JPH05173200A - Method and device for modulating light by using semiconductor element of quantum well structure - Google Patents
Method and device for modulating light by using semiconductor element of quantum well structureInfo
- Publication number
- JPH05173200A JPH05173200A JP3178654A JP17865491A JPH05173200A JP H05173200 A JPH05173200 A JP H05173200A JP 3178654 A JP3178654 A JP 3178654A JP 17865491 A JP17865491 A JP 17865491A JP H05173200 A JPH05173200 A JP H05173200A
- Authority
- JP
- Japan
- Prior art keywords
- quantum well
- light
- semiconductor element
- well structure
- probe light
- 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
Classifications
-
- 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
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements with at least one potential jump barrier, e.g. PN, PIN junction
- G02F1/017—Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells
- G02F1/01725—Non-rectangular quantum well structures, e.g. graded or stepped quantum wells
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements with at least one potential jump barrier, e.g. PN, PIN junction
- G02F1/017—Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells
- G02F1/01725—Non-rectangular quantum well structures, e.g. graded or stepped quantum wells
- G02F1/0175—Non-rectangular quantum well structures, e.g. graded or stepped quantum wells with a spatially varied well profile, e.g. graded or stepped quantum wells
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、量子井戸構造の半導体
素子を用いて、ピコ秒或はそれ以下の超高速度で光を変
調する方法及び装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for modulating light at a very high speed of picosecond or less using a semiconductor device having a quantum well structure.
【０００２】[0002]
【従来の技術】従来、光変調装置として、photorefract
ive （ＰＲ）効果を用いたものが提案されている。この
ＰＲ効果を、図５を用いて説明する。2. Description of the Related Art Conventionally, photorefract has been used as an optical modulator.
Those using the ive (PR) effect have been proposed. This PR effect will be described with reference to FIG.
【０００３】図５は、バルク電気光学結晶のエネルギー
バンドを示す図である。ここで、或る不純物準位４２に
ある電子４１を光学的に伝導帯に励起すると、この電子
４１は、伝導帯において拡散及びドリフトし、その後、
捕獲準位４３によって捕獲される。この電子の捕獲によ
って生じる空間電界は、電気光学効果（ポッケルス効
果）によって非線形屈折率変化を起こす。この様な現象
がＰＲ効果と呼ばれている。前記不純物準位４２は、通
常、浅い準位であるドナー準位やアクセプタ準位に対し
て、室温の熱エネルギー（２６ｍｅＶ）に比べ十分大き
なエネルギーギャップを持つ深い準位と呼ばれる。ま
た、捕獲準位４３は、通常、不純物準位４２のイオン化
準位から成る。FIG. 5 is a diagram showing an energy band of a bulk electro-optic crystal. Here, when an electron 41 in a certain impurity level 42 is optically excited to the conduction band, the electron 41 diffuses and drifts in the conduction band, and then,
It is captured by the capture level 43. The spatial electric field generated by the trapping of electrons causes a nonlinear refractive index change due to the electro-optic effect (Pockels effect). Such a phenomenon is called the PR effect. The impurity level 42 is generally called a deep level having a sufficiently large energy gap with respect to the thermal energy (26 meV) at room temperature with respect to the shallow donor level and acceptor level. Further, the trap level 43 is usually composed of an ionization level of the impurity level 42.
【０００４】このＰＲ効果は、数ｍＷ程度のレーザ光パ
ワーで大きな非線形屈折率変化が得られるという利点を
有するが、光励起キャリア（この例では電子）の移動及
び捕獲を用いる為に、その応答速度は高々数マイクロ秒
程度である。This PR effect has the advantage that a large nonlinear refractive index change can be obtained with a laser light power of about several mW, but since it uses the movement and capture of photoexcited carriers (electrons in this example), its response speed is high. Is at most a few microseconds.
【０００５】これを克服する為に、最近、バリア層をグ
レーディドギャップとした、即ちバンドギャップが層厚
方向に変化している構造にした半導体井戸構造がＲａｌ
ｐｈｅｔ．ａｌ．，Ｐｈｙｓｉｃａｌ Ｒｅｖｉｅｗ
Ｌｅｔｔｅｒｓ ｖｏｌ．６３，ｐｐ．２２７２−２２
７５（１９８９）において提案されている。図６（ａ）
〜（ｃ）にこれを示す。図６（ａ）に示す如く、バリア
層の価電子帯５１と伝導帯５２はグレーディドギャップ
構造になっており、これによりビルトイン（ｂｕｉｌｔ
−ｉｎ）電界が形成されている。ここにおいて、グレー
ディドギャップバリア層で光入射により生成される正孔
５３と電子５４は、上記ビルトイン電界によりドリフト
して夫々価電子帯と伝導帯での量子井戸５５、５６で捕
獲される。この時、電子５４と正孔５３のドリフト速度
の違いにより、図６（ｂ）のように電子５４の方が早く
上記量子井戸５６に捕獲される。この為、図６（ｃ）の
ように正孔５３が量子井戸５５に捕獲されるまでの間、
電子５４と正孔５３との間で過渡的に空間電界が生じ
る。これがバリア層での電気光学効果を介して屈折率の
変化を誘起するのである。In order to overcome this, recently, a semiconductor well structure having a graded gap as a barrier layer, that is, a structure in which the band gap changes in the layer thickness direction, is Ral.
phet. al. , Physical Review
Letters vol. 63, pp. 2272-22
75 (1989). Figure 6 (a)
This is shown in (c). As shown in FIG. 6A, the valence band 51 and the conduction band 52 of the barrier layer have a graded gap structure, which allows a built-in structure.
-In) An electric field is created. Here, the holes 53 and the electrons 54 generated by light incidence in the graded gap barrier layer drift by the built-in electric field and are captured by the quantum wells 55 and 56 in the valence band and the conduction band, respectively. At this time, due to the difference in drift velocity between the electron 54 and the hole 53, the electron 54 is captured earlier in the quantum well 56 as shown in FIG. 6B. Therefore, until the holes 53 are captured by the quantum well 55 as shown in FIG.
A spatial electric field is transiently generated between the electron 54 and the hole 53. This induces a change in the refractive index via the electro-optic effect in the barrier layer.
【０００６】電子５４と正孔５３が量子井戸５６、５５
に捕獲された後では、両者間に空間的な分離がないので
上記過渡的な空間電界は消滅する。こうした過渡的な過
程のＰＲ効果の応答速度は、電子５４が量子井戸５６に
捕獲されるまでのドリフト時間で概ね決まる為に、立ち
上がりの応答速度としてピコ秒程度が実験的に得られて
いる。Electrons 54 and holes 53 are quantum wells 56 and 55.
After being captured by, the transient spatial electric field disappears because there is no spatial separation between the two. Since the response speed of the PR effect in such a transient process is substantially determined by the drift time until the electrons 54 are captured by the quantum well 56, a picosecond rise response speed has been experimentally obtained.
【０００７】また、立ち下がり時間は正孔５３の量子井
戸５５での捕獲に要する時間で概ね決まり、量子井戸５
６、５５中での電子５４−正孔５３間の再結合時間に制
限されない。なぜなら、量子井戸５６、５５内に捕獲さ
れた電子５４と正孔５３との間には空間的な分離がない
ので空間電界は生じず、上記ＰＲ効果に寄与しないから
である。従って、立ち下がり時間もピコ秒から１０ピコ
秒オーダーが期待できる。しかし、実際には、バリア層
での不純物トラップに起因するＰＲ効果のナノ秒オーダ
ーの立ち下がり時間の裾引きが生じるという問題があっ
た。The fall time is generally determined by the time required to capture the holes 53 in the quantum well 55.
It is not limited to the recombination time between the electron 54 and the hole 53 in 6, 55. This is because there is no spatial separation between the electrons 54 and the holes 53 trapped in the quantum wells 56 and 55, so that a spatial electric field does not occur and does not contribute to the PR effect. Therefore, the fall time can be expected to be in the order of picoseconds to 10 picoseconds. However, in reality, there is a problem that the fall time of the PR effect due to the impurity trap in the barrier layer is tailed on the nanosecond order.
