JPH06347839A - Optical control device - Google Patents
Optical control deviceInfo
- Publication number
- JPH06347839A JPH06347839A JP13636293A JP13636293A JPH06347839A JP H06347839 A JPH06347839 A JP H06347839A JP 13636293 A JP13636293 A JP 13636293A JP 13636293 A JP13636293 A JP 13636293A JP H06347839 A JPH06347839 A JP H06347839A
- Authority
- JP
- Japan
- Prior art keywords
- optical
- buffer layer
- control device
- substrate
- crystal substrate
- 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
- 230000003287 optical effect Effects 0.000 title claims abstract description 88
- 239000000758 substrate Substances 0.000 claims abstract description 29
- 239000013078 crystal Substances 0.000 claims abstract description 13
- 230000005693 optoelectronics Effects 0.000 claims abstract description 4
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 235000012239 silicon dioxide Nutrition 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 230000007774 longterm Effects 0.000 abstract 1
- 230000005684 electric field Effects 0.000 description 7
- 230000008859 change Effects 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 230000010287 polarization Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000031700 light absorption Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 230000001052 transient effect Effects 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 238000001552 radio frequency sputter deposition Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
Classifications
-
- 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
- G02F2203/00—Function characteristic
- G02F2203/21—Thermal instability, i.e. DC drift, of an optical modulator; Arrangements or methods for the reduction thereof
Landscapes
- Optical Integrated Circuits (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は光波の変調、光路切り換
えなどを行う光制御デバイスに関し、特に基板中に設け
た光導波路を用いて制御を行う導波路型の光制御デバイ
スに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical control device for modulating a light wave, switching an optical path, etc., and more particularly to a waveguide type optical control device for controlling using an optical waveguide provided in a substrate.
【０００２】[0002]
【従来の技術】光通信システムの実用化が進むにつれ、
さらに大容量や多機能を持つ高度のシステムが求められ
ており、より高度の光信号の発生や光伝送路の切り替
え、交換などの新たな機能の付加が必要とされている。
現在の実用システムでは光信号は直接半導体レーザや発
光ダイオードの注入電流を変調することによって得られ
ているが、直接変調では緩和振動などの効果のため１０
ＧＨｚ前後以上の高速変調が難しいこと、波長変動が発
生するためコヒーレント光伝送方式には適用が難しいな
どの欠点がある。これを解決する手段としては、外部変
調器を使用する方法があり、特に基板中に形成した光導
波路により構成した導波路型の光変調器は、小型、高効
率、高速という特徴がある。一方、光伝送路の切り替え
やネットワークの交換機能を得る手段としては光スイッ
チが使用される。現在実用されている光スイッチは、プ
リズム、ミラー、ファイバーなどを機械的に移動させる
ものであり、低速であること、信頼性が不十分であるこ
と、単体での寸法が大きくマトリクス化に不適であるこ
と等の欠点がある。2. Description of the Related Art As the practical use of optical communication systems progresses,
There is a demand for advanced systems with large capacity and multiple functions, and new functions such as generation of higher-level optical signals, switching of optical transmission lines, and replacement are required.
In the current practical system, the optical signal is obtained by directly modulating the injection current of the semiconductor laser or the light emitting diode. However, direct modulation causes an effect such as relaxation oscillation.
There are drawbacks such as difficulty in high-speed modulation of around GHz or more and difficulty in application to the coherent optical transmission system due to wavelength variation. As a means for solving this, there is a method of using an external modulator, and in particular, a waveguide type optical modulator constituted by an optical waveguide formed in a substrate is characterized by small size, high efficiency and high speed. On the other hand, an optical switch is used as a means for obtaining the function of switching the optical transmission line and the switching function of the network. Currently used optical switches mechanically move prisms, mirrors, fibers, etc., and are slow, unreliable, large in size as a single unit, and unsuitable for matrix formation. There are drawbacks such as being present.
