JP4762422B2 - Arrayed waveguide grating - Google Patents

Description

【００１７】
ここで、従来の一般的なアレイ導波路型回折格子において、（数１）から前記光透過中心波長の温度依存性を求めてみる。従来の一般的なアレイ導波路型回折格子においては、ｄｎ_ｃ／ｄＴ＝１×１０^−５（℃^−１）、α_ｓ＝３．０×１０^−６（℃^−１）、ｎ_ｃ＝１．４５１（波長１．５５μｍにおける値）であるから、これらの値を（数１）に代入する。
【００１８】
また、波長λは、各光出力導波路６についてそれぞれ異なるが、各波長λの温度依存性は等しい。そして、現在用いられているアレイ導波路型回折格子は、波長１５５０ｎｍを中心とする波長帯の波長多重光を分波したり合波したりするために用いられることが多いので、ここでは、λ＝１５５０ｎｍを（数１）に代入する。そうすると、従来の一般的なアレイ導波路型回折格子の前記光透過中心波長の温度依存性は、（数２）に示す値となる。
【００１９】
【数２】

【００２０】
なお、ｄλ／ｄＴの単位は、ｎｍ／℃である。例えばアレイ導波路型回折格子の使用環境温度が２０℃変化したとすると、各光出力導波路６から出力される光透過中心波長は０．３０ｎｍ長波長側または短波長側にシフトするものであり、前記使用環境温度変化が７０℃以上になると、前記光透過中心波長のシフト量が１ｎｍ以上になってしまう。
【００２１】
アレイ導波路型回折格子は１ｎｍ以下の非常に狭い間隔で波長を分波または合波できることが特徴であり、この特長を生かして波長多重光通信用に適用されるものであるため、上記のように、使用環境温度変化によって光透過中心波長が上記シフト量だけ変化することは致命的である。
【００２２】
そこで、従来から温度により光透過中心波長が変化しないように、アレイ導波路型回折格子の温度を一定に保つための温度調節手段を設けたアレイ導波路型回折格子が提案されている。この温度調節手段は、例えば、ペルチェ素子やヒータなどを設けて構成されるものであり、いずれも、アレイ導波路型回折格子を予め定めた設定温度（室温以上）に保つ制御を行なうものである。
【００２３】
図６に示したアレイ導波路型回折格子においては、符号３０で示すペルチェ素子がアレイ導波路型回折格子の基板１側に設けられており、サーミスタ３１の検出温度に基づいてアレイ導波路型回折格子の温度を一定に保つように調節する。また、ペルチェ素子の代わりにヒータを設けた構成のものは、ヒータで高温保持し、アレイ導波路型回折格子の温度を一定に保つようにしている。
【００２４】
このように、アレイ導波路型回折格子の温度を一定に保つと、温度に起因して基板１の膨張収縮や前記コアの等価屈折率変化などが生じないため、上記光透過中心波長の温度依存性の問題を解消することができる。
【００２５】
また、アレイ導波路型回折格子を構成するアレイ導波路部の作製誤差（膜厚、幅、屈折率等の誤差）に起因して、前記光透過中心波長がＩＴＵグリッド波長等の設定波長からずれている場合にも、光透過中心波長が前記設定波長となる温度を（数２）を用いて算出し、アレイ導波路型回折格子の温度がこの算出温度となるようにペルチェ素子やヒータ等を有する温度調節手段によって温度調節すれば、前記光透過中心波長をグリッド波長に合わせることができる。
【００２６】
しかしながら、ペルチェ素子やヒータのような温度調節手段を用いてアレイ導波路型回折格子の温度を一定に保つものは、温度調節のために、ペルチェ素子やヒータに例えば１Ｗといった通電を常時行なわなければならず、コストがかかるといった問題があった。
【００２７】
また、ペルチェ素子やヒータのような電気部品を使用するためには、当然、コントローラーや制御用サーミスター、熱電対等が必要となり、これらの部品の組立ずれ等に起因して、光透過中心波長シフトを正確に抑制できないことがあった。
【００２８】
さらに、アレイ導波路型回折格子と光ファイバアレイとの接続は、一般に接着剤を用いて行なわれており、ペルチェ素子やヒータによってアレイ導波路型回折格子の温度を室温以上の温度に制御すると、アレイ導波路回折格子と光ファイバーの接続面に介設された接着剤が室温以上の温度によって例えば膨張したり、軟化したりする。したがって、ペルチェ素子などを用いてアレイ導波路型回折格子の温度を一定に保つ構成とした場合に、前記接着剤の膨張や軟化によって、アレイ導波路型回折格子の光入力導波路２や光出力導波路６と光ファイバとの接続損失が増加し、アレイ導波路型回折格子と光ファイバとの接続の信頼性を損ねるといった問題があった。
【００２９】
本発明は、上記課題を解決するためになされたものであり、その目的は、光透過中心波長の温度依存性を正確に抑制することができる安価なアレイ導波路型回折格子を提供することにある。
【００３０】
【課題を解決するための手段】
上記目的を達成するために、本発明は次のような構成をもって課題を解決するための手段としている。すなわち、第１の発明は、１本以上の並設された光入力導波路の出射側に第１のスラブ導波路が接続され、該第１のスラブ導波路の出射側には該第１のスラブ導波路から導出された光を伝搬する互いに異なる長さの複数の並設されたアレイ導波路が接続され、該複数のアレイ導波路の出射側には第２のスラブ導波路が接続され、該第２のスラブ導波路の出射側には複数の並設された光出力導波路が接続された導波路形成領域を基板上に形成し、前記光入力導波路から入力される互いに異なる複数の波長をもった光から１つ以上の波長の光を分波して各光出力導波路から出力する光分波機能を有するアレイ導波路型回折格子であって、前記第１のスラブ導波路と第２のスラブ導波路の少なくとも一方がスラブ導波路の光進行方向の中心軸に対して斜めに交わる切断面で切断されて分離スラブ導波路と成し、前記導波路形成領域が一方側の分離スラブ導波路を含む第１の導波路形成領域と他方側の分離スラブ導波路を含む第２の導波路形成領域とに分離されており、互いに対向する第１の導波路形成領域端面と第２の導波路形成領域端面の間隔を可変する端面間隔可変手段が設けられている構成をもって課題を解決する手段としている。
【００３１】
また、第２の発明は、上記第１の発明の構成に加え、前記端面間隔可変手段は、第１と第２の導波路形成領域の端面間隔可変によってそれぞれの光出力導波路から出力される出力光の光透過中心波長の温度依存変動を低減する温度依存変動低減手段と成している構成をもって課題を解決する手段としている。
【００３２】
さらに、第３の発明は、上記第１又は第２の発明の構成に加え、前記端面間隔可変手段は、互いに対向する第１の導波路形成領域端面と第２の導波路形成領域端面を平行状態と成した構成をもって課題を解決する手段としている。
【００３３】
さらに、第４の発明は、上記第１又は第２の発明の構成に加え、前記端面間隔可変手段は、互いに対向する第１の導波路形成領域端面と第２の導波路形成領域端面を非平行状態と成した構成をもって課題を解決する手段としている。
【００３４】
さらに、第５の発明は、上記第３の発明の構成に加え、前記端面間隔可変手段は第１の導波路形成領域と第２の導波路形成領域に跨る態様で設けられた部材を有しており、該部材は導波路形成領域および基板よりも熱膨張係数が大きい高熱膨張係数部材である構成をもって課題を解決する手段としている。さらに、第６の発明は、上記第３の発明の構成に加え、前記第１の導波路形成領域と第２の導波路形成領域はベース上に配設されており、第１の導波路形成領域と第２の導波路形成領域の一方は前記ベースに固定され、他方は前記ベースに対して移動可能に配設されており、端面間隔可変手段は、一端側が前記ベースに対して移動可能な導波路形成領域に固定され、他端側は前記ベースに固定されて、前記移動可能な導波路形成領域とベースとの間に介設された部材を有しており、該部材は導波路形成領域および基板よりも熱膨張係数が大きい高熱膨張係数部材である構成をもって課題を解決する手段としている。
【００３５】
さらに、第７の発明は、上記第４の構成に加え、前記第１の導波路形成領域と第２の導波路形成領域はベース上に配設されており、第１の導波路形成領域と第２の導波路形成領域の一方は前記ベースに固定され、他方は一端側を前記一方の導波路形成領域に対して傾動の移動が可能に弾性変形可能なヒンジを介して前記ベースに配設されており、端面間隔可変手段は、一端側が前記移動可能な導波路形成領域の前記ヒンジを支点として傾動させる作用点となる位置に接触し、他端側は前記ベースに固定されて、前記移動可能な導波路形成領域とベースとの間に介設された部材を有しており、該部材は導波路形成領域および基板よりも熱膨張係数が大きい高熱膨張係数部材である構成をもって課題を解決する手段としている。
【００３６】
本発明者は、アレイ導波路型回折格子の温度依存性を抑制するために、アレイ導波路型回折格子の線分散特性に着目した。アレイ導波路型回折格子において光入力導波路から入射された光は、第１のスラブ導波路（入力側スラブ導波路）で回折し、アレイ導波路を励振する。なお、前記の如く、隣接するアレイ導波路の長さは互いにΔＬずつ異なっている。そこで、アレイ導波路を伝搬した光は、（数３）を満たし、第２のスラブ導波路（出力側スラブ導波路）の出力端に集光される。
【００３７】
【数３】

【００３８】
（数３）において、ｎ_sは第１のスラブ導波路および第２のスラブ導波路の等価屈折率、ｎ_cはアレイ導波路の等価屈折率、φは回折角、ｍは回折次数、ｄは隣り合うアレイ導波路同士の間隔であり、λは、前記の如く、各光出力導波路から出力される光の透過中心波長である。
【００３９】
ここで、回折角φ=０となるところの光透過中心波長をλ_０とすると、λ_０は（数４）で表される。なお、波長λ_０は、一般に、アレイ導波路型回折格子の中心波長と呼ばれる。
【００４０】
【数４】

【００４１】
ところで、図３において、第１と第２のスラブ導波路３，５の光進行方向中心軸方向をＹ方向とし、Ｙ方向に対して直交する方向をＸ方向とする。回折角φ=０となるアレイ導波路型回折格子の集光位置を点Ｏとすると、回折角φ＝φ_pを有する光の集光位置（第２のスラブ導波路の出力端における位置）は、例えば点Ｐの位置（点ＯからＸ方向にずれた位置）となる。ここで、Ｏ−Ｐ間のＸ方向の距離をｘとすると波長λとの間に（数５）が成立する。
【００４２】
【数５】

【００４３】
（数５）において、Ｌ_fは第２のスラブ導波路の焦点距離であり、ｎ_gはアレイ導波路の群屈折率である。なお、アレイ導波路の群屈折率ｎ_gは、アレイ導波路の等価屈折率ｎ_cにより、（数６）で与えられる。
【００４４】
【数６】

