JPS62124792A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a longitudinal single-mode laser, which can be modulated at high speed, by growing multiple quantum well structure on one main surface of a semiconductor substrate through a buffer layer, applying an electric field between the multiple quantum well structure and the semiconductor substrate and controlling the stoppage and starting of oscillation. CONSTITUTION:An n-InP buffer layer 2, an MQW layer 2, an n-InP buffer 4 and a diffraction grating 4-1 are formed onto a (100)n-InP substrate 1, and an n-InGaAsP waveguide layer 5, an n-InGaAsP active layer 6 and a p-In clad layer 7 are grown on the diffraction grating 4-1. A light-emitting section is processed to a mesa shape, p-InP 8, n-InP 9 and a current block layer are grown, and p-InGaAsP 10 is grown continuously. Sections up to the n-InP buffer layer 4 is removed selectively adjoined to the light-emitting section and a p-type electrode 11 and n-type electrodes 12, 13 are formed, and one of a light-emitting outgoing section for an element is shaped in an inclined end surface 13 in order to remove a Fabry-Perot mode. When a section between the electrodes 11, 12 is conducted, the device is oscillated at a longitudinal single mode at an oscillation wavelength of approximately 1.3mum.

Description

【発明の詳細な説明】 産業上の利用分野 本発明は、光通信等に使用される高速変調可能なレーザ
光源にかかる。DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laser light source capable of high-speed modulation used in optical communications and the like.

従来の技術 従来より、光通信用半導体レーザ、特に波長１．３μｍ
、及び１．５μｍ帯のＩｎＧａＡＢＰ／ＩｎＰ系のレー
ザは、その発振しきい電流の低減、安定な横モード動作
等が実現され日本国内にも４００Ｍｂｉｔ／ｓの幹線網
が付設されるに至った。今後さらにギガピット帯の伝送
容量の通信を行うためには、モーダルノイズの影響をな
くすために高速変調時には縦単一モードで発振する分布
帰還型レーザ（ＤＦＢレーザと略す）が必要である。特
に１．６μｍ帯の光通信においてはシリカ系ファイバの
分散により伝送帯域が制御を受けるためＤＦＢレーザで
あることが必要不可決である。このレーザの変調におい
ては、いわゆる直接変調がとられるが、高速変調のため
には活性層のキャリアの再結合時間を短くする９発光パ
ワーを上げる。ゲインを高くする等の手段がとられるが
変調周波数の上限は、３〜４ＧＨ２程度である。Conventional technology Conventionally, semiconductor lasers for optical communication, especially at a wavelength of 1.3 μm, have been used.
, and 1.5 μm band InGaABP/InP lasers have achieved reduced oscillation threshold current, stable transverse mode operation, etc., and a 400 Mbit/s trunk network has been installed in Japan. In order to carry out communication with transmission capacity in the gigapit band in the future, a distributed feedback laser (abbreviated as a DFB laser) that oscillates in a single longitudinal mode during high-speed modulation will be required to eliminate the influence of modal noise. In particular, in optical communication in the 1.6 μm band, the transmission band is controlled by the dispersion of the silica fiber, so a DFB laser is not necessary. In the modulation of this laser, so-called direct modulation is used, but for high-speed modulation, the emission power is increased to shorten the recombination time of carriers in the active layer. Although measures such as increasing the gain are taken, the upper limit of the modulation frequency is about 3 to 4 GH2.

発明が解決しようとする問題点 より大容量の光通信を実現するために、ＤＦＢレーザに
直接変調とは別の方法で高速変調を可能にすることを目
的とする。Problems to be Solved by the Invention In order to realize large-capacity optical communication, it is an object of the present invention to enable high-speed modulation of a DFB laser by a method other than direct modulation.

問題点を解決するための手段 高速変調を可能にするために本発明においては、発振状
態における注入電流は一定としておき、ＤＦＢレーザの
回折格子と活性層との結合に電界によってロスを与える
ことにより発振の開始、停止を行うことを可能とする機
構をとりつけた。このために回折格子直下に、半導体多
層膜をとりつけ多重量子井戸構造（ＭＱＷと略す）とし
、このＭＱＷ層と、基板との間に独立に電界を加えるこ
とのできる電極をとりつけだ。Means for Solving the Problems In order to enable high-speed modulation, in the present invention, the injection current in the oscillation state is kept constant, and a loss is given by an electric field to the coupling between the diffraction grating and the active layer of the DFB laser. We have installed a mechanism that allows us to start and stop oscillation. For this purpose, a semiconductor multilayer film is attached directly below the diffraction grating to create a multiple quantum well structure (abbreviated as MQW), and an electrode that can independently apply an electric field between this MQW layer and the substrate is attached.

