JP3677883B2

JP3677883B2 - Surface emitting semiconductor laser element, surface emitting semiconductor laser array, surface emitting semiconductor laser beam scanner, surface emitting laser beam recording apparatus, and laser recording method

Info

Publication number: JP3677883B2
Application number: JP22018996A
Authority: JP
Inventors: 朗坂本; 将央山本; 茂行大竹; 泉岩佐
Original assignee: Fuji Xerox Co Ltd; Fujifilm Business Innovation Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 1996-08-21
Filing date: 1996-08-21
Publication date: 2005-08-03
Anticipated expiration: 2016-08-21
Also published as: JPH1065266A

Description

【０００１】
【発明の属する技術分野】
本発明は、面発光型半導体レーザ素子、面発光型半導体レーザアレイ、面発光型半導体レーザビームスキャナ、面発光レーザビーム記録装置およびレーザ記録方法に関する。
【０００２】
【従来の技術】
従来の面発光レーザアレイとして、例えば、１組のレンズ系を用いて像面に投影するようにしたものがある。しかしながら、主走査および副走査方向に等倍率にて感光体に投影した場合、特に小径ドラム上に投影した際には、投影像面は平面であるのに対し、感光体ドラム面はある曲率をもつ円筒面となる。このため、感光体ドラム面が曲率をもつ副走査方向に焦点の位置ずれが生じることになる。この問題を解決するため、副走査方向の倍率を主走査方向のそれよりも低い倍率として、像の大きさを調整し焦点位置ずれを少なくする方法が提案されている（特願平８−８８７８号）。
【０００３】
【発明が解決しようとする課題】
しかしながら、通常の円形の面発光レーザを用い、主走査方向に所定の倍率で拡大し、副走査方向にはそれよりも小さい倍率で拡大するか若しくは縮小した場合には、感光面上に投影される副走査方向のビーム径は、主走査方向のビーム径よりも小さくなる。その結果、主走査方向の焦点深度よりも副走査方向の焦点深度が浅くなり、位置合わせに高い精度が要求される。また、感光体ドラムの偏心などによる位置ずれにより、感光体上に投影されるビーム径の変動が大きくなるなどの問題がある。
【０００４】
図１は焦点位置（ビームウェスト）からの位置ずれとビーム径の変化との関係を示す。例えば、波長７８０ｎｍのガウシアン型の強度プロファイルを有する焦点位置にて２１μｍに絞られたビームは、焦点位置からのずれが１ｍｍある場合でもビーム径は高々２４μｍ程度である。一方、波長７８０ｎｍのガウシアン型の強度プロファイルを有する焦点位置にて５μｍに絞られたビームは焦点位置からのずれが１ｍｍである場合にはビーム径は４０μｍ以上になり、位置変動に対して敏感である。
【０００５】
一方、例えば特開平２ー２９００９１号のように、端面発光型のレーザを基板上に配列しまたこの基板上にあるミラーを用いて基板に垂直な方向に出射する素子構造の場合、楕円型のビームが得られ、主走査方向および副走査方向のレンズ径の倍率と素子構造を適当な関係に選ぶと、投影されるビーム径は主走査方向並びに副走査方向に同じ大きさにすることができ、焦点深度を大きくすることができる。
【０００６】
しかしながら、端面発光型のレーザを基板上に配列し基板上にあるミラーを用いて基板に垂直な方向に出射する素子構造の場合、素子を集積する密度を大きくすることができず、レーザスポットを感光体上に高精度かつ高密度に配列して形成することができないという問題があった。
【０００７】
本発明は、前記実情に鑑みてなされたもので、投影面上でビーム径を真円に近いものとし、焦点深度を大きくとることができ、また位置合わせに要求される精度の制約を小さくすることができ、感光体ドラムの偏心により、感光体面上に投影されるビーム径の変動を低減することのできる、面発光型半導体レーザを提供することを目的とする。
【０００８】
【課題を解決するための手段】
そこで、本発明では、面発光型半導体レーザ素子から発生せしめられたビームを、光軸に対して垂直な１方向には所定の倍率で、また光軸に対して垂直なもう一方にはそれとは異なる倍率で拡大または縮小する投影光学系を用いて感光体上にスポット形成するに際し、感光体上でスポット系を真円に近いものにするように、光学系の倍率に対応した偏平率の発光パターンを有する面発光型レーザ素子を形成する。例えば感光体面上で２１μｍの真円のスポットを得る場合に、光学系の倍率が主走査方向に７倍、副走査方向に２倍の倍率を有する場合には、面発光型半導体レーザ素子の発光ビーム径がそれぞれの方向について３μｍ、１０．５μｍの素子を用意するというように、主走査方向および副走査方向の倍率に応じてビーム形状を調整している。通常垂直共振器型の面発光型半導体レーザでは、発光パターンはほぼ真円である。これはレーザ構造が基板面内にほぼ対称な形状に構成されていることによる。従ってレーザを構成する共振器構造を基板面内に非対称な構造とすることで、発光パターンを偏平な形状にすることができる。そしてまたこの面発光型半導体レーザを１次元または２次元状にアレイ化する場合には面発光型半導体レーザの非対称な発光パターンの方向が一様に揃っていれば、すべてのスポットについて感光体上でスポット径を真円に近いものにすることができる。
【０００９】
すなわち、本発明の第１の特徴は、半導体基板上で、活性層が上部及び下部の半導体多層反射膜により挟まれ、基板と垂直方向に光を放出する垂直共振器型の面発光型半導体レーザ素子において、前記上部及び下部の半導体多層反射膜の内少なくとも一方が基板面内の一方向について、他方向よりも長くなるように構成されると共に、前記上部の半導体多層反射膜上に設けられ、前記上部又は下部の半導体多層反射膜からレーザ発振された発光ビームが通過する柱状の第２の半導体多層反射膜と、前記第２の半導体多層反射膜の実効屈折率よりも低い材料によって該第２の半導体多層反射膜の周囲に形成された層とを具備し、前記第２の半導体多層反射膜を介して出射された前記発光ビームの強度パターンが方向性をもつように構成されたことにある。
【００１０】
本発明の第２の特徴は、半導体基板上で、活性層が上部及び下部の半導体多層反射膜により挟まれ、基板と垂直方向に光を放出する垂直共振器型の面発光型半導体レーザ素子において、前記活性層が、基板面内の一方向について、他方向よりも長くなるように構成されると共に、前記上部の半導体多層反射膜上に設けられ、前記上部又は下部の半導体多層反射膜からレーザ発振された発光ビームが通過する柱状の第２の半導体多層反射膜と、前記第２の半導体多層反射膜の実効屈折率よりも低い材料によって該第２の半導体多層反射膜の周囲に形成された層とを具備し、前記第２の半導体多層反射膜を介して出射された前記発光ビームの強度パターンが方向性をもつように構成されたことにある。
【００１１】
本発明の第３の特徴は、半導体基板上で、活性層が上部及び下部の半導体多層反射膜により挟まれ、基板と垂直方向に光を放出する垂直共振器型の面発光型半導体レーザ素子において、前記上部及び下部の半導体多層反射膜の外側またはこれらと活性層との間に設けられる電流狭窄領域が、基板面内の一方向について、他方向よりも長くなるように構成され、発光ビームの強度パターンが方向性をもつように構成されていることにある。
