WO2009098999A1 - Optical module, electronic device and spatial communication system - Google Patents

Optical module, electronic device and spatial communication system Download PDF

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Publication number
WO2009098999A1
WO2009098999A1 PCT/JP2009/051494 JP2009051494W WO2009098999A1 WO 2009098999 A1 WO2009098999 A1 WO 2009098999A1 JP 2009051494 W JP2009051494 W JP 2009051494W WO 2009098999 A1 WO2009098999 A1 WO 2009098999A1
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quantum dot
dot laser
laser
optical module
light
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PCT/JP2009/051494
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French (fr)
Japanese (ja)
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Mitsuru Sugawara
Makoto Usami
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Qd Laser Inc.
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Publication of WO2009098999A1 publication Critical patent/WO2009098999A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/341—Structures having reduced dimensionality, e.g. quantum wires
    • H01S5/3412—Structures having reduced dimensionality, e.g. quantum wires quantum box or quantum dash

Definitions

  • the present invention relates to an optical module, an electronic device, and a spatial communication system, and more particularly to an optical module, an electronic device, and a spatial communication system having a quantum dot laser.
  • Optical modules that emit laser light are used in communication systems such as optical communication systems using optical fibers such as FTTH (fiber-to-the-home) and spatial communication systems using light.
  • communication systems such as optical communication systems using optical fibers such as FTTH (fiber-to-the-home) and spatial communication systems using light.
  • FTTH fiber-to-the-home
  • Patent Document 1 JP 2001-85665 A Electronics Letters 2007 Vol.43 pp670-672
  • FIG. 1 is a schematic diagram showing the optical output with respect to the driving current of a Fabry-Perot semiconductor laser using an InP-based semiconductor used at these wavelengths for each temperature.
  • the broken line is the current-light output characteristic immediately after manufacture, and the solid line is the current-light output characteristic after being used for a long time (that is, energized for a long time) and deteriorated.
  • the current-light output characteristics of the semiconductor laser are not constant depending on the temperature and energization time of the semiconductor laser.
  • the current-light output characteristics of the semiconductor laser are not constant.
  • FIG. 2 is a block diagram of a conventional optical module.
  • the optical module 100 includes a semiconductor laser 60a, a drive circuit 62a, a light detection unit 64, an APC circuit 66, and an input unit 68.
  • the input unit 68 receives a transmission data signal 78 from the outside, and outputs a transmission data signal to the drive circuit 62.
  • the drive circuit 62a controls the magnitude of the drive current 72 based on the control signal 76, and outputs the drive current 72 to the semiconductor laser 60a.
  • the drive circuit 62a modulates the drive current 72 with the transmission data signal.
  • the semiconductor laser 60 a emits a laser beam with an optical output corresponding to the drive current 72. Since the drive current 72 is modulated, the laser beam 70 is modulated.
  • the light detection unit 64 made of a photodiode detects a part of the light emitted from the semiconductor laser 60a and outputs a monitor current 74 corresponding to the light output of the semiconductor laser 60a to the APC circuit 66.
  • the APC circuit 66 compares the monitor current 74 with the reference current and outputs a control signal 76 to the drive circuit 62a.
  • the APC circuit 66 is used to keep the optical output constant.
  • the conventional optical module has a problem that it is difficult to reduce the cost because the APC circuit 66a is used.
  • the present invention has been made in view of the above problems, and an object thereof is to provide an optical module, an electronic device, and a spatial communication system that are low in cost and excellent in light stability.
  • the present invention includes a quantum dot laser having a quantum dot formed on a base layer, a cover layer covering the quantum dot, and a drive circuit for supplying a constant drive current to the quantum dot laser.
  • This is an optical module.
  • the quantum dot laser since the quantum dot laser is used, the light output can be made constant without using the APC circuit. Therefore, it is possible to provide an optical module that is low in cost and excellent in light stability.
  • the driving circuit may be configured not to feed back the light output of the quantum dot laser. According to this configuration, an inexpensive optical module can be provided.
  • the base layer may be made of GaAs
  • the cover layer may be made of InGaAs
  • the quantum dots may be made of InAs.
  • the quantum dot laser can emit light for spatial communication.
  • Light used for spatial communication is required to maintain a constant light output from the viewpoint of safety.
  • safety can be ensured.
  • the output wavelength of the quantum dot laser may be 1.2 ⁇ m to 1.6 ⁇ m. In this configuration, damage to the eyes can be suppressed.
  • the present invention includes a quantum dot laser having a quantum dot formed on a base layer and a cover layer covering the quantum dot, and emitting light having a wavelength of 1.2 ⁇ m to 1.6 ⁇ m in a space, and constant driving
  • a spatial communication transmitter having a drive circuit for supplying current to the quantum dot laser, and a spatial communication receiver having a light receiving element that receives light having a wavelength of 1.2 ⁇ m to 1.6 ⁇ m from the space.
  • An electronic device is provided. According to the present invention, since light having a wavelength of 1.2 ⁇ m to 1.6 ⁇ m is used as the light emitted to the space, damage to the eyes can be suppressed. Further, since the quantum dot laser is used, the output can be maintained at a constant value, and further safety can be ensured. In addition, since it is not necessary to use an APC circuit, manufacturing cost can be reduced.
  • the present invention includes a quantum dot laser having a quantum dot formed on a base layer and a cover layer covering the quantum dot and emitting light having a wavelength of 1.2 ⁇ m to 1.6 ⁇ m in a space;
  • a first device having a drive circuit for supplying a drive current to the quantum dot laser, and a second device having a light receiving element that receives light emitted from the quantum dot laser of the transmission device from space.
  • the present invention includes a first quantum dot laser having a quantum dot formed on a base layer and a cover layer covering the quantum dot and emitting light having a wavelength of 1.2 ⁇ m to 1.6 ⁇ m in a space.
