JP2635986B2 - Optical waveguide switch - Google Patents
Optical waveguide switchInfo
- Publication number
- JP2635986B2 JP2635986B2 JP63004151A JP415188A JP2635986B2 JP 2635986 B2 JP2635986 B2 JP 2635986B2 JP 63004151 A JP63004151 A JP 63004151A JP 415188 A JP415188 A JP 415188A JP 2635986 B2 JP2635986 B2 JP 2635986B2
- Authority
- JP
- Japan
- Prior art keywords
- optical
- mode
- coupling
- directional coupler
- 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.)
- Expired - Lifetime
Links
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
Landscapes
- 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〕 本発明は光通信等において光波の変調，光路の切替え
等を行なう光スイッチに関し、特に基板上に形成された
光導波路を用いた光導波路スイッチに関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch for modulating an optical wave, switching an optical path, and the like in optical communication and the like, and more particularly, to an optical waveguide switch using an optical waveguide formed on a substrate. About.
光通信システムの実用化が進み、大容量や多機能をも
つさらに高度のシステムへと開発が進められている。光
伝送路網の交換機能，光データバスにおける端末間の高
速接続，切替え等の新たな機能が求められており、それ
らを可能にする光スイッチングネットワークの必要性が
高まっている。現在実用されている光スイッチは、プリ
ズム，ミラー，ファイバ等を機械的に移動させるもので
あり、低速であること，信頼性が不十分なこと，形状が
大きくマトリクス化に不適なこと等の欠点がある。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基板
上に設置した光導波路を用いた導波路の光スイッチであ
り、高速，多素子の集積化が可能，高信頼等の特長があ
る。特に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長がある。Optical communication systems have been put into practical use, and are being developed into more advanced systems having large capacity and multiple functions. New functions such as a switching function of an optical transmission line network, high-speed connection between terminals on an optical data bus, and switching are required, and the need for an optical switching network that enables these functions is increasing. Optical switches currently in use are those that mechanically move prisms, mirrors, fibers, etc., and have disadvantages such as low speed, insufficient reliability, and large shapes that are unsuitable for matrix formation. There is. What is being developed as a means for solving this problem is a waveguide optical switch using an optical waveguide installed on a substrate, and has features such as high speed, integration of many elements, and high reliability. In particular, those using a ferroelectric material such as LiNbO 3 crystal,
It has features such as low light absorption and low loss, and high efficiency due to having a large electro-optic effect.
一般に光スイッチは光伝送路中に挿入され、光ファイ
バ中を伝搬した光信号の光路を切り替えるために使用さ
れる場合が多い。高速，大容量の光通信システムでは光
ファイバとして単一モード光ファイバが使用され、光源
には半導体レーザが使われる。半導体レーザ光は直線偏
光を出射するが、単一モード光ファイバ中を伝搬された
光波は一般にだ円偏光となり、また、その偏光状態も時
間的に変動する。一方、前述の導波形の光スイッチで
は、通常の構成の場合、スイッチ電圧，クロストーク等
の特性は入射光の偏光状態に大きく依存するという欠点
がある。第２図（ａ）は従来の導波形光スイッチの一例
である方向性結合形光スイッチを示す斜視図である。光
学軸すなわちｚ軸方向に垂直に切り出して整形したLiNb
O3結晶基板31上にTi等の金属を拡散して光導波路32,33
が形成されている。光導波路32,33は数μｍ程度の間隔
で近接して設置されることにより光方向性結合器34を構
成しており、光導波路32,33上にバッファ層であるSiO2
膜（第２図（ａ）では図示は省略）を介して制御電極35
及び39が設置されている。この光スイッチの基本的な動
作原理は、先ず、片方の光導波路例えば32の端面から入
射した光波16は光導波路32中を伝搬し、光方向性結合器
34の部分で近接した光導波路33にエネルギーが移行し、
光方向性結合器34の長さを完全結合長Lcに一致させた場
合は、ほぼ100％のエネルギーが光導波路33に移って出
射光37となる。一方、制御電極35と39の間に電圧を印加
した場合、電気光学効果によって光導波路32,33の屈折
率が変化して両者の屈折率が非対称となり、両者を伝搬
する光波の間で位相不整合が生じて結合状態が変化し、
適当な印加電圧の下ではもとの光導波路32へエネルギー
が移り出射光38となる。そのスイッチング動作に必要な
印加電圧は方向性結合器の長さに反比例する。ここで、
基板上に形成された光導波路の伝搬光は一般に独立な２
つのモード、即ち、偏光方向が基板表面に垂直なTMモー
ドとそれに直交する偏光成分をもつTEモードに分離され
