JP2007334975A - Diffraction grating, its manufacturing method, and optical pickup device - Google Patents

Diffraction grating, its manufacturing method, and optical pickup device Download PDF

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Publication number
JP2007334975A
JP2007334975A JP2006164361A JP2006164361A JP2007334975A JP 2007334975 A JP2007334975 A JP 2007334975A JP 2006164361 A JP2006164361 A JP 2006164361A JP 2006164361 A JP2006164361 A JP 2006164361A JP 2007334975 A JP2007334975 A JP 2007334975A
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Prior art keywords
refractive index
index material
diffraction grating
wavelength
diffraction
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Japanese (ja)
Inventor
Masayuki Oto
正之 大戸
Kiyokazu Yoshida
清和 吉田
Kazuyuki Nakasendou
和之 中仙道
Hiroshi Okamoto
弘志 岡本
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Miyazaki Epson Corp
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Miyazaki Epson Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffraction grating capable of suppressing a light quantity loss. <P>SOLUTION: The diffraction grating is provided with first and second diffraction grating parts 5 and 6 which are formed on both surfaces of a glass transparent substrate 2 respectively and have a low refractive index material 3, a high refractive index material 4 and a photosensitive layer 7 formed on the high refractive index material 4 and wherein the low refractive index material 3 and the high refractive index material 4 are alternately disposed. In the first diffraction grating part 5, grating depths of the low refractive index material 3 and the high refractive index material 4 are set so that the diffraction efficiency to light having wavelength λ<SB>1</SB>has a prescribed value and phase difference of the low refractive index material 3 and the high refractive index material 4 to light having wavelength λ<SB>2</SB>is 2π. In the second diffraction grating part 6, the grating depths of the low refractive index material 3 and the high refractive index material 4 are set so that the diffraction efficiency to light having wavelength λ<SB>2</SB>has a prescribed value and phase difference of the low refractive index material 3 and the high refractive index material 4 to light having wavelength λ<SB>1</SB>is 2π. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、波長が異なる複数の光を回折可能な回折格子とその製造方法、及び回折格子
を備えた光ピックアップ装置に関するものである。 The present invention relates to a diffraction grating capable of diffracting a plurality of lights having different wavelengths, a manufacturing method thereof, and an optical pickup device including the diffraction grating.

透過型回折素子は透明ガラス、透明結晶板、或いは透明樹脂板等の透明なウェーハ表面
に透明な材質にて凹凸部を形成し、凹凸部の位相差により回折光を発生させる光学素子（
回折格子＝グレーティング）である。従来の透過型回折素子は、例えば透明なガラス板、
結晶板、或いは樹脂板等から成る透明ウェーハ上にフォトレジスト膜を形成し、このレジ
スト膜を所定の周期格子マスクを用いて露光してから露光部を現像により除去するフォト
リソグラフィ技術にて凹凸の格子状パターンを形成していた。また、透明ウェーハ上にＳ
ｉＯ2などの誘電体膜をコーティングしてから、所定の周期格子マスクを用いて誘電体膜
を、フォトリソグラフィ技術を用いて露光、現像することにより凹凸の格子状パターンを
形成する方法もある。
近年、ＣＤ（Compact Disc）やＤＶＤ（Digital Versatile Disc）といった異なる種類
の光記録媒体（以下、光ディスクと称す）から情報を再生したり、或いは情報を記録した
りする光ピックアップ装置が開発されている。
上記のような光ピックアップ装置においては、レーザ光を集光させたレーザスポットが
光ディスクの情報記録面に形成されているトラックを追従するようトラッキング制御が行
われている。トラッキング制御方法としては、３ビーム法や差動プッシュプル法が広く利
用され、これら３ビーム法や差動プッシュプル法では、レーザ光源からの１つのレーザ光
を３ビーム化するために回折格子が用いられている。
また、近年、光ピックアップ装置の小型化、及び低コスト化を図るために、例えば、Ｄ
ＶＤ用の波長帯（６５０ｎｍ）のレーザ光を出射する半導体レーザと、ＣＤ用の波長帯（
７８５ｎｍ）のレーザ光を出射する半導体レーザとを１つのチップ内に形成した所謂モノ
リシック集積型の２波長レーザ光源が実用化されている。
しかしながら、例えばＣＤとＤＶＤは記録フォーマットが異なるため、回折格子の回折
光は夫々適切な角度で分離（回折）する必要があるが、従来の回折格子は単一の凹凸で形
成されているため、夫々の分離角度を制御できない問題があった。 A transmissive diffractive element is an optical element that forms a concavo-convex portion with a transparent material on a transparent wafer surface such as a transparent glass, a transparent crystal plate, or a transparent resin plate, and generates diffracted light by the phase difference of the concavo-convex portion
(Diffraction grating = grating). Conventional transmission diffraction elements are, for example, transparent glass plates,
A photoresist film is formed on a transparent wafer made of a crystal plate or a resin plate, and the resist film is exposed using a predetermined periodic lattice mask, and then the exposed portion is removed by development. A lattice pattern was formed. In addition, S on the transparent wafer
There is also a method of forming an uneven lattice pattern by coating a dielectric film such as iO 2 and then exposing and developing the dielectric film using a predetermined periodic lattice mask using a photolithography technique.
2. Description of the Related Art In recent years, optical pickup apparatuses that reproduce information from or record information on different types of optical recording media (hereinafter referred to as optical disks) such as CD (Compact Disc) and DVD (Digital Versatile Disc) have been developed. .
In the optical pickup device as described above, tracking control is performed so that the laser spot on which the laser beam is focused follows the track formed on the information recording surface of the optical disc. As a tracking control method, a three-beam method or a differential push-pull method is widely used. In the three-beam method or the differential push-pull method, a diffraction grating is used to convert one laser beam from a laser light source into three beams. It is used.
In recent years, in order to reduce the size and cost of an optical pickup device, for example, D
A semiconductor laser that emits laser light in the VD wavelength band (650 nm), and a CD wavelength band (
A so-called monolithic integrated type two-wavelength laser light source in which a semiconductor laser emitting a laser beam of 785 nm) is formed in one chip has been put into practical use.
However, for example, CD and DVD have different recording formats, so the diffracted light of the diffraction grating needs to be separated (diffracted) at an appropriate angle, but the conventional diffraction grating is formed with a single concavo-convex, There was a problem that each separation angle could not be controlled.

そこで、２つの異なる波長のレーザ光を回折可能な回折格子が提案されている。例えば
、特許文献１には、断面形状が凹凸状で、格子の凸部の幅と格子周期との比を０．５以外
の値に設定し、凸部と凹部との透過光の位相差が一方の波長の光に対して２πであり、他
方の波長の光に対して０次回折効率が所定の値に調整されている回折格子を、透光性基板
上の夫々の面に形成した２波長対応の回折格子が開示されている。 Therefore, a diffraction grating capable of diffracting two different wavelengths of laser light has been proposed. For example, in Patent Document 1, the cross-sectional shape is uneven, the ratio of the width of the convex portion of the grating to the grating period is set to a value other than 0.5, and the phase difference of the transmitted light between the convex portion and the concave portion is Diffraction gratings having 2π for light of one wavelength and zero-order diffraction efficiency adjusted to a predetermined value for light of the other wavelength are formed on respective surfaces on the translucent substrate. A wavelength compatible diffraction grating is disclosed.

図１２は、特許文献１に開示されている従来の２波長対応回折格子の構造を模式的に示
した図である。なお、図１２においては、説明を分かり易くするために波長λ1と波長λ2
とのレーザ光線の光路を分離して記載しているが、実際は各波長の光線は同一の光路を伝
搬することになる。
この図１２（ａ）（ｂ）に示す２波長対応回折格子１００は、ガラス等からなる透明基
板１０１の入射面側に断面形状が周期的な凹凸からなり均一の屈折率を有する回折格子１
０２を形成すると共に、透明基板１０１の出射面側に同じく断面形状が周期的な凹凸から
なり均一の屈折率を有する回折格子１０３を形成する。これにより、２波長レーザ光源１
０から波長λ1のレーザ光が出射された場合は、回折格子１０２により波長λ1のレーザ光
をメインビームとなる０次回折光Ｉ1（０）と、そのサイドビームとなる二つの±１次回
折光Ｉ1（±１）とに回折するようにしている。また２波長レーザ光源１０から波長λ2の
レーザ光が出射された場合は、回折格子１０３により波長λ2のレーザ光をメインビーム
となる０次回折光Ｉ2（０）と、そのサイドビームとなる二つの±１次回折光Ｉ2（±１）
とに回折するようにしている。 FIG. 12 is a diagram schematically showing the structure of a conventional two-wavelength compatible diffraction grating disclosed in Patent Document 1. In FIG. In FIG. 12, the wavelength λ 1 and the wavelength λ 2 are shown for easy understanding.
Although the optical paths of the laser beam are separated from each other, the light beams of the respective wavelengths actually propagate through the same optical path.
The diffraction grating 100 corresponding to two wavelengths shown in FIGS. 12 (a) and 12 (b) is a diffraction grating 1 having a uniform refractive index in which the cross-sectional shape is periodic unevenness on the incident surface side of the transparent substrate 101 made of glass or the like.
02 is formed, and a diffraction grating 103 having a uniform refractive index is formed on the emission surface side of the transparent substrate 101. Thereby, the two-wavelength laser light source 1
When the laser light having the wavelength λ 1 is emitted from 0, the diffraction grating 102 causes the laser light having the wavelength λ 1 to be the main beam, the 0th-order diffracted light I 1 (0), and the two ± 1 next times that are the side beams. The light is diffracted into the folded light I 1 (± 1). When laser light having a wavelength λ 2 is emitted from the two-wavelength laser light source 10, the diffraction grating 103 converts the laser light having a wavelength λ 2 into a 0th-order diffracted light I 2 (0) as a main beam and its side beam. Two ± 1st order diffracted lights I 2 (± 1)
And diffracted.