  • a spatial communication system comprising: a device; and a second device having a light receiving element that receives light emitted from the space by the quantum dot laser of the transmission device. According to the present invention, it is possible to provide a spatial communication system that is excellent in safety and low in cost.
  • the quantum dot laser since the quantum dot laser is used, the light output can be made constant without using the APC circuit. Therefore, it is possible to provide an optical module, an electronic device, and a spatial communication system that are low in cost and excellent in light stability.
  • FIG. 1 is a schematic diagram showing current-light output characteristics of a conventional semiconductor laser.
  • FIG. 2 is a block diagram showing a conventional optical module.
  • FIG. 3 is a block diagram of the optical module according to the first embodiment.
  • FIG. 4 is a cross-sectional view of the quantum dot laser of Example 1.
  • FIG. 5 is an enlarged cross-sectional view of the vicinity of the quantum dots of the quantum dot laser of Example 1.
  • FIG. 6 is a diagram showing temperature dependence of current-light output characteristics in a quantum dot laser.
  • FIGS. 7A and 7B are diagrams showing the results of investigating the deterioration with respect to the energization time in the quantum dot laser.
  • FIG. 8 is a block diagram of a spatial communication system according to the second embodiment.
  • FIG. 3 is a block diagram of the optical module according to the first embodiment.
  • the optical module 100 according to the first embodiment does not include a light receiving element and an APC circuit.
  • a quantum dot laser is used as the semiconductor laser 60a.
  • FIG. 4 is a schematic sectional view of the quantum dot Fabry-Perot laser 50.
  • five GaAs base layers 12 and five quantum dot active layers are stacked on a p-type AlGaAs cladding layer 10.
  • An n-type AlGaAs cladding layer 14 is formed on the base layer 12.
  • the n-type AlGaAs cladding layer 14 is isolated, and the quantum dot laser 50 has a ridge structure.
  • An n-electrode 16 is formed on the n-type AlGaAs cladding layer 14, and a p-electrode 18 is formed below the p-type AlGaAs cladding layer 10.
  • the n-type AlGaAs cladding layer 14 has a width of 1.8 ⁇ m and a length of 0.25 mm.
  • FIG. 5 is an enlarged view of the quantum dot active layer and the base layer 12.
  • a first InGaAs layer 22 having a thickness of about 2 nm is formed on the GaAs base layer 12 having a thickness of about 50 nm.
  • a plurality of quantum dots 30 made of InAs are formed on the first InGaAs layer 22.
  • a second InGaAs layer 24 having a thickness of 6 nm is formed so as to cover the quantum dots 30.
  • the first InGaAs layer 22 and the second InGaAs layer 24 constitute the cover layer 20, and the respective In composition ratios are 0.15 and 0.2.
  • a GaAs base layer 12 is formed on the second InGaAs layer 24.
  • FIG. 6 is a diagram showing current-light output characteristics at each temperature of the quantum dot laser 50. As shown in FIG. 6, the temperature dependency of the current-light output characteristics of the quantum dot laser 50 is small.
  • the base layer 12 is made of GaAs
  • the cover layer 20 is made of InGaAs
  • the quantum dots 30 are made of InAs. Thereby, the temperature dependence of light output can be suppressed.
  • FIG. 7A is a diagram showing deterioration of optical output due to energization of the quantum dot laser 50.
  • the quantum dot laser 50 is used as the semiconductor laser 60a of the optical module in FIG. On the other hand, it is illustrated.
  • FIG. 7B is a diagram showing a ratio between the change amount (I-I start ) from the drive current I start at the start of energization of the drive current I and I start .
  • the drive current is controlled by the APC circuit 66 so that an optical output of 2 mW can be obtained at an environmental temperature of 90 ° C.
  • the plurality of lines in FIGS. 7A and 7B indicate the drive currents I of the plurality of quantum dot lasers 50, respectively. From FIG. 7A and FIG.
  • the driving current I of the quantum dot laser 50 is substantially constant even when the energization test is performed. In other words, the light output is almost constant even when the driving current I of the quantum dot laser 50 is kept constant. As described above, the quantum dot laser 50 has substantially constant current-light output characteristics with respect to temperature and energization time.
  • the optical module 100 includes a quantum dot laser 50 and a drive circuit 62 that supplies a constant drive current 72 to the quantum dot laser 60 as shown in FIG.
  • the quantum dot laser 50 outputs laser light with a constant light output even when the driving circuit 62 that supplies the constant driving current 72 to the quantum dot laser 50 is used. can do. Therefore, the APC circuit as shown in FIG. 2 is not necessary. That is, the drive circuit 62 does not feed back the light output of the quantum dot laser 60. For this reason, the light output is constant and the cost can be reduced.
  • Example 2 is an example of a spatial communication system using Example 1.
  • FIG. 8 is a block diagram of a spatial communication system according to the second embodiment.
  • the spatial communication system 120 includes a first device 80a and a second device 80b.
  • the first device 80a and the second device 80b have transmission units 82a and 82b, reception units 84a and 84b, and control units 86a and 86b, respectively.
  • the transmitters 82a and 82b are the optical modules of the first embodiment, convert the transmission data signal from the controller 86a into light, and have a wavelength in the space of 1.2 ⁇ m to 1.6 ⁇ m, preferably 1.25 ⁇ m to 1.
  • Laser light 88a and 88b of 35 ⁇ m, for example 1.31 ⁇ m, are emitted.
  • the receivers 84a and 84b include a light receiving element 90 that is a photodiode, and an amplifier 92 that amplifies the current output from the light receiving element 90.
  • the receivers 84a and 84b receive light 88b and 88a having wavelengths of 1.2 ⁇ m to 1.6 ⁇ m, for example 1.31 ⁇ m, emitted from the transmitters 82b and 82a from the space, respectively, and control units 86a and 86b as received data signals. Output to.