る。Generally, an optical switch is inserted into an optical transmission line and is often used to switch the optical path of an optical signal propagated in an optical fiber. In a high-speed, large-capacity optical communication system, a single mode optical fiber is used as an optical fiber, and a semiconductor laser is used as a light source. Semiconductor laser light emits linearly polarized light, but a light wave propagated in a single-mode optical fiber generally becomes elliptically polarized light, and its polarization state also varies with time. On the other hand, the above-mentioned waveguide type optical switch has a drawback that, in the case of a normal configuration, characteristics such as switch voltage and crosstalk greatly depend on the polarization state of incident light. FIG. 2A is a perspective view showing a directional coupling type optical switch which is an example of a conventional waveguide type optical switch. LiNb cut out and shaped perpendicular to the optical axis, that is, the z-axis direction
O 3 optical waveguide 32 and 33 by diffusing metal such as Ti on the crystal substrate 31
Are formed. The optical waveguides 32 and 33 are arranged close to each other at an interval of about several μm to constitute an optical directional coupler 34, and a buffer layer SiO 2 is provided on the optical waveguides 32 and 33.
The control electrode 35 is provided via a film (not shown in FIG. 2A).
And 39 have been established. The basic operation principle of this optical switch is as follows. First, a light wave 16 incident from one end face of one of the optical waveguides, for example, 32 propagates through the optical waveguide 32 and the optical directional coupler.
The energy is transferred to the optical waveguide 33 adjacent at the part 34,
When the length of the optical directional coupler 34 is set to be equal to the complete coupling length Lc, almost 100% of the energy is transferred to the optical waveguide 33 and becomes the emission light 37. On the other hand, when a voltage is applied between the control electrodes 35 and 39, the refractive indices of the optical waveguides 32 and 33 change due to the electro-optic effect, the refractive indices of the two become asymmetric, and a phase mismatch occurs between the light waves propagating through both. Matching occurs and the bond changes,
Under an appropriate applied voltage, the energy is transferred to the original optical waveguide 32 and becomes the emitted light 38. The applied voltage required for the switching operation is inversely proportional to the length of the directional coupler. here,
The light propagated through the optical waveguide formed on the substrate is generally independent of two.
There are two modes: a TM mode in which the polarization direction is perpendicular to the substrate surface and a TE mode having a polarization component orthogonal to the TM mode.
従来の上述の基板方位をもつ光スイッチに用いられて
いる光導波路ではTMモードとTEモードでは伝搬定数が大
きく異なる。この結果、第２図（ｂ）に示すようにそれ
ぞれのモードに対する完全結合長Lc（TM）とLc（TE）は
大きく異なっている。そこで第２図（ａ）に示す通常の
光スイッチでは光方向性結合器の長さをLc（TM）に一致
させており、印加電圧０のときの光方向性結合器の出射
状態は両モードでは異なっていた。In the optical waveguide used for the conventional optical switch having the above-described substrate orientation, the propagation constant is largely different between the TM mode and the TE mode. As a result, as shown in FIG. 2 (b), the complete coupling lengths Lc (TM) and Lc (TE) for each mode are significantly different. Therefore, in the ordinary optical switch shown in FIG. 2 (a), the length of the optical directional coupler is made equal to Lc (TM), and when the applied voltage is 0, the emission state of the optical directional coupler is in both modes. Then it was different.
