JP4059806B2 - Optical waveguide device including optical branching device, optical branching device, and optical waveguide device manufacturing method - Google Patents

Description

【００２９】
ただし、Ｒ¹、Ｒ²、Ｒ³はそれぞれ１価の炭化水素基、アルコキシ基、水素原子を、ｎ、ｍはそれぞれ０以上で、かつ、ｎ＋ｍは５以上の整数を表わす。
このようなポリシランは、一般に２５０ｎｍ以上の紫外領域に吸収を有し、酸素存在下で紫外光を照射するとそのケイ素−ケイ素（Ｓｉ−Ｓｉ）結合が一部切断され、シロキサン（Ｓｉ−Ｏ−Ｓｉ）結合やシラノール（Ｓｉ−ＯＨ）基に変換される。
これにより、ポリシランの紫外吸収が減少するとともに、親水性とアルカリ溶液に対する可溶性が発現される。
また、上記ポリシランは、紫外光を照射することにより、屈折率が低下するという特性もあり、光導波路を形成する上でも有用である。
以下にこの発明の実施例について図面に基づいて詳細に説明する。なお、以下に示す複数の実施例において、共通する部材には同じ符号を用いて説明する。
【００３０】
実施例１
図１は実施例１による光分岐素子の構成を概略的に示す断面図、図２は図１に示される光分岐素子の平面図、図３は図１および図２に示される光分岐素子の要部の斜視図である。
図１〜３に示されるように、実施例１による第１光分岐素子１と第２光分岐素子２は、基板３と、基板３上に形成された透光性の樹脂層４とを備え、樹脂層４は樹脂層４の表面から基板３の表面へ向かって所定の角度で下るように形成された傾斜面５を有し、傾斜面５は光を反射させるための反射膜６を有する反射領域５ａと、光を透過させるために反射膜６が形成されていない透過領域５ｂとをそれぞれ有している。
【００３１】
ここで、樹脂層４は、下部クラッド層７、コア層８および上部クラッド層９とから構成されている。コア層８には、コア層８の一部の屈折率を他の部分よりも相対的に高めることにより形成され光導波路として機能するコア８ａ，８ｂ，８ｃが形成されている。傾斜面５はコア８ｂ，８ｃの一端にそれぞれ形成されている。上部クラッド層９は傾斜面５を埋めるようにコア層８上に積層されている。また、反射膜６は金からなる金属薄膜である。
【００３２】
図１中のＡ地点からコア８ａに入射し、コア８ａ中を伝播して第１光分岐素子１に到達した光のうち、反射領域５ａ（図２および図３参照）に到達した光は図１中のＢの方向へ反射され、透過領域５ｂに到達した光は図１中のＥの方向へ向かってそのまま透過領域５ｂ（図２および図３参照）を透過する。
また、第１光分岐素子１の透過領域５ｂを透過した光は、コア８ｂ中を伝播して第２光分岐素子２に到達し、第１光分岐素子１と同様にして図１中のＣの方向とＥの方向に分岐される。
【００３３】
このようにして、第１および第２光分岐素子１，２に到達した光が、第１および第２光分岐素子１，２によってそれぞれ分岐される際の分岐比は、反射膜６が形成されている反射領域５ａと、反射膜６が形成されていない透過領域５ｂとの面積比でほぼ一義的に決定される。
このため、反射膜６の表面での反射率は、伝播する光のモードにかかわりなく略一定となり、光導波路としてのコア８ａ，８ｂ，８ｃがいわゆるマルチモード導波路であってもその分岐比は安定した値が得られる。
【００３４】
例えば、反射膜６が形成された反射領域５ａの反射率を９０％、反射膜６が形成されていない透過領域５ｂの透過率を１００％とすると、１：１の分岐比を実現するには、傾斜面５の面積のうち反射領域５ａの形成範囲を５２．６％、透過領域５ｂの形成範囲を４７．４％とすればよい。このとき、１つの光分岐素子あたりの吸収損失は５％であるので、実施例１のように第１および第２光分岐素子１，２を縦列に配置した場合の全体的な光利用効率は９０．３％となり、従来の金属膜によるハーフミラーに対して大幅に改善される。
なお、コア８ａ，８ｂ，８ｃは、第１および第２光分岐素子１，２が形成されている領域でそれぞれ途切れた状態となっているが、途切れた距離がコアの幅Ｗの２倍以内であれば、光の回折（広がり）による損失は問題とならない。
【００３５】
また、図２に示される第１および第２光分岐素子の間の距離Ｌは、次式に示す条件を満たすように設定するとよい。
Ｌ＞Ｄ×Ｗ／（２λ）
ここで、Ｗは透過領域５ｂの幅、Ｄはコア８ｂの幅、λはコア８ｂ内を伝播する光のうち、最小の波長を有する光の波長である。
上記の式による条件が満たされるように、第１および第２光分岐素子１，２間の距離Ｌを設定すると、第１光分岐素子１の透過領域５ｂを透過しコア８ｂに入射した光は、入射直後にはコア８ｂの中心付近にしか広がっていないが、次の第２光分岐素子２に到達するまでに回折効果によりコア８ｂの幅一杯に広がった状態となる。
【００３６】
例えば、透過領域５ｂの幅Ｗを１０μｍ、コア８ｂの幅Ｄを２０μｍ、コア８ｂを伝播する光のうち、最小の波長を有する光の波長λを０．８５μｍとすると、第１および第２光分岐素子１，２間の距離Ｌは、約１１８μｍより大きければよいこととなる。
これにより、第２光分岐素子２の本来の性能が発揮され、例えば、分岐比が変動しなくなるなどの効果が得られる。
なお、コア８ｂに入射した光は、前述の通り、その中に閉じ込められながら伝播するので、光がコア８ｂの幅Ｄを超えて分布することはない。
【００３７】
実施例２
図４はこの発明による光導波路素子の概略的な構成を示す断面図である。
図４に示されるように、実施例２による光導波路素子２０は、基板３と、基板３上に形成された透光性の樹脂層４と、樹脂層４中に互いに間隔を空けて形成された第１光分岐素子１および第２光分岐素子２と、第１および第２光分岐素子１，２間で光を伝播するように樹脂層４中に形成された細長い光導波路としてのコア８ｂを備え、第１および第２光分岐素子１，２は上述の実施例１による第１および第２光分岐素子１，２と同じ構成を有している。
【００３８】
ここで、樹脂層４は上述の実施例１と同様に下部クラッド層７、コア層８および上部クラッド層９から構成され、コア層８にはコア８ａ，８ｂ，８ｃが形成され、コア８ａの端部近傍にはコア層８の一部に形成された傾斜面５と、この傾斜面５上に形成された反射膜６からなるミラー２１が形成されている。
また、上部クラッド層９には、ミラー２１、第１光分岐素子１および第２光分岐素子２から上部クラッド層９の表面へそれぞれ立ち上がる垂直コア９ａ，９ｂ，９ｃが形成されている。
【００３９】
垂直コア９ａ，９ｂ，９ｃの上方には、樹脂層４上に形成された電極２２と、電極２２上に塗布されたはんだ２３を介して面発光レーザ２４、第１光検出器２５および第２光検出器２６がそれぞれ実装されている。
面発光レーザ２４から放射された光は、垂直コア９ａの端部から入射し垂直コア９ａ内を伝播してミラー２１に到達する。ミラー２１に到達した光は反射されることによりその光路が９０度変更されてコア８ａに入射し、コア８ａ内を伝播して第１光分岐素子１に到達する。第１光分岐素子１に到達した光は、第１光分岐素子１の分岐作用により垂直コア９ｂへ向かう方向とコア８ｂへ向かう方向との２つの方向に分岐される。
【００４０】
第１光分岐素子１によって分岐された光のうち、垂直コア９ｂへ向かう方向へ分岐された光は、垂直コア９ｂ内を伝播して垂直コア９ｂの端部から放射され、第１光検出器２５に受光されて電気信号に変換される。