  • the data transfer rate when the quantum dot laser is a laser for 10 Gbps optical communication is calculated. Since the image data compressed by the MPEG4-AVC method of 1 hour DVD is 1 Mbps, the data for 3600 seconds is 3.6 Gbit. That is, if the spatial communication system 120 is used, it is possible to transfer this data in one second or less.
  • the wavelength of light used is 1.2 ⁇ m to 1.6 ⁇ m, and it is difficult to damage the eyes, so safety can be ensured.
  • the light output is required to be a certain standard or less from the viewpoint of further safety.
  • a quantum dot laser is used for the transmitters 82a and 82b, a stable light output can be obtained without using an APC circuit. Therefore, it is possible to reduce the optical output to a certain standard or less that can ensure safety and to reduce the cost.
  • the first device 80a and the second device 80b have the same transmission units 82a and 82b and the reception units 84a and 84b has been described, but the first device 80a has the transmission unit 82a.
  • the second device 80b does not have to include the receiving unit 84a, and may include the receiving unit 84b and not include the transmitting unit 82b.
  • the first device 80a and the second device 80b can each be a personal computer. This enables high-speed data communication between personal computers.
  • the first device 80a can be an electronic device such as a mobile phone, a digital camera, and a video camera
  • the second device 80b can be an electronic device such as a personal computer.
  • the image data can be transferred from the first device 80a to the second device 80b in a short time.
  • the first device 80a may be a personal computer and the second device 80b may be a projector. Thereby, image data can be transferred from the personal computer to the projector at high speed.
  • the first device 80a may be mounted on a vehicle, and the second device 80b may be installed on the road or on the ground.
  • image data captured by the vehicle monitoring camera can be temporarily stored in the storage device of the vehicle, and the image data can be periodically transmitted to a device on the road or on the ground.

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Abstract

Disclosed is an optical module provided with a quantum dot laser (60), which has a quantum dot formed on a base layer and a cover layer covering the quantum dot; and a drive circuit (62) which supplies the quantum dot laser with a constant drive current. When the quantum dot laser is used, optical output can be fixed without using an APC circuit.

Description

光モジュール、電子機器および空間通信システムOptical module, electronic device and spatial communication system
　本発明は、光モジュール、電子機器および空間通信システムに関し、特に量子ドットレーザを有する光モジュール、電子機器および空間通信システムに関する。 The present invention relates to an optical module, an electronic device, and a spatial communication system, and more particularly to an optical module, an electronic device, and a spatial communication system having a quantum dot laser.
　レーザ光を出射する光モジュールは、ＦＴＴＨ（fiber to the home）等の光ファイバを用いた光通信システムや光を用いた空間通信システム等の通信システムに用いられている。 Optical modules that emit laser light are used in communication systems such as optical communication systems using optical fibers such as FTTH (fiber-to-the-home) and spatial communication systems using light.
　一方、近年、特許文献１、非特許文献１のように、量子ドットを有する半導体レーザが開発されている。
特開２００１－８５６６５号公報 Electronics Letters 2007 Vol.43 pp670-672 On the other hand, in recent years, as in Patent Document 1 and Non-Patent Document 1, semiconductor lasers having quantum dots have been developed.
JP 2001-85665 A Electronics Letters 2007 Vol.43 pp670-672
　従来の光モジュールの課題について説明する。光ファイバを用いた光通信では光ファイバの光分散特性から波長が１．３μｍ帯または１．５５μｍ帯のレーザ光が用いられる。また、空間通信においては、眼へのダメージの小さい波長が１．２μｍから１．６μｍのレーザ光を用いることが好ましい。図１は、これらの波長で用いられるＩｎＰ系半導体を用いたファブリペロ半導体レーザの駆動電流に対する光出力を各温度に対し示した模式図である。図１において、破線は、製造直後の電流－光出力特性であり、実線は、長期間使用し（つまり長時間通電し）劣化した後の電流－光出力特性である。このように、半導体レーザの電流－光出力特性は、半導体レーザの温度および通電時間に依存し一定ではない。 The problem of the conventional optical module will be described. In optical communication using an optical fiber, laser light having a wavelength of 1.3 μm band or 1.55 μm band is used because of the optical dispersion characteristics of the optical fiber. In spatial communication, it is preferable to use laser light having a wavelength of 1.2 μm to 1.6 μm that causes little damage to the eyes. FIG. 1 is a schematic diagram showing the optical output with respect to the driving current of a Fabry-Perot semiconductor laser using an InP-based semiconductor used at these wavelengths for each temperature. In FIG. 1, the broken line is the current-light output characteristic immediately after manufacture, and the solid line is the current-light output characteristic after being used for a long time (that is, energized for a long time) and deteriorated. As described above, the current-light output characteristics of the semiconductor laser are not constant depending on the temperature and energization time of the semiconductor laser.
　このように半導体レーザの電流－光出力特性は一定ではない。光通信システムにおいては、光モジュールからの光出力が安定していることが求められる。また、空間に光を出射する場合、レーザ光が眼に照射された際の安全性の観点から、光モジュールからの光出力を一定値保つことが求められる。 Thus, the current-light output characteristics of the semiconductor laser are not constant. In an optical communication system, it is required that the optical output from the optical module is stable. In addition, when light is emitted into space, it is required to maintain a constant light output from the optical module from the viewpoint of safety when laser light is applied to the eye.
