JPH02310504A - Optical branching circuit - Google Patents
Optical branching circuitInfo
- Publication number
- JPH02310504A JPH02310504A JP13310889A JP13310889A JPH02310504A JP H02310504 A JPH02310504 A JP H02310504A JP 13310889 A JP13310889 A JP 13310889A JP 13310889 A JP13310889 A JP 13310889A JP H02310504 A JPH02310504 A JP H02310504A
- Authority
- JP
- Japan
- Prior art keywords
- optical waveguide
- optical
- waveguide
- optical branching
- incident light
- 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 111
- 239000012535 impurity Substances 0.000 claims abstract description 16
- 239000000758 substrate Substances 0.000 claims description 6
- 238000005452 bending Methods 0.000 abstract description 3
- 230000005855 radiation Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910003327 LiNbO3 Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
Landscapes
- Optical Integrated Circuits (AREA)
Abstract
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は光分岐回路、特に導波型光分岐回路に関する。[Detailed description of the invention] [Industrial application field] The present invention relates to an optical branch circuit, and particularly to a waveguide type optical branch circuit.
基板上に形成した光導波路により各種機能を実現する光
集積回路において、光分岐回路は最も基本的な光回路素
子の一つであり、光信号の分配、マツハツエン°ダー型
変調器、分岐型光スイッチ等に用いられる。Optical branch circuits are one of the most basic optical circuit elements in optical integrated circuits that realize various functions using optical waveguides formed on a substrate. Used for switches, etc.
以下Ｔｉ拡散ＬｉＮｂ０．光導波路を用いた対称２分岐
回路を例にとって従来例を説明する。第３図はこの光分
岐回路を示す斜視図である。ＬｉＮｂＯ３基板１上にＴ
ｉを拡散することにより屈折率を増加させ単一モード光
導波路を形成する。Below, Ti-diffused LiNb0. A conventional example will be explained by taking a symmetrical two-branch circuit using an optical waveguide as an example. FIG. 3 is a perspective view showing this optical branch circuit. T on LiNbO3 substrate 1
By diffusing i, the refractive index is increased and a single mode optical waveguide is formed.
入射光は光フアイバ直接結合あるいはレンズ結合により
光導波路端面６より入射光導波路２に入射される。入射
光導波路２を伝幡した光は２分岐部３で２つの光に分け
られ、それぞれ出射光導波路４．５を伝幡する。The incident light enters the incident optical waveguide 2 from the optical waveguide end face 6 by direct optical fiber coupling or lens coupling. The light propagated through the input optical waveguide 2 is split into two beams at the two-branch section 3, and each beam is transmitted through the output optical waveguide 4.5.
光分岐回路の過剰損失は２分岐の分岐角θ３に比例して
増加するためできるだけ小さな角度とする。さらに分岐
部分でのモード変換による過剰損失を低減するための手
段として分岐部分なテーバ構造としたり（Ｍａｓａｍｉ
ｔｓｕ Ｈａｒｕｎａ ｅｔ ａｌ：“Ｅｌｅｃｔｒｏ
ｏｐｔｉｃａｌ Ｂｒａｎｃｈｉｎｇ Ｗａｖｅｇ
ｕｉｄｅ ５ｗ１ｔｃｈｅｓ ａｎｄ ｔｈｅｉ
ｒ Ａｐｐｌｉｃａｔｉｏｎ ｔｏ １ｘ４０ｐ
ｔｉｃａｌＳｗｉｔｃｈｉｎｇ Ｎｅｔｗｏｒｋｓ″：
ＪｏｕｒｎａＩ ｏｆ Ｌｉｇｈｔｗａｖｅ Ｔｅｃ
ｈｎｏｌｏｇｙ、ｖｏｌ、ＬＴ−１，ＮＯ，１，Ｐ２２
３’８３）、モード結合型分岐とする（清野他； 「モ
ード結合型Ｙ分岐導波路」 ；昭和６１年度電子通信学
会光電波部門全国大会、講演番号２５０）などの報告が
ある。これらの方法により過剰損失０．３ ｄ Ｂ程度
の光分岐が得られている。Since the excess loss of the optical branching circuit increases in proportion to the branching angle θ3 of the two branches, the angle is made as small as possible. Furthermore, as a means to reduce excessive loss due to mode conversion at the branch section, a Taber structure is used at the branch section (Masami et al.
