JPS6223186A - Distributed feedback type semiconductor laser - Google Patents

Distributed feedback type semiconductor laser

Info

Publication number
JPS6223186A
JPS6223186A JP60162574A JP16257485A JPS6223186A JP S6223186 A JPS6223186 A JP S6223186A JP 60162574 A JP60162574 A JP 60162574A JP 16257485 A JP16257485 A JP 16257485A JP S6223186 A JPS6223186 A JP S6223186A
Authority
JP
Japan
Prior art keywords
gap
region
active layer
refractive index
distributed feedback
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
Application number
JP60162574A
Other languages
Japanese (ja)
Inventor
Mitsuhiro Kitamura
北村 光弘
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP60162574A priority Critical patent/JPS6223186A/en
Publication of JPS6223186A publication Critical patent/JPS6223186A/en
Pending legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01SDEVICES 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
    • H01S5/00Semiconductor lasers
    • H01S5/10Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers

Landscapes

  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Semiconductor Lasers (AREA)

Abstract

PURPOSE:To enable a stable single-axis oscillation near a Bragg wavelength by forming a phase shift region by filling the minute gap separating the first region from the second region with a non-conductive medium whose refractive index is larger than 1. CONSTITUTION:A diffraction grating 2 is formed, for example, on an N-InP substrate 1 and further on that, an N-In0.72Ga0.23As0.61P0.39 guide layer 3, an In0.59Ga0.41As0.90P0.10 active layer 4, and a P-Inp clad layer 5 are laminated in that order, followed by mesa etching and buried growth to fabricate DFB-BH LD. The element is mounted on a metal piece 6 of Cu using Au and while fixing it, a knife egde is put on the other end to cleave that and a force is apllied slightly against the metal piece 6 to form a gap 7 of a few mum. Polyimide 8 thinnered by thinner is poured in that gap 7 and the entire unit is baked in dry nitrogen for curing. Consequently, the gap having the medium whose refractive index is larger than 1 can be obtained.

Description

【発明の詳細な説明】 (産業上の利用分野) 本発明は分布帰還型半導体レーザに関する。[Detailed description of the invention] (Industrial application field) The present invention relates to a distributed feedback semiconductor laser.

(従来技術とその問題点) 高速変調時にも安定な単一軸モード発振を示し光フアイ
バ通信の伝送帯域を大きくとることのできる半導体光源
として分布帰還型半導体レーザ(DFB−LD)o開発
が進められている。DAB−LDは適当なピッチの回析
格子による波長選択機構を有しており、Gb/ sレベ
ルの高速iテffi調しても単一波長で発振するという
結果が得られている。
(Prior art and its problems) Distributed feedback semiconductor lasers (DFB-LDs) have been developed as semiconductor light sources that exhibit stable single-axis mode oscillation even during high-speed modulation and can widen the transmission band of optical fiber communications. ing. The DAB-LD has a wavelength selection mechanism using a diffraction grating with an appropriate pitch, and results have been obtained in which it oscillates at a single wavelength even during high-speed I-Teffi tuning at the Gb/s level.

ところで通常のDFB−LDにおいては端面反射がない
場合にはブラッグ波長をはさんだ2つの軸モードに対す
るしきい値利得が等しくなるから、基本的には2軸モ一
ド発損することが知られている。少なくとも一方の出力
端面が反射端面となっている場合にはブラッグ波長をは
さんだ発振波長としきい値利得との関係が非対称になっ
てきて、1本の軸モードで発振することになる。その場
合にも片側の端面反射率がOのとき、反射端間における
回析格子位相がπ/l T ’ ”/の場合2つの軸モ
ードに対するしきい値利得が等しくなる。このような位
相に近い状態でも、やはり両者のしきい値利得差は小さ
くなるので2軸モ一ド発振しゃすく、注入電流を増加し
て光出力を増してゆくとそれら2つの軸モード間でモー
ドのとびが生じたりする。しかも回析格子周期は240
0λ程度でありへきかいによって形成する反射端面にお
いて上述の回析格子位相を制御することは不可能といえ
る。
By the way, in a normal DFB-LD, when there is no end face reflection, the threshold gain for the two axial modes sandwiching the Bragg wavelength is equal, so it is known that basically the two axial modes generate a loss. There is. When at least one output end face is a reflective end face, the relationship between the oscillation wavelength sandwiching the Bragg wavelength and the threshold gain becomes asymmetrical, resulting in oscillation in one axial mode. In that case, when the end face reflectance on one side is O, the threshold gains for the two axial modes will be equal if the diffraction grating phase between the reflecting ends is π/l T '''/. Even in similar states, the difference in threshold gain between the two becomes small, resulting in biaxial mode oscillation, and as the injected current is increased to increase the optical output, a mode jump occurs between the two axial modes. Moreover, the diffraction grating period is 240.
It can be said that it is impossible to control the above-mentioned diffraction grating phase at the reflective end face formed by the cleavage.

