JP3692973B2 - Organic / inorganic composite waveguide and manufacturing method thereof - Google Patents

Description

【００６１】
ここで、化１中、Ｒ₁ からＲ₁₂は、炭素数１〜１０のハロゲン又はグリシジルオキシ基で置換されていてもよい脂肪族炭化水素基、炭素数６〜１２の芳香族炭化水素基、炭素数１〜８のアルコキシ基からなる群から選択される基であり、同一でも異なっていてもよい。ａ，ｂ，ｃ及びｄは、０を含む整数であり、ａ＋ｂ＋ｃ＋ｄ≧１を満たすものである。
【００６２】
このシリコーン化合物が有する脂肪族炭化水素基の具体例としては、メチル基、プロピル基、ブチル基、ヘキシル基、オクチル基、デシル基、トリフルオロプロピル基、グリシジルオキシプロピル基等の鎖状のもの、及びシクロヘキシル基、メチルシクロヘキシル基のような脂環式のものが挙げられる。
【００６３】
また芳香族炭化水素基の具体例として、フェニル基、ｐ−トリル基、ビスフェニル基が挙げられる。
【００６４】
さらにアルコキシ基の具体例としては、メトキシ基、エトキシ基、フェノキシ基、オクチルオキシ基、ｔｅｒ−ブトキシ基等が挙げられる。
【００６５】
上記Ｒ₁ からＲ₁₂の種類及びａ，ｂ，ｃ，ｄの値は特に重要ではなく、ポリシラン及び有機溶媒と相溶し、膜が透明なものであれば特に限定されい。
【００６６】
相溶性を考慮した場合には、使用するポリシランが有する炭化水素基と同じ基を有していることが好ましい。例えば、ポリシランとして、フェニルメチル系のものを使用する場合には、同じフェニルメチル系又はジフェニル系のシリコーン化合物を使用することが好ましい。
【００６７】
またＲ₁ からＲ₁₂のうち、少なくとも２つが炭素数１〜８のアルコキシ基であるような、１分子中にアルコキシ基を２つ以上有するシリコーン化合物は、架橋剤として利用可能である。そのようなものとしては、アルコキシ基を１５〜３５重量％含んだメチルフェニルメトキシシリコーンやフェニルメトキシシリコーン等を挙げることができる。分子量としては、１０，０００以下、好ましくは３，０００以下のものが好適である。
【００６８】
また上記分岐型ポリシラン化合物の分岐度を２％以上のものを用いることにより、その分岐度が高くなるほど、より光透過率を向上させることができる。それと共に、添加すべきシリコーン化合物の配合比を前述したように最適範囲に選ぶことにより、屈折率の熱安定性を大幅に向上させることができる。
【００６９】
またＣＨ基やＯＨ基による光吸収損失を低減するために、ポリシラン化合物やシリコーン化合物に重水素化、あるいは一部または全てがハロゲン化、特にフッ素化したものを用いれば、上記吸収基による光損失を大幅に低減することができる。これにより、波長依存性の極めて少ない低光伝搬損失のポリマ膜を得ることができる。
【００７０】
さらに、シリコーン化合物に架橋性、あるいはアルコキシ基からなるものを用いることによってポリシラン化合物の中に均一に添加することができ、しかもトルエンのような有機溶媒中に容易に可溶してナノメータレベルの超微粒子状溶液となり、上記ポリマ溶液を用いることにより、光散乱中心のない均一なポリマ膜を形成することができる。
【００７１】
上記図１の塗布工程Ｓ１において、塗布方法としては、スピンコーティング法、押出しコーティング法等を用いる。
【００７２】
次に、塗布工程Ｓ１が終了したならば、基板に塗布した溶液のプリベーク（１００〜１５０℃、２０分）、ポストベーク（３２０〜４８０℃、３０分）する（工程Ｓ２）。
【００７３】
プリベーク温度としては、有機溶媒を蒸発、気化させる程度の温度、すなわち、１００〜１５０℃の範囲から選ぶのが好ましい。プリベーク時間は１０分から４０分程度で十分である。
【００７４】
ついで、ポストベークを行う。ここで、ポリシラン化合物として、例えば、フェニルメチルポリシランを用いると、通常のポストベーク温度は、側鎖のフェニル基やメチル基が脱離しない温度で、無機化しない温度、３００℃以下に選ばれる。
【００７５】
しかし本発明では、超低損失化を達成するためと、超短パルスレーザービーム照射を行うために３２０〜４８０℃の範囲でポストベークを行い、無機化した膜に変える。４８０℃を越えると、膜の表面や内部にクラックが発生しやすいので、クラックの発生しない温度、できることならば３２０〜４５０℃の範囲で行う。
【００７６】
このような温度でポストベークを行うと、後述するように、超低損失な膜を得ることができると共に、緻密化して屈折率も低い値を実現することができる。
【００７７】
上記ポストベークの時間は１０分以上、１時間以内が好ましい。
【００７８】
なお上記プリベークとポストベークはまとめて行い、昇温、保温、降温工程を経るようにして行ってもよい。
【００７９】
次に、図１に示すように、上記ポストベーク工程Ｓ２を終えた膜の内部に、超短パルスレーザビームを集光、照射しつつ、基板の位置をＸ方向、Ｙ方向、あるいはＸ及びＹ方向に所望速度で移動させて、上記膜の内部に高屈折率に変化した光伝搬層のパターンを形成する（工程Ｓ３）。
【００８０】
ここで上記膜の高屈折率変化は、多光子吸収に基づく現象によって生ずるものと考えられており、本発明者の実験によれば、上記レーザービームのパワーが高いほど、基板の移動速度が遅いほど、またパルス幅が狭いほど高屈折率化を実現できることがわかった。
【００８１】
ただし、図１の工程Ｓ２の段階での膜は、通常のガラスと比べれば、よりポーラスで軟化点の低い膜であるので、レーザービームのパワーは高くなくてもよく、またパルス幅も１０００ｆｓから数百ｆｓの範囲で十分に高屈折率化を実現することができた。
【００８２】
なお工程Ｓ３の超短パルスレーザービーム照射による膜の高屈折率化（照射後の屈折率η_a と照射前の屈折率η_b との被屈折率差Δ＝｛（η_a −η_b ）／η_a ｝×１００％）は、工程Ｓ２の膜のポストベーク温度が低いほど、高Δ化が実現できることがわかった。すなわち、ポストベーク温度が高くなると膜はより無機質化して屈折率が低下し、このような膜にレーザービームを照射すると、照射後の屈折率η_a は、それほど大きくならず、逆にポストベーク温度が低いほど（ただし、膜が無機化する温度範囲で低いほど）、η_a は大きくなり、高Δ化を実現できることがわかった。なお、この工程Ｓ２は、レーザービーム照射による熱的効果を利用してもよい。例えば、上記超短パルスレーザービームのパルス幅１０００ｆｓよりも広くし、且つレーザービームのスポット径を光伝搬層形成時の径程度か、それより大きくし、また平均パワーも小さくして行い、その後に、工程Ｓ３を連続的に行ってもよい。すなわち、膜中へ形成する光伝搬層パターンに沿ってレーザービームによる加熱工程、及びレーザービームによる高屈折率化した光伝搬層の形成である。
【００８３】
図２は、本発明の有機質・無機質複合導波路の製造方法の第２の実施の形態を示したものである。
【００８４】
本実施の形態で、図１の実施の形態と違う点は、工程Ｓ１の後、プリベーク（１００〜１５０℃、２０分）のみを行う工程Ｓ２Ａを行い、次いで、プリベーク膜内部への超短パルスレーザビーム照射による高屈折率の光伝搬層パターンを形成する工程Ｓ３を行った後に、ポリシラン膜のポストベーク（３２０〜４８０℃、３０分）の工程Ｓ２Ｂを行う方法である。
【００８５】
この方法の特徴は、プリベーク膜中への超短パルスレーザービームを集光、照射するので、より高Δ化を図ることができる点にある。
【００８６】
図３は、本発明の有機質・無機質複合導波路の製造方法の第３の実施の形態を示したものである。
【００８７】
本実施の形態では、ポリシラン化合物の溶液塗布の工程Ｓ１の後、先ずポリシラン化合物の溶液のプリベーク（１５０℃、２０分）を行った後に、第１のポストベーク（２００〜２５０℃の範囲で３０分程度）の工程Ｓ２Ｃを行う。次いで、工程Ｓ２Ｃの後のポストベークを行った膜上に、所望の光伝搬層パターンの描かれたフォトマスクを介して紫外線照射し、上記ポストベーキングを行った膜に上記パターンの屈折率変化パターンを形成するポリシラン膜のパターニングの工程Ｓ３Ｃを行う。すなわち、上記フォトマスクの紫外線透過部を通った紫外線照射により、屈折率は低下する。その屈折率の低下の度合いは紫外線の照射エネルギー（照射パワー、照射時間）による。例えば、上記ポリシラン膜を用いれば０．数％から６％程度の比屈折率差を得ることができる。上記フォトマスクの紫外線非透過部、すなわち、光伝搬層パターン部は、屈折率は変化せず、そのままである。