作　　用 この電極に電界を加えると、ＭＱＷ層の透過率が変化し
同時に、回折格子と活性層での発光との結合にロスが生
じ発振は停止する。この動作においては、キャリアの移
動が伴わないため極めて高速動作が可能となる。Operation When an electric field is applied to this electrode, the transmittance of the MQW layer changes, and at the same time, a loss occurs in the coupling between the diffraction grating and the light emitted from the active layer, and oscillation stops. In this operation, extremely high-speed operation is possible because there is no movement of carriers.

実施例 〈実施例１〉 第１図に本発明のＤＦＢレーザの一実施例の斜視図を示
す。（１００）ｎ−ＩｎＰ基板１上に、気相成長法によ
ってｎ−ＩｎＰバッファ層２および高抵抗のｎ−−Ｉｎ
Ｐ、ｎ−−ＩｎＧａＡｓＰ（Ｅｇ＝０．９５ｅＶ）が交
互にそれぞれ２００人、６０人の厚さで、４０層成長さ
せたＭＱＷ層３．ｎ−ＩｎＰバッフ　７４゜該バッファ
層４には周期が約１９７ＯＡの回折格子４−１が形成さ
れている。回折格子４−１上にはｎ−ＩｎＧａＡｓＰ導
波層（約１５００人、　Ｅｇ−０，９３ｅＶ）６．ｎ−
ＩｎＧａＡｓＰ　（Ｅｇ＝０．９５）活性層６゜ｐ−Ｉ
ｎクラッド層７を成長させる。次に発光部分をメサ状に
加工後、ｐ−ＩｎＰ　８．ｎ−ＩｎＰ　９．電流ブロッ
ク層を成長後さらにｐ−１ｎＧａＡｇＰ　１０を連続し
て成長させる。次にｎ−ＩｎＰバッファ層４まで発光部
に隣接して選択的にとりのぞきｐ型電極１１及びｎ型電
極１２．１３をとりつける。Embodiment Embodiment 1 FIG. 1 shows a perspective view of an embodiment of the DFB laser of the present invention. (100) On the n-InP substrate 1, an n-InP buffer layer 2 and a high-resistance n--In
3. MQW layers of 40 layers of P, n--InGaAsP (Eg = 0.95 eV) grown alternately with a thickness of 200 and 60, respectively. n-InP buffer 74° A diffraction grating 4-1 with a period of about 197 OA is formed in the buffer layer 4. On the diffraction grating 4-1 is an n-InGaAsP waveguide layer (approximately 1500 layers, Eg-0,93eV)6. n-
InGaAsP (Eg=0.95) active layer 6°p-I
An n-cladding layer 7 is grown. Next, after processing the light emitting part into a mesa shape, p-InP 8. n-InP 9. After growing the current blocking layer, p-1nGaAgP 10 is successively grown. Next, the n-InP buffer layer 4 adjacent to the light emitting part is selectively removed and a p-type electrode 11 and an n-type electrode 12, 13 are attached.

素子の発光出射部の一方はファブリペローモードを除去
するために、傾斜端面１３とした。第２図に活性層中心
付近のへき開断面を示す。ＭＱＷ層３上のｎ−ＩｎＰバ
ッファ層４上に作られた回折格子の波の中心付近からＭ
ＱＷ層３の最上層までの厚さは、本実施例においては約
９３０人である。One of the light emission parts of the device was formed into an inclined end face 13 in order to eliminate Fabry-Perot mode. FIG. 2 shows a cleavage cross section near the center of the active layer. M
The thickness of the QW layer 3 up to the top layer is about 930 in this example.

第１図の素子をｐサイドアップでヒートシンクにマウン
トし、電極１１．１２間に通電すると、約１．３μｍの
発振波長で縦単一モードで発振する。When the device shown in FIG. 1 is mounted on a heat sink with the p side up and current is applied between the electrodes 11 and 12, it oscillates in a single longitudinal mode with an oscillation wavelength of about 1.3 μm.

