JP3815811B2 - Refractive index modulation element and refractive index modulation method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は熱印加によって屈折率を変調させて光制御を行う屈折率変調素子に関する。
【０００２】
【従来の技術】
何らかの刺激を外部より印加して光を変調させて光の伝搬を制御する目的で種々の試みが行われている。例えば、ニオブ酸リチウム、ＰＬＺＴなどの電気光学結晶と呼ばれる物質に外部より電界を印加して屈折率を変化させる、ポッケルス効果、或いはカー効果と呼ばれる現象を生じさせる方式、二酸化テルル、モリブデン酸鉛等の結晶に外部より音波を印加して結晶中にひずみを発生させ光弾性効果を生じさせることを利用する方式が知られている。しかしこれら現象を利用する素子は結晶を用いなければならず、材料上の問題があることは周知である。また、光を制御手段とする非線形光学現象を利用する方式も考案され検討が進められてはいるが、材料上の問題は解決されてはおらず、実用には至ってない。
【０００３】
他に熱的に屈折率が変化する材料を用いる方式が知られている。例えば、チタニウムドープニオブ酸リチウム、イオン交換ガラス等の無機材料、有機高分子系の平面導波路型デバイスが検討されその機能が確認されている（J. Lightwave Technology vol.7, p449-453, 1989)。また、熱刺激屈折率変調材料として、ポリカーボネート、ポリイミド、ポリアクリレート等の樹脂をもちいることが知られている（ＥＰ ６４２０５２）。
【０００４】
有機樹脂を光学用途に用いるときの問題点の一つに、多くの有機樹脂は吸水吸湿性があり、これに伴う光学的に制御不能な屈折率変化を生じることにある。
【０００５】
他方、オルガノポリシロキサン樹脂は、従来例えば特開昭６１−２４０２０７号に開示されているような単に光の透過層としての役割をになったパッシィブ材料としては知られていたが、熱印加を外部刺激として屈折率を変調させるようなアクティブ材料としては知られていない。
【０００６】
【発明が解決しようとする課題】
熱を屈折率変調手段とする屈折率変調素子に使用する屈折率変調材料として、屈折率変化が大きく且つ環境安定性に優れ、例えば空気中の水蒸気を吸収して屈折率が変化するということが殆どなく、屈折率変調が容易な材料が求められている。
本発明の目的は、上述の様な屈折率変調材料として特定のポリシロキサンを屈折率変調材料として用いた屈折率変調素子を提供することにある。
【０００７】
【課題を解決するための手段】
本発明は、少なくとも、屈折率変調材料からなる媒体を有する屈折率変調素子であって、屈折率を熱的に変調させるものにおいて、前記屈折率変調材料が次の（１）及び（２）の条件を有するポリシロキサンからなることを特徴とする屈折率変調素子である。
（１）３５０nm〜１６００nmの波長範囲において平均の分光透過率が８０％以上でありかつ特定の光吸収帯を有さないこと。
（２）屈折率の温度依存性が−０．００１／℃〜−０．００００５／℃の範囲にあること。
【０００８】
本発明における屈折率変調素子とは、何らかの刺激を外部より印加させることにより光の屈折率を変化させて光の伝播を制御させる機能を有するもののことを指す。本発明の屈折率変調素子は、熱により屈折率を変調させる屈折率変調材料からなる媒体だけから構成されていても良く、またこの屈折率変調材料からなる媒体に光搬送媒体が接して構成されていても構わない。
【０００９】
本発明における屈折率変調素子は、３５０nm〜１６００nmの波長範囲において平均の分光透過率が８０％以上でありかつ特定の光吸収帯を有さない。光通信等の光技術で使用されるレーザー波長の多くがこの範囲であるから、これは好都合な性質である。一般に、ケイ素系樹脂は他の有機樹脂に較べて吸水吸湿性が低いから光学的に制御不能な屈折率変化を生じにくい。
【００１０】
前記屈折率変調材料は、Ｒn ＳｉＯ(4-n)/2 （但し、ｎは０．５以上、３未満の数、Ｒは炭素原子数１〜１８の脂肪族基または芳香族基を表す）で示される平均組成を有するケイ素樹脂であることが好ましい。
【００１１】
即ち、本発明に用いられるポリシロキサンとしては一般式Ｒ′m ＳｉＯ(4-m)/2 で示される単位を主体に構成されるケイ素樹脂を好適に用いることができる。ここにｍは０〜３の数をとり、Ｒ′は炭素原子数１〜１８の脂肪族基又は芳香族基を表す。
