JPH06186602A - Nonlinear optical element - Google Patents
Nonlinear optical elementInfo
- Publication number
- JPH06186602A JPH06186602A JP34186392A JP34186392A JPH06186602A JP H06186602 A JPH06186602 A JP H06186602A JP 34186392 A JP34186392 A JP 34186392A JP 34186392 A JP34186392 A JP 34186392A JP H06186602 A JPH06186602 A JP H06186602A
- Authority
- JP
- Japan
- Prior art keywords
- optical element
- optical waveguide
- area
- optical
- layer
- 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.)
- Granted
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、非線形光学素子に関
し、特に光ファイバ通信や光情報処理等の分野で光制御
素子として用いられる非線形光学素子に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonlinear optical element, and more particularly to a nonlinear optical element used as an optical control element in the fields of optical fiber communication and optical information processing.
【０００２】[0002]
【従来の技術】光ファイバ通信システムや光情報処理シ
ステムの高速化には、光制御を行う素子の動作の高速化
が必要不可欠である。従来、光制御素子においては、電
気信号により光制御を行う方法（電気−光制御）がとら
れてきたが、近年、より高速の動作が期待される方法と
して、光により光制御を行う方法（光−光制御）が注目
されている。光−光制御方式を用いた場合の利点とし
て、電気回路のＣＲ時定数により動作速度が制限されな
いこと、電気パルスよりも超短パルス発生の容易な光パ
ルスが利用可能であることなどが挙げられる。2. Description of the Related Art In order to increase the speed of an optical fiber communication system or an optical information processing system, it is necessary to increase the speed of the operation of an element that performs optical control. Conventionally, in a light control element, a method of performing light control by an electric signal (electric-light control) has been taken, but in recent years, as a method expected to operate at a higher speed, a method of performing light control by light ( Light-light control) is drawing attention. The advantages of using the light-light control method are that the operating speed is not limited by the CR time constant of the electric circuit, and that an optical pulse that can generate an ultrashort pulse is easier than an electric pulse can be used. .
【０００３】例えば、特開平４−３１２５号公報には、
光吸収により非線形屈折率変化を示す光導波部に静電界
を印加する手段を有する非線形光学素子が記載されてい
る。この素子の光導波部では、制御光が吸収され、励起
されたキャリアによるバンドフィリング効果によって非
線形屈折率変化が引き起こされる。この非線形屈折率変
化により、光導波部を伝搬する信号光が位相変調され
る。ここで、光吸収による非線形屈折率変化の発現は非
常に高速であるが、その消失は光励起さたキャリアの寿
命（〜数ｎＳ）により決まるため、高速動作は不可能で
ある。そこで特開平４−３１２５号公報に記載の非線形
光学素子では、この素子の光導波部に静電界が印加され
ることにより、励起されたキャリアを光導波部外に掃引
することを提案している。バンドフィリング効果が前記
掃引時間で消失し、非線形屈折率変化が回復する。すな
わち、この素子では、動作速度がバンド間緩和時間で制
限されず、高速の光制御が可能になる。For example, Japanese Patent Application Laid-Open No. 4-3125 discloses that
A non-linear optical element having means for applying an electrostatic field to an optical waveguide section that exhibits a non-linear refractive index change by light absorption is described. In the optical waveguide portion of this element, the control light is absorbed, and the nonlinear refractive index change is caused by the band-filling effect of the excited carriers. Due to this change in the nonlinear refractive index, the signal light propagating through the optical waveguide is phase-modulated. Here, although the nonlinear refractive index change due to light absorption is very fast, the disappearance thereof is determined by the life of the photoexcited carrier (up to several nS), and thus high-speed operation is impossible. Therefore, in the nonlinear optical element described in Japanese Patent Laid-Open No. 4-3125, it is proposed that an excited electric field is applied to the optical waveguide section of this element to sweep the excited carriers to the outside of the optical waveguide section. . The band-filling effect disappears in the sweep time, and the nonlinear refractive index change is recovered. That is, in this element, the operation speed is not limited by the interband relaxation time, and high-speed optical control is possible.
【０００４】[0004]
【発明が解決しようとする課題】上記のような電界によ
る光キャリア掃引を行う素子において重要なことは、常
に光導波部に高い静電界が印加されていることである。
しかし実際には、光励起キャリアにより光電流が生じ、
このため光導波部以外の種々の電気抵抗に電圧降下が生
ずる結果、重要な光導波部における電界強度が低下する
という問題があった。したがって高い変調度を得るべく
高密度の光キャリアを生成すると、上記電界強度の低下
により、高速性が損なわれるという問題があった。What is important in the above-mentioned device for performing optical carrier sweeping by an electric field is that a high electrostatic field is always applied to the optical waveguide portion.
