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Photonic crystal laser

外国特許コード F110003518
整理番号 AF08-01US
掲載日 2011年6月28日
出願国 アメリカ合衆国
出願番号 23049408
公報番号 20090074024
公報番号 8284814
出願日 平成20年8月29日(2008.8.29)
公報発行日 平成21年3月19日(2009.3.19)
公報発行日 平成24年10月9日(2012.10.9)
優先権データ
  • 特願2007-226255 (2007.8.31) JP
発明の名称 (英語) Photonic crystal laser
発明の概要(英語) A laser capable of emitting multiple laser beams is provided.
A two-dimensional photonic crystal laser according to the present invention has a laminated structure including an active layer, a first photonic crystal layer having a periodic distribution of refractive index with a first period, and a second photonic crystal layer having a periodic distribution of refractive index with a second period that differs from the first period.
This two-dimensional photonic crystal laser can emit a main beam traveling in a direction perpendicular to the two-dimensional photonic crystals and side beams each traveling in a direction inclined with respect to the main beam.
These beams can be used, for example, in a recording/reproducing device by means of an optical disk, the main beam being used for recording/reproducing information and the side beams for following up the track.
従来技術、競合技術の概要(英語) BACKGROUND ART
In a device for recording information onto an optical disk or reproducing information from an optical disk, when a single recording/reproducing laser beam is delivered onto a track in which information is to be recorded or has been recorded, two position-detecting laser beams that are symmetrical with respect to the recording/reproducing laser beam are also delivered onto the same track.
These beams are generated by splitting a single laser beam from one light source (i.e. a laser) with a diffraction grating (for example, refer to Patent Document 1 and Non-Patent Document 1).
A single laser light source generally emits a single laser beam in a specific direction.
Therefore, if multiple laser beams are required, it is necessary to use a diffraction grating or similar dispersing element to split one laser beam emitted from the light source, or provide two or more light sources.
Accordingly, if multiple laser beams can be generated from a single element, the diffraction grating will no longer be necessary, so that the device will be downsized and its production cost will be decreased.
On the other hand, it is known that a laser using a two-dimensional photonic crystal normally emits a single laser beam in a direction perpendicular to the two-dimensional photonic crystal (for example, refer to Patent Document 2) yet allows the emitting direction of the laser beam to be controlled by appropriately shaping the holes created in the two-dimensional photonic crystal (refer to Non-Patent Document 2).
This is because an appropriately shaped hole improves the light-confining property (which is represented by a Q// value) with respect to the direction parallel to the two-dimensional photonic crystal in a photonic band in which the group velocity becomes zero when the component k// of the wave number vector parallel to the two-dimensional photonic crystal is at a non-GAMMA point, i.e. when k// is not zero.
However, Non-Patent Document 2 makes no mention as to the number of laser beams emitted from the laser and thereby offers little help in the development of a device that requires multiple laser beams (e.g. the aforementioned optical disk recording/reproducing device).
Patent Document 1: U.S. Pat. No. 3,876,842
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-332351
Non-Patent Document 1: Ryoichi Ito and Michiharu Nakamura, Handoutai Rehza [Kiso To Ouyou] (Semiconductor Laser [Basics and Applications]), pp. 305-306, published Apr. 25, 1989, Baifukan Co., Ltd, Tokyo
Non-Patent Document 2: Eiji Miyai et al., "Fotonikku Kesshou Men Hakkou Rehza No Gamma-Ten Igai Deno Hasshin No Kanousei No Kentou (Study on the Possibility of the Oscillation of a Photonic Crystal Surface Emitting Laser at a Point other than the GAMMA Point)", Preprints of 67th Meeting of Japan Society of Applied Physics (Issued Aug. 29, 2006), Part 3, p. 968, Japan Society of Applied Physics

特許請求の範囲(英語) [claim1]
1. A photonic crystal laser comprising: an active layer for generating light of a predetermined wave number range upon an injection of an electric current;
a first photonic crystal layer for forming a standing wave of light within the first photonic crystal layer having a first wave number within the predetermined wave number range, among the light generated in the active layer; and
a second photonic crystal layer for forming a standing wave of light within the second photonic crystal layer having a second wave number within the predetermined wave number range and different from the first wave number, among the light generated in the active layer, wherein the first photonic crystal layer is provided on one side of the active layer, and the second photonic crystal layer is provided on the other side of the active layer, and
a spatial beat results from a superposition of the standing wave of light formed by the first photonic crystal layer and the standing wave of light formed by the second photonic crystal layer.
