JP2012177797A - Polarizer - Google Patents

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JP2012177797A
JP2012177797A JP2011040704A JP2011040704A JP2012177797A JP 2012177797 A JP2012177797 A JP 2012177797A JP 2011040704 A JP2011040704 A JP 2011040704A JP 2011040704 A JP2011040704 A JP 2011040704A JP 2012177797 A JP2012177797 A JP 2012177797A
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metal layer
intermediate layer
wave
periodic structure
thickness
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JP5837310B2 (en
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Kazuo Shiraishi
和男 白石
Yuta Inagawa
雄太 稲川
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Utsunomiya University
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Abstract

PROBLEM TO BE SOLVED: To provide a polarizer which is easily manufactured with a large area and is capable of achieving both polarization splitting and reflection prevention, in particular, in a short-wavelength region and allows improvement of characteristics in a mid-infrared region, and to provide a manufacturing method thereof and an optical module.SOLUTION: The polarizer is configured to include: a substrate 11 having a periodic structure where a unit structure continuously changing the occupancy with respect to an electromagnetic wave impinging on a surface of the substrate at a prescribed angle is repeated with a period shorter than a wavelength of the electromagnetic wave; a metallic layer 12 provided on a surface of the periodic structure; an intermediate layer 13 provided on the surface of the substrate 11; and a metallic layer 14 provided on a surface of the intermediate layer 13. It is preferable that a cross section of the periodic structure has a triangular wave shape or a sine wave shape.

Description

本発明は、偏光子、その製造方法及び光モジュールに関する。   The present invention relates to a polarizer, a manufacturing method thereof, and an optical module.

偏光子は、ある特定の偏光のみを透過させる素子である。光通信、光情報処理又は光センシング等の分野では、小型で、消光比が高く、使用波長範囲が広く、耐環境性に優れ、量産性にも優れた偏光子が要求されている。   A polarizer is an element that transmits only certain polarized light. In the fields of optical communication, optical information processing, or optical sensing, there is a demand for a polarizer that is small, has a high extinction ratio, has a wide wavelength range, is excellent in environmental resistance, and is excellent in mass productivity.

例えば、テラヘルツ帯及び近赤外領域用偏光子として、特許文献１では、サブ波長格子（Ｓｕｂｗａｖｅｌｅｎｇｔｈ ｇｒａｔｉｎｇ：ＳＷＧ）を用いた偏光子が提案されている。   For example, as a polarizer for the terahertz band and the near infrared region, Patent Document 1 proposes a polarizer using a subwavelength grating (SWG).

特開２０１０−２５６８４０号公報JP 2010-256840 A

上記特許文献１に記載の偏光子は、主に、テラヘルツ領域から遠赤外領域を対象としていたが、中赤外及び近赤外領域の特性を向上させる余地がある。   The polarizer described in Patent Document 1 mainly targets the far-infrared region from the terahertz region, but there is room for improving the characteristics of the mid-infrared region and the near-infrared region.

本発明は、上記課題を解決するためになされたものであって、その目的は、平易な作製プロセスによりコストが大幅に削減できるとともに、かつ広開口の偏光子を作製することが容易で、中赤外及び近赤外領域における特性を向上させることができる偏光子、その製造方法及び光モジュールを提供することにある。   The present invention has been made in order to solve the above-described problems, and its object is to greatly reduce the cost by a simple manufacturing process and to easily manufacture a wide aperture polarizer. An object of the present invention is to provide a polarizer capable of improving characteristics in the infrared and near-infrared regions, a manufacturing method thereof, and an optical module.

（１）上記課題を解決するための本発明に係る偏光子は、基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化する単位構造をλ（入射する電磁波の波長）より小さな周期で繰り返す周期構造を有した基材と、前記周期構造の表面に中間層を介して複数設けられた金属層と、を有することを特徴とする。   (1) The polarizer according to the present invention for solving the above-mentioned problem is a unit structure whose occupancy continuously changes with respect to electromagnetic waves incident on the substrate surface at a predetermined angle λ (wavelength of incident electromagnetic waves). ) It has a base material having a periodic structure that repeats with a smaller period, and a plurality of metal layers provided on the surface of the periodic structure via an intermediate layer.