【０００８】以上の様に、ＰＲ効果を用いた純光学的な
光波の変調では、量子井戸構造を用いたキャリアの実励
起によるものでも、光励起されたキャリアの走行時間及
び不純物準位での捕獲により、立ち上がり及び立ち下が
りの応答速度が制限されるという欠点があった。As described above, in the pure optical light wave modulation using the PR effect, even when the carriers are actually excited by using the quantum well structure, the photoexcited carriers are trapped in the transit time and the impurity level. Due to this, there is a drawback that the response speed of rising and falling is limited.
【０００９】[0009]
【発明が解決しようとする課題】よって、本発明の目的
は、上記従来技術の問題点を解決し、ピコ秒或はそれ以
下の超高速度で光を変調することができる光変調方法及
び装置を提供することにある。SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an optical modulation method and apparatus capable of modulating light at an ultrahigh speed of picosecond or less. To provide.
【００１０】[0010]
【課題を解決する為の手段】本発明の上記目的を達成す
る光変調装置は以下を有することを特徴とする：量子井
戸構造を備えた半導体素子；半導体素子の量子井戸構造
に電界を印加する手段；半導体素子に偏光したプローブ
光を入射する手段、該プローブ光は、量子井戸構造にお
ける電気光学効果によって、その偏光状態が変化して半
導体素子から出射される；半導体素子に、その量子井戸
構造に仮想電荷励起を生じさせるポンプ光を入射する手
段、ここで、仮想電荷励起よって、量子井戸構造に印加
された電界がスクリーニングされる；及び半導体素子か
ら出射した光の偏光状態の変化を強度変化に変換する偏
光子。An optical modulator for achieving the above object of the present invention is characterized by having: a semiconductor element having a quantum well structure; an electric field applied to the quantum well structure of the semiconductor element. Means; means for injecting polarized probe light into the semiconductor element; the probe light is emitted from the semiconductor element with its polarization state changed by the electro-optic effect in the quantum well structure; Means for injecting pumping light that causes virtual charge excitation into, where the electric field applied to the quantum well structure is screened by the virtual charge excitation; and the change in polarization state of the light emitted from the semiconductor device is changed in intensity. Polarizer to convert to.
【００１１】また、上記の装置を用いて、光を変調する
方法は以下のステップを有することを特徴とする：半導
体素子の量子井戸構造に電界を印加する；半導体素子に
偏光したプローブ光を入射する、該プローブ光は、量子
井戸構造における電気光学効果によって、その偏光状態
が変化して半導体素子から出射される；半導体素子に、
その量子井戸構造に仮想電荷励起を生じさせるポンプ光
を入射する、ここで、仮想電荷励起によって、量子井戸
構造に印加された電界がスクリーニングされる；及び半
導体素子から出射した光の偏光状態の変化を偏光子によ
って強度変化に変換する。A method of modulating light using the above device is characterized by the following steps: applying an electric field to the quantum well structure of the semiconductor device; and injecting polarized probe light into the semiconductor device. The polarization state of the probe light is changed by the electro-optic effect in the quantum well structure and emitted from the semiconductor element;
Pump light that causes virtual charge excitation is incident on the quantum well structure, where the electric field applied to the quantum well structure is screened by the virtual charge excitation; and change in polarization state of light emitted from the semiconductor device. Is converted into intensity change by a polarizer.
【００１２】また、本発明の一実施態様の光変調装置は
以下を有する： （ａ）以下のものから成る半導体素子、基板；基板上に
形成された第１の導電型を有する第１の半導体層；第１
の半導体層上に形成された多重量子井戸層；多重量子井
戸層上に形成された第２の導電型を有する第２の半導体
層；及び第１及び第２の半導体層に各々電気的にコンタ
クトされた一対の電極； （ｂ）半導体素子に逆バイアスの電界を印加する、前記
電極に接続された電圧源； （ｃ）半導体素子に偏光したプローブ光を入射する手
段、該プローブ光は、多重量子井戸層における電気光学
効果によって、その偏光状態が変化して半導体素子から
出射される； （ｄ）半導体素子に、その多重量子井戸層に仮想電荷励
起を生じさせるポンプ光を入射する手段、ここで、仮想
電荷励起によって、量子井戸構造に印加された電界がス
クリーニングされる；及び （ｅ）半導体素子から出射した光の偏光状態の変化を強
度変化に変換する偏光子。An optical modulator according to one embodiment of the present invention has the following: (a) a semiconductor element comprising the following: a substrate; a first semiconductor having a first conductivity type formed on the substrate. Layer; 1st
Multiple quantum well layer formed on the semiconductor layer; second semiconductor layer having a second conductivity type formed on the multiple quantum well layer; and electrically contacting the first and second semiconductor layers, respectively. Paired electrodes; (b) a voltage source connected to the electrodes for applying a reverse bias electric field to the semiconductor element; (c) means for injecting polarized probe light into the semiconductor element; The polarization state is changed by the electro-optic effect in the quantum well layer and emitted from the semiconductor element; (d) means for injecting pump light that causes virtual charge excitation in the multiple quantum well layer into the semiconductor element, here. Then, the electric field applied to the quantum well structure is screened by the virtual charge excitation; and (e) a polarizer that converts a change in the polarization state of light emitted from the semiconductor element into an intensity change.
【００１３】[0013]
【作用】即ち、本発明の装置は、量子井戸構造でのキャ
リアの仮想励起（光照射される間のみ励起が起こるも
の）による過渡的な空間電界生成を用いて電気光学効果
を介して量子井戸構造の光学的屈折率異方性を励起し、
この光学的屈折率異方性により量子井戸構造を伝搬する
光の偏光状態を変化させるものである。この様に本発明
の装置は、仮想励起された電子・正孔対の波動関数が半
導体量子井戸構造部に印加された静電界の為に非対称に
なって、仮想電荷分極が過渡的に生じる現象を利用する
ので、応答速度の立ち上がり、立ち下がり共に仮想的な
キャリア励起過程に関わり、例えばサブピコ秒程度の高
速変調が可能となる。That is, the device of the present invention uses the transient spatial electric field generation by virtual excitation of carriers in the quantum well structure (excitation occurs only during light irradiation), and the quantum well is mediated through the electro-optic effect. Excites the optical anisotropy of the structure,
This optical refractive index anisotropy changes the polarization state of light propagating through the quantum well structure. As described above, in the device of the present invention, a phenomenon in which the wave function of the virtually excited electron-hole pair becomes asymmetric due to the electrostatic field applied to the semiconductor quantum well structure, and virtual charge polarization transiently occurs. Is used, both the rise and the fall of the response speed are related to the virtual carrier excitation process, and high-speed modulation of, for example, sub-picosecond is possible.
【００１４】[0014]
【実施例】先ず、量子井戸中での仮想電荷分極励起の現
象について説明する。この現象は、例えば、山西正道
応用物理 第５８巻，ｐｐ．１９６９−１７０７（１９
８９）に記載されている。図１はＤＣ（静）電界が量子
井戸積層方向に平行に印加された量子井戸構造を示し、
伝導帯の基底サブバンド１１及び価電子帯の基底サブバ
ンド１２の波動関数１３、１４は、傾斜したバンド構造
により、図の如く空間的にずれて非対称になっている。
この為に、ＤＣ電界を加えないときと比べて実効エネル
ギーギャップと振動子強度が変化し、光学的な分散特性
（光吸収率、屈折率の波長依存性）に変化が生じる。こ
の様な状況で、基底サブバンド１１、１２間の励起子エ
ネルギーギャップに対して離調（ｄｅｔｕｎｉｎｇ）し
た光子エネルギーｈνの非共鳴光をここに入射させる
と、コヒーレントな仮想遷移による電子励起が生じる。
この時、仮想励起された電子・正孔対の波動関数１７、
１８は、量子井戸構造に印加された上記ＤＣ電界の為に
図１に示す如く非対称になって、仮想電荷分極が光入力
の間のみ過渡的に生じる。この分極は、ＤＣ電界をスク
リーニングする方向、即ち減殺する方向に反電界Ｅとし
て働く。この過程は、仮想的なキャリア励起である為
に、その応答速度は立ち上がり、立ち下がり共にサブピ
コ秒となる。そして、この場合の反電界Ｅによる量子井
戸構造の電圧降下変化Ｖは量子井戸１つの幅をＬ、量子
井戸の数をＮとすると、Ｖ＝Ｅ×Ｌ×Ｎとなる。EXAMPLES First, the phenomenon of virtual charge polarization excitation in a quantum well will be described. This phenomenon is, for example, Masamichi Yamanishi
Applied Physics Vol. 58, pp. 1969-1707 (19
89). FIG. 1 shows a quantum well structure in which a DC (static) electric field is applied parallel to the quantum well stacking direction,
The wavefunctions 13 and 14 of the conduction band ground subband 11 and the valence band ground subband 12 are spatially displaced and asymmetric as shown in the figure due to the inclined band structure.
