JPH09107156A - Semiconductor laser - Google Patents
Semiconductor laserInfo
- Publication number
- JPH09107156A JPH09107156A JP7290277A JP29027795A JPH09107156A JP H09107156 A JPH09107156 A JP H09107156A JP 7290277 A JP7290277 A JP 7290277A JP 29027795 A JP29027795 A JP 29027795A JP H09107156 A JPH09107156 A JP H09107156A
- Authority
- JP
- Japan
- Prior art keywords
- oscillation
- reflectance
- wavelength
- semiconductor laser
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、共振条件を満た
す波長に対して反射率に波長依存性を有する反射防止膜
を備えるようにした半導体レーザに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser provided with an antireflection film having a wavelength dependence of reflectance with respect to a wavelength satisfying a resonance condition.
【０００２】[0002]
【従来の技術】高出力の半導体レーザでは、発振効率を
向上させる目的で、レーザ素子の出射側の劈開面Ｒ１
に、反射防止（ＡＲ）膜を被着し、これに対向する劈開
面Ｒ２に、反射増強（ＨＲ）膜を被着することがなされ
ている。2. Description of the Related Art In a high-power semiconductor laser, a cleavage plane R1 on the emitting side of a laser element is used for the purpose of improving the oscillation efficiency.
Then, an antireflection (AR) film is deposited on the first surface, and a reflection enhancing (HR) film is deposited on the cleavage plane R2 facing the antireflection (AR) film.
【０００３】[0003]
【発明が解決しようとする課題】ところで、半導体レー
ザの性能を表す一つのパラメータとして注入電流−光出
力特性の傾きを表す微分量子効率ηｄが挙げられる。こ
の微分量子効率ηｄ（相対値）は、図４に示すように、
半導体レーザの出射面Ｒ１の反射率が低いほど向上す
る。しかしながら、半導体レーザの出射面Ｒ１の反射率
を低下させると、図５に示すように、もう一つの性能評
価のパラメータである発振しきい値ｇｔｈ（相対値）が
増大してしまうという問題がある。このため、反射防止
膜の反射率は、両者のバランスを考慮して、約５％程度
に制限されている。By the way, the differential quantum efficiency ηd, which represents the slope of the injection current-optical output characteristic, is one parameter that represents the performance of the semiconductor laser. This differential quantum efficiency ηd (relative value) is as shown in FIG.
The higher the reflectance of the emission surface R1 of the semiconductor laser, the higher the improvement. However, if the reflectance of the emitting surface R1 of the semiconductor laser is reduced, as shown in FIG. 5, there is a problem that the oscillation threshold value gth (relative value), which is another parameter for performance evaluation, increases. . Therefore, the reflectance of the antireflection film is limited to about 5% in consideration of the balance between the two.
【０００４】この発明は、このような問題点に鑑みなさ
れたもので、発振しきい値の低減と微分量子効率の向上
とを同時に図ることができる半導体レーザを提供するこ
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 a semiconductor laser capable of simultaneously reducing the oscillation threshold and improving the differential quantum efficiency.
【０００５】[0005]
【課題を解決するための手段】この発明に係る半導体レ
ーザは、注入電流の増加に伴いレーザ光の発振波長がシ
フトする半導体レーザにおいて、発振しきい値電流の注
入時の発振波長に対する反射率が、前記発振しきい値電
流よりも大きな電流の注入時の発振波長に対する反射率
より大となる分光反射率特性を有する反射防止膜をレー
ザ光の出射端面に被着してなることを特徴とする。A semiconductor laser according to the present invention is a semiconductor laser in which the oscillation wavelength of laser light shifts with an increase in injection current, and the reflectance for the oscillation wavelength at the time of injection of an oscillation threshold current is And an antireflection film having a spectral reflectance characteristic that is greater than a reflectance with respect to an oscillation wavelength when a current larger than the oscillation threshold current is injected is attached to the emission end face of the laser light. .
【０００６】本発明によれば、注入電流の増加に伴って
発振波長がシフトするという半導体レーザの性質を利用
して、反射率が前述した波長依存性を有する反射防止膜
をレーザ光の出射端面に被着するようにしているので、
発振しきい値電流注入時の発振波長に対しては高い反射
率となって、発振しきい値を低く抑えることができ、注
入電流を増加して発振波長がシフトするに伴い反射率が
低下するようにして、高出力時の微分量子効率を向上さ
せることができる。According to the present invention, by utilizing the property of the semiconductor laser that the oscillation wavelength shifts with the increase of the injection current, the antireflection film having the above-mentioned wavelength dependence of the reflectance is formed on the emitting end face of the laser light. Because I am trying to wear
The reflectance becomes high with respect to the oscillation wavelength when the oscillation threshold current is injected, and the oscillation threshold can be kept low. The reflectance decreases as the injection current increases and the oscillation wavelength shifts. In this way, the differential quantum efficiency at high output can be improved.