　そこで、半導体レーザの光出力を目標の光出力に一定に保つためＡＰＣ（Auto Power Control）回路を用いている。図２は従来の光モジュールのブロック図である。図２を参照に、光モジュール１００は、半導体レーザ６０ａ、駆動回路６２ａ、光検出部６４、ＡＰＣ回路６６および入力部６８を有している。入力部６８は外部から送信データ信号７８を受信し、駆動回路６２に送信データ信号を出力する。駆動回路６２ａは、制御信号７６に基づき駆動電流７２の大きさを制御し、半導体レーザ６０ａに駆動電流７２を出力する。駆動回路６２ａは送信データ信号により駆動電流７２を変調する。半導体レーザ６０ａは駆動電流７２に応じた光出力でレーザ光を出射する。駆動電流７２が変調されているため、レーザ光７０は変調されている。 Therefore, an APC (Auto Power Control) circuit is used to keep the optical output of the semiconductor laser constant at the target optical output. FIG. 2 is a block diagram of a conventional optical module. Referring to FIG. 2, the optical module 100 includes a semiconductor laser 60a, a drive circuit 62a, a light detection unit 64, an APC circuit 66, and an input unit 68. The input unit 68 receives a transmission data signal 78 from the outside, and outputs a transmission data signal to the drive circuit 62. The drive circuit 62a controls the magnitude of the drive current 72 based on the control signal 76, and outputs the drive current 72 to the semiconductor laser 60a. The drive circuit 62a modulates the drive current 72 with the transmission data signal. The semiconductor laser 60 a emits a laser beam with an optical output corresponding to the drive current 72. Since the drive current 72 is modulated, the laser beam 70 is modulated.
　例えばフォトダイオードからなる光検出部６４は、半導体レーザ６０ａから出射された光の一部を検知し、半導体レーザ６０ａの光出力に応じたモニタ電流７４をＡＰＣ回路６６に出力する。ＡＰＣ回路６６は、モニタ電流７４と基準電流とを比較し、制御信号７６を駆動回路６２ａに出力する。 For example, the light detection unit 64 made of a photodiode detects a part of the light emitted from the semiconductor laser 60a and outputs a monitor current 74 corresponding to the light output of the semiconductor laser 60a to the APC circuit 66. The APC circuit 66 compares the monitor current 74 with the reference current and outputs a control signal 76 to the drive circuit 62a.
　このように、従来の光モジュールにおいては、光出力を一定に保つためＡＰＣ回路６６を用いている。しかしながら、従来の光モジュールにおいては、ＡＰＣ回路６６ａを用いるため低コスト化が難しいという課題がある。 Thus, in the conventional optical module, the APC circuit 66 is used to keep the optical output constant. However, the conventional optical module has a problem that it is difficult to reduce the cost because the APC circuit 66a is used.
　本発明は、上記課題に鑑みなされたものであり、低コストかつ光安定性に優れた光モジュール、電子機器および空間通信システムを提供することを目的とする。 The present invention has been made in view of the above problems, and an object thereof is to provide an optical module, an electronic device, and a spatial communication system that are low in cost and excellent in light stability.
　本発明は、ベース層上に形成された量子ドットと、前記量子ドットを覆うカバー層と、を有する量子ドットレーザと、一定の駆動電流を前記量子ドットレーザに供給する駆動回路と、を具備することを特徴とする光モジュールである。本発明によれば、量子ドットレーザを用いるため、ＡＰＣ回路を用いなくとも光出力を一定にすることができる。よって、低コストかつ光安定性に優れた光モジュールを提供することができる。 The present invention includes a quantum dot laser having a quantum dot formed on a base layer, a cover layer covering the quantum dot, and a drive circuit for supplying a constant drive current to the quantum dot laser. This is an optical module. According to the present invention, since the quantum dot laser is used, the light output can be made constant without using the APC circuit. Therefore, it is possible to provide an optical module that is low in cost and excellent in light stability.
　上記構成において、前記駆動回路は、前記量子ドットレーザの光出力をフィードバックしていない構成とすることができる。この構成によれば、安価な光モジュールを提供することができる。 In the above configuration, the driving circuit may be configured not to feed back the light output of the quantum dot laser. According to this configuration, an inexpensive optical module can be provided.
　上記構成において、前記ベース層はＧａＡｓからなり、前記カバー層はＩｎＧａＡｓからなり、前記量子ドットはＩｎＡｓからなる構成とすることができる。この構成によれば、量子ドットレーザの光出力の温度依存性を一層抑制することができる。よって、一層光安定性に優れた光モジュールを提供することができる。 In the above configuration, the base layer may be made of GaAs, the cover layer may be made of InGaAs, and the quantum dots may be made of InAs. According to this configuration, the temperature dependence of the optical output of the quantum dot laser can be further suppressed. Therefore, it is possible to provide an optical module that is further excellent in light stability.
　上記構成において、前記量子ドットレーザは空間通信のための光を出射する構成とすることができる。空間通信に用いる光は安全性の観点から、光出力を一定値保つことが求められる。この構成においては、光出力が一定なため、安全性を確保できる。 In the above configuration, the quantum dot laser can emit light for spatial communication. Light used for spatial communication is required to maintain a constant light output from the viewpoint of safety. In this configuration, since the light output is constant, safety can be ensured.
　上記構成において、前記量子ドットレーザの出力波長は、１．２μｍから１．６μｍである構成とすることができる。この構成においては、眼へのダメージを抑制することができる。 In the above configuration, the output wavelength of the quantum dot laser may be 1.2 μm to 1.6 μm. In this configuration, damage to the eyes can be suppressed.
　本発明は、ベース層上に形成された量子ドットと前記量子ドットを覆うカバー層とを有し、空間に１．２μｍから１．６μｍの波長の光を出射する量子ドットレーザと、一定の駆動電流を前記量子ドットレーザに供給する駆動回路と、を有する空間通信用送信部と、空間から１．２μｍから１．６μｍの波長の光を受光する受光素子を有する空間通信用受信部と、を具備することを特徴とする電子機器である。本発明によれば、空間に出射する光として１．２μｍから１．６μｍの波長の光を用いるため、眼へのダメージを抑制することができる。また量子ドットレーザを用いているため、出力を一定値保つことができ、さらなる安全性を確保することができる。また、ＡＰＣ回路を用いなくともよいため、製造コストを削減することができる。 The present invention includes a quantum dot laser having a quantum dot formed on a base layer and a cover layer covering the quantum dot, and emitting light having a wavelength of 1.2 μm to 1.6 μm in a space, and constant driving A spatial communication transmitter having a drive circuit for supplying current to the quantum dot laser, and a spatial communication receiver having a light receiving element that receives light having a wavelength of 1.2 μm to 1.6 μm from the space. An electronic device is provided. According to the present invention, since light having a wavelength of 1.2 μm to 1.6 μm is used as the light emitted to the space, damage to the eyes can be suppressed. Further, since the quantum dot laser is used, the output can be maintained at a constant value, and further safety can be ensured. In addition, since it is not necessary to use an APC circuit, manufacturing cost can be reduced.