本発明において、加水分解性基を２個分子中に有するケイ素化合物の加水分解縮合によって生成されたケイ素系高分子を用いることができ、これはポリシロキサンと称される樹脂群である。また、加水分解性基が１個のものと３或いは４個を有するケイ素系化合物から同様にして合成される樹脂を本発明で用いることができ、これらはシリコーン業界ではＭＴレジン、或いはＭＱレジンと呼ばれる樹脂を生成することができ、加水分解性基が３個のもの単独からはＴレジン或いはポリシルセスキオキサンと呼ばれる樹脂を生成することができる。前述の一般式において、４−ｎが３より大きいものは３個加水分解性基を有するケイ素化合物と４個の加水分解性基を有する化合物との共重合体である。
【００１２】
本発明のポリシロキサンの屈折率は、光伝搬媒体によって適宜選択されねばならない。同一有機基をケイ素上の置換基とする場合、屈折率はそれほど大きな変化はないが、有機基の種類を変えることによってポリシロキサンの屈折率は変えることができる。例えば、ポリシロキサンでは、Ｒとしてメチル、フェニルを用いることによりポリ（ジメチル−ジフェニル）シロキサンでは屈折率ｎｄが１．４０９〜１．５２、ポリメチルフェニルシロキサンでは１．５５０、ポリ（ジメチル−メチルフェニル−ジフェニル）シロキサンでは１．４０９〜１．５５０である。このように、屈折率を高くしたいときは芳香族基を、低くしたいときには脂肪族基を用いればよく、この両者の濃度によって基本的屈折率は調整されうる。更に、屈折率を高めたいときはシロキサンと共重合しうる公知の金属を導入し、或いは塩素、臭素を芳香族基に置換させる事ができ、又低下させたいときはホウ素等の金属類の化合物の共重合、或いはフッ素を置換した脂肪族基を用いることができる。当然、後述の分光透過率、或いは光吸収帯を考慮して選択される事は言うまでもない。従って、一般式におけるＲとして、炭素原子数１〜１８の直鎖或いは分岐であるかを問わず飽和炭化水素基、例えばメチル、エチル、プロピル、ブチル、アミル、ヘキシル、２−エチルヘキシル、ドデシル、オクタデシル等、アルケニル基、例えばビニル、アリル等、アリール基、例えばフェニル、トリル等、及び例えばトリフルオロプロピル、ヘプタフルオロペンチル、ナノフルオロヘキシル等で代表されるフロロ炭化水素基、クロロメチル、クロロエチル等、炭素数１〜１８の直鎖或いは分岐であるかを問わず飽和炭化水素基ハロゲン置換体をあげることができる。
【００１３】
本発明に用いるポリシロキサンは、架橋されていないものの他、架橋され硬化されているものも推奨される。架橋方法としては、重合時に一部に加水分解性が異なる加水分解性基を導入し、重合終了後これを縮合させて架橋させることも、架橋する際に架橋剤を加え、これを介して架橋させることもできる。このような架橋剤としては１分子中に複数個の加水分解性基を有するケイ素化合物であれば特に限定するものではない。加水分解性基としては水酸基、メトキシ、エトキシ、プロポキシキ、ブトキシ基が挙げられ、メチル、エチル、プロピル、ブチル、アミル、ヘキシル、フェニル、トリル基が１〜２個置換していてもよい。必ずしも触媒が必要ではないが、通常ケイ素樹脂の硬化に用いられる触媒の使用を妨げるものではなく、硬化に要する時間、硬化温度等を考慮してジブチル錫ジアセテート等アルキル錫有機酸塩から触媒を選ぶのがよい。
【００１４】
また、架橋構造成形時に反応系から反応に伴う揮発性低分子化合物が生成しない付加型の反応形式が一般には好ましい場合には、そのような反応形式として−ＳｉＨとビニル基の反応、水酸基とイソシアナートの反応、エポキシとアミン或いは酸無水物等の反応、ビニル基の過酸化物あるいは光等による反応などが好ましい例として挙げられる。この組み合わせのうち、一方をケイ素樹脂中に重合時に予め共重合し、他方を架橋剤中に含ませておくことができる。
【００１５】
架橋反応において、必ずしもそれぞれの置換基を有するポリマー同志を反応させる必要はない。２官能性或いは多官能性低分子を介して架橋することを妨げるものではない。例えば、カルビノール残基を有する樹脂をキシリデンジイソシアナート或いはシクロヘキサンジイソシアナート等を介して架橋することができる。特に、室温近辺で硬化させる必要がある場合は、−ＳｉＨとビニル基をそれぞれに含む樹脂の組み合わせ或いは樹脂と架橋剤の組み合わせの、白金を触媒とするヒドロシリル化が好ましい。ヒドロシリル化に供しうる白金系触媒としては白金酸塩類が挙げられるがこれに限定されるものではない。