For this reason, the effective energy gap and the oscillator strength are changed as compared with the case where no DC electric field is applied, and the optical dispersion characteristics (light absorption rate and wavelength dependence of refractive index) are changed. In such a situation, when non-resonant light having photon energy hν that is detuned with respect to the exciton energy gap between the ground subbands 11 and 12 is injected into the excitonic energy gap, electronic excitation due to coherent virtual transition occurs. ..
At this time, the wave function 17 of the virtually excited electron-hole pair,
18 becomes asymmetric as shown in FIG. 1 due to the DC electric field applied to the quantum well structure, and virtual charge polarization occurs transiently only during light input. This polarization acts as a demagnetizing field E in the direction of screening the DC electric field, that is, in the direction of canceling it. Since this process is a virtual carrier excitation, its response speed rises and falls both in sub-picoseconds. Then, in this case, the voltage drop change V of the quantum well structure due to the counter electric field E is V = E × L × N, where L is the width of one quantum well and N is the number of quantum wells.
【００１５】ところで、量子井戸構造を構成する半導体
は、通常、静電界に対する構成原子配置での電気光学効
果（ポッケルス効果）を有しているので、元々印加され
ているＤＣ電界による電気光学効果に加えて上記の反電
界Ｅによって電気光学効果の変化が生じることになる。
このことは、概にＤＣ電界の印加により誘起されている
上記量子井戸構造の光学的異方性が反電界Ｅに発生によ
り更に変化することを意味する。By the way, since the semiconductor forming the quantum well structure usually has an electro-optical effect (Pockels effect) in the arrangement of constituent atoms with respect to an electrostatic field, the electro-optical effect due to the originally applied DC electric field is generated. In addition, the demagnetizing field E causes a change in electro-optical effect.
This means that the optical anisotropy of the quantum well structure, which is generally induced by the application of the DC electric field, is further changed by the generation of the anti-electric field E.
【００１６】この反電界Ｅによる電圧降下変化Ｖで生じ
る光学的異方性による屈折率の相対変化量Δψは次式で
与えられる。 Δψ＝２π／λ・ｑｎ3ｒeffＶ・・・・・（１） ここで、λは真空中の波長、ｑは結晶方位とＤＣ電界と
の相対関係に依存する定数、ｎは屈折率、ｒeffは実効
的な電気光学係数である。The relative change amount Δφ of the refractive index due to the optical anisotropy caused by the voltage drop change V due to the demagnetizing field E is given by the following equation. Δψ = 2π / λ · qn 3 r eff V (1) where λ is the wavelength in vacuum, q is a constant depending on the relative relationship between the crystal orientation and the DC electric field, and n is the refractive index. r eff is the effective electro-optic coefficient.
【００１７】本発明は、上記の様な屈折率の変化を利用
して、光の偏光状態を変化させ、光を変調するものであ
る。The present invention utilizes the above change in the refractive index to change the polarization state of light and modulate the light.
【００１８】図２は、本発明に用いられる半導体素子の
一例を示す略断面図である。図２において、符号１はｎ
+−ＧａＡｓ基板、符号２はｎ+−ＧａＡｓから成るエピ
タキシャル成長の為のバッファ層、符号３はｎ+−Ａｌ
ＧａＡｓから成るエッチングストップ層、符号４はｎ型
半導体から成る超格子構造のコンタクト層、符号５はノ
ンドープのイントリンシック（ｉ−）半導体から成る超
格子構造のバッファ層、符号６はｉ−半導体から成る多
重量子井戸層を夫々示す。また、符号７はｉ−半導体か
ら成る超格子構造のバッファ層、８はｐ型半導体から成
る超格子構造のコンタクト層、９はｐ+−ＡｌＧａＡｓ
から成るトップコンタクト層を夫々示す。FIG. 2 is a schematic sectional view showing an example of a semiconductor device used in the present invention. In FIG. 2, reference numeral 1 is n
+ -GaAs substrate, reference numeral 2 is a buffer layer made of n + -GaAs for epitaxial growth, reference numeral 3 is n + -Al
An etching stop layer made of GaAs, a reference numeral 4 is a contact layer of a superlattice structure made of an n-type semiconductor, a reference numeral 5 is a buffer layer of a superlattice structure made of an undoped intrinsic (i-) semiconductor, and a reference numeral 6 is made of an i-semiconductor. The respective multiple quantum well layers are shown. Reference numeral 7 is a buffer layer having a superlattice structure made of i-semiconductor, 8 is a contact layer having a superlattice structure made of p-type semiconductor, and 9 is p + -AlGaAs.
Each of the top contact layers is shown.
【００１９】トップコンタクト層９上には、ｐ型電極１
０が形成され、基板１の底面には、ｎ型電極２０が形成
されている。電極１０は、開孔２６を有するリング状に
形成され、開孔２６からは、後述するプローブ光及びポ
ンプ光から成る入射光２２が入射される。一方、電極２
０、基板１及びバッファ層２にも、開孔２７が形成され
ており、この開孔２７より偏光状態が変化した出射光２
３が出射する。電極１０及び２０の間には、電圧源２１
によって逆バイアスのＤＣ電圧が印加されている。A p-type electrode 1 is formed on the top contact layer 9.
0 is formed, and an n-type electrode 20 is formed on the bottom surface of the substrate 1. The electrode 10 is formed in a ring shape having an opening 26, and incident light 22 composed of probe light and pump light described later is incident from the opening 26. On the other hand, electrode 2
0, the substrate 1 and the buffer layer 2 also have an aperture 27 formed therein, and the emitted light 2 whose polarization state has changed from the aperture 27 is formed.
3 is emitted. A voltage source 21 is provided between the electrodes 10 and 20.
A reverse bias DC voltage is applied by.
【００２０】上記の半導体素子は、以下の様に作製され
た。まず、ｎ+−ＧａＡｓ基板１上に、厚さ０．５μｍ
のｎ+−ＧａＡｓバッファ層２、厚さ１μｍのｎ+−Ａｌ
ＧａＡｓエッチングストップ層３を順次成長させた。次
に、層３上に、厚さ２９Åのｎ+−ＧａＡｓ層と、厚さ
６９Åのｎ+−ＡｌＧａＡｓ層を交互に２０周期成長さ
せ、コンタクト層４を形成した。次に、層４上に、厚さ
２９Åのｉ−ＧａＡｓ層と、厚さ６９Åのｉ−ＡｌＧａ
Ａｓ層を交互に３０周期成長させ、バッファ層５を形成
した。次に、厚さ１００Åのｉ−ＡｌＧａＡｓから成る
井戸層と、厚さ１００Åのｉ−ＡｌＡｓから成るバリア
層とを、交互に２０周期成長させ、多重量子井戸層６を
形成した。次に、多重量子井戸層６上に、厚さ２９Åの
ｉ−ＧａＡｓ層と、厚さ６９Åのｉ−ＡｌＧａＡｓ層を
交互に３０周期成長させ、バッファ層７を形成した。次
に、層７上に、厚さ２９Åのｐ+−ＧａＡｓ層と、厚さ
６９Åのｐ+−ＡｌＧａＡｓ層を交互２０周期成長さ
せ、コンタクト層８を形成した。次に、層８上に厚さ１
μｍのｐ+−ＡｌＧａＡｓトップコンタクト層９を成長
させた。これらの半導体層の成長には、分子線エピタキ
シー（ＭＢＥ）を用いた。ＭＢＥの代わりに、有機金属
化学気相堆積（ＭＯ−ＣＶＤ）法を用いても良い。The above semiconductor device was manufactured as follows. First, 0.5 μm thick on the n + -GaAs substrate 1.
