JP2879849B2 - Striped laterally confined optical waveguide - Google Patents
Striped laterally confined optical waveguideInfo
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- JP2879849B2 JP2879849B2 JP63053113A JP5311388A JP2879849B2 JP 2879849 B2 JP2879849 B2 JP 2879849B2 JP 63053113 A JP63053113 A JP 63053113A JP 5311388 A JP5311388 A JP 5311388A JP 2879849 B2 JP2879849 B2 JP 2879849B2
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- layer
- optical waveguide
- refractive index
- core
- intermediate layer
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Description
【発明の詳細な説明】 〔概 要〕 基板上に形成される光導波路で,縦方向に光を閉じ込
めるコア層の一部分の中間に低屈折率中間層膜を挿入
し,光が感じる等価屈折率を制御して,中間層のある部
分の等価屈折率を中間層のない部分の等価屈折率より低
くすることによって,光を横方向に閉じ込めるようにし
た光導波路である。DETAILED DESCRIPTION OF THE INVENTION [Summary] An optical waveguide formed on a substrate, a low-refractive-index intermediate layer film is inserted in the middle of a part of a core layer that vertically confines light, and an equivalent refractive index felt by light. Is controlled so that the equivalent refractive index of the portion without the intermediate layer is lower than the equivalent refractive index of the portion without the intermediate layer, so that light is confined in the lateral direction.
本発明は,光導波路に関するものであり,特に光導波
路を多層化した三次元導波路構造を可能にするストライ
プ横閉じ込め光導波路に関するものである。The present invention relates to an optical waveguide, and more particularly to a stripe laterally confined optical waveguide that enables a three-dimensional waveguide structure in which an optical waveguide is multilayered.
一般に,半導体やガラスなど,ある特定の基板上に製
作する光導波路は,縦方向(膜厚方向)と横方向(基板
面に平行な方向)にそれぞれ何らかの光閉じ込め機構を
設けて,光を導波する。In general, an optical waveguide manufactured on a specific substrate such as a semiconductor or glass is provided with some light confinement mechanism in a vertical direction (thickness direction) and a horizontal direction (a direction parallel to the substrate surface) to guide light. Waves.
横方向には,例えばコア(光が通る層)とクラッドの
間の屈折率差による全反射を利用したものや,多層膜ク
ラッドの干渉反射を利用したものが一般的であり,様々
な屈折率をもつ透明な材料を連続的に積層することで容
易に製作できる。In the horizontal direction, for example, those using total reflection due to the refractive index difference between the core (layer through which light passes) and the cladding and those using interference reflection of the multilayer cladding are generally used. It can be easily manufactured by continuously laminating transparent materials having
一方,横方向にはフォトリソグラフィとエッチング技
術を組み合わせた様々な光閉じ込め法が考案されてい
る。On the other hand, in the lateral direction, various light confinement methods combining photolithography and etching techniques have been devised.
第6図は、従来のリッジ型光導波路の例を示してい
る。図において,1は半導体などの基板であり,2は基板1
上に形成されたクラッド層,3はクラッド層2上に形成さ
れクラッド層2よりも屈折率が高いコア層,4はコア層3
を膜厚方向に段差を生じるようにエッチングして形成し
たリッジ(うね部),5はリッジ4に沿って設けられた光
の線路である。FIG. 6 shows an example of a conventional ridge-type optical waveguide. In the figure, 1 is a substrate such as a semiconductor, and 2 is a substrate 1
The cladding layer 3 formed on the core layer 3 is formed on the cladding layer 2 and has a higher refractive index than the cladding layer 2.
The ridge (ridge), 5 formed by etching so that a step is formed in the film thickness direction, and 5 is a light line provided along the ridge 4.