Tsu Haruna et al: “Electro
optical branching wave
uide 5w1tches and thei
r Application to 1x40p
ticalSwitching Networks”:
JournaI of Lightwave Tec
hnology, vol, LT-1, NO, 1, P22
3'83), and mode-coupled branching (Seino et al.; ``Mode-coupled Y-branch waveguide''; 1986 Institute of Electronics and Communication Engineers National Conference of Photo-Radio Division, Lecture No. 250). Optical branching with an excess loss of about 0.3 dB has been obtained by these methods.
従来の光分岐回路では分岐部分の過剰損失低減に重点が
置かれている。しかし光分岐回路では損失増加のため分
岐角θ３を大きくとれないので出射光導波路間の間隔を
広げるための曲がり光導波路が実用上必要不可欠である
。このため分岐部分は低損失であっても、回路を小型化
するために曲がり導波路の曲率半径を小さくし放射損失
が増加してしまうこともありうる。よって光分岐回路の
損失は分岐部のモード変換損失と曲がり光導波路の放射
損失の和として考えるべきである。よって光分岐回路ト
ータルの損失を低減する場合、曲がり部分と損失低減は
重要な問題となる。そして出射光導波路の曲がり部分で
は曲がりの曲率半径を大きくする、あるいは光導波路の
屈折率増加量を大きくすることにより光導波路内での光
閉じ込めを強くする等の方法により放射損失を低減でき
ることが知られている。In conventional optical branch circuits, emphasis is placed on reducing excess loss in the branch portion. However, in the optical branching circuit, the branching angle θ3 cannot be set large due to the increase in loss, so curved optical waveguides for widening the spacing between the output optical waveguides are practically indispensable. For this reason, even if the branch portion has low loss, the radius of curvature of the curved waveguide may be reduced in order to miniaturize the circuit, resulting in an increase in radiation loss. Therefore, the loss of an optical branch circuit should be considered as the sum of the mode conversion loss of the branch and the radiation loss of the curved optical waveguide. Therefore, when reducing the total loss of the optical branch circuit, bending portions and loss reduction become important issues. It is also known that radiation loss can be reduced by increasing the radius of curvature of the bend in the output optical waveguide, or by increasing the amount of increase in the refractive index of the optical waveguide to strengthen optical confinement within the optical waveguide. It is being
従来の光分岐回路を小型化するために曲がり導波路の曲
率半径を小さくした場合、曲がり部分での放射損失を低
減するために光導波路の光閉じ込め強さを大きくしなけ
ればならない。しかしこの場合、従来の光分岐回路では
入射光導波路も光閉じ込めの強さが大きくなり、入射端
面から入射した光が光導波路内で定常状態になるのに要
する距離は長くなる。もし入射光の伝播モードが定常状
態になる前に分岐するならば、分岐比が光の入射状態に
依存して変動するため安定な光分岐回路が得られない。When the radius of curvature of a curved waveguide is reduced in order to downsize a conventional optical branch circuit, the optical confinement strength of the optical waveguide must be increased to reduce radiation loss at the curved portion. However, in this case, in the conventional optical branching circuit, the intensity of light confinement in the incident optical waveguide also becomes large, and the distance required for the light incident from the incident end face to reach a steady state within the optical waveguide becomes long. If the propagation mode of the incident light branches before reaching a steady state, a stable optical branching circuit cannot be obtained because the branching ratio varies depending on the incident state of the light.
従って分岐°比を安定化するためには入射光導波路を十
分に長くとらなくてはならないことになる。つまり曲が
り部の長さを短縮するためには入射光導波路を長くしな
ければならないという矛盾が生じてしまう。Therefore, in order to stabilize the branching ratio, the input optical waveguide must be sufficiently long. In other words, a contradiction arises in that in order to shorten the length of the curved portion, the input optical waveguide must be lengthened.
