JPS623220A - Optical modulator - Google Patents
Optical modulatorInfo
- Publication number
- JPS623220A JPS623220A JP14172785A JP14172785A JPS623220A JP S623220 A JPS623220 A JP S623220A JP 14172785 A JP14172785 A JP 14172785A JP 14172785 A JP14172785 A JP 14172785A JP S623220 A JPS623220 A JP S623220A
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- Japan
- Prior art keywords
- layer
- voltage
- semiconductor
- quantum well
- gaas
- Prior art date
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Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は低駆動電圧で高い消光化が得られ、吸収端の短
波長化、長波長化の両方を行なうことのできる高速変調
可能な光変調器に関するものである。Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to high-speed modulation of light that can achieve high quenching with low driving voltage and that can both shorten and lengthen the wavelength of the absorption edge. It concerns a modulator.
（従来技術とその問題点）
光通信等において、光源として用いられる半導体レーザ
の出力強度や位相を高速で変化させる際には、大きく分
類して２種の方法がある。それは、半導体レーザを駆動
する電流を直接変化させる方法と、光源からの光出力も
受動素子である光変調器を通す事によって変調する方法
である。この両者にはそれぞれ長所短所がある。前者は
光変調器を使用しないため、光変調器による挿入損失は
ないが、数百メガヘルツ以上の高速変調時には、半導体
レーザ中のキャリヤの緩和振動による変調波形の歪みや
、発振波長の時間変化（チャーピング）が生じ、信号光
の検出が困難になる。また、この変調速度はキャリヤ寿
命により制限され、毎秒約４ギガビツト以上の直接変調
は原理的に困難である。(Prior Art and its Problems) When changing the output intensity or phase of a semiconductor laser used as a light source at high speed in optical communication or the like, there are broadly two types of methods. There are two methods: one is to directly change the current that drives the semiconductor laser, and the other is to modulate the optical output from the light source by passing it through an optical modulator, which is a passive element. Both have their own advantages and disadvantages. The former does not use an optical modulator, so there is no insertion loss caused by the optical modulator, but during high-speed modulation of several hundred megahertz or higher, distortion of the modulation waveform due to relaxation oscillation of carriers in the semiconductor laser and time change in the oscillation wavelength ( Chirping) occurs, making it difficult to detect the signal light. Further, this modulation speed is limited by the carrier lifetime, and direct modulation of more than about 4 gigabits per second is difficult in principle.
一方後者は、毎秒１０ギガビット程度の高速変調が可能
で、かつ高速変調時においてもチャーピングは少ないが
、通常の光変調器では挿入損失が大きく、特に長距離の
伝送に対しては不利である。On the other hand, the latter is capable of high-speed modulation of about 10 gigabits per second and has little chirping even during high-speed modulation, but ordinary optical modulators have large insertion loss, which is particularly disadvantageous for long-distance transmission. .
また、高い消光比の変調を得るためには高い電圧で駆動
する必要がある。Furthermore, in order to obtain modulation with a high extinction ratio, it is necessary to drive at a high voltage.
そこで、後者のタイプで、低損失で高速変調可能な多層
薄膜半導体による光変調器が提案されている。その−例
は、山西氏らにより、ジャパニーズ、ジャーナル・オブ
・アプライド・フィジックス（Ｊａｐａｎｅｓｅ Ｊｏ
ｕｎａｌ ｏｆ Ａｐｐｌｉｅｄ Ｐｈｙｓｉｃｓ）誌
１９８３年２２巻Ｌ２２に掲載されているように、多層
薄膜半導体に電界を印加する事により、吸収端を長波長
側にずらす、というものであるが、これは、同時に電子
と正孔も空間的に分離してしまい、吸収確率は小さくな
るという欠点を有する。しかも、電界の印加方向を変化
させても吸収端の短波長化は原理的に困難で、高い消光
比の変調を得るための駆動電圧も実用上はまだ高めであ
る。Therefore, an optical modulator of the latter type using a multilayer thin film semiconductor has been proposed, which is capable of high-speed modulation with low loss. An example is the Japanese Journal of Applied Physics by Yamanishi et al.
As published in Vol. 22, L22, of Applied Physics), 1983, applying an electric field to a multilayer thin film semiconductor shifts the absorption edge to the longer wavelength side, but this also means that electrons This has the disadvantage that the holes and holes are also spatially separated, and the probability of absorption is small. Moreover, even if the direction of electric field application is changed, it is difficult in principle to shorten the wavelength of the absorption edge, and the driving voltage required to obtain high extinction ratio modulation is still high in practice.
（問題点を解決するための手段）
本発明による光変調器は、１層ないし多層の、膜厚が電
子の平均自由行程程度以下である半導体層
′膜を有し、該半導体薄膜に積層方向に電界を印加する
手段を有する光変調器において、該半導体膜中の狭禁制
帯幅を有する半導体層の禁制帯幅が積層方向に関して単
調に変化してなることに特徴がある。(Means for Solving the Problems) The optical modulator according to the present invention has one or more semiconductor layers having a film thickness equal to or less than the mean free path of electrons.