　本発明は、ベース層上に形成された量子ドットと、前記量子ドットを覆うカバー層と、を有し空間に１．２μｍから１．６μｍの波長の光を出射する量子ドットレーザと、一定の駆動電流を前記量子ドットレーザに供給する駆動回路と、を有する第１装置と、空間から前記送信装置の前記量子ドットレーザが出射した光を受光する受光素子を有する第２装置と、を具備することを特徴とする空間通信システムである。本発明によれば、安全性に優れ、低コストな空間通信システムを提供することができる。 The present invention includes a quantum dot laser having a quantum dot formed on a base layer and a cover layer covering the quantum dot and emitting light having a wavelength of 1.2 μm to 1.6 μm in a space; A first device having a drive circuit for supplying a drive current to the quantum dot laser, and a second device having a light receiving element that receives light emitted from the quantum dot laser of the transmission device from space. This is a spatial communication system characterized by the above. According to the present invention, it is possible to provide a spatial communication system that is excellent in safety and low in cost.
　本発明は、ベース層上に形成された量子ドットと、前記量子ドットを覆うカバー層と、を有し空間に１．２μｍから１．６μｍの波長の光を出射する量子ドットレーザを有する第１装置と、空間から前記送信装置の前記量子ドットレーザが出射した光を受光する受光素子を有する第２装置と、を具備することを特徴とする空間通信システムである。本発明によれば、安全性に優れ、低コストな空間通信システムを提供することができる。 The present invention includes a first quantum dot laser having a quantum dot formed on a base layer and a cover layer covering the quantum dot and emitting light having a wavelength of 1.2 μm to 1.6 μm in a space. A spatial communication system comprising: a device; and a second device having a light receiving element that receives light emitted from the space by the quantum dot laser of the transmission device. According to the present invention, it is possible to provide a spatial communication system that is excellent in safety and low in cost.
　本発明によれば、量子ドットレーザを用いるため、ＡＰＣ回路を用いなくとも光出力を一定にすることができる。よって、低コストかつ光安定性に優れた光モジュール、電子機器および空間通信システムを提供することができる。 According to the present invention, since the quantum dot laser is used, the light output can be made constant without using the APC circuit. Therefore, it is possible to provide an optical module, an electronic device, and a spatial communication system that are low in cost and excellent in light stability.
図１は、従来の半導体レーザの電流－光出力特性を示す模式図である。FIG. 1 is a schematic diagram showing current-light output characteristics of a conventional semiconductor laser. 図２は、従来の光モジュールを示すブロック図である。FIG. 2 is a block diagram showing a conventional optical module. 図３は、実施例１に係る光モジュールのブロック図である。FIG. 3 is a block diagram of the optical module according to the first embodiment. 図４は、実施例１の量子ドットレーザの断面図である。FIG. 4 is a cross-sectional view of the quantum dot laser of Example 1. 図５は、実施例１の量子ドットレーザの量子ドット付近の拡大断面図である。FIG. 5 is an enlarged cross-sectional view of the vicinity of the quantum dots of the quantum dot laser of Example 1. 図６は、量子ドットレーザにおける電流－光出力特性の温度依存を示す図である。FIG. 6 is a diagram showing temperature dependence of current-light output characteristics in a quantum dot laser. 図７（ａ）および図７（ｂ）は、量子ドットレーザにおける通電時間に対する劣化を調査した結果の図である。FIGS. 7A and 7B are diagrams showing the results of investigating the deterioration with respect to the energization time in the quantum dot laser. 図８は、実施例２に係る空間通信システムのブロック図である。FIG. 8 is a block diagram of a spatial communication system according to the second embodiment.
発明を実施するための形態BEST MODE FOR CARRYING OUT THE INVENTION
　以下、図面を参考に本発明の実施例について説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
　図３は実施例１に係る光モジュールのブロック図である。図３を参照に、実施例１に係る光モジュール１００は受光素子およびＡＰＣ回路を有していない。半導体レーザ６０ａとして、量子ドットレーザを用いている。 FIG. 3 is a block diagram of the optical module according to the first embodiment. Referring to FIG. 3, the optical module 100 according to the first embodiment does not include a light receiving element and an APC circuit. A quantum dot laser is used as the semiconductor laser 60a.
　以下に量子ドットレーザの構造および特徴を説明する。図４は量子ドットファブリペロレーザ５０の断面模式図である。図４を参照に、ｐ型ＡｌＧａＡｓクラッド層１０上にＧａＡｓベース層１２および量子ドット活性層が５層積層されている。ベース層１２上に、ｎ型ＡｌＧａＡｓクラッド層１４が形成されている。ｎ型ＡｌＧａＡｓクラッド層１４は孤立しており、量子ドットレーザ５０はリッジ構造を有している。ｎ型ＡｌＧａＡｓクラッド層１４上にはｎ電極１６、ｐ型ＡｌＧａＡｓクラッド層１０下にはｐ電極１８が形成されている。ｎ型ＡｌＧａＡｓクラッド層１４の幅は１．８μｍ、長さは０．２５ｍｍである。 The structure and features of the quantum dot laser will be described below. FIG. 4 is a schematic sectional view of the quantum dot Fabry-Perot laser 50. Referring to FIG. 4, five GaAs base layers 12 and five quantum dot active layers are stacked on a p-type AlGaAs cladding layer 10. An n-type AlGaAs cladding layer 14 is formed on the base layer 12. The n-type AlGaAs cladding layer 14 is isolated, and the quantum dot laser 50 has a ridge structure. An n-electrode 16 is formed on the n-type AlGaAs cladding layer 14, and a p-electrode 18 is formed below the p-type AlGaAs cladding layer 10. The n-type AlGaAs cladding layer 14 has a width of 1.8 μm and a length of 0.25 mm.