【００１６】
熱による屈折率変調度は前述の樹脂構造に大きく依存する。最も変調度を大きく取りたい場合、Ｒn ＳｉＯ(4-n)/2 においてｎ＝２のポリシロキサン系の樹脂を主成分とする樹脂を選択し、変調度の小さい場合はｎ＜１、つまり３個の加水分解性基と４個の加水分解性基から成る共重合体を主成分とする樹脂を選択することができ、このように組成を変化させることにより、屈折率を０．００１から０．００００５の範囲で目的に応じて調節することができる。熱屈折率変調は熱膨張と線形関係にあるため、高分子科学において知られているごとく、架橋を高度に行うか軽度に行うことにより屈折率変調度は調節できる。
【００１７】
本発明のポリシロキサンは、特殊な有機基を含まない限り、可視光領域には特定の吸収帯は有せず、ケイ素に水酸基が結合していないかぎり、１５５０nm付近の吸収帯は存在しない。
【００１８】
本発明に使用する樹脂の製造方法としては Silicon-Based Polymer Science Ed., Jhon M. Ziegler & F. W. Gordon Fearon, ACS series 224, The American Chemical Society, 1990、の７１ページに記載のシロキサンポリマー合成方法を始めとして公知の方法を用いることができる。
【００１９】
本発明の屈折率変調素子は単一の屈折率変調材料のみで構成されていてもよく、この場合は、例えば光ファイバーとして使用できる。
【００２０】
本発明の屈折率変調素子は屈折率変調材料からなる媒体に光搬送媒体が接して構成されていてもよく、この場合は、例えば光スイッチ等として使用できる。
【００２１】
屈折率変調素子が屈折率変調材料からなる層に光搬送媒体が接して構成される場合次の様な設定をすることができる。
ａ）屈折率変調材料と光搬送媒体の屈折率を予め一致させて構成する。この場合、例えば熱印加により屈折率変調材料の屈折率を光搬送媒体の屈折率より低くすることができる。
ｂ）屈折率に差のある屈折率変調材料と光搬送媒体により構成する。この場合、例えば光搬送媒体とその屈折率より高い屈折率の屈折率変調材料から屈折率変調素子を構成させ、熱印加により低屈折率に変調させ両者の屈折率を合致させることができる。
【００２２】
本発明の屈折率変調素子は、実用上は屈折率変調素子に熱を印加する手段を伴って使用される。
前記熱印加手段は、電気的に発熱しうる発熱体であれば特に限定されるものではない。熱転写プリンターに使用される熱印加手段であっても差し支えない。
【００２３】
屈折率変調素子と印加手段を備えた装置を製作する場合、各種方法が可能であるが、例えば次の様な方法が挙げられる。
（１）屈折率変調素子に使用されたポリシロキサンが硬化した後に熱印加機能を有するデバイスをこのポリシロキサンに接触させて設ける方法。
（２）屈折率変調素子に使用されたポリシロキサンの硬化途中に熱印加機能を有するデバイスをこのポリシロキサンに接触させて設ける方法。
（３）熱印加手段の種類によっては蒸着等の気相加工方法により屈折率変調素子に熱印加手段を設けることもできる。
従来の有機系樹脂による屈折率変調素子の製造において、高温条件下で行なわれる蒸着を選択した場合、有機系樹脂の耐熱性の問題があり、樹脂の種類によっては蒸着を行なうことが難しく、場合によっては冷却しながら行なう等の方法がとられていました。ポリシロキサンを使用した場合は、この点は余り大きな問題とはならず、有機系樹脂に対して有利である。
【００２４】
本願発明の屈折率変調素子は、２５０℃以下の温度で熱印加するのがよい。温度範囲については、好適には−７０〜２５０℃の範囲で熱印加による屈折率変調が可能である。ポリシロキサンの熱安定性及び屈折率の温度依存性が安定しているのがこの温度範囲であるからである。
【００２５】
本発明の屈折率変調素子は、使用される屈折率変調材料であるケイ素系樹脂の種類によっても異なるが、屈折率を０．０２以下の範囲で変調することもできる。この変調範囲は、０．００８以下の範囲で使用されることがより望ましい。変調できる範囲は、ポリシロキサンの使用可能温度範囲の影響も大きく受けている。つまり、２５０℃以下の実用的温度で印加した場合の変調範囲が上記の範囲と言うことになる。
【００２６】
（実施例１）
（ビニル基含有ケイ素樹脂）