なお、例えば、本発明の偏光子において、前記単位構造の周期が、λ（１μｍ≦λ≦２０μｍ）／ｎ（前記中間層の屈折率）以下である、ことが好ましい。また、前記中間層の厚さが０．０８λ〜０．２５λであること、前記金属層が三層であり、前記周期構造の断面が正弦波形状である場合に、前記中間層の厚さが０．２λ〜０．５８λであることが好ましい。さらに、前記金属層が三層であり、前記周期構造の断面が三角波形状である場合に、前記中間層の厚さが０．２５λ〜０．７λであることが好ましい。   For example, in the polarizer of the present invention, the period of the unit structure is preferably λ (1 μm ≦ λ ≦ 20 μm) / n (refractive index of the intermediate layer) or less. Further, when the thickness of the intermediate layer is 0.08λ to 0.25λ, the metal layer is three layers, and the cross section of the periodic structure is sinusoidal, the thickness of the intermediate layer is It is preferably 0.2λ to 0.58λ. Furthermore, when the metal layer has three layers and the cross section of the periodic structure has a triangular wave shape, the thickness of the intermediate layer is preferably 0.25λ to 0.7λ.

（２）本発明の偏光子において、前記周期構造の断面が三角波形状又は正弦波形状であることが好ましい。   (2) In the polarizer of the present invention, it is preferable that a cross section of the periodic structure has a triangular wave shape or a sine wave shape.

（３）本発明の偏光子において、前記金属層が二層であり、前記中間層の厚さが０より大きくλ／ｎ以下であることが好ましい。   (3) In the polarizer of the present invention, it is preferable that the metal layer has two layers, and the thickness of the intermediate layer is greater than 0 and not more than λ / n.

（４）上記課題を解決するための本発明に係る偏光子の製造方法は、基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化する単位構造をλ（入射する電磁波の波長）より小さな周期で繰り返す周期構造を前記基材面に形成する工程と、前記周期構造の表面に金属層を形成する工程と、前記金属層の表面に中間層を形成する工程と、前記中間層の表面に金属層を形成する工程とを有することを特徴とする。   (4) In the method for manufacturing a polarizer according to the present invention for solving the above-described problem, a unit structure whose occupancy continuously changes with respect to an electromagnetic wave incident on the substrate surface at a predetermined angle is λ (incident. Forming a periodic structure on the substrate surface that repeats with a period smaller than the wavelength of the electromagnetic wave, forming a metal layer on the surface of the periodic structure, forming an intermediate layer on the surface of the metal layer, And a step of forming a metal layer on the surface of the intermediate layer.

（５）本発明の偏光子の製造方法において、前記周期構造の断面が三角波形状又は正弦波形状であることが好ましい。   (5) In the manufacturing method of the polarizer of the present invention, it is preferable that the section of the periodic structure has a triangular wave shape or a sine wave shape.

（６）上記課題を解決するための本発明に係る光モジュールは、上記本発明に係る偏光子を用いたことを特徴とする。   (6) An optical module according to the present invention for solving the above-described problems uses the polarizer according to the present invention.

本発明の偏光子によれば、基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化する単位構造をλ（入射する電磁波の波長）より小さな周期で繰り返す周期構造を有した基材と、前記周期構造の表面に中間層を介して複数設けられた金属層とを有するので、中赤外領域における特性を向上させることができる。   According to the polarizer of the present invention, the periodic structure in which the unit structure whose occupancy continuously changes with respect to the electromagnetic wave incident on the substrate surface at a predetermined angle is repeated with a period smaller than λ (the wavelength of the incident electromagnetic wave). Since it has the base material which had and the metal layer provided in multiple numbers via the intermediate | middle layer on the surface of the said periodic structure, the characteristic in a mid-infrared area | region can be improved.

本発明の偏光子の製造方法によれば、基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化する単位構造をλ（入射する電磁波の波長）より小さな周期で繰り返す周期構造を前記基材面に形成する工程と、前記周期構造の表面に金属層を形成する工程と、前記金属層の表面に中間層を形成する工程と、前記中間層の表面に金属層を形成する工程とを有するので、従来のような多層構造を形成した後に切り出す方法よりも効率的に製造することができる。   According to the method for manufacturing a polarizer of the present invention, a unit structure whose occupancy continuously changes with respect to electromagnetic waves incident on a substrate surface at a predetermined angle is repeated with a period smaller than λ (wavelength of incident electromagnetic waves). A step of forming a periodic structure on the surface of the substrate, a step of forming a metal layer on the surface of the periodic structure, a step of forming an intermediate layer on the surface of the metal layer, and a metal layer on the surface of the intermediate layer. Therefore, it can be manufactured more efficiently than a conventional method of cutting out after forming a multilayer structure.

