JP2621313B2 - Optical switch / modulator - Google Patents

Optical switch / modulator

Info

Publication number
JP2621313B2
JP2621313B2 JP6646088A JP6646088A JP2621313B2 JP 2621313 B2 JP2621313 B2 JP 2621313B2 JP 6646088 A JP6646088 A JP 6646088A JP 6646088 A JP6646088 A JP 6646088A JP 2621313 B2 JP2621313 B2 JP 2621313B2
Authority
JP
Japan
Prior art keywords
optical
modulator
electrode
optical switch
passivation film
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.)
Expired - Lifetime
Application number
JP6646088A
Other languages
Japanese (ja)
Other versions
JPH01238623A (en
Inventor
裕 西本
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
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Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP6646088A priority Critical patent/JP2621313B2/en
Publication of JPH01238623A publication Critical patent/JPH01238623A/en
Application granted granted Critical
Publication of JP2621313B2 publication Critical patent/JP2621313B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • 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
    • G02F1/29—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 position or the direction of light beams, i.e. deflection
    • G02F1/31—Digital deflection, i.e. optical switching
    • G02F1/313—Digital deflection, i.e. optical switching in an optical waveguide structure
    • G02F1/3132—Digital deflection, i.e. optical switching in an optical waveguide structure of directional coupler type

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Integrated Circuits (AREA)

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は方向性結合器を用いた導波型の光スイッチ・
変調器に関するものである。The present invention relates to a waveguide type optical switch using a directional coupler.
It relates to a modulator.

〔従来の技術〕[Conventional technology]

基板に形成された互いに近接した２本の光導波路で構
成した光方向性結合器からなる導波型光スイッチ・変調
器は光交換機及び光通信ネークワークにおける伝送路切
替器、外部変調器などへの応用がある。この光方向性結
合器からなる導波型光スイッチ・変調器において、光路
をスイッチまたは光を変調するための制御信号が印加さ
れる制御電極（今後電極と呼ぶ）は、通常光方向性結合
器を構成する光導波路上に設置される。電極材料は金属
及び導電性のある透明材料を用いる。電極材料として金
属を用いるもの（以後金属電極と呼ぶ）は、光スイッチ
・変調器を電界成分が基板に垂直な偏光モード（TMモー
ド）で動作させる場合、金属による光の吸収を防ぐため
に、光導波路と金属電極の間に基板より屈折率が低く、
かつ光の吸収が少ない光学的なバッファ層を施す。この
バッファ層はSiO2,Si3N4,SiONx,Al2O3などが用いらえ
る。一方、導電性がある透明材料を用いた電極（以後透
明電極と呼ぶ）はその屈折率が低ければ、前記バッファ
層は必要とせず電極を光導波路上に直接形成することが
できる。透明材料にはITOがある。A waveguide type optical switch / modulator composed of an optical directional coupler composed of two optical waveguides close to each other formed on a substrate is used for a transmission line switch, an external modulator, etc. in an optical exchange and an optical communication network. There are applications. In a waveguide type optical switch / modulator composed of this optical directional coupler, a control electrode (hereinafter referred to as an electrode) to which a control signal for switching an optical path or modulating light is applied is usually an optical directional coupler. Is installed on the optical waveguide that constitutes. As the electrode material, a metal and a conductive transparent material are used. In the case where a metal is used as the electrode material (hereinafter referred to as a metal electrode), when the optical switch / modulator is operated in a polarization mode (TM mode) in which the electric field component is perpendicular to the substrate, an optical waveguide is required to prevent absorption of light by the metal. The refractive index is lower than the substrate between the waveguide and the metal electrode,
An optical buffer layer that absorbs less light is provided. For this buffer layer, SiO 2 , Si 3 N 4 , SiONx, Al 2 O 3 or the like can be used. On the other hand, if an electrode using a transparent material having conductivity (hereinafter referred to as a transparent electrode) has a low refractive index, the electrode can be formed directly on the optical waveguide without the need for the buffer layer. The transparent material is ITO.