３００mLの丸底フラスコに、１，３−ジビニル−１，１，３，３−テトラメチルジシロキサン（１４．９ｇ，０．０８モル）、蒸留水（１０．１ｇ，０．５６モル）、塩酸（３．５ｇ，０．０９６モル）及びエタノール（６．５ｇ，０．１４モル）を入れ５０℃で攪拌した。滴下ロートにフェニルトリエトキシシラン（９．６ｇ，０．０４モル）、メチルトリメトキシシラン（３８．１ｇ，０．２８モル）及びエタノール（６．５ｇ，０．１４モル）を入れ、前記攪拌している丸底フラスコ中の混合液に滴下し、２時間還流した。還流後常温に冷却した後、ヘキサンを加え有機層をこれが中和されるまで洗浄し、無水硫酸マグネシウムを添加して水分を取り除き、塩をろ過した後有機溶媒を取り除いた。
【００２７】
（ＳｉＨ含有ケイ素樹脂）
５００mLの丸底フラスコに、１，１，３，３−テトラメチルジシロキサン（５０．４ｇ，０．３７５モル）、蒸留水（４８ｇ，３モル）、塩酸（２４ｇ，０．６６モル）及びメタノール（１５ｇ，０．４７モル）を入れ１０℃以下で攪拌した。テトラメトキシシラン（１１４．２ｇ，０．７５モル）を前記フラスコ中の混合液に１０℃以下で滴下し、２時間室温で攪拌した。以下、溶液の中和、塩、溶媒の除去は上記と同様の手法で行った。
【００２８】
以上の手法で合成したビニル基含有ケイ素樹脂とＳｉＨ含有ケイ素樹脂を混合し、Ｂ型回転粘度計（トキメック株式会社）で室温で粘度を測定したところ、４，５００cps であった。これに白金触媒を混合し均一になるまで攪拌した後、混合物を８０℃で２時間加熱させることによって硬化させた。このようにして得られたケイ素樹脂硬化物は、分光光度計、Ｕ−３２１０（日立製作所）で透過率を測定したところ、３５０nm〜１６００nmの範囲でいずれの波長においても８５％以上の透過性を有した。２０℃でのｄ線５８７．６nmに対する屈折率を高精度屈折計、ＫＰＲ−２００（カルニュウ光学株式会社）で測定したところ、ｎｄは１．４３１９であり、また、試料の温度変化から屈折率の温度依存性は−３．２×１０-4／℃であった。
【００２９】
シリコンウェハー上にシリカガラス（nd＝１．４５８６）の導波路を形成し、上記ケイ素樹脂をその上に薄膜状に積層した。シリコンウェハーを１５０℃に加熱し、導波路を伝搬する光がケイ素樹脂より射出する強度を光ファイバーを通して分光光度計で検出したところ、射出強度が加熱前に比べて２５％以下になった。
【００３０】
（実施例２）
（ビニル基含有ケイ素樹脂）
前記フェニルトリエトキシシランに代えてフェニルトリクロロシラン（１６．８ｇ，０．７モル）を用いたほかは実施例１と同様にしてビニル基含有ケイ素樹脂合成した。
【００３１】
（ＳｉＨ含有架橋剤）
フェニルトリメトキシシラン（２９．７４ｇ，０．１５モル）とテトラメチルジシロキサン（６０．４５ｇ，０．４５モル）、を使用した他は実施例１のＳｉＨ含有ケイ素樹脂の製法と同様な方法によりＳｉＨ含有架橋剤を合成した。
【００３２】
以上の手法で合成したビニル基含有ケイ素樹脂とＳｉ−Ｈ含有架橋剤、及び白金触媒を混合し１２０℃で２時間加熱硬化させた。このようにして得られたケイ素樹脂硬化物について実施例１と同様に光学性質を測定すると、３５０nm〜１６００nm範囲でいずれの波長においても８５％以上の透過性を示し、２５℃でのｎｄは１．５１６０であり、屈折率の温度依存性は−３．５×１０-4／℃であった。シリカガラスの代わりにＢＫ−７ガラス（ｎｄ＝１．５１６３）を用いて導波路を形成し実施例１同様に積層した。約１００℃に加熱すると導波路からの射出強度は加熱前と比較すると３倍に増加した。
【００３３】
【発明の効果】
本発明により、光伝搬媒体と屈折率を予め一致させておき、熱印加にて屈折率変調させる、或いは異なる屈折率を熱印加屈折率変調させて光伝搬媒体の屈折率と一致させる熱変調型光スイッチ、分岐干渉型光スイッチ、方向性結合型光スイッチが製造され、従来知られている熱可塑性樹脂を用いた素子より変調範囲の広い素子が提供される。また、単一の屈折率変調材料のみからなる屈折率変調素子、例えば光ファイバーの場合、この素子の温度を変化させることにより屈折率を変化させ、これにより光の透過量を変化させることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refractive index modulation element that performs light control by modulating a refractive index by applying heat.