【００８８】
次に上記膜に対して第２のポストベーク（３２０〜４８０℃、３０分程度）の工程Ｓ２Ｄを行う。
【００８９】
そして最後に上記紫外線が照射されなかったパターン部の膜内部に超短パルスレーザービームを集光、照射し、高屈折率に変化した光伝搬層パターンを形成する工程Ｓ３Ｄを行う。
【００９０】
この方法によれば、ポリシラン膜のパターニングの工程Ｓ３Ｃの段階で、高Δが得られた段階で、さらにレーザービーム照射で、さらなる高Δ化を実現することができる。また工程Ｓ３Ｃの段階で、光伝搬層となり得るパターンが形成され、光伝搬層パターンを形成する工程Ｓ３Ｄで、上記パターンに沿ってレーザービームを照射するので、高寸法精度の光伝搬層パターンを形成することができる。
【００９１】
なお、このレーザービーム照射による光伝搬層の形成は、上記紫外線照射領域の全域か一部の領域でもよい。
【００９２】
図４は、本発明の有機質・無機質複合導波路の製造方法の第４の実施の形態を示したものである。
【００９３】
本実施の形態は、基本的には図３の第３の実施の形態と工程Ｓ１，Ｓ２Ｃ，Ｓ３Ｃまでは同じである。
【００９４】
第３の実施の形態と違う点は、工程Ｓ２Ｄと工程Ｓ３Ｄとを入れ換えた点にある。
【００９５】
すなわち、フォトマスクを介した紫外線によるポリシラン膜のパターニングの工程Ｓ３Ｄの後に、第２のポストベーキング工程Ｓ２Ｄを行う。
【００９６】
このようにすると、図３の方法よりもさらに高Δ化を実現することができる。
【００９７】
その理由は、図３の第３の実施の形態では、ポリシラン膜のパターニングの工程Ｓ３Ｃの段階で、高Δパターンが得られた後に第２のポストベーキング工程Ｓ２Ｄを行うと、上記高Δが少し低下するが、図４の第４の実施の形態では、高Δパターンを得た後に、超短パルスレーザビームを照射して光伝搬層パターンを形成する工程Ｓ３Ｄを行うことで、高Δ化を図れるためである。そして最後に、第２のポストベーキング工程Ｓ２Ｄを行うことにより、紫外線の照射された領域の屈折率が下がるので、結果的にさらに高Δ化を実現することができる。
【００９８】
図５は、本発明の有機質・無機質複合導波路の製造方法の第５の実施の形態を示したものである。
【００９９】
図５において、工程Ｓ１，Ｓ２Ｃ，Ｓ３Ｃまでは、第３及び第４の実施の形態と同じである。
【０１００】
紫外線照射によって光の伝搬する高屈折率のパターン部とその両側面の低屈折率部の上にクラッド用ポリマ溶液を塗布する工程Ｓ４を設ける。その後、上記クラッド用ポリマ溶液のプリベーク（１００〜１５０℃の範囲で２０分程度）、次いでポストベーク（２００〜２５０℃の範囲で３０分）の工程Ｓ５を行う。最後に上記紫外線が照射されなかった高屈折率のパターン部の内部へ超短パルスレーザービームを集光して照射し、高屈折率に変化した光伝搬層を形成する工程Ｓ３Ｄを行う。
【０１０１】
この方法の特徴は、光伝搬層が上部クラッド層で十分に覆われていることである。これにより、さらに低損失の導波路を得ることができる。
【０１０２】
次に、超低損失導波路を実現する上で重要なポストベーク温度とポリマ膜の伝搬損失との関係について図６により説明する。
【０１０３】
図６は本発明に用いるポリマ膜の伝搬損失とベーク温度との関係を実験したものである。
【０１０４】
これは、バイコールガラス基板（厚み０．５ｍｍ）上に形成したポリマ膜（膜厚：約９μｍ）の伝搬損失を波長１３００ｎｍと１５５０ｎｍで測定した結果を示したものである。
【０１０５】
横軸のベーク温度は、バイコールガラス基板（コーニンググラス社製、厚み０．５ｍｍ）上に塗布したポリマ溶液をプリベーク（１５０℃，２０分）した後に行うポストベーク（温度ｔ℃、３０分間）の温度ｔであり、上記温度ｔを種々変えて作成したポリマ膜の伝搬損失を縦軸に示している。
【０１０６】
上記ポリマ溶液は、トルエン有機溶媒に、分岐度が２０％のポリメチルフェニルシランと、メチルフェニルメトキシリコーンを５０％添加したポリマ溶液である。
【０１０７】
図６からわかるように、ポストベーク温度が高くなるほど、ポリマ膜の伝搬損失を低くすることができる。この結果は本発明者が見いだしたものである。さらに温度を上げれば、低損失化が可能であるが、基板との熱膨張係数の違いにより、ポリマ膜中に歪みが生じてクラックが入り、逆に伝搬損失が増大する。この熱的効果によるダメージを防ぐために超短パルスレーザービーム照射による高屈折率変化による三次元導波路の作成と、熱的ダメージをなくして低損失化を達成するようにしたものである。
【０１０８】
上記ポストベークを行った膜中への超短パルスレーザービームの集光、照射により、Δが１％以上の高Δ光伝搬層を実現し、また波長１３００ｎｍ、１５５０ｎｍにおける伝搬損失として、図６の結果よりもさらに低く、０．０１ｄＢ／ｃｍ以下の超低損失導波路を実現することができることがわかった。
【０１０９】
なお、上記超短パルスレーザービームとして、波長８００ｎｍ、パルス幅２００〜１０００ｆｓ、パルス繰り返し数十Ｈｚ〜数百ＫＨｚのものを用いた。また作成した三次元導波路は上記測定波長においてシングルモード導波路であった。
【０１１０】
図７は本発明に用いるポリマ膜の屈折率、膜厚のベーキング温度依存性の実験例を示したものである。このポリマ膜は図６で説明したものと同じである。
【０１１１】
図７に示すように、ポストベーク温度が高くなるほど、ポリマ膜の屈折率及び膜厚は低下する。なお屈折率は波長１３００ｎｍで測定した結果である。
【０１１２】
図７のポリマ膜に超短パルスレーザービームを照射すると、照射された部分の膜の屈折率は０．数％〜１％程度高くなることがわかった。これは多光子吸収現象によるものと考えられる。この屈折率が高くなる現象は、図７のベーク温度を高くすることによって屈折率が低下する現象と相反するものである。
【０１１３】
次に本発明の三次元導波路の具体例を図８〜図１３に示す。
【０１１４】
先ず図８は、図１で説明した工程（あるいは図２で説明した工程）で作ることができる第１の三次元導波路の断面図を示したものである。
【０１１５】
基板１０には、ガラス、プラスチック、セラミック、半導体、強誘電体、あるいはこれらを組み合わせた材料からなる基板を用いることができる。
【０１１６】
特に、ポリマ溶液を基板上に塗布し、低温でのプリベーク、ポストベークでポリマ膜１２とした後に、超短パルスレーザビーム照射で高屈折率に変化させた光伝搬層１３を形成するので、基板１０には、プラスチックフィルム、プリント基板等のような低温処理に適した基板を用いることができ、かつ大気中でのポリマ溶液の塗布（スピンコーティング，押し出しコーティング等）で成膜化を行えるので、大面積の基板へ適用できるという特徴がある。
【０１１７】
次に、図９について説明する。
【０１１８】
図９（ａ）は第２の三次元導波路の断面図、図９（ｂ）は、図９（ａ）のＡ−Ａ線断面内における屈折率分布、図９（ｃ）は、図９（ａ）のＢ−Ｂ線断面内における屈折率分布を示したものである。
【０１１９】
この図９は、図３の第３の実施の形態の工程あるいは図４の第４の実施の形態の工程を用いて作ることができる三次元導波路の断面図を示したもので、基板２０上に、前述したポリシラン化合物のフォトブリーチング用ポリマ膜２１、２２Ａ，２２Ｂが形成されており、左右のポリマ膜２２Ａ，２２Ｂは、フォトマスクを介した紫外線照射によって屈折率が低下した領域であり、中央のポリマ膜２１は、紫外線が照射されなかった領域であり、この領域内に超短パルスレーザービーム照射によって高屈折率に変化させられた光伝搬層２３が形成されている。
【０１２０】
したがって、光伝搬層２３の屈折率は、最も高い値η_a となり、またその層内で、レーザービームのスポット径内パワー分布に相似したような僅かな屈折率分布をもっている。
【０１２１】