また、図１２に示す従来の２波長対応回折格子１００においては、回折格子１０２の幅
寸法Ｗ11と格子周期Ｐ11との比Ｗ11／Ｐ11（以下、デューティ比という）を０．５以外の
値に設定することにより、ＤＶＤ用の波長λ1の０次回折光Ｉ1（０）と１次回折光Ｉ1（
±１）の回折効率とが所定の値となるように調整している。また同様に回折格子１０３の
デューティ比Ｗ12／Ｐ12を０．５以外の値に設定することにより、ＣＤ用の波長λ2の０
次回折光Ｉ2（０）と１次回折光Ｉ2（±１）の回折効率が所定の値となるように調整して
いる。
特開２００１−２８１４３２公報 Further, in the conventional two-wavelength handling diffraction grating 100 shown in FIG. 12, the ratio W 11 / P 11 of the width dimension W 11 and the grating period P 11 of the diffraction grating 102 (hereinafter, referred to as duty ratio) 0.5 except the of by setting the value, 0-order diffracted light I 1 (0) of the wavelength lambda 1 for DVD and 1-order diffracted light I 1 (
The diffraction efficiency of ± 1) is adjusted to a predetermined value. Similarly, by setting the duty ratio W 12 / P 12 of the diffraction grating 103 to a value other than 0.5, the CD wavelength λ 2 is reduced to 0.
The diffraction efficiencies of the first-order diffracted light I 2 (0) and the first-order diffracted light I 2 (± 1) are adjusted to be a predetermined value.
JP 2001-281432 A

ところで、回折格子における光量損失は、周知の通り、回折格子のデューティ比の値が
０．５のときに最も小さくなり、０．５から離れるに従って大きくなる。このため、上記
図１２に示した２波長対応回折格子１００のように０次回折光と１次回折光の回折効率が
所定の値となるように、回折格子のデューティ比の値を０．５以外の値を調整すると、回
折格子における光量損失が大きくなる。この結果、従来の回折格子は、高い光量が求めら
れる例えばＤＶＤに情報の書き込みを行う光記録装置の光ピックアップ装置等に適用でき
ないという問題点があった。 By the way, as is well known, the light quantity loss in the diffraction grating becomes the smallest when the value of the duty ratio of the diffraction grating is 0.5, and becomes larger as the distance from 0.5 is increased. Therefore, the value of the duty ratio of the diffraction grating is set to a value other than 0.5 so that the diffraction efficiency of the 0th-order diffracted light and the 1st-order diffracted light becomes a predetermined value as in the two-wavelength-corresponding diffraction grating 100 shown in FIG. When the value is adjusted, the light amount loss in the diffraction grating increases. As a result, the conventional diffraction grating has a problem that it cannot be applied to, for example, an optical pickup device of an optical recording apparatus that writes information on a DVD that requires a high amount of light.

そこで、本発明は上記したような点を鑑みてなされたものであり、複数の異なる波長の
光を回折することが可能で、且つ、光量損失を抑制することができる回折格子と、回折格
子を備えた光ピックアップ装置を提供することを目的とする。 Therefore, the present invention has been made in view of the above points, and includes a diffraction grating capable of diffracting light having a plurality of different wavelengths and suppressing light loss, and a diffraction grating. An object of the present invention is to provide an optical pickup device provided.

上記目的を達成するため、本発明は、波長が異なる複数の光のうち、少なくとも一つの
波長の光が入射する回折格子であって、透明基材と、透明基材の両面上に夫々形成され、
第１の屈折率を有する第１の屈折率材料、第１の屈折率材料とは異なる第２の屈折率を有
する第２の屈折率材料、及び第２の屈折率材料上に形成される感光層を有し、第１の屈折
率材料と第２の屈折率材料とが交互に配置された第１及び第２の回折格子部と、を備え、
第１の回折格子部は、第１の波長に対して回折効率が所定の値で、且つ、第２の波長に対
して第１の屈折率材料と第２の屈折率材料との位相差が２πとなるように、第１及び第２
の屈折率材料の格子深さが設定され、第２の回折格子部は、第２の波長に対して回折効率
が所定の値で、且つ、第１の波長に対して第１の屈折率材料と第２の屈折率材料との位相
差が２πとなるように、第１及び第２の屈折率材料の格子深さが設定されている。
このように構成される本発明の回折格子は、第１の屈折率材料と第２の屈折率材料との
格子深さを調整することで、回折格子の幅寸法と格子周期とのデューティ比を０．５、ま
たは０．５に近い値にしつつ、夫々所定の波長に対してのみ所定の回折効率を有するよう
第１及び第２の回折格子部を構成した。これにより、複数の異なる波長の光を回折するこ
とが可能で、且つ、光量損失を抑制することができる。 In order to achieve the above object, the present invention is a diffraction grating on which light of at least one wavelength among a plurality of lights having different wavelengths is incident, and is formed on each of a transparent substrate and both surfaces of the transparent substrate. ,
A first refractive index material having a first refractive index, a second refractive index material having a second refractive index different from the first refractive index material, and a photosensitive formed on the second refractive index material First and second diffraction grating portions having a layer, wherein the first refractive index material and the second refractive index material are alternately arranged,
The first diffraction grating portion has a diffraction efficiency of a predetermined value with respect to the first wavelength, and a phase difference between the first refractive index material and the second refractive index material with respect to the second wavelength. First and second to be 2π
The grating depth of the refractive index material is set, and the second diffraction grating portion has a predetermined diffraction efficiency with respect to the second wavelength and the first refractive index material with respect to the first wavelength. The grating depths of the first and second refractive index materials are set so that the phase difference between the first refractive index material and the second refractive index material is 2π.
The diffraction grating of the present invention configured as described above adjusts the grating depth of the first refractive index material and the second refractive index material, thereby changing the duty ratio between the width dimension of the diffraction grating and the grating period. The first and second diffraction grating portions were configured so as to have a predetermined diffraction efficiency only for a predetermined wavelength while being set to 0.5 or a value close to 0.5. As a result, it is possible to diffract light having a plurality of different wavelengths, and it is possible to suppress light loss.

また本発明は、波長が異なる複数の光のうち、少なくとも一つの波長の光が入射する回
折格子であって、透明基材と、第１の屈折率を有する第１の屈折率材料、第１の屈折率材
料とは異なる第２の屈折率を有する第２の屈折率材料、及び第２の屈折率材料上に形成さ
れる感光層を有し、透明基材の表面上に第１の屈折率材料と第２の屈折率材料とが交互に
配置された回折格子部と、を備え、第１及び第２の波長を含む波長帯域における回折効率
が所定の値になるように、第１及び第２の屈折率材料の格子深さが夫々設定されている。
このように構成される本発明の回折格子は、第１及び第２の波長を含む波長帯域におけ
る回折効率が所定の値になるように第１の屈折率材料と第２の屈折率材料との格子深さを
設定しているので、回折格子の幅寸法と格子周期とのデューティ比を０．５、または０．
５に近い値にすることが可能になる。これにより、複数の異なる波長の光を回折すること
が可能で、且つ、光量損失を抑制することができる。 The present invention also relates to a diffraction grating on which light of at least one wavelength is incident among a plurality of lights having different wavelengths, a transparent substrate, a first refractive index material having a first refractive index, a first A second refractive index material having a second refractive index different from that of the first refractive index material, and a photosensitive layer formed on the second refractive index material, the first refractive on the surface of the transparent substrate A diffraction grating portion in which a refractive index material and a second refractive index material are alternately arranged, and the first and second diffraction efficiencies in a wavelength band including the first and second wavelengths are set to a predetermined value. The grating depth of the second refractive index material is set respectively.
The diffraction grating of the present invention configured as described above includes the first refractive index material and the second refractive index material so that the diffraction efficiency in a wavelength band including the first and second wavelengths becomes a predetermined value. Since the grating depth is set, the duty ratio between the width dimension of the diffraction grating and the grating period is set to 0.5, or 0.
A value close to 5 can be set. As a result, it is possible to diffract light having a plurality of different wavelengths, and it is possible to suppress light loss.

また本発明の回折格子は、第１の屈折率材料をアクリル系樹脂、第２の屈折率材料を誘
電体であるＴｉＯ2またはＴａ2Ｏ5を用いて構成すると、回折格子を安価に製造すること
が可能になる。
また第１の屈折率材料を吸湿性の小さい感光性ポリシラン樹脂、第２の屈折率材料を誘
電体であるＴｉＯ2またはＴａ2Ｏ5を用いて構成すると信頼性の高い回折格子を実現する
ことができる。 The diffraction grating according to the present invention can be manufactured at low cost when the first refractive index material is made of acrylic resin and the second refractive index material is made of dielectric TiO 2 or Ta 2 O 5. It becomes possible.
Further, if the first refractive index material is composed of a photosensitive polysilane resin having a low hygroscopic property, and the second refractive index material is composed of dielectric TiO 2 or Ta 2 O 5 , a highly reliable diffraction grating can be realized. Can do.