そこで、本発明の目的は、上述の観点にたって、安定に
単一軸モード発振が得られ、特性の向上した分布帰還型
半導体レーザを提供することにある。
SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a distributed feedback semiconductor laser that can stably obtain single-axis mode oscillation and has improved characteristics.

(問題点を解決するための手段) 前述の問題点を解決するために本発明が提供する手段は
、活性層と、この活性層よりエネルギーギャップが大き
く、かつ一方の面に回析格子が形成された光ガイド層と
を半導体基板上に積層してなる分布帰還型半導体レーザ
でおって、前記活性層がレーザ共振軸方向に第1及び第
2の領域に分割してあり、これら第1及び第2の領域は
微小な間隙で隔てており、この間隙は屈折率が1より大
きな非導電媒質で埋めてあり位相シフト領域を形成して
いることを特徴とする。
(Means for Solving the Problems) The means provided by the present invention to solve the above-mentioned problems include an active layer having a larger energy gap than the active layer, and a diffraction grating formed on one surface. The active layer is divided into a first region and a second region in the direction of the laser resonance axis, and the active layer is divided into a first region and a second region in the direction of the laser resonance axis. The second region is separated by a minute gap, and this gap is filled with a non-conductive medium having a refractive index greater than 1 to form a phase shift region.

(発明の作用*原理) 従来の分布帰還型半導体レーザ(DFB−LD)に対し
、本発明においては素子を2分割し、その中間領域に位
相をずらす領域を形成した。それによって適当な位相ず
れ量に対して、ブラッグ波長においても単一軸モード発
振させることが可能となり、そのしきい値利得も通常の
場合と比べて大幅に下げることができる。
(Operation*Principle of the Invention) In contrast to the conventional distributed feedback semiconductor laser (DFB-LD), in the present invention, the element is divided into two parts, and a region for shifting the phase is formed in the middle region. This makes it possible to cause single-axis mode oscillation even at the Bragg wavelength for an appropriate amount of phase shift, and the threshold gain can also be significantly lowered compared to the normal case.

通常のDFB−LDICおいては、ブラッグ波長におい
て、光波の位相は一往復でπだけずれるから互いに打ち
消しあう。すなわちブラッグ波長では発損し得ないわけ
で、これが所謂ストップバンドとなる。そこで前述のよ
うにレーザ共振軸方向にそって部分的に等側屈折率の異
なる部分を形成することによって光波の位相をπだけず
らしてやれば、ブラッグ波長において一往復で2(πず
−れることになり、したがってブラッグ波長発振しうる
。このときには同時に、しきい値利得も低減する。
In a normal DFB-LDIC, the phases of light waves shift by π in one round trip at the Bragg wavelength, so they cancel each other out. In other words, there can be no emission loss at the Bragg wavelength, and this becomes the so-called stop band. Therefore, as mentioned above, if the phase of the light wave is shifted by π by forming parts with different equilateral refractive indexes along the laser resonance axis direction, the phase of the light wave can be shifted by 2 (π) in one round trip at the Bragg wavelength. Therefore, Bragg wavelength oscillation can occur.At this time, the threshold gain is also reduced at the same time.