金属電極及び透明電極はその動作中，湿気，ホコリ，
温度変化などの外部環境の影響により電極自体の破壊や
劣化などが生じ、光スイッチ・変調器の動作不良が発生
するため電極を外部環境から保護するために電極を覆う
パッシベーション膜を施す場合がある。これらの電極の
構造を第３図及び第４図を参照して説明する。During operation, the metal electrode and the transparent electrode are subject to moisture, dust,
Due to the effects of the external environment such as temperature changes, the electrodes themselves may be destroyed or deteriorated, causing malfunctions of the optical switch or modulator.Therefore, a passivation film covering the electrodes may be applied to protect the electrodes from the external environment. . The structure of these electrodes will be described with reference to FIG. 3 and FIG.

第３図（ａ），（ｂ）は、光方向性結合器４から成る
光スイッチ・変調器において金属電極６を用いた構造の
断面図であり、金属電極６と光方向性結合器４の間にバ
ッファ層５が設けてある。第３図（ａ）はバッファ層５
をLiNb3基板１の全面に施した場合であり、第３図
（ｂ）はバッファ層５を金属電極６の領域のみに施した
場合である。3 (a) and 3 (b) are cross-sectional views of a structure using the metal electrode 6 in the optical switch / modulator including the optical directional coupler 4, and FIG. The buffer layer 5 is provided between them. FIG. 3A shows the buffer layer 5.
Is applied to the entire surface of the LiNb 3 substrate 1, and FIG. 3B shows the case where the buffer layer 5 is applied only to the region of the metal electrode 6.

第４図は、光方向性結合器４から成る光スイッチ・変
調器において透明電極７を用いた構造の断面図である。
第３図，第４図のそれぞれの電極はパッシベーション膜
８で覆われている。FIG. 4 is a sectional view of a structure using a transparent electrode 7 in the optical switch / modulator including the optical directional coupler 4.
Each of the electrodes in FIGS. 3 and 4 is covered with a passivation film 8.

第３図（ｂ）において、バッファ層５を金属電極６の
領域のみに施すのは金属電極６に直流電圧バイアスを印
加した場合にスイッチング電圧のシフト（今後DCドリフ
トと呼ぶ）が生じるのを低減させるためである。すなわ
ち、前記DCドリフトの主要因は、金属電極６に直流電圧
バイアスを印加した場合のバッファ層５内の正負イオン
の移動によるものであり、第３図（ａ）の構造では前記
正負イオンの移動が顕著に現われるのに対し、第３図
（ｂ）では１対の金属電極６の間の前記正負イオンの移
動はなく、LiNbO3基板１と金属電極６の間の前記正負イ
オンの移動のみに抑えられるため、DCドリフトは低減さ
れる。一方、第４図に示す透明電極７を用いた構造では
DCドリフトの主要因であるバッファ層が不要なためDCド
リフトは回避される。これらの電極構造において、電極
6,7はその動作中湿気，ホコリ，温度変化などの外部環
境の影響により電極自体の破壊や劣化などが生じ、光ス
イッチ・変調器の動作不良が発生する。このため電極6,
7を外部環境から保護するため電極を覆うパッシベーシ
ョン膜８を施すことがある。パッシベーション膜８に望
まれることは、第一にパッシベーション膜８自体が極め
て低い不純物濃度をもつこと、すなわち、不純物濃度が
高ければ前記DCドリフトの発生を促進してしまう。第二
にパッシベーション膜８自体の絶縁破壊電圧が高いこ
と、すなわち、第３図，第４図における金属電極6,透明
電極７それぞれにおいて、一対の電極6,7の間の距離、
すなわち、光方向性結合器４の２本の導波路の間隔数μ
ｍに対して直流電圧バイアス100V近くを必要とすると
き、絶縁破壊電圧が低いと電極自体が絶縁破壊を発生す
る。In FIG. 3B, applying the buffer layer 5 only to the region of the metal electrode 6 reduces the occurrence of switching voltage shift (hereinafter referred to as DC drift) when a DC voltage bias is applied to the metal electrode 6. It is to make it. That is, the main cause of the DC drift is due to the movement of the positive and negative ions in the buffer layer 5 when a DC voltage bias is applied to the metal electrode 6, and in the structure of FIG. 3B, the positive and negative ions do not move between the pair of metal electrodes 6 but only the positive and negative ions move between the LiNbO 3 substrate 1 and the metal electrode 6. Because it is suppressed, DC drift is reduced. On the other hand, in the structure using the transparent electrode 7 shown in FIG.
DC drift is avoided because a buffer layer, which is a main cause of DC drift, is not required. In these electrode structures, the electrode
In the devices 6 and 7, the electrodes themselves are destroyed or deteriorated due to the influence of the external environment such as humidity, dust and temperature change during operation, resulting in malfunction of the optical switch / modulator. Therefore, the electrode 6,
A passivation film 8 covering the electrodes may be applied to protect 7 from the external environment. What is desired for the passivation film 8 is that the passivation film 8 itself has an extremely low impurity concentration, that is, if the impurity concentration is high, the occurrence of the DC drift is promoted. Second, the dielectric breakdown voltage of the passivation film 8 itself is high, that is, the distance between the pair of electrodes 6 and 7 in each of the metal electrode 6 and the transparent electrode 7 in FIGS.
That is, the interval μ between the two waveguides of the optical directional coupler 4.
When a DC voltage bias of about 100 V is required for m, if the dielectric breakdown voltage is low, the electrode itself will cause dielectric breakdown.