'In an optical modulator having a film and means for applying an electric field to the semiconductor thin film in the stacking direction, the forbidden band width of the semiconductor layer having a narrow forbidden band width in the semiconductor film changes monotonically with respect to the stacking direction. It is characterized by the fact that it becomes
また、上記半導体薄膜が積層方向に関してｐ型半導体層
とｎ型半導体層にはさまれた領域にあり、該半導体薄膜
中の狭禁制帯幅を有する半導体層の禁制帯幅が、積層方
向に関してｐ型半導体層に近づくほど狭くなるよう変化
しているとさらによい効果が得られる光変調器となる。Further, the semiconductor thin film is located in a region sandwiched between a p-type semiconductor layer and an n-type semiconductor layer in the stacking direction, and the semiconductor layer in the semiconductor thin film has a narrow bandgap width of p in the stacking direction. If the width becomes narrower as it approaches the type semiconductor layer, an optical modulator with even better effects will be obtained.
（発明の作用・原理）
以下、図面を用いて本発明の作用・原理を説明する。ま
ず、本発明による光変調器の、１層ないし多層の半導体
薄膜構造のバンド構造を模式的に、電界が印加されて′
ν）ない場合について第１図（ａ）に、積層方向に電界
が印加されている場合について第１図（ｂ）に示す。こ
の図では薄膜構造が量子井戸層１層から成っている例を
示した。量子井戸層とバリア層を交互に多数積層した薄
膜構造でも原理は同じである。この多層の積層構造から
成る薄膜構造は光の閉じ込めの点では１層のものより有
利である。ここでは話をわかりやすくするため１層の場
合で原理を説明する。ここで、横軸は積層方向すなわち
２方向の位置とし、縦軸はバンド構造のエネルギーであ
る。エネルギーは量子井戸の中間点でのバンド端の値を
基準に考え、電子に対しては、第１図の上向きの方向も
正に、正孔に対しては下向きを正に考える。そして、量
子井戸層の中間点を２軸の原点と考える。矩形の量子井
戸ポテンシャルを、積層方向に印加した電界によりバン
ド端が斜めになるように変形させた場合、電子、正孔等
キャリヤの存在できるエネルギー準位は、電界を印加し
ていない場合の矩形の量子井戸ポテンシャルの中でのエ
ネルギー準位と比べ、低減されることが理論的に示され
ている（バスタート、他、フイジカルレビｚ−Ｂ（Ｐｈ
ｙｓ、Ｒｅｖ、Ｂ）２８巻１９８３年３２４１ページ）
。特に、量子井戸層が１００人程度量上ある場合のエネ
ルギー準位の低下量は量子井戸のポテンシャル深さにほ
とんど依存せず、次式で近似的にあられすことができる
。(Operation/Principle of the Invention) The operation/principle of the present invention will be explained below with reference to the drawings. First, the band structure of the one-layer or multi-layer semiconductor thin film structure of the optical modulator according to the present invention is schematically shown.
FIG. 1(a) shows the case where there is no ν), and FIG. 1(b) shows the case where an electric field is applied in the stacking direction. This figure shows an example in which the thin film structure consists of one quantum well layer. The principle is the same for a thin film structure in which a large number of quantum well layers and barrier layers are alternately laminated. This multi-layered thin film structure is more advantageous than a single layer structure in terms of light confinement. Here, in order to make the discussion easier to understand, the principle will be explained in the case of one layer. Here, the horizontal axis is the stacking direction, that is, the position in two directions, and the vertical axis is the energy of the band structure. The energy is considered based on the value of the band edge at the midpoint of the quantum well, and for electrons, the upward direction in FIG. 1 is also considered positive, and for holes, the downward direction is considered positive. The midpoint of the quantum well layer is considered to be the origin of the two axes. When a rectangular quantum well potential is deformed so that the band edge is oblique by an electric field applied in the stacking direction, the energy level at which carriers such as electrons and holes can exist is the same as that of the rectangle when no electric field is applied. It has been theoretically shown that the energy level in the quantum well potential of
ys, Rev, B) Volume 28, 1983, Page 3241)
. In particular, when there are about 100 quantum well layers, the amount of decrease in the energy level hardly depends on the potential depth of the quantum well, and can be approximately expressed by the following equation.
ここで、ｍ＊はキャリヤの有効質量、ｅは電子の
喝電荷の絶対値、Ｆは量子井戸内での電界による空
間的エネルギー変化を表わすパラメータ、Ｌｚは量子井
戸の幅、ｈはブランクの定数を２ｎで除したものであ゛
る。また、Ｃは１０−３程度の大きさの正の定数である
。この式は、量子井戸内のハミルトニアンＨが、矩形の
量子井戸におけるハミルトニアンをＨｏとして、
Ｈ＝Ｈｏ＋１ｅＩＦ・ｚ （
２）となる場合のエネルギー準位変化量を変分法により
計算したものである。
・□・さて、第１図（ａ）のような本発明によ
る量子井戸構造においては、ハミルトニアンは
・。Here, m* is the effective mass of the carrier, and e is the effective mass of the electron.
The absolute value of the charge, F is a parameter representing the spatial energy change due to the electric field within the quantum well, Lz is the width of the quantum well, and h is the blank constant divided by 2n. Further, C is a positive constant of approximately 10-3. This formula shows that the Hamiltonian H in the quantum well is H=Ho+1eIF・z (
2) The amount of energy level change in case 2) is calculated using the variational method.