一方、コア８ｂへ向かう方向へ分岐された光はコア８ｂ内を伝播して第２光分岐素子２に到達し、第２光分岐素子２の分岐作用により垂直コア９ｃへ向かう方向とコア８ｃへ向かう方向との２つの方向に分岐される。
【００４１】
第２光分岐素子２によって分岐された光のうち、垂直コア９ｃへ向かう方向へ分岐された光は、垂直コア９ｃ内を伝播して垂直コア９ｃの端部から放射され、第２光検出器２６に受光されて電気信号に変換される。
一方、コア８ｃへ向かう方向へ分岐された光は図示しない他の光分岐素子又はミラーへ向かってコア８ｃ内をさらに伝播する。
ここで、光分岐素子１，２の分岐比は、上述の通り、コアを伝播する光のモードに影響され難いので、コア８ａ，８ｂ，８ｃを、幅と厚さが共に２０μｍ程度ある大きなマルチモード導波路として形成することができる。
この結果、発光部の直径が約１０μｍ以上ある面発光レーザ２４からの光も効率よくコア８ａ，８ｂ，８ｃに導くことができる。
【００４２】
また、上部クラッド層９内に垂直コア９ａ，９ｂ，９ｃが形成されているので、垂直コア９ａの端部と面発光レーザ２４との間の距離、並びに、垂直コア９ｂ，９ｃの端部と第１および第２光検出器２５，２６の受光部との間の距離が短くなる。
このため、面発光レーザから放射された光を、広がりが小さい状態で垂直コア９ａへ入射させることができ、また、垂直コア９ｂ，９ｃの端部から放射された光を、広がりが小さい状態で第１および第２光検出器２５，２６に受光させることができ、結果として光の結合効率が向上する。
【００４３】
次に、実施例２による光導波路素子の製造方法について図５〜１８に基づいて説明する。図５〜７および図９〜１８は、図４に示される光導波路素子の製造工程を示す工程図であり、図８は光導波路素子の製造工程で用いられるグレーマスクの構成を示す説明図である。
【００４４】
まず、図５に示されるように、基板３上に下部クラッド層７を形成する。基板３には平滑性に優れるガラス基板、あるいは可撓性と耐熱性に優れるポリイミドフィルムを用いる。
下部クラッド層７は後で形成するコア層８より屈折率の低いものであればよいが、耐熱性（ガラス転移点約３５０℃以上）とスピンコートが可能な点からポリシラン（日本ペイント株式会社製、品名：グラシアＷＧ、品番：ＷＧ−００５）を用いる。耐熱性が約３００℃以上であれば、電子部品を実装する際のはんだ付け工程で変性可能性が小さくなり実装で有利である。
下部クラッド層７は、上記ポリシランを基板３上にスピンコートで塗布し、約３５０℃で焼成して化学的に安定な膜とすることにより形成される。
【００４５】
次に、図６に示されるように、下部クラッド層７の上にコア層８を形成する。コア層８には紫外光を照射することにより親水性と可溶性と屈折率変化とを示すポリシラン（日本ペイント株式会社製、品名：グラシアＷＧ、品番：ＷＧ−００４）を用いる。
ポリシランは、紫外光の照射により分子の一部が切断されて親水性を示すようになるのと同時に、アルカリ溶液に可溶となり、さらに屈折率が低下する。また、耐熱性の点からも好ましい。
但し、下部クラッド層７との屈折率差を確保するため、下部クラッド層７を構成するポリシランとは組成の異なるものを用いている。
コア層８は、上記ポリシランを下部クラッド層７上にスピンコートで塗布し、約２５０℃に加熱して膜中の溶剤を揮発させることにより形成される。
【００４６】
次に、図７に示されるように、グレーマスク３０を介してコア層８に紫外光を照射する。グレーマスク３０は、図８に示されるように透明基体３０ａと遮光膜３０ｂとからなり、遮光膜３０ｂは傾斜面５と対応する箇所において光透過率を漸減させるために膜厚が徐々に変化する光透過部３０ｃと、光透過部３０ｃと隣接する開口部３０ｄとを有している。
紫外光を照射することによるポリシランの化学変化（親水性と可溶性と屈折率変化の発現）は、照射される紫外光の強度に応じてコア層８の表面より厚み方向に向かって進行する。
このため、光透過部３０ｃを介して紫外光が照射された部分では、光透過部３０ｃの膜厚の変化に応じて化学変化が進行し、結果としてコア層８に傾斜面５の立体的な潜像を有する露光領域３１が形成される。
【００４７】
次に、図９に示されるように、得られた基板３をアルカリ溶液に浸漬し、紫外光の照射により親水性と可溶性と屈折率変化とが発現した露光領域３１（図７参照）を除去し傾斜面５を有する凹部３２を形成する。
【００４８】
次に、図１０（ａ）および図１０（ｂ）に示されるように、得られた基板３を無電解めっき法でめっき浴する。この際、凹部３２の内面には先の工程での紫外線照射により生じた親水基が残存するので、凹部３２の内面にのみ金属めっきが施され、反射膜６が形成される。
この工程では、傾斜面５と対向する凹部の内面にも反射膜６が形成されるが、これは光の伝播の妨げとなるので、この部分の反射膜６を次以降の工程で除去する。
【００４９】
すなわち、図１１（ａ）および図１１（ｂ）に示されるように、コア層４上にレジスト３３を塗布し、フォトリソグラフィーにより開口３４ａ，３４ｂ，３４ｃをそれぞれ形成して除去すべき反射膜６を露出させる。
開口３４ａは、傾斜面５を覆いつつ傾斜面５との対向面に形成された反射膜６を露出させるように形成され、開口３４ｂ，３４ｃは傾斜面５との対向面に形成された反射膜６と、傾斜面５に形成された反射膜６の中央部とを露出させるようにＴ字形に形成される。
【００５０】
次に、図１２（ａ）および図１２（ｂ）に示されるように、得られた基板３をエッチング液に浸漬し、不要な反射膜６（図１１（ａ）および図１１（ｂ）参照）を除去する。
次に、図１３（ａ）および図１３（ｂ）に示されるように、コア層８上に残るレジスト３３（図１２（ａ）および図１２（ｃ）参照）を有機溶剤で溶解除去する。
【００５１】
次に、図１４（ａ）および図１４（ｂ）に示されるように、コア層８に光導波路としてのコア８ａ，８ｂ，８ｃを形成するため、コア８ａ，８ｂ，８ｃに対応するパターンの遮光膜３５ｂを備えたマスク３５を介して紫外光を照射する。
すなわち、コア層８を構成するポリシランは、紫外光を照射することにより屈折率が低下するので、コア層８のうち、コア８ａ，８ｂ，８ｃとしない部分に紫外光を照射して屈折率を低下させ、コア８ａ，８ｂ，８ｃとすべき部分の屈折率を相対的に高め、コア８ａ，８ｂ，８ｃを形成するのである。
【００５２】
次に、図１５に示されるように、コア層８を約３５０℃で焼成して化学的に安定させる。
この際、コア層８の屈折率は全体的に低下するが、先の工程での紫外光照射によって生じた屈折率差はほぼそのまま維持され、また、コア層８全体の屈折率はいずれの部分についても下部クラッド層７より高く維持される。
次に、図１６に示されるように、コア層８上に上部クラッド層９を形成する。上部クラッド層９は、コア層８を構成するポリシランと同じポリシランをスピンコートで塗布し、約２５０℃に加熱して膜中の溶剤を揮発させることにより形成される。
【００５３】
次に、図１７（ａ）および図１７（ｂ）に示されるように、傾斜面５の上方と対応する箇所にのみ遮光膜３６ｂを備えたマスク３６を介して紫外光を上部クラッド層９に照射し、照射部分の屈折率を低下させて垂直コア９ａ，９ｂ，９ｃとすべき部分の屈折率を相対的に高めることにより上部クラッド層９内に垂直コア９ａ，９ｂ，９ｃを形成する。
次に、図１８（ａ）および図１８（ｂ）に示されるように、上部クラッド層９を約３５０℃で焼成して化学的に安定させる。
その後、面発光レーザ２４や第１および第２光検出器２５，２６を搭載するための電極２２を上部クラッド層９上に形成し、面発光レーザ２４や第１および第２光検出器２５，２６をそれぞれ電極にはんだ付けすることにより図４に示される光導波路素子２０が完成する。