第6図に示されたリッジ型光導波路では,コア層3の
膜厚を,リッジ4の部分とその周辺部分とで僅かに異な
らせたことにより,等価的な屈折率に差を生じさせて,
横方向の光閉じ込めを行っている。In the ridge type optical waveguide shown in FIG. 6, the thickness of the core layer 3 is made slightly different between the ridge 4 portion and the peripheral portion, thereby causing a difference in equivalent refractive index. ,
Light is confined in the horizontal direction.
第7図は,従来の矩形埋込型光導波路の例を示してい
る。図において,1は半導体などの基板,2はクラッド層,6
はクラッド層2よりも高い屈折率をもつコアデある。FIG. 7 shows an example of a conventional rectangular embedded optical waveguide. In the figure, 1 is a substrate such as a semiconductor, 2 is a cladding layer, 6
Is a core having a higher refractive index than the cladding layer 2.
コア6はクラッド層2上に形成した膜をストリップ状
に残してクラッド層2あるいは基板1までエッチングし
て形成され,その後ストリップ状のコアを低屈折率媒質
で埋込むことにより横方向の光閉じ込めが行われてい
る。The core 6 is formed by etching the clad layer 2 or the substrate 1 while leaving the film formed on the clad layer 2 in a strip shape, and thereafter embedding the strip-shaped core with a low-refractive index medium to confine light in the lateral direction. Has been done.
前述したリッジ型光導波路や矩形埋込型光導波路は,
従来多く用いられていたが,これらは一般にコア径が10
μm近い単一モード光ファイバとの高効率結合を考慮し
たとき,光導波路のコアの大きさもそれと同等にする必
要があり,その場合光横閉じ込めに必要なエッチング深
さも,数μmから10μm以上に及んでしまう。The above-mentioned ridge type optical waveguide and rectangular buried type optical waveguide
These have been widely used in the past, but these generally have a core diameter of 10
Considering high-efficiency coupling with a single-mode optical fiber close to μm, the size of the core of the optical waveguide needs to be the same, and in that case, the etching depth required for lateral confinement of the light is reduced from several μm to more than 10 μm. Reach.
これだけの厚さをエッチングするためには方向性をも
たない化学エッチングは不可能であり,近年急速に進歩
してきた反応性イオンビームエッチングなどの異方向性
ドライエッチング技術を用いる必要があるが,それでも
現状では低損失な光導波路を得るためにかなりの精度と
時間を要している。In order to etch such a thickness, chemical etching without directivity is impossible, and it is necessary to use an omnidirectional dry etching technique such as reactive ion beam etching, which has progressed rapidly in recent years. Nevertheless, at present, considerable precision and time are required to obtain a low-loss optical waveguide.
また今後は,光素子を高密度に集積化する上で,第8
図に示すような複数の光線路を膜厚方向に積層し,3次元
的に光信号のやり取りを行う積層導波型光集積回路の重
要性が増大するものと考えられる。簡単に図について説
明すると,30は半導体などの基板,31は光の入射ポート,3
2は光導波路,33は光の出射ポート,34は光合流・分岐回
路,35は上下方向の光結合回路,36は光検器である。しか
し前述したような光横閉じ込め法では,光導波路形成後
にその凹凸が表面に残ってしまうため,この方法で多段
に積層した光集積回路を構成することは不可能である。In the future, in order to integrate optical devices at a high density,
It is thought that the importance of a laminated waveguide type optical integrated circuit that stacks a plurality of optical lines as shown in the film thickness direction and exchanges optical signals three-dimensionally will increase. Briefly explaining the diagram, 30 is a substrate such as a semiconductor, 31 is a light incident port, 3
2 is an optical waveguide, 33 is a light emission port, 34 is an optical merging / branching circuit, 35 is a vertical optical coupling circuit, and 36 is an optical detector. However, in the lateral optical confinement method as described above, since the unevenness remains on the surface after the formation of the optical waveguide, it is impossible to form a multi-layered optical integrated circuit by this method.