【０００７】なお、反射防止膜が、発振しきい値電流よ
りも大きな所定の電流の注入時の発振波長で、反射率が
極小値となるような分光反射率特性を有していると、任
意の特定波長での微分量子効率を最大にした状態で、多
モード発振によって生じた余分な波長成分を抑制して、
コヒーレンスの高い光出力を得ることができる。It is to be noted that if the antireflection film has a spectral reflectance characteristic such that the reflectance has a minimum value at an oscillation wavelength when a predetermined current larger than the oscillation threshold current is injected, it is optional. In the state where the differential quantum efficiency at the specific wavelength of is maximized, the extra wavelength component generated by the multimode oscillation is suppressed,
An optical output with high coherence can be obtained.
【０００８】[0008]
【発明の実施の形態】以下、図面を参照して、この発明
の実施の形態について説明する。図１は、この発明の一
実施例に係る半導体レーザの概略構成を示す斜視図であ
る。半導体レーザ１は、例えばｐ−ＩｎＰからなるＰ型
クラッド層２と、ｎ−ＩｎＰからなるＮ型クラッド層３
との間にＧａＩｎＡｓＰからなるダブルヘテロ接合構造
の導波路活性層４を設け、クラッド層２，３等の上下面
にＡｌ等の電極５，６をそれぞれ設けると共に、出射側
の劈開面Ｒ１に反射防止膜７を、また、これに対向する
劈開面Ｒ２に反射増強膜８をそれぞれ被着してなるもの
である。Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of a semiconductor laser according to an embodiment of the present invention. The semiconductor laser 1 includes, for example, a P-type cladding layer 2 made of p-InP and an N-type cladding layer 3 made of n-InP.
And a waveguide active layer 4 of a double heterojunction structure made of GaInAsP, and electrodes 5 and 6 made of Al or the like on the upper and lower surfaces of the cladding layers 2 and 3, respectively, and reflected on the cleavage plane R1 on the emitting side. The antireflection film 7 and the reflection enhancing film 8 are attached to the cleavage plane R2 facing the antireflection film 7, respectively.
【０００９】反射防止膜７は、例えば図２に示すよう
に、特定波長（１５２０［ｎｍ］）でその反射率が極小
値となる分光反射率特性を有するものである。このよう
な特性を持つ反射防止膜７は、複数の異なる屈折率の誘
電体層（例えば、ＴｉＯ2 とＳｉＯ2 との組み合わせ、
又はＴａ2 Ｏ5 とＳｉＯ2 との組み合わせ等）を交互に
積層してなる光学多層膜フィルタにより実現することが
できる。また、反射増強膜８は、例えば９０％以上の反
射率を有している。As shown in FIG. 2, for example, the antireflection film 7 has a spectral reflectance characteristic in which its reflectance has a minimum value at a specific wavelength (1520 [nm]). The antireflection film 7 having such characteristics has a plurality of dielectric layers having different refractive indexes (for example, a combination of TiO 2 and SiO 2 ,
Alternatively, a combination of Ta 2 O 5 and SiO 2 etc.) may be alternately laminated to realize an optical multilayer filter. The reflection enhancing film 8 has a reflectance of 90% or more, for example.
【００１０】次に、このように構成された半導体レーザ
１の動作について説明する。図３（ａ）は半導体レーザ
１に１００［ｍＡ］の電流を注入したときに発振するレ
ーザ光のスペクトルの一例を示す図、図３（ｂ）は半導
体１に５００［ｍＡ］の電流を注入したときに発振する
レーザ光のスペクトルの一例を示す図である。１００
［ｍＡ］の電流を注入すると、レーザ光の発振波長は１
５０５［ｎｍ］となり、その発振出力は１０．９［μ
Ｗ］となる。また、５００［ｍＡ］の電流を注入する
と、レーザ光の発振波長は１５２１［ｎｍ］となり、そ
の発振出力は３０．８［μＷ］となる。従って、注入電
流が増加するに従い、レーザ光の発振波長は長波長側に
シフトする。Next, the operation of the semiconductor laser 1 thus constructed will be described. FIG. 3A is a diagram showing an example of a spectrum of laser light that oscillates when a current of 100 [mA] is injected into the semiconductor laser 1, and FIG. 3B is injected with a current of 500 [mA] into the semiconductor 1. It is a figure which shows an example of the spectrum of the laser beam which oscillates when it does. 100
When a current of [mA] is injected, the oscillation wavelength of laser light is 1
505 [nm], and the oscillation output is 10.9 [μ
W]. When a current of 500 [mA] is injected, the oscillation wavelength of the laser light becomes 1521 [nm], and the oscillation output becomes 30.8 [μW]. Therefore, the oscillation wavelength of the laser light shifts to the long wavelength side as the injection current increases.