【００４５】
前記（数５）は、第２のスラブ導波路の焦点ＯからＸ方向の距離ｄｘ離れた位置に光出力導波路の入力端を配置形成することにより、ｄλだけ波長の異なった光を取り出すことが可能であることを意味する。
【００４６】
また、（数５）の関係は、第１のスラブ導波路３に関しても同様に成立する。すなわち、例えば第１のスラブ導波路３の焦点中心を点Ｏ’とし、この点Ｏ’からＸ方向に距離ｄｘ’ずれた位置にある点を点Ｐ’とすると、この点Ｐ’に光を入射した場合に、出力の波長がｄλ’ずれることになる。この関係を式により表わすと、（数７）のようになる。
【００４７】
【数７】

【００４８】
なお、（数７）において、Ｌ_ｆ’は第１のスラブ導波路の焦点距離である。この（数７）は、第１のスラブ導波路の焦点Ｏ’とＸ方向の距離ｄｘ’離れた位置に光入力導波路の出力端を配置形成することにより、前記焦点Ｏに形成した光出力導波路においてｄλ’だけ波長の異なった光を取り出すことが可能であることを意味する。
【００４９】
したがって、アレイ導波路型回折格子の使用環境温度変動によってアレイ導波路型回折格子の光出力導波路から出力される光透過中心波長がΔλずれたときに、ｄλ’＝Δλとなるように、光入力導波路の出力端位置を、前記Ｘ方向（すなわち、スラブ導波路の光進行方向中心軸に対する直交方向）に距離ｄｘ’だけずらせば、例えば焦点Oに形成した光出力導波路において、波長ずれのない光を取り出すことができ、他の光出力導波路に関しても同様の作用が生じるため、前記光透過中心波長ずれΔλを補正（解消）できることになる。
【００５０】
上記構成の本発明においては、第１のスラブ導波路と第２のスラブ導波路の少なくとも一方が、スラブ導波路の光進行方向の中心軸に対して斜めに交わる切断面で切断分離されている。
【００５１】
そこで、第１のスラブ導波路が切断分離されていると仮定して議論すると、端面間隔可変手段によって、前記切断分離された一方側の分離スラブ導波路を含む第１の導波路形成領域の端面と他方側の分離スラブ導波路を含む第２の導波路形成領域の端面の間隔を可変することにより、例えば光入力導波路の出力端位置が、第１のスラブ導波路の光進行方向の中心軸と直交する方向にシフトする。そうすると、上記原理によって、それぞれの光出力導波路から出力する出力光の光透過中心波長をシフトさせることが可能となる。
【００５２】
また、前記端面間隔可変手段によって、前記各光透過中心波長の温度依存変動（波長ずれ）Δλがｄλと等しくなるようにして、前記各光透過中心波長の温度依存変動を低減するように前記端面間隔を可変して光入力導波路の出力端位置を移動させれば、前記光透過中心波長ずれを解消することが可能となる。
【００５３】
なお、厳密に言えば、第１と第２の導波路形成領域の端面間隔を変えることによって、光入力導波路の出力端からアレイ導波路の入力端まで、第１のスラブ導波路内を伝搬する光の焦点距離Ｌ_ｆ’が若干変化するが、現在用いられているアレイ導波路型回折格子における第１のスラブ導波路の焦点距離は数ｍｍのオーダーであり、一方、アレイ導波路型回折格子の光透過中心波長補正のために移動す上記端面間隔可変量は数μｍ〜数１０μｍのオーダーであり、第１のスラブ導波路の焦点距離に比べて非常に小さい。
【００５４】
そのため、実質的には上記焦点距離の変化は無視してしまっても何も差し支えない。このことから、前記の如く、アレイ導波路型回折格子における各光透過中心波長の温度依存変動を低減するように、第１の導波路形成領域の端面と第２の導波路形成領域の端面の間隔を調整すれば、前記光透過中心波長ずれを解消することが可能となる。
【００５５】
ここで、温度変化量と光入力導波路の位置補正量の関係を導いておく。前記光透過中心波長の温度依存性（温度による光透過中心波長のずれ量）は、前記（数２）で表されるので、温度変化量Ｔを用いて光透過中心波長ずれ量Δλを（数８）により表わすことができる。
【００５６】
【数８】

【００５７】
（数７）、（数８）から、温度変化量Ｔと光入力導波路の位置補正量ｄｘ’を求めると、（数９）が導かれる。
【００５８】
【数９】

【００５９】
したがって、本発明において、（数９）により示される位置補正量ｄｘ’だけ、光入力導波路の出力端位置を、第１のスラブ導波路の光進行方向の中心軸に直交する方向に移動できるように、前記端面間隔可変手段によって第１の導波路形成領域端面と第２の導波路形成領域端面の間隔を可変調整することにより、前記光透過中心波長ずれを解消することが可能となる。
【００６０】
また、前記の如く、アレイ導波路型回折格子は光の相反性を利用して形成されているものであり、第２のスラブ導波路側を切断分離して、この切断分離に対応させて導波路形成領域を切断分離し、第１の導波路形成領域と第２の導波路形成領域とを形成した場合も、端面間隔可変手段による作用によって上記と同様の効果が得られ、前記各光透過中心波長の温度依存変動を解消することが可能となる。
【００６１】
さらに、本発明においては、上記の原理に基づきペルチェ素子やヒータを用いなくてもアレイ導波路型回折格子の使用環境温度による光透過中心波長ずれを抑制し、光透過中心波長の温度無依存化を行うことができるために、ペルチェ素子やヒータを含む温度調節手段を設ける場合のように、常時通電を必要とせず、部品の組立誤差による温度補正誤差が生じることもなく、室温以上の温度でアレイ導波路型回折格子を保つことによるアレイ導波路型回折格子と光ファイバとの接続損失増加の虞もない。
【００６２】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。なお、本実施形態例の説明において、従来例と同一名称部分には同一符号を付し、その重複説明は省略する。図１には、本発明に係るアレイ導波路型回折格子の第１実施形態例の概略図が平面図によって模式的に示されている。なお、同図の（ａ）には本実施形態例のアレイ導波路型回折格子の平面図が、同図の（ｂ）にはその側面図がそれぞれ示されている。
【００６３】
同図に示すように、本実施形態例のアレイ導波路型回折格子も従来例のアレイ導波路型回折格子と同様に、基板１上にコアの導波路構成を形成しており、図１では、基板１上の導波路構成の形成領域を導波路形成領域１０（１０ａ、１０ｂ）として示している。
【００６４】
本実施形態例のアレイ導波路型回折格子は、従来例と同様に、１本の光入力導波路２、第１のスラブ導波路３、複数のアレイ導波路４、第２のスラブ導波路５、複数の光出力導波路６を有しており、前記アレイ導波路４、光出力導波路６は、それぞれ予め定められた導波路間隔を介して並設されているが、本実施形態例のアレイ導波路型回折格子においては、第１のスラブ導波路３が、第１のスラブ導波路３の光進行方向の中心軸（図のＹ方向）に対して斜めに交わる切断面８で切断分離されている。
【００６５】
また、本実施形態例では、上記第１のスラブ導波路３の切断面８での切断に伴い、基板１および導波路形成領域（導波路形成領域）１０もそれぞれ２つに切断分離されている。分離スラブ導波路３ａを含む第１の導波路形成領域１０ａと、分離スラブ導波路３ｂ含む第１の導波路形成領域１０ｂに跨る態様で、導波路形成領域１０よりも熱膨張係数が大きく、基板１よりも熱膨張係数が大きい高熱膨張係数部材７が設けられており、高熱膨張係数部材７は導波路形成領域１０ａ，１０ｂの下側の基板１ａ，１ｂ側に接着剤１３によって固定されている。
【００６６】
本実施形態例では、高熱膨張係数部材７が、第１の導波路形成領域１０ａの端面８ａと第２の導波路形成領域１０ｂの端面８ｂとの間隔を可変する端面間隔可変手段として機能する。また、この端面間隔可変手段は、互いに対向する第１の導波路形成領域１０ａの端面８ａと第２の導波路形成領域１０ｂの端面８ｂを平行状態として端面８ａと端面８ｂの間隔を可変する構成と成している。
【００６７】
図１において、第１のスラブ導波路３の光進行方向中心軸方向をＹ方向とし、このＹ方向に直交する方向をＸ方向としたとき、端面間隔可変手段は、端面８ａと端面８ｂの間隔を可変することによって光入力導波路２の出力端２０のＸ方向の位置を変化させ、この変化によってアレイ導波路型回折格子の光透過中心波長のシフトを解消する機能を有している。
【００６８】
高熱膨張係数部材７は、この機能を果たすことができる端面８ａと８ｂの間隔に対応して熱膨張係数による収縮が生じるように、例えば熱膨張係数が２．５×１０^−５（１／Ｋ）のＡｌ（アルミニウム）により形成されている。
【００６９】
そして、このように、高熱膨張係数部材７を形成することにより、本実施形態例では、端面間隔可変手段が、第１と第２の導波路形成領域１０ａ，１０ｂの端面８ａ，８ｂの間隔可変によって、それぞれの光出力導波路６から出力される出力光の光透過中心波長の温度依存変動を低減する温度依存変動低減手段と成している。
【００７０】
なお、本実施形態例において、前記導波路構成における各パラメータは、以下のように構成されている。すなわち、第１のスラブ導波路３の焦点距離Ｌ_ｆ’と第２のスラブ導波路５の焦点距離Ｌ_fは等しく、その値は９ｍｍであり、また、２５℃において、第１のスラブ導波路３の等価屈折率および第２のスラブ導波路５の等価屈折率は共にｎ_ｓで、その値は、波長１．５５μｍの光に対して１．４５３である。また、波長１．５５μｍの光に対してアレイ導波路４の等価屈折率ｎ_ｃは１．４５１、アレイ導波路の群屈折率ｎ_ｇは１．４７５、アレイ導波路４の光路長差ΔＬは６５．２μｍ、隣り合うアレイ導波路４同士の間隔は１５μｍ、回折次数ｍは６１である。
【００７１】
したがって、本実施形態例のアレイ導波路型回折格子において、回折角φ＝０となるところの光透過中心波長λ₀は、前記（数４）から明らかなように、λ₀=１５５０．９ｎｍである。
【００７２】
ところで、本発明者は、アレイ導波路型回折格子の温度依存性を抑制するために、アレイ導波路型回折格子の線分散特性に着目し、前記（数１）〜（数９）を用いた説明の通り、アレイ導波路型回折格子の使用環境温度変化量Ｔと光入力導波路の位置補正量ｄｘ’との関係を求めた。そして、この関係は前記（数９）により表わされることを確認した。
【００７３】
そこで、本実施形態例について、アレイ導波路型回折格子の導波路構成の各パラメータと（数９）に基づき、アレイ導波路型回折格子の使用環境温度の変化量Ｔと光入力導波路２の位置補正量ｄｘ’の関係を求めると、（数１０）に示す関係となっていることが分かった。
【００７４】
【数１０】