[0002]
[Prior art]
Various attempts have been made to control light propagation by applying some stimulus from the outside to modulate light. For example, a method that causes a phenomenon called Pockels effect or Kerr effect by applying an electric field to a substance called electro-optic crystal such as lithium niobate or PLZT from the outside, tellurium dioxide, lead molybdate, etc. There is known a system that utilizes the application of a sound wave from the outside to the crystal to generate a strain in the crystal to generate a photoelastic effect. However, it is well known that elements utilizing these phenomena must use crystals and have material problems. Further, although a method using a nonlinear optical phenomenon using light as a control means has been devised and studied, the material problem has not been solved and has not been put into practical use.
[0003]
Another known method uses a material whose refractive index changes thermally. For example, an inorganic material such as titanium-doped lithium niobate, ion exchange glass, and an organic polymer-based planar waveguide device have been studied and their functions have been confirmed (J. Lightwave Technology vol.7, p449-453, 1989). ). In addition, it is known that a resin such as polycarbonate, polyimide, polyacrylate or the like is used as a heat-stimulated refractive index modulation material (EP 642052).
[0004]
One of the problems when using organic resins in optical applications is that many organic resins are water-absorbing, resulting in optically uncontrollable refractive index changes.
[0005]
On the other hand, an organopolysiloxane resin has been known as a passive material that has merely served as a light transmission layer as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-240207. It is not known as an active material that modulates the refractive index as a stimulus.
[0006]
[Problems to be solved by the invention]
As a refractive index modulation material used for a refractive index modulation element using heat as a refractive index modulation means, the refractive index changes greatly and is excellent in environmental stability. For example, the refractive index changes by absorbing water vapor in the air. There is almost no need for a material that can be easily modulated in refractive index.
An object of the present invention is to provide a refractive index modulation element using a specific polysiloxane as the refractive index modulation material as described above.
[0007]
[Means for Solving the Problems]
The present invention provides a refractive index modulation element having at least a medium made of a refractive index modulation material, which thermally modulates the refractive index, wherein the refractive index modulation material includes the following (1) and (2): It is a refractive index modulation element characterized by comprising polysiloxane having conditions.
(1) The average spectral transmittance is not less than 80% in the wavelength range of 350 nm to 1600 nm and does not have a specific light absorption band.
(2) The temperature dependence of the refractive index is in the range of -0.001 / ° C to -0.00005 / ° C.
[0008]
The refractive index modulation element in the present invention refers to an element having a function of controlling the propagation of light by changing the refractive index of light by applying some stimulus from the outside. The refractive index modulation element of the present invention may be composed only of a medium made of a refractive index modulation material that modulates the refractive index by heat, and is constructed by contacting an optical carrier medium with the medium made of this refractive index modulation material. It does not matter.
[0009]
The refractive index modulation element of the present invention has an average spectral transmittance of 80% or more in the wavelength range of 350 nm to 1600 nm and does not have a specific light absorption band. This is an advantageous property because many of the laser wavelengths used in optical technologies such as optical communications are in this range. In general, silicon-based resins are less likely to cause optically uncontrollable refractive index changes because they are less hygroscopic than other organic resins.
[0010]
The refractive index modulation material is R n SiO (4-n) / 2 (where n is a number of 0.5 or more and less than 3, and R represents an aliphatic group or an aromatic group having 1 to 18 carbon atoms). It is preferable that it is a silicon resin which has the average composition shown by this.
[0011]
That is, as the polysiloxane used in the present invention, a silicon resin mainly composed of a unit represented by the general formula R ′ m SiO (4-m) / 2 can be preferably used. Here, m is a number from 0 to 3, and R ′ represents an aliphatic group or an aromatic group having 1 to 18 carbon atoms.
In the present invention, a silicon-based polymer produced by hydrolytic condensation of a silicon compound having two hydrolyzable groups in the molecule can be used, which is a resin group called polysiloxane. In addition, a resin synthesized in the same manner from a silicon-based compound having one hydrolyzable group and three or four hydrolyzable groups can be used in the present invention, and these resins can be used in the silicone industry as MT resin or MQ resin. A resin called “T-resin” or “polysilsesquioxane” can be produced from a resin having three hydrolyzable groups alone. In the above general formula, 4-n is larger than 3 is a copolymer of a silicon compound having 3 hydrolyzable groups and a compound having 4 hydrolyzable groups.