〔発明が解決しようとする課題〕 前述した様に、パッシベーション膜を適用した従来の
光スイッチ・変調器では、パッシベーション膜の特性に
よりDCドリフト、電極寿命が決定されるため、常に高い
信頼性を得るのは困難である。[Problems to be Solved by the Invention] As described above, in a conventional optical switch / modulator to which a passivation film is applied, DC drift and electrode life are determined by the characteristics of the passivation film, so that high reliability is always obtained. It is difficult.

本発明の目的は、高信頼の光スイッチ・変調器を与え
ることにある。It is an object of the present invention to provide a highly reliable optical switch / modulator.

〔課題を解決するための手段〕[Means for solving the problem]

本発明は、基板に形成された互いに近接した２本の光
導波路からなる光方向性結合器と、前記２本の光導波路
上にそれぞれ形成された制御電極とそれを覆うパッシベ
ーション膜からなる光スイッチ・変調器において、すく
なくとも前記近接した２本の光導波路の間の領域が前記
近接した２本の光導波路の間の領域が前記近接した２本
の光導波路表面より凸部にせしめ、かつ、前記パッシベ
ーション膜を前記凸部を介して分断せしめたことを特徴
とする。The present invention relates to an optical directional coupler formed on a substrate and comprising two optical waveguides close to each other, an optical switch comprising a control electrode formed on each of the two optical waveguides and a passivation film covering the control electrode. In the modulator, at least the area between the two adjacent optical waveguides is such that the area between the two adjacent optical waveguides is more convex than the surfaces of the two adjacent optical waveguides, and It is characterized in that the passivation film is divided via the projection.

〔実施例〕〔Example〕

次に本発明について図面を参照して説明する。 Next, the present invention will be described with reference to the drawings.