【００７５】
したがって、本実施形態例においては、アレイ導波路型回折格子の使用環境温度が１０℃変化した際、光入力導波路２の出力端の位置をＸ方向（第１のスラブ導波路３の光進行方向の中心軸に対して直交する方向）に約３．８３μｍ補正（移動）すれば、温度による中心波長すれが補正できる計算になる。
【００７６】
そこで、本実施形態例では、アレイ導波路型回折格子の使用環境温度が１０℃上昇したときに、第１の導波路形成領域１０ａが第２の導波路形成領域１０ｂに対して図の矢印Ａ方向に移動して端面８ａと端面８ｂの間隔が広がり、それにより、光入力導波路２の出力端２０の位置が約３．８３μｍだけＡ’方向に移動するようにした。
【００７７】
また、その逆に、本実施形態例において、アレイ導波路型回折格子の使用環境温度が１０℃下降したときに、第１の導波路形成領域１０ａが第２の導波路形成領域１０ｂに対して図の矢印Ｂ方向に移動して端面８ａと端面８ｂの間隔が狭まり、それにより、光入力導波路２の出力端２０の位置が約３．８３μｍだけＢ’方向に移動するように、端面８ａと端面８ｂの間隔可変量を定めた。
【００７８】
そして、この間隔可変量が得られるように高熱膨張係数部材７の大きさ等を形成し、この高熱膨張係数部材７の熱伸縮によって、各光透過中心波長の温度依存変動を低減する方向に、第１の導波路形成領域１０ａと第２の導波路形成領域１０ｂを相対移動させるようにしている。
【００７９】
なお、本実施形態例のアレイ導波路型回折格子の作製に際し、本発明者は、ファイバグレーティングの温度補償パッケージを応用し、モジュールを組み立てた。すなわち、第１のスラブ導波路３の切断にはダイシングソーを用い、切断面８における反射を防ぐために、石英系ガラスと屈折率の整合したマッチンググリースを切断面８に塗布した。また、高熱膨張係数部材７と導波路形成領域１０ａとの接着に用いた接着剤１３は、熱硬化接着剤とし、１００℃で硬化させた。
【００８０】
本実施形態例は以上のように構成されており、第１のスラブ導波路３の光進行方向の中心軸に対して斜めに交わる切断面８で、第１のスラブ導波路３が分離スラブ導波路３ａ，３ｂに切断分離されており、アレイ導波路型回折格子の使用環境温度が変化すると、端面間隔可変手段としての高熱膨張係数部材７によって、第１の導波路形成領域１０ａの端面８ａと第２の導波路形成領域１０ｂの端面８ｂの間隔が可変される。
【００８１】
そして、光入力導波路２の出力端２０の位置が、アレイ導波路型回折格子のそれぞれの光出力導波路６から出力される光透過中心波長の温度依存変動を低減する方向（図１の矢印Ａ’方向または矢印Ｂ’方向）に移動させられる。
【００８２】
また、上記光入力導波路２の出力端２０のＸ方向移動量は、前記（数１０）により求められる位置補正量ｄｘ’であり、端面間隔可変手段は、第１と第２の導波路形成領域１０ａ，１０ｂの端面８ａ，８ｂ間隔可変によって、それぞれの光出力導波路６から出力される出力光の光透過中心波長の温度依存変動を補償する構成と成しているために、本実施形態例は、たとえアレイ導波路型回折格子の使用環境温度が変化しても、この温度変化に伴う光透過中心波長ずれを解消することができ、使用環境温度に依存しない、いわゆる温度無依存型のアレイ導波路型回折格子とすることができる。
【００８３】
本発明者が、実際に、０℃〜８０℃の環境温度において、光透過中心波長の温度変化を測定したところ、図２の特性線ａに示す結果が得られ、光透過中心波長のずれ（シフト）量は約０．０１ｎｍ以下となり、使用環境温度が０℃〜８０℃の範囲内で変化しても、光透過中心波長は殆どずれないことが確認できた。
【００８４】
なお、図２には、アレイ導波路型回折格子における導波路構成の各パラメータを本実施形態例と同様に形成し、第１のスラブ導波路３を分離していない従来のアレイ導波路型回折格子において、０℃〜８０℃の環境温度における光透過中心波長の温度変化を測定した結果も示されている（図２の特性線ｂ）。特性線ａと特性線ｂとを比較すると明らかなように、本実施形態例のアレイ導波路型回折格子は、従来のアレイ導波路型回折格子において問題であった光透過中心波長の温度依存性を解消することができ、光波長多重通信用などの実用に適した優れたアレイ導波路型回折格子であることが分かる。
【００８５】
また、本実施形態例によれば、端面間隔可変手段は、高熱膨張係数部材７を第１の導波路形成領域１０ａと第２の導波路形成領域１０ｂとに跨って設けることによって構成されているために、装置構成を非常に簡略化することができ、装置の低コスト化および製造歩留まりの向上を図ることができる。
【００８６】
さらに、本実施形態例において、端面間隔可変手段として適用している高熱膨張係数部材７は、安価なＡｌにより形成しているので、より一層、装置の低コスト化を図ることができる。
【００８７】
さらに、本実施形態例によれば、ペルチェ素子やヒータを用いる必要がないために、ペルチェ素子やヒータを含む温度調節手段を設ける場合のように、常時通電を必要とせず、部品の組立誤差による温度補正誤差が生じることもなく、室温以上の温度でアレイ導波路型回折格子を保つことによるアレイ導波路型回折格子と光ファイバとの接続損失増加の虞もない。
【００８８】
したがって、本実施形態例のアレイ導波路型回折格子は、確実に、光透過中心波長の温度依存性を解消でき、しかも、接続相手側の光ファイバとの接続信頼性が高く、コストが安い優れたアレイ導波路型回折格子とすることができる。
【００８９】
さらに、本実施形態例によれば、第１のスラブ導波路３を切断面８で切断しているために、例えばアレイ導波路型回折格子を構成するアレイ導波路部の作製誤差に起因して、前記光透過中心波長がＩＴＵグリッド波長等の設定波長からずれている場合には、その分だけ第１と第２の導波路形成領域１０ａ，１０ｂの端面間隔をずらして、光入力導波路２のＸ方向の位置をずらすことにより、設定温度において、前記光透過中心波長をグリッド波長等の設定波長とすることができる。
【００９０】
図４には、本発明に係るアレイ導波路型回折格子の第２実施形態例の概略図が平面図によって模式的に示されている。なお、同図の（ａ）には本実施形態例のアレイ導波路型回折格子の平面図が、同図の（ｂ）にはそのＣ−Ｃ’断面図がそれぞれ示されている。
【００９１】
本第２実施形態例は上記第１実施形態例とほぼ同様に構成されており、本第２実施形態例が上記第１実施形態例と異なる特徴的なことは、アレイ導波路型回折格子を配設するベース９と第１の導波路形成領域１０ａの側面との間に高熱膨張係数部材７を介設して、前記端面間隔可変手段を構成したことである。
【００９２】
具体的には、ベース９を石英ガラスやＩｎｖａｒロットなどの低熱膨張率の材料により形成し、高熱膨張係数部材７は熱膨張係数が１．６５×１０^−５（１／Ｋ）のＣｕ（銅）により形成している。高熱膨張係数部材７は第１の導波路形成領域１０ａの上面に接続されることなく、第２の導波路形成領域１０ｂの上面に沿って設けられた上板部７ａと第１の導波路形成領域１０ａの側面に沿って設けられた側板部７ｂとを有する部材であり、高熱膨張係数部材７の側板部７ｂをねじ１１でベース９に固定している。
【００９３】
また、第１の導波路形成領域１０ａおよびその下の基板１ａはベース９に固定しており、一方、第２の導波路形成領域１０ｂおよびその下の基板１ｂは、ベース９の表面に沿って図の矢印Ａ方向および矢印Ｂ方向にスライド移動自在に配置している。そして、第２の導波路形成領域１０ｂの上面を接着剤１３によって高熱膨張係数部材７の上板部７ａに固定している。
【００９４】
本第２実施形態例は以上のように構成されており、本第２実施形態例は高熱膨張係数部材７の熱収縮に応じて第２の導波路形成領域１０ｂを第１の導波路形成領域１０ａに対して相対移動させることにより、上記第１実施形態例と同様に、高熱膨張係数部材７の熱伸縮に応じて第２の導波路形成領域１０ｂの端面８ｂと第１の導波路形成領域１０ａの端面８ａとの間隔が可変され、上記第１実施形態例とほぼ同様の作用により、同様の効果を奏することができる。
【００９５】
また、本第２実施形態例でも、端面間隔可変手段は、高熱膨張係数部材７、ベース９を有する簡単な構成であり、アレイ導波路型回折格子の構成の複雑化を避けることができ、容易に作製できる。
【００９６】
さらに、本第２実施形態例では、Ａｌほど線（熱）膨張係数が大きくないＣｕ等を用いることができ、高熱膨張係数部材７の材料を特別限定する必要はないメリットがある。それというのは、上記第１実施形態例では、高熱膨張係数部材７の配設形態を考慮すると、高熱膨張係数部材７の熱膨張を大きくする必要があり、Ａｌ等によって形成する必要があるが、第２実施形態例では例えばチップサイズ（導波路形成領域１０ａ、１０ｂのサイズ）が小さくて高熱膨張係数部材７がチップサイズ内に収まらない場合でも適用できるため、高熱膨張係数部材７としてＡｌほど線膨張係数が大きくない材料を用いることができる。
【００９７】
図５には、本発明に係るアレイ導波路型回折格子の第３実施形態例の概略図が平面図により示されている。本第３実施形態例は上記第２実施形態例とほぼ同様に構成されており、本第３実施形態例が上記第２実施形態例と異なる特徴的なことは、端面間隔可変手段が、互いに対向する第１の導波路形成領域１０ａの端面８ａと第２の導波路形成領域１０ｂの端面８ｂを非平行状態として、端面８ａと端面８ｂの間隔を可変する構成としたことである。
【００９８】
具体的には、本第３実施形態例においては、第１の導波路形成領域１０ａの一端側に、弾性変形可能なプラスチックフィルムによって形成されたヒンジ１５を接着剤１３により固定し、第１の導波路形成領域１０ａの他端側には切り欠き１２を形成している。そして、高熱膨張係数部材７の基端側をベース９に固定し、高熱膨張係数部材７の先端側を切り欠き１２に接触させて設け、高熱膨張係数部材７の熱伸縮に応じて、第１の導波路形成領域１０ａを、図のＳを支点として傾動させるようにしている。
【００９９】
本第３実施形態例では、このような構成により、互いに対向する第１の導波路形成領域１０ａの端面８ａと第２の導波路形成領域１０ｂの端面８ｂとが斜めに交わる非平行状態として、端面８ａと端面８ｂの間隔を可変する（言い換えれば端面８ａと端面８ｂとの成す角度を可変する）構成としており、本第３実施形態例も上記第１、第２実施形態例と同様の作用により同様の効果を奏することができる。
【０１００】
なお、本発明は上記実施形態例に限定されることはなく、様々な実施の態様を採り得る。例えば、上記各実施形態例では、高熱膨張係数部材７としてＡｌやＣｕの板を用いたが、高熱膨張係数部材７は必ずしもＡｌやＣｕとするとは限らず、ＡｌやＣｕ以外の、導波路形成領域よりも熱膨張係数が大きい材料により形成してもよい。
【０１０１】
また、上記各実施形態例では、第１のスラブ導波路３を切断分離したが、アレイ導波路型回折格子は光の相反性を利用して形成されているものであり、第２のスラブ導波路５側を切断分離して、互いに対向する第１の導波路形成領域端面と第２の導波路形成領域端面の間隔を可変し、それぞれの光出力導波路から出力される出力光の光透過中心波長の温度依存変動を低減するようにしてもよく、この場合も、上記各実施形態例と同様の効果が得られ、前記光透過中心波長の温度依存変動を解消することができる。
【０１０２】
さらに、上記各実施形態例では、第１のスラブ導波路３を切断分離することにより形成した第１の導波路形成領域１０ａの端面８ａと第２の導波路形成領域１０ｂの端面８ｂの間隔を可変する端面間隔可変手段を、高熱膨張係数部材７を設けて形成したが、端面間隔可変手段の構成は特に限定されるものではなく、適宜設定されるものである。すなわち、上記端面間隔可変手段は、上記第１の導波路形成領域１０ａの端面８ａと第２の導波路形成領域１０ｂの端面８ｂの間隔を可変することにより、アレイ導波路型回折格子の光透過中心波長をシフトできる機能を有していればよい。
【０１０３】
特に、上記端面間隔可変手段は、上記各実施形態例のように、アレイ導波路型回折格子の各光透過中心波長の温度依存変動を低減する方向に、第１と第２の導波路形成領域の端面間隔を可変する機能を有していれば望ましく、端面間隔可変手段をこのように構成することにより、上記各実施形態例のように、従来のアレイ導波路型回折格子において問題であった光透過中心波長の温度依存性を解消することができ、光波長多重通信用などの実用に適した優れたアレイ導波路型回折格子とすることができる。
【０１０４】
さらに、本発明のアレイ導波路型回折格子を構成する各導波路２，３，４，５，６の等価屈折率や本数、大きさなどの詳細な値は特に限定されるものではなく、適宜設定されるものである。
【０１０５】
【発明の効果】
第１の発明によれば、第１のスラブ導波路と第２のスラブ導波路の少なくとも一方を、スラブ導波路の光進行方向の中心軸に対して斜めに交わる切断面で切断分離し、この切断分離により形成される第１の導波路形成領域端面と第２の導波路形成領域端面の間隔を可変するものであるから、この端面間隔可変により、例えば光入力導波路の出力端位置や光出力導波路の入力端位置を上記中心軸に直交する方向にずらしてアレイ導波路型回折格子の各光透過中心波長をシフトさせることができる。
【０１０６】
また、第２の発明によれば、上記第１の発明に加えて、前記端面間隔可変手段を、第１と第２の導波路形成領域の端面間隔可変によってそれぞれの光出力導波路から出力される出力光の光透過中心波長の温度依存変動を低減する温度依存変動低減手段と成すものであるから、前記端面間隔可変量を適切な値とすることによって前記各光透過中心波長の温度依存変動（波長ずれ）を解消することができる。
【０１０７】
さらに、第２の発明によれば、ペルチェ素子やヒータを用いなくてもアレイ導波路型回折格子の使用環境温度による光透過中心波長ずれを抑制し、光透過中心波長の温度無依存化を行うことができるために、ペルチェ素子やヒータを含む温度調節手段を設ける場合のように、常時通電を必要とすることもないし、部品の組立誤差による温度補正誤差が生じることもなく、さらに、室温以上の温度でアレイ導波路型回折格子を保つことによるアレイ導波路型回折格子と光ファイバとの接続損失増加の虞もない。
【０１０８】
したがって、第２の発明のアレイ導波路型回折格子は、接続相手側の光ファイバとの接続信頼性が高く、確実に光透過中心波長の温度依存性を解消でき、コストが安い優れたアレイ導波路型回折格子とすることができる。
【０１０９】
さらに、第３、第４、第５の発明によれば、導波路形成領域よりも熱膨張係数が大きい高熱膨張係数部材を、第１の導波路形成領域と第２の導波路形成領域に跨る態様で設けたり、アレイ導波路型回折格子を配設するベースと第１の導波路形成領域と第２の導波路形成領域の移動側の導波路形成領域間に介設したりして端面間隔可変手段を形成したものであるから、高熱膨張係数部材を用いた簡単な構成により、前記端面間隔可変手段を形成することができる。
【０１１０】
したがって、第３、第４、第５の発明によれば、上記優れた効果を奏するアレイ導波路型回折格子を、簡単な構成で容易に作製することができ、コストを低コストにできる。
【０１１１】
さらに、第６、第７の発明のように、互いに対向する第１の導波路形成領域端面と第２の導波路形成領域端面とを平行状態としたり、非平行状態としたりして、上記効果を奏することができるアレイ導波路型回折格子を様々に形成し、アレイ導波路型回折格子の仕様等に対応する好適なアレイ導波路型回折格子を形成することができる。
【図面の簡単な説明】
【図１】本発明に係るアレイ導波路型回折格子の第１実施形態例を平面図（ａ）と側面図（ｂ）により示す要部構成図である。
【図２】上記実施形態例のアレイ導波路型回折格子における光透過中心波長の温度依存性を従来のアレイ導波路型回折格子における光透過中心波長の温度依存性と比較して示すグラフである。
【図３】アレイ導波路型回折格子における光透過中心波長シフトと光入力導波路および光出力導波路の位置との関係を示す説明図である。
【図４】本発明に係るアレイ導波路型回折格子の第２実施形態例を平面図（ａ）と断面図（ｂ）により示す要部構成図である。
【図５】本発明に係るアレイ導波路型回折格子の第３実施形態例を平面図により示す要部構成図である。
【図６】ペルチェ素子を設けて構成した従来のアレイ導波路型回折格子を示す説明図である。
【図７】アレイ導波路型回折格子の１つの光出力導波路から出力される光の光透過特性を示すグラフである。
【符号の説明】
１ 基板
２ 光入力導波路
３ 第１のスラブ導波路
３ａ，３ｂ 分離スラブ導波路
４ アレイ導波路
５ 第２のスラブ導波路
６ 光出力導波路
７ 高熱膨張係数部材
８ 切断面
８ａ，８ｂ 端面
９ ベース
１０，１０ａ，１０ｂ 導波路形成領域
１４ 係止部材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an arrayed waveguide grating used as, for example, an optical multiplexer / demultiplexer in wavelength multiplexing optical communication.
[0002]
[Prior art]
In recent years, in optical communication, research and development of optical wavelength division multiplexing communication has been actively conducted as a method for dramatically increasing the transmission capacity, and practical application is being advanced. In optical wavelength division multiplexing, for example, a plurality of lights having different wavelengths are multiplexed and transmitted. In such an optical wavelength division multiplexing system, from the multiplexed light to be transmitted, on the optical receiving side, for each wavelength. In order to extract the light, it is indispensable to provide in the system a light transmission device that transmits only light of a predetermined wavelength.