【００１２】
望ましくは、前記電流狭窄領域はＡｌＡｓ酸化物で構成されていることを特徴とする。
【００１３】
本発明の第４の特徴は、半導体基板上で、活性層が上部及び下部の半導体多層反射膜により挟まれ、基板と垂直方向に光を放出する垂直共振器型の面発光型半導体レーザ素子が、基板面内にアレイ状に複数個配列された面発光型半導体レーザアレイにおいて、前記面発光型半導体レーザ素子は、前記上部の半導体多層反射膜上に設けられ、前記上部又は下部の半導体多層反射膜からレーザ発振された発光ビームが通過する柱状の第２の半導体多層反射膜と、前記第２の半導体多層反射膜の実効屈折率よりも低い材料によって該第２の半導体多層反射膜の周囲に形成された層とを具備し、前記第２の半導体多層反射膜を介して出射された前記発光ビームの強度パターンが方向性をもつように構成されていることにある。
【００１４】
本発明の第５の特徴は、レーザ光源と、前記レーザ光源から出射されるビームを主走査方向で第１の倍率で拡大する第１のレンズ系と、副走査方向で第２の倍率で拡大または縮小する第２のレンズ系と、前記レーザ光源からのビームを駆動走査し、前記第１および第２のレンズ系を介して走査面上に導く駆動走査系とを具備し、前記レーザ光源が、前記第１および第２の倍率に合わせ、ビームが走査面上でほぼ真円となるように、素子の発光ビームの強度パターンが方向性をもつように構成された垂直共振器型の面発光型半導体レーザ素子を、基板面内にアレイ状に複数個配列してなる面発光型半導体レーザ装置で構成されていることにある。
【００１５】
本発明の第６の特徴は、レーザ光源と、前記レーザ光源から出射されるビームを主走査方向で第１の倍率で拡大する第１のレンズ系と、副走査方向で第２の倍率で拡大または縮小する第２のレンズ系と、ビームによって感光し静電潜像を形成する感光体と、前記レーザ光源からのビームを駆動走査し、前記第１および第２のレンズ系を介して感光体面上に導く駆動走査系と、前記静電潜像に基づいて画像記録を実行する記録手段とを具備し、前記レーザ光源が、前記第１および第２の倍率に合わせ、ビームが走査面上でほぼ真円となるように、素子の発光ビームの強度パターンが方向性をもつように構成された垂直共振器型の面発光型半導体レーザ素子を、基板面内にアレイ状に複数個配列してなる面発光型半導体レーザ装置で構成されていることにある。
【００１６】
本発明の第７の特徴は、レーザ光源から出射されるレーザ光を第１のレンズ系および第２のレンズ系を介して、主走査方向および副走査方向にそれぞれ第１および第２の倍率で拡大縮小し、これを駆動走査して、感光体面上に静電潜像を形成する工程と、前記静電潜像に基づいて画像記録を実行する記録工程とを含み、前記レーザ光源が、前記第１および第２の倍率に応じて、ビームが走査面上でほぼ真円となるように、素子の発光ビームの強度パターンが方向性をもつように構成された垂直共振器型の面発光型半導体レーザ素子を、基板面内にアレイ状に複数個配列してなる面発光型半導体レーザ装置で構成されていることにある。
【００１８】
本発明によれば、面発光型半導体レーザから発せられたビームを、光軸に対して垂直な１方向には所定の倍率で、光軸に対して垂直なもう一方向にはそれとは異なる倍率で拡大または縮小する投影光学系を用いて感光体上に導く際、これらの倍率に対応して各方向のビーム径を調整し、感光体上でほぼ真円となるようにしているため、焦点深度を大きくとることができ、位置合わせに要求される精度の制約を低減することができる。従って感光体ドラムが偏心している場合にも、ビーム径の変動を抑制することができる。
【００１９】
従ってこの面発光型半導体レーザ素子を用いて記録を行う場合、高精度で信頼性の高い記録を行うことが可能となる。
【００２０】
【実施例】
以下、本発明について、図面を参照しつつ説明する。
【００２１】
図２（ａ）および（ｂ）は本発明の第１の実施例の面発光型半導体レーザ装置の上面図、その断面図である。
【００２２】
この面発光型半導体レーザ装置は、ｎ型ガリウムヒ素（ＧａＡｓ）基板１上に形成されたｎ型Ａｌ_0.9Ｇａ_0.1Ａｓ／Ａｌ_0.3Ｇａ_0.7Ａｓ下部半導体多層反射膜２（多重回折ブラッグ反射鏡（ＤＢＲ）と、この上に形成されたアンドープのＡｌ_0.11Ｇａ_0.89量子井戸層とアンドープのＡｌ_0.3Ｇａ_0.7Ａｓ障壁層とからなる量子井戸活性層３と、ＡｌＡｓの酸化によって形成され、中央に開口を有する電流狭窄層４と、ｐ型Ａｌ_0.9Ｇａ_0.1Ａｓ／Ａｌ_0.3Ｇａ_0.7Ａｓ上部半導体多層反射膜５と、ｐ型ＧａＡｓコンタクト層（図示せず）と、ｐ型電極６が順次積層せしめられ、電流狭窄層４の側面が露呈する深さまで、発光領域およびその周辺を除いてエッチング除去され、角柱状の光制御領域７が形成されている。そしてここで上部半導体多層反射膜５の最下層に、中央の開口部を除いてＡｌＡｓ層が酸化されて形成された電流狭窄層が形成されており、この開口部以外の領域では堆積方向に電流が流れない構造となっている。なお、量子井戸活性層３と電流狭窄層４との間には量子井戸活性層３への不純物の侵入を保護するためにＡｌ_0.11Ｇａ_0.89Ａｓからなる分離層ｓが介在せしめられている。
【００２３】
また、ｐ型電極６の中央には電流狭窄層の開口の上部を含むように、第２の開口が形成されこの開口から上部半導体多層反射膜５上に第２の上部多層反射膜８が柱状をなすように突出して形成されている。
【００２４】
さらにこの光制御領域の周りは少なくとも上部多層反射膜５の途中まで窒化シリコンからなる第１の絶縁膜９で覆われ、この上層は、第２の上部多層反射膜８の高さまで酸化シリコンからなる第２の絶縁膜１０が形成され、この第２の上部多層反射膜８の柱状の部分とその周囲とで屈折率に差をもたせるようにし、図３および図４に示すように、この第２の上部多層反射膜８の形状に応じ、短手方向に偏平した楕円型のビームプロファイルが形成されるようになっている。ここで第２の上部多層反射膜８は、５：１の矩形形状を有しており、図３はこのときのビーム強度プロファイルの等高線を示し、図４はこれを３次元表示したものである。
【００２５】
そして基板裏面にはＡｕ−Ｇｅ／Ａｕからなるｎ側電極（図示せず）が形成されている。
【００２６】
ここでｎ型下部半導体多層反射膜２は、ｎ型Ａｌ_0.9Ｇａ_0.1Ａｓ層とｎ型Ａｌ_0.7Ｇａ_0.3ＡｓＧａＡｓ層とをそれぞれ膜厚λ／（４ｎr）（λ：発振波長，ｎ_r：屈折率）で約４０．５周期積層することによって形成されたもので、ｎ型不純物であるシリコン濃度は２×１０¹⁸ｃｍ^-3である。また、量子井戸活性層４は、アンドープのＡｌ_0.11Ｇａ_0.89量子井戸層（膜厚８ｎｍ×３）とアンドープのＡｌ_0.3Ｇａ_0.7Ａｓ障壁層（膜厚５ｎｍ×４）との組み合わせとする。また、上部半導体多層反射膜７は、ｐ型Ａｌ_0.9Ｇａ_0.1Ａｓ層とｐ型Ａｌ_0.7Ｇａ_0.3ＡｓＧａＡｓ層とをそれぞれ膜厚 λ／(４ｎ_r)(λ：発振波長，ｎ_r：屈折率）で交互に３０周期積層することによって形成されたもので、ｐ方不純物であるカーボン濃度は３×１０¹⁸ｃｍ^-3である。最後に第２の上部半導体多層反射膜８はアンドープである。ドーパントの種類についてはここで用いたものに限定されることなく、ｎ型であればセレン、ｐ型であれば亜鉛やマグネシウムなどを用いることも可能である。
【００２７】
なお前記実施例ではＡｌＡｓ層を選択酸化することにより柱状領域の側面から酸化膜を形成することにより電流狭窄を行うようにしたが、選択エッチングにより空隙を形成するようにしてもよい。なおこの電流狭窄層で囲まれる開口の形状は真円若しくは正方形状の対称な構造でもよいし、楕円または矩形などの非対称な構造であってもよい。