また本発明は、波長が異なる複数の光のうち、少なくとも一つの波長の光が入射する回
折格子の製造方法であって、透明基板上に、高屈折率材料４を成膜する工程と、高屈折率
材料を成膜した透明基板全体に低屈折率材料を成膜する工程と、高屈折率材料上に成膜し
た低屈折率材料に紫外線を照射して低屈折率材料とは屈折率の異なる感光層に変化させる
工程とからなる。
このようにすれば、本発明の回折格子を作製することができる。また、本発明の回折格
子の製造方法においては、低屈折率材料の上面にマスキングを施した後、フォトブリーチ
ング現象を利用して、高屈折率材料上の低屈折率材料の屈折率だけを変化させて感光層を
形成するようにしている。このようにすれば、高屈折率材料と感光層との位置合わせを精
度良く行うことができるため、位置ずれによる損失を最小限に抑えることができるという
利点もある。 The present invention also relates to a method of manufacturing a diffraction grating in which light of at least one wavelength is incident among a plurality of lights having different wavelengths, the step of forming a high refractive index material 4 on a transparent substrate, The process of depositing a low refractive index material on the entire transparent substrate on which the refractive index material is deposited, and the low refractive index material formed by irradiating the low refractive index material deposited on the high refractive index material with ultraviolet rays And changing to a different photosensitive layer.
In this way, the diffraction grating of the present invention can be produced. In the diffraction grating manufacturing method of the present invention, after masking the upper surface of the low refractive index material, the photobleaching phenomenon is used to obtain only the refractive index of the low refractive index material on the high refractive index material. The photosensitive layer is formed by changing. In this way, since the alignment between the high refractive index material and the photosensitive layer can be performed with high accuracy, there is also an advantage that loss due to misalignment can be minimized.

また本発明は、少なくとも２つの異なる波長の光を出射する光源と、前記光源から出射
光を光記録媒体に集光する対物レンズとを備え、光記録媒体に情報の記録又は／及び再生
を行う光ピックアップ装置であって、光源と対物レンズとの間の光路中に、本発明の回折
格子が配置されている。このように構成すれば、回折格子とモノリシック集積型２波長レ
ーザとを組み合わせて使用した場合でも、ＣＤやＤＶＤ等の異なる種類の光記録媒体に情
報の記録又は再生を確実に行うことができる。 The present invention also includes a light source that emits light of at least two different wavelengths and an objective lens that condenses the emitted light from the light source onto an optical recording medium, and records or / and reproduces information on the optical recording medium. In the optical pickup device, the diffraction grating of the present invention is disposed in the optical path between the light source and the objective lens. With this configuration, even when a diffraction grating and a monolithic integrated type two-wavelength laser are used in combination, information can be recorded or reproduced reliably on different types of optical recording media such as a CD and a DVD.

以下、図面を用いて本発明の実施形態を詳細に説明する。
図１は、本発明の第１の実施形態に係る２波長対応回折格子の構造を模式的に示した図
である。なお、図１においては、説明を分かり易くするために、波長λ1と波長λ2とのレ
ーザ光線の光路を分離して記載しているが、実際は各波長の光線は同一の光路を伝搬する
ことになる。
この図１（ａ）（ｂ）に示す２波長対応回折格子１は、ガラス等の透明基材であるガラ
ス透明基板２の一方の表面上に、低屈折率（第１の屈折率）を有する低屈折率材料（第１
の屈折率材料）３ａと、この低屈折率材料３ａとは異なる高屈折率（第２の屈折率）を有
する高屈折率材料（第２の屈折率材料）４ａとを交互に配置した第１の回折格子部５を形
成すると共に、他方の表面上に低屈折率を有する低屈折率材料３ｂと、この低屈折率材料
３ｂとは異なる高屈折率を有する高屈折率材料４ｂとを交互に配置した第２の回折格子部
６を形成した。
ここで、前記低屈折率材料３ａ、３ｂには、感光することにより分解が生じて屈折率を
制御できる性質（フォトブリーチング性）を備えた感光性樹脂（ポリシラン樹脂、アクリ
ル樹脂等）を使用し、高屈折率材料４ａ、４ｂとして誘電体であるＴｉＯ2またはＴａ2Ｏ
5を使用した。
更に、前記高屈折率材料４ａ、４ｂ上に形成した前記低屈折率材料３ａ、３ｂを、該高
屈折率材料４ａ、４ｂに近接配置した低屈折率材料３ａ、３ｂの屈折率よりも小さくする
ために感光して、感光層７ａ、７ｂを夫々形成した。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram schematically showing the structure of a two-wavelength compatible diffraction grating according to the first embodiment of the present invention. In FIG. 1, for easy understanding, the optical paths of the laser beams having the wavelengths λ 1 and λ 2 are shown separately, but in actuality, the light beams of the respective wavelengths propagate through the same optical path. It will be.
1A and 1B has a low refractive index (first refractive index) on one surface of a glass transparent substrate 2 which is a transparent base material such as glass. Low refractive index material (first
First refractive index material) 3a and high refractive index material (second refractive index material) 4a having a high refractive index (second refractive index) different from the low refractive index material 3a are alternately arranged. The low refractive index material 3b having a low refractive index on the other surface and the high refractive index material 4b having a high refractive index different from the low refractive index material 3b are alternately formed on the other surface. The arranged second diffraction grating portion 6 was formed.
Here, as the low refractive index materials 3a and 3b, photosensitive resins (polysilane resin, acrylic resin, etc.) having a property (photo bleaching property) capable of controlling the refractive index by being decomposed by exposure to light are used. TiO 2 or Ta 2 O which is a dielectric as the high refractive index materials 4a and 4b
5 was used.
Further, the low refractive index materials 3a and 3b formed on the high refractive index materials 4a and 4b are made smaller than the refractive indexes of the low refractive index materials 3a and 3b disposed close to the high refractive index materials 4a and 4b. Therefore, photosensitive layers 7a and 7b were formed respectively.

この場合、第１の回折格子部５は、第１の波長であるＤＶＤ用の波長λ1（６５０ｎｍ
）に対して回折効率が所定の値となるように低屈折率材料３ａの幅寸法Ｗ1と回折周期Ｐ1
とのデューティ比Ｗ1／Ｐ1を略０．５の値に設定し、かつ、第２の波長であるＣＤ用の波
長λ2（７８５ｎｍ）に対して低屈折率材料３ａと高屈折率材料４ａとの位相差が２πと
なるよう低屈折率材料３ａの格子深さｄL1と高屈折率材料４ａの格子深さｄH1を夫々設定
した。
また第２の回折格子部６は、ＣＤ用の波長λ2に対しては回折効率が所定の値となるよ
うに低屈折率材料３ｂの幅寸法Ｗ2と格子周期Ｐ2とのデューティ比Ｗ2／Ｐ2を略０．５の
値に設定し、且つ、波長λ1に対して低屈折率材料３ｂと高屈折率材料４ｂとの位相差が
２πとなるよう低屈折率材料３ｂの格子深さｄL2と高屈折率材料４ｂの格子深さｄH2を夫
々設定した。 In this case, the first diffraction grating portion 5 has a wavelength λ 1 (650 nm for DVD) which is the first wavelength.
), The width dimension W 1 of the low refractive index material 3a and the diffraction period P 1 so that the diffraction efficiency becomes a predetermined value.
The duty ratio W 1 / P 1 is set to a value of approximately 0.5 with, and the low refractive index material 3a and a high refractive index material for a wavelength lambda 2 for CD is a second wavelength (785 nm) the phase difference between the 4a has respectively set the grating depth d H1 of the grating depth d L1 of the low refractive index material 3a so as to be 2π high refractive index material 4a.
The second diffraction grating section 6 has a duty ratio W between the width dimension W 2 of the low refractive index material 3b and the grating period P 2 so that the diffraction efficiency becomes a predetermined value for the wavelength λ 2 for CD. 2 / P 2 is set to a value of about 0.5, and the lattice of the low refractive index material 3b is set so that the phase difference between the low refractive index material 3b and the high refractive index material 4b is 2π with respect to the wavelength λ 1 . The depth d L2 and the grating depth d H2 of the high refractive index material 4b were set.

図２は回折格子部のデューティ比と回折効率の関係を示した図であり、（ａ）は０次回
折効率を、（ｂ）は１次回折効率を夫々示した図である。
この図２（ａ）に示すように、第１及び第２の回折格子部５、６の０次回折効率は、通
常デューティ比の値が０．５のときに最も小さな値となり、０．５の値から離れるにした
がって大きくなる。一方、図２（ｂ）に示すように第１及び第２の回折格子部５、６の±
１次回折効率は、デューティ比の値が０．５のときに最も大きな値になり、０．５の値か
ら離れるにしたがって小さくなる。
そこで、本実施形態の２波長対応回折格子１においては、第１及び第２の回折格子部５
、６のデューティ比を０．５、或いは０．５に近い値に設定することにより、第１及び第
２の回折格子部５、６における光量損失を抑制したうえで、低屈折率材料３ａ、３ｂの格
子深さｄL1、ｄL2と、高屈折率材料４ａ、４ｂの格子深さｄH1、ｄH2と、を夫々調整する
ようにした。 2A and 2B are diagrams showing the relationship between the duty ratio of the diffraction grating portion and the diffraction efficiency. FIG. 2A shows the 0th-order diffraction efficiency, and FIG. 2B shows the 1st-order diffraction efficiency.
As shown in FIG. 2A, the 0th-order diffraction efficiency of the first and second diffraction grating portions 5 and 6 is the smallest value when the value of the normal duty ratio is 0.5. The value increases as the distance from the value increases. On the other hand, as shown in FIG. 2 (b), the first and second diffraction grating portions 5 and 6 have ±
The first-order diffraction efficiency becomes the largest value when the duty ratio value is 0.5, and decreases as the distance from the value becomes 0.5.
Therefore, in the two-wavelength diffraction grating 1 of the present embodiment, the first and second diffraction grating portions 5 are used.
, 6 is set to 0.5 or a value close to 0.5, thereby suppressing the light amount loss in the first and second diffraction grating portions 5 and 6, and the low refractive index material 3a, The grating depths d L1 and d L2 of 3b and the grating depths d H1 and d H2 of the high refractive index materials 4a and 4b were adjusted.