[0003]
As an example of the light transmission device, there is an arrayed waveguide grating (AWG) of a planar optical waveguide circuit (PLC) as shown in FIG. The arrayed waveguide type diffraction grating has a waveguide configuration as shown in the figure formed on a substrate 1 made of silicon or the like with a core made of quartz glass or the like.
[0004]
The waveguide configuration of the arrayed waveguide grating is such that the first slab waveguide 3 is connected to the output side of one or more optical input waveguides 2 arranged in parallel, and the first slab waveguide 3 is output. A plurality of arrayed waveguides 4 arranged in parallel are connected to the side, a second slab waveguide 5 is connected to the output side of the arrayed waveguide 4, and a plurality of arrayed waveguides 4 are connected to the output side of the second slab waveguide 5. The optical output waveguides 6 arranged side by side are connected to each other.
[0005]
The arrayed waveguide 4 propagates light derived from the first slab waveguide 3, and is formed to have different lengths. The lengths of the adjacent arrayed waveguides 4 are different from each other by ΔL. The optical input waveguide 2 and the optical output waveguide 6 are provided corresponding to the number of signal lights having different wavelengths that are demultiplexed or combined by, for example, an arrayed waveguide type diffraction grating. The waveguide 4 is usually provided in a large number such as 100, for example, but in the figure, for the sake of simplification of the drawing, each of the optical input waveguide 2, the arrayed waveguide 4, and the optical output waveguide 6 is provided. Is simply shown.
[0006]
For example, a transmission side optical fiber (not shown) is connected to the optical input waveguide 2 so that wavelength division multiplexed light is introduced, and the first slab guide is passed through the optical input waveguide 2. The light introduced into the waveguide 3 spreads by the diffraction effect and enters each arrayed waveguide 4 and propagates through the arrayed waveguide 4.
[0007]
The light propagating through the arrayed waveguide 4 reaches the second slab waveguide 5 and is further collected and output to the optical output waveguide 6, but all the arrayed waveguides 4 have different lengths. Therefore, after propagating through the arrayed waveguide 4, the phase of each light is shifted, and the wavefront of the focused light is tilted according to the shift amount, and the focusing position is determined by the tilt angle.
[0008]
For this reason, the light condensing positions of the light having different wavelengths are different from each other. By forming the light output waveguide 6 at that position, the light having different wavelengths (demultiplexed light) is guided to the light output different for each wavelength. It can be output from the waveguide 6.
[0009]
In other words, the arrayed waveguide type diffraction grating demultiplexes light of one or more wavelengths from the multiplexed light having a plurality of different wavelengths inputted from the optical input waveguide 2 and outputs them from each optical output waveguide 6. The center wavelength of the light to be demultiplexed is the difference in length (ΔL) of the arrayed waveguide 4 and the effective refractive index n of the arrayed waveguide 4._cIs proportional to
[0010]
Since the arrayed waveguide type diffraction grating has the characteristics as described above, the arrayed waveguide type diffraction grating can be used as an optical wavelength demultiplexer for wavelength multiplexing transmission. For example, as shown in FIG. When wavelength multiplexed light having wavelengths λ1, λ2, λ3,..., Λn (n is an integer of 2 or more) is input from the two optical input waveguides 2, the light of each wavelength is the first slab waveguide. 3, reaches the arrayed waveguide 4, passes through the second slab waveguide 5, is condensed at different positions depending on the wavelength as described above, and is incident on different optical output waveguides 6. The light is output from the output end of the light output waveguide 6 through the light output waveguide 6.
[0011]
Then, by connecting an optical fiber for light output (not shown) to the output end of each light output waveguide 6, light of each wavelength is extracted through this optical fiber. When connecting an optical fiber to each optical output waveguide 6 or the above-described optical input waveguide 2, for example, an optical fiber array having optical fiber end faces arranged and fixed in a one-dimensional array is prepared. The optical fiber, the optical output waveguide 6 and the optical input waveguide 2 are connected by being fixed to the connection end face side of the output waveguide 6 and the optical input waveguide 2.
[0012]
In the arrayed waveguide type diffraction grating, the light transmission characteristics of the light output from each light output waveguide 6 (wavelength characteristics of the transmitted light intensity of the arrayed waveguide type diffraction grating) are as shown in FIG. Each light transmission center wavelength (for example, λ1, λ2, λ3,... Λn) is the center, and the light transmission characteristic is such that the light transmittance decreases as the wavelength deviates from the corresponding light transmission center wavelength. The light transmission characteristic does not necessarily have one maximum value, and may have two or more maximum values.
[0013]
Further, since the arrayed waveguide type diffraction grating uses the principle of reciprocity (reversibility) of light, it has a function as an optical demultiplexer as well as a function as an optical multiplexer. That is, conversely to FIG. 6, when light of a plurality of different wavelengths is incident from the respective light output waveguides 6 for each wavelength, these lights pass through the propagation path opposite to the above and are guided by the array. The signals are multiplexed by the waveguide 4 and emitted from one optical input waveguide 2.
[0014]
In such an arrayed waveguide type diffraction grating, ΔL is designed to be large because the wavelength resolution of the diffraction grating is proportional to the difference in length (ΔL) of the arrayed waveguide 4 constituting the diffraction grating, as described above. As a result, optical multiplexing / demultiplexing of wavelength-division multiplexed light with a narrow wavelength interval that could not be realized with conventional diffraction gratings becomes possible, and optical multiplexing / demultiplexing of a plurality of signal lights required for realizing high-density optical wavelength division multiplexing communication is possible. A wave function, that is, a function of demultiplexing or multiplexing a plurality of optical signals having a wavelength interval of 1 nm or less can be achieved.
[0015]
[Problems to be solved by the invention]
By the way, since the above-mentioned arrayed waveguide type diffraction grating is mainly made of a silica-based glass material, the light transmission center of the arrayed waveguide type diffraction grating is caused by the temperature dependence of the silica-based glass material. The wavelength shifts depending on the temperature. This temperature dependency is such that the transmission center wavelength of light output from one optical output waveguide 6 is λ, and the equivalent refractive index of the core forming the arrayed waveguide 4 is n._cThe coefficient of thermal expansion of the substrate (for example, silicon substrate) 1 is α_sWhen the temperature change amount of the arrayed waveguide type diffraction grating is T, it is represented by (Equation 1).
[0016]
[Expression 1]