N + -GaAs buffer layer 2, 1 μm thick n + -Al
The GaAs etching stop layer 3 was sequentially grown. Next, on the layer 3, an n + -GaAs layer having a thickness of 29 Å and an n + -AlGaAs layer having a thickness of 69 Å were alternately grown for 20 cycles to form a contact layer 4. Next, on the layer 4, an i-GaAs layer having a thickness of 29Å and an i-AlGa having a thickness of 69Å are formed.
The As layer was alternately grown for 30 cycles to form the buffer layer 5. Next, a well layer made of i-AlGaAs having a thickness of 100 Å and a barrier layer made of i-AlAs having a thickness of 100 Å were alternately grown for 20 cycles to form a multiple quantum well layer 6. Next, on the multiple quantum well layer 6, an i-GaAs layer having a thickness of 29Å and an i-AlGaAs layer having a thickness of 69Å were alternately grown for 30 cycles to form a buffer layer 7. Then, on the layer 7, a p + -GaAs layer having a thickness of 29Å and a p + -AlGaAs layer having a thickness of 69Å were alternately grown for 20 cycles to form a contact layer 8. Then a thickness of 1 on layer 8
A μm p + -AlGaAs top contact layer 9 was grown. Molecular beam epitaxy (MBE) was used to grow these semiconductor layers. Instead of MBE, a metal organic chemical vapor deposition (MO-CVD) method may be used.
【００２１】次に、コンタクト層９上に、ＡｕＧｅ膜を
蒸着し、リング状の部分を残してエッチングすることに
よって、電極１０を形成した。基板１の底面には、Ｃｒ
ＡｕＮｉ膜を蒸着し、電極２０を形成した。最後に、電
極２０、基板１及びバッファ層２の一部を、エッチング
ストップ層３に達するまでエッチングし、開孔２７を形
成した。Next, an electrode 10 was formed by depositing an AuGe film on the contact layer 9 and performing etching while leaving a ring-shaped portion. On the bottom surface of the substrate 1, Cr
An AuNi film was deposited to form the electrode 20. Finally, the electrode 20, the substrate 1, and part of the buffer layer 2 were etched until reaching the etching stop layer 3 to form an opening 27.
【００２２】上記の様に作製された半導体素子の多重量
子井戸層のエネルギーバンド図を図３（ａ）及び（ｂ）
に示す。これらの図において、符号２４は量子井戸層
を、符号２５はバリア層を示す。図３（ａ）は、電圧源
２１から外部電界Ｅ0が印加されていない状態を示す。
量子井戸層２４は、ＡｌxＧａ1-xＡｓから形成され、バ
リア層は前述の様にＡｌＡｓから形成されている。ここ
で、井戸層２４におけるＡｌの組成比ｘは、ｘ＝０．３
から層厚方向に連続的に変化する様に形成され、井戸層
２４は、傾斜したバンドギャップを有している。Energy band diagrams of the multiple quantum well layers of the semiconductor device manufactured as described above are shown in FIGS. 3 (a) and 3 (b).
Shown in. In these figures, reference numeral 24 indicates a quantum well layer and reference numeral 25 indicates a barrier layer. FIG. 3A shows a state in which the external electric field E 0 is not applied from the voltage source 21.
The quantum well layer 24 is formed of Al x Ga 1-x As, the barrier layer is formed of AlAs as described above. Here, the Al composition ratio x in the well layer 24 is x = 0.3.
And the well layer 24 has an inclined band gap.
【００２３】上記の量子井戸構造に、電圧源２１より逆
バイアスの電界Ｅ0を印加すると、図３（ｂ）のように
エネルギー状態が変化する。この状態で、量子井戸構造
に仮想電荷励起を生じさせるポンプ光を入射させると、
図１で説明した様に、入射している間のみ、電荷の分極
が生じ、反電界Ｅが生じる。この反電界Ｅよって、印加
されている電圧はＶで示す値、降下する。When a reverse bias electric field E 0 is applied from the voltage source 21 to the above quantum well structure, the energy state changes as shown in FIG. 3 (b). In this state, when pump light that causes virtual charge excitation is incident on the quantum well structure,
As described with reference to FIG. 1, polarization of electric charges occurs only during the incidence, and a demagnetizing field E is generated. Due to this anti-electric field E, the applied voltage drops by a value indicated by V.
【００２４】上記電圧降下変化Ｖの値に関して、Ｍ．Ｙ
ａｍａｎｉｓｈｉ ａｎｄ Ｍ．Ｋｕｒｏｓａｋｉ，Ｉ
ＥＥＥ Ｊ．Ｑｕａｎｔｕｍ Ｅｒｅｃｔｒｏｎ，Ｖｏ
ｌ．ＱＥ−２４，ｐｐ．３２５〜３３１（１９８８）に
は、以下の様な数値例が記載されている。Regarding the value of the voltage drop change V, M. Y
amanishi and M.A. Kurosaki, I
EEE J. Quantum Electron, Vo
l. QE-24, pp. 325 to 331 (1988) describe the following numerical examples.
【００２５】即ち、図３（ａ）に示す様なＧａ1-xＡｌx
Ａｓ／ＡｌＡｓのグレーディドギャップ（ギャップが線
形に３０％まで変化している）量子井戸構造を考えて、
Ｌ（量子井戸幅）＝２０ｎｍ，Ｅ0（ＤＣ電界）＝９０
ｋＶ／ｃｍ、Ｎ（量子井戸数）＝２５、Ｉin（入力光強
度）＝ＩＧＷ／ｃｍ2で離調エネルギーが５０ｍｅＶと
するとＶ＝０．４Ｖとなる。この値を（１）式に代入し
て、量子井戸構造の積層方向を＜００１＞方位としλ＝
１．０６μｍ、ｑ＝１、ｎ＝３．４８、ｒeff＝１．４
×１０-12ｍ／Ｖを用いると、＜１１０＞と＜−１１０
＞方位間の相対的位相差はΔψ＝１．４×１０-4ラジア
ン＝０．００８°となる。この値は図６（ａ）〜（ｃ）
に示したＲａｌｐｈらの方法による結果と同程度の位相
変化である。この結果は、量子井戸がグレーデッドギャ
ップでない一定の構造でも上述と同程度の位相差が得ら
れることを示す。That is, Ga 1-x Al x as shown in FIG.
Considering the As / AlAs graded gap (the gap changes linearly up to 30%) quantum well structure,
L (quantum well width) = 20 nm, E 0 (DC electric field) = 90
When kV / cm, N (number of quantum wells) = 25, I in (input light intensity) = IGW / cm 2 and detuning energy of 50 meV, V = 0.4 V. Substituting this value into the equation (1), the stacking direction of the quantum well structure is defined as the <001> orientation, and λ =
1.06 μm, q = 1, n = 3.48, r eff = 1.4
Using x10 -12 m / V, <110> and <-110
> The relative phase difference between directions is Δψ = 1.4 × 10 −4 radian = 0.008 °. This value is shown in FIGS.
The phase change is similar to the result of the method of Ralph et al. This result shows that a phase difference similar to the above can be obtained even in a fixed structure in which the quantum well is not a graded gap.
【００２６】このような、位相変化、即ち、偏光状態の
変化を、偏光子で光の強度変化に変換すると、超高速の
光変調が可能となる。以下にこれを利用した本発明の光
変調装置を説明する。When such a phase change, that is, a change in the polarization state is converted into a change in the light intensity by the polarizer, it is possible to perform ultrahigh-speed light modulation. The optical modulator of the present invention utilizing this will be described below.
【００２７】図４は、本発明の光変調装置の一実施例を
示す概略図である。図４において、符号３１は、図２の
様な半導体素子を示す。また、符号３９は、半導体素子
３１に向けて偏光したプローブ光３３を出射するプロー
ブ光源、符号３８は、半導体素子３１に向けてポンプ光
３２を出射するポンプ光源、符号４０は、プローブ光源
３３とポンプ光３２を合成する光学素子を夫々示す。半
導体素子３１を透過して偏光状態が変化した光３４は、
位相板３５を透過し位相が調整される。位相板３５を透
過した光は、偏光子３６を透過することによって、偏光
状態の変化が強度変化に変換され、強度変調光３７とな
る。FIG. 4 is a schematic diagram showing an embodiment of the optical modulator of the present invention. In FIG. 4, reference numeral 31 indicates a semiconductor element as shown in FIG. Further, reference numeral 39 is a probe light source that emits the probe light 33 polarized toward the semiconductor element 31, reference numeral 38 is a pump light source that emits the pump light 32 toward the semiconductor element 31, and reference numeral 40 is a probe light source 33. Optical elements for combining the pump light 32 are shown respectively. The light 34 whose polarization state has changed after passing through the semiconductor element 31 is
The phase is transmitted through the phase plate 35 and the phase is adjusted. The light transmitted through the phase plate 35 is transmitted through the polarizer 36, whereby the change in the polarization state is converted into the intensity change and becomes the intensity-modulated light 37.