【０００３】これを解決する手段として開発が進められ
ているものはやはり光導波路を用いた導波型の光スイッ
チであり、高速、多素子の集積化が可能、高信頼等の特
徴がある。特にニオブ酸リチウム（ＬｉＮｂＯ3 ）結晶
等の強誘電体材料を用いたものは、光吸収が小さく低損
失であること、大きな電気光学効果を有しているため高
効率である等の特徴があり、従来からも方向性結合器型
光変調器・スイッチ、全反射型光スイッチ、マッハツエ
ンダ型光変調器等の種々の方式の光制御素子が報告され
ている。What is being developed as a means for solving this is a waveguide type optical switch using an optical waveguide, which is characterized by high speed, multi-element integration and high reliability. In particular, a material using a ferroelectric material such as lithium niobate (LiNbO 3 ) crystal is characterized by low light absorption and low loss and high efficiency because it has a large electro-optical effect. Conventionally, various types of optical control elements such as a directional coupler type optical modulator / switch, a total reflection type optical switch and a Mach-Zehnder type optical modulator have been reported.
【０００４】図２（ａ），（ｂ）に、従来の光制御デバ
イスの一例として方向性結合器型光スイッチの平面図及
びａ−ａ′部分の断面図を示す。ニオブ酸リチウム結晶
基板１の上にチタン（Ｔｉ）を拡散して屈折率を基板よ
りも大きくして形成した帯状の光導波路２及び３が形成
されており、光導波路２及び３は基板の中央部で互いに
数μｍ程度まで近接し、方向性結合器４を形成してい
る。また、方向性結合器４を構成する光導波路上には電
極による光吸収を防ぐための光学的バッファ層６を介し
て制御電極５が形成されている。2A and 2B are a plan view and a sectional view taken along the line aa 'of a directional coupler type optical switch as an example of a conventional optical control device. Band-shaped optical waveguides 2 and 3 formed by diffusing titanium (Ti) to have a refractive index larger than that of the substrate are formed on a lithium niobate crystal substrate 1, and the optical waveguides 2 and 3 are formed at the center of the substrate. The parts are close to each other by about several μm to form the directional coupler 4. A control electrode 5 is formed on the optical waveguide forming the directional coupler 4 with an optical buffer layer 6 for preventing light absorption by the electrode.
【０００５】光導波路２に入射した入射光７は方向性結
合器４の部分を伝搬するにしたがって近接した光導波路
３へ徐々に光エネルギーが移り、方向性結合器４を通過
後は光導波路３にほぼ１００％エネルギーが移って出射
光８となる。一方、制御電極５に電圧を印加した場合、
電気光学効果により制御電極下の光導波路の屈折率が変
化し、光導波路２と３を伝搬する導波モードの間に位相
速度の不整合が生じ、両者の間の結合状態は変化する。
すなわち、制御電極５への制御電圧の有無によって、入
射光７は光導波路２からの出射光９または光導波路３か
らの出射光８となる。Incident light 7 that has entered the optical waveguide 2 gradually transfers optical energy to the adjacent optical waveguide 3 as it propagates through the directional coupler 4, and after passing through the directional coupler 4, the optical waveguide 3 Almost 100% of the energy is transferred to and becomes emitted light 8. On the other hand, when a voltage is applied to the control electrode 5,
Due to the electro-optic effect, the refractive index of the optical waveguide under the control electrode changes, a phase velocity mismatch occurs between the waveguide modes propagating in the optical waveguides 2 and 3, and the coupling state between the two changes.
That is, the incident light 7 becomes the emitted light 9 from the optical waveguide 2 or the emitted light 8 from the optical waveguide 3 depending on the presence or absence of the control voltage to the control electrode 5.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、図２に
示すような従来の光スイッチでは、ＤＣ電圧印加により
光学的バッファ層６中の電荷が局部的に蓄積されて光波
に作用する電界強度が変化する現象即ちＤＣドリフトが
生じやすく、デバイスの安定性に問題があった。However, in the conventional optical switch as shown in FIG. 2, charges in the optical buffer layer 6 are locally accumulated by applying a DC voltage, and the electric field strength acting on the light wave changes. There is a problem in the stability of the device because the phenomenon that occurs, that is, DC drift is likely to occur.