【００２８】
ここでは、発振波長λ：７８０ｎｍのレーザ光を取り出すように設計した。
【００２９】
この構成によれば、角柱状の光制御領域７の内部におけるキャリアの通過経路が、電流狭窄層４の開口の２組の対称面方向から狭められると共に光の閉じ込めも行われる。また第２の上部半導体多層反射膜８とその周りの第２の絶縁層１０とで屈折率に差を生じるため、より屈折率差の小さい対称面側に偏平となるような楕円型のビームプロファイルとなる。
またこれにより、出射光の偏波面はこの方向に安定化される。
【００３０】
次に、この面発光型半導体レーザ装置の製造工程について説明する。
【００３１】
まず、図２に示すように、有機金属気相成長（ＭＯＣＶＤ）法により、ｎ型ガリウムヒ素（ＧａＡｓ）（１００）基板１上に、ｎ型Ａｌ_0.9Ｇａ_0.1Ａｓ／Ａｌ_0.7Ｇａ_0.3Ａｓ下部半導体多層反射膜３と、アンドープのＡｌ_0.11Ｇａ_0.89量子井戸層とアンドープのＡｌ_0.3Ｇａ_0.7Ａｓ障壁層とからなる量子井戸活性層３と、Ａｌ_0.11Ｇａ_0.89Ａｓ層からなる分離層Ｓ、ＡｌＡｓ層とｐ型Ａｌ_0.9Ｇａ_0.1Ａｓ／Ａｌ_0.7Ｇａ_0.3Ａｓ上部半導体多層反射膜５と、ｐ型ＧａＡｓコンタクト層（図示せず）とを順次積層する。
そして基板を成長室から取出し、酸化シリコン膜などの絶縁膜を形成しフォトリソグラフィ技術を用いて、ＳｉＣｌ₄ガスを用いた反応性イオンエッチングにより、ＡｌＡｓ層が露出せしめられる深さまで半導体層をエッチング除去して、角柱状の半導体柱からなる光制御領域７を形成する。
【００３２】
続いてこの基板を、高温の水蒸気を充満させた石英管内で基板を４００℃に加熱し、約１０分間の熱処理を行うことにより露出したＡｌＡｓ層が外側断面から徐々に酸化され、酸化膜が形成され、最終的には酸化されずに残った領域が長方形形状となる。なお、ここで熱処理による酸化に代えて、硫酸過酸化水素溶液（Ｈ₂ＳＯ₄：Ｈ₂Ｏ₂：Ｈ₂Ｏ＝１：１：５）中に、約３０秒間浸すようにしても良く、これにより、ＡｌＡｓ層はいわゆるサイドエッチングにより外側断面から選択的に除去される。
【００３３】
この後、表面のレジストマスクを残したまま、窒化シリコン層からなる第１の絶縁層９を形成し、リフトオフにより柱状領域上面の第１の絶縁層を除去すると共に選択エッチングにより酸化シリコンを除去する。
【００３４】
この後し、蒸着法およびフォトリソグラフィ技術を用いて、光制御領域７の周りを覆うように環状のｐ側電極６を形成する。この中央のｐ側電極のパターニングで用いたレジストを残したまま第２の上部半導体多層反射膜８を形成し、リフトオフにより、このレジストと共に開口部以外の膜を除去し、柱状領域を形成する。
【００３５】
そして最後に、全体を覆うように酸化シリコン層からなる第２の絶縁層１０を形成し、基板裏面には全面にｎ側電極を形成して、図２に示した本発明にかかる第１の実施例の面発光型半導体レーザ装置が完成する。
【００３６】
なお、前記実施例では各半導体層は有機金属気相成長法で形成したが、これに限定されることなく分子線エピタキシー（ＭＢＥ）法などによっても良い。
【００３７】
また、半導体柱形成のためのマスクとして用いる絶縁膜についても、酸化シリコン膜に限定されることなく窒化シリコン膜など他の材料を用いても良い。
【００３８】
さらにまた、前記実施例ではＡｌＡｓ層を選択的に除去するためのエッチングに硫酸過酸化水素水溶液を用いたがＡｌ組成比に対するエッチングレートの選択性が高いものが望ましく、Ａｌ組成比が高くなるにつれてエッチングレートが急激に増大する硫酸過酸化水素水溶液は最適である。また他のエッチャントとしては水酸化アンモニウム過酸化水素水溶液などを用いても良い。
【００３９】
また、前記実施例ではＡｌＡｓ層の選択酸化の際、加熱する温度を４００℃とした場合について説明したが、これに限定されることなく、最終的な電流通路の大きさが所望の値となるよう制御できる条件であればよい。温度をあげると酸化速度が上昇し、短時間で所望の酸化領域を形成する事ができるが、４００℃程度がもっとも制御しやすい温度であった。
【００４０】
また、半導体柱形成のためのエッチングに際しては、ウエットエッチングの場合、上層と下層でエッチング液にさらされる時間が異なることから、半導体柱の底部に向かうにつれて面積が広がるいわゆるテーパ形状が形成され、直径の小さな半導体柱が作りにくいという問題があるが、ドライエッチングの場合、反応性イオンビームエッチング（ＲＩＢＥ）法や反応性イオンエッチング（ＲＩＥ）法を用いれば、半導体柱の側壁が、垂直あるいはアンダーカット形状をとるようにすることもでき、直径の小さな半導体柱も容易に形成することができる。このとき、エッチングガスとしてはＣｌ₂、ＢＣｌ₃、ＳｉＣｌ₄ あるいはＡｒとＣｌ₂の混合ガス等が用いられる。
【００４１】
このようにして作製された面発光型半導体レーザ素子の動作は、以下に示す如くである。ここで、量子井戸層に注入されたキャリアは電子−正孔再結合により光を放出し、この光は上部と下部の半導体多層反射膜によって反射され、利得が損失を上回ったところでレーザ発振を生ずる。レーザ光は基板表面に設けられた電極の窓部に設けられた第２の上部多層反射膜を介して出射されるが、この形状が長軸と短軸との比が５：１の矩形をなし、図３および図４に示すような偏平なビームを形成する。
【００４２】
次に本発明の第２の実施例の面発光型半導体レーザ素子およびその製造方法について、図面を参照しつつ説明する。
前記第１の実施例では、角柱状の光制御領域７の上面に突出するように第２の上部半導体多層反射膜５を形成したが、この例ではこの第２の上部半導体多層反射膜５ａの周りを選択的に酸化し第３の酸化膜５ｓを形成し、屈折率の異なる領域としたことを特徴とする。
【００４３】
この構造では、上記第１の実施例の効果に加え酸化されずに残る領域の大きさを調節することにより、出射ビームの形状を容易に調節することができるという効果を奏効する。
【００４４】
次に本発明の第３の実施例の面発光型半導体レーザ素子およびその製造方法について、図面を参照しつつ説明する。
【００４５】
前記第１および第２の実施例ではエッチングにより柱状の光制御領域を形成したが、この例では図６に示すように電流狭窄層１４はプロトン注入により矩形状の開口Ｈを残して形成され、さらにｐ型の上部半導体多層反射膜５の周りが亜鉛などのｐ型不純物を拡散して形成され、上部半導体多層反射膜５をこれとは屈折率の異なる不純物拡散領域１５で囲むように構成されている。この不純物拡散領域は電流注入層としての役割をも果たし、この上層にｐ側電極６が形成されている。
【００４６】
各層の状態および他の部分については、前記第１および第２の実施例と同様に形成されている。
【００４７】
この構造では、、上記第１の実施例の効果に加え、不純物書く山荘１５と光が導波する p型上部多層反射膜５との屈折率差をより小さくする事ができるため、より大きな径の出射ビームを容易に得ることができるという効果を奏効する。
【００４８】
このような面発光型半導体レーザ素子を図７に示すように、矩形状の発光パターンｐの短軸をｎの方向に揃うようにアレイ状に配列することによって面発光型半導体レーザ装置が形成される。
【００４９】
また図８に示すように、このような面発光型半導体レーザ素子を二次元に配列して２次元の面発光型半導体レーザ装置を形成することも可能である。この時最近接のパターンを結ぶ軸ｎおよびｍが所定の角度をなすように形成することにより、均一に光照射を行うことができるように、より密接して配列することができる。