本発明に係る偏光子の一例とその使用態様を示す全体図である。It is a general view which shows an example of the polarizer which concerns on this invention, and its usage condition. 三角波形状の断面を有し、その三角波形状の表面に金属層が形成されている偏光子（サブ波長格子）の例を示す拡大図である。It is an enlarged view which shows the example of the polarizer (subwavelength grating) which has a triangular wave-shaped cross section and the metal layer is formed in the surface of the triangular wave shape. 正弦波形状の断面を有し、その正弦波形状の表面に金属層が形成されている偏光子（サブ波長格子）の例を示す拡大図である。It is an enlarged view which shows the example of the polarizer (subwavelength grating) which has a cross section of a sine wave shape and the metal layer is formed in the surface of the sine wave shape. 周期構造の占有率（充填率）についての説明図である。It is explanatory drawing about the occupation rate (filling rate) of a periodic structure. 波長λが１μｍ、周期構造の周期Λが２５０ｎｍ、アスペクト比ｈ／Λが１、金属層Ａｌの厚さの合計が１８ｎｍである場合の、中間層の厚さＤの変化に対するＴＥ波とＴＭ波の透過損失特性を厳密結合波解析（ＲＣＷＡ）法を用いた数値解析により求めたグラフである。When the wavelength λ is 1 μm, the period Λ of the periodic structure is 250 nm, the aspect ratio h / Λ is 1, and the total thickness of the metal layer Al is 18 nm, the TE wave and the TM wave with respect to the change in the thickness D of the intermediate layer It is the graph which calculated | required the transmission loss characteristic of this by the numerical analysis using the exact coupling wave analysis (RCWA) method. 単層格子（金属層が一層の格子）の場合の表面および裏面に励起される表面プラズモンを概念的に示す図である。It is a figure which shows notionally the surface plasmon excited by the surface and the back surface in the case of a single layer grating | lattice (a grating | lattice with one metal layer). 二重格子（金属層が二層の格子）で中間層の厚さＤが小さい場合の表面および裏面に励起される表面プラズモンと、各金属層の中間層側に励起される表面プラズモンを概念的に示す図である。Conceptually the surface plasmons excited on the front and back surfaces when the thickness D of the intermediate layer is small in a double lattice (lattice metal layer lattice) and the surface plasmons excited on the intermediate layer side of each metal layer FIG. 一層当りの金属層の膜厚が十分小さい二重格子で、かつ中間層の厚さＤが十分大きい場合の表面および裏面に励起される表面プラズモンと、各金属層の中間層側に励起される表面プラズモンを概念的に示す図である。Surface plasmons excited on the front and back surfaces when the thickness of the metal layer per layer is sufficiently small and the thickness D of the intermediate layer is sufficiently large, and excited on the intermediate layer side of each metal layer It is a figure which shows a surface plasmon conceptually. 波長λが１０μｍ、正弦波形状の断面を有し、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、中間層の厚さＤが０（単層格子）と１．５μｍ（二重格子）である場合の、金属層が一層の場合と二層の場合の、ＲＣＷＡ法を用いた数値解析により求めた、金属層の厚さに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。The wavelength λ is 10 μm, it has a sinusoidal cross section, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the thickness D of the intermediate layer is 0 (single-layer grating) and 1.5 μm ( The transmission loss characteristics of TE wave and TM wave with respect to the thickness of the metal layer, obtained by numerical analysis using the RCWA method, when the metal layer is a single layer and when the metal layer is two layers are shown. It is a graph. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、二重格子を構成する金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。Numerical value using the RCWA method when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness t of the metal layers constituting the double grating is 18 nm. It is a graph which shows the transmission loss characteristic of the TE wave and TM wave with respect to the thickness D of the intermediate | middle layer calculated | required by analysis. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、四重格子（金属層が四層）を構成する金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。When the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness t of the metal layers constituting the quadruple lattice (four metal layers) is 18 nm. It is a graph which shows the transmission loss characteristic of the TE wave and TM wave with respect to the thickness D of the intermediate | middle layer calculated | required by the numerical analysis using the RCWA method. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、二重格子を構成する金属層の合計の厚さｔが１８ｎｍ、中間層の厚さＤが１．５μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、アスペクト比ｈ／Λに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。The RCWA method in which the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the total thickness t of the metal layers constituting the double grating is 18 nm, and the thickness D of the intermediate layer is 1.5 μm. It is a graph which shows the transmission loss characteristic of the TE wave and TM wave with respect to aspect ratio h / Λ calculated | required by the used numerical analysis. 波長λが１０μｍ、三角波形状の断面を有し、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、中間層の厚さＤが０（単層格子）と１．５μｍ（二重格子）である場合の、ＲＣＷＡ法を用いた数値解析により求めた、金属層の合計の厚さｔに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。The wavelength λ is 10 μm, it has a triangular wave cross section, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the thickness D of the intermediate layer is 0 (single-layer grating) and 1.5 μm (two It is a graph which shows the transmission loss characteristic of the TE wave and TM wave with respect to the total thickness t of a metal layer calculated | required by the numerical analysis using the RCWA method in the case of a double grating | lattice. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、三重格子を構成する金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。Numerical analysis using the RCWA method when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness t of the metal layers constituting the triple lattice is 18 nm. 5 is a graph showing transmission loss characteristics of TE wave and TM wave with respect to the thickness D of the intermediate layer, obtained by 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、三重格子を構成する金属層の合計の厚さｔが１８ｎｍ、中間層の合計の厚さＤが２．５μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、アスペクト比ｈ／Λに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。RCWA method when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the total thickness t of the metal layers constituting the triple lattice is 18 nm, and the total thickness D of the intermediate layer is 2.5 μm. 6 is a graph showing transmission loss characteristics of a TE wave and a TM wave with respect to an aspect ratio h / Λ obtained by a numerical analysis using a wave. 波長λが１０μｍ、正弦波形状の断面を有し、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、中間層の合計の厚さＤが２．５μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、金属層の合計の厚さｔに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。RCWA when the wavelength λ is 10 μm, the cross-section is sinusoidal, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness D of the intermediate layer is 2.5 μm It is a graph which shows the transmission loss characteristic of the TE wave and TM wave with respect to the total thickness t of the metal layer calculated | required by the numerical analysis using a method. 波長λが１０μｍ、三角波形状の断面を有し、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、中間層の合計の厚さＤが２．５μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、金属層の合計の厚さｔに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。RCWA method in which the wavelength λ is 10 μm, the section has a triangular wave shape, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness D of the intermediate layer is 2.5 μm 6 is a graph showing the transmission loss characteristics of TE wave and TM wave with respect to the total thickness t of the metal layer, which is obtained by numerical analysis using the wave length. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、四重格子を構成する中間層の合計の厚さＤが２．５μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、金属層Ａｌの合計の厚さｔに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。The RCWA method is used when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness D of the intermediate layer constituting the quadruple grating is 2.5 μm. It is a graph which shows the transmission loss characteristic of the TE wave and TM wave with respect to the total thickness t of the metal layer Al calculated | required by numerical analysis. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、四重格子を構成する中間層の合計の厚さＤが３．５μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、金属層Ａｌの合計の厚さｔに対するＴＥ波とＴＭ波の透過損失特性を示すグラフである。