【０００７】本発明の目的は、上述の従来の光制御デバ
イスの問題点を解決し、特性が長期に渡って安定な光制
御デバイスを提供することにある。An object of the present invention is to solve the above-mentioned problems of the conventional light control device and to provide a light control device whose characteristics are stable over a long period of time.
【０００８】[0008]
【課題を解決するための手段】本発明は、電気光学効果
を有する誘電体結晶基板中に設置された光導波路と、そ
の光導波路を含む基板上に設置された光学的バッファ層
と、光導波路近傍の光学的バッファ層上に設置された制
御用電極とからなる導波路型光制御デバイスにおいて、
前記光学的バッファ層の直流の抵抗率と誘電率の積が、
前記誘電体結晶基板の直流の抵抗率と誘電率の積に比べ
て小さいことを特徴とする。DISCLOSURE OF THE INVENTION The present invention provides an optical waveguide provided in a dielectric crystal substrate having an electro-optical effect, an optical buffer layer provided on the substrate including the optical waveguide, and an optical waveguide. In a waveguide type optical control device comprising a control electrode provided on a nearby optical buffer layer,
The product of the direct current resistivity and the dielectric constant of the optical buffer layer is
It is characterized by being smaller than the product of the direct current resistivity and the dielectric constant of the dielectric crystal substrate.
【０００９】[0009]
【作用】発明が解決しようとする課題の項で述べたＤＣ
ドリフト現象は、誘電体結晶基板と光学的バッファ層の
電気的定数が異なることに起因する電界の過渡的な変
化、および光学的バッファ層中の不純物イオンの分極が
主な原因である、通常、外部からの電界に対して、光導
波路部分の電界を弱めるような変化を正のＤＣドリフ
ト、強めるような変化を負のＤＣドリフトと呼ぶ。発明
者らのシミュレーションによると、基板と光学的バッフ
ァ層の電気的定数が異なることに起因する電界の過渡的
応答変化量は、基板の直流の抵抗率と誘電率の積（以
下、直流の抵抗率と誘電率の積を時定数と呼ぶ）と光学
的バッファ層の時定数の差に依存し、光学的バッファ層
の時定数が基板の時定数に比べて小さいほどＤＣドリフ
トは小さく、または負になる。一方、光学的バッファ層
中の不純物イオンの分極による電界の変化は正のＤＣド
リフトとなるので、基板とバッファ層の時定数の差に起
因する負のＤＣドリフトにより、不純物イオンの分極に
よる正のＤＣドリフトを打ち消すことができる。また、
不純物イオンによるＤＣドリフトが小さく上記２つのＤ
Ｃドリフトの和が負になる場合にも、負のＤＣドリフト
に対しては印加ＤＣ電圧を弱くすることで対応可能なの
で、問題にはならない。従って本発明により、安定な光
制御デバイスが得られる。The DC described in the section of the problem to be solved by the invention
The drift phenomenon is mainly caused by the transient change of the electric field due to the different electric constants of the dielectric crystal substrate and the optical buffer layer, and the polarization of impurity ions in the optical buffer layer. A change that weakens the electric field in the optical waveguide portion with respect to an external electric field is called a positive DC drift, and a change that strengthens the electric field is called a negative DC drift. According to the simulations by the inventors, the transient response change amount of the electric field due to the difference between the electric constants of the substrate and the optical buffer layer is the product of the direct current resistivity and the dielectric constant of the substrate (hereinafter referred to as the direct current resistance). The product of the dielectric constant and the permittivity is called the time constant) and the time constant of the optical buffer layer, and the smaller the time constant of the optical buffer layer is than the time constant of the substrate, the smaller the DC drift or the negative. become. On the other hand, the change in the electric field due to the polarization of the impurity ions in the optical buffer layer results in a positive DC drift, so that the negative DC drift resulting from the difference in the time constant between the substrate and the buffer layer causes the positive DC drift due to the polarization of the impurity ions. DC drift can be canceled. Also,
DC drift due to impurity ions is small and the above two D
Even if the sum of the C drifts becomes negative, it is possible to deal with the negative DC drift by weakening the applied DC voltage, so there is no problem. Therefore, the present invention provides a stable light control device.
