JPS63262625A - Waveguide type optical switch - Google Patents
Waveguide type optical switchInfo
- Publication number
- JPS63262625A JPS63262625A JP62098853A JP9885387A JPS63262625A JP S63262625 A JPS63262625 A JP S63262625A JP 62098853 A JP62098853 A JP 62098853A JP 9885387 A JP9885387 A JP 9885387A JP S63262625 A JPS63262625 A JP S63262625A
- Authority
- JP
- Japan
- Prior art keywords
- waveguide
- directional coupler
- equal
- light
- optical
- 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
- 230000003287 optical effect Effects 0.000 title claims abstract description 50
- 239000000758 substrate Substances 0.000 claims abstract description 28
- 230000005540 biological transmission Effects 0.000 claims abstract description 15
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 238000005342 ion exchange Methods 0.000 claims abstract description 5
- 239000013078 crystal Substances 0.000 claims description 22
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 7
- 230000001568 sexual effect Effects 0.000 claims 1
- 230000008878 coupling Effects 0.000 abstract description 17
- 238000010168 coupling process Methods 0.000 abstract description 17
- 238000005859 coupling reaction Methods 0.000 abstract description 17
- 230000005684 electric field Effects 0.000 abstract description 8
- 238000000034 method Methods 0.000 abstract description 5
- 230000010287 polarization Effects 0.000 description 21
- 238000009792 diffusion process Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 description 4
- 239000010408 film Substances 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 239000013307 optical fiber Substances 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- 238000004891 communication Methods 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 239000005711 Benzoic acid Substances 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 235000010233 benzoic acid Nutrition 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- 244000025254 Cannabis sativa Species 0.000 description 1
- 229910003327 LiNbO3 Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 239000002344 surface layer Substances 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
- 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)
- Optical Communication System (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、光通信用の光制御素子に関し、とくに素子の
特性が入射光の偏光状態に依存しない導波路型光制御デ
バイスに関する。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a light control element for optical communication, and particularly to a waveguide type light control device whose properties do not depend on the polarization state of incident light.
（従来の技術）
光通信システムの実用化が進み、大容量や多機能を持つ
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、切り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ツチングネットワークの必要性が高
まってきている。(Prior Art) Optical communication systems have been put into practical use, and more advanced systems with large capacity and multiple functions are being developed. New functions such as switching functions of optical transmission networks, high-speed connections between terminals in optical data buses, and switching are required, and the need for optical switching networks that make these functions possible is increasing.
現在実用されている光スィッチは、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、低速で信
頼性が不十分であること、形状が大きくマトリクス化に
は不適当などの欠点がある。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
路を用いた導波型のスイシチであり、高速、多素子の集
積化が可能、高信頼などの特長がある。特にＬｉＮｂＯ
３結晶なと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
るため高能率であるなどの特長を持つ。Optical switches currently in use include prisms, mirrors,
This method mechanically moves fibers, etc., and has drawbacks such as low speed and insufficient reliability, and large size making it unsuitable for matrix formation. What is currently being developed as a means to solve this problem is a waveguide type switch that uses optical waveguides installed on a substrate, and has features such as high speed, the ability to integrate multiple elements, and high reliability. . Especially LiNbO
Those using tricrystalline ferroelectric materials have features such as low light absorption and low loss, and high efficiency because they have a large electro-optic effect.
一般に光スィッチは光伝送路中に挿入され、光フアイバ
中を伝送され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シアイバが使用される。単
一モードファイバ中を透過した光波は、一般に楕円偏光
であり、またその偏光状態も時間的に変動する。これま
での導波型の光スィッチでは、電圧、クロストークなど
のスイッチ特性は、入射光の偏光状態に大きく依存する
。このため、光フアイバ伝送路の途中にこの導波型光ス
イッチを挿入することは困難である。Generally, an optical switch is inserted into an optical transmission line and is often used to switch the optical path of an optical signal transmitted through an optical fiber. Single-mode optical shear fibers are used as optical fibers in high-speed, large-capacity optical communication systems. A light wave transmitted through a single mode fiber is generally elliptically polarized light, and its polarization state also changes over time. In conventional waveguide type optical switches, switch characteristics such as voltage and crosstalk largely depend on the polarization state of incident light. Therefore, it is difficult to insert this waveguide type optical switch in the middle of an optical fiber transmission line.