　図５は、量子ドット活性層およびベース層１２を拡大した図である。膜厚が約５０ｎｍのＧａＡｓベース層１２上に、膜厚が約２ｎｍの第１ＩｎＧａＡｓ層２２が形成されている。第１ＩｎＧａＡｓ層２２上にＩｎＡｓからなる複数の量子ドット３０が形成されている。量子ドット３０を覆うように、膜厚が６ｎｍの第２ＩｎＧａＡｓ層２４が形成されている。第１ＩｎＧａＡｓ層２２および第２ＩｎＧａＡｓ層２４はカバー層２０を構成しており、それぞれのＩｎ組成比は、０．１５、０．２である。第２ＩｎＧａＡｓ層２４上にＧａＡｓベース層１２が形成されている。 FIG. 5 is an enlarged view of the quantum dot active layer and the base layer 12. A first InGaAs layer 22 having a thickness of about 2 nm is formed on the GaAs base layer 12 having a thickness of about 50 nm. A plurality of quantum dots 30 made of InAs are formed on the first InGaAs layer 22. A second InGaAs layer 24 having a thickness of 6 nm is formed so as to cover the quantum dots 30. The first InGaAs layer 22 and the second InGaAs layer 24 constitute the cover layer 20, and the respective In composition ratios are 0.15 and 0.2. A GaAs base layer 12 is formed on the second InGaAs layer 24.
　図６は、量子ドットレーザ５０の各温度における電流－光出力特性を示す図である。図６のように、量子ドットレーザ５０の電流－光出力特性の温度依存性は小さい。このように、ベース層１２がＧａＡｓからなり、カバー層２０がＩｎＧａＡｓからなり、量子ドット３０がＩｎＡｓからなる。これにより、光出力の温度依存性を抑制することができる。 FIG. 6 is a diagram showing current-light output characteristics at each temperature of the quantum dot laser 50. As shown in FIG. 6, the temperature dependency of the current-light output characteristics of the quantum dot laser 50 is small. Thus, the base layer 12 is made of GaAs, the cover layer 20 is made of InGaAs, and the quantum dots 30 are made of InAs. Thereby, the temperature dependence of light output can be suppressed.
　図７（ａ）は、量子ドットレーザ５０に通電することによる光出力の劣化を示す図であり、量子ドットレーザ５０を図２の光モジュールの半導体レーザ６０ａとして用い、駆動電流Ｉを経過時間に対し図示している。図７（ｂ）は、駆動電流Ｉの通電開始時の駆動電流Ｉｓｔａｒｔからの変化量（Ｉ－Ｉｓｔａｒｔ）とＩｓｔａｒｔとの比を示した図である。環境温度が９０℃において、２ｍＷの光出力を得られるようにＡＰＣ回路６６で駆動電流を制御している。図７（ａ）および図７（ｂ）における複数の線は、それぞれ複数の量子ドットレーザ５０の駆動電流Ｉを示している。図７（ａ）および図７（ｂ）より、通電試験を行っても量子ドットレーザ５０の駆動電流Ｉはほぼ一定である。言い換えれば、量子ドットレーザ５０の駆動電流Ｉを一定として通電しても光出力はほぼ一定である。以上のように、量子ドットレーザ５０は温度および通電時間に対し電流－光出力特性がほぼ一定である。 FIG. 7A is a diagram showing deterioration of optical output due to energization of the quantum dot laser 50. The quantum dot laser 50 is used as the semiconductor laser 60a of the optical module in FIG. On the other hand, it is illustrated. FIG. 7B is a diagram showing a ratio between the change amount (I-I start ) from the drive current I start at the start of energization of the drive current I and I start . The drive current is controlled by the APC circuit 66 so that an optical output of 2 mW can be obtained at an environmental temperature of 90 ° C. The plurality of lines in FIGS. 7A and 7B indicate the drive currents I of the plurality of quantum dot lasers 50, respectively. From FIG. 7A and FIG. 7B, the driving current I of the quantum dot laser 50 is substantially constant even when the energization test is performed. In other words, the light output is almost constant even when the driving current I of the quantum dot laser 50 is kept constant. As described above, the quantum dot laser 50 has substantially constant current-light output characteristics with respect to temperature and energization time.
　実施例１に係る光モジュール１００は、図３のように、量子ドットレーザ５０と、一定の駆動電流７２を量子ドットレーザ６０に供給する駆動回路６２と、を有している。このように、半導体レーザとして量子ドットレーザ５０を用いることにより、一定の駆動電流７２を量子ドットレーザ５０に供給する駆動回路６２を用いても量子ドットレーザ５０は一定の光出力でレーザ光を出力することができる。よって、図２のようなＡＰＣ回路が不要となる。つまり、駆動回路６２は、量子ドットレーザ６０の光出力をフィードバックしていない。このため、光出力が一定でかつ低コスト化が可能となる。 The optical module 100 according to the first embodiment includes a quantum dot laser 50 and a drive circuit 62 that supplies a constant drive current 72 to the quantum dot laser 60 as shown in FIG. Thus, by using the quantum dot laser 50 as a semiconductor laser, the quantum dot laser 50 outputs laser light with a constant light output even when the driving circuit 62 that supplies the constant driving current 72 to the quantum dot laser 50 is used. can do. Therefore, the APC circuit as shown in FIG. 2 is not necessary. That is, the drive circuit 62 does not feed back the light output of the quantum dot laser 60. For this reason, the light output is constant and the cost can be reduced.