[0017]
Here, in the conventional general arrayed waveguide grating, the temperature dependence of the light transmission center wavelength is obtained from (Equation 1). In a conventional general arrayed waveguide grating, dn_c/ DT = 1 × 10^-5(℃^-1), Α_s= 3.0 × 10^-6(℃^-1), N_cSince 1.451 (value at a wavelength of 1.55 μm), these values are substituted into (Equation 1).
[0018]
Further, the wavelength λ is different for each optical output waveguide 6, but the temperature dependence of each wavelength λ is equal. The arrayed waveguide grating currently used is often used for demultiplexing or multiplexing wavelength-multiplexed light in a wavelength band centered on a wavelength of 1550 nm. = 1550 nm is substituted into (Equation 1). Then, the temperature dependence of the light transmission center wavelength of the conventional general arrayed waveguide grating is a value shown in (Expression 2).
[0019]
[Expression 2]

[0020]
The unit of dλ / dT is nm / ° C. For example, if the operating environment temperature of the arrayed waveguide grating changes by 20 ° C., the light transmission center wavelength output from each light output waveguide 6 is shifted to the 0.30 nm long wavelength side or short wavelength side. When the temperature change in the use environment is 70 ° C. or more, the shift amount of the light transmission center wavelength becomes 1 nm or more.
[0021]
The arrayed waveguide type diffraction grating is characterized in that the wavelength can be demultiplexed or multiplexed at a very narrow interval of 1 nm or less, and is used for wavelength multiplexing optical communication by taking advantage of this feature. In addition, it is fatal that the light transmission center wavelength is changed by the shift amount due to a change in the use environment temperature.
[0022]
Therefore, an arrayed waveguide type diffraction grating provided with a temperature adjusting means for keeping the temperature of the arrayed waveguide type diffraction grating constant so that the light transmission center wavelength does not change with temperature has been proposed. This temperature adjusting means is configured by providing, for example, a Peltier element, a heater, etc., all of which controls to keep the arrayed waveguide grating at a preset temperature (above room temperature). .
[0023]
In the arrayed waveguide type diffraction grating shown in FIG. 6, a Peltier element indicated by reference numeral 30 is provided on the substrate 1 side of the arrayed waveguide type diffraction grating, and the arrayed waveguide type diffraction is performed based on the detection temperature of the thermistor 31. Adjust the grid temperature to keep it constant. In the case of a configuration in which a heater is provided instead of the Peltier element, the temperature of the arrayed waveguide type diffraction grating is kept constant by holding the heater at a high temperature.
[0024]
As described above, if the temperature of the arrayed waveguide grating is kept constant, the substrate 1 does not expand or contract or the equivalent refractive index of the core changes due to the temperature. Sex problems can be solved.
[0025]
In addition, the light transmission center wavelength is deviated from the set wavelength such as the ITU grid wavelength due to manufacturing errors (thickness, width, refractive index, etc.) of the arrayed waveguide section constituting the arrayed waveguide grating. In this case, the temperature at which the light transmission center wavelength becomes the set wavelength is calculated using (Equation 2), and the temperature of the arrayed waveguide grating is set to this calculated temperature, and a Peltier element, a heater, etc. If the temperature is adjusted by the temperature adjusting means, the light transmission center wavelength can be adjusted to the grid wavelength.
[0026]
However, in order to keep the temperature of the arrayed waveguide type diffraction grating constant by using a temperature adjusting means such as a Peltier element or a heater, the Peltier element or the heater must be constantly energized with, for example, 1 W for temperature adjustment. In other words, there was a problem that the cost was high.
[0027]
In addition, in order to use electrical components such as Peltier elements and heaters, naturally, a controller, control thermistor, thermocouple, etc. are required. May not be suppressed accurately.
[0028]
Furthermore, the connection between the arrayed waveguide type diffraction grating and the optical fiber array is generally performed using an adhesive, and when the temperature of the arrayed waveguide type diffraction grating is controlled to a temperature higher than room temperature by a Peltier element or a heater, The adhesive interposed between the connection surface of the arrayed waveguide diffraction grating and the optical fiber expands or softens, for example, depending on the temperature above room temperature. Therefore, when the temperature of the arrayed waveguide grating is kept constant using a Peltier element or the like, the optical input waveguide 2 or the optical output of the arrayed waveguide grating is expanded by the expansion or softening of the adhesive. There is a problem in that the connection loss between the waveguide 6 and the optical fiber increases and the reliability of the connection between the arrayed waveguide grating and the optical fiber is impaired.
[0029]
The present invention has been made to solve the above problems, and an object of the present invention is to provide an inexpensive arrayed waveguide grating capable of accurately suppressing the temperature dependence of the light transmission center wavelength. is there.
[0030]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration as means for solving the problems. That is, in the first invention, the first slab waveguide is connected to the output side of one or more optical input waveguides arranged in parallel, and the first slab waveguide is connected to the output side of the first slab waveguide. A plurality of arrayed waveguides having different lengths that propagate light derived from the slab waveguide are connected to each other, and a second slab waveguide is connected to the output side of the plurality of arrayed waveguides, On the output side of the second slab waveguide, a waveguide forming region to which a plurality of light output waveguides arranged in parallel is connected is formed on the substrate, and a plurality of different input signals input from the light input waveguide are formed. An arrayed waveguide type diffraction grating having an optical demultiplexing function of demultiplexing light of one or more wavelengths from light having a wavelength and outputting the demultiplexed light from each optical output waveguide, and the first slab waveguide At least one of the second slab waveguides is in relation to the central axis of the light traveling direction of the slab waveguide. The first slab waveguide includes a first slab waveguide including the first slab waveguide and the second slab waveguide. The first slab waveguide includes the first slab waveguide. It is separated into two waveguide formation regions, and there is a problem with a configuration in which end surface interval varying means for varying the distance between the first waveguide formation region end surface and the second waveguide formation region end surface facing each other is provided. As a means to solve the problem.
[0031]
According to a second aspect of the invention, in addition to the configuration of the first aspect of the invention, the end face spacing variable means outputs from the respective optical output waveguides by varying the end face spacing of the first and second waveguide forming regions. The temperature-dependent fluctuation reducing means for reducing the temperature-dependent fluctuation of the light transmission center wavelength of the output light is a means for solving the problem.
[0032]
  Furthermore, the third aspect of the invention is characterized in that, in addition to the configuration of the first or second aspect of the invention, the end surface interval varying means isThe first waveguide forming region end face and the second waveguide forming region end face that face each other are in a parallel state.The structure is a means to solve the problem.
[0033]
  Furthermore, a fourth invention is the above-described configuration of the first or second invention,The end face spacing variable means is configured such that the first waveguide forming region end surface and the second waveguide forming region end surface facing each other are in a non-parallel state.The structure is a means to solve the problem.
[0034]
  In addition5The invention of the above3In addition to the configuration of the invention, the end surface interval varying means isIt has a member provided in a manner straddling the first waveguide formation region and the second waveguide formation region, and the member is a high thermal expansion coefficient member having a larger thermal expansion coefficient than the waveguide formation region and the substrate. is thereThe structure is a means to solve the problem.Furthermore, in the sixth invention, in addition to the configuration of the third invention, the first waveguide formation region and the second waveguide formation region are disposed on a base, and the first waveguide formation is performed. One of the region and the second waveguide formation region is fixed to the base, and the other is disposed so as to be movable with respect to the base. The other end is fixed to the base and has a member interposed between the movable waveguide forming region and the base, and the member is formed as a waveguide. A structure that is a high thermal expansion coefficient member having a larger thermal expansion coefficient than the region and the substrate serves as means for solving the problem.
[0035]
  Furthermore, a seventh invention is the above-mentioned first4In addition to the configuration ofThe first waveguide formation region and the second waveguide formation region are disposed on the base, and one of the first waveguide formation region and the second waveguide formation region is fixed to the base, and the other The one end side is disposed on the base via a hinge that can be elastically deformed so as to be tiltable with respect to the one waveguide formation region. A member that is in contact with a position serving as an action point for tilting with respect to the hinge in the waveguide forming region, the other end being fixed to the base, and interposed between the movable waveguide forming region and the base The member is a high thermal expansion coefficient member having a larger coefficient of thermal expansion than the waveguide forming region and the substrate.The structure is a means to solve the problem.
[0036]
The present inventor paid attention to the linear dispersion characteristic of the arrayed waveguide type diffraction grating in order to suppress the temperature dependence of the arrayed waveguide type diffraction grating. The light incident from the optical input waveguide in the arrayed waveguide grating is diffracted by the first slab waveguide (input slab waveguide) to excite the arrayed waveguide. As described above, the lengths of adjacent arrayed waveguides are different from each other by ΔL. Therefore, the light propagated through the arrayed waveguide satisfies (Equation 3) and is condensed at the output end of the second slab waveguide (output-side slab waveguide).
[0037]
[Equation 3]