また一方、通常、電気光学効果によって変化する屈折
率変化量は偏光方向によって異なり、その結果スイッチ
電圧も偏光方向によって大きく異なる。例えば、第２図
（ａ）の場合、TMモード,TEモードに対して得られる屈
折率変化量はそれぞれ となる。ここで、r33,r31はそれぞれ電気光学定数、ne,
noはそれぞれ異常光，常光に対する屈折率、Ｅはｚ方向
に印加される電界強度である。LiNbO3結晶の場合、r33
＞3r13であるので、δnTM＞３δnTEとなり、TEモードの
スイッチ電圧はTMモードのスイッチ電圧の３倍以上の値
となる。そこで通常は入射光をTMまたはTEモードのいず
れか一方の偏光状態に一致させる必要が生じ、第２図
（ａ）の構成の光スイッチは単一モード光ファイバ伝送
路中に挿入して使用することはできない。On the other hand, the amount of change in the refractive index, which usually changes due to the electro-optic effect, differs depending on the polarization direction, and as a result, the switch voltage also differs greatly depending on the polarization direction. For example, in the case of FIG. 2 (a), the refractive index change amounts obtained for the TM mode and the TE mode are respectively Becomes Here, r 33 and r 31 are electro-optical constants, ne ,
n o is the refractive index for extraordinary light and ordinary light, respectively, and E is the electric field intensity applied in the z direction. In the case of LiNbO 3 crystal, r 33
Because> is 3r 13, δn TM> 3δn TE, and the switch voltage of the TE mode is three times the value of the switch voltage TM mode. Therefore, it is usually necessary to make the incident light coincide with either the polarization state of the TM mode or the TE mode, and the optical switch having the configuration of FIG. 2A is inserted into a single-mode optical fiber transmission line and used. It is not possible.
上述の通常の光スイッチの偏光依存性を除くために第
３図に示す光スイッチが1979年11月15日付アプライド・
フィジックス誌（Appl.Phys.Lett.）第35巻,10号,748〜
750頁に報告されている。第３図の光スイッチは第２図
（ａ）の通常の光スイッチと基板方位は同じであるが、
光方向性結合器44を構成する２つの光導波路42と43の間
隔が光透過方向に連続的に変化し、その結果結合係数も
連続的に変化している。また、制御電極の一方が電極45
と46に分割されている。この従来の偏光依存性を除去し
た光スイッチでは、電極45と46に印加する電圧が異な
り、また出力光を47と48に切替える場合には電極45と46
にはそれぞれ独立に異なる電圧を印加する必要がある。
その結果、駆動方法が非常に複雑となる。また、上述の
ように光透過方向に連続的に結合係数を変化させること
によって、電圧を印加した場合のTM,TE両モードに対す
る切換え状態の印加電圧に対する依存性を小さくし、冗
長性をもたしているが、このため逆に動作電圧が非常に
大きい。報告されている例では動作電圧と素子長の積は
波長1.3μｍに対しては通常のTMモードに対する光スイ
ッチの７倍程度に当る90vの電圧を必要としている。In order to eliminate the polarization dependence of the ordinary optical switch described above, the optical switch shown in FIG.
Physics (Appl. Phys. Lett.) Volume 35, Issue 10, 748-
It is reported on page 750. The optical switch of FIG. 3 has the same substrate orientation as the normal optical switch of FIG.
The interval between the two optical waveguides 42 and 43 constituting the optical directional coupler 44 changes continuously in the light transmission direction, and as a result, the coupling coefficient also changes continuously. One of the control electrodes is an electrode 45.
And is divided into 46. In this conventional optical switch from which the polarization dependency is removed, the voltages applied to the electrodes 45 and 46 are different, and when the output light is switched to 47 and 48, the electrodes 45 and 46 are used.
, It is necessary to independently apply different voltages.
As a result, the driving method becomes very complicated. In addition, by continuously changing the coupling coefficient in the light transmission direction as described above, the dependence on the applied voltage of the switching state for both the TM and TE modes when a voltage is applied is reduced, and redundancy is provided. However, on the contrary, the operating voltage is very large. In the reported example, the product of the operating voltage and the element length requires a voltage of 90 V, which is about seven times the optical switch for the normal TM mode for a wavelength of 1.3 μm.