第１図（ａ），（ｂ）は本発明の一実施例に係る方向
性結合器を用いた光スイッチ・変調器の断面図であり、
LiNbO3基板１を用い、電極形成領域以外をすべてLiNbO3
凸部とした場合、すなわちLiNbO3基板に溝を形成し、そ
の中に電極を形成した構造を示している。光方向性結合
器４を構成する光導波路はTiを熱拡散して形成した。Li
NbO3基板自体の絶縁破壊電圧はおよそ100V/μｍである
ため、電極間の絶縁層として優れた特性をもつ。例えば
電極間の距離Ｗを５μｍとすると、この時の絶縁破壊電
圧は数百Ｖ以上となる。この値は、光スイッチ・変調器
にとって実用上充分である。FIGS. 1A and 1B are cross-sectional views of an optical switch / modulator using a directional coupler according to an embodiment of the present invention.
Using LiNbO 3 substrate 1, all but the electrode formation region LiNbO 3
In the case of a convex portion, that is, a structure in which a groove is formed in a LiNbO 3 substrate and an electrode is formed therein is shown. The optical waveguide constituting the optical directional coupler 4 was formed by thermally diffusing Ti. Li
Since the NbO 3 substrate itself has a dielectric breakdown voltage of about 100 V / μm, it has excellent characteristics as an insulating layer between electrodes. For example, if the distance W between the electrodes is 5 μm, the dielectric breakdown voltage at this time is several hundred V or more. This value is practically sufficient for an optical switch / modulator.

第１図（ａ）はLiNbO3凸部３と電極２とが互いに接触
した場合であり、第１図（ｂ）はLiNbO3凸部３と電極２
が互いに接触しないように形成した場合であり光スイッ
チ・変調器の構成上どちらでも良いが、光スイッチング
電圧，変調電圧の点からは第１図（ｂ）の方が良い。す
なわち、誘電率の高いLiNbO3基板１に接触しない方が電
界の有効利用ができるためである。Figure 1 (a) shows a case where the LiNbO 3 the projections 3 and the electrode 2 in contact with each other, FIG. 1 (b) is LiNbO 3 projections 3 and the electrode 2
Are formed so as not to be in contact with each other, and either may be used in terms of the configuration of the optical switch / modulator, but FIG. 1B is better in terms of the optical switching voltage and the modulation voltage. That is, it is because the electric field can be used more effectively when it is not in contact with the LiNbO 3 substrate 1 having a high dielectric constant.

第１図（ａ），（ｂ）に示す様に、LiNbO3凸部３でパ
ッシベーション膜８を分断すると、パッシベーション膜
の不純物濃度によらず、電圧印加時に電極間の正負イオ
ンの移動はLiNbO3凸部３で遮断されるためDCドリフトは
発生しない。また、パッシベーション膜８の絶縁破壊電
圧の大きさによらず電極はLiNbO3凸部で絶縁されている
ため常に安定な動作を得る。つまり、パッシベーション
膜８は湿気，ホコリなどの外部環境から電極を保護する
ためのものであり、DCドリフト，電極の絶縁破壊には何
らの悪影響を与えず、DCドリフト電極の絶縁破壊防止の
ためには常に基板の一部であるLiNbO3凸部３が寄与す
る。つまり、本構造をとればパッシベーション膜の特性
によらずDCドリフト及び電極の絶縁破壊のない極めて高
い信頼性を持つ光スイッチ・変調器を得ることができ
る。1 (a), as shown in (b), when dividing the passivation film 8 in LiNbO 3 protrusions 3, regardless of the impurity concentration of the passivation film, the movement of the positive and negative ions between the electrodes when a voltage is applied LiNbO 3 DC drift does not occur because it is cut off by the projection 3. Further, regardless of the magnitude of the dielectric breakdown voltage of the passivation film 8, the electrode is insulated by the LiNbO 3 projection, so that a stable operation is always obtained. That is, the passivation film 8 is for protecting the electrode from the external environment such as moisture and dust, does not have any adverse effect on DC drift and dielectric breakdown of the electrode, and is intended to prevent dielectric breakdown of the DC drift electrode. Is always contributed by the LiNbO 3 projections 3 which are part of the substrate. In other words, with this structure, it is possible to obtain an optical switch / modulator having extremely high reliability without DC drift and electrode breakdown regardless of the characteristics of the passivation film.