　実施例２は、実施例１を用いた空間通信システムの例である。図８は、実施例２に係る空間通信システムのブロック図である。図８を参照に、空間通信システム１２０は、第１装置８０ａおよび第２装置８０ｂを有している。第１装置８０ａおよび第２装置８０ｂはそれぞれ送信部８２ａおよび８２ｂ、受信部８４ａおよび８４ｂ並びに制御部８６ａおよび８６ｂを有している。送信部８２ａおよび８２ｂは実施例１の光モジュールであり、制御部８６ａからの送信データ信号を光に変換し、空間に波長が１．２μｍから１．６μｍ、好ましくは、１．２５μｍから１．３５μｍ、例えば１．３１μｍのレーザ光８８ａおよび８８ｂを出射する。受信部８４ａおよび８４ｂは、フォトダイオードである受光素子９０と、受光素子９０が出力する電流を増幅する増幅器９２とを有している。受信部８４ａおよび８４ｂは、送信部８２ｂおよび８２ａが出射した波長が１．２μｍから１．６μｍ、例えば１．３１μｍの光８８ｂおよび８８ａをそれぞれ空間から受光し、受信データ信号として制御部８６ａおよび８６ｂに出力する。 Example 2 is an example of a spatial communication system using Example 1. FIG. 8 is a block diagram of a spatial communication system according to the second embodiment. Referring to FIG. 8, the spatial communication system 120 includes a first device 80a and a second device 80b. The first device 80a and the second device 80b have transmission units 82a and 82b, reception units 84a and 84b, and control units 86a and 86b, respectively. The transmitters 82a and 82b are the optical modules of the first embodiment, convert the transmission data signal from the controller 86a into light, and have a wavelength in the space of 1.2 μm to 1.6 μm, preferably 1.25 μm to 1. Laser light 88a and 88b of 35 μm, for example 1.31 μm, are emitted. The receivers 84a and 84b include a light receiving element 90 that is a photodiode, and an amplifier 92 that amplifies the current output from the light receiving element 90. The receivers 84a and 84b receive light 88b and 88a having wavelengths of 1.2 μm to 1.6 μm, for example 1.31 μm, emitted from the transmitters 82b and 82a from the space, respectively, and control units 86a and 86b as received data signals. Output to.
　例えば、量子ドットレーザが、１０Ｇｂｐｓ光通信用のレーザである場合のデータ転送速度を計算する。１時間のＤＶＤのＭＰＥＧ４－ＡＶＣ方式で圧縮された画像データは１Ｍｂｐｓであるから、３６００秒分のデータは３．６Ｇｂｉｔとなる。すなわち、空間通信システム１２０を用いれば、１秒以下でこのデータを転送することが可能である。 For example, the data transfer rate when the quantum dot laser is a laser for 10 Gbps optical communication is calculated. Since the image data compressed by the MPEG4-AVC method of 1 hour DVD is 1 Mbps, the data for 3600 seconds is 3.6 Gbit. That is, if the spatial communication system 120 is used, it is possible to transfer this data in one second or less.
　さらに、実施例２においては、用いる光の波長が１．２μｍから１．６μｍであり、眼にダメージを与えにくいため、安全性を確保できる。しかしながら、このような波長を用いる場合も、さらなる安全性の観点から、光出力を一定基準以下とすることが求められる。実施例２では、送信部８２ａおよび８２ｂに量子ドットレーザを用いているため、ＡＰＣ回路を用いず安定な光出力を得ることができる。よって、光出力を安全性が確保可能な一定基準以下としかつ低コスト化が可能となる。 Furthermore, in Example 2, the wavelength of light used is 1.2 μm to 1.6 μm, and it is difficult to damage the eyes, so safety can be ensured. However, even when such a wavelength is used, the light output is required to be a certain standard or less from the viewpoint of further safety. In the second embodiment, since a quantum dot laser is used for the transmitters 82a and 82b, a stable light output can be obtained without using an APC circuit. Therefore, it is possible to reduce the optical output to a certain standard or less that can ensure safety and to reduce the cost.
　実施例２においては、第１装置８０ａおよび第２装置８０ｂとも同じ送信部８２ａおよび８２ｂ、受信部８４ａおよび８４ｂを有している例を説明したが、第１装置８０ａは送信部８２ａを有し受信部８４ａを有さず、第２装置８０ｂは受信部８４ｂを有し送信部８２ｂを有さなくてもよい。 In the second embodiment, the example in which both the first device 80a and the second device 80b have the same transmission units 82a and 82b and the reception units 84a and 84b has been described, but the first device 80a has the transmission unit 82a. The second device 80b does not have to include the receiving unit 84a, and may include the receiving unit 84b and not include the transmitting unit 82b.
　本空間通信システム１２０として、第１装置８０ａおよび第２装置８０ｂをそれぞれパーソナルコンピュータとすることができる。これにより、パーソナルコンピュータ間で高速のデータ通信が可能となる。また、例えば、第１装置８０ａを携帯電話、デジタルカメラ、ビデオカメラ等の電子機器とし、第２装置８０ｂをパーソナルコンピュータ等の電子機器とすることができる。これにより、画像データを第１装置８０ａから第２装置８０ｂに短時間で転送することができる。さらに、第１装置８０ａをパーソナルコンピュータ、第２装置８０ｂをプロジェクタとしてもよい。これにより、パーソナルコンピュータからプロジェクタに高速に画像データを転送することができる。さらに、第１装置８０ａを車両に搭載し、第２装置８０ｂを路上や地上に設置してもよい。これにより、例えば車両の監視カメラが撮影した画像データを車両の記憶装置に一時記憶し、画像データを定期的に路上や地上の装置に送信することができる。 As the spatial communication system 120, the first device 80a and the second device 80b can each be a personal computer. This enables high-speed data communication between personal computers. Further, for example, the first device 80a can be an electronic device such as a mobile phone, a digital camera, and a video camera, and the second device 80b can be an electronic device such as a personal computer. Thereby, the image data can be transferred from the first device 80a to the second device 80b in a short time. Further, the first device 80a may be a personal computer and the second device 80b may be a projector. Thereby, image data can be transferred from the personal computer to the projector at high speed. Further, the first device 80a may be mounted on a vehicle, and the second device 80b may be installed on the road or on the ground. As a result, for example, image data captured by the vehicle monitoring camera can be temporarily stored in the storage device of the vehicle, and the image data can be periodically transmitted to a device on the road or on the ground.