【００５０】
次にこの面発光型半導体レーザ装置を、素子を１次元のアレイ状に配列したもので構成し、主走査拡大光学系、副走査拡大光学系を用いて感光体面上に投影する形態を図９に示す。この図から明らかなように面発光レーザアレイ１００で形成する発光パターンｐを楕円状にし、この発光パターンｐの偏平率（主走査方向長さ：ｐ１、副走査方向長さ：ｐ２）を、感光体１３面上で真円（主走査方向長さ：Ｌ１、副走査方向長さ：Ｌ２、Ｌ１＝Ｌ２）となるように、光学系の倍率の比に対応して決定している。ここでは発光パターンを長手方向に５μｍ、短手方向に１μｍの場合に、主走査方向光学系２１の倍率を５倍、副走査方向光学系２２の倍率を２５倍とし、ｐ１／ｐ２＝５とすることにより、投影面の感光体１３上でほぼ真円のビーム形状を得ることができるようになっている。
【００５１】
これにより焦点深度の異方性を最小にすることができ、位置合わせに要求される精度を抑え、感光体ドラムの偏心などの位置ずれにより、感光体面上に投影されるビーム径が変動を低減するのを防ぐことができる。
【００５２】
なお、本発明の構成要件を満足する範囲内で他の方法によっても実現可能であることはいうまでもない。
【００５３】
【発明の効果】
以上説明してきたように、本発明によれば、主走査方向に所定の倍率で拡大し、副走査方向にはそれ以下の倍率で拡大若しくは縮小した場合に、各方向の倍率に合わせて、感光体面上で、ビームが真円となるように、ビームを偏平形状にすることにより、焦点深度を大きとることができ、位置合わせに要求される精度を抑え、感光体ドラムの偏心などの位置ずれにより生じるビーム径の変動を小さくすることができる。
【００５４】
また、出射の偏波面を一方向に安定化させることが出来、これらの素子を同一基板上に集積化した際、すべての素子の偏波面をばらつきなく一方向に揃える事ができる。また注入電流を増加しても、光透過領域の形に比べて柱状の光制御領域の径を十分に大きくする事ができるため発熱を抑制し、広い出力範囲にわたって光出力特性を劣化させることなく偏波面を安定化することができる。
【図面の簡単な説明】
【図１】焦点位置からの位置ずれとビーム径の変化を示す図
【図２】本発明の第１の実施例の面発光型半導体レーザ素子を示す図
【図３】半導体多層反射膜の矩形形状が５：１である場合のビーム強度プロファイルの等高線を示す図
【図４】同ビーム強度プロアフィルの３次元表示を示す図
【図５】本発明の第２の実施例の面発光型半導体レーザ素子を示す図
【図６】本発明の第３の実施例の面発光型半導体レーザ素子を示す図
【図７】本発明の面発光型半導体レーザ素子を用いた１次元アレイの概念図
【図８】本発明の面発光型半導体レーザ素子を用いた２次元アレイの概念図
【図９】同半導体レーザ装置におけるビームの主走査方向および副走査方向での投影状態を示す図
【符号の説明】
１ｎ型ガリウムひ素（ＧａＡｓ）基板
２ｎ型下部半導体多層反射膜
３量子井戸活性層
４電流狭窄層
５ｐ型上部半導体多層反射膜
６ｐ側電極
７光制御領域
８第２のｐ型上部半導体多層反射膜
９第１の絶縁層
１０第２の絶縁層
１３感光体
２１主走査拡大走査系
２２副走査拡大走査系
１００面発光型半導体レーザアレイ面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface emitting semiconductor laser element, a surface emitting semiconductor laser array, a surface emitting semiconductor laser beam scanner, a surface emitting laser beam recording apparatus, and a laser recording method.
[0002]
[Prior art]
As a conventional surface emitting laser array, for example, there is one that projects onto an image plane using a set of lens systems. However, when projected onto the photosensitive member at the same magnification in the main scanning and sub-scanning directions, particularly when projected onto a small-diameter drum, the projected image surface is a flat surface, whereas the photosensitive drum surface has a certain curvature. It has a cylindrical surface. For this reason, a focus position shift occurs in the sub-scanning direction in which the photosensitive drum surface has a curvature. In order to solve this problem, a method has been proposed in which the magnification in the sub-scanning direction is set lower than that in the main scanning direction to adjust the image size and reduce the focal position shift (Japanese Patent Application No. 8-8878). issue).
[0003]
[Problems to be solved by the invention]
However, when a normal circular surface emitting laser is used and enlarged at a predetermined magnification in the main scanning direction and enlarged or reduced at a smaller magnification in the sub scanning direction, it is projected onto the photosensitive surface. The beam diameter in the sub scanning direction is smaller than the beam diameter in the main scanning direction. As a result, the focal depth in the sub-scanning direction is shallower than the focal depth in the main scanning direction, and high accuracy is required for alignment. In addition, there is a problem that the beam diameter projected onto the photoconductor varies greatly due to the positional deviation caused by the eccentricity of the photoconductor drum.
