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Two-dimensional photonic crystal slab, two-dimensional photonic crystal waveguide, and optical device

外国特許コード F140007931
整理番号 253
掲載日 2014年8月19日
出願国 アメリカ合衆国
出願番号 92702904
公報番号 20050047742
公報番号 7336879
出願日 平成16年8月26日(2004.8.26)
公報発行日 平成17年3月3日(2005.3.3)
公報発行日 平成20年2月26日(2008.2.26)
優先権データ
  • 特願2003-305329 (2003.8.28) JP
  • 特願2004-058981 (2004.3.3) JP
発明の名称 (英語) Two-dimensional photonic crystal slab, two-dimensional photonic crystal waveguide, and optical device
発明の概要(英語) A two-dimensional photonic crystal slab having a photonic band gap common to a light beam in the TE-like mode and a light beam in the TM-like mode includes a slab member containing a high refractive index material and low refractive index sectors, arranged in the slab member in a triangular pattern, having a triangular prism shape.
The two-dimensional photonic crystal slab further includes a linear defect section that is a disordered portion in a periodic structure of a photonic crystal and extends in the Gamma-J direction.
Light beams in the TE-like mode and light beams in the TM-like mode can be propagated through the waveguide section.
A two-dimensional photonic crystal waveguide includes the two-dimensional photonic crystal slab.
従来技術、競合技術の概要(英語) BACKGROUND OF THE INVENTION
1.
Field of the Invention
The present invention relates to a two-dimensional photonic crystal slab included in a micro-optical circuit element or the like, a two-dimensional photonic crystal waveguide including such a two-dimensional photonic crystal slab having a linear defect, and an optical device including such a two-dimensional photonic crystal waveguide.
2. Description of the Related Art
Materials with a periodic variation in refractive index on a length scale comparable to the wavelength of light are referred to as photonic crystals, which have forbidden bands that is, so-called photonic band gaps.
In such materials, the propagation of light with a specific wavelength corresponding to the periodicity is prohibited.
In recent years, the photonic crystals have been attracting much attention because light propagation can be precisely controlled using the photonic crystals, which therefore seem to be suitable for next-generation electronics or optoelectronics.
FIG. 44 shows an example of known two-dimensional photonic crystal waveguides (see Japanese Unexamined Patent Application Publication No. 2001-272555).
This two-dimensional photonic crystal waveguide includes a slab 81, made of a material having a refractive index higher than that of air, having cylindrical holes 86 arranged in a triangular grid pattern.
The slab 81 therefore functions as a two-dimensional photonic crystal.
The slab 81 has a linear defect section 92 extending between the cylindrical holes 86 as shown in FIG. 44. The linear defect section 92 functions as a waveguide section.
When the two-dimensional photonic crystal waveguide is irradiated with a light beam 103 with a wavelength corresponding to a frequency within a photonic band gap, the light beam 103 is prevented from being propagated in regions of the waveguide other than the linear defect section 92 because the regions have photonic band gaps in the in-plane direction; however, the light beam 103 is propagated in the linear detect section 92 functioning as a waveguide section and confined in the direction perpendicular to the in-plane direction by the total internal reflection due to a difference in refractive index.
Known two-dimensional photonic crystal waveguides have a photonic band gap for only one of a light beam in the transverse-electric (TE)-like mode and a light beam in the transverse-magnetic (TM)-like mode, the TE-like mode and the TM-like mode being among polarization modes.
Therefore, a light beam in one of the modes is prevented from being propagated but a light beam in the other leaks in the in-plane direction of the waveguides; hence, the waveguides have low light extraction efficiency.
For example, a two-dimensional photonic crystal waveguide having cylindrical holes arranged in a triangular grid pattern has a photonic band gap only for the light beam in the TE-like mode; hence, the light beam in the TM-like mode leaks in the in-plane direction of the waveguide.
A two-dimensional photonic crystal slab having a photonic band gap common to the light beam in the TE-like mode and the light beam in the TM-like mode has been demanded; however, such a two-dimensional photonic crystal slab has not been obtained.