ところで位相をずらす方法としては部分的に活性層おる
いはガイド層の厚さを変えて等側屈折率を部分的に変え
る方法などが考えられているが、本発明においては活性
層を第1及び第2の領域に2分割し、両領域の間隙で位
相をずらすものであれても位相シフトの効果が現われ、
素子特性の歩留り向上につながる。
By the way, as a method for shifting the phase, a method has been considered in which the thickness of the active layer or the guide layer is partially changed to partially change the isolateral refractive index, but in the present invention, the active layer is Even if it is divided into two regions and the phase is shifted in the gap between both regions, the effect of phase shift will appear,
This leads to improved yield of device characteristics.

活性層を2分割してわずかなすき間を形成することはさ
itど困瘤なことではなく、例えばW 、T。
It is not difficult to divide the active layer into two to form a slight gap, for example, W and T.

Tsangらが報告しているC1eaved −Cou
pled −Cavity (C’) v−ザ(App
l 、 Phys 、 Lett 、。
C1eaved-Cou reported by Tsang et al.
pled -Cavity (C') v-the (App
l, Phys, Lett,.

土2.(8)、P2S5,1983)  の手法を用い
、Cu等の金属片に一方の面を固定したまま他方の面か
らメスの刃をあててへきかりし、金属片をわずかに曲げ
ることによって容易VC2分割できる。
Soil 2. (8), P2S5, 1983), fix one side of a metal piece such as Cu, apply a scalpel blade from the other side to make a cut, and bend the metal piece slightly to easily create VC2. Can be divided.

あるいはイオンエツチング等の技術を用いてもよい。Alternatively, techniques such as ion etching may be used.

ところが、そのようにして形成される数μm程度のすき
間を空間のままにしておくと、DFB−LDの特性が、
非常にすき間の大きさに敏感罠なってしまい、2軸モ一
ド発振するなど、かえって素子歩留りが低下することが
認められた。これに対し、屈折率のやや大きなポリイミ
ドのような有機材料でそのすき間を埋めたところ、すき
間部分での光の反射が低減し、所望の位相シフトの効果
が確認嘔れた。
However, if the gap of several μm formed in this way is left open, the characteristics of the DFB-LD will change.
It was found that the device became extremely sensitive to the size of the gap, resulting in biaxial mode oscillation, which actually lowered the device yield. In contrast, when the gap was filled with an organic material such as polyimide with a slightly higher refractive index, the reflection of light at the gap was reduced, confirming the desired phase shift effect.

(実施例1) 以下実施例を示す図面を用いて本発明をより詳細に説明
する。
(Example 1) The present invention will be described in more detail below using drawings showing examples.

第1図は本発明による第1の実施例を示す。まずn−I
nP 基板1上に周期0.24μmの回析格子2を形成
する。その上に発光波長1.3μmに相当するn−In
6.yz Gao、ta As(、、Hpo−ssガイ
ド層3、発光波長1,55μmに相自する工nO,Il
l oao、41 AS67゜p o、t o  活性
層4.p−Inp  クラット層5を順次積層する。そ
の後通常の工程をへて、メサエッチング、埋め込み成長
を行なうことによりDFB−BHLDを作製した。素子
を前述0ようにcuの金属片6上にAuでマウントし、
固定したまま他方の面にメスの刃をあててへきかいし、
金属片6にわずかに力を加えることによって数μmのす
きま7を形成できる。そのす急ま7にシンナーで薄めた
ポリイミド8を流し込み、乾燥窒素中でベーキングする
ことくより、固化させることができる。その後P側の電
極をワイヤボンディングし、所望のDFB−LDを得た
。素子全体り長さは300μm程度とした。用いたポリ
イミドは屈折率が1.8程度のものである。
FIG. 1 shows a first embodiment according to the invention. First, n-I
A diffraction grating 2 with a period of 0.24 μm is formed on an nP substrate 1. On top of that, n-In corresponding to an emission wavelength of 1.3 μm is added.
6. yz Gao, ta As(,, Hpo-ss guide layer 3, technology compatible with the emission wavelength of 1.55 μm)
l oao, 41 AS67°p o, to active layer 4. P-Inp crat layers 5 are sequentially laminated. Thereafter, a DFB-BHLD was fabricated by performing mesa etching and buried growth through normal steps. Mount the device with Au on the Cu metal piece 6 as described above,
While keeping it fixed, apply a scalpel blade to the other side and cut it.
By applying a slight force to the metal piece 6, a gap 7 of several μm can be formed. The polyimide 8 diluted with thinner is poured into the rush 7 and can be solidified by baking in dry nitrogen. Thereafter, the P-side electrode was wire-bonded to obtain a desired DFB-LD. The overall length of the element was approximately 300 μm. The polyimide used has a refractive index of about 1.8.