The RCWA method is used when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness D of the intermediate layer constituting the quadruple grating is 3.5 μm. It is a graph which shows the transmission loss characteristic of the TE wave and TM wave with respect to the total thickness t of the metal layer Al calculated | required by numerical analysis. 周期構造の周期Λ＝２．５μｍ、構造のアスペクト比ｈ／Λ＝１、金属層Ａｌの合計の厚さｔ＝２０ｎｍ、中間層の厚さがＤ＝１．５μｍである二重格子の、ＲＣＷＡ法を用いた数値解析により求めた、入射波長に対する透過損失特性を示すグラフである。A double lattice in which the period Λ = 2.5 μm of the periodic structure, the aspect ratio h / Λ = 1 of the structure, the total thickness t = 20 nm of the metal layer Al, and the thickness of the intermediate layer D = 1.5 μm, It is a graph which shows the transmission loss characteristic with respect to the incident wavelength calculated | required by the numerical analysis using RCWA method. 周期構造の周期Λ＝２．５μｍ、構造のアスペクト比ｈ／Λ＝１、金属層Ａｌの合計の厚さｔ＝２０ｎｍ、中間層の合計の厚さがＤ＝２．５μｍである三重格子の、ＲＣＷＡ法を用いた数値解析により求めた、入射波長に対する透過損失特性を示すグラフである。A triple lattice in which the period Λ = 2.5 μm of the periodic structure, the aspect ratio h / Λ = 1 of the structure, the total thickness t = 20 nm of the metal layer Al, and the total thickness of the intermediate layer D = 2.5 μm It is a graph which shows the transmission loss characteristic with respect to the incident wavelength calculated | required by the numerical analysis using the RCWA method. 正弦波形状の断面を有し、その正弦波形状の表面に金属層が形成されている偏光子（サブ波長格子）の例を示す拡大図である。It is an enlarged view which shows the example of the polarizer (subwavelength grating) which has a cross section of a sine wave shape and the metal layer is formed in the surface of the sine wave shape. 波長λが１０μｍ、周期構造の周期Λが２．５μ、アスペクト比ｈ／Λが１、金属層の合計の厚さｔすなわちｔ１＋ｔ２が２０ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、各金属層の厚さに対する透過損失特性を示すグラフである。Obtained by numerical analysis using the RCWA method when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μ, the aspect ratio h / Λ is 1, and the total thickness t of the metal layer, that is, t1 + t2 is 20 nm. It is a graph which shows the transmission loss characteristic with respect to the thickness of each metal layer. 波長λが２０μｍ、周期構造の周期Λが５μｍ、アスペクト比ｈ／Λが１、金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の厚さＤに対する透過損失特性を示すグラフである。When the wavelength λ is 20 μm, the period Λ of the periodic structure is 5 μm, the aspect ratio h / Λ is 1, and the total thickness t of the metal layer is 18 nm, the intermediate layer is obtained by numerical analysis using the RCWA method. 5 is a graph showing transmission loss characteristics with respect to thickness D. 波長λが１μｍ、周期構造の周期Λが２５０ｎｍ、アスペクトｈ／Λが１、金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の合計の厚さＤに対する透過損失特性を示すグラフである。Sum of intermediate layers obtained by numerical analysis using RCWA method when wavelength λ is 1 μm, period Λ of periodic structure is 250 nm, aspect ratio h / Λ is 1, and total thickness t of metal layers is 18 nm It is a graph which shows the transmission loss characteristic with respect to the thickness D of the. 波長λが２０μｍ、周期構造の周期Λが５μｍ、アスペクト比ｈ／Λが１、金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の合計の厚さＤに対する透過損失特性を示すグラフである。When the wavelength λ is 20 μm, the period Λ of the periodic structure is 5 μm, the aspect ratio h / Λ is 1, and the total thickness t of the metal layer is 18 nm, the intermediate layer is obtained by numerical analysis using the RCWA method. 5 is a graph showing transmission loss characteristics with respect to total thickness D. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の厚さＤに対する透過損失特性を示すグラフである。An intermediate value obtained by numerical analysis using the RCWA method when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness t of the metal layer is 18 nm. It is a graph which shows the transmission loss characteristic with respect to the thickness D of a layer. 波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、金属層の合計の厚さｔが１８ｎｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層の厚さＤに対する透過損失特性を示すグラフである。An intermediate value obtained by numerical analysis using the RCWA method when the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, and the total thickness t of the metal layer is 18 nm. It is a graph which shows the transmission loss characteristic with respect to the thickness D of a layer.