従来の導波型光スイッチの特性に偏光依存性が生じる原
因は、結晶基板の持つ屈折率及び用いる電気光学定数に
異方性があることである。例えば代表的°な例として、
２板ニオブ酸リチウム結晶にＴｉ拡散光導波路を築き、
導波路上に設けた電極間の電界Ｅｚを介して生ずる屈折
率の変化Δｎｚ、Δｎｙを通じて、導波路を伝搬する光
波モニドＴＭ、 ＴＥ波に位相定数変化を与えるデバイ
スを想定したとき、電界Ｅ２とこれによって生ずる屈折
率変化Δｎｚ、Δｎｙとの間を結び付ける比例定数は、
（ｎｅ”ｒ３３）／２、（ｎｏ３ｒ１ａ）／２である。The polarization dependence in the characteristics of conventional waveguide optical switches is due to anisotropy in the refractive index of the crystal substrate and in the electro-optic constants used. For example, as a typical example,
A Ti-diffused optical waveguide is built on a two-plate lithium niobate crystal,
Assuming a device that changes the phase constant of the light wave monide TM and TE waves propagating through the waveguide through changes in the refractive index Δnz and Δny caused by the electric field Ez between the electrodes provided on the waveguide, the electric field E2 and The proportionality constant that connects the refractive index changes Δnz and Δny caused by this is:
(ne”r33)/2, (no3r1a)/2.
これらの大きさの比はおおよそ３：１であって、電界に
よって生ずる位相差は３倍異なるため、ＴＭ波に対して
は充分な電界強度であってもＴＥ波にたいしては、更に
２倍の電界強度を余計に必要とする。The ratio of these magnitudes is approximately 3:1, and the phase difference caused by the electric field is three times different, so even if the electric field strength is sufficient for TM waves, the electric field is twice as strong for TE waves. Requires extra strength.
これを改良するため、異方性の少ない結晶方位を用いる
デバイス方式として、ｙ板ニオフ酸リチウム結晶を基板
とし、導波路方向即ち光透過方向を２軸に選んで方向性
結合型光スィッチを構成する発明がある。このデバイス
の方式ではＴＭ、 ＴＥ波に関係する結晶の屈折率がい
ずれも常光線屈折率馬であり、さらに、基板の深さ方向
への印加電界成分ＥＹに関与する電気光学定数は両方と
もｒ２□であることと相まって、電界ＥＹによって生ず
る屈折率の変化の絶対値はほぼ等しく、入射光の偏光に
依存しない導波型デバイスを構成できることが期待され
る。In order to improve this, we constructed a directional coupling type optical switch by using a Y-plate lithium niophate crystal as a substrate and selecting the waveguide direction, that is, the light transmission direction, as two axes, as a device method using a crystal orientation with less anisotropy. There is an invention that does. In this device system, the refractive indices of the crystals related to TM and TE waves are both ordinary ray refractive indexes, and furthermore, the electro-optic constants related to the applied electric field component EY in the depth direction of the substrate are both r2. Coupled with the fact that □, the absolute values of the changes in the refractive index caused by the electric field EY are approximately equal, and it is expected that a waveguide type device that does not depend on the polarization of incident light can be constructed.
しかしながら、既に明らかになっているように、ｙ板ニ
オフ酸リチウム結晶にチャンネル状導波路を形成するこ
とを目的として、２軸方向を長手方向とするＴｉ線条パ
タンを形成し、これを熱拡散した場合、パタンの長手方
向とは直交する方向即ちＸ軸方向へのＴｉの拡散係数は
極めて大きいため、初期の線条パタン幅よりも数倍に広
がって拡散し、有効な光閉じ込め効果を持った光導波路
を築くことが難しい。このため数ｐｍの間隙をもった方
向性結合導波路を作ることができず、導波路間隔の極め
て広い結合導波路しか形成することができない。このた
め、スイッチング電圧が高くなり、小型のデバイスを得
ることが困難である。However, as has already been clarified, in order to form a channel-shaped waveguide in a Y-plate lithium niophosphate crystal, a Ti filament pattern with the longitudinal direction in the biaxial direction is formed, and this is thermally diffused. In this case, the diffusion coefficient of Ti in the direction perpendicular to the longitudinal direction of the pattern, that is, in the It is difficult to construct optical waveguides. For this reason, it is not possible to create a directional coupling waveguide with a gap of several pm, and only a coupling waveguide with an extremely wide waveguide spacing can be formed. Therefore, the switching voltage becomes high and it is difficult to obtain a small device.