特許請求の範囲(英語) [claim1]
1. A two-dimensional photonic crystal slab having a photonic band gap for light propagated through the slab, comprising: a slab member containing a material having a high refractive index;
and
sectors that are periodically arranged in the slab member, contain a material having a refractive index less than that to the slab member, and define the distribution of refractive index in the slab,wherein the low refractive index sectors have a shape with C3v symmetry and are arranged in the slab member in a triangular grid pattern, andwherein the low refractive index sectors have a regular triangular prism shape and satisfy the inequality 0.7<L/a <= 1.0, where L represents the length of edges of triangular faces of the low refractive index sectors and a represents the minimum distance between the centers of the low refractive index sectors or the grating constant.
[claim2]
2. The two-dimensional photonic crystal slab according to claim 1, wherein the slab member satisfies the inequality 0.1 <= t/lambda 0 <= 0.3, where t represents the thickness of the slab member and lambda 0 represents the center wavelength of a photonic band gap.
[claim3]
3. A two-dimensional photonic crystal slab having a photonic band gap common to a light beam in the TE-like mode and a light beam in the TM-like mode, comprising: a slab member containing a material having a high refractive index;
and
sectors that are periodically arranged in the slab member, contain a material having a refractive index less than that of the slab member, and define the distribution of refractive index in the slab,wherein the low refractive index sectors are arranged in the slab member in a square grid pattern, and the slab member satisfies the inequality 0.1 <= t/lambda 0 <= 0.3, where t represents the thickness of the slab member and lambda 0 represents the center wavelength of a photonic band gap, andwherein the low refractive index sectors have a cylindrical shape and satisfy the inequality 0.4 <= r/a<0.50, where r represents the radius of the low refractive index sectors and a represents the minimum distance between the centers of the low refractive index sectors or the grating constant.
[claim4]
4. The two-dimensional photonic crystal slab according to claim 1, wherein the slab member has a support layer, placed on at least one face thereof, having no low refractive index sectors.
[claim5]
5. The two-dimensional photonic crystal slab according to claim 3, wherein the slab member has a support layer, placed on at least one face thereof, having no low refractive index sectors.
[claim6]
6. A two-dimensional photonic crystal waveguide comprising: the two-dimensional photonic crystal slab according to claim 1, wherein the two-dimensional photonic crystal slab includes a linear defect section that is a disordered portion in a periodic structure of a photonic crystal, extends in the GAMMA -J direction, and functions as a waveguide section for guiding light in the TB-like mode and light in the TM-like mode.
[claim7]
7. A two-dimensional photonic crystal waveguide comprising the two-dimensional photonic crystal slab according to claim 3, wherein the two-dimensional photonic crystal slab includes a linear defect section that is a disordered portion in a periodic structure of a photonic crystal, extends in the GAMMA -X direction, and functions as a waveguide section for guiding light in the TE-like mode and light in the TM-like mode.
[claim8]
8. The two-dimensional photonic crystal waveguide according to claim 6, wherein the low refractive index sectors are grouped into a first and a second region, which are asymmetric about the waveguide section.
[claim9]
9. The two-dimensional photonic crystal waveguide according to claim 6, wherein the low refractive index sectors are grouped into a first and a second region, which are symmetric about the waveguide section.
[claim10]
10. The two-dimensional photonic crystal waveguide according to claim 6, wherein at least one of the dispersion relation and frequency range of light is controlled by varying the waveguide section width.
[claim11]
11. The two-dimensional photonic crystal waveguide according to claim 6, wherein the waveguide section is allowed to function as an acceptor-type waveguide by varying the width of the waveguide section.
[claim12]
12. The two-dimensional photonic crystal waveguide according to claim 6, wherein the two-dimensional photonic crystal slab satisfies the inequality (2Root 3)a * (2/16) <= W <= (2Root 3)a * (18/16), where W represents the width of the waveguide sections and a represents the minimum distance between the centers of the low refractive index sectors or the grating constant.
[claim13]
13. The two-dimensional photonic crystal waveguide according to claim 7, wherein at least one of the dispersion relation and frequency range of light is controlled by varying the waveguide section width.
[claim14]
14. The two-dimensional photonic crystal waveguide according to claim 7, wherein the waveguide section is allowed to function as an acceptor-type wave guide by varying the width of the waveguide section.