本発明の光分岐回路は、基板に不純物を導入して形成し
た光導波路が、少なくとも１つの入射光導波路と、少な
くとも２つ以上に分かれる分岐部と、＝枝部に接続した
曲がり部を含む少なくとも２つ以上の出射光導波路とか
ら少くともなり、前記入射光導波路の前記不純物濃度を
前記出射光導波路における前記不純物濃度よりも低濃度
としたことを特徴とする構成になっている。In the optical branch circuit of the present invention, the optical waveguide formed by introducing impurities into a substrate includes at least one incident optical waveguide, at least a branch part that is divided into two or more parts, and a bent part connected to the branch part. There are at least two or more output optical waveguides, and the impurity concentration in the input optical waveguide is lower than the impurity concentration in the output optical waveguide.
本発明では出射光導波路の屈折率を増加させる不純物の
濃度を高くすることにより導波光を先導波路内に強く閉
じ込め、曲がり放射損失を低減させることができる、ま
た光分岐回路の入射光導波路の不純物濃度を低くするこ
とにより光の閉じ込め強さを弱くし出射光導波路と同一
の不純物濃度とした場合に比べより短距離で入射光が定
常状態になるようにする。つまり本発明によれば光分岐
回路の入射光導波路と出射光導波路との光閉じ込め強さ
を独立に最適化している。In the present invention, by increasing the concentration of impurities that increase the refractive index of the output optical waveguide, it is possible to strongly confine the guided light within the leading waveguide and reduce bending radiation loss. By lowering the concentration, the light confinement strength is weakened, and the incident light is brought into a steady state over a shorter distance than when the impurity concentration is the same as that of the output optical waveguide. That is, according to the present invention, the optical confinement strength of the input optical waveguide and the output optical waveguide of the optical branching circuit is independently optimized.
よって本発明により入射光導波路を短縮化しても安定な
分岐比が得られ、かつ曲がりの曲率半径を小さくするこ
とにより出射光導波路の長さを短縮しても低損失な導波
路構造が可能となり、低損失で小型な光分岐回路を実現
することができる。Therefore, according to the present invention, a stable branching ratio can be obtained even if the input optical waveguide is shortened, and by reducing the radius of curvature of the bend, a waveguide structure with low loss can be achieved even if the length of the output optical waveguide is shortened. , it is possible to realize a small optical branch circuit with low loss.
次に本発明の実施例について図面を参照して説明する。 Next, embodiments of the present invention will be described with reference to the drawings.
第１図は本発明の第１の実施例を示す斜視図である。FIG. 1 is a perspective view showing a first embodiment of the present invention.
２−カッ） Ｌ ｉ Ｎ ｂ ０３基板１上に以下の条
件でＴｉを拡散することにより光導波路を形成する。2-C) An optical waveguide is formed by diffusing Ti on the L i N b 03 substrate 1 under the following conditions.
分岐前の入射光導波路２の拡散前のＴｉ膜厚をｄ、＝５
００人とし、分岐後の出射光導波路４，５の拡散前のＴ
ｉ膜厚をｄ、＝８００人とする。両光導波路幅Ｗ＝８μ
ｍとし、１０５０℃・８時間空気雰囲気中で拡散を行う
。分岐前の入射光導波路２のＴｉ膜厚ｄ１は光の閉じ込
め強さが１次モードカットオフよりも十分に弱くなるよ
う設定されている。また分岐後の出射光導波路４，５の
Ｔｉ膜厚ｄ２は１次モードカットオフ近傍の閉じ込め強
さとなるように設定さ九ている。上記の条件によって作
製された光分岐回路において入射光導波路２では拡散さ
れたＴｉ濃度が低く光の閉じ込めか弱くなる。このため
入射光導波路２に入った光の伝播モード分布が最短距離
で定常状態になり安定な分岐比が得られる。また分岐後
の出射光導波路４，５ではＴｉ濃度が高く導波光の光閉
じ込めが強いため曲がり部分での放射損失を低減するこ
とができる。The Ti film thickness before diffusion of the incident optical waveguide 2 before branching is d, = 5
00 people, and T before diffusion of the output optical waveguides 4 and 5 after branching.