以上のように、従来の導波型の光スィッチではは入射光
の偏光状態に応じてデバイス特性が大幅に異なるため、
前述のように光フアイバ伝送路の途中にこのデバイスを
挿入することは困難である。As mentioned above, in conventional waveguide type optical switches, the device characteristics differ significantly depending on the polarization state of the incident light.
As mentioned above, it is difficult to insert this device in the middle of an optical fiber transmission line.
（発明の目的）
本発明の目的は、上述の従来の導波型光スイッチの欠点
を取り除き、入射光の偏光状態に特性が依存しない光ス
ィッチを提供することにある。(Objective of the Invention) An object of the present invention is to eliminate the drawbacks of the conventional waveguide optical switch described above and to provide an optical switch whose characteristics do not depend on the polarization state of incident light.
（発明の構成）
本発明によれば、ニオブ酸リチウム結晶板に形成された
互いに近接した２本のチャンネル先導波路からなる方向
性結合器と該方向性結合器の近傍に設置された電極より
なり、該方向性結合器の光透過方向を前記結晶板のＣ軸
と等しくし、基板の全面に不純物を拡散したうえに、チ
ャンネルとすべき部位以外の部位に基板表面からイオン
交換を施して前記方向性結合器を構成する光導波路を設
けることによって入射光の偏光状態に特性が依存しない
導波路型光スイッチが得られる。(Structure of the Invention) According to the present invention, the directional coupler includes two channel leading waveguides formed in a lithium niobate crystal plate and adjacent to each other, and an electrode installed near the directional coupler. , the light transmission direction of the directional coupler is made equal to the C-axis of the crystal plate, impurities are diffused over the entire surface of the substrate, and ion exchange is performed from the substrate surface to areas other than the areas to be used as channels. By providing an optical waveguide constituting a directional coupler, a waveguide type optical switch whose characteristics do not depend on the polarization state of incident light can be obtained.
また第２の本発明によれば、ニオブ酸リチウム結晶板に
形成された互いに近接した２本のチャンネル光導波路か
らなる方向性結合器と該方向性結合器の近傍に設置され
た電極よりなり、該方向性結合器の光透過方向を前記結
晶板のＣ軸と等しくし、チャンネルとすべき部位のみに
基板表面より不純物を拡散し、さらに該部位以外の部位
に基板表面からイオン交換を施して前記方向性結合器を
構成する光導波路を設けることによって、入射光の偏光
状態に特性が依存しない導波路力先スイッチが得られる
。According to the second aspect of the present invention, the directional coupler includes two channel optical waveguides close to each other formed on a lithium niobate crystal plate, and an electrode installed near the directional coupler, The light transmission direction of the directional coupler is made equal to the C axis of the crystal plate, impurities are diffused from the substrate surface only to the portions that are to be channels, and ion exchange is performed from the substrate surface to other portions. By providing an optical waveguide constituting the directional coupler, a waveguide power-forward switch whose characteristics do not depend on the polarization state of incident light can be obtained.
（実施例１）
以下本発明を実施例に基づき図面を用いて詳細に説明す
る。(Example 1) The present invention will be described in detail below based on an example using the drawings.