これにより、２波長レーザ光源１０から波長λ1のレーザ光が出射された場合は、第１
の回折格子部５により波長λ1のレーザ光を所定の回折効率でメインビームとなる０次回
折光Ｉ1（０）と、そのサイドビームとなる二つの±１次回折光Ｉ1（±１）とに回折し、
２波長レーザ光源１０から波長λ2のレーザ光が出射された場合は、第２の回折格子部６
により波長λ2のレーザ光を所定の回折効率でメインビームとなる０次回折光Ｉ2（０）と
、そのサイドビームとなる二つの±１次回折光Ｉ2（±１）とに回折するようにしている
。 As a result, when the laser light having the wavelength λ 1 is emitted from the two-wavelength laser light source 10, the first
With the diffraction grating section 5, the 0th-order diffracted light I 1 (0) that becomes the main beam of the laser light of wavelength λ 1 with a predetermined diffraction efficiency, and two ± 1st-order diffracted lights I 1 (± 1) that become the side beams Diffracted into
When laser light having a wavelength λ 2 is emitted from the two-wavelength laser light source 10, the second diffraction grating unit 6
Thus, the laser beam of wavelength λ 2 is diffracted into zero-order diffracted light I 2 (0) as the main beam and two ± 1st-order diffracted lights I 2 (± 1) as the side beams with a predetermined diffraction efficiency. ing.

図１２に示した従来の２波長対応回折格子１００は、凹部を空気により構成しているの
で屈折率が１であるために、波長λ1、λ2の０次回折効率と１次回折効率とが夫々所定の
値となるように回折格子のデューティ比を夫々調整し、例えばＣＤの波長光を３ビーム化
するために０次回折光と１次回折光との比率を１５：１に調整した場合は、デューティ比
が０．５の値から大きくずれて、第１及び第２の回折格子部５、６における光量損失が大
きくなってしまうという問題点があった。 Since the conventional two-wavelength-corresponding diffraction grating 100 shown in FIG. 12 has a concave portion made of air and has a refractive index of 1, the zero-order diffraction efficiency and the first-order diffraction efficiency at wavelengths λ 1 and λ 2 When the duty ratio of the diffraction grating is adjusted so that each becomes a predetermined value, for example, the ratio of the 0th-order diffracted light to the 1st-order diffracted light is adjusted to 15: 1 in order to convert the wavelength light of the CD into 3 beams There is a problem that the light amount loss in the first and second diffraction grating portions 5 and 6 becomes large when the duty ratio deviates greatly from the value of 0.5.

これに対して、本実施形態の２波長対応回折格子１は、ガラス透明基板２の一方の表面
上に低屈折率材料３ａと高屈折率材料４ａとを交互に配置すると共に、前記高屈折率材料
４ａ上に形成した前記低屈折率材料３ａを、該高屈折率材料４ａに近接配置した低屈折率
材料３ａの屈折率よりも小さくするために感光して、感光層７ａを形成して第１の回折格
子部５を形成し、ガラス透明基板２の他方の表面上に低屈折率材料３ｂと高屈折率材料４
ｂとを交互に配置すると共に、前記高屈折率材料４ｂ上に形成した前記低屈折率材料３ｂ
を、該高屈折率材料４ｂに近接配置した低屈折率材料３ｂの屈折率よりも小さくするため
に感光して、感光層７ｂを形成して第２の回折格子部６を形成する。この際、第１の回折
格子部５は、ＤＶＤ用の波長λ1に対して回折効率が所定の値で、且つ、ＣＤ用のλ2に対
して低屈折率材料３ａと高屈折率材料４ａとの位相差が２πとなるよう低屈折率材料３ａ
と高屈折率材料４ａの格子深さを設定するようにした。また第２の回折格子部６は、ＣＤ
用の波長λ２に対して回折効率が所定の値で、且つ、波長λ１に対して低屈折率材料３ｂ
と高屈折率材料４ｂとの位相差が２πとなるよう低屈折率材料３ｂと高屈折率材料４ｂの
格子深さを設定した。このように構成することによって、複数の異なる波長の光を回折す
ることを可能とすると共に、光量損失も抑制することができた。 In contrast, the two-wavelength diffraction grating 1 of the present embodiment alternately arranges the low refractive index material 3a and the high refractive index material 4a on one surface of the glass transparent substrate 2, and the high refractive index. The low refractive index material 3a formed on the material 4a is exposed in order to make it smaller than the refractive index of the low refractive index material 3a disposed close to the high refractive index material 4a, and a photosensitive layer 7a is formed to form a first layer. 1 is formed, and the low refractive index material 3 b and the high refractive index material 4 are formed on the other surface of the glass transparent substrate 2.
b and the low refractive index material 3b formed on the high refractive index material 4b.
Is photosensitized so as to be smaller than the refractive index of the low refractive index material 3b disposed close to the high refractive index material 4b, and the second diffraction grating portion 6 is formed by forming the photosensitive layer 7b. At this time, the first diffraction grating portion 5 has a predetermined diffraction efficiency with respect to the wavelength λ 1 for DVD and a low refractive index material 3 a and a high refractive index material 4 a with respect to λ 2 for CD. The low refractive index material 3a so that the phase difference from the
And the grating depth of the high refractive index material 4a is set. The second diffraction grating portion 6 is a CD.
The diffraction efficiency is a predetermined value for the wavelength λ2 and the low refractive index material 3b for the wavelength λ1.
The grating depths of the low refractive index material 3b and the high refractive index material 4b were set so that the phase difference between the high refractive index material 4b and the high refractive index material 4b was 2π. With this configuration, it was possible to diffract light having a plurality of different wavelengths and to suppress a light amount loss.

また、２波長対応回折格子１においては、低屈折率材料３として汎用的なアクリル系樹
脂、高屈折率材料４として誘電体であるＴｉＯ2またはＴａ2Ｏ5を使用することによって
、安価に製造することができる。
また、低屈折率材料３として吸湿性が小さい感光性ポリシラン樹脂（日本ペイント製グ
ラシア等）、高屈折率材料４として誘電体であるＴｉＯ2またはＴａ2Ｏ5を使用すること
によって、信頼性の高い回折格子を実現することができる。
更にまた、回折パターンを構成する感光性樹脂層として、感光することで屈折率を制御
できるアクリル樹脂、ポリシラン樹脂などを用いたので、これらの樹脂と前記透明基板２
の表面との接合力は十分に強いため、透明基板との密着力を確保するためのアンダーコー
ト層（ＰＥＴ層等）を形成する必要がなくなり、透明基板２上に直接感光性樹脂層を形成
することができる。また、感光性樹脂を塗布する方法はスピンナやローラを用いる方法が
設備費用も比較的安価に抑えられるため望ましい。
なお、感光性ポリシラン樹脂とは、ケイ素原子が一次元的に直接結合した高分子材料で
あり、紫外線露光した部分のみ屈折率が変化する現象光学特性を有している。 The two-wavelength diffraction grating 1 is manufactured at a low cost by using a general-purpose acrylic resin as the low refractive index material 3 and TiO 2 or Ta 2 O 5 as a dielectric as the high refractive index material 4. can do.
Further, by using photosensitive polysilane resin (Nippon Paint Gracia etc.) having low hygroscopicity as the low refractive index material 3, and using TiO 2 or Ta 2 O 5 which is a dielectric as the high refractive index material 4, reliability can be improved. A high diffraction grating can be realized.
Furthermore, since an acrylic resin, a polysilane resin, or the like whose refractive index can be controlled by exposure is used as the photosensitive resin layer constituting the diffraction pattern, these resins and the transparent substrate 2 are used.
Since the bonding strength with the surface of the substrate is sufficiently strong, it is no longer necessary to form an undercoat layer (PET layer, etc.) to ensure adhesion to the transparent substrate, and a photosensitive resin layer is formed directly on the transparent substrate 2 can do. In addition, a method of applying a photosensitive resin is desirable because a method using a spinner or a roller can keep the equipment cost relatively low.
The photosensitive polysilane resin is a polymer material in which silicon atoms are directly bonded in a one-dimensional manner, and has a phenomenon optical characteristic that the refractive index changes only in a portion exposed to ultraviolet rays.