[0012]
The refractive index of the polysiloxane of the present invention must be appropriately selected depending on the light propagation medium. When the same organic group is a substituent on silicon, the refractive index does not change so much, but the refractive index of the polysiloxane can be changed by changing the type of the organic group. For example, polysiloxane uses methyl and phenyl as R, so that poly (dimethyl-diphenyl) siloxane has a refractive index nd of 1.409 to 1.52, polymethylphenylsiloxane 1.550, poly (dimethyl-methylphenyl). In the case of -diphenyl) siloxane, it is 1.409 to 1.550. As described above, an aromatic group may be used to increase the refractive index, and an aliphatic group may be used to decrease the refractive index, and the basic refractive index can be adjusted by the concentration of both. Furthermore, when it is desired to increase the refractive index, a known metal that can be copolymerized with siloxane can be introduced, or chlorine or bromine can be substituted with an aromatic group, and when it is desired to decrease, a compound of a metal such as boron. Or an aliphatic group substituted with fluorine can be used. Of course, it goes without saying that the spectral transmittance or the light absorption band described later is selected. Therefore, as R in the general formula, a saturated hydrocarbon group, for example, methyl, ethyl, propyl, butyl, amyl, hexyl, 2-ethylhexyl, dodecyl, octadecyl, regardless of whether it is linear or branched having 1 to 18 carbon atoms. Alkenyl groups such as vinyl and allyl, aryl groups such as phenyl and tolyl, and fluorohydrocarbon groups such as trifluoropropyl, heptafluoropentyl and nanofluorohexyl, chloromethyl and chloroethyl A saturated hydrocarbon group halogen-substituted product can be used regardless of whether it is linear or branched.
[0013]
As the polysiloxane used in the present invention, a non-crosslinked polysiloxane and a crosslinked and cured polysiloxane are also recommended. As a crosslinking method, a hydrolyzable group having a different hydrolyzability is partially introduced at the time of polymerization, and this is condensed and crosslinked after the completion of the polymerization. It can also be made. Such a crosslinking agent is not particularly limited as long as it is a silicon compound having a plurality of hydrolyzable groups in one molecule. Examples of the hydrolyzable group include a hydroxyl group, methoxy, ethoxy, propoxy, and butoxy group, and one or two methyl, ethyl, propyl, butyl, amyl, hexyl, phenyl, and tolyl groups may be substituted. Although a catalyst is not necessarily required, it does not prevent the use of a catalyst usually used for curing a silicon resin, and a catalyst from an alkyltin organic acid salt such as dibutyltin diacetate is considered in consideration of the time required for curing, the curing temperature, etc. It is good to choose.
[0014]
In addition, when an addition-type reaction mode in which a volatile low-molecular compound accompanying the reaction is not generated from the reaction system at the time of forming a crosslinked structure is generally preferable, such a reaction mode is a reaction between -SiH and a vinyl group, a hydroxyl group and an isocyanate. Preferred examples include the reaction of nate, the reaction of epoxy and amine or acid anhydride, the reaction of vinyl group peroxide or light. Of these combinations, one can be copolymerized in advance in the silicon resin during polymerization and the other can be included in the crosslinking agent.
[0015]
In the crosslinking reaction, it is not always necessary to react the polymers having the respective substituents. It does not prevent cross-linking via a bifunctional or polyfunctional small molecule. For example, a resin having a carbinol residue can be crosslinked via xylidene diisocyanate or cyclohexane diisocyanate. In particular, when it is necessary to cure at around room temperature, platinum-catalyzed hydrosilylation of a combination of a resin containing -SiH and a vinyl group or a combination of a resin and a crosslinking agent is preferable. Platinum-based catalysts that can be used for hydrosilylation include, but are not limited to, platinates.
[0016]
The degree of refractive index modulation due to heat greatly depends on the resin structure. When it is desired to obtain the largest degree of modulation, a resin whose main component is a polysiloxane resin of n = 2 in R n SiO (4-n) / 2 is selected, and when the degree of modulation is small, n <1, that is, A resin mainly composed of a copolymer composed of 3 hydrolyzable groups and 4 hydrolyzable groups can be selected, and the refractive index can be changed from 0.001 by changing the composition in this way. It can be adjusted according to the purpose in the range of 0.00005. Since thermal refractive index modulation has a linear relationship with thermal expansion, as is known in polymer science, the refractive index modulation can be adjusted by performing crosslinking highly or lightly.
[0017]
The polysiloxane of the present invention does not have a specific absorption band in the visible light region unless it contains a special organic group, and does not have an absorption band near 1550 nm unless a hydroxyl group is bonded to silicon.
[0018]
As a method for producing the resin used in the present invention, the siloxane polymer synthesis method described on page 71 of Silicon-Based Polymer Science Ed., Jhon M. Ziegler & FW Gordon Fearon, ACS series 224, The American Chemical Society, 1990, is used. A known method can be used as the beginning.
[0019]
The refractive index modulation element of the present invention may be composed of only a single refractive index modulation material. In this case, for example, it can be used as an optical fiber.
[0020]
The refractive index modulation element of the present invention may be configured such that a light transport medium is in contact with a medium made of a refractive index modulation material. In this case, for example, it can be used as an optical switch or the like.