左右のポリシラン膜２２Ａ，２２Ｂの領域は、紫外線照射によって、低屈折率η_p （η_p ＜η_a ）になっている。紫外線が照射されなかった中央のポリマ膜２１の領域は、屈折率η_b （η_p ＜η_b ＜η_a ）になっている。
【０１２２】
図１０は、第３の三次元導波路の断面を示したものである。
【０１２３】
図１０は、図９で説明した、ポリマ膜２１，２２Ａ，２２Ｂの上に上部クラッド層２４（屈折率は、ポリマ膜２２Ａ，２２Ｂのそれと略等しいかそれよりも低い値）を設けた構造であり、図５の第５の実施の形態の工程によって作られたものである。
【０１２４】
図１１は、第４の三次元導波路の断面を示し、この第４の三次元導波路は、図１０の三次元導波路において、基板２０とポリマ膜２１，２２Ａ，２２Ｂの間に低屈折率（屈折率は、ポリマ膜２１，２２Ａ、上部クラッド層２４のそれと等しいかそれよりも低い値）の層２５を設けた構造の断面図を示したものである。
【０１２５】
上記低屈折率の層２５及び上部クラッド層２４をフォトブリーチング用ポリマ材料、あるいはポリマ材料で形成すると全ての層を塗布工程で形成することができること、及び低温で形成することができるといった利点が得られる。
【０１２６】
図１２は、第５の三次元導波路の断面を示したものである。
【０１２７】
これは基板２０上に低屈折率の層２５を形成し、その低屈折率の層２５上に、紫外線を照射したポリマ膜２２Ａ，２２Ｂ，２２Ｃ，２２Ｄと、紫外線が照射されていないパターン部のポリマ膜２１Ａ，２１Ｂ，２１Ｃを交互に形成し、その紫外線が照射されていないポリマ膜２１Ａ，２１Ｂ，２１Ｃ内に、高屈折率変化した光伝搬層２３Ａ，２３Ｂ，２３Ｃを形成し、さらにポリマ膜２１Ａ，２１Ｂ，２１Ｃ，２２Ａ，２２Ｂ，２２Ｃ，２２Ｄ上に上部クラッド層２４を形成すると共にそのクラッド層２４上に紫外線をカットするための紫外線カット層２６を形成した例である。
【０１２８】
図１３は、第６の三次元導波路の断面を示したものである。
【０１２９】
これは、高屈折率化した光伝搬層を積層構造にしたものである。
【０１３０】
すなわち、基板２０上に低屈折率の層２５を形成し、その低屈折率の層２５上ポリマ層２２Ｆを形成し、そのポリマ層２２Ｆ内に光伝搬層２３Ａ，２３Ｂ，２３Ｃを形成し、上記ポリマ層２２Ｆの上に低屈折率（屈折率はポリマ層２２Ｆのそれよりも低い値）の中間層２７を介してポリマ層２２Ｇを設け、このポリマ層２２Ｇ内に光伝搬層２３Ｄ，２３Ｅを形成し、さらにそのポリマ層２２Ｇ上に上部クラッド層２４を形成した積層構造導波路である。
【０１３１】
本発明は上記実施の形態に限定されない。例えば高屈折率化された光伝搬層はポリマ膜の内部以外に、ポリマ膜表面に設けてもよい。そしてその表面に低屈折率のポリマ層を形成してもよい。
【０１３２】
高屈折率化された光伝搬層のパターンは、直線パターン、曲線パターン、およびこれらを組み合わせたパターンで構成され、光方向性結合回路、光スターカプラ、光リング共振回路、光フィルタ、アレイ格子型グレーティング、Ｙ分岐光回路あるいはこれらを組合せた光回路などを構成するようにしてもよい。
【０１３３】
ポリマ膜は、ポリシラン化合物、ポリシラン化合物にシリコーン化合物を添加したもの、あるいはポリシラン化合物にシリコーン化合物と光酸発生剤（トリジアン系、過酸化物等）を添加したものを用いてもよい。高屈折率化された光伝搬層は、図１３の構造以外に、更に多層状に積層されたポリマ層の中に設けられていてもよい。またその際は、中間層２７は必ずしも設けなくてもよい。
【０１３４】
図１４に示したように、基板３０上に低屈折率の層３５を形成し、その低屈折率の層３５上に、第１の光伝搬層パターンが描かれているフォトマスクを介して紫外線照射して高屈折率の第１の光伝搬層３２とその側面に低屈折率化された側面クラッド層３１Ａ，３１Ｂを形成した後に、上記第１の光伝搬層３２に超短パルスレーザビームを集光、照射してさらに高屈折率の光伝搬層３３に変え、さらに上部クラッド層３４を形成するようにすれば、パターン寸法精度のよい光伝搬層をより高Δで実現することができる。
【０１３５】
【発明の効果】
以上要するに本発明によれば、次のような効果を奏する。
（１）ガラス導波路の損失と同程度かそれよりもさらに低損失を実現することができ、しかも従来のガラス導波路の製造方法に比して圧倒的に簡単で安価な製造方法で作ることができる。すなわち、大気中において、塗布工程と５００℃以下の加熱工程、超短パルスレーザービーム照射工程、場合によっては紫外線照射工程の併用で作製することができる。またプラスチックフィルム、プリント基板等の超大型の基板上に形成することができるので高集積化した高機能光回路を構成することができる。さらに低温工程で作れるので、基板の反りを起こすことなく、光学特性の劣化も少ない。
（２）ＣＨ基による吸収損失も３２０〜４８０℃の温度で無機化することにより、また超短パルスレーザービームを照射することにより、ほとんどなくすことができ、広い波長域にわたって超低損失な三次元型光回路を実現することができる。
（３）温度変化による屈折率の安定性も３２０〜４８０℃のポストベーク温度でベーキングしてポリシラン膜（あるいはシリコーンや光酸発生剤を添加したポリシラン膜）を無機化することにより、良好にすることができ、さらに超短パルスレーザービーム照射でさらなる無機化を図り、温度変化に対して屈折率変化が少ない光伝搬層を実現することができる。
（４）三次元導波路をポリマ溶液の塗布からスタートし、それのポリマ膜化および無機化、レーザービーム照射による光伝搬層の形成化等を行い、低コストで超低損失な光回路を実現することができる。
（５）フォトブリーチングポリマ層上に第１の光伝搬層パターンの描かれているフォトマスクを介して紫外線を照射して高屈折率の第１の光伝搬層パターンを形成した後に、その第１の光伝搬層パターンに沿って超短パルスレーザービームを照射することによって、その第１の光伝搬層をさらに高屈折率化すると共に、パターン寸法精度のよい第２の光伝搬層を第１の光伝搬層内に形成することができるので、散乱損失の低い超低損失・超小型・高Δ導波路およびそれを用いた光回路を実現することができる。
（６）基板として、プリント基板やプラスチックフィルム等の耐熱温度の低い基板を用いることができるので、ＬＳＩやＬ，Ｃ，Ｒ等の電気部品の搭載された基板上に光配線回路、光信号処理を超低損失で実現することが可能となる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態を示す図である。
【図２】本発明の第２の実施の形態を示す図である。
【図３】本発明の第３の実施の形態を示す図である。
【図４】本発明の第４の実施の形態を示す図である。
【図５】本発明の第５の実施の形態を示す図である。
【図６】本発明において、ポリマ膜の伝搬損失とベーキング温度の関係を示す図である。
【図７】本発明において、ポリマ膜の屈折率、膜厚のベーク温度依存性を示す図である。
【図８】本発明の方法で作製された第１の三次元導波路の断面図である。
【図９】本発明の方法で作製された第２の三次元導波路の断面とその屈折率を示す図である。
【図１０】本発明の方法で作製された第３の三次元導波路の断面図である。
【図１１】本発明の方法で作製された第４の三次元導波路の断面図である。
【図１２】本発明の方法で作製された第５の三次元導波路の断面図である。
【図１３】本発明の方法で作製された第６の三次元導波路の断面図である。
【図１４】本発明の方法で作製された第７の三次元導波路の断面図である。
【符号の説明】
１０，２０，３０ 基板
１２ ２２ ポリマ膜
２１ ポリマ膜
２３ 光伝搬層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic / inorganic composite waveguide that can be produced in the atmosphere by a simple method and that can realize extremely low loss characteristics, and a method for manufacturing the same.