・□・Now, in the quantum well structure according to the present invention as shown in Figure 1(a), the Hamiltonian is
・.
Ｈ＝Ｈｏ＋−・Ｚ （正孔に対して）（４）と考える
ことができる。ここで、Ｆｄｌ、 Ｆｖ１２はそれぞれ
伝導帯下端、価電子帯上端のエネルギーの量子井戸内で
の変化量を表わす。（３）式、および（４）式は、それ
ぞれＦｃ／ＬｚとＦｖ／Ｌｚをｌ ｅ ｌ・Ｆと書き直
せば（２）式と同一なことがわかる。したがって、本発
明による量子井戸構造における、矩形の量子井戸でのエ
ネルギー準位からの変化量は、電子に対して正孔に対し
である。ここで、ｍｅ”、 ｍｈ”は電子、正孔の有効
質量である。It can be considered that H=Ho+-.Z (for holes) (4). Here, Fdl and Fv12 represent the amount of change in the energy at the lower end of the conduction band and the upper end of the valence band, respectively, within the quantum well. It can be seen that equations (3) and (4) are the same as equation (2) by rewriting Fc/Lz and Fv/Lz as le l·F, respectively. Therefore, in the quantum well structure according to the present invention, the amount of change from the energy level in a rectangular quantum well is the same for holes as for electrons. Here, me'' and mh'' are effective masses of electrons and holes.
以上により、まず矩形の量子井戸ポテンシャルにおける
電子のエネルギー準位を８８、正孔のエネルギー準位も
εｈとすれば、第１図（ａ）の構造における電子および
正孔のエネルギー準位ε、’ １３．εｈ′１４は、と
なる。From the above, first, if the energy level of the electron in the rectangular quantum well potential is 88 and the energy level of the hole is also εh, then the energy level of the electron and hole in the structure of FIG. 1(a) is ε,' 13. εh'14 becomes.
次に、電界印加１２により第１図（ａ）のバンド構造が
第１図（ｂ）のように変化した際のキャリヤのエネルギ
ー準位について考える。ここで、電界印加による量子井
戸ポテンシャルの変化は第１図（ｂ）中のＸというエネ
ルギー準位巻で特性づけることができる。Next, consider the energy level of carriers when the band structure in FIG. 1(a) changes as shown in FIG. 1(b) by applying an electric field 12. Here, the change in the quantum well potential due to the application of an electric field can be characterized by the energy level winding X in FIG. 1(b).
このＸは、量子井戸内での伝導帯下端のエネルギー最小
部の電界印加によるエネルギー上昇量を表わす。印加電
界の大きさをＥとするとＸはｅ−Ｅ−Ｌｚ（ｅｖ）とし
て表わすことができる。This X represents the amount of increase in energy due to the application of an electric field at the minimum energy portion at the bottom of the conduction band within the quantum well. If the magnitude of the applied electric field is E, then X can be expressed as e-E-Lz(ev).
したがって、この場合のハミルトアンは、（３）式、（
４）式から
Ｈ＝ Ｈａ ＋ −・ｚ （正孔に対して）
（１０）Ｌｚ
と与えられる。よって、第１図（ａ）の場合の考察より
、ただちに電子正孔のエネルギー準位ε。１６゜εｈ″
１７は
と与えられる。Therefore, the Hamiltonian in this case is expressed by equation (3), (
4) From the formula, H= Ha + −・z (for holes)
(10) Given as Lz. Therefore, from the consideration of the case in FIG. 1(a), the energy level ε of the electron hole is immediately determined. 16゜εh″
17 is given as.
さて、上記での考察結果をもとして、電界印加による本
発明による量子井戸構造の吸収端の変化量を考える。電
界印加がない際の吸収端８ｇ′、電界印加時の吸収端ｅ
ｇ″は、それぞれ
ｃ、’ ＝ｅ、’ へ’ ＋ｅ、’ （但し、弓は、も
との禁制帯り （１３）ｅ−＝″、” ＋ｅｈ
＋％ （
１４）であるので、この変化量δε＝εｇ″−εｇ′ハ
、δε＝ｅ’−ｔ、′ ＝（εＩ 十〇ｈ′ ）−（ε
） ＋εｈ′ ）となる。Now, based on the results of the above discussion, the amount of change in the absorption edge of the quantum well structure according to the present invention due to application of an electric field will be considered. Absorption edge 8g' when no electric field is applied, absorption edge e when electric field is applied
g'' becomes c, ' = e, ' + e, ' (however, the bow is the original forbidden belt (13) e-='', " +eh
+% (
14), the amount of change δε=εg″−εg′c, δε=e′−t,′ =(εI 10h′)−(ε
) +εh′).
通常の光変調器に用いられる（ＡＩＧａ）Ａｓや（Ｉｎ
Ｇａ）（ＡｓＰ）等の半導体においてはｍｅ”とｍｈ”
の比は１：１０程度、また、ＦｃとＦｖの比は、伝導帯
と価電子帯のヘテロ界面でのバンド不連続量に等しく２
：１から１：２程度であるので、（１５）式中の（ｍｈ
”・Ｆｖ −ｍｅ＊−Ｆｃ）の値は通常圧となる。(AIGa)As and (In) used in ordinary optical modulators
In semiconductors such as Ga) (AsP), me” and mh”
The ratio of Fc to Fv is about 1:10, and the ratio of Fc to Fv is 2, which is equal to the amount of band discontinuity at the hetero interface between the conduction band and the valence band.