第１図は本発明の一実施例である方向性結合器型光スイ
ッチの構造を示す上面図である。１１はＬｉＮｂ○３結
晶板であり、基板方位はｙ板（即ち基板に立てた法線は
ｙ軸）、光透過方向は結晶の２軸に選んである。結晶基
板上に近接した２本の先導波路と、これらの導波路の上
に設け、その間にスイッチ電圧を印加するための電極４
．５で構成されている。FIG. 1 is a top view showing the structure of a directional coupler type optical switch which is an embodiment of the present invention. 11 is a LiNb*3 crystal plate, the substrate orientation is y-plate (that is, the normal to the substrate is the y-axis), and the light transmission direction is selected to be the two axes of the crystal. Two leading waveguides close to each other on a crystal substrate, and an electrode 4 provided on these waveguides for applying a switch voltage between them.
．． It consists of 5.
この方向性結合器によって経路をスイッチさせる光６は
一方の導波路３がら入射する。この方向性結合器の晃透
過方向の長さは、偏光状態が不定の入射光６のＴＥ、Ｔ
Ｍ両モードに対してほぼ完全結合長（ある特定のモード
に対して一方の導波路中の光パワーが他方の導波路に総
て移行するために必要な結合器の長さ）となるように設
定されており、今、上記電極に電圧を印加しない状態で
は、一方の導波路３から入射した光は、他方の導波路２
にそのパワーを総て移行させている。ここで上記電極に
電圧を印加すると、一方の導波路３がら入射した光は隣
接する光導波路２に移行することなく全てのパワーが自
らの導波路を進んでこの方向性結合器を出射する。。Ｔ
Ｅ、ＴＭ両酸成分持つ偏光状態が不定の導波光を相互に
隣合う導波路にエネルギを残すことなくスイッチさせる
、即ち偏光状態に依存しないスイッチ特性が得られるの
は、以下の理由による。The light 6 whose path is switched by this directional coupler enters from one waveguide 3. The length of this directional coupler in the transmission direction is TE and T of the incident light 6 with an indefinite polarization state.
M so that the coupling length is almost perfect for both modes (the length of the coupler required for all the optical power in one waveguide to transfer to the other waveguide for a certain mode). If no voltage is applied to the electrodes, the light incident from one waveguide 3 will pass through the other waveguide 2.
All that power is transferred to. When a voltage is applied to the electrodes, the light incident from one waveguide 3 does not transfer to the adjacent optical waveguide 2, but all the power travels through its own waveguide and exits the directional coupler. . T
The reason why guided light having both E and TM acid components and whose polarization state is indeterminate can be switched without leaving energy in mutually adjacent waveguides, that is, switching characteristics independent of the polarization state can be obtained is as follows.
第２図は本発明の一実施例の構成図である第１図の方向
性結合器型光スイッチのＡ−Ａ’における断面図を示す
。上記の偏光依存性のない方向性結合を可能にしている
導波路の構造であって、この方向性結合導波路は次のよ
うに形成される。１のニオブ酸リチウム基板のｙ面全面
にＴｉ膜を蒸着等で設け、これを１０００°Ｃ余りで熱
拡散をする。このＴｉ拡散を施したＬｉＮｂ０ａ基板上
に、第１図の導波路パターン形状をしたＴｉ、 Ｔａ、
等の薄膜パターンを形成し、これをマスクにして加熱し
た安息香酸、リン酸等に浸してプロトン（Ｈ＋）交換を
施す。このＨ十交換時のマスクとした薄膜パターンを酸
で溶解除去等を行った後、基板全面に５ｉ０２膜を設け
、導波路上に電極４．５を設ける。Ｔｉを拡散したＬｉ
ＮｂＯ３表面層は屈折率が僅か上昇し、平面導波路を形
成する。この平面導波路内で光の横方開広がりを抑えて
チ・ヤンネル状に導波路を形成するために、チャンネル
状光導波路となるべき領域以外を表面よりＨ十交換を施
す。Ｈ十交換を施した領域８は、常光線に対する屈折率
卿が０．０４低下する。ここで使用しでいる結晶板はｙ
板であり、Ｚ軸方向に透過する光はＴＥ波にしろＴＭ波
にしろ常光線であるため、Ｈ十交換を施した領域は何れ
の偏波成分に対しても屈折率は低下している。すなわち
、基板の深さ方向にはＴｉ拡散による高屈折率層７、横
方向には屈折率の低い浅いＨ十交換層８との２つの効果
によってチャンネル状導波路２及び３が形成される。FIG. 2 shows a sectional view taken along line AA' of the directional coupler type optical switch of FIG. 1, which is a configuration diagram of an embodiment of the present invention. This is a waveguide structure that enables the above-mentioned directional coupling without polarization dependence, and this directional coupling waveguide is formed as follows. A Ti film is provided on the entire y-plane of the lithium niobate substrate No. 1 by vapor deposition or the like, and then thermally diffused at about 1000°C. On this Ti-diffused LiNb0a substrate, Ti, Ta,