図３は本発明の第２の実施形態に係る２波長対応回折格子の構造を模式的に示した図で
ある。
この図３に示す２波長対応回折格子２０は、ガラス等の透明基材であるガラス透明基板
２と、低屈折率（第１の屈折率）を有する低屈折率材料（第１の屈折率材料）３と、低屈
折率材料３とは異なる屈折率で、且つ低屈折率材料３の屈折率より高い高屈折率（第２の
屈折率）を有する高屈折率材料（第２の屈折率材料）４とからなる。そして、ガラス透明
基板２の出射面側に低屈折率材料３と高屈折率材料４とを交互に配置することにより、ガ
ラス透明基板２の表面に断面形状が周期的な凹凸となる回折格子を形成するようにしてい
る。また高屈折率材料４上に形成した前記低屈折率材料３を、該高屈折率材料４に近接配
置した低屈折率材料３の屈折率よりも小さくするために感光して、感光層７を形成した。
そしてこの場合も、低屈折率材料３の幅Ｗ3と周期Ｐ3とのデューティ比Ｗ3／Ｐ3を０．
５の値に設定したうえで、所定の波長帯域における回折効率がほぼ一定となるように低屈
折率材料３と高屈折率材料４との格子深さ（厚さ）を適宜設定するようにした点に特徴が
ある。 FIG. 3 is a diagram schematically showing the structure of a diffraction grating for two wavelengths according to the second embodiment of the present invention.
The two-wavelength diffraction grating 20 shown in FIG. 3 includes a glass transparent substrate 2 that is a transparent substrate such as glass, and a low refractive index material (first refractive index material) having a low refractive index (first refractive index). 3) and a high refractive index material (second refractive index material) having a refractive index different from that of the low refractive index material 3 and having a higher refractive index (second refractive index) than the refractive index of the low refractive index material 3 ) 4. Then, by alternately disposing the low refractive index material 3 and the high refractive index material 4 on the emission surface side of the glass transparent substrate 2, a diffraction grating whose cross-sectional shape becomes periodic irregularities on the surface of the glass transparent substrate 2. Try to form. Further, the low refractive index material 3 formed on the high refractive index material 4 is exposed to make it smaller than the refractive index of the low refractive index material 3 disposed close to the high refractive index material 4, and the photosensitive layer 7 is formed. Formed.
And again, the duty ratio W 3 / P 3 of the width W 3 and the period P 3 of the low refractive index material 3 0.
After setting to a value of 5, the grating depth (thickness) of the low refractive index material 3 and the high refractive index material 4 is appropriately set so that the diffraction efficiency in a predetermined wavelength band is substantially constant. There is a feature in the point.

図４は、２波長対応回折格子２０における波長と回折効率との関係を示した図である。
この図４に示すように２波長対応回折格子２０は、少なくともＤＶＤ用の波長λ1（６５
０ｎｍ）からＣＤ用の波長λ2（７８５ｎｍ）までの波長帯域における０次回折光Ｉ（０
）とその±１次回折光Ｉ（±１）の回折効率の値をほぼ同じにすることができる。 FIG. 4 is a diagram showing the relationship between the wavelength and the diffraction efficiency in the two-wavelength diffraction grating 20.
As shown in FIG. 4, the two-wavelength diffraction grating 20 has at least a wavelength λ 1 (65 for DVD).
0th order) in the wavelength band from CD wavelength λ 2 (785 nm) to zeroth order diffracted light I (0
) And the ± 1st order diffracted light I (± 1) can be made substantially the same in diffraction efficiency.

ここで、図５を参照しながら、低屈折率材料（感光性樹脂）３、感光後の低屈折率材料
（感光層）７と高屈折率材料４との格子深さと回折効率との関係を説明する。
図５は、２波長対応回折格子２０の回折格子部分を示した拡大断面図であり、この図５
に示すように、低屈折率材料３の屈折率をｎL、感光層７の屈折率をｎL’、高屈折率材料
４の屈折率をｎH、回折格子のピッチをＰ、低屈折率材料３部分の幅をＷ、低屈折率材料
３の格子深さをｄL、高屈折率材料４の格子深さをｄHとする。
回折格子のｍ次光の回折効率をηmとすると、回折効率ηmは、Ｐ、Ｗ、Γによって式（
１）のような関数によって示すことができる。 Here, referring to FIG. 5, the relationship between the grating depth and the diffraction efficiency of the low refractive index material (photosensitive resin) 3, the low refractive index material (photosensitive layer) 7 after exposure and the high refractive index material 4 is shown. explain.
FIG. 5 is an enlarged cross-sectional view showing a diffraction grating portion of the two-wavelength compatible diffraction grating 20. FIG.
, The refractive index of the low refractive index material 3 is n L , the refractive index of the photosensitive layer 7 is n L ′, the refractive index of the high refractive index material 4 is n H , the pitch of the diffraction grating is P, and the low refractive index. The width of the material 3 portion is W, the grating depth of the low refractive index material 3 is d L , and the grating depth of the high refractive index material 4 is d H.
Assuming that the diffraction efficiency of the m-order light of the diffraction grating is η m , the diffraction efficiency η m is expressed by the formula (
It can be shown by a function like 1).

Figure 2007334975
Figure 2007334975

位相変調量Γは波長により変化するため、異なる波長で回折効率ηmを同じ値にするた
めには、波長が変化しても位相変調量Γが変化しないように補償すれば良い。
ここで、位相変調量Γは式（２）のように示すことができる。

Figure 2007334975
Since the phase modulation amount Γ changes depending on the wavelength, in order to make the diffraction efficiency η m the same value at different wavelengths, it is only necessary to compensate so that the phase modulation amount Γ does not change even if the wavelength changes.
Here, the phase modulation amount Γ can be expressed as in Expression (2).

Figure 2007334975

また、格子材料の屈折率は波長分散を持つため、波長λ1での低屈折率材料３の屈折率
をｎL1、感光層７の屈折率をｎL1’、高屈折率材料４の屈折率をｎH1、波長λ2での低屈
折率材料３の屈折率をｎL2、感光層７の屈折率をｎL2’、高屈折率材料４の屈折率をｎH2
とすると、波長λ1における位相変調量をΓ1、及び波長λ2における位相変調量をΓ2は、
下記式（３）、（４）のように示すことができる。 Further, since the refractive index of the grating material has wavelength dispersion, the refractive index of the low refractive index material 3 at the wavelength λ 1 is n L1 , the refractive index of the photosensitive layer 7 is n L1 ′, and the refractive index of the high refractive index material 4. N H1 , the refractive index of the low refractive index material 3 at the wavelength λ 2 is n L2 , the refractive index of the photosensitive layer 7 is n L2 ′, and the refractive index of the high refractive index material 4 is n H2.
Then, the phase modulation amount at the wavelength λ 1 is Γ 1 , and the phase modulation amount at the wavelength λ 2 is Γ 2 .
It can be shown as the following formulas (3) and (4).

Figure 2007334975

Figure 2007334975
Figure 2007334975

Figure 2007334975

そして、波長λ1及びλ2における回折効率を同じにするには、Γ1＝Γ2であれば良いか
ら、

Figure 2007334975
を満足するように各条件を設定すれば良い。 And in order to make the diffraction efficiencies at the wavelengths λ 1 and λ 2 the same, Γ 1 = Γ 2 suffices,
Figure 2007334975
Each condition may be set to satisfy

ここで、一例として、低屈折率材料３をポリシラン樹脂、感光層７を感光後のポリシラ
ン樹脂、高屈折率材料４をＴａ2Ｏ5、波長λ1を６６０ｎｍ、波長λ2を７８５ｎｍとする
と、各波長λ1及びλ2におけるＳｉＯ2、Ｔａ2Ｏ5の屈折率は、
波長λ1（６６０ｎｍ） ｎL1＝１．５９６、ｎL1’＝１．４９６、ｎH1＝２．１６４
波長λ2（７８５ｎｍ） ｎL2＝１．５８７、ｎL2’＝１．４８７、ｎH2＝２．１４７
となる。 Here, as an example, if the low refractive index material 3 is a polysilane resin, the photosensitive layer 7 is a polysilane resin after exposure, the high refractive index material 4 is Ta 2 O 5 , the wavelength λ 1 is 660 nm, and the wavelength λ 2 is 785 nm, The refractive index of SiO 2 and Ta 2 O 5 at each wavelength λ 1 and λ 2 is
Wavelength λ 1 (660 nm) n L1 = 1.596, n L1 ′ = 1.497, n H1 = 2.164
Wavelength λ 2 (785 nm) n L2 = 1.587, n L2 '= 1.487, n H2 = 2.147
It becomes.

これらの値を上記した式（５）に代入すると、下記式（６）の結果が得られる。

Figure 2007334975
By substituting these values into the above equation (5), the result of the following equation (6) is obtained.

Figure 2007334975

従って、この式（６）を満たすように低屈折率材料３の格子深さｄLと、高屈折率材料
４の格子深さｄHを設定すれば、ＤＶＤ用の波長λ1における０次回折光Ｉ（０）の回折効
率とＣＤ用の波長λ2における０次回折光Ｉ（０）の回折効率をほぼ同じに設定すること
ができる。なお、説明は省略するが、同様にＤＶＤ用の波長λ1における１次回折光Ｉ（
±１）の回折効率と、ＣＤ用の波長λ2における１次回折光Ｉ（±１）の回折効率もほぼ
同じに設定することができる。 Thus, the grating depth d L of the low refractive index material 3 so as to satisfy the equation (6), by setting the grating depth d H of the high refractive index material 4, 0-order diffracted light at the wavelength lambda 1 for DVD The diffraction efficiency of I (0) and the diffraction efficiency of the 0th-order diffracted light I (0) at the wavelength λ 2 for CD can be set substantially the same. Note that description is omitted, similarly first order diffracted light at the wavelength lambda 1 for DVD I (
The diffraction efficiency of ± 1) and the diffraction efficiency of the first-order diffracted light I (± 1) at the wavelength λ 2 for CD can be set substantially the same.