Let the film thickness of i be d, = 800 people. Both optical waveguide width W=8μ
m, and diffusion is performed in an air atmosphere at 1050° C. for 8 hours. The Ti film thickness d1 of the incident optical waveguide 2 before branching is set so that the light confinement strength is sufficiently weaker than the first-order mode cutoff. Further, the Ti film thickness d2 of the output optical waveguides 4 and 5 after branching is set so as to have a confinement strength near the first-order mode cutoff. In the optical branching circuit manufactured under the above conditions, the diffused Ti concentration in the incident optical waveguide 2 is low, and light confinement is weak. Therefore, the propagation mode distribution of the light that has entered the incident optical waveguide 2 becomes a steady state at the shortest distance, and a stable branching ratio can be obtained. Further, the output optical waveguides 4 and 5 after branching have a high Ti concentration and strong optical confinement of the guided light, so that radiation loss at the bent portion can be reduced.
このようにＴｉ濃度を変えることにより分岐への入射光
導波路と出社光導波路の光閉じ込め強さを最適化するこ
とができる。よって入射光導波路を短縮化しても安定な
分岐比が得られ、かつ出射光導波路の曲がりの曲率半径
を従来より小さくしても損失増加の無い先導波路構造が
可能となる。By changing the Ti concentration in this way, it is possible to optimize the optical confinement strength of the optical waveguide entering the branch and the optical waveguide exiting the branch. Therefore, even if the input optical waveguide is shortened, a stable branching ratio can be obtained, and even if the radius of curvature of the output optical waveguide is made smaller than before, it is possible to create a leading waveguide structure with no increase in loss.
これにより従来と同等の損失でより小型化な、あるいは
同等のサイズでより低損失な光分岐回路が実現できる。This makes it possible to realize a smaller optical branch circuit with the same loss as the conventional one, or an optical branch circuit with the same size and lower loss.
第２図は本発明の第２の実施例を示す斜視図である。FIG. 2 is a perspective view showing a second embodiment of the invention.
本実施例では入射光導波路２のＴｉ膜厚をｄ、、出射光
導波路４，５のＴｉ膜厚をｄ２と、第１のＱ
実施例と同じに分岐部３のＴｉ膜厚をｄｌからｄ２まで
テーパ状に変化させる。Ｔｉ膜厚テーバを１００〜２０
０人／ｍｍにすれば光導波路の屈折率変化によるモード
変換損失はほとんど発生せず（近藤他；、°屈折率差を
つけたＬｉＮｂ○、方向性結合型スイッチ′ ；第３１
回応用物理学関係連合講演会予稿集ｐ １１ ｇ）、よ
り低損失な光分岐回路を実現できる。In this example, the Ti film thickness of the input optical waveguide 2 is d, the Ti film thickness of the output optical waveguides 4 and 5 is d2, and the Ti film thickness of the branch part 3 is changed from dl to d2 as in the first example. Change in a tapered shape until. Ti film thickness Taber 100~20
If it is set to 0 people/mm, almost no mode conversion loss will occur due to changes in the refractive index of the optical waveguide (Kondo et al., LiNb with a difference in refractive index, directional coupling type switch'; No. 31
Proceedings of the Joint Conference on Regenerative Physics, p. 11 g), it is possible to realize an optical branch circuit with lower loss.
以上Ｔｉ拡散Ｌ ｉ Ｎ ｂ Ｏｓ光導波路の場合を例
によって説明したが他の石英系ガラス、半導体等の導波
路材料による不純物拡散型光導波路を用いて形成した光
分岐回路に本発明を適用した場合でも同様の効果を得ら
れる。The case of a Ti-diffused L i N b Os optical waveguide has been described above as an example, but the present invention can also be applied to optical branch circuits formed using impurity-diffused optical waveguides made of other waveguide materials such as silica-based glass and semiconductors. The same effect can be obtained in any case.
また光分岐回路をカスケードに多段接続する場合も本発
明を適用して、出射光導波路の不純物濃度を高くし、次
段の光分岐回路の入射光導波路の不純物濃度を低くする
ことにより分岐への入射光導波路と出射光導波路の光閉
じ込め強さを最適化することができる。よって入射光導
波路を短縮化しても安定な分岐比が得られ、かつ出射光
導波路の曲がりの曲率半径を従来より小さくしても損失
増加の無い光導波路構造が可能となる。The present invention can also be applied when optical branching circuits are connected in multiple stages in cascade, by increasing the impurity concentration of the output optical waveguide and lowering the impurity concentration of the input optical waveguide of the next stage optical branching circuit. The optical confinement strength of the input optical waveguide and the output optical waveguide can be optimized. Therefore, even if the input optical waveguide is shortened, a stable branching ratio can be obtained, and even if the radius of curvature of the output optical waveguide is made smaller than that of the conventional optical waveguide, an optical waveguide structure with no increase in loss can be achieved.
