Two-dimensional photonic crystal

• US 20070172188A1
• Filed: 03/04/2005
• Published: 07/26/2007
• Est. Priority Date: 03/05/2004
• Status: Active Grant

• Current Assignee: Kyoto University
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.), Kyoto University, TDK Corporation
• Inventors: Asano, Takashi, Noda, Susumu, Kitagawa, Hitoshi, Takawayam, Seiichi
• Granted Patent: US 7,853,111 B2
• Time in Patent Office: Days
• US Class Current: 385/130
• 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 6/29325 of the slab or planar or plate like form, i.e. confinement in a single transverse dimension only integrated circuit planar waveguide arrangements G02B6/12007; specially adapted for lighting G02B6/0011
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM

Abstract

The present invention provides a two-dimensional photonic crystal in which an absolute photonic band gap (PBG), i.e. a photonic band gap that is effective for both the TE-polarized light and the TM-polarized light within a predetermined wavelength range, is created with an adequate bandwidth. The body 21 is provided with holes 22 arranged in a triangular lattice pattern, where the basic shape of the hole is an equilateral triangle. This shaping and arranging of the holes creates an absolute PBG. Each corner of the equilateral triangle is cut along an arc to leave an adequate distance between the neighboring holes (i.e. an adequate width of the connecting portion of the body). This design makes it possible to enlarge each hole 22 while ensuring an adequate strength of the two-dimensional photonic crystal. This construction creates an absolute PBG having a large width.

Claims

1. A two-dimensional photonic crystal having a slab-shaped body in which modified refractive index areas, which have the same shape and whose refractive index differs from that of the body, are cyclically arranged, which is characterized in that:

a plane shape of each modified refractive index area is a polygon whose corners are removed.

2. The two-dimensional photonic crystal according to claim 1, which is characterized in that the modified refractive index area has a 3m-symmetrical shape.

3. The two-dimensional photonic crystal according to claim 2, which is characterized in that the polygon is an equilateral triangle.

4. The two-dimensional photonic crystal according to claim 1, which is characterized in that the corners are removed along an arc.

5. The two-dimensional photonic crystal according to claim 4, which is characterized in that:

the modified refractive index areas are arranged in a triangular lattice pattern;

the polygon is an equilateral triangle;

the refractive index of the body is within a range from 3.15 to 3.55; and

a radius r_a of the arc satisfies a following equation;

0<

r_a<

[1.23(FF−

0.34)^0.5−

1.28(FF−

0.34)+1.03(FF−

0.34)²],

where FF is an area fraction of the modified refractive index areas in the body.

6. The two-dimensional photonic crystal according to claim 1, which is characterized in that an area fraction FF of the modified refractive index areas in the body is within a range from 0.45 to 0.85.

7. The two-dimensional photonic crystal according to claim 6, which is characterized in that the FF value is within a range from 0.5 to 0.70.

8. The two-dimensional photonic crystal according to claim 1, which is characterized in that each modified refractive index area consists of holes.

9. An optical waveguide device, which is characterized in that it comprises:

a two-dimensional photonic crystal according to claim 1, in which a linear defect of the modified refractive index areas is created.

10. An optical resonator device, which is characterized in that it comprises:

a two-dimensional photonic crystal according to claim 1, in which a point-like defect of the modified refractive index areas is created.

11. An optical multiplexer/demultiplexer, which is characterized in that it comprises:

a two-dimensional photonic crystal according to claim 1;

at least one optical waveguide including a linear defect of the modified refractive index areas created in the two-dimensional photonic crystal; and

at least one optical resonator including a point-like defect of the modified refractive index areas created in a vicinity of the optical waveguide.