A thin film pattern is formed, and this is used as a mask to immerse it in heated benzoic acid, phosphoric acid, etc. to perform proton (H+) exchange. After dissolving and removing the thin film pattern used as a mask during H1 exchange with acid, a 5i02 film is provided on the entire surface of the substrate, and electrodes 4.5 are provided on the waveguide. Li diffused with Ti
The NbO3 surface layer has a slightly increased refractive index and forms a planar waveguide. In order to suppress the lateral spread of light within this planar waveguide and form a channel-shaped waveguide, H0 exchange is performed from the surface in areas other than the area that is to become a channel-shaped optical waveguide. In region 8 subjected to H-exchange, the refractive index for ordinary rays decreases by 0.04. The crystal plate used here is y
Since it is a plate and the light transmitted in the Z-axis direction is an ordinary ray whether it is a TE wave or a TM wave, the refractive index of the region subjected to H-exchange is lower for any polarization component. . That is, the channel-shaped waveguides 2 and 3 are formed by two effects: a high refractive index layer 7 formed by Ti diffusion in the depth direction of the substrate, and a shallow H+ exchange layer 8 with a low refractive index in the lateral direction.
このように形成したチャンネル状光導波路は、ＴＥ、Ｔ
Ｍ両波にたいして等側屈折率が殆ど等しい導波路である
ため、方向性結合器を構成した場合の完全結合長は両波
にたいして等しい。従って、方向性結合器の長さをこの
完全結合長に等しく設定しておくことによって、第１図
に示す電極４及び５の間に電圧を印加しない状態では、
入射光６は総て２の導波路に結合して出射する。さらに
、電解を印加して屈折率の変化を生じさせることに関与
する電気光学定数は、両波ともにｒ２□と等しいため、
電圧印加に対する結合光強度の変化の仕方は等しく、等
しい電圧で光のスイッチ状態、すなわち、ＴＥ、ＴＭは
すべて導波路３がら出射する。The channel-shaped optical waveguide formed in this way has TE, T
Since the waveguide has almost the same refractive index on the same side for both M waves, the complete coupling length when configuring a directional coupler is equal for both waves. Therefore, by setting the length of the directional coupler equal to this perfect coupling length, when no voltage is applied between the electrodes 4 and 5 shown in FIG.
All incident light 6 is coupled to two waveguides and output. Furthermore, since the electro-optical constant involved in causing a change in refractive index by applying an electrolyte is equal to r2□ for both waves,
The intensity of the coupled light changes in the same manner with respect to the applied voltage, and the switched states of light, ie, TE and TM, are all emitted from the waveguide 3 at the same voltage.
（実施例２）
以下本発明を実施例に基づき図面を用いて詳細に説明す
る。(Example 2) The present invention will be described below in detail based on an example using the drawings.
第３図は本発明の一実施例である方向性結合器型結合器
型光スイッチの構造を示す上面図である。FIG. 3 is a top view showing the structure of a directional coupler type optical switch which is an embodiment of the present invention.
１はＬｉＮｂＯ３結晶板であり、基板方位はｙ板（即ち
基板に立てた法線はｙ軸）、光透過方向は結晶の２軸に
選んである。結晶基板上に近接した２本の光導波路と、
これらの導波路の上に設け、その間にスイッチ電圧を印
加するための電極で構成されている。1 is a LiNbO3 crystal plate, the substrate orientation is y-plate (that is, the normal to the substrate is the y-axis), and the light transmission direction is selected to be the two axes of the crystal. Two optical waveguides close to each other on a crystal substrate,
It consists of electrodes placed above these waveguides for applying a switch voltage between them.