次に、本発明の実施の形態について説明する。なお、本発明は、その技術的思想を含む範囲を包含し、以下に示す説明や図面等に限定されない。   Next, an embodiment of the present invention will be described. In addition, this invention includes the range including the technical idea, and is not limited to description, drawing, etc. which are shown below.

［偏光子］
本発明の偏光子１０は、図１に示すように、入射する電磁波に対する占有率が連続的に変化する単位構造を繰り返す周期構造を有する基材１１と、周期構造の表面に設けられた金属層１２と、この金属層１２の上に設けられた中間層１３と、この中間層１３の上に設けられた金属層１４と、を有している。 [Polarizer]
As shown in FIG. 1, the polarizer 10 of the present invention includes a base material 11 having a periodic structure that repeats a unit structure in which an occupation ratio to incident electromagnetic waves continuously changes, and a metal layer provided on the surface of the periodic structure. 12, an intermediate layer 13 provided on the metal layer 12, and a metal layer 14 provided on the intermediate layer 13.

基材１１の表面に設けられた周期構造は、図２に断面を示すように、断面が三角形の溝（Ｇｒｏｏｖｅ）である単位構造を溝の長手方向に対して垂直な方向に隣接させて繰り返す構造、すなわち三角波形状となっている。なお、この例では、単位構造の断面形状を三角波形状としているが、入射する電磁波に対して占有率が連続的に変化する単位構造を繰り返す周期構造であれば、例えば図３に示すように、単位構造の断面形状を正弦波形状としてもよい。あるいは、単位構造の断面形状を矩形波形状としてもよい。   The periodic structure provided on the surface of the base material 11 is repeated by adjoining a unit structure, which is a groove having a triangular cross section, in a direction perpendicular to the longitudinal direction of the groove, as shown in FIG. It has a structure, that is, a triangular wave shape. In this example, the cross-sectional shape of the unit structure is a triangular wave shape, but as long as the periodic structure repeats the unit structure in which the occupation ratio continuously changes with respect to the incident electromagnetic wave, for example, as shown in FIG. The cross-sectional shape of the unit structure may be a sine wave shape. Alternatively, the cross-sectional shape of the unit structure may be a rectangular wave shape.

この偏光子１０は、図１に示すように、周期構造が形成された面に所定の角度で電磁波（光）が入射波として入射した場合に、その周期構造に平行な偏波成分を反射し、垂直な偏波成分を透過させる。すなわち、電界の偏光方向が図１のｘ方向(周期構造に垂直)であるＴＭ波は、表面プラズマ波を介して金属層を低損失で透過し、電界がｙ方向の偏光方向(周期構造に平行)を持つＴＥ波は、金属層により吸収、反射され、ＴＥ波の透過損失は大きくなる（高透過損失）。   As shown in FIG. 1, when an electromagnetic wave (light) is incident as an incident wave at a predetermined angle on the surface on which the periodic structure is formed, the polarizer 10 reflects a polarization component parallel to the periodic structure. Transmits the vertical polarization component. That is, the TM wave having the polarization direction of the electric field in the x direction (perpendicular to the periodic structure) in FIG. The TE wave having (parallel) is absorbed and reflected by the metal layer, and the TE wave transmission loss increases (high transmission loss).

なお、電磁波（光）は進行方向と垂直に振動する横波である。また、入射角は入射波の方向と基材面の法線方向とがなす角度である。さらに、入射面は入射波の方向と基材面の法線方向を含む平面である。また、図１にも示したように、電界の向きが周期構造（格子）の溝方向に平行な電磁波をＴＥ（Ｔｒａｎｓｖｅｒｓｅ Ｅｌｅｃｔｒｉｃ ｗａｖｅ）波、格子の溝方向に垂直な電磁波をＴＭ（Ｔｒａｎｓｖｅｒｓｅ Ｍａｇｎｅｔｉｃ ｗａｖｅ）波と呼ぶ。本発明のＴＥ透過損失とＴＭ透過損失とは、上記のＴＥ波やＴＭ波が偏光子１を透過する際の損失（単位「ｄＢ」による表記）である。   Electromagnetic waves (light) are transverse waves that vibrate perpendicular to the traveling direction. The incident angle is an angle formed by the direction of the incident wave and the normal direction of the substrate surface. Further, the incident surface is a plane including the direction of the incident wave and the normal direction of the substrate surface. In addition, as shown in FIG. 1, an electromagnetic wave whose electric field direction is parallel to the groove direction of the periodic structure (lattice) is a TE (Transverse Electric wave) wave, and an electromagnetic wave perpendicular to the groove direction of the grating is TM (Transverse Magnetic wave). ) Call a wave. The TE transmission loss and TM transmission loss of the present invention are losses (notation in units of “dB”) when the TE wave or TM wave passes through the polarizer 1.