【００１０】[0010]
【実施例】図１（ａ），（ｂ）は、本発明による光制御
デバイスの一実施例である方向性結合器型光スイッチの
平面図及びａ−ａ′部分の断面図である。1 (a) and 1 (b) are a plan view and a sectional view taken along the line aa 'of a directional coupler type optical switch which is an embodiment of an optical control device according to the present invention.
【００１１】ニオブ酸リチウム（ＬｉＮｂＯ3 ）結晶基
板１の上にチタンを９００〜１１００℃程度で数時間熱
拡散して形成された３〜１０μｍ程度の光導波路２及び
３が形成されており、基板の中央部で両光導波路は互い
に数μｍまで近接して方向性結合器４を構成している。
その上に光学的バッファ層６を介して制御電極５が形成
されている。光学的バッファ層６の時定数は基板１の時
定数に比べて小さくなるようにする。例えば基板１がニ
オブ酸リチウムの場合、前述の拡散プロセスの雰囲気を
ドライ酸素で行うと、基板の抵抗率は２５℃で２×１０
19（Ωｃｍ）程度になる。一方、光学的バッファ層６が
ＲＦスパッタ成膜の二酸化シリコン（ＳｉＯ2 ）の場
合、入射電力を２ｋＷとし、成膜後ドライ酸素中でアニ
ールすると、光学的バッファ層の抵抗率は２５℃で８×
１０18（Ωｃｍ）程度になる。ニオブ酸リチウム及び二
酸化シリコンの比誘電率はそれぞれ約２８と４であるか
ら、上記の場合、基板１及び光学的バッファ層６の時定
数はそれぞれ約１．２×１０4 時間及び７５０時間とな
り、光学的バッファ層の時定数が基板の時定数より小さ
くなるので本発明の条件を満足する。このようにして作
製された光スイッチは、作用の項で述べたように、基板
１と光学的バッファ層６の時定数の差に起因するＤＣド
リフトが負になるので、光学的バッファ層中の不純物イ
オンの分極に起因するＤＣドリフトを打ち消し、ＤＣド
リフトの小さい安定な動作が得られる。On a lithium niobate (LiNbO 3 ) crystal substrate 1, optical waveguides 2 and 3 of about 3 to 10 μm formed by thermally diffusing titanium at 900 to 1100 ° C. for several hours are formed. At the center of the two optical waveguides, the optical waveguides are close to each other by several μm to form the directional coupler 4.
A control electrode 5 is formed on top of this via an optical buffer layer 6. The time constant of the optical buffer layer 6 is made smaller than that of the substrate 1. For example, when the substrate 1 is lithium niobate and the atmosphere of the diffusion process is dry oxygen, the substrate resistivity is 2 × 10 5 at 25 ° C.
It will be about 19 (Ωcm). On the other hand, when the optical buffer layer 6 is a silicon dioxide (SiO 2 ) film formed by RF sputtering, the incident power is set to 2 kW, and the film is annealed in dry oxygen after the film formation, the resistivity of the optical buffer layer is 8 at 25 ° C. ×
It becomes about 10 18 (Ωcm). Since the relative permittivities of lithium niobate and silicon dioxide are about 28 and 4, respectively, in the above case, the time constants of the substrate 1 and the optical buffer layer 6 are about 1.2 × 10 4 hours and 750 hours, respectively. The condition of the present invention is satisfied because the time constant of the optical buffer layer is smaller than that of the substrate. In the optical switch manufactured in this manner, the DC drift due to the difference in the time constant between the substrate 1 and the optical buffer layer 6 becomes negative, as described in the section of the action, so that the optical switch in the optical buffer layer has a negative DC drift. DC drift caused by polarization of impurity ions is canceled, and stable operation with small DC drift can be obtained.