[0002]
[Prior art]
Research and development of polymer waveguides using polymer materials has become active. Since this polymer waveguide can be easily produced by a low temperature process, it has been considered that superiority can be expected in terms of cost reduction and large size as compared with a glass waveguide using a glass material. ing. That is, a polymer solution dissolved in an organic solvent is applied onto various substrates by a spin coating method, an extrusion coating method, or the like, and then heated at a low temperature (≦ 300 ° C.) to form a polymer film. Next, after obtaining a substantially rectangular high refractive index core polymer pattern using photolithography or an etching process, a low refractive index polymer film is formed so as to cover the core pattern.
[0003]
As a method for producing a polymer waveguide in a simple manner in the atmosphere, the present inventor first forms a polymer film for photobleaching on a substrate on which a film having a lower refractive index is formed, and then a desired method. The photomask on which the core pattern is drawn is irradiated with ultraviolet light on the photobleaching polymer film, and the refractive index of the photobleaching polymer film irradiated with the ultraviolet light is lowered to form a side cladding layer. The region not irradiated with ultraviolet light becomes a core layer without a decrease in refractive index. Thereafter, a polymer waveguide is realized by forming a low refractive index clad polymer film so as to cover the photobleaching polymer film.
[0004]
[Problems to be solved by the invention]
However, the above-described conventional polymer waveguide has the following problems.
[0005]
(1) Transmission loss is too high compared to glass waveguide, making it difficult to put it into practical use.
[0006]
(2) It is difficult to reduce the loss due to the absorbing group (CH group) unique to the polymer material.
If it is fluorinated in order to reduce this, the heat resistance and handleability of the material itself deteriorate, and it becomes very expensive.
[0007]
(3) Although polymer waveguides using photobleaching polymer materials are characterized by simple methods in the atmosphere, it is difficult to reduce the loss due to intrinsic absorption.
[0008]
(4) Compared with glass materials, polymer materials have poor refractive index stability due to temperature changes, and optical characteristics are likely to change even when an optical circuit is configured.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide an organic / inorganic composite waveguide that can be easily manufactured and a method for manufacturing the same.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a pulse width of 1000 fs (femto sec; 10 on the surface or inside of a polymer film made of a polysilane compound. ^-15 The organic-inorganic composite waveguide is characterized in that a light propagation layer pattern obtained by condensing an ultrashort pulse laser beam of less than 2 seconds) and changing it to a high refractive index is formed on the polymer film surface or inside.
[0011]
A silicone compound may be added to the polysilane compound at a desired mixing ratio, and a compound bonded to a hydrocarbon group, an alkoxy group, or a hydrogen atom in addition to the Si atom may be used.
[0012]
In addition, as the polysilane compound, a part or all of which is deuterated may be used.
[0013]
Further, the polysilane compound may be a part or all of which is fluorinated.
[0014]
The silicone compound may be crosslinkable or an alkoxy group.
[0015]
In addition, part or all of the silicone compound may be deuterated.
[0016]
Further, part or all of the silicone compound may be fluorinated.
[0017]
The polymer film has a pattern in a region where the refractive index is lowered by irradiation with ultraviolet light through a photomask having a desired pattern shape and a region in which the refractive index is not lowered without being irradiated with ultraviolet light. The ultrashort pulse laser beam is focused and irradiated on a high refractive index region that has not been irradiated with ultraviolet rays, so that a light propagation layer having a refractive index higher than the refractive index of the polymer film is formed. It may be.
[0018]
A clad polymer film having a refractive index lower than that of the polymer film may be formed on the surface of the polymer film.
[0019]
Moreover, the polymer film may be heat-treated in the range of 320 to 480 ° C.
[0020]
The heat treatment of the polymer film may be performed either before or after irradiation with the ultrashort pulse laser beam.
[0021]
The polymer film may be formed on the substrate.
[0022]
Further, a plurality of polymer films may be laminated.
[0023]
The present invention includes a step of applying a solution of a polysilane compound dissolved in an organic solvent on a substrate in addition to the organic / inorganic composite waveguide, and then a polymer film cured by heat treatment in a temperature range of 100 to 480 ° C. A step of obtaining a high refractive index by relatively changing the position of the condensing point and the substrate while condensing an ultrashort pulse laser beam having a pulse width of 1000 fs or less on the surface or inside of the polymer film. This is a method for producing an organic / inorganic composite waveguide having a step of forming the pattern of the light propagation layer on the surface or inside of the polymer film.
[0024]
A silicone compound may be added to the solution of the polysilane compound dissolved in the organic solvent at a desired compounding ratio.
[0025]
The heat treatment step may be narrowed to a pre-baking temperature range of 100 to 250 ° C., and instead, a step of post-baking in a temperature range of 320 to 480 ° C. may be provided after the step of forming the pattern of the light propagation layer.
[0026]
In addition to the above pre-baking process, a photomask with a desired pattern shape is placed on the polymer film and irradiated with ultraviolet light, and the region where the refractive index is reduced by the ultraviolet light irradiation and the ultraviolet light is not irradiated. A step of forming a pattern in which the refractive index did not decrease, and after the step, the ultra-short pulse laser beam is focused on and irradiated to the region not irradiated with the ultraviolet light, It is also possible to provide a step of forming a pattern of the light propagation layer that has been changed to a high refractive index by relatively changing the position, and a post-baking step.
[0027]
You may provide the said post-baking process before the process of forming the pattern of the light propagation layer by ultrashort pulse laser beam irradiation.
[0028]
A step of forming a cladding polymer having a refractive index lower than the refractive index of the polymer film on the surface of the polymer film on which the light propagation layer is formed may be provided.
[0029]
The clad polymer film forming step may be provided after the step of forming a refractive index pattern of the polymer film by ultraviolet light irradiation.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0031]
1 to 5 show an embodiment of a method for producing an organic / inorganic composite waveguide according to the present invention.
[0032]
First, the manufacturing method of FIG. 1 will be described.
[0033]
As shown in FIG. 1, a solution of a polysilane compound dissolved in an organic solvent is applied onto a substrate (step S1).
[0034]
Here, as a substrate, in addition to glass, ceramics, plastics, semiconductor, ferroelectric crystal, a substrate made of a combination of the above materials (for example, glass-filled plastics, Si substrate with oxide film, etc.) is used. Can do.
[0035]
As the polysilane compound, linear and branched polysilane compounds can be used.
[0036]
Here, the branched type and the straight type are distinguished by the bonding state of Si atoms contained in the polysilane.