本発明の目的は上述の従来の光導波路スイッチの欠点
を除き、入射光の偏光状態に対する依存性がなく、スイ
ッチ電圧が低くまた、駆動方法が簡単な光導波路スイッ
チを提供することにある。An object of the present invention is to provide an optical waveguide switch which has no dependency on the polarization state of incident light, has a low switch voltage, and has a simple driving method, except for the above-mentioned disadvantages of the conventional optical waveguide switch.
本発明による光導波路スイッチは、光軸（Ｚ軸）に平
行に切り出した電気光学効果を有する結晶基板上に形成
した光軸に垂直方向に光波を伝搬させる互いに近接した
２本の光導波路からなる光方向性結合器と、前記２本の
光導波路間及び前記２本の光導波路の外側にそれぞれ設
置された３本の制御電極とからなり、電界成分が基板に
垂直な偏光モード（TMモード）と基板に平行な偏光モー
ド（TEモード）に対する上記光方向性結合器の結合係数
がほぼ一致し、かつその結合係数は光透過方向の一定の
長さにおいて一様な値をもち、かつ、その長さは光方向
性結合器の完全結合長に等しく、前記それぞれの制御電
極は前記光方向性結合器の全体にわたって連続してい
る。An optical waveguide switch according to the present invention includes two optical waveguides formed on a crystal substrate having an electro-optic effect and cut in parallel to an optical axis (Z axis) and adjacent to each other, which propagate light waves in a direction perpendicular to the optical axis. A polarization mode (TM mode) comprising an optical directional coupler and three control electrodes provided between and between the two optical waveguides and outside the two optical waveguides, respectively, in which an electric field component is perpendicular to the substrate. And the coupling coefficient of the optical directional coupler for the polarization mode (TE mode) parallel to the substrate is substantially the same, and the coupling coefficient has a uniform value at a certain length in the light transmission direction, and The length is equal to the full coupling length of the light directional coupler, and the respective control electrodes are continuous throughout the light directional coupler.
本発明では、先ず、従来の第２図，第３図の光スイッ
チと異なり、光方向性結合器の結合長をTEモードとTMモ
ードを一致させている。これは、発明者等が光導波路を
作製する際にTi膜厚を特定の膜厚に制御すればTEモード
とTMモードの完全結合長を再現よく一致させられること
を見い出したことを利用するものである。In the present invention, first, unlike the conventional optical switch shown in FIGS. 2 and 3, the coupling length of the optical directional coupler is made to match between the TE mode and the TM mode. This is based on the fact that the inventors have found that the perfect coupling length between the TE mode and the TM mode can be reproducibly matched by controlling the Ti film thickness to a specific thickness when fabricating an optical waveguide. It is.
また、本発明では従来の方向性結合形光スイッチで通
常用いられている光軸（Ｚ軸）方向に垂直に切り出した
基板（Ｚ板）ではなくＸ軸に対して垂直に切り出した基
板（Ｘ板）を用いている。上述のTE,TMモードの完全結
合長が一致する条件を満たす光方向性結合器を構成する
光導波路の屈折率は従来の方向性結合形光スイッチを構
成する光導波路の屈折率より小さいため、同一の完全結
合長の光方向性結合器を比べた場合、従来よりも光導波
路間の間隔は大きくなる。そこで、光導波路上に電極を
設置して深さ方向の電界成分を利用して制御するＺ板を
用いるよりもＸ板を用いて基板表面方向（Ｚ方向）電界
成分を利用して制御する方がスイッチ電圧は低いため本
発明ではＸ板を用いる。Further, in the present invention, a substrate (X plate) cut out perpendicular to the X axis, instead of a substrate (Z plate) cut out perpendicular to the optical axis (Z axis) direction, which is usually used in a conventional directional coupling type optical switch. Board). Since the refractive index of the optical waveguide constituting the optical directional coupler that satisfies the condition that the complete coupling lengths of the TE and TM modes match each other is smaller than the refractive index of the optical waveguide constituting the conventional directional coupling optical switch, When the optical directional couplers having the same perfect coupling length are compared, the distance between the optical waveguides is larger than before. Therefore, it is more preferable to use an X-plate to control by using an electric field component in the direction of the substrate surface (Z direction) than to use a Z-plate in which an electrode is placed on an optical waveguide and control is performed using an electric field component in a depth direction. However, since the switch voltage is low, an X plate is used in the present invention.