【００５４】
【発明の効果】
この発明に係る光導波路素子によれば、第１および第２光分岐素子の傾斜面が光を反射させるための反射膜を有する反射領域と、光を透過させるために反射膜が形成されていない透過領域とを有するので、透過させるべき光を第１および第２光分岐素子の透過領域に直接到達させて透過させることができ、光の吸収損失を極力抑えることができる。
さらに、光導波路は断面が方形状で基板と平行な方向に延びて一定の幅と高さを有し、第１および第２光分岐素子の傾斜面は光導波路の両端面と一致する幅と高さをそれぞれ有して光導波路に光学的に接続され、第１光分岐素子の透過領域は幅Ｗを有するスリット状で、光導波路の幅をＤ、光導波路内を伝播する光の波長をλとするとき、第１および第２光分岐素子間の距離Ｌは、Ｌ＝Ｄ×Ｗ／（２λ）で表される距離Ｌよりも長く設定されるので、第１光分岐素子の透過領域を透過した直後では光導波路の一部にしか広がっていなかった光が、第２光分岐素子に到達するまでには回折効果により光導波路の幅一杯に広がった状態となり、第２光分岐素子における分岐比は光の伝播モードに係わりなく反射領域と受光領域の面積比でほぼ一義的に決定されるので、光の伝播モード変化の影響を受けることなく安定した分岐比が得られる。
【図面の簡単な説明】
【図１】この発明の実施例１による光分岐素子の構成を概略的に示す断面図である。
【図２】図１に示される光分岐素子の平面図である。
【図３】図１に示される光分岐素子の要部の斜視図である。
【図４】この発明の実施例２による光導波路素子の構成を概略的に示す断面図である。
【図５】図４に示される光導波路素子の製造工程を示す工程図である。
【図６】図４に示される光導波路素子の製造工程を示す工程図である。
【図７】図４に示される光導波路素子の製造工程を示す工程図である。
【図８】図４に示される光導波路素子の製造工程で用いられるグレーマスクの構成を概略的に示す説明図である。
【図９】図４に示される光導波路素子の製造工程を示す工程図である。
【図１０】図４に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１１】図４に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１２】図４に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１３】図４に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１４】図４に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１５】図４に示される光導波路素子の製造工程を示す工程図である。
【図１６】図４に示される光導波路素子の製造工程を示す工程図である。
【図１７】図４に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１８】図４に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１９】従来の光信号伝送システムの構成を概略的に示す説明図である。
【符号の説明】
１・・・第１光分岐素子
２・・・第２光分岐素子
３・・・基板
４・・・樹脂層
５・・・傾斜面
５ａ・・・反射領域
５ｂ・・・透過領域
６・・・反射膜
７・・・下部クラッド層
８・・・コア層
８ａ，８ｂ，８ｃ・・・コア
９・・・上部クラッド層
９ａ，９ｂ，９ｃ・・・垂直コア
２０・・・光導波路素子
２１・・・ミラー
２２・・・電極
２３・・・はんだ
２４・・・面発光レーザ
２５・・・第１光検出器
２６・・・第２光検出器
３０・・・グレーマスク
３０ａ・・・透明基体
３０ｂ，３５ｂ，３６ｂ・・・遮光膜
３０ｃ・・・光透過部
３０ｄ・・・開口部
３１・・・露光領域
３２・・・凹部
３３・・・レジスト
３４ａ，３４ｂ，３４ｃ・・・開口
３５，３６・・・マスク
Ｄ・・・コアの幅
Ｌ・・・第１および第２光分岐素子間の距離
Ｗ・・・透過領域の幅[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical branching device, an optical waveguide device including the optical branching device, and a manufacturing method thereof, and more particularly to an optical branching device for branching light transmitted from the optical waveguide and a manufacturing method thereof.
[0002]
[Prior art]
In order to realize a computer that performs faster arithmetic processing, the number of clocks of the CPU tends to increase year by year, and now a frequency around GHz has appeared.
As a result, there is a portion where a high-frequency signal flows in the electrical wiring of copper on the printed circuit board in the computer, and malfunction occurs due to the generation of noise. In addition, electromagnetic waves are radiated and the surroundings are affected.
[0003]
In order to solve such a problem, a method of using an optical signal instead of an electric signal by replacing a part of the electric wiring by copper on the printed board with an optical wiring by an optical waveguide is being actively tried now. . Since optical signals do not cause so-called electromagnetic induction, there are few malfunctions due to noise as described above.
[0004]
As an optical wiring by a conventional optical waveguide, for example, an optical signal transmission system in which light emitted from a light emitting element is received by a plurality of light receiving elements as shown in FIG. 19 is known (for example, see Patent Document 1). ).