本発明は,コア厚の大きい光導波路を横閉じ込めする
ときに要求されうエッチング精度を緩和し,従来の方法
に比べて極めて容易に製作でき,かつ表面に段差がほと
んど残らない光横閉じ込め光導波路を実現することを目
的とするものである。The present invention alleviates the etching accuracy required when laterally confining an optical waveguide having a large core thickness, and can be manufactured extremely easily as compared with the conventional method, and has almost no step on the surface. The purpose is to realize.
本発明は,光の線路となるコアの横方向において媒質
中に低い屈折率をもつ薄い中間層をストライプ状に設け
ることによって等価的に屈折率を低下させ,深いエッチ
ングを行う必要なしに光の横方向閉じ込めを実現するも
のである。The present invention reduces the refractive index equivalently by providing a thin intermediate layer having a low refractive index in a stripe shape in the medium in the lateral direction of the core serving as the optical line, thereby lowering the refractive index equivalently and eliminating the need for deep etching. This realizes lateral confinement.
第1図は,本発明によるストライプ横閉じ込め光導波
路の原理説明図である。FIG. 1 is a view for explaining the principle of a stripe laterally confined optical waveguide according to the present invention.
図において,11はクラッド層,12は光導波路のコア層,1
3はコア層12よりも屈折率が低い媒質の中間層,14はクラ
ッド層11に対向するクラッド層,15は光の線路となるコ
ア部である。また,Aは中間層が除去されている領域,Bは
中間層が存在する領域である。In the figure, 11 is the cladding layer, 12 is the core layer of the optical waveguide, 1
Reference numeral 3 denotes an intermediate layer of a medium having a lower refractive index than that of the core layer 12, reference numeral 14 denotes a cladding layer facing the cladding layer 11, and reference numeral 15 denotes a core portion serving as an optical line. A is a region where the intermediate layer has been removed, and B is a region where the intermediate layer exists.
第1図により,本発明の作用を説明する。 The operation of the present invention will be described with reference to FIG.
第1図の縦方向(膜厚方向)に積層した光導波路のコ
ア層12中には,領域Bに示されるような非常に薄い中間
層13が一層挟まれている。この中間層13は,コアに用い
られている材料よりも屈折率が低いため,光に作用する
等価屈折率をわずかに下げる働きをもつ。したがって中
間層13が除去されている領域Aとの間に横方向に等価的
な屈折率差が生じ,領域AとBの境界で光が全反射する
ため,光が領域Aの中に閉じ込められる。In the core layer 12 of the optical waveguide laminated in the vertical direction (film thickness direction) in FIG. 1, a very thin intermediate layer 13 as shown in a region B is sandwiched. Since the intermediate layer 13 has a lower refractive index than the material used for the core, it has a function of slightly reducing the equivalent refractive index acting on light. Therefore, an equivalent refractive index difference occurs in the lateral direction between the region A and the region A from which the intermediate layer 13 has been removed, and the light is totally reflected at the boundary between the regions A and B, so that the light is confined in the region A. .
この横閉じ込め法は,コア材料の一部が低屈折率媒質
に置き換わっているという点において従来のリッジ型光
導波路における横閉じ込め法と同じであるが,その低屈
折率媒質をコア層の中間に置いたことで,薄い層でもそ
の効果を数倍から10倍以上に大きくしている。This lateral confinement method is the same as the conventional ridge-type optical waveguide lateral confinement method in that a part of the core material is replaced by a low refractive index medium, but the low refractive index medium is placed in the middle of the core layer. The effect is increased by several to ten times or more even for thin layers.