[0004]
FIG. 1 shows the relationship between the displacement from the focal position (beam waist) and the change in beam diameter. For example, a beam narrowed to 21 μm at a focal position having a Gaussian intensity profile with a wavelength of 780 nm has a beam diameter of about 24 μm at most even when the deviation from the focal position is 1 mm. On the other hand, a beam focused to 5 μm at a focal position having a Gaussian intensity profile with a wavelength of 780 nm has a beam diameter of 40 μm or more when the deviation from the focal position is 1 mm, and is sensitive to positional fluctuations. is there.
[0005]
On the other hand, in the case of an element structure in which edge-emitting lasers are arranged on a substrate and emitted in a direction perpendicular to the substrate using a mirror on the substrate, as in JP-A-2-290091, for example, When a beam is obtained, and the magnification of the lens diameter in the main scanning direction and the sub scanning direction and the element structure are selected in an appropriate relationship, the projected beam diameter can be the same in the main scanning direction and the sub scanning direction. , The depth of focus can be increased.
[0006]
However, in the case of an element structure in which edge-emitting lasers are arranged on a substrate and emitted in a direction perpendicular to the substrate using a mirror on the substrate, the density for integrating the elements cannot be increased, and the laser spot is There is a problem in that it cannot be formed on the photosensitive member with high precision and high density.
[0007]
The present invention has been made in view of the above-described circumstances. The beam diameter on the projection surface is close to a perfect circle, the focal depth can be increased, and the accuracy restriction required for alignment is reduced. Another object of the present invention is to provide a surface emitting semiconductor laser capable of reducing fluctuations in the beam diameter projected onto the surface of the photosensitive member due to the eccentricity of the photosensitive drum.
[0008]
[Means for Solving the Problems]
Therefore, in the present invention, the beam generated from the surface-emitting type semiconductor laser element has a predetermined magnification in one direction perpendicular to the optical axis, and the other is perpendicular to the optical axis. When a spot is formed on a photoconductor using a projection optical system that expands or contracts at different magnifications, light emission with a flat rate corresponding to the magnification of the optical system is made so that the spot system on the photoconductor is close to a perfect circle. A surface emitting laser element having a pattern is formed. For example, when a 21 μm round spot is obtained on the surface of the photoconductor, the light emission of the surface emitting semiconductor laser element is obtained when the magnification of the optical system is 7 times in the main scanning direction and 2 times in the sub scanning direction. The beam shape is adjusted in accordance with the magnification in the main scanning direction and the sub-scanning direction so that elements having a beam diameter of 3 μm and 10.5 μm are prepared in each direction. In a normal vertical cavity surface emitting semiconductor laser, the light emission pattern is almost a perfect circle. This is because the laser structure is formed in a substantially symmetrical shape within the substrate surface. Therefore, the light emission pattern can be made flat by making the resonator structure constituting the laser asymmetrical in the substrate plane. Further, when the surface emitting semiconductor laser is arrayed in a one-dimensional or two-dimensional array, if the directions of the asymmetrical light emitting patterns of the surface emitting semiconductor laser are uniform, all the spots on the photoconductor. The spot diameter can be made close to a perfect circle.
[0009]
That is, the first feature of the present invention is that a vertical cavity surface emitting semiconductor laser in which an active layer is sandwiched between upper and lower semiconductor multilayer reflective films on a semiconductor substrate and emits light in a direction perpendicular to the substrate. In the element, at least one of the upper and lower semiconductor multilayer reflective films is configured to be longer than the other direction in one direction in the substrate surface, and provided on the upper semiconductor multilayer reflective film, The columnar second semiconductor multilayer reflective film through which the emitted laser beam oscillated from the upper or lower semiconductor multilayer reflective film passes , and the second semiconductor multilayer reflective film by a material lower than the effective refractive index of the second semiconductor multilayer reflective film. A layer formed around the semiconductor multilayer reflective film, and the intensity pattern of the emitted light beam emitted through the second semiconductor multilayer reflective film is configured to have directionality. Located in.
[0010]
A second feature of the present invention is a vertical cavity surface emitting semiconductor laser device in which an active layer is sandwiched between upper and lower semiconductor multilayer reflective films on a semiconductor substrate and emits light in a direction perpendicular to the substrate. The active layer is configured to be longer in one direction in the substrate surface than the other direction , and is provided on the upper semiconductor multilayer reflective film, and laser is emitted from the upper or lower semiconductor multilayer reflective film. A columnar second semiconductor multilayer reflective film through which the oscillated emission beam passes and a material lower than the effective refractive index of the second semiconductor multilayer reflective film are formed around the second semiconductor multilayer reflective film And the intensity pattern of the emitted light beam emitted through the second semiconductor multilayer reflective film has a directivity.
[0011]
A third feature of the present invention is a vertical cavity surface emitting semiconductor laser device in which an active layer is sandwiched between upper and lower semiconductor multilayer reflective films on a semiconductor substrate and emits light in a direction perpendicular to the substrate. The current confinement region provided outside or between the upper and lower semiconductor multilayer reflective films and between the active layer and the active layer is configured to be longer in one direction in the substrate surface than in the other direction, The intensity pattern is configured to have directionality.
[0012]
Preferably, the current confinement region is made of AlAs oxide.
[0013]
According to a fourth aspect of the present invention, there is provided a vertical cavity surface emitting semiconductor laser device in which an active layer is sandwiched between upper and lower semiconductor multilayer reflective films on a semiconductor substrate and emits light in a direction perpendicular to the substrate. In the surface-emitting type semiconductor laser array arranged in an array on the substrate surface, the surface-emitting type semiconductor laser element is provided on the upper semiconductor multilayer reflective film, and the upper or lower semiconductor multilayer reflective film is provided. A columnar second semiconductor multilayer reflective film through which an emission beam laser-oscillated from the film passes, and a material lower than the effective refractive index of the second semiconductor multilayer reflective film are formed around the second semiconductor multilayer reflective film. And an intensity pattern of the emitted light beam emitted through the second semiconductor multilayer reflective film has a directivity.
[0014]
According to a fifth aspect of the present invention, there is provided a laser light source, a first lens system that expands a beam emitted from the laser light source at a first magnification in the main scanning direction, and magnification at a second magnification in the sub-scanning direction. Or a second lens system to be reduced, and a drive scanning system that drives and scans a beam from the laser light source and guides the beam onto a scanning surface via the first and second lens systems. In accordance with the first and second magnifications, the vertical cavity surface emitting device is configured such that the intensity pattern of the light emission beam of the element has directionality so that the beam is substantially circular on the scanning plane. The present invention resides in a surface-emitting type semiconductor laser device in which a plurality of type semiconductor laser elements are arranged in an array on the substrate surface.
[0015]
A sixth feature of the present invention is a laser light source, a first lens system that expands a beam emitted from the laser light source at a first magnification in the main scanning direction, and a magnification at a second magnification in the sub-scanning direction. Alternatively, a second lens system to be reduced, a photoconductor that is exposed to a beam to form an electrostatic latent image, and a beam from the laser light source is driven and scanned, and the photoconductor surface is passed through the first and second lens systems. A driving scanning system that leads upward, and a recording unit that performs image recording based on the electrostatic latent image, wherein the laser light source is adjusted to the first and second magnifications, and the beam is on the scanning surface. A plurality of vertical cavity surface emitting semiconductor laser elements configured so that the intensity pattern of the emitted light beam of the element has directionality so as to be substantially circular are arranged in an array on the substrate surface. It is composed of a surface emitting semiconductor laser device Lies in the fact.