[0038]
In (Equation 3), n_sIs the equivalent refractive index of the first slab waveguide and the second slab waveguide, n_cIs the equivalent refractive index of the arrayed waveguide, φ is the diffraction angle, m is the diffraction order, d is the spacing between adjacent arrayed waveguides, and λ is the light output from each optical output waveguide as described above. The transmission center wavelength.
[0039]
Here, the light transmission center wavelength where the diffraction angle φ = 0 is λ.₀Then λ₀Is represented by (Equation 4). The wavelength λ₀Is generally called the center wavelength of an arrayed waveguide grating.
[0040]
[Expression 4]

[0041]
In FIG. 3, the central axis direction of the light traveling direction of the first and second slab waveguides 3 and 5 is defined as the Y direction, and the direction orthogonal to the Y direction is defined as the X direction. If the condensing position of the arrayed waveguide grating where the diffraction angle φ = 0 is point O, the diffraction angle φ = φ_pThe light condensing position (position at the output end of the second slab waveguide) having the position is, for example, the position of the point P (position shifted from the point O in the X direction). Here, if the distance in the X direction between O and P is x, (Equation 5) holds between the wavelength λ.
[0042]
[Equation 5]

[0043]
In (Equation 5), L_fIs the focal length of the second slab waveguide and n_gIs the group index of the arrayed waveguide. Note that the group refractive index n of the arrayed waveguide_gIs the equivalent refractive index n of the arrayed waveguide_cIs given by (Equation 6).
[0044]
[Formula 6]

[0045]
In the above (Expression 5), the input end of the optical output waveguide is arranged and formed at a distance dx in the X direction from the focal point O of the second slab waveguide, thereby extracting light having different wavelengths by dλ. Means that it is possible.
[0046]
Further, the relationship of (Equation 5) is similarly established for the first slab waveguide 3. That is, for example, when the focal point center of the first slab waveguide 3 is a point O ′ and a point at a position shifted by a distance dx ′ in the X direction from the point O ′ is a point P ′, light is transmitted to the point P ′. When incident, the output wavelength is shifted by dλ ′. This relationship can be expressed by an equation (7).
[0047]
[Expression 7]

[0048]
In (Expression 7), L_f'Is the focal length of the first slab waveguide. This (Equation 7) is obtained by arranging and forming the output end of the optical input waveguide at a position separated from the focal point O ′ of the first slab waveguide by a distance dx ′ in the X direction. This means that it is possible to extract light having different wavelengths by dλ ′ in the waveguide.
[0049]
Therefore, when the light transmission center wavelength output from the optical output waveguide of the arrayed waveguide type diffraction grating is shifted by Δλ due to a change in the ambient temperature of the arrayed waveguide type diffraction grating, the optical wavelength is set so that dλ ′ = Δλ. If the output end position of the input waveguide is shifted by the distance dx ′ in the X direction (that is, the direction perpendicular to the central axis of the light traveling direction of the slab waveguide), for example, in the optical output waveguide formed at the focal point O, the wavelength shift Since the same operation occurs with respect to other optical output waveguides, the light transmission center wavelength shift Δλ can be corrected (cancelled).
[0050]
In the present invention having the above-described configuration, at least one of the first slab waveguide and the second slab waveguide is cut and separated by a cut surface that obliquely intersects the central axis of the light traveling direction of the slab waveguide. .
[0051]
Therefore, when it is assumed that the first slab waveguide is cut and separated, the end face of the first waveguide forming region including the separated slab waveguide on one side cut and separated by the end face spacing variable means. And the distance between the end faces of the second waveguide forming region including the other separated slab waveguide, for example, the output end position of the optical input waveguide is centered in the light traveling direction of the first slab waveguide. Shift in a direction perpendicular to the axis. If it does so, it will become possible to shift the light transmission center wavelength of the output light output from each optical output waveguide by the said principle.
[0052]
Further, the end face interval changing means makes the temperature dependent fluctuation (wavelength shift) Δλ of each light transmission center wavelength equal to dλ so as to reduce the temperature dependence fluctuation of each light transmission center wavelength. If the output end position of the optical input waveguide is moved by changing the interval, the light transmission center wavelength shift can be eliminated.
[0053]
Strictly speaking, it propagates in the first slab waveguide from the output end of the optical input waveguide to the input end of the arrayed waveguide by changing the end face spacing between the first and second waveguide forming regions. Focal length L_f'Varies slightly, but the focal length of the first slab waveguide in the currently used arrayed waveguide grating is on the order of several millimeters, while the optical transmission center wavelength correction of the arrayed waveguide grating is The above-mentioned end face interval variable amount that moves for the purpose is on the order of several μm to several tens of μm, which is very small compared to the focal length of the first slab waveguide.
[0054]
Therefore, there is no problem even if the change in the focal length is substantially ignored. From this, as described above, the end surface of the first waveguide formation region and the end surface of the second waveguide formation region are reduced so as to reduce the temperature-dependent variation of each light transmission center wavelength in the arrayed waveguide grating. If the interval is adjusted, it is possible to eliminate the light transmission center wavelength shift.
[0055]
Here, the relationship between the temperature change amount and the position correction amount of the optical input waveguide is derived. Since the temperature dependence of the light transmission center wavelength (the amount of shift of the light transmission center wavelength depending on the temperature) is expressed by the above (Equation 2), the light transmission center wavelength shift amount Δλ is expressed as 8).
[0056]
[Equation 8]

[0057]
When the temperature change amount T and the optical input waveguide position correction amount dx ′ are obtained from (Equation 7) and (Equation 8), (Equation 9) is derived.
[0058]
[Equation 9]

[0059]
Therefore, in the present invention, the output end position of the optical input waveguide can be moved in a direction orthogonal to the central axis of the light traveling direction of the first slab waveguide by the position correction amount dx ′ represented by (Equation 9). Thus, by variably adjusting the distance between the end face of the first waveguide formation area and the end face of the second waveguide formation area by the end face distance changing means, it is possible to eliminate the light transmission center wavelength shift.
[0060]
Further, as described above, the arrayed waveguide type diffraction grating is formed by utilizing the reciprocity of light, and the second slab waveguide side is cut and separated and guided in accordance with this cutting and separation. Even when the waveguide formation region is cut and separated to form the first waveguide formation region and the second waveguide formation region, the same effect as described above can be obtained by the action of the end face interval varying means, and each light transmission It becomes possible to eliminate the temperature-dependent fluctuation of the center wavelength.
[0061]
Furthermore, in the present invention, based on the above principle, the optical transmission center wavelength shift due to the operating temperature of the arrayed waveguide grating is suppressed without using a Peltier element or a heater, and the temperature of the optical transmission center wavelength is made temperature independent. Therefore, as in the case of providing temperature control means including Peltier elements and heaters, there is no need to energize at all times, and there is no temperature correction error due to assembly errors of parts. There is no risk of increasing the connection loss between the arrayed waveguide grating and the optical fiber by maintaining the arrayed waveguide grating.
[0062]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the present embodiment, the same reference numerals are assigned to the same name portions as in the conventional example, and the duplicate description thereof is omitted. FIG. 1 is a schematic plan view of a first embodiment of an arrayed waveguide grating according to the present invention. In addition, (a) of the figure shows a plan view of the arrayed waveguide type diffraction grating of the present embodiment, and (b) of the figure shows a side view thereof.
[0063]
As shown in the figure, the arrayed waveguide type diffraction grating of the present embodiment also has a core waveguide structure formed on the substrate 1 like the conventional arrayed waveguide type diffraction grating. The formation region of the waveguide structure on the substrate 1 is shown as a waveguide formation region 10 (10a, 10b).
[0064]
As in the conventional example, the arrayed waveguide type diffraction grating of the present embodiment example has one optical input waveguide 2, a first slab waveguide 3, a plurality of arrayed waveguides 4, and a second slab waveguide 5. The arrayed waveguide 4 and the optical output waveguide 6 are arranged in parallel with each other with a predetermined waveguide interval. In the arrayed waveguide type diffraction grating, the first slab waveguide 3 is cut and separated at a cut surface 8 that obliquely intersects the central axis (Y direction in the figure) of the light traveling direction of the first slab waveguide 3. Has been.
[0065]
In the present embodiment, the substrate 1 and the waveguide forming region (waveguide forming region) 10 are also cut and separated into two parts along the cutting surface 8 of the first slab waveguide 3. . In a mode straddling the first waveguide formation region 10a including the separation slab waveguide 3a and the first waveguide formation region 10b including the separation slab waveguide 3b, the thermal expansion coefficient is larger than that of the waveguide formation region 10, and the substrate A high thermal expansion coefficient member 7 having a thermal expansion coefficient larger than 1 is provided, and the high thermal expansion coefficient member 7 is fixed to the lower substrate 1a, 1b side of the waveguide forming regions 10a, 10b by an adhesive 13. .
[0066]
In the present embodiment, the high thermal expansion coefficient member 7 functions as an end surface interval varying means that varies the interval between the end surface 8a of the first waveguide forming region 10a and the end surface 8b of the second waveguide forming region 10b. Further, the end face interval varying means is configured to vary the distance between the end face 8a and the end face 8b with the end face 8a of the first waveguide forming area 10a and the end face 8b of the second waveguide forming area 10b facing each other in a parallel state. It is made.
[0067]
In FIG. 1, when the central axis direction of the light traveling direction of the first slab waveguide 3 is the Y direction and the direction orthogonal to the Y direction is the X direction, the end face interval varying means is the distance between the end face 8a and the end face 8b. Is changed to change the position of the output end 20 of the optical input waveguide 2 in the X direction, and this change has a function of eliminating the shift of the light transmission center wavelength of the arrayed waveguide grating.
[0068]
The high thermal expansion coefficient member 7 has a thermal expansion coefficient of, for example, 2.5 × 10 so that the thermal expansion coefficient contracts in accordance with the distance between the end faces 8a and 8b that can perform this function.^-5It is made of (1 / K) Al (aluminum).
[0069]
In this way, by forming the high thermal expansion coefficient member 7 in this way, in this embodiment, the end face interval changing means can change the interval between the end faces 8a and 8b of the first and second waveguide forming regions 10a and 10b. Thus, temperature-dependent variation reducing means for reducing the temperature-dependent variation of the light transmission center wavelength of the output light output from each light output waveguide 6 is formed.
[0070]
In this embodiment, each parameter in the waveguide configuration is configured as follows. That is, the focal length L of the first slab waveguide 3_f'And the focal length L of the second slab waveguide 5_fAnd the value is 9 mm, and the equivalent refractive index of the first slab waveguide 3 and the equivalent refractive index of the second slab waveguide 5 are both n at 25 ° C._sThe value is 1.453 for light having a wavelength of 1.55 μm. Further, the equivalent refractive index n of the arrayed waveguide 4 with respect to light having a wavelength of 1.55 μm._cIs 1.451, the group refractive index n of the arrayed waveguide_gIs 1.475, the optical path length difference ΔL between the arrayed waveguides 4 is 65.2 μm, the distance between adjacent arrayed waveguides 4 is 15 μm, and the diffraction order m is 61.
[0071]
Therefore, in the arrayed waveguide type diffraction grating of this embodiment, the light transmission center wavelength λ where the diffraction angle φ = 0 is obtained.₀As is clear from the above (Equation 4), λ₀= 1550.9 nm.
[0072]
By the way, in order to suppress the temperature dependence of the arrayed waveguide type diffraction grating, the present inventor paid attention to the linear dispersion characteristics of the arrayed waveguide type diffraction grating and used the above (Equation 1) to (Equation 9). As described above, the relationship between the use environment temperature change amount T of the arrayed waveguide grating and the position correction amount dx ′ of the optical input waveguide was obtained. And it confirmed that this relationship was represented by said (Formula 9).
[0073]
Therefore, in this embodiment, based on the parameters of the waveguide configuration of the arrayed waveguide type diffraction grating and (Equation 9), the change amount T of the ambient temperature of the arrayed waveguide type diffraction grating and the optical input waveguide 2 When the relationship of the position correction amount dx ′ was obtained, it was found that the relationship shown in (Equation 10) was obtained.
[0074]
[Expression 10]