この上51Cして作製し九D F B−L Dにおいて
、室温CW動作時の発振しきい値電流20mA、  片
面からの微分量子効率25−1単一軸モ一ド動作出力5
0mW、最高CW温度110℃程度の素子が再現性よく
得られた。
In the 9D F B-LD manufactured by 51C on this, the oscillation threshold current at room temperature CW operation is 20 mA, the differential quantum efficiency from one side is 25-1, the single axis mode operation output is 5
A device with a power of 0 mW and a maximum CW temperature of about 110° C. was obtained with good reproducibility.

さらにこのような位相シフト領域を有するDFB−LD
においては、反射端面における回析格子2の位相の影響
も小さい。通常のDFB−LDにおいては反射端面にお
ける位相条件によってモードとびを生ずる素子が少なく
なかった。−例として1枚のクエファから任意に切り出
して特性歩留りを調べたところ、通常のDFB−LDで
は35慢の素子が10mW以内の出力レベルで軸モード
のとび、あるいは2〜3本のモードが同時に発振するよ
5な状態を示したが、本実施例に示し九〇FB−LDに
おいてはその割合が10%に減少し、単一軸モード発振
の歩留りが大幅に向上した。
Furthermore, a DFB-LD having such a phase shift region
In this case, the influence of the phase of the diffraction grating 2 on the reflective end face is also small. In ordinary DFB-LDs, there are many elements in which mode skipping occurs due to phase conditions at the reflective end face. - As an example, when we cut out arbitrary pieces from one Quefer and investigated the characteristic yield, we found that in a normal DFB-LD, the axial mode jumps at an output level of less than 10 mW, or 2 to 3 modes simultaneously. However, in the 90FB-LD shown in this example, the ratio decreased to 10%, and the yield of single-axis mode oscillation was significantly improved.

(実施例2) 第1図に示した実施例ではCレーザのように素子そのも
のを2分割してすきま7を形成したが、リアクティブイ
オンエツチング等の技術を用いてすきま7を形成しても
よい。第2図は本発明による第2の実施例の模式的な断
面図である。第1図の場合と同様にしてDFBウェファ
を作製し、活性層4をつ糎ぬける深さまでイオンエツチ
ングを行なってすきま7を形成した。このようにして作
製したDFB−LDも第1の実施例の場合とほぼ同等の
特性を示し、特性の歩留りもきわめて高かった。
(Example 2) In the example shown in FIG. 1, the gap 7 was formed by dividing the element itself into two like a C laser, but the gap 7 could also be formed using a technique such as reactive ion etching. good. FIG. 2 is a schematic cross-sectional view of a second embodiment of the invention. A DFB wafer was prepared in the same manner as in the case of FIG. 1, and ion etching was performed to a depth that penetrated the active layer 4 to form the gap 7. The DFB-LD produced in this way also exhibited characteristics almost equivalent to those of the first example, and the yield of characteristics was also extremely high.

なお本発明の実施例においてはInP を基板、それに
格子整合したInGaAsPを活性層およびガイド層と
したが、用いる半導体材料はもちろんこれに限るもので
はなく、GaAJAs / GaAs系、InGaAs
 / InAlAs系等、他の半導体材料を用いて何ら
差しつかえないヶもちろんPW基板、あるいは半導絶縁
性の半導体基板を用いて何ら差しつかえない。さらに2
分割された領域にそれぞれ独立の電極を形成してやれば
波長制御型のDFB−LDとしても用いることができる
In the embodiments of the present invention, InP was used as the substrate, and InGaAsP lattice-matched to it was used as the active layer and the guide layer, but the semiconductor materials used are of course not limited to these, and may include GaAJAs/GaAs, InGaAs, etc.
/ There is no problem in using other semiconductor materials such as InAlAs type, but there is also no problem in using a PW substrate or a semiconducting insulating semiconductor substrate. 2 more
By forming independent electrodes in each of the divided regions, it can also be used as a wavelength control type DFB-LD.