【００２８】図４において、ＤＣ電界の印加された半導
体素子３１に、前記の仮想電荷分極が誘起される適当な
波長と光強度を有するポンプ光３２を入射させると、量
子井戸構造に電圧変化が誘起される。そして、この半導
体素子３１に、素子を構成する半導体の結晶軸方向に対
して、適当な偏光状態のプローブ光３３を入射させる
と、このプローブ光は、量子井戸構造において、位相変
化Δψを受ける。例えば、プローブ光としては、図４の
ｚ軸を＜００１＞方位とするとｘ軸の＜１１０＞方位と
ｙ軸の＜−１１０＞方位に同じ大きさの成分を有する偏
光が用いられる。In FIG. 4, when a pump light 32 having an appropriate wavelength and light intensity for inducing the virtual charge polarization is incident on the semiconductor element 31 to which a DC electric field is applied, a voltage change occurs in the quantum well structure. Induced. Then, when the probe light 33 having an appropriate polarization state is made incident on the semiconductor element 31 in the crystal axis direction of the semiconductor constituting the element, the probe light undergoes a phase change Δψ in the quantum well structure. For example, as the probe light, polarized light having components of the same magnitude in the <110> direction of the x axis and the <−110> direction of the y axis is used when the z axis of FIG. 4 is the <001> direction.
【００２９】また、プローブ光３３は、この半導体素子
３１での光吸収を受けないが電気光学効果に十分感度の
ある波長を用いる様にするのが好ましい。こうして、半
導体素子３１の透過光３４は位相板３５と偏光子３６に
よりその位相変化が光強度の変化に変換され、変調光３
７として出力される。Further, it is preferable that the probe light 33 has a wavelength which is not absorbed by the semiconductor element 31 but is sufficiently sensitive to the electro-optical effect. In this way, the phase change of the transmitted light 34 of the semiconductor element 31 is converted into the change of the light intensity by the phase plate 35 and the polarizer 36, and the modulated light 3
It is output as 7.
【００３０】この変調光３７の光強度Ｉは、次式から求
められる。 Ｉ＝１／２・Ｉ0｛１＋ｓｉｎ２θｃｏｓψ｝・・・・（２） ここで、Ｉ0は透過光３４の全光強度、θはｘ軸方向に
対する偏光子３６の透過軸方位の角度である。また、位
相板３５のｘ軸方位とｙ軸方位との相対位相差をφ、プ
ローブ光３３のｘ軸方位とｙ軸方位との相対位相差を
ρ、半導体素子３１での入射プローブ光３３がないとき
の光学的異方性のｘ軸方位とｙ軸方位との相対位相差を
εとすると、ψは、 ψ＝Δψ＋ρ＋φ＋ε・・・・（３） と表わせる。従って、θ＝π／４として位相板３５の位
相差φを、 φ＝−ρ−ε±π／２・・・・（４） となる様に設定すると、 Ｉ＝１／２・Ｉ0｛１±ｓｉｎΔψ｝・・・・（５） となる（式（４）（５）の複号は順不同である）。ここ
で注意することは、相対位相変化量Δψの変化を最も感
度良くする為にバイアス点をψ＝±π／２に設定したこ
とである。上述の例では、プローブ光３３の両直交偏光
成分の位相差を任意としていたが、（４）式を満足する
様に予め位相差ρを与えておいても良い。こうした場合
には、位相板３５は図４の位置に置く必要はなくなる。
即ち、位相板３５を半導体素子３１よりも前に置いて
（４）式を満たす様にしても良い。或は、プローブ光３
３として位相差ρが±π／２の円偏光を用いて、ウォラ
ストン・プリズムや偏光プリズム等でｘ軸偏光とｙ軸偏
光とを分けて差動検出を行なっても良い。The light intensity I of the modulated light 37 is obtained from the following equation. I = 1/2 · I 0 {1 + sin2θ cos ψ} ... (2) where I 0 is the total light intensity of the transmitted light 34, and θ is the angle of the transmission axis azimuth of the polarizer 36 with respect to the x-axis direction. Further, the relative phase difference between the x-axis azimuth and the y-axis azimuth of the phase plate 35 is φ, the relative phase difference between the x-axis azimuth and the y-axis azimuth of the probe light 33 is ρ, and the incident probe light 33 at the semiconductor element 31 is Letting ε be the relative phase difference between the x-axis azimuth and the y-axis azimuth of the optical anisotropy when not present, ψ can be expressed as ψ = Δψ + ρ + φ + ε ... (3). Therefore, when θ = π / 4 and the phase difference φ of the phase plate 35 is set to be φ = −ρ−ε ± π / 2 (4), I = 1/2 · I 0 { 1 ± sin Δψ} ... (5) (the compound signs of the equations (4) and (5) are in no particular order). Note that the bias point is set to ψ = ± π / 2 in order to maximize the sensitivity of the change in the relative phase change amount Δψ. In the above example, the phase difference between the two orthogonal polarization components of the probe light 33 is arbitrary, but the phase difference ρ may be given in advance so as to satisfy the expression (4). In such a case, the phase plate 35 need not be placed at the position shown in FIG.
That is, the phase plate 35 may be placed in front of the semiconductor element 31 to satisfy the expression (4). Or probe light 3
Alternatively, circularly polarized light having a phase difference ρ of ± π / 2 may be used as 3, and differential detection may be performed by separating the x-axis polarized light and the y-axis polarized light with a Wollaston prism or a polarization prism.
【００３１】上記の例の様に、本発明ではプローブ光３
３の波長は電気光学効果に対して感度がある領域にあれ
ば良いので、半導体素子３１に対して光吸収の無い波長
を広い波長域に亙って選択することができるという特長
がある。また、図４の例で２つに分けたポンプ光３２と
プローブ光３３を１つにして、ポンプ光のみで両者を兼
ねる様にしても良い。この場合でも仮想電荷誘起を起こ
すのみであるからポンプ光の光吸収は非常に少ない。As in the above example, the probe light 3 is used in the present invention.
Since the wavelength of 3 need only be in a region sensitive to the electro-optical effect, it has a feature that a wavelength that does not absorb light with respect to the semiconductor element 31 can be selected over a wide wavelength range. Further, the pump light 32 and the probe light 33, which are divided into two in the example of FIG. 4, may be combined into one, and the pump light alone may serve as both. Even in this case, since the virtual charge is only induced, the light absorption of the pump light is very small.
【００３２】図４の上記実施例では、ポンプ光３２とプ
ローブ光３３が素子３１の量子井戸構造に対して垂直に
入射する場合を示したが、ポンプ光３２とプローブ光３
３が量子井戸構造に対して平行に入射する場合や、ポン
プ光３２或はプローブ光３３の一方が量子井戸構造に対
して垂直で他方が量子井戸構造に対して平行に入射する
場合でも同様の効果が得られる。この場合、量子井戸構
造に対して垂直な方向に導波路構造を形成してポンプ光
３２或はプローブ光３３を導波させることが、相互作用
長及び光強度を増大する意味で望ましい。Although the pump light 32 and the probe light 33 are incident perpendicularly to the quantum well structure of the element 31 in the above embodiment of FIG. 4, the pump light 32 and the probe light 3 are shown.
Similarly, when 3 is incident parallel to the quantum well structure, or when one of the pump light 32 and the probe light 33 is perpendicular to the quantum well structure and the other is parallel to the quantum well structure. The effect is obtained. In this case, it is desirable to form a waveguide structure in a direction perpendicular to the quantum well structure to guide the pump light 32 or the probe light 33 in order to increase the interaction length and the light intensity.