As shown in FIG. 19, the conventional optical signal transmission system is configured by stacking optical waveguides in two layers in the thickness direction of the substrate. The first layer components in contact with the substrate 101 are the first layer cladding 102, the first layer core 103, and the first layer mirror layer 104, and the second layer components thereon are the second layer core 106, A second mirror layer 107 and a second cladding 108. Two light receiving elements 109 are arranged on the second layer clad 108.
[0005]
Since the first-layer mirror layer 104 and the second-layer mirror layer 107 are formed in a ridge like the first-layer core 103 and the second-layer core 106, they themselves function as the core of the optical waveguide. Further, end surfaces of the first mirror layer 104 and the second mirror layer 107 are reflection surfaces 105 having an inclination angle of 45 degrees with respect to the substrate 101. These reflecting surfaces 105 are half mirrors, and divide half of the incident light in the straight direction and divide half in the orthogonal direction by reflection. By generating such beam splitting action and waveguide by the mirror layer at various parts in the optical signal transmission system, optical coupling between different layers and light reception by a plurality of light receiving elements 109 are possible.
[0006]
Another conventional technique related to the present invention is a method of manufacturing an electric circuit board, in which a polysilane film is formed on the surface of the board, and a mask having openings corresponding to the circuit pattern in the polysilane film. The exposed part is made hydrophilic by irradiating it with UV light, and a palladium salt solution is attached to the exposed exposed part to form a pattern made of palladium salt on the exposed part, and this pattern is subjected to metal plating. A method of manufacturing an electric circuit board to be a conductive pattern is known (see, for example, Patent Document 2).
[0007]
In addition, as another conventional technique related to the present invention, a technique is known in which the polysilane compound is irradiated with ultraviolet light to reduce the refractive index of the irradiated portion in accordance with the amount of irradiation (for example, non-patent literature). 1).
[0008]
[Patent Document 1]
JP 2000-47044 A
[Patent Document 2]
Japanese Patent Laid-Open No. 10-326957
[Non-Patent Document 1]
Akihiro Hori, 1 other, “Examination of optical waveguide technology using photobleaching polymer materials”, Proceedings of 12th Microelectronics Symposium, October 2002, pp. 223-226
[0009]
[Problems to be solved by the invention]
In general, the half mirror is formed of an extremely thin metal thin film (thickness of 100 mm or less) or a multilayer dielectric film. However, when a metal thin film is used, the light use efficiency is reduced by the absorption loss that occurs when light passes through the half mirror.
As the metal thin film, a titanium thin film is often used. In this case, if the transmittance and the reflectance are set to be the same, an absorption loss occurs about 40%, and the transmittance and the reflectance are about 30%, respectively.
Therefore, when two half mirrors using a titanium thin film are arranged in tandem, the light use efficiency is 36% or less.
[0010]
On the other hand, the multilayer dielectric film has an absorption loss of almost 0%. However, since the multilayer dielectric film is formed by stacking about 4 to 10 thin films having different refractive indexes, vacuum deposition needs to be repeated many times in the manufacturing process, and the workability is poor.
Multilayer dielectric films exhibit different transmittance and reflectance depending on the mode of light propagating through the optical waveguide. When this is used for a multimode waveguide, the branching ratio is dynamically changed by the optical power transfer between modes. There is a problem that changes.
[0011]
Even if the half mirror is formed of a metal film or a multilayer dielectric film, it is necessary to change the thickness and configuration of the film in order to change the branching ratio. Therefore, in order to form a plurality of optical branching elements having different branching ratios in one optical waveguide element, it is necessary to repeat the process of forming the optical branching element a plurality of times, resulting in poor productivity.
[0012]
  The present invention has been made in view of the above circumstances, and has a small light absorption loss.LightAn optical waveguide element comprising a branch element, andOptical branching element and optical waveguide elementThe manufacturing method of this is provided.
[0013]
[Means for Solving the Problems]
  The present invention includes a substrate, a translucent resin layer formed on the substrate, a first optical branching element and a second optical branching element formed in the resin layer at intervals, and the first and first optical branching elements. An elongated optical waveguide formed in the resin layer so as to propagate light between the two optical branch elements, and the first and second optical branch elements are:An inclined surface formed so as to descend at a predetermined angle from the surface of the resin layer toward the surface of the substrate, the inclined surface has a reflective region having a reflective film for reflecting light, and for transmitting light The optical waveguide has a rectangular cross section, extends in a direction parallel to the substrate, has a certain width and height, and is inclined by the first and second optical branching elements. The surface has a width and a height that match the both end faces of the optical waveguide, and is optically connected to the optical waveguide. The transmission region of the first optical branching element is a slit having a width W, and the width of the optical waveguide is reduced. D, when the wavelength of light propagating in the optical waveguide is λ, the distance L between the first and second optical branching elements is longer than the distance L represented by L = D × W / (2λ)An optical waveguide device is provided.
  That is, according to this inventionFirst and second provided in the optical waveguide deviceThe light branching element includes a reflective region having a reflective film for reflecting light on an inclined surface, and light.Make transparentForNo reflection film is formed on the transmissionAnd having a region.
  For this reason, the light that should be transmittedFirst and secondOptical branching elementTransparentThe light can be directly transmitted to the region and light absorption loss can be suppressed as much as possible.
  Also,First and secondThe branching ratio by the optical branching element isTransparentSince it is determined almost uniquely by the area ratio of the region, it is hardly affected by changes in the propagation mode of light and can be applied to a multimode waveguide.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
  According to this inventionOptical waveguide deviceA substrate and a translucent resin layer formed on the substrateThe first and second light branching elements formed at intervals in the resin layer, and the elongate formed in the resin layer so as to propagate light between the first and second light branching elements With optical waveguideWithThe first and second optical branching elements are:It has an inclined surface formed so as to descend at a predetermined angle from the surface of the resin layer toward the surface of the substrate, and the inclined surface has a reflection region having a reflection film for reflecting light, and light.Transmission without reflection film for transmissionTerritory and haveThe optical waveguide has a square cross section, extends in a direction parallel to the substrate, has a certain width and height, and the inclined surfaces of the first and second optical branching elements have a width coincident with both end faces of the optical waveguide. The first optical branching element has a slit shape with a width W, the width of the optical waveguide is D, and the wavelength of the light propagating in the optical waveguide is optically connected to the optical waveguide. When λ, the distance L between the first and second optical branching elements is longer than the distance L represented by L = D × W / (2λ)It is characterized by that.
[0015]
  Here, for example, a glass substrate excellent in smoothness or a polyimide film excellent in flexibility and heat resistance can be used as the substrate.
  Moreover, as a translucent resin layer, the optical branching element mentioned later is mentioned.And optical waveguide elementsAs touched in the manufacturing method ofOptical branching elementFormation of inclined surface and reflective filmAnd fabrication of optical waveguidesFrom the viewpoint of facilitating, for example, solubility and hydrophilicity by light irradiationAnd refractive index changeCan be used.
  Further, the inclined surface is not particularly limited as long as it is formed so as to descend at a predetermined angle from the surface of the resin layer toward the surface of the substrate.