:1 to 1:2, so (mh
”・Fv −me*−Fc) is the normal pressure.
ここで、第２図に電界印加による量子井戸ポテンシャル
の変形量Ｘと吸収端の変化量δεの関係を本発明による
場合を実線で、従来の矩形量子井戸での場合（Ｆｃ ＝
Ｆｖ ＝ ０に対応する）を破線で示す。Here, in FIG. 2, the relationship between the amount of deformation X of the quantum well potential due to the application of an electric field and the amount of change δε of the absorption edge is shown by the solid line in the case of the present invention, and in the case of the conventional rectangular quantum well (Fc =
(corresponding to Fv = 0) is indicated by a dashed line.
第２図を用いて実際に電圧を積層方向に印加し、量子井
戸層に電界を印加する際の吸収端の変化量について考え
る。電界がＯの時はＸがＯに対応する。Using FIG. 2, consider the amount of change in the absorption edge when a voltage is actually applied in the stacking direction and an electric field is applied to the quantum well layer. When the electric field is O, X corresponds to O.
本発明では電界が０の状態から、量子井戸内の伝導帯下
端のエネルギー最小値が上昇する方向（以下正方向とよ
ぶ）に電界を印加すると吸収端は長波長化し、負方向に
印加すると短波長化する。しがち、この場合では、従来
と同じだけの電界を印加しＸの値を同じだけ変化させて
も吸収端の変化量は非常に大きくとれる。そして電子と
正孔の各波動関数は、第１図（ｂ）よりもわかるように
、量子井戸内で伝導帯下端または価電子帯上端が水平に
なる程度に大きな電界を印加しない限りは、反対方向の
ヘテ口界面に局在することはなく、重列積分値の変化は
小さい。そのため、吸収端を変化させても吸収係数の低
下率は小さい。In the present invention, when an electric field is applied in the direction in which the minimum energy value at the lower end of the conduction band in the quantum well increases (hereinafter referred to as the positive direction) from a state where the electric field is 0, the absorption edge becomes longer in wavelength, and when applied in the negative direction, the absorption edge becomes shorter in wavelength. Convert into wavelength. In this case, even if the same electric field as in the conventional case is applied and the value of X is changed by the same amount, the amount of change in the absorption edge can be very large. As can be seen from Figure 1(b), the wave functions of electrons and holes are opposite unless a large electric field is applied to the quantum well so that the lower end of the conduction band or the upper end of the valence band becomes horizontal. It is not localized at the hete-opening interface in the direction, and the change in the multiline integral value is small. Therefore, even if the absorption edge is changed, the rate of decrease in the absorption coefficient is small.
さらに、この量子井戸層をｐ型クラッド層とｎ型クラッ
ド層の間に位置させ、しかも禁制帯幅の狭くなっている
方にｐ型クラッド層がある場合では、ｐ−ｎ接合による
いわゆるビルトイン・ポテンシャルにより、外部からの
電界を印加しない場合でも第２図のＸが正の場合に対応
する内部電界が印加されていることになる。この場合で
外部から電界を印加すると、印加電界に対応する吸収端
の変化量はさらに大きくとれることがわかる。Furthermore, if this quantum well layer is located between a p-type cladding layer and an n-type cladding layer, and the p-type cladding layer is located on the side where the forbidden band width is narrower, the so-called built-in Due to the potential, even when no external electric field is applied, an internal electric field corresponding to the case where X in FIG. 2 is positive is applied. It can be seen that if an electric field is applied from the outside in this case, the amount of change in the absorption edge corresponding to the applied electric field can be further increased.
（実施例）
第３図に本発明第１の実施例の光変調器の斜視図を示す
。これは、分子線エピタキシー（ＭＢＥ）法により製作
したものである。これは、まずＳｉドープｎ型ＧａＡｓ
基板３１上に厚さ１．０１１ｍのＳｉドープｎ型ＧａＡ
ｓバッファ一層３２、厚さ２．０ｐｍのＳｉドープｎ型
Ａｌｏ。(Embodiment) FIG. 3 shows a perspective view of an optical modulator according to a first embodiment of the present invention. This was manufactured using the molecular beam epitaxy (MBE) method. First, Si-doped n-type GaAs
Si-doped n-type GaA with a thickness of 1.011 m is placed on the substrate 31.
s-buffer layer 32, 2.0 pm thick Si-doped n-type Alo.
４Ｇａｏ、ｓＡｓクラッド層３３を積層し、次にＡ１組
成比、Ｘを０から０．１５まで連続的に変化させた厚さ
１００人のノンドープＡｌｘＧａ１−ＡＳ量子井戸層３
４と厚さ８０人のノンドープＡｌｏ４Ｇａｏ、ｓＡｓバ
リヤ層３５を交互に３００周期積し、その上に厚さ２．
０ｐｍのＢｅドープｐ型Ａｌｏ、４Ｇａｏ。A 4Gao, sAs cladding layer 33 is laminated, and then a non-doped AlxGa1-AS quantum well layer 3 with a thickness of 100 layers with the A1 composition ratio and X continuously varied from 0 to 0.15.