[0016]
The seventh feature of the present invention is that the laser light emitted from the laser light source is supplied through the first lens system and the second lens system at the first and second magnifications in the main scanning direction and the sub scanning direction, respectively. Enlarging / reducing, driving and scanning this to form an electrostatic latent image on the surface of the photoreceptor, and a recording step of executing image recording based on the electrostatic latent image, wherein the laser light source includes A vertical cavity surface emitting type configured such that the intensity pattern of the light emitting beam of the element has directionality so that the beam is substantially circular on the scanning plane in accordance with the first and second magnifications. The semiconductor laser device is composed of a surface emitting semiconductor laser device in which a plurality of semiconductor laser elements are arranged in an array on the substrate surface.
[0018]
According to the present invention, a beam emitted from a surface-emitting type semiconductor laser has a predetermined magnification in one direction perpendicular to the optical axis and a different magnification in the other direction perpendicular to the optical axis. When the light beam is guided onto the photoconductor by using a projection optical system that is enlarged or reduced by the beam diameter, the beam diameter in each direction is adjusted to correspond to these magnifications so as to be almost a perfect circle on the photoconductor. The depth can be increased, and the accuracy restriction required for alignment can be reduced. Therefore, even when the photosensitive drum is eccentric, fluctuations in the beam diameter can be suppressed.
[0019]
Therefore, when recording is performed using this surface emitting semiconductor laser element, it is possible to perform highly accurate and reliable recording.
[0020]
【Example】
The present invention will be described below with reference to the drawings.
[0021]
2A and 2B are a top view and a cross-sectional view of the surface emitting semiconductor laser device according to the first embodiment of the present invention.
[0022]
The surface-emitting type semiconductor laser device includes an n-type Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As lower semiconductor multilayer reflective film 2 (multi-diffractive Bragg reflector (DBR)) formed on an n-type gallium arsenide (GaAs) substrate 1. ), And the quantum well active layer 3 formed on this with an undoped Al _0.11 Ga _0.89 quantum well layer and an undoped Al _0.3 Ga _0.7 As barrier layer, and formed by oxidation of AlAs, and has an opening in the center. A current confinement layer 4, a p-type Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As upper semiconductor multilayer reflective film 5, a p-type GaAs contact layer (not shown), and a p-type electrode 6 are sequentially laminated to obtain a current. Etching is removed to the depth at which the side surface of the constriction layer 4 is exposed, except for the light emitting region and its periphery, and a prismatic light control region 7 is formed. A current confinement layer formed by oxidizing the AlAs layer is formed in the lowermost layer of the reflective film 5 except for the central opening, and a current does not flow in the deposition direction in a region other than the opening. Note that a separation layer s made of Al _0.11 Ga _0.89 As is interposed between the quantum well active layer 3 and the current confinement layer 4 in order to protect the intrusion of impurities into the quantum well active layer 3. Yes.
[0023]
A second opening is formed in the center of the p-type electrode 6 so as to include the upper part of the opening of the current confinement layer, and the second upper multilayer reflective film 8 is formed in a column shape on the upper semiconductor multilayer reflective film 5 from the opening. It is formed so as to project.
[0024]
Further, the light control region is covered with a first insulating film 9 made of silicon nitride at least partway along the upper multilayer reflective film 5, and the upper layer is made of silicon oxide up to the height of the second upper multilayer reflective film 8. A second insulating film 10 is formed, and a difference in refractive index is provided between the columnar portion of the second upper multilayer reflective film 8 and the periphery thereof. As shown in FIGS. According to the shape of the upper multilayer reflective film 8, an elliptical beam profile flattened in the lateral direction is formed. Here, the second upper multilayer reflective film 8 has a rectangular shape of 5: 1, FIG. 3 shows the contour lines of the beam intensity profile at this time, and FIG. 4 shows this three-dimensionally displayed. .
[0025]
An n-side electrode (not shown) made of Au—Ge / Au is formed on the back surface of the substrate.
[0026]
Here, the n-type lower semiconductor multilayer reflective film 2 has an n-type Al _0.9 Ga _0.1 As layer and an n-type Al _0.7 Ga _0.3 AsGaAs layer each having a film thickness λ / (4nr) (λ: oscillation wavelength, n _r : refractive index). The silicon concentration of the n-type impurity is 2 × 10 ¹⁸ cm ⁻³ . The quantum well active layer 4 is a combination of an undoped Al _0.11 Ga _0.89 quantum well layer (film thickness 8 nm × 3) and an undoped Al _0.3 Ga _0.7 As barrier layer (film thickness 5 nm × 4). The upper semiconductor multilayer reflective film 7 has a p-type Al _0.9 Ga _0.1 As layer and a p-type Al _0.7 Ga _0.3 AsGaAs layer each having a film thickness λ / (4n _r ) (λ: oscillation wavelength, n _r : refractive index) The carbon concentration, which is a p-type impurity, is 3 × 10 ¹⁸ cm ⁻³ . Finally, the second upper semiconductor multilayer reflective film 8 is undoped. The type of dopant is not limited to that used here, but selenium can be used for n-type, and zinc or magnesium can be used for p-type.
[0027]
In the above embodiment, the current confinement is performed by forming the oxide film from the side surface of the columnar region by selectively oxidizing the AlAs layer. However, the air gap may be formed by selective etching. The shape of the opening surrounded by the current confinement layer may be a perfect circle or a square symmetric structure, or may be an asymmetric structure such as an ellipse or a rectangle.
[0028]
Here, the laser light having an oscillation wavelength λ of 780 nm is designed to be extracted.
[0029]
According to this configuration, the carrier passage path in the prismatic light control region 7 is narrowed from the two symmetry plane directions of the opening of the current confinement layer 4 and the light is confined. In addition, since a difference in refractive index is caused between the second upper semiconductor multilayer reflective film 8 and the second insulating layer 10 around the second upper semiconductor multilayer reflective film 8, an elliptical beam profile that is flattened toward the symmetrical plane with a smaller refractive index difference. It becomes.
This also stabilizes the plane of polarization of the outgoing light in this direction.
[0030]
Next, the manufacturing process of this surface emitting semiconductor laser device will be described.
[0031]
First, as shown in FIG. 2, an n-type Al _0.9 Ga _0.1 As / Al _0.7 Ga _0.3 As lower semiconductor is formed on an n-type gallium arsenide (GaAs) (100) substrate 1 by metal organic chemical vapor deposition (MOCVD). A multilayer reflective film 3; a quantum well active layer 3 comprising an undoped Al _0.11 Ga _0.89 quantum well layer and an undoped Al _0.3 Ga _0.7 As barrier layer; a separation layer S comprising an Al _0.11 Ga _0.89 As layer; an AlAs layer; A p-type Al _0.9 Ga _0.1 As / Al _0.7 Ga _0.3 As upper semiconductor multilayer reflective film 5 and a p-type GaAs contact layer (not shown) are sequentially stacked.
Then, the substrate is taken out of the growth chamber, an insulating film such as a silicon oxide film is formed, and the semiconductor layer is etched away to a depth at which the AlAs layer can be exposed by reactive ion etching using SiCl ₄ gas using photolithography technology. Then, the light control region 7 made of a prismatic semiconductor pillar is formed.