[0016]
  In addition, as the reflective film, for example, a metal film having a thickness of about 0.01 to 1 μm can be used, and as a material of the metal film, for example, gold or the like can be used.
  Also according to this inventionFirst and second provided in the optical waveguide deviceIn the light branching element, the reflection region means a region on the inclined surface where a reflection film for reflecting light is formed, and the shape and size thereof are not particularly limited.
  Also according to this inventionFirst and second provided in the optical waveguide deviceIn the optical branching element,TransparentAn area is an inclined surfaceFormed in a slit shapeMeans an area where no reflective film is formedTo do.
[0018]
  MaIn the optical waveguide device according to the present invention, the optical waveguide means a path of the optical signal that confines and propagates the optical signal, and can be constituted by, for example, a portion having a high refractive index formed in the resin layer.
  If a part having a higher refractive index than other parts is formed in the resin layer, an optical signal incident on the part having a higher refractive index will propagate through the interface while being totally reflected at the interface with the part having a lower refractive index. .
[0019]
  In the optical waveguide device according to the present invention, the optical waveguide is a substrate having a square cross section.WhenIn parallel directionExtendConstant widthAnd heightAnd the inclined surfaces of the first and second optical branching elements coincide with both end faces of the optical waveguide.widthWhenheightEachTheOptically connected to the optical waveguideThe
[0020]
  In such a configuration, the first optical branching elementTransparentThe area is slit-shaped with a width WAnd lightWhen the width of the waveguide is D and the wavelength of light propagating in the optical waveguide is λ, the distance L between the first and second optical branching elements is:
L = D × W / (2λ)
Longer than the distance L represented byIs set.
[0021]
  Because slit-shapedTransparentWhen the region is provided so as to cross the center of the inclined surface in a direction perpendicular to the substrate,TransparentThe light that has just passed through the area is the firstOptical branching elementIt spreads only in the vicinity of the center of the part of the optical waveguide adjacent to the part.
  However, if the distance between the first and second optical branching elements is set as described above, the light that has spread only in the vicinity of the center of the optical waveguide reaches the next second optical branching element due to the diffraction effect. The optical waveguide is expanded to the full width.
  Thereby, the original performance of the second optical branching element is exhibited, and for example, an effect such that the branching ratio is not changed is obtained.
  As described above, since the optical waveguide confines and propagates the light, even if the light transmitted through the first optical branching element propagates more than the distance L, the light is not distributed beyond the width D of the optical waveguide.
[0022]
  In addition, the present invention is viewed from another viewpoint.,lightA process of forming a resin layer by applying a translucent resin that expresses hydrophilicity and solubility upon irradiation to a substrate, and light is applied to the resin layer through a mask having a region where the light transmittance continuously changes. Irradiation to develop hydrophilicity and solubility in a part of the resin layer, dissolving and removing a part of the resin layer in which solubility has been developed to form an inclined surface, and a surface of the inclined surface having hydrophilicity The process of forming the reflective film by electroless plating and removing a part of the reflective film by etchingTransmission without reflection filmArea andHas a reflective filmAnd a step of forming a reflection region.
[0023]
According to such a manufacturing method, when forming the inclined surface, a step (exposure step) in which a part of the resin layer on which the inclined surface is to be formed is irradiated with light to develop hydrophilicity and solubility, and the solubility is expressed. The inclined surface can be easily formed in two steps including a step (development step) of dissolving and removing the formed portion.
Further, since the formed inclined surface exhibits hydrophilicity, a reflective film can be easily formed on the inclined surface by performing electroless plating (plating step).
[0024]
  That is, in the above manufacturing method, the light branching element can be formed by only three steps of the exposure step, the development step, and the plating step, and these steps can be processed in the atmosphere and are chemical reaction processing. Production can be easily expanded, which is advantageous from the viewpoint of manufacturing cost.
  Further, as described above, the branching ratio of the optical branching element manufactured by such a manufacturing method is as follows:TransparentSince the area ratio with the region is almost uniquely determined, the branching ratio can be arbitrarily set depending on the design of the mask used in the process of removing a part of the reflective film, and a plurality of branching ratios differ depending on the mask design. It is possible to simultaneously form the optical branching elements.
[0025]
  In addition, the present invention is viewed from another viewpoint.,lightA step of forming a resin layer by applying a translucent resin that exhibits hydrophilicity, solubility, and refractive index change upon irradiation to the substrate; and a resin layer comprising the first optical branch element, the second optical branch element, and the optical waveguide. A step of forming the first and second light branching elements in the resin layer by irradiating the resin layer with light through a mask having a region where the light transmittance changes continuously. A step of developing hydrophilicity and solubility in a part, a step of dissolving and removing a part of the resin layer in which solubility is expressed to form an inclined surface, and a reflective film by electroless plating on the surface of the inclined surface having hydrophilicity And a part of the reflective film is removed by etching.Transmission without reflection filmArea andHas a reflective filmThe step of forming an optical waveguide includes a step of forming a reflection region, and the step of forming an optical waveguide includes a step of irradiating the resin layer with light through a mask corresponding to the pattern of the optical waveguide to cause the resin layer to exhibit a refractive index change. The manufacturing method of this is provided.
[0026]
According to such a manufacturing method, when forming an optical waveguide, the resin layer is irradiated with light through a mask corresponding to the pattern of the optical waveguide, and a change in refractive index is expressed in the irradiated portion. Thus, an optical waveguide can be easily formed.
[0027]
Here, as the resin used in the method for manufacturing the optical branching element or the method for manufacturing the optical waveguide element, for example, what is generally called a photobleaching polymer material can be used.
Specific examples of the photobleaching polymer material include photobleachable polysilane (hereinafter simply referred to as “polysilane”).
The polysilane is an organosilicon polymer having a structure in which five or more silicon atoms are continuously connected. Specifically, the polysilane is a polymer having a structure as shown in Chemical Formula 1 below.
[0028]
[Chemical 1]

[0029]
However, R¹, R², R^ThreeEach represents a monovalent hydrocarbon group, alkoxy group or hydrogen atom, n and m each represents an integer of 0 or more, and n + m represents an integer of 5 or more.
Such a polysilane generally has an absorption in an ultraviolet region of 250 nm or more, and when irradiated with ultraviolet light in the presence of oxygen, the silicon-silicon (Si-Si) bond is partially broken to form siloxane (Si-O-Si). ) Converted to a bond or a silanol (Si-OH) group.
Thereby, the ultraviolet absorption of polysilane is reduced, and hydrophilicity and solubility in an alkaline solution are expressed.
In addition, the polysilane has a characteristic that its refractive index decreases when irradiated with ultraviolet light, and is also useful in forming an optical waveguide.
Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, in the several Example shown below, it demonstrates using the same code | symbol for a common member.
[0030]
Example 1
  1 is a cross-sectional view schematically showing a configuration of an optical branching element according to a first embodiment, FIG. 2 is a plan view of the optical branching element shown in FIG. 1, and FIG. 3 is an optical branching element shown in FIGS. It is a perspective view of the principal part.