【００３３】また、素子３１の量子井戸構造の両側に高
反射率の薄膜構造を形成して共振器構造を作り、仮想電
荷励起がないときに（即ちポンプ光が入力していないと
きに）ＤＣ電界印加により電気光学効果を介して生じて
いる光学的異方性の一方の光学軸に対する屈折率につい
て該共振器が共振条件を満たす（或は満たさない）様に
しても良い。この構成によって、仮想電荷励起が起きた
時に該共振条件が変化して該光学軸に平行な偏光成分の
プローブ光透過率或は反射率が大きく変化するので、プ
ローブ光の透過光或は反射光の偏光状態が大きく変化
し、検出時のＳ／Ｎが向上する。Further, a thin film structure having high reflectance is formed on both sides of the quantum well structure of the device 31 to form a resonator structure, and DC is generated when there is no virtual charge excitation (that is, when pump light is not input). The resonator may (or may not) satisfy the resonance condition with respect to the refractive index with respect to one optical axis of the optical anisotropy generated by the electric field application through the electro-optical effect. With this configuration, when virtual charge excitation occurs, the resonance condition changes and the probe light transmittance or reflectance of the polarization component parallel to the optical axis changes significantly, so that the transmitted light or reflected light of the probe light is changed. The polarization state of 1 changes significantly, and the S / N at the time of detection is improved.
【００３４】[0034]
【発明の効果】以上説明した如く、本発明によれば、Ｄ
Ｃ（静）電界印加した量子井戸を有する半導体量子井戸
構造において、例えば、超短パルスの光により仮想的に
量子井戸中に電荷（電子・正孔対）を励起して量子井戸
中でのＤＣ電界を該超短パルスにより変調することで、
該変調された電界により該量子井戸を構成する半導体が
有する電気光学効果を介して該量子井戸構造の光学的異
方性の大きさを変調し、該量子井戸構造中を伝搬する光
の偏光状態を変調する様にしているので、例えば、サブ
ピコ秒の立ち上がり、立ち下がり応答時間の光の位相及
び強度変調が可能となり高速光変調、スイッチングなど
が実現できる。As described above, according to the present invention, D
In a semiconductor quantum well structure having a quantum well to which a C (static) electric field is applied, for example, a charge (electron / hole pair) is virtually excited in the quantum well by light of an ultrashort pulse to generate DC in the quantum well. By modulating the electric field with the ultrashort pulse,
The polarization state of light propagating in the quantum well structure by modulating the magnitude of the optical anisotropy of the quantum well structure through the electro-optic effect of the semiconductor forming the quantum well by the modulated electric field. Is modulated, it is possible to modulate the phase and intensity of light with subpicosecond rise and fall response times, and high-speed optical modulation and switching can be realized.
【図１】本発明における仮想電荷分極励起を説明するた
めのエネルギーバンド図である。FIG. 1 is an energy band diagram for explaining virtual charge polarization excitation in the present invention.
【図２】本発明に用いられる半導体素子の一例を示す略
断面図である。FIG. 2 is a schematic cross-sectional view showing an example of a semiconductor element used in the present invention.
【図３】（ａ）は電界が印加されていない状態の図２の
量子井戸層のエネルギーバンド図、（ｂ）は電界が印加
された状態の図２の量子井戸層のエネルギーバンド図で
ある。3A is an energy band diagram of the quantum well layer of FIG. 2 in a state where no electric field is applied, and FIG. 3B is an energy band diagram of the quantum well layer of FIG. 2 in which an electric field is applied. ..
【図４】本発明の光変調装置の一実施例を示す概略図で
ある。FIG. 4 is a schematic diagram showing an embodiment of an optical modulator of the present invention.
【図５】従来のＰＲ効果による屈折率変化の原理を説明
する為のエネルギーバンド図である。FIG. 5 is an energy band diagram for explaining the principle of conventional refractive index change due to the PR effect.
【図６】ＰＲ効果を用いた従来の電気光学素子の例を説
明する為のエネルギーバンド図である。FIG. 6 is an energy band diagram for explaining an example of a conventional electro-optical element using the PR effect.
１ 基板 ２ バッファ層 ３ エッチングストップ層 ４ ｎ型の超格子構造のコンタクト層 ５，７ 超格子構造のバッファ層 ６ 多重量子井戸層 ８ ｐ型の超格子構造のコンタクト層 ９ トップコンタクト層 １０ ｐ型電極 ２０ ｎ型電極 ２１ 電圧源 ２６，２７ 開孔 １１ ＤＣ電界印加時の量子井戸での伝導帯の
最低サブバンド １２ ＤＣ電界印加時の量子井戸での価電子帯
の最低サブバンド １３，１４ 夫々最低サブバンド１１，１２に対応す
る電子と正孔の波動関数 １５，１６ デチューニングした光パルス入射で励起
された仮想電荷を表わす伝導帯と価電子帯のサブレベル １７，１８ 夫々サブレベル１５，１６に対応する仮
想的な電子と正孔の波動関数 ３１ 半導体素子 ３５ 位相板 ３６ 偏光子 ３８ ポンプ光源 ３９ プローブ光源 ４０ ポンプ光・プローブ光合成用光学素子 ２４ 量子井戸層 ２５ バリア層1 substrate 2 buffer layer 3 etching stop layer 4 n-type superlattice structure contact layer 5, 7 superlattice structure buffer layer 6 multiple quantum well layer 8 p-type superlattice structure contact layer 9 top contact layer 10 p-type Electrode 20 n-type electrode 21 Voltage source 26, 27 Open hole 11 Minimum subband of conduction band in quantum well when DC electric field is applied 12 Minimum subband of valence band in quantum well when DC electric field is applied 13, 14 respectively Electron and hole wavefunctions corresponding to the lowest subbands 11, 12 15 and 16 Sublevels of conduction band and valence band representing virtual charges excited by detuning light pulse injection 17, 18 Sublevels 15, 18 respectively Virtual wave function of electrons and holes corresponding to 16 31 Semiconductor element 35 Phase plate 36 Polarizer 38 Pump light source 39 Probe light source 40 Pump Probe light combining optical element 24 quantum well layer 25 a barrier layer
Claims (25)
置：量子井戸構造を備えた半導体素子；半導体素子の量
子井戸構造に電界を印加する手段；半導体素子に偏光し
たプローブ光を入射する手段、該プローブ光は、量子井
戸構造における電気光学効果によって、その偏光状態が
変化して半導体素子から出射される；半導体素子に、そ
の量子井戸構造に仮想電荷励起を生じさせるポンプ光を
入射する手段、ここで、仮想電荷励起によって、量子井
戸構造に印加された電界がスクリーンされる；及び半導
体素子から出射した光の偏光状態の変化を強度変化に変
換する偏光子。1. A light modulator comprising: a semiconductor element having a quantum well structure; means for applying an electric field to the quantum well structure of the semiconductor element; means for injecting polarized probe light into the semiconductor element. , The probe light is emitted from the semiconductor element by changing its polarization state due to the electro-optic effect in the quantum well structure; means for injecting pump light that causes virtual charge excitation in the quantum well structure into the semiconductor element , Where the electric field applied to the quantum well structure is screened by virtual charge excitation; and a polarizer that converts changes in the polarization state of light emitted from a semiconductor device into changes in intensity.
井戸層をサンドイッチにしたバリア層とから成り、前記
井戸層は、層厚方向に傾斜したバンドキャップを有する
請求項１記載の光変調装置。2. The light according to claim 1, wherein the quantum well structure includes a quantum well layer and a barrier layer sandwiching the well layer, and the well layer has a band cap inclined in a layer thickness direction. Modulator.
に配置された位相板から成る請求項１記載の光変調装
置。3. The optical modulator according to claim 1, further comprising a phase plate arranged in the optical path of the probe light reaching the polarizer.
１＞方位をｚ方向、＜１１０＞方位をｘ方向及び＜−１
１０＞方位をｙ方向としたとき、プローブ光は、そのｘ
方向の偏光成分とｙ方向の偏光成分とが等しい大きさを
有し、半導体素子にｚ方向に入射される請求項１記載の
光変調装置。4. The crystal <00 of the semiconductor element.
The 1> direction is the z direction, the <110> direction is the x direction, and the <-1
When the 10> azimuth is the y direction, the probe light is
The optical modulator according to claim 1, wherein the polarization component in the direction and the polarization component in the y direction have the same magnitude and are incident on the semiconductor element in the z direction.