したがって,本発明では,従来のリッジ型に比べてエ
ッチング深さが1/10程度と小さくて済み,化学エッチン
グで非常に手軽に経路パターンが形成できる。ここで形
成されるパターンは他の横閉じ込めのようにはっきりし
た段差(ストリップ)が形成されることがなく,2次元的
なストライプ(しま)に近いため,本発明ではこの横閉
じ込め法をストライプ横閉じ込めと呼んでいる。したが
って,エッチングによる段差が小さいため,最終的に表
面に残る段差を小さく抑えることができ,積層導波路型
光集積回路への応用が可能になる。Therefore, in the present invention, the etching depth can be reduced to about 1/10 as compared with the conventional ridge type, and the path pattern can be formed very easily by chemical etching. The pattern formed here does not form a distinct step (strip) like other lateral confinement and is close to a two-dimensional stripe (stripe). We call it confinement. Therefore, since the step due to the etching is small, the step finally remaining on the surface can be suppressed to be small, and application to a laminated waveguide type optical integrated circuit becomes possible.
本発明は,半導体,ガラスなどの基板上に形成された
あらゆる光導波路に適用可能であり,コアが単一モード
光ファイバと同程度に厚い場合に有効である。The present invention can be applied to any optical waveguide formed on a substrate such as a semiconductor or glass, and is effective when the core is as thick as a single mode optical fiber.
特に,第2図に示す共振反射型光導波路(通称ARRO
W)のように,単一モード導波路でありながらコア内の
光閉じ込めが強く,リッジなどの微小な外形変化しか与
えない加工では横方向の閉じ込め効果が得にくい導波路
に対しては,特に効果的と考えられる。このような共振
反射型光導波路で横閉じ込めを行った実施例を第3図に
示す。In particular, the resonant reflection type optical waveguide shown in FIG.
Especially for waveguides such as W), which have a strong optical confinement in the core even though they are single mode waveguides, and where it is difficult to obtain a lateral confinement effect by processing that gives only a small outer shape change such as a ridge. It is considered effective. FIG. 3 shows an embodiment in which lateral confinement is performed by using such a resonant reflection type optical waveguide.
第3図において,10は基板,11aは第1クラッド層,11b
は第2クラッド層,12はコア層,13は中間層,15はコア部
である。In FIG. 3, 10 is a substrate, 11a is a first cladding layer, 11b
Is a second cladding layer, 12 is a core layer, 13 is an intermediate layer, and 15 is a core portion.
また各層の屈折率と厚さを次のように表す。 The refractive index and thickness of each layer are represented as follows.
層 屈折率 厚 さ 基板 nS − 第1クラッド層 n1 d1 第2クラッド層 n2 d2 コア層 nC dC 中間層 n1C d1C ここで,共振反射型光導波路(ARROW)の構造上の特
性から,各層の屈折率間には,次のような関係が設定さ
れる。なおコア層の上部媒質(通常は空気)の屈折率を
n0とする。 Layer refractive index thickness substrate n S - wherein the first clad layer n 1 d 1 second cladding layer n 2 d 2 core layer n C d C intermediate layer n 1C d 1C, the structure of the resonant reflective optical waveguide (ARROW) From the above characteristics, the following relationship is set between the refractive indices of the respective layers. Note that the refractive index of the medium above the core layer (usually air)
Let n be 0 .
nC>n0 n1>nC n1>n2 nC≧n2 n2<nS さらに,本発明によるストライプ横閉じ込めを行う条
件として n1C<nC にされる。n C > n 0 n 1 > n C n 1 > n 2 n C ≧ n 2 n 2 <n S Furthermore, n 1C <n C is set as a condition for performing horizontal stripe confinement according to the present invention.
これにより,第2図に矢印で示されているように,コ
ア層に入射した光は,第2クラッド層の厚さを適切に設
定することにより生じる干渉反射により縦方向に閉じ込
められかつ横方向にも等価屈折率差による全反射により
閉じ込められて伝播する。As a result, as shown by arrows in FIG. 2, the light incident on the core layer is confined in the vertical direction by interference reflection caused by appropriately setting the thickness of the second cladding layer, and in the horizontal direction. Also, the light is confined and propagated by total reflection due to the equivalent refractive index difference.