またさらに、本発明では、第３図の従来の光スイッチ
とは異なり、方向性結合器の光透過方向全体にわたって
２本の光導波路間隔は一定であり、また、制御電極は方
向性結合器全体にわたって連続して設置されている。こ
のように方向性結合器の結合係数が一様な場合でもr33
を利用するモード（本発明ではTEモード）に対するスイ
ッチ電圧の3.5倍付近のある電圧を選択して印加すれば
少くとも波長1.3μｍ付近においてはクロストークが−2
0dB以下と十分に小さい値が得られることを見出した結
果に基づいている。すなわち印加電圧は第３図の従来の
光スイッチに比べると大幅に低減される。Further, in the present invention, unlike the conventional optical switch shown in FIG. 3, the distance between the two optical waveguides is constant over the entire light transmission direction of the directional coupler, and the control electrode is the entire directional coupler. It is installed continuously over. Thus, even if the coupling coefficient of the directional coupler is uniform, r 33
If a certain voltage near 3.5 times the switch voltage with respect to the mode (TE mode in the present invention) is selected and applied, the crosstalk becomes −2 at least around the wavelength of 1.3 μm.
Based on the finding that a sufficiently small value of 0 dB or less can be obtained. That is, the applied voltage is greatly reduced as compared with the conventional optical switch shown in FIG.
次に本発明の実施例を説明する 第１図（ａ）は本発明による光導波路スイッチの一実
施例を示す斜視図である。Ｘ軸に垂直に切り出したLiNb
O3基板11上に幅が数〜十数μｍのTi膜パターンを熱拡散
して形成した光導波路2,3が近接して設置され方向性結
合器４を構成している。本実施例では第２図（ａ）の例
とは異なりTi膜幅、Ti膜厚と拡散温度，時間を調整して
TM,TE両モードに対する完全結合長が一致し、それが方
向性結合器４の結合部の長さに一致するように選ばれて
いる。基板中に拡散されたTiはガウス分布をしているが
本実施例ではその平均濃度は0.6〜0.9％となるように制
御されているので上述のTM,TE両モードの完全結合長の
一致が得られる。このときの方向性結合器の長さと両モ
ードの結合度の関係を第１図（ｂ）に示す。光方向性結
合器４を構成する光導波路2,3の間には制御電極12が、
光導波路2,3の外側にはそれぞれ制御電極13,14が設置さ
れている。制御電極12と13,14の間に電圧を印加すると
光導波路2,3中には互いに逆向きの電界が生じ、互いに
逆極性の屈折率変化が生じてスイッチング動作が得られ
る。すなわち、電圧０の状態では光方向性結合器４はT
E,TM両モードに対して結合度１であり、光導波路２への
入射光16は出射光７となるが、適当な印加電圧の下では
両モードとも結合度０となり入射光16は出射光８とな
る。このスイッチングに必要な印加電圧は従来の偏光に
依存しない光スイッチの半分以下である。Next, an embodiment of the present invention will be described. FIG. 1 (a) is a perspective view showing an embodiment of an optical waveguide switch according to the present invention. LiNb cut out perpendicular to the X axis
Optical waveguides 2 and 3 formed by thermally diffusing a Ti film pattern having a width of several to several tens of μm on an O 3 substrate 11 are arranged close to each other to constitute a directional coupler 4. In this embodiment, unlike the example of FIG. 2A, the width of the Ti film, the thickness of the Ti film, the diffusion temperature, and the time are adjusted.
The perfect coupling length for both TM and TE modes is selected so that it matches the coupling length of the directional coupler 4. Ti diffused in the substrate has a Gaussian distribution, but in this embodiment, the average concentration is controlled to be 0.6 to 0.9%. can get. FIG. 1B shows the relationship between the length of the directional coupler and the degree of coupling between the two modes at this time. A control electrode 12 is provided between the optical waveguides 2 and 3 constituting the optical directional coupler 4.