【００１１】いま、この半導体レーザ１の発振しきい値
電流が１００［ｍＡ］、最大出力時の注入電流が５００
［ｍＡ］であるとすると、図２に示すように、出射面Ｒ
１に被着された反射防止膜７の分光反射率曲線は、発振
しきい値電流（＝１００［ｍＡ］）に対応したレーザ光
の発振波長（＝１５０５［ｎｍ］）での反射率が約３０
％と高い値を示すので、低い発振しきい値が得られる。
また、反射防止膜７の分光反射率曲線は、レーザ光の発
振出力が最大となる波長（＝１５２１［ｎｍ］）で極小
となり、そのときの反射率は約０．５％となる。このた
め、レーザ光の発振出力が最大となる大電流注入時にお
いては、高い微分量子効率ηｄを得ることができる。Now, the oscillation threshold current of the semiconductor laser 1 is 100 [mA], and the injection current at the maximum output is 500.
If it is [mA], as shown in FIG.
The spectral reflectance curve of the antireflection film 7 applied to No. 1 shows that the reflectance at the oscillation wavelength (= 1505 [nm]) of the laser light corresponding to the oscillation threshold current (= 100 [mA]) is approximately. Thirty
%, A low oscillation threshold is obtained.
Further, the spectral reflectance curve of the antireflection film 7 has a minimum at the wavelength (= 1521 [nm]) where the oscillation output of the laser light is maximum, and the reflectance at that time is about 0.5%. Therefore, a high differential quantum efficiency ηd can be obtained at the time of injecting a large current that maximizes the oscillation output of the laser light.
【００１２】なお、上記実施例では、反射防止膜７の分
光反射率曲線に極小値を持たせたが、必ずしも分光反射
率曲線に極小値を持たせる必要はない。即ち、本発明
は、発振しきい値電流から最大出力時の注入電流に至る
反射率が徐々に低下するような特性であれば、例えば反
射防止膜７を分光反射率曲線における長波長領域が平坦
となる特性としても良い。In the above embodiment, the spectral reflectance curve of the antireflection film 7 has a minimum value, but the spectral reflectance curve does not necessarily have a minimum value. That is, in the present invention, if the reflectance from the oscillation threshold current to the injection current at the maximum output gradually decreases, for example, the antireflection film 7 has a flat long wavelength region in the spectral reflectance curve. It may be a characteristic that
【００１３】以上、レーザ媒体の発振波長のエネルギ依
存性に着目し、反射防止膜の反射率に波長依存性を持た
せた場合について説明したが、本発明は、また、レーザ
媒体の発振波長が温度依存性を持つ場合、温度上昇時の
発振波長に対する反射率が小さくなるような反射防止膜
を使用することにより、温度上昇時の微分量子効率の低
下を防止することができるという利点がある。As described above, the energy dependence of the oscillation wavelength of the laser medium has been focused on, and the case where the reflectance of the antireflection film has the wavelength dependence has been described. In the case of having temperature dependence, by using an antireflection film whose reflectance with respect to the oscillation wavelength when temperature rises is used, there is an advantage that it is possible to prevent a decrease in differential quantum efficiency when temperature rises.
【００１４】[0014]
【発明の効果】以上述べたように、この発明によれば、
注入電流の増加に伴って発振波長がシフトするという半
導体レーザの性質を利用して、反射率が前述した波長依
存性を有する反射防止膜をレーザ光の出射端面に被着す
るようにしているので、発振しきい値電流注入時の発振
波長に対しては高い反射率となって、発振しきい値を低
く抑えることができ、注入電流を増加して発振波長がシ
フトするに伴い反射率が低下するようにして、高出力時
の微分量子効率を向上させることができる。As described above, according to the present invention,
By utilizing the property of the semiconductor laser that the oscillation wavelength shifts with the increase of the injection current, the antireflection film having the wavelength dependence of the reflectance described above is applied to the emission end face of the laser light. , The reflectance becomes high for the oscillation wavelength when the oscillation threshold current is injected, and the oscillation threshold can be kept low. The reflectance decreases as the injection current increases and the oscillation wavelength shifts. By doing so, the differential quantum efficiency at high output can be improved.