[0021]
When the refractive index modulation element is configured by contacting the light transport medium with a layer made of a refractive index modulation material, the following settings can be made.
a) The refractive index modulation material and the optical transport medium are configured to have the same refractive index in advance. In this case, for example, the refractive index of the refractive index modulation material can be made lower than the refractive index of the light carrying medium by applying heat.
b) It is composed of a refractive index modulation material having a difference in refractive index and an optical carrier medium. In this case, for example, a refractive index modulation element can be formed from a light transport medium and a refractive index modulation material having a higher refractive index than that of the optical conveyance medium, and the refractive index of both can be matched by modulating to a low refractive index by applying heat.
[0022]
The refractive index modulation element of the present invention is practically used with means for applying heat to the refractive index modulation element.
The heat applying means is not particularly limited as long as it is a heating element that can generate heat electrically. It may be a heat application means used in a thermal transfer printer.
[0023]
When manufacturing a device including a refractive index modulation element and application means, various methods are possible. For example, the following methods can be mentioned.
(1) A method of providing a device having a heat application function in contact with the polysiloxane after the polysiloxane used in the refractive index modulation element is cured.
(2) A method of providing a device having a heat application function in contact with the polysiloxane during curing of the polysiloxane used in the refractive index modulation element.
(3) Depending on the type of heat application means, the heat application means can be provided in the refractive index modulation element by a vapor phase processing method such as vapor deposition.
In the production of refractive index modulation elements using conventional organic resins, when vapor deposition performed under high temperature conditions is selected, there are problems with the heat resistance of organic resins, and depending on the type of resin, vapor deposition may be difficult. Depending on the method, it was done while cooling. When polysiloxane is used, this point is not a serious problem and is advantageous for organic resins.
[0024]
The refractive index modulation element of the present invention is preferably heat-applied at a temperature of 250 ° C. or lower. Regarding the temperature range, preferably, the refractive index can be modulated by applying heat in the range of −70 to 250 ° C. This is because the temperature stability of the polysiloxane is stable and the temperature dependency of the refractive index is in this temperature range.
[0025]
The refractive index modulation element of the present invention can also modulate the refractive index in a range of 0.02 or less, although it varies depending on the type of silicon-based resin that is the refractive index modulation material used. This modulation range is more preferably used within a range of 0.008 or less. The range that can be modulated is greatly affected by the usable temperature range of the polysiloxane. That is, the modulation range when applied at a practical temperature of 250 ° C. or less is the above range.
[0026]
Example 1
(Vinyl group-containing silicon resin)
In a 300 mL round bottom flask, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (14.9 g, 0.08 mol), distilled water (10.1 g, 0.56 mol), hydrochloric acid (3.5 g, 0.096 mol) and ethanol (6.5 g, 0.14 mol) were added and stirred at 50 ° C. Into the dropping funnel, phenyltriethoxysilane (9.6 g, 0.04 mol), methyltrimethoxysilane (38.1 g, 0.28 mol) and ethanol (6.5 g, 0.14 mol) were added and stirred. The solution was added dropwise to the mixed solution in the round bottom flask and refluxed for 2 hours. After refluxing and cooling to room temperature, hexane was added to wash the organic layer until it was neutralized, anhydrous magnesium sulfate was added to remove water, the salt was filtered, and then the organic solvent was removed.
[0027]
(SiH-containing silicon resin)
In a 500 mL round bottom flask, 1,1,3,3-tetramethyldisiloxane (50.4 g, 0.375 mol), distilled water (48 g, 3 mol), hydrochloric acid (24 g, 0.66 mol) and methanol (15 g, 0.47 mol) was added and stirred at 10 ° C. or lower. Tetramethoxysilane (114.2 g, 0.75 mol) was added dropwise to the mixed solution in the flask at 10 ° C. or lower and stirred at room temperature for 2 hours. Hereinafter, neutralization of the solution and removal of the salt and the solvent were performed in the same manner as described above.
[0028]
The vinyl group-containing silicon resin and SiH-containing silicon resin synthesized by the above method were mixed, and the viscosity was measured at room temperature with a B-type rotational viscometer (Tokimec Co., Ltd.), which was 4,500 cps. This was mixed with a platinum catalyst and stirred until uniform, and then the mixture was cured by heating at 80 ° C. for 2 hours. The silicon resin cured product thus obtained was measured for transmittance with a spectrophotometer, U-3210 (Hitachi, Ltd.), and had a transmittance of 85% or more at any wavelength in the range of 350 nm to 1600 nm. Had. When the refractive index with respect to the d-line of 587.6 nm at 20 ° C. was measured with a high-precision refractometer, KPR-200 (Karnu Optical Co., Ltd.), nd was 1.4319. The temperature dependency was −3.2 × 10 −4 / ° C.