However, in reality, photoexcited carriers generate photocurrent,
Therefore, as a result of a voltage drop occurring in various electric resistances other than the optical waveguide portion, there is a problem that the electric field strength in the important optical waveguide portion decreases. Therefore, when a high-density optical carrier is generated in order to obtain a high degree of modulation, there is a problem that the high speed is impaired due to the decrease in the electric field strength.
【０００５】本発明の目的は、このような問題を解決し
た非線形光学素子を提供することにある。An object of the present invention is to provide a non-linear optical element that solves such a problem.
【０００６】[0006]
【課題を解決するための手段】本発明の非線形光学素子
は、光吸収により非線形屈折率変化を生ずる半導体材料
からなるコア層とこのコア層に接合するクラッド層とで
層に垂直な方向に光導波構造を形成し、層に水平な方向
にも光導波構造を実現する手段を有し、さらにコア層を
ノンドープとするＰＩＮ構造を成し、さらにこのＰＩＮ
構造の上下に電極を有し、電極の面積が光導波部の面積
より大きいことを特徴とする。A nonlinear optical element of the present invention comprises a core layer made of a semiconductor material that causes a nonlinear refractive index change due to absorption of light, and a clad layer bonded to the core layer to guide light in a direction perpendicular to the layer. The PIN structure has a means for forming a wave structure and realizing an optical waveguide structure in a direction horizontal to the layer, and further forms a PIN structure in which the core layer is non-doped.
It is characterized in that electrodes are provided above and below the structure, and the area of the electrodes is larger than the area of the optical waveguide portion.
【０００７】[0007]
【実施例】図１に本発明の非線形光学素子の一実施例を
示す。本実施例ではＳｉを１０18ｃｍ-3ドーピングした
ＧａＡｓ基板２上に、Ｓｉを１０18ｃｍ-3ドーピングし
た厚さ２μｍのＡｌx Ｇａ1-x Ａｓ（ｘ＝０．０７）下
部クラッド層３、ノンドーピングで厚さ０．２μｍのＡ
ｌx Ｇａ1-x Ａｓ（ｘ＝０．０７）下部クラッド層４、
ノンドーピングで厚さ０．５μｍのＧａＡｓコア層５、
ノンドーピングで厚さ０．２μｍのＡｌx Ｇａ1-x Ａｓ
（ｘ＝０．０７）上部クラッド層６、Ｂｅを１０18ｃｍ
-3ドーピングした厚さ０．６μｍのＡｌx Ｇａ1-x Ａｓ
（ｘ＝０．０７）上部クラッド層７、Ｂｅを１０18ｃｍ
-3ドーピングした厚さ０．２μｍのＧａＡｓキャップ層
８が順に積層されている。さらに、エッチングプロセス
により高さ０．９μｍ，幅４μｍのストライプが形成さ
れている。素子表面にはＳｉＯ2 絶縁膜１０と電極１１
が積層され、電極１１はＧａＡｓキャップ層８にオーミ
ック接触している。また、基板２の裏面にもオーミック
電極１が形成されている。FIG. 1 shows one embodiment of the nonlinear optical element of the present invention. On the GaAs substrate 2 was 10 18 cm -3 Si-doped In this embodiment, a thickness of 2μm was 10 18 cm -3 doping Si Al x Ga 1-x As (x = 0.07) lower cladding layer 3 , Non-doped and 0.2 μm thick A
l x Ga 1-x As (x = 0.07) lower cladding layer 4,
Undoped GaAs core layer 5 having a thickness of 0.5 μm,
Undoped and 0.2 μm thick Al x Ga 1-x As
(X = 0.07) Upper cladding layer 6, Be 10 18 cm
-3 Doped Al x Ga 1-x As with a thickness of 0.6 μm
(X = 0.07) Upper clad layer 7, Be 10 18 cm
A −3 doped GaAs cap layer 8 having a thickness of 0.2 μm is sequentially stacked. Furthermore, stripes having a height of 0.9 μm and a width of 4 μm are formed by the etching process. A SiO 2 insulating film 10 and an electrode 11 are formed on the device surface.
Are stacked, and the electrode 11 is in ohmic contact with the GaAs cap layer 8. The ohmic electrode 1 is also formed on the back surface of the substrate 2.
【０００８】このように、本実施例の非線形光学素子
は、通常はキャパシタンスを最小限にするためにストラ
イプ上のみに形成される電極１１を、その他の部分にも
広げることにより、意図的にキャパシタンスを大きくし
ていることを特徴とする。発明が解決しようとする課題
で述べたように、静電界による光励起キャリアの掃引効
率を上げるためには、常に光導波部に高い静電界が印加
されていることが重要だが、以下の説明で明らかなよう
に、これは大面積電極１１がもたらす大きなキャパシタ
ンスにより達成される。As described above, in the nonlinear optical element of this embodiment, the electrode 11 which is normally formed only on the stripe in order to minimize the capacitance is intentionally expanded to other portions, so that the capacitance is intentionally increased. Is characterized by increasing. As described in the problem to be solved by the invention, it is important that a high electrostatic field is always applied to the optical waveguide in order to increase the sweep efficiency of the photoexcited carriers by the electrostatic field, but it is clear in the following description. As such, this is accomplished by the large capacitance provided by the large area electrode 11.