次に、ｎ型電極１２．１３間に電界を加えてゆくと発振
は停止する。高速変調実験を行うと通常の直接変調に較
べ明らかに良好な結果が得られた。Next, when an electric field is applied between the n-type electrodes 12 and 13, the oscillation stops. When conducting high-speed modulation experiments, clearly better results were obtained compared to conventional direct modulation.

〈実施例２〉 第１図と同様の構造において第３図に示すようにＭＯＷ
層３上に、ＩｎＰバッファ層４として約９３０人、ｎ−
ＩｎＧａＡｓＰ活性層６及び　ｎ−ＩｎＧａＡｓＰ導波
層６を順次成長後回折格子４−１を形成ししかるのちｐ
−ＩｎＰクラッド層７を成長させた構造とした。なお、
第３図において第１図と共通する部分には共通の番号を
付している。<Example 2> In the same structure as in Fig. 1, as shown in Fig. 3, MOW
On layer 3, approximately 930 layers, n-
After sequentially growing the InGaAsP active layer 6 and the n-InGaAsP waveguide layer 6, the diffraction grating 4-1 is formed.
- A structure in which an InP cladding layer 7 was grown was adopted. In addition,
In FIG. 3, parts common to those in FIG. 1 are designated by common numbers.

このような素子を実施例１と同様にマウントし、電極１
１．１２間に通電すると同じく縦単一モードで発振する
。次にこの状態で電極１２．１３間に電界を加えてゆく
と発振は停止した。高速変調実験では実施例１と同様従
来の直接変調にくらべ良好な特性が得られた。Such a device was mounted in the same manner as in Example 1, and electrode 1
When the current is applied between 1.12 and 12, it oscillates in a single longitudinal mode. Next, when an electric field was applied between the electrodes 12 and 13 in this state, the oscillation stopped. In the high-speed modulation experiment, as in Example 1, better characteristics were obtained than in the conventional direct modulation.

発明の効果 以上述べたように本発明によれば極めて高速変調可能な
縦単−モードレーサを提供しうる。Effects of the Invention As described above, according to the present invention, it is possible to provide a longitudinal single-mode laser capable of extremely high-speed modulation.

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

第１図は本発明の一実施例のレーザの斜視図、第２図は
同レーザの発光部の拡大図、第３図は本発明の異なる実
施例の発光部拡大図である。 １−−ｎ−ＩｎＰ基板、礼　４．　９−−−−−・ｒｘ
−ＩｎＰ。 ３・・・・・・ＭＱＷ層、　　了、８・・・・・・ｐ−
ＩｎＰ、５・・・・・・ｎ−ＩｎＧａＡｓＰ導波層、６
−−−−・・ｎ−ＩｎＧａＡｓＰ活性層、１ｏ・・・・
・・ｐ−ＩｎＧａＡｓＰキャップ層、４−１・・・・・
・回折格子、１１・・・・・・ｐ型電極、１２．１３・
・・・・・ｎ型電極。FIG. 1 is a perspective view of a laser according to an embodiment of the present invention, FIG. 2 is an enlarged view of a light emitting section of the same laser, and FIG. 3 is an enlarged view of a light emitting section of a different embodiment of the present invention. 1--n-InP substrate, courtesy 4. 9-----・rx
-InP. 3...MQW layer, 8...p-
InP, 5... n-InGaAsP waveguide layer, 6
-----... n-InGaAsP active layer, 1o...
...p-InGaAsP cap layer, 4-1...
・Diffraction grating, 11...p-type electrode, 12.13.
...N-type electrode.

Claims (1)

【特許請求の範囲】[Claims] 半導体基板の一主面に、バッファ層を介して多重量子井
戸構造を成長させ、前記多重量子井戸構造と前記半導体
基板との間に電界を加える手段を有し、前記電界印加手
段によって発振の停止、開始を制御させることを特徴と
する半導体レーザ。A multiple quantum well structure is grown on one principal surface of a semiconductor substrate via a buffer layer, and means for applying an electric field between the multiple quantum well structure and the semiconductor substrate is provided, and the oscillation is stopped by the electric field applying means. , a semiconductor laser characterized in that its starting is controlled.