この方向性結合器によって経路をスイッチさせる光６は
一方の導波路３から入射する。この方向性結合器の光透
過方向の長さは、偏光状態が不定の入射光６のＴＥ、Ｔ
Ｍ両モードに対してほぼ完全結合長（ある特定のモード
に対して一方の導波路中の光パワーが他方の導波路に総
て移行するために必要な結合器の長さ）となるように設
定されており、今、上記電極に電圧を印加しない状態で
は、一方の導波路３から入射した光６は、他方の導波路
２にそのパワーを総て移行させている。ここで上記電極
に電圧を印加すると、一方の導波路３から入射した光６
は隣接する光導波路２に移行することなく全てのパワー
が自らの導波路３を進んでこの方向性結合器を出射する
。ＴＥ、ＴＭ両酸成分持つ偏光状態が不定の導波光を相
互に隣合う導波路にエネルギを残すことなくスイッチさ
せる、即ち偏光状態に依存しないスイッチ特性が得られ
るのは、以下の理由による。Light 6 whose path is switched by this directional coupler enters from one waveguide 3. The length of this directional coupler in the light transmission direction is TE and T of the incident light 6 with an indefinite polarization state.
M so that the coupling length is almost perfect for both modes (the length of the coupler required for all the optical power in one waveguide to transfer to the other waveguide for a certain mode). When no voltage is applied to the electrodes, the light 6 incident from one waveguide 3 transfers all its power to the other waveguide 2. Here, when a voltage is applied to the above electrode, the light 6 that has entered from one of the waveguides 3
All the power proceeds through its own waveguide 3 and exits the directional coupler without transferring to the adjacent optical waveguide 2. The reason why guided light having both TE and TM acid components and having an indeterminate polarization state can be switched without leaving any energy in mutually adjacent waveguides, that is, switching characteristics independent of the polarization state can be obtained is as follows.
第４図は本発明の一実施例の構成図である第１図の方向
性結合器型光スイッチのＡ−Ａ’における断面図を示す
。上記の偏光依存性のない方向性結合を可能にしている
導波路の構造であって、この方向性結合導波路は次のよ
うに形成される。１のニオブ酸リチウム基板のｙ面上に
導波路を設けるべき位置に、蒸着およびリソグラフィー
技術を用いて、第３図の導波路パターンの形状にＴｉ膜
を設け、これを１０００°Ｃ余りで熱拡散をする。この
Ｔｉ拡散を施した導波路７の上にさらに、Ｔｉ、Ｔａ等
の薄膜を前記パターンに目合わせして形成し、これをマ
スクにして加熱した安息香酸、リン酸等に浸してプロト
ン（Ｈ＋）交換を施す。この後、Ｈ十交換時にマスクと
した薄膜パターンを酸で溶解等による除去を行い、基板
全面に５ｉ０２膜９を設け、さらに導波路上に電極４．
５を設ける。FIG. 4 shows a cross-sectional view taken along line AA' of the directional coupler type optical switch of FIG. 1, which is a configuration diagram of an embodiment of the present invention. This is a waveguide structure that enables the above-mentioned directional coupling without polarization dependence, and this directional coupling waveguide is formed as follows. Using vapor deposition and lithography techniques, a Ti film was provided in the shape of the waveguide pattern shown in Fig. 3 on the y-plane of the lithium niobate substrate in No. Spread the word. A thin film of Ti, Ta, etc. is further formed on the Ti-diffused waveguide 7 in alignment with the pattern, and this is used as a mask and immersed in heated benzoic acid, phosphoric acid, etc. to generate protons (H+ ) Make an exchange. After this, the thin film pattern used as a mask during H10 exchange is removed by dissolving with acid, etc., a 5i02 film 9 is provided on the entire surface of the substrate, and electrodes 4.
5 will be provided.