　以上、発明の好ましい実施例について詳述したが、本発明は係る特定の実施例に限定されるものではなく、特許請求の範囲に記載された本発明の要旨の範囲内において、種々の変形・変更が可能である。 The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

Claims (8)

  1. 　ベース層上に形成された量子ドットと、前記量子ドットを覆うカバー層と、を有する量子ドットレーザと、
    　一定の駆動電流を前記量子ドットレーザに供給する駆動回路と、
    　を具備することを特徴とする光モジュール。     A quantum dot laser having quantum dots formed on the base layer and a cover layer covering the quantum dots;
    A drive circuit for supplying a constant drive current to the quantum dot laser;
    An optical module comprising:
  2. 　前記駆動回路は、前記量子ドットレーザの光出力をフィードバックしていないことを特徴とする請求項１記載の光モジュール。 2. The optical module according to claim 1, wherein the drive circuit does not feed back the optical output of the quantum dot laser.
  3. 　前記ベース層はＧａＡｓからなり、前記カバー層はＩｎＧａＡｓからなり、前記量子ドットはＩｎＡｓからなることを特徴とする請求項１または２記載の光モジュール。 3. The optical module according to claim 1, wherein the base layer is made of GaAs, the cover layer is made of InGaAs, and the quantum dots are made of InAs.
  4. 　前記量子ドットレーザは空間通信のための光を出射することを特徴とする請求項１から３のいずれか一項記載の光モジュール。 The optical module according to any one of claims 1 to 3, wherein the quantum dot laser emits light for spatial communication.
  5. 　前記量子ドットレーザの出力波長は、１．２μｍから１．６μｍであることを特徴とする請求項４記載の光モジュール。 The optical module according to claim 4, wherein an output wavelength of the quantum dot laser is 1.2 μm to 1.6 μm.
  6. 　ベース層上に形成された量子ドットと前記量子ドットを覆うカバー層とを有し、空間に１．２μｍから１．６μｍの波長の光を出射する量子ドットレーザと、一定の駆動電流を前記量子ドットレーザに供給する駆動回路と、を有する空間通信用送信部と、
    　空間から１．２μｍから１．６μｍの波長の光を受光する受光素子を有する空間通信用受信部と、
    を具備する電子機器。     A quantum dot laser having a quantum dot formed on the base layer and a cover layer covering the quantum dot and emitting light having a wavelength of 1.2 μm to 1.6 μm in the space; A drive circuit for supplying to the dot laser, and a spatial communication transmitter,
    A spatial communication receiver having a light receiving element that receives light having a wavelength of 1.2 μm to 1.6 μm from the space;
    An electronic device comprising:
  7. 　ベース層上に形成された量子ドットと、前記量子ドットを覆うカバー層と、を有し空間に１．２μｍから１．６μｍの波長の光を出射する量子ドットレーザと、一定の駆動電流を前記量子ドットレーザに供給する駆動回路と、を有する第１装置と、
    　空間から前記送信装置の前記量子ドットレーザが出射した光を受光する受光素子を有する第２装置と、
    を具備する空間通信システム。     A quantum dot laser formed on a base layer; a cover layer covering the quantum dots; a quantum dot laser that emits light having a wavelength of 1.2 μm to 1.6 μm; and a constant driving current A first device having a drive circuit for supplying to the quantum dot laser;
    A second device having a light receiving element that receives light emitted from the quantum dot laser of the transmission device from space;
    A spatial communication system comprising:
  8. 　ベース層上に形成された量子ドットと、前記量子ドットを覆うカバー層と、を有し空間に１．２μｍから１．６μｍの波長の光を出射する量子ドットレーザを有する第１装置と、
    　空間から前記送信装置の前記量子ドットレーザが出射した光を受光する受光素子を有する第２装置と、
    を具備する空間通信システム。     A first device having a quantum dot laser that emits light having a wavelength of 1.2 μm to 1.6 μm in a space, the quantum dots formed on the base layer; and a cover layer covering the quantum dots;
    A second device having a light receiving element that receives light emitted from the quantum dot laser of the transmission device from space;
    A spatial communication system comprising:
PCT/JP2009/051494 2008-02-06 2009-01-29 Optical module, electronic device and spatial communication system WO2009098999A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011046004A1 (en) * 2009-10-13 2011-04-21 株式会社Ｑｄレーザ Optical transmission/reception device

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Optical Fiber Communication Conference, 2006 and the 2006 National Fiber Optic Engineers Conference. OFC 2006, 2006.03", article YAMABANA T. ET AL.: "Temperature independent transmission for 10 Gbps 300m-MMF using low driving-current quantum dot laser" *
OTSUBO K. ET AL.: "Temperature-Insensitive Eye- Opening under 10-Gb/s Modulation of 1.3-pm P- Doped Quantum-Dot Lasers without Current Adjustments", JAPANESE JOURNAL OF APPLIED PHYSICS, vol. 43, no. 8B, 2004, pages L1124 - L1126 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011046004A1 (en) * 2009-10-13 2011-04-21 株式会社Ｑｄレーザ Optical transmission/reception device

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