[0075]
Therefore, in this embodiment, when the use environment temperature of the arrayed waveguide grating changes by 10 ° C., the position of the output end of the optical input waveguide 2 is set in the X direction (the optical progression of the first slab waveguide 3). If correction (movement) of about 3.83 μm is performed in a direction orthogonal to the central axis of the direction, the calculation can correct the center wavelength deviation due to temperature.
[0076]
Therefore, in the present embodiment, when the operating environment temperature of the arrayed waveguide grating increases by 10 ° C., the first waveguide formation region 10a has an arrow A in the figure with respect to the second waveguide formation region 10b. The distance between the end face 8a and the end face 8b is widened in the direction, so that the position of the output end 20 of the optical input waveguide 2 is moved in the A ′ direction by about 3.83 μm.
[0077]
On the contrary, in the present embodiment, when the operating environment temperature of the arrayed waveguide grating decreases by 10 ° C., the first waveguide formation region 10a is compared with the second waveguide formation region 10b. The end face 8a is moved so that the distance between the end face 8a and the end face 8b is narrowed by moving in the direction of arrow B in the figure, and the position of the output end 20 of the optical input waveguide 2 is moved in the B ′ direction by about 3.83 μm. And a variable amount of the gap between the end faces 8b.
[0078]
Then, the size of the high thermal expansion coefficient member 7 is formed so as to obtain this variable amount of space, and the thermal expansion and contraction of the high thermal expansion coefficient member 7 in the direction of reducing the temperature-dependent fluctuation of each light transmission center wavelength, The first waveguide formation region 10a and the second waveguide formation region 10b are moved relative to each other.
[0079]
In manufacturing the arrayed waveguide type diffraction grating according to this embodiment, the inventor applied a fiber grating temperature compensation package to assemble a module. That is, a dicing saw was used for cutting the first slab waveguide 3, and a matching grease having a refractive index matching that of quartz glass was applied to the cut surface 8 in order to prevent reflection at the cut surface 8. The adhesive 13 used for bonding the high thermal expansion coefficient member 7 and the waveguide forming region 10a was a thermosetting adhesive and cured at 100 ° C.
[0080]
The present embodiment is configured as described above, and the first slab waveguide 3 is separated from the first slab waveguide 3 by the cut surface 8 that obliquely intersects with the central axis in the light traveling direction of the first slab waveguide 3. When the operating environment temperature of the arrayed waveguide type diffraction grating is changed by being cut and separated into the waveguides 3a and 3b, the end surface 8a of the first waveguide forming region 10a is separated from the end surface 8a by the high thermal expansion coefficient member 7 as the end surface interval varying means. The interval between the end faces 8b of the second waveguide forming region 10b is variable.
[0081]
The position of the output end 20 of the optical input waveguide 2 reduces the temperature-dependent variation of the light transmission center wavelength output from each optical output waveguide 6 of the arrayed waveguide grating (arrow in FIG. 1). A ′ direction or arrow B ′ direction).
[0082]
Further, the amount of movement in the X direction of the output end 20 of the optical input waveguide 2 is the position correction amount dx ′ obtained by the above (Equation 10), and the end face interval varying means is used to form the first and second waveguides. This embodiment is configured to compensate for the temperature-dependent variation of the light transmission center wavelength of the output light output from the respective optical output waveguides 6 by varying the distance between the end faces 8a and 8b of the regions 10a and 10b. The example shows that even if the operating environment temperature of the arrayed waveguide grating changes, the light transmission center wavelength shift accompanying this temperature change can be eliminated, and the so-called temperature-independent type that does not depend on the operating environment temperature. An arrayed waveguide grating can be used.
[0083]
When the inventor actually measured the temperature change of the light transmission center wavelength at an environmental temperature of 0 ° C. to 80 ° C., the result shown in the characteristic line a in FIG. The amount of shift) was about 0.01 nm or less, and it was confirmed that even if the use environment temperature was changed within the range of 0 ° C. to 80 ° C., the light transmission center wavelength was hardly shifted.
[0084]
FIG. 2 shows a conventional arrayed waveguide type diffraction in which each parameter of the waveguide configuration in the arrayed waveguide type diffraction grating is formed in the same manner as in the present embodiment and the first slab waveguide 3 is not separated. The result of measuring the temperature change of the light transmission center wavelength at the ambient temperature of 0 ° C. to 80 ° C. in the lattice is also shown (characteristic line b in FIG. 2). As is apparent from the comparison between the characteristic line a and the characteristic line b, the arrayed waveguide type diffraction grating of the present embodiment example is dependent on the temperature dependence of the light transmission center wavelength, which is a problem in the conventional arrayed waveguide type diffraction grating. It can be understood that this is an excellent arrayed waveguide type diffraction grating suitable for practical use such as for optical wavelength multiplex communication.
[0085]
Further, according to the present embodiment, the end face interval varying means is configured by providing the high thermal expansion coefficient member 7 across the first waveguide formation region 10a and the second waveguide formation region 10b. Therefore, the apparatus configuration can be greatly simplified, and the cost of the apparatus can be reduced and the manufacturing yield can be improved.
[0086]
Furthermore, in the present embodiment, the high thermal expansion coefficient member 7 applied as the end face interval varying means is made of inexpensive Al, so that the cost of the apparatus can be further reduced.
[0087]
Further, according to the present embodiment example, since it is not necessary to use a Peltier element or a heater, it is not always necessary to energize as in the case where a temperature adjusting means including a Peltier element or a heater is provided. There is no temperature correction error, and there is no risk of increased connection loss between the arrayed waveguide grating and the optical fiber due to maintaining the arrayed waveguide grating at a temperature above room temperature.
[0088]
Therefore, the arrayed waveguide type diffraction grating of the present embodiment can reliably eliminate the temperature dependence of the light transmission center wavelength, and is excellent in connection reliability with the optical fiber on the connection partner side and at low cost. An arrayed waveguide type diffraction grating can be used.
[0089]
Furthermore, according to the present embodiment example, the first slab waveguide 3 is cut by the cut surface 8, and therefore, for example, due to a manufacturing error of the arrayed waveguide portion constituting the arrayed waveguide grating. When the light transmission center wavelength is deviated from a set wavelength such as an ITU grid wavelength, the distance between the end faces of the first and second waveguide formation regions 10a and 10b is shifted by that amount, and the optical input waveguide 2 By shifting the position in the X direction, the light transmission center wavelength can be set to a set wavelength such as a grid wavelength at a set temperature.
[0090]
FIG. 4 is a schematic plan view of a second embodiment of the arrayed waveguide grating according to the present invention. 2A shows a plan view of the arrayed waveguide type diffraction grating of the present embodiment, and FIG. 2B shows a C-C ′ sectional view thereof.
[0091]
The second embodiment is configured in substantially the same manner as the first embodiment. The second embodiment is different from the first embodiment in that an arrayed waveguide grating is used. That is, the end face interval variable means is configured by interposing a high thermal expansion coefficient member 7 between the base 9 to be disposed and the side surface of the first waveguide forming region 10a.
[0092]
Specifically, the base 9 is formed of a material having a low coefficient of thermal expansion such as quartz glass or Invar lot, and the high coefficient of thermal expansion member 7 has a coefficient of thermal expansion of 1.65 × 10.^-5It is formed of (1 / K) Cu (copper). The high thermal expansion coefficient member 7 is not connected to the upper surface of the first waveguide formation region 10a, and the upper plate portion 7a provided along the upper surface of the second waveguide formation region 10b and the first waveguide formation The side plate portion 7 b is provided along the side surface of the region 10 a, and the side plate portion 7 b of the high thermal expansion coefficient member 7 is fixed to the base 9 with screws 11.
[0093]
The first waveguide formation region 10a and the substrate 1a below the first waveguide formation region 10a are fixed to the base 9. On the other hand, the second waveguide formation region 10b and the substrate 1b below the first waveguide formation region 10a are along the surface of the base 9. They are slidably arranged in the direction of arrow A and arrow B in the figure. The upper surface of the second waveguide forming region 10 b is fixed to the upper plate portion 7 a of the high thermal expansion coefficient member 7 by the adhesive 13.
[0094]
The second embodiment is configured as described above. In the second embodiment, the second waveguide formation region 10b is changed to the first waveguide formation region according to the thermal contraction of the high thermal expansion coefficient member 7. By relative movement with respect to 10a, the end surface 8b of the second waveguide forming region 10b and the first waveguide forming region are formed in accordance with the thermal expansion and contraction of the high thermal expansion coefficient member 7 as in the first embodiment. The distance from the end surface 8a of 10a can be varied, and the same effect can be obtained by the substantially same operation as in the first embodiment.
[0095]
Also in the second embodiment, the end face interval varying means has a simple configuration including the high thermal expansion coefficient member 7 and the base 9, and the configuration of the arrayed waveguide type diffraction grating can be avoided from being complicated and easy. Can be made.
[0096]
Further, in the second embodiment, Cu or the like whose linear (thermal) expansion coefficient is not as large as Al can be used, and there is an advantage that the material of the high thermal expansion coefficient member 7 does not need to be specifically limited. This is because, in the first embodiment, in consideration of the arrangement of the high thermal expansion coefficient member 7, it is necessary to increase the thermal expansion of the high thermal expansion coefficient member 7, and it is necessary to form it with Al or the like. In the second embodiment, for example, even when the chip size (the size of the waveguide forming regions 10a and 10b) is small and the high thermal expansion coefficient member 7 does not fit within the chip size, the high thermal expansion coefficient member 7 can be as large as Al. A material that does not have a large linear expansion coefficient can be used.
[0097]
FIG. 5 is a plan view schematically showing a third embodiment of the arrayed waveguide grating according to the present invention. The third embodiment is configured in substantially the same way as the second embodiment, and the third embodiment is different from the second embodiment in that the end face interval varying means are mutually connected. That is, the end surface 8a of the first waveguide forming region 10a and the end surface 8b of the second waveguide forming region 10b facing each other are in a non-parallel state so that the distance between the end surface 8a and the end surface 8b is variable.
[0098]
Specifically, in the third embodiment, a hinge 15 formed of an elastically deformable plastic film is fixed to one end side of the first waveguide forming region 10a with an adhesive 13, and A notch 12 is formed on the other end side of the waveguide forming region 10a. Then, the base end side of the high thermal expansion coefficient member 7 is fixed to the base 9, and the distal end side of the high thermal expansion coefficient member 7 is provided in contact with the notch 12. The waveguide forming region 10a is tilted with S in the figure as a fulcrum.
[0099]
In the third embodiment, with such a configuration, the end surface 8a of the first waveguide forming region 10a and the end surface 8b of the second waveguide forming region 10b facing each other are in a non-parallel state in which the end surface 8b obliquely intersects. The distance between the end surface 8a and the end surface 8b is variable (in other words, the angle between the end surface 8a and the end surface 8b is variable), and the third embodiment is similar to the first and second embodiments. Thus, the same effect can be achieved.
[0100]
In addition, this invention is not limited to the said embodiment example, Various aspects can be taken. For example, in each of the embodiments described above, an Al or Cu plate is used as the high thermal expansion coefficient member 7, but the high thermal expansion coefficient member 7 is not necessarily Al or Cu, and waveguide formation other than Al or Cu is used. You may form with a material with a larger thermal expansion coefficient than an area | region.
[0101]
In each of the above embodiments, the first slab waveguide 3 is cut and separated. However, the arrayed waveguide grating is formed by utilizing the reciprocity of light, and the second slab waveguide is formed. By cutting and separating the waveguide 5 side, the distance between the end face of the first waveguide forming area and the end face of the second waveguide forming area facing each other is changed, and light transmission of output light output from each light output waveguide is performed. The temperature-dependent fluctuation of the center wavelength may be reduced, and in this case, the same effect as the above embodiments can be obtained, and the temperature-dependent fluctuation of the light transmission center wavelength can be eliminated.
[0102]
Further, in each of the above embodiments, the distance between the end surface 8a of the first waveguide formation region 10a formed by cutting and separating the first slab waveguide 3 and the end surface 8b of the second waveguide formation region 10b is set. Although the variable end surface interval variable means is formed by providing the high thermal expansion coefficient member 7, the configuration of the end surface interval variable means is not particularly limited, and is appropriately set. That is, the end face interval varying means changes the distance between the end face 8a of the first waveguide forming region 10a and the end face 8b of the second waveguide forming region 10b, thereby allowing light transmission through the arrayed waveguide grating. It is only necessary to have a function capable of shifting the center wavelength.
[0103]
In particular, the end face interval varying means is arranged such that the first and second waveguide forming regions are arranged in a direction to reduce the temperature-dependent fluctuation of each light transmission center wavelength of the arrayed waveguide type diffraction grating, as in the above embodiments. It is desirable to have a function of varying the end face spacing of the first and second end face spacing varying means in this way, which is a problem in the conventional arrayed waveguide grating as in the above embodiments. The temperature dependence of the light transmission center wavelength can be eliminated, and an excellent arrayed waveguide type diffraction grating suitable for practical use such as for optical wavelength multiplexing communication can be obtained.
[0104]
Furthermore, the detailed values such as the equivalent refractive index, the number, and the size of each of the waveguides 2, 3, 4, 5, and 6 constituting the arrayed waveguide type diffraction grating of the present invention are not particularly limited, and are appropriately determined. Is set.
[0105]
【The invention's effect】
According to the first aspect of the present invention, at least one of the first slab waveguide and the second slab waveguide is cut and separated at a cut surface that obliquely intersects the central axis of the light traveling direction of the slab waveguide. Since the interval between the end face of the first waveguide formation region and the end face of the second waveguide formation region formed by the cutting and separation is variable, for example, the output end position of the optical input waveguide and the light can be changed by changing the end surface interval. The light transmission center wavelength of the arrayed waveguide grating can be shifted by shifting the input end position of the output waveguide in the direction orthogonal to the central axis.
[0106]
According to the second invention, in addition to the first invention, the end face spacing variable means is output from the respective optical output waveguides by varying the end face spacing of the first and second waveguide forming regions. Temperature-dependent fluctuation reducing means for reducing the temperature-dependent fluctuation of the light transmission center wavelength of the output light to be obtained, so that the temperature-dependent fluctuation of each light transmission center wavelength can be achieved by setting the end face interval variable amount to an appropriate value. (Wavelength shift) can be eliminated.
[0107]
Furthermore, according to the second aspect of the present invention, the shift of the light transmission center wavelength due to the use environment temperature of the arrayed waveguide grating is suppressed without using a Peltier element or a heater, and the light transmission center wavelength is made temperature independent. Therefore, as in the case of providing a temperature adjusting means including a Peltier element and a heater, there is no need for constant energization, no temperature correction error due to parts assembly error, and more than room temperature. There is no risk of increasing the connection loss between the arrayed waveguide grating and the optical fiber due to maintaining the arrayed waveguide grating at the temperature of.
[0108]
Therefore, the arrayed waveguide type diffraction grating according to the second aspect of the present invention has high connection reliability with the optical fiber on the other end of the connection, can reliably eliminate the temperature dependence of the light transmission center wavelength, and is an excellent array conductor with low cost. It can be a waveguide type diffraction grating.
[0109]
  Third, fourth, 5thAccording to the invention, a high thermal expansion coefficient member having a thermal expansion coefficient larger than that of the waveguide formation region is provided in a manner straddling the first waveguide formation region and the second waveguide formation region, or arrayed waveguide type diffraction A base on which a grating is disposed, a first waveguide formation region, and a second waveguide formation region;Moving side waveguide formation regionSince the end face spacing variable means is formed by interposing them, the end face spacing varying means can be formed with a simple configuration using a high thermal expansion coefficient member.
[0110]
  Therefore, the third and fourth, 5thAccording to the invention, the arrayed waveguide type diffraction grating having the above excellent effects can be easily manufactured with a simple configuration, and the cost can be reduced.
[0111]
  In addition6The second7As described in the invention, the first waveguide forming region end face and the second waveguide forming region end face facing each other can be set in a parallel state or a non-parallel state so that the above effect can be obtained. Various waveguide type diffraction gratings can be formed, and a suitable array waveguide type diffraction grating corresponding to the specifications of the arrayed waveguide type diffraction grating can be formed.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram showing a first embodiment of an arrayed waveguide grating according to the present invention by a plan view (a) and a side view (b).
FIG. 2 is a graph showing the temperature dependence of the light transmission center wavelength in the arrayed waveguide type diffraction grating of the embodiment described above compared with the temperature dependence of the light transmission center wavelength in the conventional arrayed waveguide type diffraction grating. .
FIG. 3 is an explanatory diagram showing a relationship between a light transmission center wavelength shift and positions of an optical input waveguide and an optical output waveguide in an arrayed waveguide type diffraction grating.
FIG. 4 is a main part configuration diagram showing a second embodiment of an arrayed waveguide grating according to the present invention by a plan view (a) and a sectional view (b).
FIG. 5 is a main part configuration diagram showing a third embodiment of an arrayed waveguide grating according to the present invention in plan view.
FIG. 6 is an explanatory view showing a conventional arrayed waveguide type diffraction grating configured by providing a Peltier element.
FIG. 7 is a graph showing light transmission characteristics of light output from one light output waveguide of an arrayed waveguide type diffraction grating.
[Explanation of symbols]
1 Substrate
2 Optical input waveguide
3 First slab waveguide
3a, 3b Separated slab waveguide
4 Arrayed waveguide
5 Second slab waveguide
6 Optical output waveguide
7 High thermal expansion coefficient members
8 Cut surface
8a, 8b End face
9 base
10, 10a, 10b Waveguide formation region
14 Locking member