Ｔｉを拡散した領域は屈折率が僅か上昇したチャンネル
状導波路７を形成するが、前述の如く、Ｔｉ拡散の構法
がりが大きいために、初期の線条バタン幅よりも数倍に
広がって拡散し、有効な光閉じ込め効果を持った光導波
路となっていない。これを抑えて初期の線条バタン幅に
見合ったチャンネル状導波路とするために、光導波路と
なるべき領域以外を表面よりＨ十交換を施す。この後、
Ｈ十交換を施した領域８は、常光線に対する屈折率抑が
０．０４低下する。ここで使用している結晶板はｙ板で
あり、Ｚ軸方向に透過する光はＴＥ波にしろＴＭ波にし
ろ常光線であるため、Ｈ十交換を施した領域は何れの偏
波成分に対しても屈折率は低下している。すなわち、基
板の深さ方向にはＴｉ拡散による高屈折率層、横方向に
は屈折率の低い浅いＨ十交換層との２つの効果によって
チャンネル状導波路２及び３が形成される。The region in which Ti is diffused forms a channel-shaped waveguide 7 with a slightly increased refractive index, but as mentioned above, because the construction method of Ti diffusion is large, it spreads several times as wide as the initial width of the filament batten and is diffused. However, the optical waveguide does not have an effective optical confinement effect. In order to suppress this and create a channel-shaped waveguide commensurate with the initial filament width, H10 exchange is performed from the surface in areas other than the area to become an optical waveguide. After this,
In region 8 subjected to H-exchange, the refractive index suppression for ordinary rays is reduced by 0.04. The crystal plate used here is a y-plate, and the light transmitted in the Z-axis direction is an ordinary ray, whether it is a TE wave or a TM wave. The refractive index also decreases. That is, the channel-shaped waveguides 2 and 3 are formed by two effects: a high refractive index layer due to Ti diffusion in the depth direction of the substrate, and a shallow H 10 exchange layer with a low refractive index in the lateral direction.
このように形成したチャンネル状光導波路は、ＴＥ、Ｔ
Ｍ両波にだいして等側屈折率が殆ど等しい導波路である
ため、方向性結合器を構成した場合の完全結合長は両波
にたいして等しい。従って、方向性結合器の長さをこの
完全結合長に等しく設定しておくことによって、第３図
に示す電極４及び５の間に電圧を印加しない状態では、
入射光６は総て２の導波路に結合して出射する。さらに
、電解を印加して屈折率の変化を生じさせることに関与
する電気光学定数は、両波ともにｒ２２と等しいため、
電圧印加に対する結合光強度の変化の仕方は等しく、等
しい電圧で光のスイッチ状態、すなわち、ＴＥ、ＴＭは
すべて導波路３から出射する。The channel-shaped optical waveguide formed in this way has TE, T
Since the waveguide has almost the same refractive index on both sides of the M wave, the complete coupling length when configuring a directional coupler is the same for both waves. Therefore, by setting the length of the directional coupler equal to this perfect coupling length, when no voltage is applied between the electrodes 4 and 5 shown in FIG.
All incident light 6 is coupled to two waveguides and output. Furthermore, since the electro-optical constant involved in causing a change in refractive index by applying electrolyte is equal to r22 for both waves,
The intensity of the coupled light changes in the same manner with respect to the applied voltage, and the switched states of light, ie, TE and TM, are all emitted from the waveguide 3 at the same voltage.
本実施例では、チャンネル状導波路を形成するために、
Ｔｉ拡散、Ｈ十交換共にパターン化を行っている。Ｔｉ
拡散は必ずしもパターン化する必要はなく、基板全面に
行っても良いが、Ｔｉ拡散を施した領域は基板が盛り上
がりを見せると言う現象を利用できるため、後のプロセ
スで電極パターンを形成するときにマスクの目合わせに
便利であるという利点を有す。In this example, in order to form a channel-shaped waveguide,
Patterning is performed for both Ti diffusion and H exchange. Ti
Diffusion does not necessarily need to be patterned and can be performed over the entire surface of the substrate, but since the phenomenon that the substrate bulges in the area where Ti has been diffused can be used, it can be used when forming an electrode pattern in a later process. It has the advantage of being convenient for eye alignment of the mask.
（発明の効果）
以上説明のように、本発明によればスイッチ特性が入射
光の偏光状態に依存しない、即ちいわゆる偏光無依存の
導波型方向性結合型スイッチが得られる。(Effects of the Invention) As described above, according to the present invention, a waveguide type directional coupling switch whose switch characteristics do not depend on the polarization state of incident light, that is, so-called polarization-independent switch can be obtained.