[claim15]
15. An optical device comprising the two-dimensional photonic crystal waveguide according to claim 6.
[claim16]
16. An optical device comprising the two-dimensional photonic crystal waveguide according to claim 7.
[claim17]
17. Two-dimensional photonic crystal waveguide comprising: a two-dimensional photonic crystal slab having a photonic band gap for light propagated through the slab, includinga slab member containing a material having a high refractive index;
and
sectors that are periodically arranged in the slab member, contain a material having a refractive index less than that of the slab member, and define the distribution of refractive index in the slab,wherein the two-dimensional photonic crystal slab includes a linear defect section that is a disordered portion in a periodic structure of a photonic crystal extends in the GAMMA -J direction, and functions as a waveguide section for guiding light in the TE-like mode and light in the TM-like mode,wherein the low refractive index sectors have a shape with C3v symmetry and are arranged in the slab member in a triangular grid pattern, andwherein the low refractive index sectors are grouped into a first and a second region, which are asymmetric about the waveguide section.
[claim18]
18. The two-dimensional photonic crystal waveguide according to claim 17, wherein the slab member satisfies the inequality 0.1 <= t/lambda 0 <= 0.3, where t represents the thickness of the slab member and lambda 0 represents the center wavelength of a photonic band gap.
[claim19]
19. The two-dimensional photonic crystal waveguide according to claim 17, wherein the low refractive index sectors have a shape selected from the group consisting of a regular triangular prism shape;
a hexagonal prism shape, other than a regular hexagonal prism shape, formed by chamfering edges of a regular biangular prism;
a shape in which a regular triangular prism has edges each having corresponding protrusions;
and a shape in which a triplet of cylindrical prisms are arranged such that straight lines connecting the centers of the cylindrical prisms form a regular triangle when viewed from above.
[claim20]
20. The two-dimensional photonic crystal waveguide according to claim 17, wherein the slab member has a support layer, placed on at least one face thereto having no low refractive index sectors.
[claim21]
21. A two-dimensional photonic crystal slab having a photonic band gap for light propagated through the slab, comprising: a slab member containing a material having a high refractive index;
and
sectors that are periodically arranged in the slab member, contain a material having a refractive index less than that of the slab member, and define the distribution of refractive index in the slab,wherein the low refractive index sectors have a shape with C3v symmetry and are arranged in the slab member in a triangular grid pattern,wherein the low refractive index sectors have a triangular shape in horizontal cross section in which vertices are concave.
[claim22]
22. The two-dimensional photonic crystal slab according to claim 21, wherein the slab member satisfies the inequality 0.1 <= t/lambda 0 <= 0.3 where t represents the thickness of the slab member and lambda 0 represents the center wavelength of a photonic band gap.
[claim23]
23. A two-dimensional photonic crystal slab having a photonic band gap for light propagated through the slab, comprising: a slab member containing a material having a high refractive index;
and
sectors that are periodically arranged in the slab member, contain a material having a refractive index less than that of the slab member, and define the distribution of refractive index in the slab,wherein the low refractive index sectors have a shape with C3v symmetry and are arranged in the slab member in a triangular grid pattern,wherein the low refractive index sectors have a triangular prism shape in which each vertex angle portion has a corresponding flat surface, and have a Y-shape in horizontal cross section.
[claim24]
24. The two-dimensional photonic crystal slab according to claim 23, wherein the slab member satisfies the inequality 0.1 <= t/lambda 0 <= 0.3, where t represents the thickness of the slab member and lambda 0 represents the center wavelength of a photonic band gap.
[claim25]
25. A two-dimensional photonic crystal slab having a photonic band gap for light propagated through the slab, comprising: a slab member containing a material having a high refractive index;
and
sectors that are periodically arranged in the slab member, contain a material having a refractive index less than that of the slab member, and define the distribution of refractive index in the slab,wherein the low refractive index sectors have a shape with C3v symmetry and are arranged in the slab member in a triangular grid pattern,wherein the low refractive index sectors have a unit of three cylindrical columns in which centers of the three cylindrical columns in the unit constitute an equilateral triangle.
[claim26]
26. The two-dimensional photonic crystal slab according to claim 25, wherein the slab member satisfies the inequality 0.1 <= t/lambda 0 <= 0.3, where t represents to thickness of to slab member and lambda 0 represents the center wavelength of a photonic band gap.
  • 発明者/出願人(英語)
  • KITAGAWA HITOSHI
  • NODA SUSUMU
  • ASANO TAKASHI
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 385/129
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