第4図に,中間層の厚さd1Cをパラメータとしたと
き,コア層の表面からの中間層の位置Dと横方向等価屈
折率差ΔΩとの関係を示す。FIG. 4 shows the relationship between the position D of the intermediate layer from the surface of the core layer and the lateral equivalent refractive index difference ΔΩ when the thickness d 1C of the intermediate layer is used as a parameter.
第3図の実施例による横閉じ込めの設計の具体例とし
て,波長0.633μmに対してコア層12の厚さdCを4μm
とし,コア層12の材料に光導波路でよく用いられるC705
9ガラス(nC=1.54)を仮定したとき,第1クラッド層1
1aにTiO2,中間層13にSiO2(n1C=1.46)を用いれば,中
間層13の厚さd1Cが0.4μmと薄くても,横方向に0.25%
の等価屈折率差が得られる。As a specific example of the lateral confinement design according to the embodiment of FIG. 3, the thickness d C of the core layer 12 is set to 4 μm for a wavelength of 0.633 μm.
The material of the core layer 12 is C705, which is often used in optical waveguides.
Assuming 9 glasses (n C = 1.54), the first cladding layer 1
If TiO 2 is used for 1a and SiO 2 (n 1C = 1.46) is used for the intermediate layer 13, even if the thickness d 1C of the intermediate layer 13 is as thin as 0.4 μm, 0.25% in the horizontal direction
Is obtained.
なお,製作においては,クラッド層,コア層,中間層
などの各層の成膜にスパッタ法を,コア部15(領域A)
の中間層の除去にはBHF(緩衝フッ酸)エッチングを用
いた。エッチングの深さは数1000Å程度でよいため,製
作が容易である。In the production, a sputtering method was used for forming each layer such as a clad layer, a core layer, and an intermediate layer.
The intermediate layer was removed by BHF (buffered hydrofluoric acid) etching. Since the etching depth is only required to be several thousand mm, fabrication is easy.
また,本発明に基づくストライプ横閉じ込め光導波路
によれば,光導波路形成後,表面に残る段差が非常に小
さいので,基板上に1つの導波回路を形成した後,さら
にその上に分離層を挟んで別の導波回路を積層すること
が可能である。第5図はその1例であり,上下の導波路
が重なる部分に光信号をやり取りする光結合部を設ける
ことで,3次元的な積層導波路型光集積回路が構成でき
る。Also, according to the striped laterally confined optical waveguide according to the present invention, the step remaining on the surface after the formation of the optical waveguide is very small, so that after forming one waveguide circuit on the substrate, a separation layer is further formed thereon. It is possible to stack another waveguide circuit by sandwiching the same. FIG. 5 is an example of this, and a three-dimensional laminated waveguide type optical integrated circuit can be configured by providing an optical coupling section for exchanging optical signals in a portion where the upper and lower waveguides overlap.
第5図において,16は基板,17は基板と導波路を分離す
る干渉反射クラッド,18は下部導波路,19は上下の導波路
を分離する干渉反射クラッド,20は上部導波路,21および
22は中間層,23および24はコア部,25は光スイッチや変調
器などの光デバイスを示す。In FIG. 5, 16 is a substrate, 17 is an interference reflection cladding for separating the substrate and the waveguide, 18 is a lower waveguide, 19 is an interference reflection cladding for separating the upper and lower waveguides, 20 is an upper waveguide, 21 and
Reference numeral 22 denotes an intermediate layer, reference numerals 23 and 24 denote core portions, and reference numeral 25 denotes an optical device such as an optical switch or modulator.
このようにして,任意複数の導波路を多層化して三次
元構造とすることができる。In this way, an arbitrary plurality of waveguides can be multilayered to form a three-dimensional structure.