[0037]
The branched type is a polysilane compound containing Si atoms having 3 or 4 bonds to adjacent Si atoms (number of bonds).
[0038]
On the other hand, in the linear type, the number of bonds between Si atoms adjacent to Si atoms is two. Usually, since the valence of Si atoms is 4, those having 3 or less bonds among Si atoms present in polysilane are bonded to hydrocarbons, alkoxy groups or hydrogen atoms in addition to Si atoms. . As such a hydrocarbon group, an aliphatic hydrocarbon group which may be substituted with a halogen having 1 to 10 carbon atoms and an aromatic hydrocarbon group having 6 to 14 carbon atoms are preferable.
[0039]
Specific examples of the aliphatic hydrocarbon group include a chain group such as a methyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a trifluoropropyl group, and a nonafluorohexyl group, a cyclohexyl group, and a methylcyclohexyl group. Examples include alicyclic groups such as groups.
[0040]
Specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, a biphenyl group, and an anthracyl group.
[0041]
Examples of the alkoxy group include those having 1 to 8 carbon atoms. Specific examples include a methoxy group, an ethoxy group, a phenoxy group, and an octyloxy group. Among these, a methyl group and a phenyl group are particularly preferable in view of ease of synthesis.
[0042]
In the case of the branched type, the adjacent Si atoms are preferably 2% or more of the total number of Si atoms in the branched polysilane. Less than 2% or linear polysilane has high crystallinity, and microcrystals are easily generated in the film, which causes scattering and lowers transparency. However, in the case of the present invention, as described later, the polysilane film is mineralized by heat treatment at a high temperature of 350 to 450 ° C., and the film surface or the inside is irradiated with an ultrashort pulse laser beam. Less than 2% or linear polysilane can also be applied.
[0043]
The upper limit of the degree of branching is limited in making a soluble polymer solution by dissolving in an organic solvent, and the upper limit is about 50%.
[0044]
The polysilane used in the present invention is produced by a polycondensation reaction by heating a halogenated silane compound to 80 ° C. or higher in an organic solvent such as n-decane or toluene in the presence of an alkali metal such as sodium. Can do.
[0045]
It can also be synthesized by an electrolytic polymerization method or a method using metal magnesium and a metal oxide.
[0046]
In the case of the branched polysilane compound, the halosilane is composed of an organotrihalosilane compound, a tetrahalosilane compound, and a diorganodihalosilane compound, and the organotrihalosilane compound and the tetrahalosilane compound are 2 mol% or more of the total amount. The target branched polysilane compound is obtained by polycondensation by heating the mixture.
[0047]
Here, the organotrihalosilane compound is a Si atom source having a bond number of 3 with an adjacent Si atom, and one tetrahalosilane compound is an Si atom source having a bond number of 4 with an adjacent Si atom. Become.
[0048]
The network structure can be confirmed by measuring an ultraviolet absorption spectrum or a silicon nuclear magnetic resonance spectrum.
[0049]
It is preferable that the halogen atom which each of the organotrihalosilane compound, the tetrahalosilane compound, and the diorganodihalosilane compound used as the raw material for polysilane has is a chlorine atom.
[0050]
Examples of the substituent other than the halogen atom that the organotrihalosilane compound and the diorganodihalosilane compound have include the above-described hydrocarbon group, alkoxy group, or hydrogen atom.
[0051]
The polysilane compound is not particularly limited as long as it is soluble in an organic solvent and can form a transparent film by coating.
[0052]
Preferable examples of such organic solvents are C5-12 hydrocarbons, halogen hydrocarbons, and ethers.
[0053]
Examples of hydrocarbons include pentane, hexane, heptane, cyclohexane, n-decane, n-dodecane, benzene, toluene, xylene, methoxybenzene, and the like.
[0054]
Examples of the halogen hydrocarbon include carbon tetrachloride, chloroform, 1,2-dichloroethane, dichloromethane, chlorobenzene and the like.
[0055]
Examples of ethers include diethyl ether, dibutyl ether, tetrahydrofuran and the like.
[0056]
A silicone compound may be added in a desired mixing ratio in the solution of the polysilane compound dissolved in the organic solvent. That is, the blending ratio of silicone to polysilane compound is preferably in the range of 20 to 130 wt%.
[0057]
When the amount of silicone compound added is small, the refractive index of the polymer film is high, and the amount of change in the refractive index with respect to the baking temperature is large. The greater the amount of silicone compound added, the lower the refractive index of the polymer film. However, in the range of 40 to 90 wt%, the refractive index change with respect to the baking temperature is small. The change of the refractive index with respect to the baking temperature becomes large.
[0058]
The light transmittance of the polymer film becomes better as the amount of the silicone compound added increases.
[0059]
Here, the silicone compound shown in Chemical Formula 1 is used.
[0060]
[Chemical 1]

[0061]
Here, in Chemical Formula 1, R ₁ To R ₁₂ Is an aliphatic hydrocarbon group optionally substituted with a halogen having 1 to 10 carbon atoms or a glycidyloxy group, an aromatic hydrocarbon group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. The groups selected may be the same or different. a, b, c, and d are integers including 0 and satisfy a + b + c + d ≧ 1.
[0062]
Specific examples of the aliphatic hydrocarbon group possessed by the silicone compound include chain groups such as methyl group, propyl group, butyl group, hexyl group, octyl group, decyl group, trifluoropropyl group, glycidyloxypropyl group, And an alicyclic group such as a cyclohexyl group and a methylcyclohexyl group.
[0063]
Specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, and a bisphenyl group.
[0064]
Furthermore, specific examples of the alkoxy group include methoxy group, ethoxy group, phenoxy group, octyloxy group, ter-butoxy group and the like.
[0065]
R above ₁ To R ₁₂ And the values of a, b, c and d are not particularly important as long as they are compatible with polysilane and an organic solvent and the film is transparent.
[0066]
In consideration of compatibility, it is preferable that the polysilane used has the same group as the hydrocarbon group. For example, when a phenylmethyl type polysilane is used, it is preferable to use the same phenylmethyl type or diphenyl type silicone compound.
[0067]
Also R ₁ To R ₁₂ Among them, a silicone compound having two or more alkoxy groups in one molecule such that at least two are alkoxy groups having 1 to 8 carbon atoms can be used as a crosslinking agent. Examples thereof include methylphenylmethoxysilicone and phenylmethoxysilicone containing 15 to 35% by weight of alkoxy groups. The molecular weight is 10,000 or less, preferably 3,000 or less.
[0068]
Further, by using the branched polysilane compound having a branching degree of 2% or more, the light transmittance can be further improved as the branching degree becomes higher. At the same time, the thermal stability of the refractive index can be greatly improved by selecting the compounding ratio of the silicone compound to be added within the optimum range as described above.
[0069]
In order to reduce light absorption loss due to CH group or OH group, if polysilane compound or silicone compound is deuterated or partially or completely halogenated, especially fluorinated, light loss due to the above absorbing group Can be greatly reduced. Thereby, it is possible to obtain a polymer film having a low light propagation loss and extremely low wavelength dependency.
[0070]
Furthermore, by using a silicone compound having a crosslinkable or alkoxy group, it can be uniformly added to the polysilane compound, and it can be easily dissolved in an organic solvent such as toluene and can be nanometer level. By forming a fine particle solution and using the polymer solution, a uniform polymer film having no light scattering center can be formed.
[0071]
In the coating step S1 in FIG. 1, a spin coating method, an extrusion coating method, or the like is used as a coating method.
[0072]
Next, when the coating step S1 is completed, the solution applied to the substrate is pre-baked (100 to 150 ° C., 20 minutes) and post-baked (320 to 480 ° C., 30 minutes) (step S2).
[0073]
The pre-baking temperature is preferably selected from a temperature at which the organic solvent is evaporated and vaporized, that is, a range of 100 to 150 ° C. A pre-bake time of about 10 to 40 minutes is sufficient.
[0074]
Next, post bake is performed. Here, when, for example, phenylmethylpolysilane is used as the polysilane compound, the normal post-bake temperature is selected at a temperature at which the phenyl group and methyl group in the side chain are not eliminated and at a temperature at which the inorganic group is not mineralized, 300 ° C. or less.