Control electrodes 13 and 14 are provided outside the optical waveguides 2 and 3, respectively. When a voltage is applied between the control electrodes 12 and 13 and 14, electric fields in opposite directions are generated in the optical waveguides 2 and 3, and refractive index changes of opposite polarities are generated, and a switching operation is obtained. That is, when the voltage is 0, the optical directional coupler 4 is at T
The coupling degree is 1 for both the E and TM modes, and the incident light 16 to the optical waveguide 2 becomes the outgoing light 7, but under an appropriate applied voltage, the coupling degree becomes 0 for both modes and the incident light 16 becomes the outgoing light. It becomes 8. The applied voltage required for this switching is less than half that of the conventional polarization independent optical switch.
なお、通常、光導波路上に制御電極を設置する場合に
は、電極による光吸収を防ぐため光導波路上にSiO2膜等
のバッファ層を介して制御電極を設置するが、本実施例
では制御電極13,14は光導波路上にないためバッファ層
が不要であり、若干の光波エネルギーが浸み出す制御電
極12の下のみにバッファ層を設置すればよい。このため
バッファ層を介することによる電界強度の低下が小さく
なり、バッファ層を使用したＺ板上のスイッチよりもス
イッチ電圧は小さい。また、さらに制御電極12の下に酸
化マグネシウム（MgO）を拡散して屈折率を低下させる
ことにより、バッファ層を除いても光吸収を小さくする
ことができ、スィッチ電圧はさらに低減する。Normally, when a control electrode is provided on the optical waveguide, the control electrode is provided via a buffer layer such as an SiO 2 film on the optical waveguide to prevent light absorption by the electrode. Since the electrodes 13 and 14 are not on the optical waveguide, a buffer layer is not required, and the buffer layer may be provided only under the control electrode 12 where a small amount of light wave energy leaks. For this reason, the decrease in the electric field strength due to the interposition of the buffer layer is small, and the switch voltage is lower than that of the switch on the Z plate using the buffer layer. Further, by further lowering the refractive index by diffusing magnesium oxide (MgO) under the control electrode 12, light absorption can be reduced even without the buffer layer, and the switch voltage is further reduced.
尚、基板に不純物を導入する方法は実施例では拡散を
用いたが他の方法、例えばイオン注入，イオン交換等の
方法でもよい。Although the method of introducing impurities into the substrate uses diffusion in the embodiment, other methods such as ion implantation and ion exchange may be used.
以上述べたように本発明によれば入射光の偏光状態に
対する依存性がなく、スイッチ電圧が低く、また駆動方
法が簡単な光導波路スイッチが得られる。As described above, according to the present invention, an optical waveguide switch having no dependency on the polarization state of incident light, a low switch voltage, and a simple driving method can be obtained.
第１図（ａ），（ｂ）は本発明による光導波路スイッチ
の一実施例を示す斜視図及びその特性を示す図、第２図
（ａ），（ｂ），第３図は従来の光導波路スイッチの一
例を示す斜視図及びその特性を示す図である。 11,31……LiNbO3結晶基板、4,34,44……光方向性結合
器、2,3,32,33,42,43……光導波路、12,13,14,3539,45,
46……制御電極、16……入射光、7,8,37,38,47,48……
出射光、1 (a) and 1 (b) are perspective views showing one embodiment of an optical waveguide switch according to the present invention and a diagram showing its characteristics, and FIGS. 2 (a), (b) and 3 are conventional optical waveguide switches. It is the perspective view which shows an example of a waveguide switch, and the figure which shows the characteristic. 11,31… LiNbO 3 crystal substrate, 4,34,44 …… Directional coupler, 2,3,32,33,42,43 …… Optical waveguide, 12,13,14,3539,45,
46: Control electrode, 16: Incident light, 7, 8, 37, 38, 47, 48 ...