300 cycles of non-doped Alo4Gao, sAs barrier layers 35 with a thickness of 2.4 and 80 layers are stacked alternately, and a layer 35 with a thickness of 2.
0pm Be-doped p-type Alo, 4Gao.
６ＡＳクラッド層３６、厚さ０．５ｐｍのＢｅドープｐ
型ＧａＡｓコンタクト層３７を成長して多層構造を製作
した。次にこれを５Ｘ５ｍｍ程度の大きさにし、上面、
および下面のＧａＡｓ層を選択エツチングにより円形に
除去し、それ以外のＧａＡｓ層上に電極３８を製作した
ものである。6AS cladding layer 36, 0.5 pm thick Be-doped p
A type GaAs contact layer 37 was grown to produce a multilayer structure. Next, make this into a size of about 5 x 5 mm, and
The GaAs layer on the lower surface was removed in a circular shape by selective etching, and an electrode 38 was fabricated on the remaining GaAs layer.
この円形のＧａＡｓ層を除去した部分に、垂直方向に光
を入射し、電圧を上記電極間に印加して透過光スペクト
ルの電圧依存性を調べた。Light was perpendicularly incident on the circular portion where the GaAs layer was removed, and a voltage was applied between the electrodes to examine the voltage dependence of the transmitted light spectrum.
本実施例においては、ビルトイン・ポテンシャルにより
、第２図におけるＸ軸の原点がやや左側に移動する状態
に対応しているが、電圧を正方向、つまりｎ側の電極を
接地し、ｐ側の電極に負の電圧を印加した際には吸収端
は長波長化し、逆方向の電圧印加時には短波長化した。In this example, the built-in potential corresponds to the state in which the origin of the X axis in FIG. When a negative voltage was applied to the electrode, the wavelength of the absorption edge became longer, and when a voltage was applied in the opposite direction, the wavelength became shorter.
＋２ｖから一２Ｖまでの電圧を印加した際の吸収端の変
化量は、−６ｍｅＶから＋３ｍｅＶであり、吸収端近傍
の吸収率はほとんど変動しなかった。そして、変調特性
も良好であった。The amount of change in the absorption edge when a voltage from +2V to -2V was applied was from -6meV to +3meV, and the absorption rate near the absorption edge hardly changed. Moreover, the modulation characteristics were also good.
次に、本発明第２の実施例について説明する。第４図に
、本実施例の多層薄膜構造のバンドの模式図を示す。こ
の素子構造は、第１の実施例とほとんど同じであるが但
し量子井戸層を、Ａｔ組成比Ｘが０゜１５から０になる
ように製作し、ｐ型ＧａＡｓ層の方向に量子井戸層の禁
制帯幅が狭くなるようにした。そして、垂直方向に光を
入射して、吸収端の電圧依存性を調べた。ｎ側電極を接
地し、ｐ側電極に一２Ｖから＋２Ｖまで電圧を印加した
所、吸収端は、−１０ｍｅＶから＋７ｍｅＶまで変化し
、同一電圧でも第１の実施例以上の吸収端の変化が得ら
れた。そして、吸収端近傍の吸収率も、第１の実施例と
同様、電圧印加による変動は少なく、しかも良好な変調
特性も得られた。実際に、＋２Ｖの電圧印加時の吸収端
は、本実施例では約８０５ｎｍ、Ｏｖでは約８１０ｎｍ
、−２Ｖでは約８１４ｎｍであり波長８１２ｎｍの光の
吸収率をそれぞれの場合について測定した所、３％、３
０％、９７％となり、＋２Ｖから一２ｖの電圧変化によ
って得られる消光比は１５ｄＢと非常に良好な値であっ
た。Next, a second embodiment of the present invention will be described. FIG. 4 shows a schematic diagram of the band of the multilayer thin film structure of this example. The device structure is almost the same as that of the first embodiment, except that the quantum well layer is fabricated so that the At composition ratio The forbidden band width has been made narrower. Then, the voltage dependence of the absorption edge was investigated by entering light in the vertical direction. When the n-side electrode was grounded and a voltage from -2V to +2V was applied to the p-side electrode, the absorption edge changed from -10meV to +7meV, and even with the same voltage, the absorption edge changed more than in the first example. It was done. Similarly to the first example, the absorption coefficient near the absorption edge showed little variation due to voltage application, and good modulation characteristics were also obtained. In fact, the absorption edge when a voltage of +2V is applied is about 805 nm in this example, and about 810 nm in Ov.
, -2V is about 814 nm, and when the absorption rate of light with a wavelength of 812 nm was measured in each case, it was 3%, 3
0% and 97%, and the extinction ratio obtained by changing the voltage from +2V to -2V was a very good value of 15 dB.