  As shown in FIGS. 1 to 3, the first optical branch element 1 and the second optical branch element 2 according to the first embodiment include a substrate 3 and a translucent resin layer 4 formed on the substrate 3. The resin layer 4 has an inclined surface 5 formed so as to descend at a predetermined angle from the surface of the resin layer 4 toward the surface of the substrate 3, and the inclined surface 5 has a reflective film 6 for reflecting light. Reflection area 5a and lightTransmission without reflection film 6 formed for transmissionEach has a region 5b.
[0031]
Here, the resin layer 4 includes a lower clad layer 7, a core layer 8, and an upper clad layer 9. The core layer 8 is formed with cores 8a, 8b, and 8c that are formed by raising the refractive index of a part of the core layer 8 relative to other parts and function as an optical waveguide. The inclined surface 5 is formed at one end of each of the cores 8b and 8c. The upper cladding layer 9 is laminated on the core layer 8 so as to fill the inclined surface 5. The reflective film 6 is a metal thin film made of gold.
[0032]
  Of the light that enters the core 8a from the point A in FIG. 1 and propagates through the core 8a and reaches the first optical branching element 1, the light that reaches the reflection region 5a (see FIGS. 2 and 3) is shown in FIG. Reflected in the direction of B in 1.TransparentThe light that has reached the region 5b remains in the direction of E in FIG.TransparentThe region 5b (see FIGS. 2 and 3) is transmitted.
  Also, the first optical branching element 1TransparentThe light transmitted through the region 5b propagates through the core 8b, reaches the second optical branching element 2, and is branched in the directions C and E in FIG. .
[0033]
  In this way, the reflection film 6 is formed in the branching ratio when the light reaching the first and second optical branching elements 1 and 2 is branched by the first and second optical branching elements 1 and 2, respectively. The reflective area 5a and the reflective film 6 are not formedTransparentThe area ratio with the region 5b is determined almost uniquely.
  For this reason, the reflectance at the surface of the reflective film 6 is substantially constant regardless of the mode of propagating light, and even if the cores 8a, 8b, 8c as optical waveguides are so-called multimode waveguides, the branching ratio is A stable value is obtained.
[0034]
  For example, the reflectance of the reflective region 5a where the reflective film 6 is formed is 90%, and the reflective film 6 is not formed.TransparentAssuming that the transmittance of the region 5b is 100%, in order to realize a branching ratio of 1: 1, the reflective region 5 out of the area of the inclined surface 5 is used.aThe formation range of 52.6%,TransparentRegion 5bThe formation range may be 47.4%. At this time, since the absorption loss per one optical branching element is 5%, the overall light utilization efficiency when the first and second optical branching elements 1 and 2 are arranged in tandem as in the first embodiment is as follows. This is 90.3%, which is a significant improvement over the conventional half mirror made of a metal film.
  The cores 8a, 8b, and 8c are in an interrupted state in the region where the first and second optical branching elements 1 and 2 are formed, but the interrupted distance is within twice the width W of the core. If so, loss due to light diffraction (spreading) is not a problem.
[0035]
  Also, the distance L between the first and second optical branching elements shown in FIG. 2 may be set so as to satisfy the condition shown in the following equation.
L> D × W / (2λ)
  Where W isTransparentThe width of the region 5b, D is the width of the core 8b, and λ is the wavelength of light having the minimum wavelength among the light propagating in the core 8b.
  When the distance L between the first and second optical branching elements 1 and 2 is set so that the condition according to the above equation is satisfied, the first optical branching element 1TransparentThe light that has passed through the region 5b and entered the core 8b has spread only near the center of the core 8b immediately after the incidence, but until the next second optical branching element 2 is reached, the full width of the core 8b is reached by the diffraction effect. It becomes a state spread to.
[0036]
  For example,TransparentWhen the width W of the region 5b is 10 μm, the width D of the core 8b is 20 μm, and the wavelength λ of the light having the minimum wavelength among the light propagating through the core 8b is 0.85 μm, the first and second optical branching elements 1 , 2 need only be larger than about 118 μm.
  Thereby, the original performance of the 2nd optical branching element 2 is exhibited, and the effect that a branching ratio does not fluctuate, for example is acquired.
  As described above, the light incident on the core 8b propagates while being confined in the core 8b, so that the light does not distribute beyond the width D of the core 8b.
[0037]
Example 2
FIG. 4 is a sectional view showing a schematic configuration of an optical waveguide device according to the present invention.
As shown in FIG. 4, the optical waveguide element 20 according to the second embodiment is formed in the resin layer 4 with a space between the substrate 3, the translucent resin layer 4 formed on the substrate 3. The core 8b as an elongated optical waveguide formed in the resin layer 4 so as to propagate light between the first and second optical branching elements 1 and 2, and the first and second optical branching elements 1 and 2. The first and second optical branching elements 1 and 2 have the same configuration as the first and second optical branching elements 1 and 2 according to the first embodiment.
[0038]
Here, the resin layer 4 is composed of the lower clad layer 7, the core layer 8 and the upper clad layer 9 as in the first embodiment, and the core layer 8 is formed with cores 8a, 8b and 8c. Near the end, there is formed a mirror 21 made of an inclined surface 5 formed on a part of the core layer 8 and a reflective film 6 formed on the inclined surface 5.
The upper cladding layer 9 is formed with vertical cores 9a, 9b, and 9c that rise from the mirror 21, the first optical branching element 1 and the second optical branching element 2 to the surface of the upper cladding layer 9, respectively.
[0039]
Above the vertical cores 9 a, 9 b, 9 c, the surface emitting laser 24, the first photodetector 25, and the second are disposed via the electrode 22 formed on the resin layer 4 and the solder 23 applied on the electrode 22. Each of the photodetectors 26 is mounted.
The light emitted from the surface emitting laser 24 enters from the end of the vertical core 9a, propagates through the vertical core 9a, and reaches the mirror 21. The light reaching the mirror 21 is reflected to change its optical path by 90 degrees, enter the core 8a, propagate through the core 8a, and reach the first optical branching element 1. The light that has reached the first optical branching element 1 is branched into two directions, that is, the direction toward the vertical core 9b and the direction toward the core 8b by the branching action of the first optical branching element 1.
[0040]
Of the light branched by the first optical branching element 1, the light branched in the direction toward the vertical core 9b propagates in the vertical core 9b and is radiated from the end of the vertical core 9b, and the first photodetector. The light is received by 25 and converted into an electrical signal.
On the other hand, the light branched in the direction toward the core 8b propagates in the core 8b and reaches the second optical branching element 2, and the direction toward the vertical core 9c and the core 8c are caused by the branching action of the second optical branching element 2. It branches in two directions, the direction to go.
[0041]
Of the light branched by the second optical branching element 2, the light branched in the direction toward the vertical core 9c propagates in the vertical core 9c and is radiated from the end of the vertical core 9c, and the second photodetector. The light is received by 26 and converted into an electrical signal.
On the other hand, the light branched in the direction toward the core 8c further propagates in the core 8c toward another optical branching element or mirror (not shown).