Outgoing light,
Claims (2)
するニオブ酸リチウム結晶基板上に形成した光軸に垂直
方向に光波を伝搬させる互いに近接した２本の光導波路
からなる光方向性結合器と、前記２本の光導波路間及び
前記２本の光導波路の外側にそれぞれ設置されたＺ軸方
向に電界を印加するための３本の制御電極とからなり、
前記光導波路は前記ニオブ酸リチウム結晶基板にチタン
を平均濃度0.6〜0.9で導入して形成したものであり、 電界成分が基板に垂直な偏光モード（TMモード）と基板
に平行な偏光モード（TEモード）に対する前記光方向性
結合器の結合係数がほぼ一致し、かつその結合係数は光
透過方向の一定の長さにおいて一様な値をもち、かつ、
その長さは前記光方向性結合器の完全結合長に等しく、
前記それぞれの制御電極は前記光方向性結合器の全体に
わたって連続しており、 前記光方向性結合器を構成する２本の光導波路間の制御
電極下のみにバッファ層が形成され、他の２つの制御電
極は直接基板に接しており、 前記制御電極への印加電圧を、TEモードの結合度が最初
に最小となる電圧値の３倍程度以上でかつTEモード、TM
モードともに結合度が０付近となる電圧値、または0Vと
することによりスイッチング動作を行うことを特徴とす
る光導波路スイッチ。1. An optical directional coupling comprising two optical waveguides which are formed on a lithium niobate crystal substrate having an electro-optical effect and which is cut out perpendicular to the X axis and which propagates an optical wave in a direction perpendicular to an optical axis and which are close to each other. And three control electrodes for applying an electric field in the Z-axis direction provided between the two optical waveguides and outside the two optical waveguides, respectively.
The optical waveguide is formed by introducing titanium into the lithium niobate crystal substrate at an average concentration of 0.6 to 0.9, and a polarization mode in which an electric field component is perpendicular to the substrate (TM mode) and a polarization mode parallel to the substrate (TE mode). Mode), the coupling coefficient of the optical directional coupler substantially matches, and the coupling coefficient has a uniform value at a certain length in the light transmission direction, and
Its length is equal to the full coupling length of the optical directional coupler,
The respective control electrodes are continuous over the entire optical directional coupler, and a buffer layer is formed only under the control electrode between the two optical waveguides constituting the optical directional coupler. The two control electrodes are in direct contact with the substrate, and the voltage applied to the control electrodes is about three times or more the voltage value at which the degree of coupling in the TE mode is first minimized, and the TE mode and the TM
An optical waveguide switch characterized in that a switching operation is performed by setting a voltage value at which the degree of coupling becomes close to 0 or a voltage value of 0 V in both modes.
するニオブ酸リチウム結晶基板上に形成した光軸に垂直
方向に光波を伝搬させる互いに近接した２本の光導波路
からなる光方向性結合器と、前記２本の光導波路間及び
前記２本の光導波路の外側にそれぞれ設置されたＺ軸方
向に電界を印加するための３本の制御電極とからなり、
前記光導波路は前記ニオブ酸リチウム結晶基板にチタン
を平均濃度0.6〜0.9で導入して形成したものであり、 電界成分が基板に垂直な偏光モード（TMモード）と基板
に平行な偏光モード（TEモード）に対する前記光方向性
結合器の結合係数がほぼ一致し、かつその結合係数は光
透過方向の一定の長さにおいて一様な値をもち、かつ、
その長さは前記光方向性結合器の完全結合長に等しく、
前記それぞれの制御電極は前記光方向性結合器の全体に
わたって連続しており、 前記光方向性結合器を構成する２本の光導波路間の制御
電極下にマグネシウムを含む領域が形成され、３つの制
御電極は直接基板に接しており、 前記制御電極への印加電圧を、TEモードの結合度が最初
に最小となる電圧値の３倍程度以上でかつTEモード、TM
モードともに結合度が０付近となる電圧値、または0Vと
することによりスイッチング動作を行うことを特徴とす
る光導波路スイッチ。2. A light directional coupling comprising two optical waveguides which are formed on a lithium niobate crystal substrate having an electro-optic effect and which is cut out perpendicular to the X axis and which propagates a light wave in a direction perpendicular to the optical axis and which are close to each other. And three control electrodes for applying an electric field in the Z-axis direction provided between the two optical waveguides and outside the two optical waveguides, respectively.