次に、本発明第３の実施例について説明する。第５図に
本実施例の斜視図を示す。これは気相成長法によりＳド
ープｎ型ＩｎＰ基板５１上に厚さ２．０ｐｍのＳドープ
ｎ型ＩｎＰバッファ一層５２を積層し、次にＡｓ組成比
Ｘを０．５０から０．６０まで連続的に変化させた厚さ
１２０人のノンドープＩｎｏ、７５Ｇａｏ、２５Ａｓｘ
Ｐ１−ｘ量子井戸層５３と厚さ６０人のノンドープＩｎ
Ｐバリヤ層５４を交互に６周期積層し、その上に厚さ２
．５ｐｍのＺｎドープｐ型ＩｎＰクラッド層５５、厚さ
０．５ｐｍのＺｎｎドープ型ＩｎＧａＡｓＰコンタクト
層５６を積層した基板を製作した。次に、基板の両面に
電極５７を製作し、そして基板上面にＣＶＤ法によりＳ
ｉＯ２膜を付着させた後、通常のフォトリソグラフィー
法により、１．５１１ｍ幅のストラ 。Next, a third embodiment of the present invention will be described. FIG. 5 shows a perspective view of this embodiment. This is done by laminating a single layer 52 of S-doped n-type InP buffer with a thickness of 2.0 pm on an S-doped n-type InP substrate 51 using a vapor phase growth method, and then continuously increasing the As composition ratio X from 0.50 to 0.60. Non-doped Ino, 75Gao, 25Asx with different thicknesses of 120 people
P1-x quantum well layer 53 and non-doped In with a thickness of 60
Six periods of P barrier layers 54 are laminated alternately, and a layer with a thickness of 2
．． A substrate was manufactured in which a 5 pm thick Zn-doped p-type InP cladding layer 55 and a 0.5 pm thick Znn-doped InGaAsP contact layer 56 were laminated. Next, electrodes 57 are fabricated on both sides of the substrate, and S
After depositing the iO2 film, a 1.511 m wide strip was formed using conventional photolithography methods.
イブ状に５ｉ０２を残して他のＳｉＯ２を除去し、しか
る後、ＳｉＯ２の付着していない部分をｎ型ＩｎＰバッ
ファ一層５２までエツチングにより除去してから残って
いたＳｉＯ２を取りさって導波路構造を形成し
、゛たものである。The remaining SiO2 was removed leaving 5i02 in the form of a strip, and then the portion to which SiO2 was not attached was removed by etching down to the n-type InP buffer layer 52, and the remaining SiO2 was removed to form a waveguide structure. form
, it was.
この導波路構造に光を入射し、導波された光の透過スペ
クトルの、印加電圧依存性を測定したところ、印加電圧
が＋ＩＶ、 ＯＶ、 −ＩＶの際の吸収端はそれぞれ１
２９５ｎｍ、 １３０５ｎｍ、 １３１４ｎｍであった
。そして導波路長を２００ｐｍとし、波長１３００ｎｍ
のレーザ光を入射し、上記電圧を変調して印加したとこ
ろ、＋ＩＶ印加時はもとのレーザ光強度の約１％、−１
Ｖでは７０％の光が取り出された。この際の消光比は約
１８ｄＢと非常に優れたものであった。そして、この印
加電圧の変調により光の強度変調を行なったところ、変
調可能であった最高周波数は約３ＧＨｚであり、しかも
これは電極間の寄生容量により決定されたものであって
、素子構造によるものではなかった。When light was incident on this waveguide structure and the dependence of the transmission spectrum of the guided light on the applied voltage was measured, the absorption edges were 1 when the applied voltage was +IV, OV, and -IV, respectively.
They were 295 nm, 1305 nm, and 1314 nm. The waveguide length is 200pm, and the wavelength is 1300nm.
When the above voltage was modulated and applied to a laser beam of
At V, 70% of the light was extracted. The extinction ratio at this time was approximately 18 dB, which was very excellent. When the intensity of light was modulated by modulating this applied voltage, the highest frequency that could be modulated was approximately 3 GHz, and this was determined by the parasitic capacitance between the electrodes, and was determined by the element structure. It wasn't something.
以上ここでは３つの実施例について述べたが、本発明は
量子井戸層の禁制帯幅が積層方向に関して単調に変化し
てなる、好ましくはｐ型半導体層の方向に狭くなるよう
変化してなることが本質であり、量子井戸での禁制帯幅
の変化のしかた、材料系、半導体成長方法等に何ら限定
されないことは明らかである。そして上記禁制帯幅の変
化の仕方も空間的に直線でなく第６図（ａ）のように湾
曲していても、第６図（ｂ）のようにステップ状に変化
していても本質的な効果は同様である。Although three embodiments have been described above, the present invention is such that the forbidden band width of the quantum well layer changes monotonically in the stacking direction, preferably changes to become narrower in the direction of the p-type semiconductor layer. It is clear that this is the essence, and is not limited to the method of changing the forbidden band width in the quantum well, the material system, the semiconductor growth method, etc. The manner in which the forbidden band width changes is not a straight line spatially, but curved as shown in Figure 6(a), or in a stepwise manner as shown in Figure 6(b). The effect is the same.
（発明の効果）
本発明による光変調器は、低電圧で高い消光比を得るこ
とができ、電圧印加方向の変化により吸収端の短波長化
、長波長化の両方が行なえ、しかも高速変調が可能であ
るという特徴を有する。(Effects of the Invention) The optical modulator according to the present invention can obtain a high extinction ratio with a low voltage, can both shorten and lengthen the wavelength of the absorption edge by changing the direction of voltage application, and can perform high-speed modulation. It has the characteristic that it is possible.