【００１２】[0012]
【発明の効果】以上述べたように、本発明ではＤＣドリ
フトを小さくできるので、従来の光制御デバイスに比
べ、特性の安定した光制御デバイスが得られる。As described above, in the present invention, the DC drift can be reduced, so that an optical control device having stable characteristics can be obtained as compared with the conventional optical control device.
【図１】本発明による光制御デバイスの一例を示す平面
図および断面図である。FIG. 1 is a plan view and a cross-sectional view showing an example of a light control device according to the present invention.
【図２】従来例による光制御デバイスの一例を示す平面
図および断面図である。FIG. 2 is a plan view and a cross-sectional view showing an example of a conventional light control device.
１ ニオブ酸リチウム結晶基板 ２，３ 光導波路 ４ 方向性結合器 ５ 制御電極 ６ バッファ層 ７ 入射光 ８，９ 出射光 1 Lithium niobate crystal substrate 2, 3 Optical waveguide 4 Directional coupler 5 Control electrode 6 Buffer layer 7 Incident light 8, 9 Emission light
Claims (3)
設置された光導波路と、その光導波路を含む基板上に設
置された光学的バッファ層と、光導波路近傍の光学的バ
ッファ層上に設置された制御用電極とからなる導波路型
光制御デバイスにおいて、 前記光学的バッファ層の直流の抵抗率と誘電率の積が、
前記誘電体結晶基板の直流の抵抗率と誘電率の積に比べ
て小さいことを特徴とする光制御デバイス。1. An optical waveguide provided in a dielectric crystal substrate having an electro-optical effect, an optical buffer layer provided on a substrate including the optical waveguide, and an optical buffer layer near the optical waveguide. In a waveguide type optical control device comprising an installed control electrode, the product of the direct current resistivity and the dielectric constant of the optical buffer layer is:
An optical control device, which is smaller than a product of a direct current resistivity and a dielectric constant of the dielectric crystal substrate.
結晶基板であり、 前記バッファ層は、二酸化シリコンである、ことを特徴
とする請求項１記載の光制御デバイス。2. The light control device according to claim 1, wherein the dielectric crystal substrate is a lithium niobate crystal substrate, and the buffer layer is silicon dioxide.
合器を構成することを特徴とする請求項１または２記載
の光制御デバイス。3. The light control device according to claim 1, wherein the optical waveguide constitutes a directional coupler having a proximity portion.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13636293A JPH06347839A (en) | 1993-06-08 | 1993-06-08 | Optical control device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13636293A JPH06347839A (en) | 1993-06-08 | 1993-06-08 | Optical control device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06347839A true JPH06347839A (en) | 1994-12-22 |
Family
ID=15173402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13636293A Pending JPH06347839A (en) | 1993-06-08 | 1993-06-08 | Optical control device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06347839A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07128624A (en) * | 1993-11-01 | 1995-05-19 | Sumitomo Osaka Cement Co Ltd | Production of waveguide optical element |
| JP2013190723A (en) * | 2012-03-15 | 2013-09-26 | Ricoh Co Ltd | Electro-optical element, method of manufacturing the same, and electro-optical device |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04346310A (en) * | 1991-05-23 | 1992-12-02 | Nippon Telegr & Teleph Corp <Ntt> | light control device |
-
1993
- 1993-06-08 JP JP13636293A patent/JPH06347839A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04346310A (en) * | 1991-05-23 | 1992-12-02 | Nippon Telegr & Teleph Corp <Ntt> | light control device |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07128624A (en) * | 1993-11-01 | 1995-05-19 | Sumitomo Osaka Cement Co Ltd | Production of waveguide optical element |
| JP2013190723A (en) * | 2012-03-15 | 2013-09-26 | Ricoh Co Ltd | Electro-optical element, method of manufacturing the same, and electro-optical device |
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