Here, since the branching ratio of the optical branching elements 1 and 2 is not easily affected by the mode of light propagating through the core as described above, the cores 8a, 8b, and 8c are made of large multi-layers having a width and thickness of about 20 μm. It can be formed as a mode waveguide.
As a result, the light from the surface emitting laser 24 having a light emitting portion having a diameter of about 10 μm or more can be efficiently guided to the cores 8a, 8b, and 8c.
[0042]
Further, since the vertical cores 9a, 9b and 9c are formed in the upper clad layer 9, the distance between the end of the vertical core 9a and the surface emitting laser 24 and the end of the vertical cores 9b and 9c The distance between the first and second light detectors 25 and 26 and the light receiving portion is shortened.
Therefore, the light emitted from the surface emitting laser can be incident on the vertical core 9a with a small spread, and the light emitted from the ends of the vertical cores 9b and 9c can be entered with a small spread. The first and second photodetectors 25 and 26 can receive light, and as a result, the light coupling efficiency is improved.
[0043]
Next, the manufacturing method of the optical waveguide element by Example 2 is demonstrated based on FIGS. 5 to 7 and FIGS. 9 to 18 are process diagrams showing the manufacturing process of the optical waveguide device shown in FIG. 4, and FIG. 8 is an explanatory diagram showing the configuration of the gray mask used in the manufacturing process of the optical waveguide device. is there.
[0044]
First, as shown in FIG. 5, the lower cladding layer 7 is formed on the substrate 3. As the substrate 3, a glass substrate having excellent smoothness or a polyimide film having excellent flexibility and heat resistance is used.
The lower cladding layer 7 may have any refractive index lower than that of the core layer 8 to be formed later, but polysilane (manufactured by Nippon Paint Co., Ltd.) from the viewpoint of heat resistance (glass transition point of about 350 ° C. or higher) and spin coating. , Product name: Gracia WG, product number: WG-005). If the heat resistance is about 300 ° C. or higher, the possibility of modification is reduced in the soldering process when mounting electronic components, which is advantageous for mounting.
The lower clad layer 7 is formed by applying the polysilane by spin coating on the substrate 3 and baking it at about 350 ° C. to form a chemically stable film.
[0045]
Next, as shown in FIG. 6, the core layer 8 is formed on the lower cladding layer 7. The core layer 8 is made of polysilane (manufactured by Nippon Paint Co., Ltd., product name: Gracia WG, product number: WG-004) that exhibits hydrophilicity, solubility, and refractive index change when irradiated with ultraviolet light.
Polysilane is rendered hydrophilic by being partially cut off by irradiation with ultraviolet light, and at the same time, it becomes soluble in an alkaline solution, and the refractive index is further lowered. Moreover, it is preferable also from a heat resistant point.
However, in order to ensure a difference in refractive index from the lower cladding layer 7, a material having a composition different from that of the polysilane constituting the lower cladding layer 7 is used.
The core layer 8 is formed by applying the above polysilane onto the lower cladding layer 7 by spin coating and heating to about 250 ° C. to volatilize the solvent in the film.
[0046]
Next, as shown in FIG. 7, the core layer 8 is irradiated with ultraviolet light through the gray mask 30. As shown in FIG. 8, the gray mask 30 includes a transparent substrate 30a and a light shielding film 30b. The light shielding film 30b gradually changes its thickness in order to gradually reduce the light transmittance at a position corresponding to the inclined surface 5. The light transmission part 30c and the opening part 30d adjacent to the light transmission part 30c are provided.
The chemical change (expression of hydrophilicity, solubility, and refractive index change) of polysilane by irradiation with ultraviolet light proceeds in the thickness direction from the surface of the core layer 8 according to the intensity of the irradiated ultraviolet light.
For this reason, in the part irradiated with ultraviolet light through the light transmission part 30c, a chemical change progresses according to the change in the film thickness of the light transmission part 30c, and as a result, the three-dimensional surface of the inclined surface 5 is formed on the core layer 8. An exposure area 31 having a latent image is formed.
[0047]
Next, as shown in FIG. 9, the obtained substrate 3 is immersed in an alkaline solution, and the exposure region 31 (see FIG. 7) where hydrophilicity, solubility, and refractive index change are manifested by irradiation with ultraviolet light is removed. Then, the recess 32 having the inclined surface 5 is formed.
[0048]
Next, as shown in FIG. 10A and FIG. 10B, the obtained substrate 3 is plated with an electroless plating method. At this time, since the hydrophilic group generated by the ultraviolet irradiation in the previous step remains on the inner surface of the recess 32, only the inner surface of the recess 32 is subjected to metal plating, and the reflective film 6 is formed.
In this step, the reflective film 6 is also formed on the inner surface of the concave portion facing the inclined surface 5. However, since this hinders the propagation of light, this portion of the reflective film 6 is removed in the subsequent steps.
[0049]
That is, as shown in FIGS. 11 (a) and 11 (b), a resist 33 is coated on the core layer 4, and openings 34a, 34b, 34c are formed by photolithography, and the reflective film 6 to be removed. To expose.
The opening 34 a is formed so as to expose the reflective film 6 formed on the surface facing the inclined surface 5 while covering the inclined surface 5, and the openings 34 b and 34 c are formed on the surface facing the inclined surface 5. 6 and the central portion of the reflective film 6 formed on the inclined surface 5 are formed in a T shape.
[0050]
Next, as shown in FIGS. 12A and 12B, the obtained substrate 3 is immersed in an etching solution, and an unnecessary reflective film 6 (see FIGS. 11A and 11B). ) Is removed.
Next, as shown in FIGS. 13A and 13B, the resist 33 (see FIGS. 12A and 12C) remaining on the core layer 8 is dissolved and removed with an organic solvent.
[0051]
Next, as shown in FIGS. 14A and 14B, in order to form the cores 8a, 8b and 8c as the optical waveguides in the core layer 8, the patterns corresponding to the cores 8a, 8b and 8c are formed. Ultraviolet light is irradiated through the mask 35 provided with the light shielding film 35b.
That is, since the refractive index of the polysilane constituting the core layer 8 is reduced by irradiating with ultraviolet light, the portion of the core layer 8 that is not the cores 8a, 8b, 8c is irradiated with ultraviolet light to change the refractive index. The core 8a, 8b, 8c is formed by lowering the refractive index of the portions to be the cores 8a, 8b, 8c.
[0052]
Next, as shown in FIG. 15, the core layer 8 is baked at about 350 ° C. to be chemically stabilized.
At this time, the refractive index of the core layer 8 is decreased as a whole, but the refractive index difference caused by the ultraviolet light irradiation in the previous step is maintained as it is, and the refractive index of the entire core layer 8 is in any part. Is maintained higher than the lower cladding layer 7.
Next, as shown in FIG. 16, the upper cladding layer 9 is formed on the core layer 8. The upper clad layer 9 is formed by applying the same polysilane as the polysilane constituting the core layer 8 by spin coating and heating to about 250 ° C. to volatilize the solvent in the film.