[claim2]
2. The photonic crystal laser according to claim 1, wherein the first photonic crystal layer has a periodic distribution of refractive index with a first period, while the second photonic crystal layer has a periodic distribution of refractive index with a second period that differs from the first period.
[claim3]
3. The photonic crystal laser according to claim 2, wherein each of the first and second photonic crystal layers is a two-dimensional photonic crystal including a plate member in which modified refractive index portions whose refractive index differs from that of the plate member are periodically arranged.
[claim4]
4. The photonic crystal laser according to claim 3, wherein: the modified refractive index portions in the first photonic crystal layer are arranged on lattice points of an orthogonal lattice or triangular lattice; and
the modified refractive index portions in the second photonic crystal layer are arranged on a same type of lattice as the modified refractive index portions in the first photonic crystal layer.
[claim5]
5. The photonic crystal laser according to claim 4, wherein the first and second photonic crystal layers are configured so that one of these two layers has its modified refractive index portions arranged in a square lattice pattern while the other layer has its modified refractive index portions arranged in a rectangular lattice pattern, the period of this rectangular lattice in a first direction being equal to the period of the square lattice, and the period of the same rectangular lattice in a second direction perpendicular to the first direction being different from the period of the square lattice.
[claim6]
6. The photonic crystal laser according to claim 2, wherein: the first photonic crystal layer is a first plate member defined by an X-Y plane and having a first rod group formed by rods having a refractive index different from that of the first plate member, the rods being embedded in the first plate member in a pattern parallel to each other in a first direction and parallel to the X-Y plane;
the second photonic crystal layer is a second plate member defined by the X-Y plane and having a second rod group formed by rods having a refractive index different from that of the second plate member, the rods being embedded in the second plate member in a pattern parallel to each other in a second direction and parallel to the X-Y plane, and perpendicular to the rods of the first rod group; and
at least either the first or second rod group has a defect created in a periodic structure thereof.
[claim7]
7. The photonic crystal laser according to claim 2 wherein: a current injection means for injecting the electric current into only a portion of the active layer is provided, an injection point thereof being controllable; and
the second period of the second photonic crystal layer changes according to a position within the same layer.
[claim8]
8. The photonic crystal laser according to claim 7, wherein: the second photonic crystal layer has a plurality of modified period areas having different second periods; and
the current injection means includes a pair of electrodes between which the active layer, the first photonic crystal layer and the second photonic crystal layer are sandwiched, one of the two electrodes being divided into a plurality of electrode segments for each of the modified period areas.
[claim9]
9. The photonic crystal laser according to claim 8, wherein the modified period areas are arranged in a rectangular lattice pattern with lattice points arrayed in two directions intersecting each other in the rectangular lattice, in which a lattice-point interval in one direction varies from one modified period area to another.
[claim10]
10. The photonic crystal laser according to claim 8, wherein the modified period areas are arranged in a rectangular lattice pattern with lattice points arrayed in two directions intersecting each other in the rectangular lattice, in which lattice-point intervals in both directions vary from one modified period area to another.
[claim11]
11. The photonic crystal laser according to claim 7, wherein the second period continuously varies within the second photonic crystal layer.
[claim12]
12. The photonic crystal laser according to claim 11, wherein the current injection means includes a pair of electrodes between which the active layer, the first photonic crystal layer and the second photonic crystal layer are sandwiched, one of the two electrodes being divided into a plurality of electrode segments.
[claim13]
13. The photonic crystal laser according to claim 11, wherein the modified period areas are arranged in a rectangular lattice pattern with lattice points arrayed in two directions intersecting each other in the rectangular lattice, in which a lattice-point interval in one direction varies from one modified period area to another.
[claim14]
14. The photonic crystal laser according to claim 11, wherein the modified period areas are arranged in a rectangular lattice pattern with lattice points arrayed in two directions intersecting each other in the rectangular lattice, in which lattice-point intervals in both directions vary from one modified period area to another.
  • 発明者/出願人(英語)
  • NODA SUSUMU
  • KUROSAKA YOSHITAKA
  • SAKAI KYOSUKE
  • MIYAI EIJI
  • OHNISHI DAI
  • KUNISHI WATARU
  • ROHM
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 372/96
参考情報 (研究プロジェクト等) CREST Photonics and Quantum Optics for the Creation of Innovative Functions AREA
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