[0032]
Subsequently, the substrate is heated to 400 ° C. in a quartz tube filled with high-temperature water vapor, and the exposed AlAs layer is gradually oxidized from the outer cross section by performing a heat treatment for about 10 minutes to form an oxide film. In the end, the region that remains without being oxidized becomes a rectangular shape. Here, instead of oxidation by heat treatment, it may be soaked in a sulfuric acid hydrogen peroxide solution (H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 1: 1: 5) for about 30 seconds, Thereby, the AlAs layer is selectively removed from the outer cross section by so-called side etching.
[0033]
Thereafter, the first insulating layer 9 made of a silicon nitride layer is formed while leaving the resist mask on the surface, and the first insulating layer on the upper surface of the columnar region is removed by lift-off and silicon oxide is removed by selective etching. .
[0034]
Thereafter, an annular p-side electrode 6 is formed so as to cover the periphery of the light control region 7 by using a vapor deposition method and a photolithography technique. The second upper semiconductor multilayer reflective film 8 is formed while leaving the resist used for patterning the central p-side electrode, and the film other than the opening is removed together with the resist by lift-off to form a columnar region.
[0035]
Finally, a second insulating layer 10 made of a silicon oxide layer is formed so as to cover the whole, and an n-side electrode is formed on the entire back surface of the substrate, so that the first according to the present invention shown in FIG. The surface emitting semiconductor laser device of the example is completed.
[0036]
In the above embodiment, each semiconductor layer is formed by metal organic vapor phase epitaxy, but the present invention is not limited to this, and molecular beam epitaxy (MBE) may be used.
[0037]
Further, the insulating film used as a mask for forming the semiconductor pillar is not limited to the silicon oxide film, and other materials such as a silicon nitride film may be used.
[0038]
Furthermore, in the above embodiment, an aqueous solution of hydrogen peroxide sulfate is used for the etching for selectively removing the AlAs layer, but it is desirable that the etching rate has a high selectivity with respect to the Al composition ratio, and as the Al composition ratio increases. An aqueous solution of sulfuric acid and hydrogen peroxide whose etching rate increases rapidly is optimal. Further, as another etchant, an ammonium hydroxide hydrogen peroxide aqueous solution or the like may be used.
[0039]
In the above embodiment, the case where the heating temperature is set to 400 ° C. during the selective oxidation of the AlAs layer has been described. However, the present invention is not limited to this, and the final current path has a desired value. Any controllable conditions may be used. When the temperature is raised, the oxidation rate increases, and a desired oxidation region can be formed in a short time. However, a temperature of about 400 ° C. is the easiest to control.
[0040]
In addition, in the etching for forming the semiconductor pillar, in the case of wet etching, since the time of exposure to the etching solution is different between the upper layer and the lower layer, a so-called taper shape is formed in which the area increases toward the bottom of the semiconductor pillar, and the diameter is increased. However, in the case of dry etching, if the reactive ion beam etching (RIBE) method or the reactive ion etching (RIE) method is used, the side wall of the semiconductor column is vertical or undercut. A shape can be taken, and a semiconductor pillar with a small diameter can also be formed easily. At this time, Cl ₂ , BCl ₃ , SiCl ₄ or a mixed gas of Ar and Cl ₂ is used as an etching gas.
[0041]
The operation of the surface-emitting type semiconductor laser device thus manufactured is as follows. Here, the carriers injected into the quantum well layer emit light by electron-hole recombination, and this light is reflected by the upper and lower semiconductor multilayer reflection films, and laser oscillation occurs when the gain exceeds the loss. . The laser light is emitted through the second upper multilayer reflective film provided in the window portion of the electrode provided on the substrate surface. This shape is a rectangle having a major axis / minor axis ratio of 5: 1. None, a flat beam as shown in FIGS. 3 and 4 is formed.
[0042]
Next, a surface-emitting type semiconductor laser device according to a second embodiment of the present invention and a method for manufacturing the same will be described with reference to the drawings.
In the first embodiment, the second upper semiconductor multilayer reflective film 5 is formed so as to protrude from the upper surface of the prismatic light control region 7. In this example, the second upper semiconductor multilayer reflective film 5 a The area is selectively oxidized to form a third oxide film 5s, which is a region having a different refractive index.
[0043]
In this structure, in addition to the effect of the first embodiment, the size of the exit beam can be easily adjusted by adjusting the size of the region that remains without being oxidized.
[0044]
Next, a surface-emitting type semiconductor laser device according to a third embodiment of the present invention and a method for manufacturing the same will be described with reference to the drawings.
[0045]
In the first and second embodiments, the columnar light control region is formed by etching. In this example, as shown in FIG. 6, the current confinement layer 14 is formed leaving a rectangular opening H by proton implantation. Further, the p-type upper semiconductor multilayer reflective film 5 is formed by diffusing a p-type impurity such as zinc, and the upper semiconductor multilayer reflective film 5 is surrounded by an impurity diffusion region 15 having a refractive index different from that of the upper semiconductor multilayer reflective film 5. ing. This impurity diffusion region also serves as a current injection layer, and the p-side electrode 6 is formed in the upper layer.
[0046]
The state of each layer and other portions are formed in the same manner as in the first and second embodiments.
[0047]
In this structure, in addition to the effects of the first embodiment, the refractive index difference between the mountain villa 15 where impurities are written and the p-type upper multilayer reflective film 5 where light is guided can be made smaller. The effect that the outgoing beam can be easily obtained is obtained.
[0048]
As shown in FIG. 7, a surface emitting semiconductor laser device is formed by arranging such surface emitting semiconductor laser elements in an array so that the short axes of rectangular light emitting patterns p are aligned in the direction of n. The
[0049]
As shown in FIG. 8, it is also possible to form a two-dimensional surface-emitting semiconductor laser device by arranging such surface-emitting semiconductor laser elements two-dimensionally. At this time, by forming the axes n and m connecting the closest patterns so as to form a predetermined angle, they can be arranged more closely so that uniform light irradiation can be performed.
[0050]
Next, this surface-emitting type semiconductor laser device is composed of elements arranged in a one-dimensional array, and is projected onto the photoreceptor surface using the main scanning magnification optical system and sub-scanning magnification optical system. Shown in As is apparent from this figure, the light emission pattern p formed by the surface emitting laser array 100 is made elliptical, and the flatness ratio (length in the main scanning direction: p1, length in the sub scanning direction: p2) of the light emission pattern p is determined in a photosensitive manner. It is determined corresponding to the magnification ratio of the optical system so as to be a perfect circle (length in the main scanning direction: L1, sub-scanning direction length: L2, L1 = L2) on the surface of the body 13. Here, when the light emission pattern is 5 μm in the longitudinal direction and 1 μm in the lateral direction, the magnification of the main scanning direction optical system 21 is 5 times, the magnification of the sub-scanning direction optical system 22 is 25 times, and p1 / p2 = 5 By doing so, a substantially perfect beam shape can be obtained on the photosensitive member 13 on the projection surface.
[0051]
This minimizes the anisotropy of the depth of focus, reduces the accuracy required for alignment, and reduces fluctuations in the beam diameter projected onto the photoreceptor surface due to misalignment such as the eccentricity of the photoreceptor drum. Can be prevented.
[0052]
Needless to say, the present invention can be realized by other methods as long as the constituent requirements of the present invention are satisfied.