なお、上記の実施例における説明では、ｙ板を用いた場
合を説明したが、Ｘ板を用い２軸に光透過方向を選んで
も同様の偏光無依存の光スィッチが得られる。In the above embodiments, a case was explained in which a Y plate was used, but a similar polarization-independent optical switch can be obtained even if an X plate is used and the light transmission direction is set along two axes.
第１図、第３図は本発明の一実施例の構造を説明する上
面図であり、第２図、第４図はその断面図である。
図中
１はＬｉＮｂ０３ｙ板、２，３は導波路、４，５は電極
、７は茅 １ 凹
影ν ノ ■1 and 3 are top views illustrating the structure of an embodiment of the present invention, and FIGS. 2 and 4 are sectional views thereof. In the figure, 1 is a LiNb03y board, 2 and 3 are waveguides, 4 and 5 are electrodes, and 7 is grass. 1 Concave shadow ν ノ ■
Claims (1)
た２本のチャンネル光導波路からなる方向性結合器と該
方向性結合器の近傍に設置された電極よりなり、該方向
性結合器の光透過方向は、前記結晶板のＣ軸と等しく、
該方向性結合器を構成する光導波路は、基板全面に不純
物を拡散したうえにチャンネルとすべき部位以外の部位
に基板表面からイオン交換を施してあることを特徴とす
る導波路型光スイッチ。 ２）ニオブ酸リチウム結晶板に形成された互いに近接し
た２本のチャンネル光導波路からなる方向性結合器と該
方向性結合器の近傍に設置された電極よりなり、該方向
性結合器の光透過方向は、前記結晶板のＣ軸と等しく、
該方向性結合器を構成する光導波路は、チャンネルとす
べき部位のみに不純物が拡散され、さらに該部位以外の
部位に基板表面からイオン交換が施されていることを特
徴とする導波路型光スイッチ。[Claims] 1) A directional coupler consisting of two channel optical waveguides close to each other formed on a lithium niobate crystal plate, and an electrode installed near the directional coupler, The light transmission direction of the sexual coupler is equal to the C axis of the crystal plate,
A waveguide type optical switch characterized in that the optical waveguide constituting the directional coupler has impurities diffused over the entire surface of the substrate and ion exchange is performed from the surface of the substrate in areas other than the area to be used as a channel. 2) A directional coupler consisting of two channel optical waveguides close to each other formed on a lithium niobate crystal plate, and an electrode installed near the directional coupler, and light transmission through the directional coupler. the direction is equal to the C axis of the crystal plate,
The optical waveguide constituting the directional coupler is a waveguide-type optical waveguide characterized in that impurities are diffused only in a portion that should be a channel, and ion exchange is performed on other portions from the substrate surface. switch.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62098853A JPH0721595B2 (en) | 1987-04-21 | 1987-04-21 | Waveguide type optical switch |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62098853A JPH0721595B2 (en) | 1987-04-21 | 1987-04-21 | Waveguide type optical switch |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS63262625A true JPS63262625A (en) | 1988-10-28 |
| JPH0721595B2 JPH0721595B2 (en) | 1995-03-08 |
Family
ID=14230787
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62098853A Expired - Fee Related JPH0721595B2 (en) | 1987-04-21 | 1987-04-21 | Waveguide type optical switch |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0721595B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02226232A (en) * | 1989-02-28 | 1990-09-07 | Nec Corp | Directional coupler type optical switch |
| CN103424895A (en) * | 2012-05-21 | 2013-12-04 | 鸿富锦精密工业（深圳）有限公司 | Electro-optical modulator |
-
1987
- 1987-04-21 JP JP62098853A patent/JPH0721595B2/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02226232A (en) * | 1989-02-28 | 1990-09-07 | Nec Corp | Directional coupler type optical switch |
| CN103424895A (en) * | 2012-05-21 | 2013-12-04 | 鸿富锦精密工业（深圳）有限公司 | Electro-optical modulator |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0721595B2 (en) | 1995-03-08 |
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