に配置された位相板から成り、偏光子の透過軸方位のｘ
方向に対する角度をθ、プローブ光が入射していないと
きの半導体素子のｘ方向とｙ方向との相対位相差をε、
プローブ光のｘ方向の偏光成分とｙ方向の偏光成分との
相対位相差をρ、位相板の位相差をφとしたときに、以
下の条件を満足する請求項４記載の光変調装置。 θ＝π／４ φ＝−ρ−ε±π／２5. A phase plate arranged in the optical path of probe light reaching the polarizer, wherein x is a transmission axis direction of the polarizer.
The angle with respect to the direction is θ, the relative phase difference between the x direction and the y direction of the semiconductor element when the probe light is not incident is ε,
The optical modulator according to claim 4, wherein the following condition is satisfied, where ρ is the relative phase difference between the polarization component of the probe light in the x direction and the polarization component in the y direction, and φ is the phase difference of the phase plate. θ = π / 4 φ = −ρ−ε ± π / 2
る量子井戸構造を備えた半導体素子及び偏光子を用い
て、光を変調する方法：半導体素子の量子井戸構造に電
界を印加する；半導体素子に偏光したプローブ光を入射
する、該プローブ光は、量子井戸構造における電気光学
効果によって、その偏光状態が変化して半導体素子から
出射される；半導体素子に、その量子井戸構造に仮想電
荷励起を生じさせるポンプ光を入射する、ここで、仮想
電荷励起によって、量子井戸構造に印加された電界がス
クリーニングされる；及び半導体素子から出射した光の
偏光状態の変化を偏光子によって強度変化に変換する。6. A method of modulating light using a semiconductor device having a quantum well structure and a polarizer, comprising the steps of: applying an electric field to the quantum well structure of the semiconductor device; Polarized probe light is incident on the quantum well structure, the probe light changes its polarization state due to the electro-optic effect in the quantum well structure, and is emitted from the semiconductor element; Inject pump light to be generated, where electric field applied to quantum well structure is screened by virtual charge excitation; and change in polarization state of light emitted from semiconductor device is converted into intensity change by polarizer ..
１＞方位をｚ方向、＜１１０＞方位をｘ方向及び＜−１
１０＞方位をｙ方向としたとき、プローブ光は、そのｘ
方向の偏光成分とｙ方向の偏光成分とが等しい大きさを
有し、半導体素子にｚ方向に入射される請求項６記載の
光変調装置。7. <00 of crystals constituting the semiconductor element
The 1> direction is the z direction, the <110> direction is the x direction, and the <-1
When the 10> azimuth is the y direction, the probe light is
7. The light modulation device according to claim 6, wherein the polarization component in the direction and the polarization component in the y direction have the same magnitude and are incident on the semiconductor element in the z direction.
板が設けられ、偏光子の透過軸方位のｘ方向に対する角
度をθ、プローブ光が入射していないときの半導体素子
のｘ方向とｙ方向との相対位相差をε、プローブ光のｘ
方向の偏光成分とｙ方向の偏光成分との相対位相差を
ρ、位相板の位相差をφとしたときに、以下の条件を満
足する請求項７記載の光変調装置。 θ＝π／４ φ＝−ρ−ε±π／２8. A phase plate is provided in the optical path of the probe light reaching the polarizer, and the angle of the transmission axis azimuth of the polarizer with respect to the x direction is θ, and the x direction of the semiconductor element when the probe light is not incident. The relative phase difference from the y direction is ε, and the probe light x
8. The optical modulator according to claim 7, wherein the following conditions are satisfied, where ρ is a relative phase difference between a polarized component in the directional direction and a polarized component in the y direction and φ is a phase difference of the phase plate. θ = π / 4 φ = −ρ−ε ± π / 2
状態を変化させる装置：量子井戸構造を備えた半導体素
子；半導体素子の量子井戸構造に電界を印加する手段；
半導体素子に偏光したプローブ光を入射する手段、該プ
ローブ光は、量子井戸構造における電気光学効果によっ
て、その偏光状態が変化して半導体素子から出射され
る；及び半導体素子に、その量子井戸構造に仮想電荷励
起を生じさせるポンプ光を入射する手段、ここで、仮想
電荷励起によって、量子井戸構造に印加された電界がス
クリーニングされる。9. A device for changing the polarization state of light, comprising: a semiconductor device having a quantum well structure; means for applying an electric field to the quantum well structure of the semiconductor device;
Means for injecting polarized probe light into the semiconductor device, the probe light being emitted from the semiconductor device with its polarization state changed by the electro-optical effect in the quantum well structure; and to the semiconductor device. Means for injecting pump light that causes virtual charge excitation, where virtual charge excitation screens the electric field applied to the quantum well structure.
該井戸層をサンドイッチにしたバリア層とから成り、前
記井戸層は、層厚方向に傾斜したバンドギャップを有す
る請求項９記載の光変調装置。10. The quantum well structure comprises a quantum well layer,
10. The optical modulator according to claim 9, further comprising a barrier layer in which the well layer is sandwiched, and the well layer has a band gap inclined in a layer thickness direction.
０１＞方位をｚ方向、＜１１０＞方位をｘ方向および＜
−１１０＞方位をｙ方向としたとき、プローブ光は、そ
のｘ方向の偏光成分とｙ方向の偏光成分とが等しい大き
さを有し、半導体素子にｚ方向に入射される請求項９記
載の光変調装置。11. <0 of a crystal forming the semiconductor element
The 01> direction is the z direction, the <110> direction is the x direction, and
The probe light having a polarization component in the x direction and a polarization component in the y direction having the same magnitude when the −110> azimuth is set in the y direction, and is incident on the semiconductor element in the z direction. Light modulator.
する量子井戸構造を備えた半導体素子を用いて、光の偏
光状態を変化させる方法：半導体素子の量子井戸構造に
電界を印加する；半導体素子に偏光したプローブ光を入
射する、該プローブ光は、量子井戸構造における電気光
学効果によって、その偏光状態が変化して半導体素子か
ら出射される；及び半導体素子に、その量子井戸構造に
仮想電荷励起を生じさせるポンプ光を入射する、ここ
で、仮想電荷励起よって、量子井戸構造に印加された電
界がスクリーニングされる。12. A method of changing the polarization state of light using a semiconductor device having a quantum well structure, which comprises the steps of: applying an electric field to the quantum well structure of the semiconductor device; Polarized probe light is incident on the quantum well structure, the probe light changes its polarization state due to the electro-optic effect in the quantum well structure, and is emitted from the semiconductor device; and the semiconductor device has virtual charge excitation in the quantum well structure. The pumping light that causes is generated, where the electric field applied to the quantum well structure is screened by virtual charge excitation.
０１＞方位をｚ方向、＜１１０＞方位をｘ方向及び＜−
１１０＞方位をｙ方向としたとき、プローブ光は、その
ｘ方向の偏光成分とｙ方向の偏光成分とが等しい大きさ
を有し、半導体素子にｚ方向に入射される請求項１２記
載の光変調装置。13. The crystal of the semiconductor element is <0.
The 01> direction is the z direction, the <110> direction is the x direction, and the <−
13. The light according to claim 12, wherein when the 110> azimuth is the y direction, the probe light has a polarization component in the x direction and a polarization component in the y direction that are equal to each other and is incident on the semiconductor element in the z direction. Modulator.
装置： （ａ）以下のものから成る半導体素子、基板；基板上に
形成された第１の導電型を有する第１の半導体層；第１
の半導体層上に形成された多量子井戸層；多重量子井戸
層上に形成された第２の導電型を有する第２の半導体
層；及び第１及び第２の半導体層に各々電気的にコンタ
クトされた一対の電極； （ｂ）半導体素子に逆バイアスの電界を印加する、前記
電極に接続された電圧源； （ｃ）半導体素子に偏光したプローブ光を入射する手
段、該プローブ光は、多重量子井戸層における電気光学
効果によって、その偏光状態が変化して半導体素子から
出射される； （ｄ）半導体素子に、その多重量子井戸層に仮想電荷励
起を生じさせるポンプ光を入射する手段、ここで、仮想
電荷励起によって、量子井戸構造に印加された電界がス
クリーニングされる；及び （ｅ）半導体素子から出射した光の偏光状態の変化を強
度変化に変換する偏光子。14. A light modulating device comprising: (a) a semiconductor element comprising the following: a substrate; a first semiconductor layer having a first conductivity type formed on the substrate; 1
A multi-quantum well layer formed on the semiconductor layer; a second semiconductor layer having a second conductivity type formed on the multi-quantum well layer; and electrically contacting the first and second semiconductor layers, respectively. Paired electrodes; (b) a voltage source connected to the electrodes for applying a reverse bias electric field to the semiconductor element; (c) means for injecting polarized probe light into the semiconductor element; The polarization state is changed by the electro-optic effect in the quantum well layer and emitted from the semiconductor element; (d) means for injecting pump light that causes virtual charge excitation in the multiple quantum well layer into the semiconductor element, here. Then, the electric field applied to the quantum well structure is screened by the virtual charge excitation; and (e) a polarizer that converts a change in the polarization state of light emitted from the semiconductor element into an intensity change.