ここで、回折光量比（０次回折光／１次回折光）＝１５．０に設定する場合を考えると
、波長λ1における位相変調量Γ1＝０．１２３とすれば良いので、式（３）よりｄH＝１
９２２ｎｍ、式（６）よりｄL＝１３６５０ｎｍが得られる。
図６は、低屈折率材料３の格子深さｄL＝１３６５０ｎｍ、高屈折率材料４の格子深さ
ｄH＝１９２２ｎｍに設定したときの波長と回折効率との関係をシミュレーションした結
果を示した図である。
この図６に示すシミュレーション結果からも、ＤＶＤ用の波長λ1からＣＤ用の波長λ2
における０次回折光Ｉ（０）及び１次回折光Ｉ（±１）の回折効率をほぼ同じに設定でき
ることが確認された。 Here, considering the case of setting the diffracted light quantity ratio (0th order diffracted light / 1st order diffracted light) = 15.0, the phase modulation amount Γ 1 = 0.123 at the wavelength λ 1 may be set. D H = 1
922 nm, d L = 13650 nm is obtained from the equation (6).
FIG. 6 shows the result of simulating the relationship between the wavelength and the diffraction efficiency when the grating depth d L of the low refractive index material 3 is set to 13650 nm and the grating depth of the high refractive index material 4 is set to d H = 1922 nm. FIG.
Also from the simulation results shown in FIG. 6, the wavelength λ 1 for DVD to the wavelength λ 2 for CD
It was confirmed that the diffraction efficiencies of the 0th-order diffracted light I (0) and the 1st-order diffracted light I (± 1) in FIG.

このように構成される２波長対応回折格子２０においては、ガラス透明基板２の表面上
に交互に形成する低屈折率材料３と高屈折率材料４の格子深さを設定しているので、回折
格子部のデューティ比を０．５、若しくは０．５に近い値に設定することが可能になる。
これにより、複数の異なる波長λ1、λ2の光を回折することが可能で、且つ、光量損失を
抑制することができる。 In the two-wavelength diffraction grating 20 configured in this way, the grating depths of the low refractive index material 3 and the high refractive index material 4 that are alternately formed on the surface of the glass transparent substrate 2 are set. It becomes possible to set the duty ratio of the lattice part to 0.5 or a value close to 0.5.
As a result, it is possible to diffract light having a plurality of different wavelengths λ 1 and λ 2 , and to suppress light quantity loss.

また上記２波長対応回折格子２０においても、例えば低屈折率材料３として汎用的なア
クリル系樹脂や吸湿性が小さい感光性ポリシラン樹脂（日本ペイント製グラシア等）、高
屈折率材料４として同じく誘電体であるＴｉＯ2又はＴａ2Ｏ5を夫々用いるようにすると
、例えば、高い信頼性が要求される車載用の光ディスク装置の光ピックアップ装置に好適
な回折格子を実現することができる。 In the two-wavelength diffraction grating 20, for example, a general-purpose acrylic resin or a low-hygroscopic photosensitive polysilane resin (Nippon Paint Gracia, etc.) is used as the low refractive index material 3, and a dielectric is used as the high refractive index material 4. When TiO 2 or Ta 2 O 5 is used, for example, it is possible to realize a diffraction grating suitable for an optical pickup device of an in-vehicle optical disk device that requires high reliability.

ここで、本実施形態に係る２波長対応回折格子１の製造方法について、図７を参照しつ
つ詳細に説明する。
まず、図７（ａ）に示すように透明ガラス基板２を用意し、図７（ｂ）に示すように透
明ガラス基板２の表面上に真空蒸着機やスパッタ成膜等の成膜装置を用いてＴａ2Ｏ5等の
高屈折率材料４を形成する。次に、図７（ｃ）に示すように高屈折率材料４の表面上にフ
ォトレジスト４１を塗布し、図７（ｄ）に示すように回折格子の仕様に基づいて所定の寸
法でパターニングされたマスク４２を用いてフォトレジスト４１を露光する。フォトレジ
スト４１を現像したのが図７（ｅ）に示す図である。そして、図７（ｆ）に示すようにフ
ォトレジストの感光部４１ａにより覆われていない領域の高屈折率材料４をエッチングに
より除去する。次に図７（ｇ）に示すように高屈折率材料４を形成したガラス透明基板２
全体に感光性ポリシラン樹脂の低屈折率材料３を塗布した後、図７（ｈ）に示すように低
屈折率材料３を高屈折率材料４の成膜位置と対応する位置に開口部４３ａが形成されたフ
ォトマスク４３によりマスキングした後、図７（ｉ）に示すように上方から紫外線を照射
することにより、低屈折率材料３のうち、紫外線により露光された部分の屈折率だけを変
化させて感光層７を形成する。以上の工程を前記透明基板２の裏面にも施すことによって
、前記透明基板２の両主面に夫々回折格子部を形成して本実施形態の構造の２波長対応回
折格子１を製造することができる。
高屈折率材料４上の感光性ポリシラン樹脂をフォトリソグラフィ技法とエッチング技法
とを用いて、取り除くことによって空気層を形成するようにしても良いが、空気の屈折率
（＝１）とほぼ同程度となるように感光性ポリシランを紫外線照射により感光させること
によって屈折率を変化させた方が煩雑性がないので低コストで２波長対応回折格子１を製
造することができる。
なお、本実施形態では、低屈折率材料３として感光性ポリシラン樹脂を例に挙げて説明
したが、感光性ポリシラン樹脂の代わりにアクリル樹脂を用いても同様に作製することが
可能である。 Here, the manufacturing method of the two-wavelength diffraction grating 1 according to the present embodiment will be described in detail with reference to FIG.
First, a transparent glass substrate 2 is prepared as shown in FIG. 7A, and a film deposition apparatus such as a vacuum vapor deposition machine or sputter film formation is used on the surface of the transparent glass substrate 2 as shown in FIG. 7B. Thus, a high refractive index material 4 such as Ta 2 O 5 is formed. Next, as shown in FIG. 7C, a photoresist 41 is applied on the surface of the high refractive index material 4, and is patterned with a predetermined dimension based on the specifications of the diffraction grating as shown in FIG. 7D. The photoresist 41 is exposed using the mask 42. FIG. 7E shows a state where the photoresist 41 is developed. Then, as shown in FIG. 7 (f), the high refractive index material 4 in the region not covered with the photosensitive portion 41a of the photoresist is removed by etching. Next, as shown in FIG. 7G, the glass transparent substrate 2 on which the high refractive index material 4 is formed.
After the low refractive index material 3 of the photosensitive polysilane resin is applied to the whole, an opening 43a is formed at a position corresponding to the film forming position of the high refractive index material 4 as shown in FIG. After masking with the formed photomask 43, as shown in FIG. 7 (i), ultraviolet rays are irradiated from above to change only the refractive index of the portion exposed to the ultraviolet rays in the low refractive index material 3. Thus, the photosensitive layer 7 is formed. By performing the above process on the back surface of the transparent substrate 2 as well, diffraction grating portions are formed on both main surfaces of the transparent substrate 2 to manufacture the two-wavelength diffraction grating 1 having the structure of this embodiment. it can.
An air layer may be formed by removing the photosensitive polysilane resin on the high refractive index material 4 by using a photolithography technique and an etching technique, but it is approximately the same as the refractive index of air (= 1). Thus, it is less complicated to change the refractive index by exposing the photosensitive polysilane to ultraviolet radiation so that the two-wavelength diffraction grating 1 can be manufactured at low cost.
In the present embodiment, the photosensitive polysilane resin has been described as an example of the low refractive index material 3, but it can be similarly manufactured by using an acrylic resin instead of the photosensitive polysilane resin.

また、本実施形態の２波長対応回折格子の製造方法においては、低屈折率材料３の上面
をフォトマスク４３によりマスキングを施した後、光学特性であるフォトブリーチング現
象、即ち、紫外線露光した部分のみ屈折率が変化する現象を利用して、高屈折率材料４上
の低屈折率材料３の屈折率だけを変化させて感光層７を形成するようにしている。このよ
うにすれば、高屈折率材料４と感光層７との位置合わせを精度良く行うことができるため
、位置ずれによる損失を最小限に抑えることができるという利点がある。 Further, in the manufacturing method of the two-wavelength diffraction grating of the present embodiment, the upper surface of the low refractive index material 3 is masked by the photomask 43 and then the photobleaching phenomenon which is an optical characteristic, that is, the portion exposed to ultraviolet rays. Only the refractive index of the low refractive index material 3 on the high refractive index material 4 is changed to form the photosensitive layer 7 using the phenomenon that the refractive index changes only. In this way, since the alignment between the high refractive index material 4 and the photosensitive layer 7 can be performed with high accuracy, there is an advantage that loss due to misalignment can be minimized.