第２図（ａ），（ｂ）は本発明のもう１つの実施例に
係る方向性結合器を用いた光スイッチ・変調器の断面図
であり、電極の間の領域のみをLiNbO3凸部とした場合を
示している。原理及び効果は第１図で説明したものと同
じであり、第２図（ａ）（ｂ）のそれぞれの違いも第１
図（ａ）（ｂ）の違いと同じである。Figure 2 (a), (b) is a sectional view of an optical switch modulator using a directional coupler according to another embodiment of the present invention, LiNbO 3 protrusions only the region between the electrodes Is shown. The principle and effects are the same as those described with reference to FIG. 1, and the differences between FIGS.
This is the same as the difference between FIGS.

以上説明したように本発明による構造を用いれば、光
スイッチ・変調器は外部環境の影響や通常用いられる印
加電圧の大きさによらず、かつパッシベーション膜の特
性にかかわらず、DCドリフト，電極破壊等の光スイッチ
・変調器の動作不良を起こすことなく、常に安定した動
作を行なえる極めて高信頼な光スイッチ・変調器を得る
ことができる。As described above, when the structure according to the present invention is used, the optical switch / modulator can be subjected to DC drift and electrode breakdown regardless of the influence of the external environment, the magnitude of the applied voltage normally used, and the characteristics of the passivation film. It is possible to obtain an extremely reliable optical switch / modulator that can always perform a stable operation without causing a malfunction of the optical switch / modulator.

また、本発明の構造において、電極はバッファ層を用
いる金属電極また透明電極どちらでも同一の効果が得ら
れるのは明らかであり、導電性高分子を用いた電極でも
よく、限定されるものではない。Also, in the structure of the present invention, it is clear that the same effect can be obtained with either a metal electrode using a buffer layer or a transparent electrode, and the electrode may be an electrode using a conductive polymer, and is not limited. .

光導波路はTi拡散によらず、LiNbO3基板を安息香酸や
ピロ燐酸等に加熱浸漬してプトロン交換により形成する
等どのような方法で形成してもよい。また基板はLiNbO3
に限らず半導体を用いてもよい。半導体基板を用いた場
合、光導波路は不純物拡散，埋め込み構造，超格子構造
等最も適当と思われるものを用いればよい。The optical waveguide may be formed by any method such as forming the LiNbO 3 substrate by heating and immersing it in benzoic acid, pyrophosphoric acid, or the like, and exchanging it by proton without using Ti diffusion. The substrate is LiNbO 3
The invention is not limited to this, and a semiconductor may be used. When a semiconductor substrate is used, the most suitable optical waveguide such as an impurity diffusion, a buried structure, and a superlattice structure may be used.

凸部は基板をエッチングして形成する以外、平坦な基
板面に絶縁破壊電圧の高い誘電体等を堆積して形成した
構造としてもよい。The projection may be formed by depositing a dielectric or the like having a high dielectric breakdown voltage on a flat substrate surface, instead of forming the projection by etching the substrate.

〔発明の効果〕〔The invention's effect〕

以上説明したように、本発明によれば基板に形成した
光方向性結合器を用いた光スイッチ・変調器において、
すくなくとも光方向性結合器を形成する近接した２本の
光導波路上にそれぞれ設置された制御電極の間すなわ
ち、近接した２本の光導波路の間の領域がその光導波路
表面より凸状態にし、かつ凸状態にした部位でパッシベ
ーション膜を分断させることにより、外部環境の影響や
通常用いられる印加電圧の大きさによらず、かつ、パッ
シベーション膜の特性にかかわらずDCドリフト，電極破
壊等の光スイッチ・変調器の動作不良を起こすことな
く、常に安定した動作を行なえる極めて高信頼な光スイ
ッチ・変調器を得ることができる。As described above, according to the present invention, in an optical switch / modulator using an optical directional coupler formed on a substrate,
At least a region between the control electrodes provided on the two adjacent optical waveguides forming the optical directional coupler, that is, a region between the two adjacent optical waveguides is made convex from the surface of the optical waveguide, and By dividing the passivation film at the protruded part, optical switches such as DC drift and electrode destruction do not depend on the influence of the external environment or the magnitude of the applied voltage normally used, and regardless of the characteristics of the passivation film. An extremely reliable optical switch / modulator that can always perform a stable operation without causing a malfunction of the modulator can be obtained.