第１図（ａ）、 （ｂ）は本発明の詳細な説明するため
のバンド構造を示す模式図である。第２図は量子井戸ポ
テンシャルの変形量Ｘと吸収端の変化量δεの関係を示
す図である。第３図は第１の実施例の斜視図である。第
４図は第２の実施例の多層薄膜構造のバンド構造を示す
模式図である。第５図は第３実施例の斜視図である。第
６図（ａ）、 （ｂ）は量子井戸層内のバンド構造の変
形例を示す模式図である。
図において
１１・・・量子井戸での伝導帯下端のポテンシャルエネ
ルギー変化量
１２・・・量子井戸での価電子帯上端のポテンシャルエ
ネルギー変化量
１３・・・電子のエネルギー準位
１４・・・正孔のエネルギー準位
１５・・・量子井戸ポテンシャルの変形を特徴づけるエ
ネルギー値
１６・・・電界印加時の電子のエネルギー準位１７・・
・電界印加時の正孔のエネルギー準位３１−ｎ型ＧａＡ
ｓ基板 ３２・ｎ型ＧａＡｓバッファ一層３３−ｎ型
Ａｌｏ、＋Ｇａｏ、ｅＡｓクラッド層３４−・・ノンド
ープＡｌｘＧａｘ−ｘＡｓ（０≦Ｘ≦０．１５）量子井
戸層
３５−・・ノンドープＡｌｏ、＋Ｇａｏ、ｅＡｓバリヤ
層３６・ｐ型Ａｊｏ、４Ｇａｏ、ｓＡｓクラッド層３７
・・・ｐ型ＧａＡｓコンタクト層
３８・・・電極 ５１・・・ｎ型ＩｎＰ基板５２
・・・ｎ型ＩｎＰバッファ一層
５３・・・ノン ドーフゴｎｏ、７ｓＧａｏ、２５Ａｓ
ｘＰｔ−ｘ（０，５０≦Ｘ≦０゜６０）量子井戸層
５４・・・ノンドープＩｎＰバリヤ層
５５・・・ｐ型ＩｎＰクラッド層
５６・・・ｐ型ＩｎＧａＡｓＰコンタクト層 ５７・
・・電極である。
第１図
（ａ）
第２図
第６図
（ａ）
（ｂ）FIGS. 1(a) and 1(b) are schematic diagrams showing band structures for detailed explanation of the present invention. FIG. 2 is a diagram showing the relationship between the amount of deformation X of the quantum well potential and the amount of change δε of the absorption edge. FIG. 3 is a perspective view of the first embodiment. FIG. 4 is a schematic diagram showing the band structure of the multilayer thin film structure of the second embodiment. FIG. 5 is a perspective view of the third embodiment. FIGS. 6(a) and 6(b) are schematic diagrams showing modified examples of the band structure within the quantum well layer. In the figure, 11... Potential energy change at the bottom of the conduction band in the quantum well 12... Potential energy change at the top of the valence band in the quantum well 13... Electron energy level 14... Hole Energy level 15...Energy value characterizing the deformation of the quantum well potential 16...Energy level of electrons when an electric field is applied 17...
・Hole energy level 31-n-type GaA when electric field is applied
s substrate 32 - n-type GaAs buffer single layer 33 - n-type Alo, +Gao, eAs cladding layer 34 - non-doped AlxGax-xAs (0≦X≦0.15) quantum well layer 35 - non-doped Alo, +Gao, eAs Barrier layer 36/p-type Ajo, 4Gao, sAs cladding layer 37
... p-type GaAs contact layer 38 ... electrode 51 ... n-type InP substrate 52
...N-type InP buffer single layer 53...Non Dofugo no, 7sGao, 25As
xPt-x (0,50≦X≦0°60) quantum well layer 54...non-doped InP barrier layer 55...p-type InP cladding layer 56...p-type InGaAsP contact layer 57.
...It is an electrode. Figure 1 (a) Figure 2 Figure 6 (a) (b)
Claims (2)
を１層ないし多層具備した半導体膜構造と、該半導体薄
膜構造に積層方向に電界を印加する手段とを少なくとも
有し、さらに、該半導体薄膜構造を構成する半導体層の
うち禁制帯幅の小さい方の半導体層の禁制帯幅が積層方
向に関して単調に変化してなることを特徴とする光変調
器。(1) It has at least a semiconductor film structure including one or more semiconductor layers having a film thickness equal to or less than the mean free path of electrons, and means for applying an electric field to the semiconductor thin film structure in the stacking direction, and further comprises: An optical modulator characterized in that a forbidden band width of a semiconductor layer having a smaller forbidden band width among semiconductor layers constituting a semiconductor thin film structure changes monotonically in the stacking direction.