【０００９】図２に図１の実施例の電気的等価回路を示
す。ここで、Ｃpin は実施例のＰＩＮ構造のキャパシタ
ンス、Ｒは直列内部抵抗（小さいので無視できる）、Ｃ
s は浮遊溶量、Ｚは外部抵抗、ｖ0 ／ｓは光励起による
起電力を表す。ここでｖ0 ＝ｑ0 ／Ｃpin ，ｑ0 は光励
起されたキャリアの量である。キルヒホッフの法則によ
ると、FIG. 2 shows an electrical equivalent circuit of the embodiment shown in FIG. Here, C pin is the capacitance of the PIN structure of the embodiment, R is the series internal resistance (small and can be ignored), C
s is the amount of floating solution, Z is the external resistance, and v 0 / s is the electromotive force due to photoexcitation. Here, v 0 = q 0 / C pin , q 0 is the amount of photoexcited carriers. According to Kirchhoff's law,
【００１０】[0010]
【数１】 [Equation 1]
【００１１】となる。ｓはラプラス演算子である。ｉ1
およびｉ2 は図２に示すループ電流である。ここで
（１），（２）式より、ＰＩＮ構造に印加されている電
圧を求めると、[0011] s is a Laplace operator. i 1
And i 2 are the loop currents shown in FIG. Here, when the voltage applied to the PIN structure is obtained from the equations (1) and (2),
【００１２】[0012]
【数２】 [Equation 2]
【００１３】となる。（３）式は光励起されたキャリア
によるキャパシタンスＣpin 上にかかる電圧の変化を示
す。前記の如く、非線形導波路の高速化には、電圧変化
が少ない方が望ましいので、Δｖ（ｔ）→０の極限を求
めると、（Ｃpin ＋Ｃs ）→∞となる。すなわちＰＩＮ
構造のキャパシタンスは大きいほどよく、このために
は、電極の面積が大きいほどよい。[0013] Equation (3) shows the change in the voltage on the capacitance C pin due to photoexcited carriers. As described above, it is desirable that the voltage change is small in order to increase the speed of the nonlinear waveguide. Therefore, when the limit of Δv (t) → 0 is obtained, (C pin + C s ) → ∞. Ie PIN
The larger the capacitance of the structure, the better, and for this, the larger the area of the electrodes.
【００１４】以上、本発明の非線形光学素子について、
実施例による詳しい説明を行ったが、本発明は本実施例
に限定されるものではない。本実施例ではＧａＡｓ系の
材料を用いたが、これは光波長に応じて、他の材料、例
えばＩｎＰ，ＩｎＧａＡｓＰ等が用いられることは明ら
かである。また素子の構造に関しても、導波損失の低減
のためにコア層とクラッド層間にバッファ層を加える
と、種々の変形が考えられる。As described above, regarding the nonlinear optical element of the present invention,
Although the detailed description has been given with reference to the embodiments, the present invention is not limited to the embodiments. Although a GaAs-based material is used in this embodiment, it is obvious that other materials such as InP and InGaAsP may be used depending on the light wavelength. Regarding the structure of the element, various modifications can be considered if a buffer layer is added between the core layer and the clad layer in order to reduce the waveguide loss.
【００１５】[0015]
【発明の効果】以上説明したように、本発明の非線形光
学素子は、大きな素子容量を持つため、制御光吸収によ
る印加静電界の低下が抑制され、高速動作が可能であ
る。As described above, since the nonlinear optical element of the present invention has a large element capacitance, the decrease of the applied electrostatic field due to the absorption of the control light is suppressed and the high speed operation is possible.
【図１】本発明の非線形光学素子の一実施例を示す断面
図である。FIG. 1 is a sectional view showing an embodiment of a nonlinear optical element of the present invention.
【図２】図１の実施例の等価回路を示す図である。FIG. 2 is a diagram showing an equivalent circuit of the embodiment of FIG.