The optical waveguide is formed by introducing titanium into the lithium niobate crystal substrate at an average concentration of 0.6 to 0.9, and a polarization mode in which an electric field component is perpendicular to the substrate (TM mode) and a polarization mode parallel to the substrate (TE mode). Mode), the coupling coefficient of the optical directional coupler substantially matches, and the coupling coefficient has a uniform value at a certain length in the light transmission direction, and
Its length is equal to the full coupling length of the optical directional coupler,
The respective control electrodes are continuous throughout the optical directional coupler, and a region including magnesium is formed under the control electrode between the two optical waveguides forming the optical directional coupler, and three regions are formed. The control electrode is in direct contact with the substrate, and the voltage applied to the control electrode is about three times or more the voltage value at which the degree of coupling in the TE mode is first minimized, and the TE mode, TM
An optical waveguide switch characterized in that a switching operation is performed by setting a voltage value at which the degree of coupling becomes close to 0 or a voltage value of 0 V in both modes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63004151A JP2635986B2 (en) | 1988-01-11 | 1988-01-11 | Optical waveguide switch |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63004151A JP2635986B2 (en) | 1988-01-11 | 1988-01-11 | Optical waveguide switch |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01179918A JPH01179918A (en) | 1989-07-18 |
| JP2635986B2 true JP2635986B2 (en) | 1997-07-30 |
Family
ID=11576763
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63004151A Expired - Lifetime JP2635986B2 (en) | 1988-01-11 | 1988-01-11 | Optical waveguide switch |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2635986B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7809217B2 (en) | 2007-01-23 | 2010-10-05 | Murata Manufacturing Co., Ltd. | Light control element |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4997245A (en) * | 1990-01-04 | 1991-03-05 | Smiths Industries Aerospace & Defense Systems Incorporated | Polarization independent optical switches |
| CN111290191B (en) * | 2020-02-19 | 2023-07-18 | 联合微电子中心有限责任公司 | Directional coupler and optical switch based on silicon nitride platform |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57161837A (en) * | 1981-03-31 | 1982-10-05 | Nec Corp | Optical switching method |
-
1988
- 1988-01-11 JP JP63004151A patent/JP2635986B2/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| 昭和６２年電子情報通信学会半導体・材料部門全国大会予稿集２−１４０〜１４１頁（発表番号３５３、３５４） |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7809217B2 (en) | 2007-01-23 | 2010-10-05 | Murata Manufacturing Co., Ltd. | Light control element |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01179918A (en) | 1989-07-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7356227B2 (en) | Optical switch, optical modulator and wavelength variable filter | |
| JP2679570B2 (en) | Polarization separation element | |
| JPH1073737A (en) | Integrated optical polarizing element | |
| US4983006A (en) | Polarization-independent optical waveguide switch | |
| US4561718A (en) | Photoelastic effect optical waveguides | |
| JPH0728007A (en) | Waveguide type optical device | |
| JPH07318986A (en) | Waveguide type optical switch | |
| JPH05196972A (en) | Waveguide type optical directional coupler | |
| JP2932742B2 (en) | Waveguide type optical device | |
| JPH1184434A (en) | Light control circuit and its operation method | |
| JP2635986B2 (en) | Optical waveguide switch | |
| JP2000028979A (en) | Optical control element independent of polarization | |
| JP2936792B2 (en) | Waveguide type optical device | |
| JPH0820651B2 (en) | Optical waveguide switch | |
| JPH0721597B2 (en) | Optical switch | |
| JP2613942B2 (en) | Waveguide type optical device | |
| JPH0756199A (en) | Polarization-independent waveguide type optical switch | |
| JPH0553157A (en) | Optical control device | |
| JPH0697286B2 (en) | Optical circuit and manufacturing method thereof | |
| JPH0750285B2 (en) | Optical switching method | |
| JP2705134B2 (en) | Directional coupler type waveguide optical switch | |
| JPS63163432A (en) | Optical switch | |
| JPH01201628A (en) | Optical switch | |
| JPS63262625A (en) | Waveguide type optical switch | |
| JPH03188423A (en) | Optical directional coupler and production thereof |