[0075]
However, in the present invention, in order to achieve ultra-low loss and to perform ultrashort pulse laser beam irradiation, post-baking is performed in the range of 320 to 480 ° C. to change to an inorganic film. If the temperature exceeds 480 ° C., cracks are likely to occur on the surface and inside of the film, and therefore, the crack is not generated, preferably in the range of 320 to 450 ° C.
[0076]
When post-baking is performed at such a temperature, an ultra-low-loss film can be obtained as described later, and a fine refractive index and a low refractive index can be realized.
[0077]
The post-baking time is preferably 10 minutes or more and 1 hour or less.
[0078]
The pre-bake and post-bake may be performed together, and may be performed through a temperature raising process, a temperature holding process, and a temperature lowering process.
[0079]
Next, as shown in FIG. 1, the position of the substrate is set in the X direction, Y direction, or X and Y while condensing and irradiating an ultrashort pulse laser beam inside the film after the post-baking step S2. The pattern of the light propagation layer changed to a high refractive index is formed inside the film by moving it in the direction at a desired speed (step S3).
[0080]
Here, it is considered that the high refractive index change of the film is caused by a phenomenon based on multiphoton absorption. According to the experiment of the present inventors, the higher the power of the laser beam, the slower the moving speed of the substrate. Further, it was found that a higher refractive index can be realized as the pulse width is narrower.
[0081]
However, since the film at the step S2 in FIG. 1 is a film that is more porous and has a lower softening point than ordinary glass, the power of the laser beam does not have to be high, and the pulse width is from 1000 fs. A sufficiently high refractive index could be realized in the range of several hundred fs.
[0082]
Note that the refractive index of the film is increased by irradiation with the ultrashort pulse laser beam in step S3 (refractive index η after irradiation). _a And refractive index η before irradiation _b Difference in refractive index Δ = {(η _a −η _b ) / Η _a } × 100%), it was found that a higher Δ can be realized as the post-baking temperature of the film in step S2 is lower. That is, when the post-bake temperature is increased, the film becomes more inorganic and the refractive index decreases, and when such a film is irradiated with a laser beam, the refractive index η after irradiation _a Is not so large, and conversely, the lower the post-bake temperature (however, the lower the temperature range at which the film becomes mineral), _a It became clear that a high Δ could be realized. In addition, this process S2 may utilize the thermal effect by laser beam irradiation. For example, the pulse width of the ultrashort pulse laser beam is made wider than 1000 fs, the spot diameter of the laser beam is made about the same as or larger than the diameter at the time of forming the light propagation layer, and the average power is made small. Step S3 may be performed continuously. That is, a heating process using a laser beam along a light propagation layer pattern formed in the film, and formation of a light propagation layer having a high refractive index using a laser beam.
[0083]
FIG. 2 shows a second embodiment of the method for producing an organic / inorganic composite waveguide of the present invention.
[0084]
In the present embodiment, the difference from the embodiment of FIG. 1 is that after step S1, only step S2A is performed in which only pre-baking (100 to 150 ° C., 20 minutes) is performed, and then an ultrashort pulse into the pre-baked film is formed. This is a method of performing step S2B of post-baking (320 to 480 ° C., 30 minutes) of the polysilane film after performing step S3 of forming a high refractive index light propagation layer pattern by laser beam irradiation.
[0085]
The feature of this method is that the ultrashort pulse laser beam is condensed and irradiated into the pre-baked film, so that a higher Δ can be achieved.
[0086]
FIG. 3 shows a third embodiment of the method for producing an organic / inorganic composite waveguide of the present invention.
[0087]
In the present embodiment, after the polysilane compound solution coating step S1, first the polysilane compound solution is pre-baked (150 ° C., 20 minutes), and then the first post-bake (in the range of 200 to 250 ° C. is performed). Step S2C). Next, the post-baked film after step S2C is irradiated with ultraviolet rays through a photomask on which a desired light propagation layer pattern is drawn, and the refractive index change pattern of the pattern is applied to the post-baked film. Step S3C of patterning the polysilane film to form the film is performed. That is, the refractive index is lowered by the ultraviolet irradiation through the ultraviolet transmitting portion of the photomask. The degree of decrease in the refractive index depends on the irradiation energy (irradiation power and irradiation time) of ultraviolet rays. For example, when the above polysilane film is used, it is 0. A relative refractive index difference of about several to 6% can be obtained. The ultraviolet light non-transmissive portion of the photomask, that is, the light propagation layer pattern portion is not changed in refractive index.
[0088]
Next, a second post-bake (320 to 480 ° C., about 30 minutes) step S2D is performed on the film.
[0089]
Finally, a step S3D is performed in which the ultrashort pulse laser beam is focused and irradiated inside the film of the pattern portion that has not been irradiated with the ultraviolet rays, thereby forming a light propagation layer pattern having a high refractive index.
[0090]
According to this method, when the high Δ is obtained in the step S3C of patterning the polysilane film, further high Δ can be realized by laser beam irradiation. In step S3C, a pattern that can become a light propagation layer is formed. In step S3D of forming the light propagation layer pattern, a laser beam is irradiated along the pattern, so that a light propagation layer pattern with high dimensional accuracy is formed. can do.
[0091]
The formation of the light propagation layer by this laser beam irradiation may be in the whole or a part of the ultraviolet irradiation region.
[0092]
FIG. 4 shows a fourth embodiment of the method for producing an organic / inorganic composite waveguide of the present invention.
[0093]
This embodiment is basically the same as the third embodiment of FIG. 3 up to steps S1, S2C, and S3C.
[0094]
The difference from the third embodiment is that step S2D and step S3D are interchanged.
[0095]
That is, the second post-baking step S2D is performed after the step S3D of patterning the polysilane film with ultraviolet rays through a photomask.
[0096]
In this way, a higher Δ can be realized than the method of FIG.
[0097]
The reason for this is that in the third embodiment of FIG. 3, when the second post-baking step S2D is performed after the high Δ pattern is obtained at the stage of the patterning step S3C of the polysilane film, the high Δ is slightly increased. In the fourth embodiment shown in FIG. 4, after obtaining a high Δ pattern, the step of S3D for forming a light propagation layer pattern by irradiating an ultrashort pulse laser beam is performed to increase the Δ. It is because it can plan. Finally, by performing the second post-baking step S2D, the refractive index of the region irradiated with ultraviolet rays is lowered, and as a result, higher Δ can be realized.
[0098]
FIG. 5 shows a fifth embodiment of the method for producing an organic / inorganic composite waveguide of the present invention.
[0099]
In FIG. 5, steps S1, S2C, and S3C are the same as those in the third and fourth embodiments.
[0100]
A step S4 of applying a polymer solution for cladding is provided on the high refractive index pattern portion through which light propagates by ultraviolet irradiation and the low refractive index portions on both side surfaces thereof. Thereafter, step S5 of pre-baking the clad polymer solution (in the range of 100 to 150 ° C. for about 20 minutes) and then post-baking (in the range of 200 to 250 ° C. for 30 minutes) is performed. Finally, step S3D is performed in which an ultrashort pulse laser beam is condensed and irradiated inside the high refractive index pattern portion that has not been irradiated with the ultraviolet rays, thereby forming a light propagation layer that has changed to a high refractive index.
[0101]
The feature of this method is that the light propagation layer is sufficiently covered with the upper cladding layer. Thereby, a further low-loss waveguide can be obtained.
[0102]
Next, the relationship between the post bake temperature and the propagation loss of the polymer film, which are important in realizing an ultra-low loss waveguide, will be described with reference to FIG.
[0103]
FIG. 6 shows the relationship between the propagation loss of the polymer film used in the present invention and the baking temperature.
[0104]
This shows the result of measuring the propagation loss of a polymer film (film thickness: about 9 μm) formed on a Vycor glass substrate (thickness 0.5 mm) at wavelengths of 1300 nm and 1550 nm.
