photonic crystal slab.

10. The two-dimensional photonic crystal slab waveguide as claimed in claim 9, wherein:

a first diameter of said dielectric columns in said optical waveguide part is different from a second diameter of other dielectric columns located in parts other than said optical waveguide part, and said first diameter is a value by which said dielectric columns does not contact with said other dielectric columns.

11. The two-dimensional photonic crystal slab waveguide as claimed in claim 9, wherein each dielectric column of dielectric columns in said optical waveguide part is apart from a position at which said each dielectric column should be positioned in said normal two-dimensional photonic crystal slab by a half of the lattice constant of said normal two-dimensional photonic crystal slab.

12. The two-dimensional photonic crystal slab waveguide as claimed in claim 9, wherein said dielectric cylindrical or polygon columns are arranged in a triangle lattice pattern having a lattice constant “

a”

, a radius or a half-breadth of said dielectric cylindrical or polygon columns is from 0.2a to 0.45a, and said radius or half-breadth is determined such that said dielectric cylindrical or polygon columns do not contact with dielectric columns in said optical waveguide part.

13. The two-dimensional photonic crystal slab waveguide as claimed in claim 12, wherein:

a refractive index of said dielectric thin-film slab is from 3.0 to 4.5, and each of refractive indices of parts other than said dielectric thin-film slab is from 1.0 to 1.7.

14. The two-dimensional photonic crystal slab waveguide as claimed in claim 9, wherein said dielectric cylindrical or polygon columns are arranged in a square lattice pattern having a lattice constant “

a”

, a radius or a half-breadth of said dielectric cylindrical or polygon columns is from 0.35a to 0.45a, and said radius or half-breadth is determined such that wherein said dielectric cylindrical or polygon columns do not contact with dielectric columns in said optical waveguide part.

15. The two-dimensional photonic crystal slab waveguide as claimed in claim 14, wherein:

a refractive index of said dielectric thin-film slab is from 3.0 to 4.5, and each of refractive indices of parts other than said dielectric thin-film slab is from 1.0 to 1.7.

16. The two-dimensional photonic crystal slab waveguide as claimed in claim 9, wherein:

silicon, germanium, gallium arsenide base compound, indium phosphide base compound, or indium antimony base compound is used as a material of said dielectric thin-film slab, and silica, polyimide base organic compound, epoxy base organic compound, acrylic base organic compound, air or vacuum is used as a material of parts other than said dielectric thin-film slab.

17. The two-dimensional photonic crystal slab waveguide as claimed in claim 16, wherein said two-dimensional photonic crystal slab waveguide is formed by using a Silicon-On-Insulator (SOI) substrate.