１ 電極 ２ ＳｉドープＧａＡｓ基板 ３ ＳｉドープＡｌＧａＡｓ下部クラッド層 ４ ノンドープＡｌＧａＡｓ下部クラッド層 ５ ノンドープＧａＡｓコア層 ６ ノンドープＡｌＧａＡｓ上部クラッド層 ７ ＢｅドープＡｌＧａＡｓ上部クラッド層 ８ ＢｅドープＧａＡｓキャップ層 １０ ＳｉＯ2 絶縁膜 １１ 電極 Ｃpin 非線形素子のＰＩＮ構造のキャパシタンス ｖ0 ／ｓ ステップ状に加えられた励起光による起電力 Ｒ 非線形素子のＰＩＮ構造の抵抗 Ｃs 浮遊および外部回路のキャパシタンス Ｚ 外部回路の抵抗1 electrode 2 Si-doped GaAs substrate 3 Si-doped AlGaAs lower cladding layer 4 Non-doped AlGaAs lower cladding layer 5 Non-doped GaAs core layer 6 Non-doped AlGaAs upper cladding layer 7 Be-doped AlGaAs upper cladding layer 8 Be-doped GaAs cap layer 10 SiO 2 insulating film 11 Electrode C pin Capacitance of PIN structure of non-linear element v 0 / s Electromotive force due to stepwise applied excitation light R Resistance of PIN structure of non-linear element C s Stray and external circuit capacitance Z External circuit resistance
Claims (3)
子において、 ノンドープのコア層と上部クラッド層と下部クラッド層
とからなるＰＩＮ構造を有し、上部電極の面積を光導波
部の面積よりも大きくして、ＰＩＮ構造のキャパシタン
スを大きくしたことを特徴とする非線形光学素子。1. A nonlinear optical element utilizing band filling, which has a PIN structure composed of a non-doped core layer, an upper clad layer and a lower clad layer, wherein the area of the upper electrode is larger than the area of the optical waveguide. And a PIN structure having a large capacitance.
導体材料からなるコア層とこのコア層に接合するクラッ
ド層とで層に垂直な方向に光導波構造を形成し、層に水
平な方向にも光導波構造を実現する手段を有し、さらに
前記コア層をノンドープとするＰＩＮ構造を成し、さら
にこのＰＩＮ構造の上下に電極を有する非線形光学素子
において、前記電極の面積が光導波部の面積より大きい
ことを特徴とする非線形光学素子。2. An optical waveguide structure is formed in a direction perpendicular to a layer by a core layer made of a semiconductor material that causes a nonlinear refractive index change by light absorption and a clad layer joined to the core layer, and the optical waveguide structure is formed in a direction horizontal to the layer. Also has a means for realizing an optical waveguide structure, further comprises a PIN structure in which the core layer is non-doped, and further, in a non-linear optical element having electrodes above and below the PIN structure, the area of the electrode is the optical waveguide portion. A non-linear optical element having a larger area.
静電界印加によるキャリア掃引を利用した高速の光−光
制御を行う非線形光学素子において、 大きな素子を保持するために、電極の面積を光導波部の
面積よりも大きくしたことを特徴とする非線形光学素
子。3. A nonlinear optical element for performing high-speed optical-optical control utilizing a band-filling effect due to absorption of control light and a carrier sweep due to application of an electrostatic field, in order to hold a large element, the area of an electrode is set to an optical waveguide section. A non-linear optical element characterized by being made larger than the area of.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4341863A JP2541089B2 (en) | 1992-12-22 | 1992-12-22 | Non-linear optical element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4341863A JP2541089B2 (en) | 1992-12-22 | 1992-12-22 | Non-linear optical element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06186602A true JPH06186602A (en) | 1994-07-08 |
| JP2541089B2 JP2541089B2 (en) | 1996-10-09 |
Family
ID=18349333
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4341863A Expired - Lifetime JP2541089B2 (en) | 1992-12-22 | 1992-12-22 | Non-linear optical element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2541089B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5557700A (en) * | 1994-06-14 | 1996-09-17 | Nec Corporation | Semiconductor optical device utilizing nonlinear optical effect |
| JP2012208413A (en) * | 2011-03-30 | 2012-10-25 | Anritsu Corp | Optical gate element |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03144613A (en) * | 1989-10-31 | 1991-06-20 | Oki Electric Ind Co Ltd | Waveguide type optical element |
| JPH04107428A (en) * | 1990-08-28 | 1992-04-08 | Fujikura Ltd | Substrate type optical switch |
-
1992
- 1992-12-22 JP JP4341863A patent/JP2541089B2/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03144613A (en) * | 1989-10-31 | 1991-06-20 | Oki Electric Ind Co Ltd | Waveguide type optical element |
| JPH04107428A (en) * | 1990-08-28 | 1992-04-08 | Fujikura Ltd | Substrate type optical switch |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5557700A (en) * | 1994-06-14 | 1996-09-17 | Nec Corporation | Semiconductor optical device utilizing nonlinear optical effect |
| JP2012208413A (en) * | 2011-03-30 | 2012-10-25 | Anritsu Corp | Optical gate element |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2541089B2 (en) | 1996-10-09 |
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