以下、本発明の構成について詳しく説明する。   Hereinafter, the configuration of the present invention will be described in detail.

（基材）
基材１１は、基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化する単位構造を繰り返す周期構造を有している。 (Base material)
The base material 11 has a periodic structure that repeats a unit structure in which the occupation ratio continuously changes with respect to electromagnetic waves incident on the base material surface at a predetermined angle.

周期構造は、図１、図２及び図３に示すように、一定の単位構造が周期的に繰り返される構造であり、基材１１は、そうした周期構造が基材面に形成されている。周期的に繰り返す単位構造は、基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化するものである。   As shown in FIGS. 1, 2 and 3, the periodic structure is a structure in which a certain unit structure is periodically repeated, and the base material 11 has such a periodic structure formed on the base material surface. The unit structure that repeats periodically is one in which the occupation ratio changes continuously with respect to electromagnetic waves incident on the substrate surface at a predetermined angle.

また、基材１１の基材面の全面には、図１及び図２に示すように、Ａｌ等からなる金属層１２が形成されており、この金属層１２の上には、Ｓｉや石英等などの透明体からなる中間層１３が形成されており、さらに、この中間層１３の上には、Ａｌ等からなる金属層１４が形成されている。同様に、図３に示す基材２１の基材面の全面には、Ａｌ等からなる金属層２２が形成されており、この金属層２２の上には、Ｓｉや石英等などの透明体等からなる中間層２３が形成されており、さらに、この中間層２３の上には、Ａｌ等からなる金属層２４が形成されている。   Further, as shown in FIGS. 1 and 2, a metal layer 12 made of Al or the like is formed on the entire surface of the substrate 11, and Si, quartz, or the like is formed on the metal layer 12. An intermediate layer 13 made of a transparent material such as Al is formed, and a metal layer 14 made of Al or the like is formed on the intermediate layer 13. Similarly, a metal layer 22 made of Al or the like is formed on the entire surface of the substrate surface of the substrate 21 shown in FIG. 3, and a transparent body such as Si or quartz is formed on the metal layer 22. An intermediate layer 23 made of is formed, and a metal layer 24 made of Al or the like is formed on the intermediate layer 23.

ここで、「基材面に所定の角度で入射する電磁波」とは、所定の入射角（入射波の方向と基材面の法線方向とがなす角度）で基材面に入射するものであれば、図１に示すように必ずしも法線方向から入射するものでなくてもよく、「所定の角度（入射角）」で基材面に入射するものであればよい。   Here, “electromagnetic wave incident on the substrate surface at a predetermined angle” means that the light is incident on the substrate surface at a predetermined incident angle (an angle formed by the direction of the incident wave and the normal direction of the substrate surface). If there is, it does not necessarily have to be incident from the normal direction as shown in FIG. 1, and may be anything that enters the substrate surface at a “predetermined angle (incident angle)”.

また、「電磁波に対して占有率が連続的に変化する」とは、例えば図４に示すように、基材面の法線方向から入射する電磁波が基材面にそのまま直進透過するとした場合に、電磁波が直進透過する長さの割合ということができる。例えば図４では、電磁波Ｅ３が透過する谷部５は透過長さが最も短い部位であり、電磁波Ｅ１が透過する尾根部４は透過長さが最も長い部位である。「電磁波に対する占有率」とは、このように、電磁波の透過長さが最も長い部位を占有率１００％とし、電磁波の透過長さが最も短い部位を占有率０％として表すものということができる。そして、「占有率が連続的に変化する」とは、図４の例のように、尾根部４から谷部５に向かって占有率（単位構造の長さＬ）が連続的に変化することをいう。なお、「連続的」とは、尾根部４から谷部５に向かう面３が、図２の三角波形状のように直線的に変化する場合や図３の正弦波形状のよう曲線状に変化する場合の他、ガウス形、アークタンジェント形、レイズドコサイン形、放物形等々に連続変化する場合（図示しない）であってもよい。つまり、尾根部４から谷部５に向かって占有率が総じて増加乃至減少する態様のものも含まれてもよい。 Further, “the occupation ratio continuously changes with respect to the electromagnetic wave” means that, for example, as shown in FIG. 4, the electromagnetic wave incident from the normal direction of the base material surface is transmitted straight through the base material surface. It can be said that the ratio of the length that electromagnetic waves pass straight through. For example, in FIG. 4, the trough portion 5 through which the electromagnetic wave E 3 transmits is the portion with the shortest transmission length, and the ridge portion 4 through which the electromagnetic wave E 1 transmits is the portion with the longest transmission length. The “occupancy ratio with respect to electromagnetic waves” can be said to represent a portion with the longest electromagnetic wave transmission length as 100% occupation ratio and a portion with the shortest electromagnetic wave transmission length as 0% occupation ratio. . And “occupation rate changes continuously” means that the occupation rate (unit structure length L) continuously changes from the ridge 4 to the valley 5 as in the example of FIG. Say. Note that “continuous” means that the surface 3 from the ridge 4 to the valley 5 changes linearly like the triangular wave shape of FIG. 2 or changes to a curved shape like the sine wave shape of FIG. In addition to the case, it may be a case of changing continuously (not shown) such as a Gaussian shape, an arctangent shape, a raised cosine shape, a parabolic shape or the like. That is, an aspect in which the occupation ratio generally increases or decreases from the ridge 4 toward the valley 5 may be included.