本発明によって,コア層が光ファイバのコアと同程度
の厚い導波路でも,深いエッチングを行わずに容易に屈
折率差を形成することができるため,光横閉じ込めが極
めて簡単に実現できる。また,導波路の表面の凹凸が小
さいため,積層導波路型光集積回路への応用が可能にな
る。According to the present invention, even if the core layer is as thick as the core of the optical fiber, the refractive index difference can be easily formed without performing deep etching, so that the light lateral confinement can be realized very easily. In addition, since the irregularities on the surface of the waveguide are small, it can be applied to a laminated waveguide type optical integrated circuit.
第1図は本発明の原理説明図,第2図は本発明を用いた
場合に特に大きな効果が得られる共振反射型光導波路の
説明図,第3図は本発明の1実施例である共振反射型光
導波路の構造図,第4図は中間層と横方向等価屈折率差
の関係説明図,第5図は本発明の実施例による積層導波
路型光集積回路の構造図,第6図は従来のリッジ型光導
波路の例の構造図,第7図は従来の矩形埋込型光導波路
の例の構造図,第8図は従来の積層導波路型光集積回路
の例の説明図である。 第1図中, 11:クラッド層 12:コア層 13:中間層 14:クラッド層 15:コア部FIG. 1 is an explanatory view of the principle of the present invention, FIG. 2 is an explanatory view of a resonant reflection type optical waveguide in which a particularly great effect is obtained when the present invention is used, and FIG. FIG. 4 is a view showing the relationship between the intermediate layer and the lateral equivalent refractive index difference, FIG. 5 is a view showing the structure of a laminated waveguide type optical integrated circuit according to an embodiment of the present invention, and FIG. FIG. 7 is a structural diagram of an example of a conventional ridge type optical waveguide, FIG. 7 is a structural diagram of an example of a conventional rectangular embedded optical waveguide, and FIG. 8 is an explanatory diagram of an example of a conventional laminated waveguide type optical integrated circuit. is there. In Fig. 1, 11: clad layer 12: core layer 13: intermediate layer 14: clad layer 15: core part
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.6,DB名) G02B 6/122 ──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. 6 , DB name) G02B 6/122
Claims (1)
(11)及びコア層(12)を備えるとともに,コア層(1
2)中に,基板(10)と並行な面内でストライプ畳に配
置した薄い中間層(13)を設け, 上記中間層(13)の屈折率をコア層(12)の屈折率より
も低くして,中間層(13)の近傍の媒質の等価的な屈折
率を低下させ,コア層(12)内を導波される光を基板
(10)に並行な面内で横方向に閉じ込めることを特徴と
するストライプ横閉じ込め光導波路。A cladding layer (11) and a core layer (12) sequentially formed on a substrate (10).
In 2), a thin intermediate layer (13) arranged in stripes in a plane parallel to the substrate (10) is provided, and the refractive index of the intermediate layer (13) is lower than the refractive index of the core layer (12). Then, the equivalent refractive index of the medium near the intermediate layer (13) is reduced, and the light guided in the core layer (12) is confined laterally in a plane parallel to the substrate (10). A striped laterally confined optical waveguide characterized by the following.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP63053113A JP2879849B2 (en) | 1988-03-07 | 1988-03-07 | Striped laterally confined optical waveguide |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP63053113A JP2879849B2 (en) | 1988-03-07 | 1988-03-07 | Striped laterally confined optical waveguide |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH01225904A JPH01225904A (en) | 1989-09-08 |
JP2879849B2 true JP2879849B2 (en) | 1999-04-05 |
Family
ID=12933742
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Application Number | Title | Priority Date | Filing Date |
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JP63053113A Expired - Fee Related JP2879849B2 (en) | 1988-03-07 | 1988-03-07 | Striped laterally confined optical waveguide |
Country Status (1)
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JP (1) | JP2879849B2 (en) |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
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JPS4924452A (en) * | 1972-06-28 | 1974-03-04 |
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1988
- 1988-03-07 JP JP63053113A patent/JP2879849B2/en not_active Expired - Fee Related
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JPH01225904A (en) | 1989-09-08 |
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