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

第１図（ａ），（ｂ）、第２図（ａ），（ｂ）は本発明
の一実施例の光スイッチ・変調器の断面図、第３図
（ａ），（ｂ）第４図は従来例の光スイッチ・変調器に
おける光スイッチ・変調器の断面図である。 １……LiNbO3基板、２……制御電極、３……LiNbO3凸
部、４……光方向性結合器、５……バッファ層、６……
金属電極、７……透明電極、８……パッシベーション
膜。FIGS. 1 (a) and (b), FIGS. 2 (a) and (b) are cross-sectional views of an optical switch / modulator according to an embodiment of the present invention, and FIGS. FIG. 1 is a sectional view of an optical switch / modulator in a conventional optical switch / modulator. 1 ...... LiNbO 3 substrate, 2 ...... control electrode, 3 ...... LiNbO 3 protrusions, 4 ...... light directional coupler, 5 ...... buffer layer, 6 ......
Metal electrode, 7: Transparent electrode, 8: Passivation film.

Claims (1)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】基板に形成された互いに近接した２本の光
導波路からなる光方向性結合器と、前記２本の光導波路
上にそれぞれ形成された制御電極と、前記制御電極を覆
うパッシベーション膜からなる光スイッチ・変調器にお
いて、すくなくとも前記近接した２本の光導波路の間の
領域が前記近接した２本の光導波路表面より凸部にせし
め、かつ、前記パッシベーション膜を前記凸部を介して
分断せしめたことを特徴とする光スイッチ・変調器。An optical directional coupler comprising two optical waveguides formed on a substrate and disposed adjacent to each other, a control electrode formed on each of the two optical waveguides, and a passivation film covering the control electrode. In the optical switch / modulator, the area between at least the two adjacent optical waveguides is made to be more convex than the surfaces of the two optical waveguides adjacent to each other, and the passivation film is interposed through the convex. An optical switch / modulator characterized by being divided.
JP6646088A 1988-03-18 1988-03-18 Optical switch / modulator Expired - Lifetime JP2621313B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP6646088A JP2621313B2 (en) 1988-03-18 1988-03-18 Optical switch / modulator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP6646088A JP2621313B2 (en) 1988-03-18 1988-03-18 Optical switch / modulator

Publications (2)

Publication Number Publication Date
JPH01238623A JPH01238623A (en) 1989-09-22
JP2621313B2 true JP2621313B2 (en) 1997-06-18

Family

ID=13316404

Family Applications (1)

Application Number Title Priority Date Filing Date
JP6646088A Expired - Lifetime JP2621313B2 (en) 1988-03-18 1988-03-18 Optical switch / modulator

Country Status (1)

Country Link
JP (1) JP2621313B2 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0727131B2 (en) * 1990-08-24 1995-03-29 日本航空電子工業株式会社 Optical waveguide modulator
JP3362105B2 (en) * 1997-03-31 2003-01-07 住友大阪セメント株式会社 Waveguide type optical modulator
KR100330095B1 (en) * 1998-06-22 2003-01-15 삼성전자 주식회사 Vertically oriented twisted nematic liquid crystal display
JP2008046573A (en) 2006-08-21 2008-02-28 Fujitsu Ltd Optical modulator

Also Published As

Publication number Publication date
JPH01238623A (en) 1989-09-22

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