[0105]
The baking temperature on the horizontal axis is that of post-baking (temperature t ° C., 30 minutes) performed after pre-baking (150 ° C., 20 minutes) the polymer solution applied on the Vycor glass substrate (Corning Glass, thickness 0.5 mm). The vertical axis represents the propagation loss of a polymer film prepared at various temperatures t.
[0106]
The polymer solution is a polymer solution obtained by adding 50% of polymethylphenylsilane having a degree of branching of 20% and methylphenylmethoxy ricone to a toluene organic solvent.
[0107]
As can be seen from FIG. 6, the higher the post-bake temperature, the lower the propagation loss of the polymer film. This result has been found by the present inventors. If the temperature is further increased, loss can be reduced, but due to the difference in thermal expansion coefficient from the substrate, distortion occurs in the polymer film and cracks occur, and conversely, propagation loss increases. In order to prevent damage due to the thermal effect, a three-dimensional waveguide is created by a high refractive index change by irradiation with an ultrashort pulse laser beam, and thermal loss is eliminated to achieve low loss.
[0108]
By condensing and irradiating the ultrashort pulse laser beam into the post-baked film, a high Δ light propagation layer with Δ of 1% or more is realized, and the propagation loss at wavelengths of 1300 nm and 1550 nm is shown in FIG. It has been found that an ultra-low loss waveguide of 0.01 dB / cm or less can be realized even lower than the results.
[0109]
The ultrashort pulse laser beam having a wavelength of 800 nm, a pulse width of 200 to 1000 fs, and a pulse repetition of several tens to several hundreds KHz was used. The created three-dimensional waveguide was a single mode waveguide at the measurement wavelength.
[0110]
FIG. 7 shows an experimental example of the dependency of the refractive index and film thickness on the baking temperature of the polymer film used in the present invention. This polymer film is the same as that described in FIG.
[0111]
As shown in FIG. 7, the higher the post-bake temperature, the lower the refractive index and film thickness of the polymer film. The refractive index is a result measured at a wavelength of 1300 nm.
[0112]
When the polymer film of FIG. 7 is irradiated with an ultrashort pulse laser beam, the refractive index of the irradiated film is 0. It turned out to be about several percent to 1% higher. This is thought to be due to the multiphoton absorption phenomenon. This phenomenon in which the refractive index is increased is contrary to the phenomenon in which the refractive index is decreased by increasing the baking temperature in FIG.
[0113]
Next, specific examples of the three-dimensional waveguide of the present invention are shown in FIGS.
[0114]
First, FIG. 8 shows a cross-sectional view of a first three-dimensional waveguide that can be formed by the process described in FIG. 1 (or the process described in FIG. 2).
[0115]
As the substrate 10, a substrate made of glass, plastic, ceramic, semiconductor, ferroelectric, or a combination of these can be used.
[0116]
In particular, since the polymer solution is applied on the substrate and the polymer film 12 is formed by pre-baking and post-baking at a low temperature, the light propagation layer 13 that is changed to a high refractive index by the ultrashort pulse laser beam irradiation is formed. 10 can be a substrate suitable for low temperature processing such as a plastic film, a printed circuit board, etc., and can be formed into a film by applying a polymer solution (spin coating, extrusion coating, etc.) in the atmosphere. It is characterized by being applicable to a large area substrate.
[0117]
Next, FIG. 9 will be described.
[0118]
9A is a cross-sectional view of the second three-dimensional waveguide, FIG. 9B is a refractive index distribution in the cross section along line AA of FIG. 9A, and FIG. 9C is FIG. The refractive index distribution in the BB line cross section of (a) is shown.
[0119]
FIG. 9 shows a cross-sectional view of a three-dimensional waveguide that can be formed using the process of the third embodiment of FIG. 3 or the process of the fourth embodiment of FIG. On the top, polymer films 21, 22A, and 22B for photobleaching of the polysilane compound described above are formed, and the left and right polymer films 22A and 22B are regions in which the refractive index is lowered by ultraviolet irradiation through a photomask. The central polymer film 21 is a region not irradiated with ultraviolet rays, and a light propagation layer 23 that is changed to a high refractive index by irradiation with an ultrashort pulse laser beam is formed in this region.
[0120]
Therefore, the refractive index of the light propagation layer 23 has the highest value η _a In the layer, it has a slight refractive index distribution similar to the power distribution within the spot diameter of the laser beam.
[0121]
The regions of the left and right polysilane films 22A and 22B are irradiated with ultraviolet rays so that the low refractive index η _p (Η _p <Η _a )It has become. The region of the central polymer film 21 that has not been irradiated with ultraviolet rays has a refractive index η _b (Η _p <Η _b <Η _a )It has become.
[0122]
FIG. 10 shows a cross section of the third three-dimensional waveguide.
[0123]
FIG. 10 shows a structure in which the upper clad layer 24 (the refractive index is approximately equal to or lower than that of the polymer films 22A and 22B) is provided on the polymer films 21, 22A and 22B described in FIG. Yes, and produced by the process of the fifth embodiment of FIG.
[0124]
FIG. 11 shows a cross section of the fourth three-dimensional waveguide. This fourth three-dimensional waveguide has a low refractive index between the substrate 20 and the polymer films 21, 22A, 22B in the three-dimensional waveguide of FIG. A sectional view of a structure in which a layer 25 having a refractive index (a refractive index is equal to or lower than that of the polymer films 21 and 22A and the upper cladding layer 24) is shown.
[0125]
When the low refractive index layer 25 and the upper clad layer 24 are formed of a photobleaching polymer material or a polymer material, all the layers can be formed by a coating process and can be formed at a low temperature. can get.
[0126]
FIG. 12 shows a cross section of the fifth three-dimensional waveguide.
[0127]
This is because a low refractive index layer 25 is formed on the substrate 20, and polymer films 22A, 22B, 22C, and 22D irradiated with ultraviolet rays are formed on the low refractive index layer 25, and a pattern portion not irradiated with ultraviolet rays. Polymer films 21A, 21B, and 21C are alternately formed, and light propagation layers 23A, 23B, and 23C having a high refractive index are formed in the polymer films 21A, 21B, and 21C that are not irradiated with the ultraviolet rays, and the polymer film is further formed. In this example, an upper clad layer 24 is formed on 21A, 21B, 21C, 22A, 22B, 22C, and 22D, and an ultraviolet cut layer 26 for cutting ultraviolet rays is formed on the clad layer 24.
[0128]
FIG. 13 shows a cross section of the sixth three-dimensional waveguide.
[0129]
This is a layered structure of a light propagation layer having a high refractive index.
[0130]
That is, a low refractive index layer 25 is formed on the substrate 20, a polymer layer 22F is formed on the low refractive index layer 25, and light propagation layers 23A, 23B, and 23C are formed in the polymer layer 22F. A polymer layer 22G is provided on the polymer layer 22F via an intermediate layer 27 having a low refractive index (the refractive index is lower than that of the polymer layer 22F), and light propagation layers 23D and 23E are formed in the polymer layer 22G. Furthermore, a laminated structure waveguide in which an upper clad layer 24 is formed on the polymer layer 22G.
[0131]
The present invention is not limited to the above embodiment. For example, the light propagation layer having a high refractive index may be provided on the surface of the polymer film in addition to the inside of the polymer film. A low refractive index polymer layer may be formed on the surface.
[0132]
The pattern of the light propagation layer with a high refractive index is composed of a linear pattern, a curved pattern, and a combination of these patterns. Optical directional coupling circuit, optical star coupler, optical ring resonance circuit, optical filter, array lattice type A grating, a Y-branch optical circuit, or an optical circuit combining these may be configured.
[0133]
The polymer film may be a polysilane compound, a polysilane compound added with a silicone compound, or a polysilane compound added with a silicone compound and a photoacid generator (tridian, peroxide, etc.). In addition to the structure shown in FIG. 13, the light propagation layer having a higher refractive index may be provided in a polymer layer that is further laminated in multiple layers. In that case, the intermediate layer 27 is not necessarily provided.