図８は上記した本実施形態の２波長対応回折格子１、２０を備えた光ピックアップ装置
の構成を示した図である。
この図８に示す光ピックアップ装置は、２波長レーザ光源１０から出射された光が２波
長対応回折格子１（２０）において０次回折光と±１次回折光に回折される。２波長対応
回折格子１（２０）において回折された０次回折光と±１次回折光はビームスプリッタ２
１を透過し、コリメートレンズ２２により平行光にされた後、対物レンズ２３により光デ
ィスク３０の情報記録面上に集光される。そして、光ディスク３０で反射された光が再び
対物レンズ２３、及びコリメートレンズ２２を透過し、ビームスプリッタ２１により反射
されて光検出器２４の受光面において受光されることになる。
このように本実施形態の２波長対応回折格子１（２０）を用いて光ピックアップ装置を
構成すれば、レーザ光源として２波長レーザ光源１０を使用した場合でも、ＣＤやＤＶＤ
等の異なる種類の光ディスクに対して情報の記録又は／及び再生を確実に行うことが可能
になる。 FIG. 8 is a diagram showing a configuration of an optical pickup device including the above-described two-wavelength diffraction gratings 1 and 20 of the present embodiment.
In the optical pickup device shown in FIG. 8, light emitted from the two-wavelength laser light source 10 is diffracted into zero-order diffracted light and ± first-order diffracted light by the two-wavelength diffraction grating 1 (20). The zero-order diffracted light and the ± first-order diffracted light diffracted by the two-wavelength compatible diffraction grating 1 (20)
1, is collimated by the collimator lens 22, and then condensed on the information recording surface of the optical disk 30 by the objective lens 23. Then, the light reflected by the optical disk 30 passes through the objective lens 23 and the collimating lens 22 again, is reflected by the beam splitter 21, and is received by the light receiving surface of the photodetector 24.
As described above, when the optical pickup device is configured by using the two-wavelength diffraction grating 1 (20) of the present embodiment, even when the two-wavelength laser light source 10 is used as a laser light source, a CD or DVD is used.
It is possible to reliably record and / or reproduce information on different types of optical disks.

図９は本発明の第３の実施形態に係る２波長対応回折格子の構造を模式的に示した図で
ある。なお、図１と同一部位には同一符号を付して詳細な説明は省略する。
この図９（ａ）（ｂ）に示す２波長対応回折格子３０は、透明基板２ａの一方の表面に
第１の回折格子部５を形成すると共に、透明基板２ｂの一方の表面に第２の回折格子部６
を形成する。そして、これら透明基板２ａ、２ｂの回折格子部が形成されていない他方の
主面同士を、偏光フィルム８を挟んで光学接着剤により貼り合わせて構成するようにして
いる。偏光フィルム８は、例えばポリビニルアルコール（ＰＶＡ（polyvinyl alcohol）
）により構成され、出射面側からの戻り光を偏光して入射面側に戻るのを防止するように
している。このように構成すれば、偏光手段により戻り光が入射面側に入射されるのを防
止できるので、戻り光が入射光と干渉するのを防止することができる。 FIG. 9 is a diagram schematically showing the structure of a two-wavelength diffraction grating according to the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same site | part as FIG. 1, and detailed description is abbreviate | omitted.
The two-wavelength diffraction grating 30 shown in FIGS. 9A and 9B forms the first diffraction grating portion 5 on one surface of the transparent substrate 2a and the second diffraction grating 30 on one surface of the transparent substrate 2b. Diffraction grating part 6
Form. The other principal surfaces of the transparent substrates 2a and 2b where the diffraction grating portion is not formed are bonded to each other with an optical adhesive with the polarizing film 8 interposed therebetween. The polarizing film 8 is, for example, polyvinyl alcohol (PVA (polyvinyl alcohol)).
The return light from the exit surface side is polarized to prevent returning to the entrance surface side. With this configuration, the return light can be prevented from being incident on the incident surface side by the polarizing means, so that the return light can be prevented from interfering with the incident light.

図１０は本発明の第４の実施形態に係る２波長対応回折格子の構造例を示した図であり
、（ａ）（ｃ）は夫々断面図、（ｂ）は上面図である。なお、図１と同一部位には同一符
号を付して詳細な説明は省略する。
この図１０（ａ）（ｂ）に示す２波長対応回折格子４０は、透明基板２ａの一方の主面
上に第１の回折格子部５を形成すると共に、透明基板２ｂの一方側の主面上に第２の回折
格子部６を形成する。そして透明基板２ａと透明基板２ｂとの夫々回折格子が形成されて
いない他方の主面同士を、偏光フィルム８を介して貼り合わせるようにしている。このと
き、透明基板２ａ、２ｂと偏光フィルム８とは、図１０（ｂ）に示すように回折格子の光
学領域外となる外周部分だけを光学接着剤４１により接着して固定し、回折格子の光学領
域部分については光学接着剤を塗布することなく、回折格子部５、６と偏光フィルム８と
の間にギャップ（隙間）を設けるようにしている。このように構成すると、回折格子の光
学領域に光学接着剤４１を塗布する必要がないので、光学接着剤４１の厚みムラにより光
学特性が劣化するといったことを防止することができる。
また図１０（ｃ）に示す２波長対応回折格子５０は、透明基板２ａ、２ｂの夫々回折格
子が形成されている主面同士を、偏光フィルム８を介して貼り合わせるようにしている。
そして、この場合も回折格子の光学領域外となる外周部分だけを光学接着剤４１により接
着して固定し、回折格子の光学領域部分については回折格子部５、６と偏光フィルム８と
の間にギャップ（隙間）を設けるようにしている。このように構成した場合も、光学接着
剤４１の厚みムラにより光学特性が劣化するといったことを防止することができる。 10A and 10B are diagrams showing a structure example of a two-wavelength diffraction grating according to the fourth embodiment of the present invention. FIGS. 10A and 10C are cross-sectional views, and FIG. 10B is a top view. In addition, the same code | symbol is attached | subjected to the same site | part as FIG. 1, and detailed description is abbreviate | omitted.
The two-wavelength-corresponding diffraction grating 40 shown in FIGS. 10 (a) and 10 (b) forms the first diffraction grating portion 5 on one main surface of the transparent substrate 2a and the main surface on one side of the transparent substrate 2b. A second diffraction grating portion 6 is formed on the top. The other principal surfaces of the transparent substrate 2a and the transparent substrate 2b on which the diffraction gratings are not formed are bonded to each other via the polarizing film 8. At this time, the transparent substrates 2a and 2b and the polarizing film 8 are fixed by adhering and fixing only the outer peripheral portion outside the optical region of the diffraction grating with the optical adhesive 41 as shown in FIG. The optical region portion is provided with a gap (gap) between the diffraction grating portions 5 and 6 and the polarizing film 8 without applying an optical adhesive. With this configuration, since it is not necessary to apply the optical adhesive 41 to the optical region of the diffraction grating, it is possible to prevent optical characteristics from being deteriorated due to uneven thickness of the optical adhesive 41.
Further, the two-wavelength-corresponding diffraction grating 50 shown in FIG. 10C is configured so that the principal surfaces on which the diffraction gratings of the transparent substrates 2 a and 2 b are formed are bonded to each other through the polarizing film 8.
In this case as well, only the outer peripheral portion outside the optical region of the diffraction grating is adhered and fixed by the optical adhesive 41, and the optical region portion of the diffraction grating is interposed between the diffraction grating portions 5 and 6 and the polarizing film 8. A gap is provided. Also when comprised in this way, it can prevent that an optical characteristic deteriorates by the thickness nonuniformity of the optical adhesive agent 41. FIG.

図１１は本発明の第５の実施形態に係る２波長対応回折格子の構造を模式的に示した図
である。なお、図３と同一部位には同一符号を付して詳細な説明は省略する。
この図１１に示す２波長対応回折格子６０は、前記図３に示した構造の２波長対応回折
格子において、戻り光が入射面側に入射されるのを防止するために透明基板２の入射面側
に偏光フィルム８を光学接着剤により貼り合わせて構成するようにしたものである。この
ように構成すれば、偏光手段により戻り光が入射面側に入射されるのを防止できるので、
戻り光が入射光と干渉するのを防止することができる。なお、本実施の形態では、本発明
に係る偏光手段を有する回折格子の実施例として、樹脂製の偏光手段（偏光フィルム）を
用いて説明したが、これに限らず無機偏光板等の偏光板も適用できることは言うまでもな
い。 FIG. 11 is a diagram schematically showing the structure of a diffraction grating corresponding to two wavelengths according to the fifth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same site | part as FIG. 3, and detailed description is abbreviate | omitted.
The two-wavelength-corresponding diffraction grating 60 shown in FIG. 11 is the two-wavelength-corresponding diffraction grating having the structure shown in FIG. 3 in order to prevent the return light from being incident on the incident surface side. The polarizing film 8 is bonded to the side with an optical adhesive. By configuring in this way, it is possible to prevent the return light from being incident on the incident surface side by the polarizing means.
It is possible to prevent the return light from interfering with the incident light. In this embodiment, the example of the diffraction grating having the polarizing means according to the present invention has been described using the resin polarizing means (polarizing film). However, the present invention is not limited to this, and a polarizing plate such as an inorganic polarizing plate is used. It goes without saying that is also applicable.

なお、本実施の形態では、本発明の回折格子の一例として、異なる２つの波長に対応し
た２波長対応回折格子を例に挙げて説明したが、これはあくまでも一例であり、ガラス透
明基板２の表面上に形成する低屈折率材料３と高屈折率材料４との格子深さを変えること
によって、例えばＢｌｕ−ｒａｙ ＤｉｓｃやＨＤ ＤＶＤ等に用いられる青紫色レーザ
（４０５ｎｍ）を含む波長帯域において、波長依存性の小さい回折格子を実現することが
可能である。 In the present embodiment, as an example of the diffraction grating of the present invention, a two-wavelength compatible diffraction grating corresponding to two different wavelengths has been described as an example. However, this is merely an example, and the glass transparent substrate 2 By changing the grating depth of the low refractive index material 3 and the high refractive index material 4 formed on the surface, for example, in a wavelength band including a blue-violet laser (405 nm) used for Blu-ray Disc, HD DVD, etc. It is possible to realize a diffraction grating with small wavelength dependency.