(発明の効果) 本発明0%徴は分布帰還型半導体レーザにおいて、屈折
率が1よりも大きな媒質を有するすきまを形成し、位相
シフト領域としたことでちる。これによって、ブラクグ
波長付近で安定に単一軸モード発振されることが可能と
なり、発振しきい値電流が低減され、レーザ特性・素子
の特性歩留りが大幅に向上し九〇FB−LDを得ること
ができた。
(Effects of the Invention) The 0% characteristic of the present invention is achieved by forming a gap containing a medium with a refractive index greater than 1 to form a phase shift region in a distributed feedback semiconductor laser. This makes it possible to stably oscillate in a single-axis mode near the Brag wavelength, reduce the oscillation threshold current, and significantly improve the laser characteristics and device characteristic yield, making it possible to obtain a 90FB-LD. did it.

【図面の簡単な説明】[Brief explanation of drawings]

第1図及び第2図は本発明の第1及び第2の実施例をそ
れぞれ示す模式的な断面図でおる。 1・・・n−InP基板、2・・・回析格子、3・・・
ガイド層、4・・・活性層、5・・・p−1nP クラ
ッド層、6・・・金属片、7・・・すきま、8・・・ポ
リイミド。
FIGS. 1 and 2 are schematic cross-sectional views showing a first and second embodiment of the present invention, respectively. 1... n-InP substrate, 2... diffraction grating, 3...
Guide layer, 4... Active layer, 5... P-1nP cladding layer, 6... Metal piece, 7... Gap, 8... Polyimide.

Claims (1)

【特許請求の範囲】[Claims] 活性層と、この活性層よりエネルギーギャップが大きく
、かつ一方の面に回析格子が形成された光ガイド層とを
半導体基板上に積層してなる分布帰還型半導体レーザに
おいて、前記活性層がレーザ共振軸方向に第1及び第2
の領域に分割してあり、これら第1及び第2の領域は微
小な間隙で隔ててあり、この間隙は屈折率が1より大き
な非導電媒質で埋めてあり位相シフト領域を形成してい
ることを特徴とする分布帰還型半導体レーザ。
In a distributed feedback semiconductor laser in which an active layer and an optical guide layer having a larger energy gap than the active layer and having a diffraction grating formed on one surface are laminated on a semiconductor substrate, the active layer is first and second in the direction of the resonance axis
The first and second regions are separated by a minute gap, and this gap is filled with a non-conductive medium with a refractive index greater than 1 to form a phase shift region. Distributed feedback semiconductor laser featuring:
JP60162574A 1985-07-23 1985-07-23 Distributed feedback type semiconductor laser Pending JPS6223186A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP60162574A JPS6223186A (en) 1985-07-23 1985-07-23 Distributed feedback type semiconductor laser

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP60162574A JPS6223186A (en) 1985-07-23 1985-07-23 Distributed feedback type semiconductor laser

Publications (1)

Publication Number Publication Date
JPS6223186A true JPS6223186A (en) 1987-01-31

Family

ID=15757172

Family Applications (1)

Application Number Title Priority Date Filing Date
JP60162574A Pending JPS6223186A (en) 1985-07-23 1985-07-23 Distributed feedback type semiconductor laser

Country Status (1)

Country Link
JP (1) JPS6223186A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1191651A1 (en) * 2000-09-06 2002-03-27 Nec Corporation Distributed feedback semiconductor laser
WO2024105764A1 (en) * 2022-11-15 2024-05-23 日本電信電話株式会社 Optical device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1191651A1 (en) * 2000-09-06 2002-03-27 Nec Corporation Distributed feedback semiconductor laser
WO2024105764A1 (en) * 2022-11-15 2024-05-23 日本電信電話株式会社 Optical device

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