【図１】 この発明の一実施例に係る半導体レーザの概
略構成を示す斜視図である。FIG. 1 is a perspective view showing a schematic configuration of a semiconductor laser according to an embodiment of the present invention.
【図２】 反射防止膜の光学特性の一例を示す図であ
る。FIG. 2 is a diagram showing an example of optical characteristics of an antireflection film.
【図３】 注入電流時におけるレーザ光のスペクトルの
一例を示す図である。FIG. 3 is a diagram showing an example of a spectrum of laser light at the time of injection current.
【図４】 端面反射率と微分効率との関係を説明するた
めの図である。FIG. 4 is a diagram for explaining the relationship between end face reflectance and differential efficiency.
【図５】 端面反射率と発振しきい値との関係を説明す
るための図である。FIG. 5 is a diagram for explaining a relationship between an end face reflectance and an oscillation threshold value.
１…半導体レーザ、２…Ｐ型クラッド層、３…Ｎ型クラ
ッド層、４…導波路活性層、５，６…電極、７…反射防
止膜、８…反射増強膜、Ｒ１，Ｒ２…劈開面。DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... P-type clad layer, 3 ... N-type clad layer, 4 ... Waveguide active layer, 5, 6 ... Electrode, 7 ... Antireflection film, 8 ... Antireflection film, R1, R2 ... Cleaved surface .
Claims (2)
長がシフトする半導体レーザにおいて、 発振しきい値電流の注入時の発振波長に対する反射率
が、前記発振しきい値電流よりも大きな電流の注入時の
発振波長に対する反射率より大となる分光反射率特性を
有する反射防止膜をレーザ光の出射端面に被着してなる
ことを特徴とする半導体レーザ。1. A semiconductor laser in which the oscillation wavelength of laser light shifts with an increase in injection current, and the reflectance of the oscillation threshold current with respect to the oscillation wavelength at the time of injection is larger than that of the oscillation threshold current. A semiconductor laser comprising an antireflection film having a spectral reflectance characteristic that is greater than the reflectance for the oscillation wavelength at the time of injection, and is attached to the emission end face of the laser light.
流よりも大きな所定の電流の注入時の発振波長で反射率
が極小値となる分光反射率特性を有するものであること
を特徴とする請求項１記載の半導体レーザ。2. The antireflection film has a spectral reflectance characteristic in which the reflectance has a minimum value at an oscillation wavelength when a predetermined current larger than the oscillation threshold current is injected. The semiconductor laser according to claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7290277A JPH09107156A (en) | 1995-10-12 | 1995-10-12 | Semiconductor laser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7290277A JPH09107156A (en) | 1995-10-12 | 1995-10-12 | Semiconductor laser |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09107156A true JPH09107156A (en) | 1997-04-22 |
Family
ID=17754065
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7290277A Pending JPH09107156A (en) | 1995-10-12 | 1995-10-12 | Semiconductor laser |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09107156A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005072488A (en) * | 2003-08-27 | 2005-03-17 | Mitsubishi Electric Corp | Semiconductor laser |
| US7103081B2 (en) | 2002-10-18 | 2006-09-05 | Sumitomo Electric Industries, Ltd. | DFB laser with ar coating selected to provide wide temperature range of operation |
| JP2008244300A (en) * | 2007-03-28 | 2008-10-09 | Mitsubishi Electric Corp | Semiconductor laser |
-
1995
- 1995-10-12 JP JP7290277A patent/JPH09107156A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7103081B2 (en) | 2002-10-18 | 2006-09-05 | Sumitomo Electric Industries, Ltd. | DFB laser with ar coating selected to provide wide temperature range of operation |
| JP2005072488A (en) * | 2003-08-27 | 2005-03-17 | Mitsubishi Electric Corp | Semiconductor laser |
| JP2008244300A (en) * | 2007-03-28 | 2008-10-09 | Mitsubishi Electric Corp | Semiconductor laser |
| DE102007053328A1 (en) | 2007-03-28 | 2008-10-09 | Mitsubishi Electric Corp. | Semiconductor laser with Fabry-Perot resonator |
| US7627010B2 (en) | 2007-03-28 | 2009-12-01 | Mitsubishi Electric Corporation | Semiconductor laser having Fabry-Perot resonator |
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