Claims (7)

  A first slab waveguide is connected to the output side of one or more optical input waveguides arranged side by side, and the light derived from the first slab waveguide is output to the output side of the first slab waveguide. A plurality of arrayed waveguides having different lengths propagating through the plurality of arrayed waveguides are connected, and a second slab waveguide is connected to the output side of the plurality of arrayed waveguides. A waveguide forming region to which a plurality of parallel optical output waveguides are connected is formed on the substrate on the output side, and one of the lights having a plurality of different wavelengths input from the optical input waveguide is provided. An arrayed waveguide type diffraction grating having an optical demultiplexing function of demultiplexing light of the above wavelength and outputting from each optical output waveguide, wherein at least one of the first slab waveguide and the second slab waveguide One side is cut at a cross-section that crosses obliquely with respect to the central axis of the light traveling direction of the slab waveguide. A separated slab waveguide, wherein the waveguide formation region includes a first waveguide formation region including a separation slab waveguide on one side, and a second waveguide formation region including a separation slab waveguide on the other side. Arrayed waveguide type diffraction characterized in that end face interval variable means for changing the interval between the end faces of the first and second waveguide forming regions facing each other is provided. lattice.   The end face interval varying means is a temperature dependent variation reducing means for reducing the temperature dependent variation of the light transmission center wavelength of the output light output from the respective light output waveguides by varying the end face spacing of the first and second waveguide forming regions. The arrayed waveguide grating according to claim 1, wherein: 3. The arrayed waveguide according to claim 1, wherein the end face interval varying means includes a first waveguide forming region end face and a second waveguide forming region end face facing each other in a parallel state. Type diffraction grating. 3. The array guide according to claim 1, wherein the end face interval varying means is configured such that the first waveguide forming area end face and the second waveguide forming area end face facing each other are in a non-parallel state. Waveguide diffraction grating. The end face interval varying means has a member provided in a manner straddling the first waveguide forming region and the second waveguide forming region, and the member has a larger thermal expansion coefficient than the waveguide forming region and the substrate. 4. The arrayed waveguide grating according to claim 3 , wherein the arrayed waveguide grating is a high thermal expansion coefficient member. The first waveguide formation region and the second waveguide formation region are disposed on the base, and one of the first waveguide formation region and the second waveguide formation region is fixed to the base, and the other Is disposed so as to be movable with respect to the base, and the end surface interval varying means is fixed to a waveguide forming region where one end side is movable with respect to the base, and the other end side is fixed to the base. And a member interposed between the movable waveguide forming region and the base, the member being a high thermal expansion coefficient member having a larger thermal expansion coefficient than the waveguide forming region and the substrate. The arrayed waveguide grating according to claim 3 . The first waveguide formation region and the second waveguide formation region are disposed on the base, and one of the first waveguide formation region and the second waveguide formation region is fixed to the base, and the other is disposed on the base through the tilting can elastically deformable hinge movement against one end to said one waveguide forming region, the end face pitch adjusting means, one end of the can the moving guide A member that is in contact with a position serving as an action point for tilting with respect to the hinge in the waveguide forming region, the other end being fixed to the base, and interposed between the movable waveguide forming region and the base 5. The arrayed waveguide grating according to claim 4 , wherein the member is a high thermal expansion coefficient member having a thermal expansion coefficient larger than that of the waveguide forming region and the substrate.

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