[0134]
As shown in FIG. 14, a low-refractive index layer 35 is formed on a substrate 30, and ultraviolet light is passed through the photomask on which the first light propagation layer pattern is drawn on the low-refractive index layer 35. After irradiation, the first light propagation layer 32 having a high refractive index and the side cladding layers 31A and 31B having a reduced refractive index are formed on the side surfaces thereof, and then an ultrashort pulse laser beam is applied to the first light propagation layer 32. By condensing and irradiating the light to change to the light propagation layer 33 having a higher refractive index and further forming the upper clad layer 34, a light propagation layer having a high pattern dimensional accuracy can be realized with a higher Δ.
[0135]
【The invention's effect】
In short, the present invention has the following effects.
(1) A loss comparable to or lower than that of a glass waveguide can be realized, and is manufactured by a manufacturing method that is overwhelmingly simple and inexpensive as compared with a conventional glass waveguide manufacturing method. Can do. That is, in the atmosphere, it can be produced by a combination of a coating process, a heating process at 500 ° C. or lower, an ultrashort pulse laser beam irradiation process, and in some cases, an ultraviolet irradiation process. Further, since it can be formed on a very large substrate such as a plastic film or a printed circuit board, a highly integrated high-performance optical circuit can be configured. Furthermore, since it can be produced in a low temperature process, there is little deterioration in optical characteristics without causing warpage of the substrate.
(2) Absorption loss due to CH groups can be almost eliminated by mineralizing at a temperature of 320 to 480 ° C., and by irradiating with an ultrashort pulse laser beam. Type optical circuit can be realized.
(3) Stability of refractive index due to temperature change is also improved by making the polysilane film (or polysilane film added with silicone or photoacid generator) inorganic by baking at a post-bake temperature of 320 to 480 ° C. In addition, further inorganicization can be achieved by irradiation with an ultrashort pulse laser beam, and a light propagation layer with little change in refractive index with respect to temperature change can be realized.
(4) Start the 3D waveguide from the application of polymer solution, make it a polymer film, make it inorganic, and form a light propagation layer by laser beam irradiation, etc. to realize an optical circuit with low cost and ultra-low loss can do.
(5) After forming a first light propagation layer pattern having a high refractive index by irradiating ultraviolet rays on the photobleaching polymer layer through a photomask on which the first light propagation layer pattern is drawn, By irradiating an ultrashort pulse laser beam along one light propagation layer pattern, the refractive index of the first light propagation layer is further increased, and a second light propagation layer with good pattern dimensional accuracy is provided as the first light propagation layer. Therefore, it is possible to realize an ultra-low loss / ultra-compact / high Δ waveguide with low scattering loss and an optical circuit using the same.
(6) Since a substrate having a low heat-resistant temperature such as a printed circuit board or a plastic film can be used as the substrate, an optical wiring circuit and an optical signal processing are provided on a substrate on which an electrical component such as LSI, L, C, or R is mounted. Can be realized with ultra-low loss.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of the present invention.
FIG. 2 is a diagram showing a second embodiment of the present invention.
FIG. 3 is a diagram showing a third embodiment of the present invention.
FIG. 4 is a diagram showing a fourth embodiment of the present invention.
FIG. 5 is a diagram showing a fifth embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the propagation loss of a polymer film and the baking temperature in the present invention.
FIG. 7 is a diagram showing the dependency of the refractive index and film thickness of a polymer film on the baking temperature in the present invention.
FIG. 8 is a cross-sectional view of a first three-dimensional waveguide manufactured by the method of the present invention.
FIG. 9 is a diagram showing a cross section of a second three-dimensional waveguide manufactured by the method of the present invention and its refractive index.
FIG. 10 is a cross-sectional view of a third three-dimensional waveguide manufactured by the method of the present invention.
FIG. 11 is a cross-sectional view of a fourth three-dimensional waveguide manufactured by the method of the present invention.
FIG. 12 is a cross-sectional view of a fifth three-dimensional waveguide manufactured by the method of the present invention.
FIG. 13 is a cross-sectional view of a sixth three-dimensional waveguide manufactured by the method of the present invention.
FIG. 14 is a cross-sectional view of a seventh three-dimensional waveguide manufactured by the method of the present invention.
[Explanation of symbols]
10, 20, 30 substrate
12 22 polymer membrane
21 Polymer membrane
23 Light propagation layer

Claims (19)

A light propagation layer pattern in which an ultrashort pulse laser beam with a pulse width of 1000 fs or less is condensed and changed to a high refractive index is formed on the surface or inside of the polymer film made of a polysilane compound. Organic / inorganic composite waveguide characterized by 2. The organic / inorganic composite waveguide according to claim 1, wherein a silicone compound is added to the polysilane compound at a desired compounding ratio. 3. The organic / inorganic composite waveguide according to claim 1, wherein the polysilane compound is bonded to a hydrocarbon group, an alkoxy group, or a hydrogen atom in addition to the Si atom. The organic-inorganic composite waveguide according to any one of claims 1 to 3, wherein a part of or all of the polysilane compound is deuterated. The organic-inorganic composite waveguide according to any one of claims 1 to 3, wherein a part or all of the polysilane compound is fluorinated. The organic / inorganic composite waveguide according to claim 2, wherein the silicone compound is made of a crosslinkable or alkoxy group. 3. The organic / inorganic composite waveguide according to claim 2, wherein a part or all of the silicone compound is deuterated. 3. The organic / inorganic composite waveguide according to claim 2, wherein a part or all of the silicone compound is fluorinated. The polymer film consists of a pattern in which a refractive index is lowered by irradiation with ultraviolet light through a photomask having a desired pattern shape and a pattern in a high refractive index area in which the refractive index is not lowered without being irradiated with ultraviolet light. The ultrashort pulse laser beam is condensed and irradiated on a high refractive index region not irradiated with ultraviolet rays, and a light propagation layer having a refractive index higher than the refractive index of the polymer film is formed. The organic-inorganic composite waveguide according to any one of 1 to 8. The organic / inorganic composite waveguide according to any one of claims 1 to 9, wherein a polymer film for cladding having a refractive index lower than that of the polymer film is formed on a surface of the polymer film. The organic / inorganic composite waveguide according to any one of claims 1 to 10, wherein the polymer film is heat-treated in a range of 320 to 480 ° C. The organic / inorganic composite waveguide according to claim 11, wherein the heat treatment of the polymer film is performed either before or after the irradiation with the ultrashort pulse laser beam. The organic / inorganic composite waveguide according to claim 1, wherein the polymer film is formed on a substrate. The organic / inorganic composite waveguide according to claim 1, wherein the polymer film is laminated in a plurality of layers. A step of applying a solution of a polysilane compound dissolved in an organic solvent on a substrate, a step of obtaining a cured polymer film by heat treatment in a temperature range of 100 to 480 ° C., and a pulse width on the surface or inside of the polymer film While condensing and irradiating an ultra-short pulse laser beam of 1000 fs or less, the pattern of the light propagation layer changed to a high refractive index by relatively changing the position of the condensing point and the substrate is formed on the surface or inside of the polymer film. A method for producing an organic / inorganic composite waveguide having a step of forming a substrate. 16. The method for producing an organic / inorganic composite waveguide according to claim 15, wherein a silicone compound is added to a solution of a polysilane compound dissolved in an organic solvent at a desired compounding ratio. 16. The heat treatment step is narrowed to a pre-baking temperature range of 100 to 250 ° C., and instead, a step of post-baking at a temperature range of 320 to 480 ° C. is provided after the step of forming the pattern of the light propagation layer. Manufacturing method of organic / inorganic composite waveguide. In addition to the pre-baking process, place a photomask with a desired pattern shape on the polymer film and irradiate it with ultraviolet light. A step of forming a pattern in which the refractive index did not decrease is provided, and after that step, an ultrashort pulse laser beam is condensed and irradiated on a region not irradiated with the ultraviolet light, while the condensing point and the substrate are 18. The method for producing an organic / inorganic composite waveguide according to claim 17, further comprising a step of forming a pattern of the light propagation layer whose position is relatively changed to change to a high refractive index and a step of post-baking. 19. The method for producing an organic / inorganic composite waveguide according to claim 18, wherein the post-baking step is provided before the step of forming the pattern of the light propagation layer by the ultrashort pulse laser beam irradiation.

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