本発明の第１の実施形態に係る２波長対応回折格子の構造を模式的に示した図。The figure which showed typically the structure of the diffraction grating corresponding to 2 wavelength which concerns on the 1st Embodiment of this invention. 回折格子部のデューティ比と回折効率との関係を示した図。The figure which showed the relationship between the duty ratio of a diffraction grating part, and diffraction efficiency. 本発明の第２の実施形態に係る２波長対応回折格子の構造を模式的に示した図。The figure which showed typically the structure of the diffraction grating corresponding to 2 wavelength which concerns on the 2nd Embodiment of this invention. 図３に示した２波長対応回折格子における波長と回折効率との関係を示した図。The figure which showed the relationship between the wavelength and diffraction efficiency in the diffraction grating corresponding to 2 wavelengths shown in FIG. 図３に示した２波長対応回折格子の回折格子部を拡大して示した図。The figure which expanded and showed the diffraction grating part of the diffraction grating corresponding to 2 wavelengths shown in FIG. シミュレーション結果を示した図。The figure which showed the simulation result. 本実施形態の２波長対応回折格子の製造方法を示した図。The figure which showed the manufacturing method of the diffraction grating for 2 wavelengths of this embodiment. 本実施形態の２波長対応回折格子を備えた光ピックアップ装置の構成を示した図。The figure which showed the structure of the optical pick-up apparatus provided with the diffraction grating for 2 wavelengths of this embodiment. 本発明の第３の実施形態に係る２波長対応回折格子の構造を模式的に示した図。The figure which showed typically the structure of the diffraction grating corresponding to 2 wavelength which concerns on the 3rd Embodiment of this invention. 本発明の第４の実施形態に係る２波長対応回折格子の構造例を示した図。The figure which showed the structural example of the diffraction grating corresponding to 2 wavelengths which concerns on the 4th Embodiment of this invention. 本発明の第５の実施形態に係る２波長対応回折格子の構造を模式的に示した図。The figure which showed typically the structure of the diffraction grating corresponding to 2 wavelength which concerns on the 5th Embodiment of this invention. 従来の２波長対応回折格子の構造を模式的に示した図。The figure which showed typically the structure of the conventional 2 wavelength corresponding | compatible diffraction grating.

符号の説明Explanation of symbols

１、２０…２波長対応回折格子、２…ガラス透明基板、３、３ａ、３ｂ…低屈折率材料
、４、４ａ、４ｂ…高屈折率材料、５…第１の回折格子部、６…第２の回折格子部、７…
感光層、１０…半導体レーザ、２１…ビームスプリッタ、２２…コリメートレンズ、２３
…対物レンズ、２４…光検出器、３０…光ディスク、４１…フォトレジスト、４２、４３
…マスク DESCRIPTION OF SYMBOLS 1,20 ... 2 wavelength corresponding | compatible diffraction grating, 2 ... Glass transparent substrate, 3, 3a, 3b ... Low refractive index material, 4, 4a, 4b ... High refractive index material, 5 ... 1st diffraction grating part, 6 ... 1st 2 diffraction grating sections, 7...
Photosensitive layer, 10 ... semiconductor laser, 21 ... beam splitter, 22 ... collimating lens, 23
... objective lens, 24 ... photodetector, 30 ... optical disc, 41 ... photoresist, 42, 43
…mask

Claims (6)

波長が異なる複数の光のうち、少なくとも一つの波長の光が入射する回折格子であって
、
透明基材と、
前記透明基材の両面上に夫々形成され、第１の屈折率を有する第１の屈折率材料、該第
１の屈折率材料とは異なる第２の屈折率を有する第２の屈折率材料、及び前記第２の屈折
率材料上に形成される感光層を有し、前記第１の屈折率材料と前記第２の屈折率材料とが
交互に配置された第１及び第２の回折格子部と、
を備え、
前記第１の回折格子部は、前記第１の波長に対して回折効率が所定の値で、且つ、前記
第２の波長に対して前記第１の屈折率材料と前記第２の屈折率材料との位相差が２πとな
るように、前記第１及び第２の屈折率材料の格子深さが設定され、前記第２の回折格子部
は、前記第２の波長に対して回折効率が所定の値で、且つ、前記第１の波長に対して前記
第１の屈折率材料と前記第２の屈折率材料との位相差が２πとなるように、前記第１及び
第２の屈折率材料の格子深さが設定されていることを特徴とする回折格子。 A diffraction grating on which light of at least one wavelength is incident among a plurality of lights having different wavelengths,
A transparent substrate;
A first refractive index material having a first refractive index and a second refractive index material having a second refractive index different from the first refractive index material, each formed on both surfaces of the transparent substrate; And a photosensitive layer formed on the second refractive index material, and the first and second diffraction grating portions in which the first refractive index material and the second refractive index material are alternately arranged. When,
With
The first diffraction grating portion has a predetermined value of diffraction efficiency with respect to the first wavelength, and the first refractive index material and the second refractive index material with respect to the second wavelength. The grating depths of the first and second refractive index materials are set so that the phase difference between the first and second refractive index materials becomes 2π, and the second diffraction grating portion has a predetermined diffraction efficiency with respect to the second wavelength. And the first and second refractive index materials so that the phase difference between the first refractive index material and the second refractive index material is 2π with respect to the first wavelength. A diffraction grating characterized in that the grating depth is set. 波長が異なる複数の光のうち、少なくとも一つの波長の光が入射する回折格子であって
、
透明基材と、
第１の屈折率を有する第１の屈折率材料、該第１の屈折率材料とは異なる第２の屈折率
を有する第２の屈折率材料、及び前記第２の屈折率材料上に形成される感光層を有し、前
記透明基材の表面上に前記第１の屈折率材料と前記第２の屈折率材料とが交互に配置され
た回折格子部と、を備え、
前記第１及び第２の波長を含む波長帯域における回折効率が所定の値になるように、前
記第１及び第２の屈折率材料の格子深さが夫々設定されていることを特徴とする回折格子
。 A diffraction grating on which light of at least one wavelength is incident among a plurality of lights having different wavelengths,
A transparent substrate;
A first refractive index material having a first refractive index, a second refractive index material having a second refractive index different from the first refractive index material, and the second refractive index material. And a diffraction grating portion in which the first refractive index material and the second refractive index material are alternately arranged on the surface of the transparent substrate,
Diffraction characterized in that the grating depths of the first and second refractive index materials are set so that the diffraction efficiency in a wavelength band including the first and second wavelengths has a predetermined value. lattice. 前記第１の屈折率材料をアクリル系樹脂、前記第２の屈折率材料を誘電体であるＴｉＯ
2またはＴａ2Ｏ5としたことを特徴とする請求項１又は２に記載の回折格子。 The first refractive index material is an acrylic resin, and the second refractive index material is a dielectric TiO.
The diffraction grating according to claim 1, wherein the diffraction grating is 2 or Ta 2 O 5 . 前記第１の屈折率材料を感光性ポリシラン樹脂、前記第２の屈折率材料を誘電体である
ＴｉＯ2またはＴａ2Ｏ5としたことを特徴とする請求項１又は２に記載の回折格子。 3. The diffraction grating according to claim 1, wherein the first refractive index material is a photosensitive polysilane resin, and the second refractive index material is a dielectric TiO 2 or Ta 2 O 5 . 透明基板の表面上に高屈折率材料４を成膜する工程と、
前記高屈折率材料を成膜した前記透明基板全体に低屈折率材料を成膜する工程と、
前記高屈折率材料上に成膜した前記低屈折率材料に紫外線を照射して前記低屈折率材料
とは屈折率の異なる感光層に変化させる工程と、
からなることを特徴とする回折格子の製造方法。 Forming a high refractive index material 4 on the surface of the transparent substrate;
Forming a low refractive index material on the entire transparent substrate on which the high refractive index material is formed;
Irradiating the low refractive index material deposited on the high refractive index material with ultraviolet rays to change the photosensitive layer having a refractive index different from that of the low refractive index material;
A method for manufacturing a diffraction grating, comprising: 少なくとも２つの異なる波長の光を出射する光源と、前記光源から出射光を光記録媒体
に集光する対物レンズとを備え、光記録媒体に情報の記録又は／及び再生を行う光ピック
アップ装置であって、
前記光源と前記対物レンズとの間の光路中に、請求項１乃至４の何れか１項に記載の回
折格子が配置されていることを特徴とする光ピックアップ装置。 An optical pickup apparatus that includes a light source that emits light of at least two different wavelengths and an objective lens that condenses the light emitted from the light source onto an optical recording medium, and records or / and reproduces information on the optical recording medium. And
5. The optical pickup device according to claim 1, wherein the diffraction grating according to claim 1 is arranged in an optical path between the light source and the objective lens.
JP2006164361A 2006-06-14 2006-06-14 Diffraction grating, its manufacturing method, and optical pickup device Withdrawn JP2007334975A (en)

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Publication number Priority date Publication date Assignee Title
KR100894321B1 (en) * 2008-01-29 2009-04-24 도시바삼성스토리지테크놀러지코리아 주식회사 Grating device and optical pickup apparatus using the same
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Publication number Priority date Publication date Assignee Title
JP2014209237A (en) * 2008-01-21 2014-11-06 プライムセンス リミテッド Optical designs for zero order reduction
KR100894321B1 (en) * 2008-01-29 2009-04-24 도시바삼성스토리지테크놀러지코리아 주식회사 Grating device and optical pickup apparatus using the same
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