[0029]
A silica glass (nd = 1.4586) waveguide was formed on a silicon wafer, and the silicon resin was laminated thereon in a thin film shape. When the silicon wafer was heated to 150 ° C. and the intensity at which the light propagating through the waveguide was emitted from the silicon resin was detected with a spectrophotometer through an optical fiber, the emission intensity was 25% or less compared with that before the heating.
[0030]
(Example 2)
(Vinyl group-containing silicon resin)
A vinyl group-containing silicon resin was synthesized in the same manner as in Example 1 except that phenyltrichlorosilane (16.8 g, 0.7 mol) was used instead of the phenyltriethoxysilane.
[0031]
(SiH-containing crosslinking agent)
According to the same method as that for producing the SiH-containing silicon resin of Example 1, except that phenyltrimethoxysilane (29.74 g, 0.15 mol) and tetramethyldisiloxane (60.45 g, 0.45 mol) were used. A SiH-containing crosslinker was synthesized.
[0032]
The vinyl group-containing silicon resin synthesized by the above method, the Si—H-containing crosslinking agent, and the platinum catalyst were mixed and heat-cured at 120 ° C. for 2 hours. When the optical properties of the cured silicon resin thus obtained were measured in the same manner as in Example 1, it showed a transmittance of 85% or more at any wavelength in the range of 350 nm to 1600 nm, and the nd at 25 ° C. was 1 The temperature dependence of the refractive index was −3.5 × 10 −4 / ° C. A waveguide was formed using BK-7 glass (nd = 1.5163) instead of silica glass, and laminated in the same manner as in Example 1. When heated to about 100 ° C., the emission intensity from the waveguide increased three times compared to before heating.
[0033]
【The invention's effect】
According to the present invention, a thermal modulation type in which the refractive index of a light propagation medium is matched in advance and the refractive index is modulated by heat application, or a different refractive index is modulated by heat applied refractive index to match the refractive index of the light propagation medium. An optical switch, a branch interference optical switch, and a directional coupling optical switch are manufactured, and an element having a wider modulation range than a conventionally known element using a thermoplastic resin is provided. Further, in the case of a refractive index modulation element made of only a single refractive index modulation material, for example, an optical fiber, the refractive index can be changed by changing the temperature of the element, thereby changing the amount of transmitted light.
Claims (2)
（１）３５０nm〜１６００nmの波長範囲において平均の分光透過率が８０％以上でありかつ特定の光吸収帯を有さないこと。
（２）屈折率の温度依存性が−０．００１／℃〜−０．００００５／℃の範囲にあること。At least, have a medium comprising a refractive index modulation material, a refractive index modulation element that in contact with the optical carrier medium, the refractive index in what is thermally modulated, the refractive index modulation material is the following (1) and (2) conditions possess a combination structural units of RSiO 3/2 units and SiO 4/2 units; the combination of R 3 SiO 1/2 units and SiO 4/2 units; R 3 SiO 1/2 units And RSiO 3/2 unit combination; RSiO 3/2 unit alone (wherein R represents an aliphatic or aromatic group having 1 to 18 carbon atoms) Rate modulation element.
(1) The average spectral transmittance is not less than 80% in the wavelength range of 350 nm to 1600 nm and does not have a specific light absorption band.
(2) The temperature dependence of the refractive index is in the range of -0.001 / ° C to -0.00005 / ° C.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26391495A JP3815811B2 (en) | 1995-10-12 | 1995-10-12 | Refractive index modulation element and refractive index modulation method |
| US08/730,721 US5739948A (en) | 1995-10-12 | 1996-10-08 | Refractive index modulation device and method of refractive index modulation |
| EP96307406A EP0768554B1 (en) | 1995-10-12 | 1996-10-11 | Polysiloxane thermo-optic modulator |
| DE69637893T DE69637893D1 (en) | 1995-10-12 | 1996-10-11 | Thermo-optic modulator made of polysiloxane |
| KR1019960045490A KR100480524B1 (en) | 1995-10-12 | 1996-10-12 | Refractive index modulation device and method of manufacturing the same |
| TW085112523A TW343286B (en) | 1995-10-12 | 1996-10-14 | Refractive index modulation device and method of refractive index modulation |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26391495A JP3815811B2 (en) | 1995-10-12 | 1995-10-12 | Refractive index modulation element and refractive index modulation method |
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| Publication Number | Publication Date |
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| JPH09105891A JPH09105891A (en) | 1997-04-22 |
| JP3815811B2 true JP3815811B2 (en) | 2006-08-30 |
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| US6450642B1 (en) * | 1999-01-12 | 2002-09-17 | California Institute Of Technology | Lenses capable of post-fabrication power modification |
| JP2006276654A (en) | 2005-03-30 | 2006-10-12 | Hitachi Ltd | Optical switch and method for using same |
| JP6925100B2 (en) * | 2015-05-21 | 2021-08-25 | 日亜化学工業株式会社 | Light emitting device |
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