戸層と、複数のバリア層とが交互に積層されて成り、量
子井戸層は、層厚方向に傾斜したバンドギャップを有す
る請求項１４記載の光変調装置。15. The multiple quantum well layer is formed by alternately stacking a plurality of quantum well layers and a plurality of barrier layers, and the quantum well layers have a band gap inclined in a layer thickness direction. The light modulator described.
から成る複数の量子井戸層と、ＡｌＧａＡｓから成る複
数のバリア層とが交互に積層されて成る請求項１４記載
の光変調装置。16. The multi-quantum well layer is AlGaAs
15. The optical modulator according to claim 14, wherein a plurality of quantum well layers made of AlGaAs and a plurality of barrier layers made of AlGaAs are alternately laminated.
透過させる為の開孔が設けられている請求項１４記載の
光変調装置。17. The optical modulator according to claim 14, wherein the substrate and the electrode are provided with an opening for transmitting probe light.
中に配置された位相板から成る請求項１４記載の光変調
装置。18. The optical modulator according to claim 14, further comprising a phase plate arranged in the optical path of the probe light reaching the polarizer.
０１＞方位をｚ方向、＜１１０＞方位をｘ方向及び＜−
１１０＞方位をｙ方向としたとき、プローブ光は、その
ｘ方向の偏光成分とｙ方向の偏光成分とが等しい大きさ
を有し、半導体素子にｚ方向に入射される請求項１４記
載の光変調装置。19. <0 of a crystal forming the semiconductor element
The 01> direction is the z direction, the <110> direction is the x direction, and the <−
15. The light according to claim 14, wherein the probe light has a polarization component in the x direction and a polarization component in the y direction that are equal to each other when the 110> azimuth is in the y direction, and is incident on the semiconductor element in the z direction. Modulator.
中に配置された位相板から成り、偏光子の透過軸方位の
ｘ方向に対する角度をθ、プローブ光が入射していない
ときの半導体素子のｘ方向とｙ方向との相対位相差を
ε、プローブ光のｘ方向の偏光成分とｙ方向の偏光成分
との相対位相差をρ、位相板の位相差をφとしたとき
に、以下の条件を満足する請求項１９記載の光変調装
置。 θ＝π／４ φ＝−ρ−ε±π／２20. A semiconductor device comprising a phase plate arranged in the optical path of probe light reaching the polarizer, wherein the angle of the transmission axis azimuth of the polarizer with respect to the x direction is θ, and no probe light is incident. Where ε is the relative phase difference between the x direction and the y direction, ρ is the relative phase difference between the polarization component of the probe light in the x direction and the y direction, and φ is the phase difference of the phase plate, The optical modulator according to claim 19, which satisfies the condition. θ = π / 4 φ = −ρ−ε ± π / 2
光状態を変化させる装置： （ａ）以下のものから成る半導体素子、基板；基板上に
形成された第１の導電型を有する第１の半導体層；第１
の半導体層上に形成された多重量子井戸層；多重量子井
戸層上に形成された第２の導電型を有する第２の半導体
層；及び第１及び第２の半導体層に各々電気的にコンタ
クトされた一対の電極； （ｂ）半導体素子に逆バイアスの電界を印加する、前記
電極に接続された電圧源； （ｃ）半導体素子に偏光したプローブ光を入射する手
段、該プローブ光は、多重量子井戸層における電気光学
効果によって、その偏光状態が変化して半導体素子から
出射される；及び （ｄ）半導体素子に、その多重量子井戸層に仮想電荷励
起を生じさせるポンプ光を入射する手段、ここで、仮想
電荷励起によって、量子井戸構造に印加された電界がス
クリーニングされる。21. A device for changing the polarization state of light, comprising: (a) a semiconductor element consisting of: a substrate; a first having a first conductivity type formed on the substrate. Semiconductor layer; first
Multiple quantum well layer formed on the semiconductor layer; second semiconductor layer having a second conductivity type formed on the multiple quantum well layer; and electrically contacting the first and second semiconductor layers, respectively. Paired electrodes; (b) a voltage source connected to the electrodes for applying a reverse bias electric field to the semiconductor element; (c) means for injecting polarized probe light into the semiconductor element; The polarization state is changed by the electro-optic effect in the quantum well layer and emitted from the semiconductor element; and (d) means for injecting pump light that causes virtual charge excitation in the multiple quantum well layer into the semiconductor element, Here, the electric field applied to the quantum well structure is screened by virtual charge excitation.
戸層と、複数のバリア層とが交互に積層されて成り、量
子井戸層は、層厚方向に傾斜したバンドギャップを有す
る請求項２１記載の光変調装置。22. The multiple quantum well layer is formed by alternately stacking a plurality of quantum well layers and a plurality of barrier layers, and the quantum well layers have a band gap inclined in the layer thickness direction. The light modulator described.
から成る複数の量子井戸層と、ＡｌＡｓから成る複数の
バリア層とが交互に積層されて成る請求項２１記載の光
変調装置。23. The multi-quantum well layer is made of AlGaAs.
22. The optical modulator according to claim 21, wherein a plurality of quantum well layers made of Al and a plurality of barrier layers made of AlAs are alternately laminated.
透過させる為の開孔が設けられている請求項２１記載の
光変調装置。24. The optical modulator according to claim 21, wherein the substrate and the electrode are provided with openings for transmitting probe light.
０１＞方位をｚ方向、＜１１０＞方位をｘ方向及び＜−
１１０＞方位をｙ方向としたとき、プローブ光は、その
ｘ方向の偏光成分とｙ方向の偏光成分とが等しい大きさ
を有し、半導体素子にｚ方向に入射される請求項２１記
載の光変調装置。25. <0 of a crystal forming the semiconductor element
The 01> direction is the z direction, the <110> direction is the x direction, and the <−
22. The light according to claim 21, wherein the probe light has a polarization component in the x direction and a polarization component in the y direction that are equal to each other when the 110> azimuth is in the y direction, and is incident on the semiconductor element in the z direction. Modulator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3178654A JPH05173200A (en) | 1990-07-02 | 1991-06-24 | Method and device for modulating light by using semiconductor element of quantum well structure |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17507990 | 1990-07-02 | ||
| JP2-175079 | 1990-07-02 | ||
| JP3178654A JPH05173200A (en) | 1990-07-02 | 1991-06-24 | Method and device for modulating light by using semiconductor element of quantum well structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05173200A true JPH05173200A (en) | 1993-07-13 |
Family
ID=26496456
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3178654A Pending JPH05173200A (en) | 1990-07-02 | 1991-06-24 | Method and device for modulating light by using semiconductor element of quantum well structure |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05173200A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20200050048A1 (en) * | 2018-08-07 | 2020-02-13 | Sharp Kabushiki Kaisha | Display device |
| US11204621B2 (en) * | 2015-10-30 | 2021-12-21 | Essential Products, Inc. | System comprising a display and a camera that captures a plurality of images corresponding to a plurality of noncontiguous pixel regions |
-
1991
- 1991-06-24 JP JP3178654A patent/JPH05173200A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11204621B2 (en) * | 2015-10-30 | 2021-12-21 | Essential Products, Inc. | System comprising a display and a camera that captures a plurality of images corresponding to a plurality of noncontiguous pixel regions |
| US20200050048A1 (en) * | 2018-08-07 | 2020-02-13 | Sharp Kabushiki Kaisha | Display device |
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