以上説明したように本発明によれば光分岐回路の入射光
導波路及び、出射光導波路の不純物濃度を変えることに
より光閉じ込め強さを独立に制御し、入射光導波路の分
岐比を安定化すると同時に出射光導波路では損失を低減
するという従来の光分岐回路では不可能であった効果が
得られる。これにより従来より大幅に小型・低損失で安
定な光分岐比が得られる光分岐回路を実現することがで
きる。As explained above, according to the present invention, the optical confinement strength is independently controlled by changing the impurity concentration of the input optical waveguide and the output optical waveguide of the optical branching circuit, and the branching ratio of the input optical waveguide is stabilized. The output optical waveguide can achieve an effect of reducing loss, which was not possible with conventional optical branching circuits. This makes it possible to realize an optical branching circuit that is much smaller, has lower loss, and provides a more stable optical branching ratio than conventional circuits.
第１図は本発明の第１の実施例を示す斜視図である。第
２図は本発明の第２の実施例を示す斜視図である。第３
図は従来の光分岐回路を示す斜視図である。
ｌ・・・・・・Ｌ ｉ ’Ｎ ｂ Ｏ３基板、２・・・
・・・入射光導波路、３・・・・・・分岐部、４・・・
・・・出射光導波路、６・・・・・・光導波路端面。
代理人 弁理士 内 原 音
４出吋光＃人Ｉか
第１ 図
橘２図FIG. 1 is a perspective view showing a first embodiment of the present invention. FIG. 2 is a perspective view showing a second embodiment of the invention. Third
The figure is a perspective view showing a conventional optical branch circuit. l...L i 'N b O3 substrate, 2...
...Incidence optical waveguide, 3... Branch part, 4...
. . . Output optical waveguide, 6 . . . Optical waveguide end surface. Agent Patent Attorney Uchihara Oto 4 Deku Hikari #Person I or 1 Figure Tachibana 2
Claims (1)
１つの入射光導波路と、少なくとも２つ以上に分かれる
分岐部と、前記分岐部に接続した曲がり部を含む少なく
とも２つ以上の出射光導波路とから少くともなり、前記
入射光導波路の前記不純物濃度を前記出射光導波路にお
ける前記不純物濃度よりも低濃度としたことを特徴とす
る光分岐回路。An optical waveguide formed by introducing impurities into a substrate includes at least one input optical waveguide, a branch part that is divided into at least two parts, and at least two or more output optical waveguides including a bent part connected to the branch part. An optical branching circuit characterized in that at least the impurity concentration in the input optical waveguide is lower than the impurity concentration in the output optical waveguide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1133108A JP2903543B2 (en) | 1989-05-26 | 1989-05-26 | Optical branch circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1133108A JP2903543B2 (en) | 1989-05-26 | 1989-05-26 | Optical branch circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02310504A true JPH02310504A (en) | 1990-12-26 |
| JP2903543B2 JP2903543B2 (en) | 1999-06-07 |
Family
ID=15097002
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1133108A Expired - Lifetime JP2903543B2 (en) | 1989-05-26 | 1989-05-26 | Optical branch circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2903543B2 (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62254018A (en) * | 1986-04-26 | 1987-11-05 | Hoya Corp | Wave guide type sensor |
| JPS6377009A (en) * | 1986-09-20 | 1988-04-07 | Fujitsu Ltd | Y-branch waveguide |
-
1989
- 1989-05-26 JP JP1133108A patent/JP2903543B2/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62254018A (en) * | 1986-04-26 | 1987-11-05 | Hoya Corp | Wave guide type sensor |
| JPS6377009A (en) * | 1986-09-20 | 1988-04-07 | Fujitsu Ltd | Y-branch waveguide |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2903543B2 (en) | 1999-06-07 |
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