造を挟み、かつ、該半導体薄膜構造中の狭禁制帯幅を有
する半導体層の禁制帯幅が、積層方向に関してｐ型半導
体に近づくほど狭くなるよう変化してなることを特徴と
する特許請求の範囲第（１）項記載の光変調器。(2) The semiconductor thin film structure is sandwiched between a p-type semiconductor layer and an n-type semiconductor, and the forbidden band width of the semiconductor layer having a narrow forbidden band width in the semiconductor thin film structure approaches that of the p-type semiconductor in the stacking direction. The optical modulator according to claim 1, characterized in that the optical modulator is changed to become narrower as the width increases.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60141727A JPH0650366B2 (en) | 1985-06-28 | 1985-06-28 | Light modulator |
| US06/878,741 US4727341A (en) | 1985-06-28 | 1986-06-26 | Optical modulator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60141727A JPH0650366B2 (en) | 1985-06-28 | 1985-06-28 | Light modulator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS623220A true JPS623220A (en) | 1987-01-09 |
| JPH0650366B2 JPH0650366B2 (en) | 1994-06-29 |
Family
ID=15298802
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60141727A Expired - Lifetime JPH0650366B2 (en) | 1985-06-28 | 1985-06-28 | Light modulator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0650366B2 (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62191822A (en) * | 1986-02-18 | 1987-08-22 | Nippon Telegr & Teleph Corp <Ntt> | Quantum well type optical modulator and its production |
| JPS6435525A (en) * | 1987-07-31 | 1989-02-06 | Nippon Telegraph & Telephone | Quantum well type optical modulator |
| JPH01179125A (en) * | 1988-01-11 | 1989-07-17 | Nippon Telegr & Teleph Corp <Ntt> | Optical space modulating element |
| JPH01262523A (en) * | 1988-04-14 | 1989-10-19 | Fujitsu Ltd | Optical semiconductor element |
| JPH02239222A (en) * | 1989-01-26 | 1990-09-21 | Cselt Spa (Cent Stud E Lab Telecomun) | Electrooptical modulator having cantum well |
| US5101294A (en) * | 1990-03-30 | 1992-03-31 | The University Of Connecticut | Surface acoustic wave optical modulator |
| JPH08220496A (en) * | 1995-02-09 | 1996-08-30 | Nec Corp | Semiconductor optical modulation element |
| US6150667A (en) * | 1996-05-22 | 2000-11-21 | Nec Corporation | Semiconductor optical modulator |
| KR100500097B1 (en) * | 2002-03-01 | 2005-07-11 | 미쓰비시덴키 가부시키가이샤 | Optical modulator |
| WO2005096463A1 (en) * | 2004-03-30 | 2005-10-13 | Nec Corporation | Surface-emitting laser and its driving method |
| JP2006338017A (en) * | 2005-05-31 | 2006-12-14 | Avago Technologies General Ip (Singapore) Private Ltd | Semiconductor optical modulator having quantum well structure for increasing effective photocurrent generating capability |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60205421A (en) * | 1984-02-28 | 1985-10-17 | エクソン リサーチ アンド エンヂニアリング コムパニー | Superlattice electrooptic device |
-
1985
- 1985-06-28 JP JP60141727A patent/JPH0650366B2/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60205421A (en) * | 1984-02-28 | 1985-10-17 | エクソン リサーチ アンド エンヂニアリング コムパニー | Superlattice electrooptic device |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62191822A (en) * | 1986-02-18 | 1987-08-22 | Nippon Telegr & Teleph Corp <Ntt> | Quantum well type optical modulator and its production |
| JPS6435525A (en) * | 1987-07-31 | 1989-02-06 | Nippon Telegraph & Telephone | Quantum well type optical modulator |
| JPH01179125A (en) * | 1988-01-11 | 1989-07-17 | Nippon Telegr & Teleph Corp <Ntt> | Optical space modulating element |
| JPH01262523A (en) * | 1988-04-14 | 1989-10-19 | Fujitsu Ltd | Optical semiconductor element |
| JPH0529888B2 (en) * | 1989-01-26 | 1993-05-06 | Kuseruto Chentoro Suteyudei E Lab Terekomyunikatsuiooni Spa | |
| JPH02239222A (en) * | 1989-01-26 | 1990-09-21 | Cselt Spa (Cent Stud E Lab Telecomun) | Electrooptical modulator having cantum well |
| US5101294A (en) * | 1990-03-30 | 1992-03-31 | The University Of Connecticut | Surface acoustic wave optical modulator |
| JPH08220496A (en) * | 1995-02-09 | 1996-08-30 | Nec Corp | Semiconductor optical modulation element |
| US6150667A (en) * | 1996-05-22 | 2000-11-21 | Nec Corporation | Semiconductor optical modulator |
| KR100500097B1 (en) * | 2002-03-01 | 2005-07-11 | 미쓰비시덴키 가부시키가이샤 | Optical modulator |
| WO2005096463A1 (en) * | 2004-03-30 | 2005-10-13 | Nec Corporation | Surface-emitting laser and its driving method |
| JPWO2005096463A1 (en) * | 2004-03-30 | 2008-02-21 | 日本電気株式会社 | Surface emitting laser and driving method thereof |
| JP2006338017A (en) * | 2005-05-31 | 2006-12-14 | Avago Technologies General Ip (Singapore) Private Ltd | Semiconductor optical modulator having quantum well structure for increasing effective photocurrent generating capability |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0650366B2 (en) | 1994-06-29 |
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