[0053]
【The invention's effect】
As described above, according to the present invention, when magnification is performed at a predetermined magnification in the main scanning direction and magnification or reduction is performed at a magnification smaller than that in the sub-scanning direction, the sensitivity is adjusted in accordance with the magnification in each direction. By making the beam flat so that the beam becomes a perfect circle on the body surface, the depth of focus can be increased, the accuracy required for alignment is suppressed, and positional deviations such as eccentricity of the photosensitive drum The variation in beam diameter caused by the above can be reduced.
[0054]
In addition, the polarization plane of emission can be stabilized in one direction. When these elements are integrated on the same substrate, the polarization planes of all elements can be aligned in one direction without variation. Even if the injection current is increased, the diameter of the columnar light control region can be made sufficiently large compared to the shape of the light transmission region, so heat generation is suppressed and the light output characteristics are not deteriorated over a wide output range. The polarization plane can be stabilized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a positional deviation from a focal position and a change in beam diameter. FIG. 2 is a diagram showing a surface emitting semiconductor laser device according to a first embodiment of the invention. FIG. 4 is a diagram showing a contour line of a beam intensity profile when the shape is 5: 1. FIG. 4 is a diagram showing a three-dimensional display of the beam intensity profile. FIG. 5 is a surface emitting semiconductor laser according to a second embodiment of the invention. FIG. 6 is a diagram showing a surface emitting semiconductor laser element according to a third embodiment of the present invention. FIG. 7 is a conceptual diagram of a one-dimensional array using the surface emitting semiconductor laser element according to the present invention. 8 is a conceptual diagram of a two-dimensional array using the surface emitting semiconductor laser element of the present invention. FIG. 9 is a diagram showing a projection state of a beam in the main scanning direction and sub-scanning direction in the semiconductor laser device.
1 n-type gallium arsenide (GaAs) substrate 2 n-type lower semiconductor multilayer reflective film 3 quantum well active layer 4 current confinement layer 5 p-type upper semiconductor multilayer reflective film 6 p-side electrode 7 light control region 8 second p-type upper semiconductor Multilayer reflective film 9 First insulating layer 10 Second insulating layer 13 Photoconductor 21 Main scanning enlarged scanning system 22 Sub-scanning enlarged scanning system 100 Surface emitting semiconductor laser array surface

Claims

In a vertical cavity surface emitting semiconductor laser device in which an active layer is sandwiched between upper and lower semiconductor multilayer reflective films on a semiconductor substrate and emits light in a direction perpendicular to the substrate,
At least one of the upper and lower semiconductor multilayer reflective films is configured to be longer than the other direction in one direction within the substrate surface,
A columnar second semiconductor multilayer reflective film that is provided on the upper semiconductor multilayer reflective film and through which a light-emitting beam laser-oscillated from the upper or lower semiconductor multilayer reflective film passes;
A layer formed around the second semiconductor multilayer reflective film with a material lower than the effective refractive index of the second semiconductor multilayer reflective film;
A surface-emitting type semiconductor laser device, characterized in that an intensity pattern of the emitted light beam emitted through the second semiconductor multilayer reflective film has directionality.

In a vertical cavity surface emitting semiconductor laser device in which an active layer is sandwiched between upper and lower semiconductor multilayer reflective films on a semiconductor substrate and emits light in a direction perpendicular to the substrate,
The active layer is configured to be longer than the other direction in one direction in the substrate surface,
A columnar second semiconductor multilayer reflective film that is provided on the upper semiconductor multilayer reflective film and through which a light-emitting beam laser-oscillated from the upper or lower semiconductor multilayer reflective film passes;
A layer formed around the second semiconductor multilayer reflective film with a material lower than the effective refractive index of the second semiconductor multilayer reflective film;
A surface-emitting type semiconductor laser device, characterized in that an intensity pattern of the emitted light beam emitted through the second semiconductor multilayer reflective film has directionality.

In a vertical cavity surface emitting semiconductor laser device in which an active layer is sandwiched between upper and lower semiconductor multilayer reflective films on a semiconductor substrate and emits light in a direction perpendicular to the substrate,
The current confinement region provided between the active layer and the outer side of the upper and lower semiconductor multilayer reflective films is configured to be longer than the other direction in one direction within the substrate surface,
A surface-emitting type semiconductor laser device characterized in that an intensity pattern of a light-emitting beam has a directivity.

4. The surface emitting semiconductor laser device according to claim 3, wherein the current confinement region is made of an AlAs oxide.

On the semiconductor substrate, an active layer is sandwiched between upper and lower semiconductor multilayer reflective films, and a plurality of vertical cavity surface emitting semiconductor laser elements that emit light in a direction perpendicular to the substrate are arrayed within the substrate surface. In the surface emitting semiconductor laser array arranged individually,
The surface emitting semiconductor laser element is
A columnar second semiconductor multilayer reflective film that is provided on the upper semiconductor multilayer reflective film and through which a light-emitting beam laser-oscillated from the upper or lower semiconductor multilayer reflective film passes;
A layer formed around the second semiconductor multilayer reflective film with a material lower than the effective refractive index of the second semiconductor multilayer reflective film;
A surface-emitting type semiconductor laser array, wherein an intensity pattern of the emitted light beam emitted through the second semiconductor multilayer reflective film has a directionality.

A laser light source;
A first lens system for enlarging a beam emitted from the laser light source at a first magnification in the main scanning direction; and a second lens system for enlarging or reducing at a second magnification in the sub-scanning direction;
A drive scanning system that drives and scans the beam from the laser light source and guides the beam onto a scanning surface via the first and second lens systems;
A vertical resonator in which the intensity pattern of the emitted light beam of the element has directionality so that the laser light source matches the first and second magnifications, and the beam is almost a circle on the scanning plane. A surface-emitting type semiconductor laser beam scanner comprising a surface-emitting type semiconductor laser device in which a plurality of surface-emitting type semiconductor laser elements are arranged in an array on a substrate surface.

A laser light source;
A first lens system for enlarging a beam emitted from the laser light source at a first magnification in the main scanning direction; and a second lens system for enlarging or reducing at a second magnification in the sub-scanning direction;
A photosensitive member that is exposed to light to form an electrostatic latent image;
A drive scanning system that drives and scans the beam from the laser light source and guides the beam onto the surface of the photoreceptor through the first and second lens systems;
Recording means for executing image recording based on the electrostatic latent image,
A vertical resonator in which the intensity pattern of the emitted light beam of the element has directionality so that the laser light source matches the first and second magnifications, and the beam is almost a circle on the scanning plane. A surface-emitting laser beam recording apparatus comprising a surface-emitting type semiconductor laser device in which a plurality of surface-emitting type semiconductor laser elements are arranged in an array on a substrate surface.

The laser light emitted from the laser light source is enlarged / reduced at the first and second magnifications in the main scanning direction and the sub-scanning direction through the first lens system and the second lens system, respectively, and driven and scanned. Forming an electrostatic latent image on the photoreceptor surface;
A recording step of performing image recording based on the electrostatic latent image,
Vertical resonance in which the laser light source is configured so that the intensity pattern of the emitted light beam of the element has directionality so that the beam is substantially a circle on the scanning surface in accordance with the first and second magnifications. A laser recording method comprising a surface-emitting type semiconductor laser device in which a plurality of surface-emitting type semiconductor laser elements are arranged in an array on a substrate surface.