[0053]
Next, as shown in FIGS. 17A and 17B, ultraviolet light is applied to the upper clad layer 9 through a mask 36 provided with a light shielding film 36b only in a portion corresponding to the upper portion of the inclined surface 5. The vertical cores 9a, 9b, 9c are formed in the upper clad layer 9 by irradiating and lowering the refractive index of the irradiated portions to relatively increase the refractive index of the portions to be the vertical cores 9a, 9b, 9c.
Next, as shown in FIGS. 18A and 18B, the upper cladding layer 9 is baked at about 350 ° C. to be chemically stabilized.
Thereafter, an electrode 22 for mounting the surface emitting laser 24 and the first and second photodetectors 25 and 26 is formed on the upper cladding layer 9, and the surface emitting laser 24 and the first and second photodetectors 25, The optical waveguide element 20 shown in FIG. 4 is completed by soldering 26 to the electrodes.
[0054]
【The invention's effect】
  This inventionOptical waveguide device according toAccording toOf the first and second optical branching elementsA reflective area having a reflective film for reflecting light by an inclined surface;Transmission without reflection film for transmissionThe light to be transmittedFirst and secondOptical branching elementTransparentThe light can be directly transmitted to the region and light absorption loss can be suppressed as much as possible.
  Further, the optical waveguide has a square cross section and extends in a direction parallel to the substrate, and has a certain width and height. The inclined surfaces of the first and second optical branching elements have widths that coincide with both end faces of the optical waveguide. The first optical branching element has a slit shape with a width W, the width of the optical waveguide is D, and the wavelength of the light propagating in the optical waveguide is optically connected to the optical waveguide. When λ, the distance L between the first and second optical branching elements is set to be longer than the distance L represented by L = D × W / (2λ). The light that has spread to only a part of the optical waveguide immediately after passing through the light reaches the second optical branching element by the diffraction effect until it reaches the second optical branching element. The branching ratio is almost unambiguous with the area ratio of the reflective region to the light receiving region regardless of the light propagation mode. Since determined, stable branching ratio without being affected by the propagation mode change of light is obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a configuration of an optical branching element according to Embodiment 1 of the present invention.
FIG. 2 is a plan view of the optical branching element shown in FIG.
FIG. 3 is a perspective view of a main part of the optical branching element shown in FIG. 1;
FIG. 4 is a cross sectional view schematically showing a configuration of an optical waveguide element according to Embodiment 2 of the present invention.
5 is a process diagram showing a manufacturing process of the optical waveguide element shown in FIG. 4. FIG.
6 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4. FIG.
7 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4; FIG.
8 is an explanatory view schematically showing a configuration of a gray mask used in the manufacturing process of the optical waveguide device shown in FIG. 4; FIG.
9 is a process diagram showing a manufacturing process of the optical waveguide element shown in FIG. 4. FIG.
10 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4, in which (a) and (b) show a cross section and a plane in the same process, respectively.
11 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4, in which (a) and (b) show a cross section and a plane in the same process, respectively.
12 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4, in which (a) and (b) show a cross section and a plane in the same process, respectively.
13 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4, in which (a) and (b) show a cross section and a plane in the process, respectively.
14 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4, in which (a) and (b) show a cross section and a plane in the same process, respectively.
15 is a process diagram showing a manufacturing process of the optical waveguide element shown in FIG. 4. FIG.
16 is a process diagram showing a manufacturing process of the optical waveguide element shown in FIG. 4; FIG.
17 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4, in which (a) and (b) show a cross section and a plane in the same process, respectively.
18 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 4, in which (a) and (b) show a cross section and a plane in the same process, respectively.
FIG. 19 is an explanatory diagram schematically showing a configuration of a conventional optical signal transmission system.
[Explanation of symbols]
1 ... 1st optical branching element
2 ... Second optical branching element
3 ... Board
4 ... Resin layer
5 ... Inclined surface
5a: Reflection area
5b ...Transparentregion
6 ... Reflective film
7 ... Lower cladding layer
8 ... Core layer
8a, 8b, 8c ... core
9: Upper clad layer
9a, 9b, 9c ... vertical core
20: Optical waveguide device
21 ... Mirror
22 ... Electrode
23 ... Solder
24 ... Surface emitting laser
25 ... 1st photodetector
26: Second photodetector
30 ... Gray mask
30a ... Transparent substrate
30b, 35b, 36b ... light shielding film
30c: Light transmission part
30d ... opening
31 ... Exposure area
32 ... recess
33 ... resist
34a, 34b, 34c ... opening
35, 36 ... Mask
D: Core width
L: Distance between the first and second optical branching elements
W ...TransparentArea width

Claims (4)

A substrate, a translucent resin layer formed on the substrate, a first light branching element and a second light branching element formed at intervals in the resin layer, and a first and second light branching element And an elongated optical waveguide formed in the resin layer so as to propagate light therebetween, and the first and second optical branching elements descend at a predetermined angle from the surface of the resin layer toward the surface of the substrate. The inclined surface has a reflection area having a reflection film for reflecting light and a transmission area in which no reflection film is formed for transmitting light, and the optical waveguide has a cross section. Is a rectangular shape, extending in a direction parallel to the substrate, having a certain width and height, and the inclined surfaces of the first and second optical branching elements have a width and a height that match the both end faces of the optical waveguide, respectively. The first optical branching element is optically connected to the optical waveguide, and the transmission region of the first optical branching element is a slit having a width W When the width of the optical waveguide is D and the wavelength of light propagating in the optical waveguide is λ, the distance L between the first and second optical branching elements is expressed as L = D × W / (2λ) An optical waveguide element longer than the distance L. The optical waveguide device according to claim 1, wherein the slit-shaped transmission region is provided so as to cross the center of the inclined surface in a direction perpendicular to the substrate. A process of forming a resin layer by applying a translucent resin that expresses hydrophilicity and solubility by light irradiation to the substrate, and light on the resin layer through a mask having a region where the light transmittance continuously changes. Irradiating a part of the resin layer to develop hydrophilicity and solubility, dissolving and removing a part of the resin layer exhibiting solubility to form an inclined surface, and a surface of the inclined surface having hydrophilicity Of a light branching element comprising: a step of forming a reflective film by electroless plating; and a step of removing a part of the reflective film by etching to form a transmissive region having no reflective film and a reflective region having a reflective film Method. A step of applying a light-transmitting resin that exhibits hydrophilicity, solubility, and refractive index change to the substrate by light irradiation to form a resin layer; and the first light branching element, the second light branching element, and the optical waveguide as a resin And forming the first and second light branching elements by irradiating the resin layer with light through a mask having a region in which the light transmittance changes continuously. Reflecting the surface of the inclined surface with hydrophilicity by electroless plating, the step of developing hydrophilicity and solubility in part, the step of dissolving and removing a part of the resin layer that exhibits solubility, and forming the inclined surface A step of forming a film, and a step of removing a part of the reflective film by etching to form a transmissive region having no reflective film and a reflective region having the reflective film . Light is applied to the resin layer through a mask corresponding to the pattern. Method for manufacturing an optical waveguide element comprising the step of expressing the refractive index change shines resin layer.

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