また、「一定の単位構造が周期的に繰り返される」とは、上記した「電磁波に対して占有率が連続的に変化する単位構造」が一定の周期（ピッチ：図２、図３中のΛ）で繰り返されているものである。その周期は全て一致していることが好ましいが、必ずしも完全に一致していなくてもよい。例えば、周期が不規則であってもある意図を持った設計思想の下で繰り返されているものであればよい。また、構造単位も全て同じ形状であることが好ましいが、完全に一致していなくてもよい。例えば、異なる形状の構造単位がある意図を持った設計思想の下で繰り返されているものであればよい。   Further, “a constant unit structure is periodically repeated” means that the above “unit structure whose occupation ratio continuously changes with respect to electromagnetic waves” has a constant period (pitch: Λ in FIGS. 2 and 3). ) Is repeated. Although it is preferable that the periods are all coincident with each other, it is not always necessary to coincide completely. For example, what is necessary is just to be repeated under the design philosophy with the intention which is irregular even if the period is irregular. Moreover, although it is preferable that all structural units are also the same shape, it does not need to correspond completely. For example, what is necessary is just to be repeated under the design philosophy with the intention that there is a structural unit of a different shape.

基材１１の材質としては、屈折率の実部ｎ及び虚部κが低い材料を用いることが好ましい。屈折率の実部ｎが低いほど優れた偏光特性を見込むことができるとともに、基材１１によるフレネル反射損失を低減することができる。一方、虚部κが小さいほど吸収損失を低減することができる。   As a material of the base material 11, it is preferable to use a material having a low real part n and imaginary part κ of refractive index. The lower the real part n of the refractive index, the better the polarization characteristics can be expected, and the Fresnel reflection loss due to the substrate 11 can be reduced. On the other hand, the absorption loss can be reduced as the imaginary part κ is smaller.

本発明の偏光子１０が対象とする帯域は、波長が１μｍ〜２０μｍ程度の赤外帯域である。この帯域では、基材１１の材質は、例えば低損失材料であるＳｉとし、金属層１２及び金属層１４の材質は、Ａｌとする。例えば波長が１０μｍである場合、Ａｌの光学定数（屈折率の実部ｎと虚部κ）のうち虚部κは８９．８である。また、この場合の金属表面に入射した電磁波の電界の振幅が１／ｅとなる深さである表皮深さδは、１７．７ｎｍとなる。なお、金属層１２及び金属層１４の材質は、Ａｌだけに限られず、他に、Ａｇ，Ｐｔ，Ｃｕ，Ａｕ，Ｃｒ，Ｍｏ，Ｗ，Ｔｉ，Ｐｄ，Ｎｉ等も用いることができる。   The band targeted by the polarizer 10 of the present invention is an infrared band having a wavelength of about 1 μm to 20 μm. In this band, the material of the base material 11 is, for example, Si, which is a low-loss material, and the material of the metal layer 12 and the metal layer 14 is Al. For example, when the wavelength is 10 μm, the imaginary part κ of the optical constant of Al (the real part n and the imaginary part κ of the refractive index) is 89.8. In this case, the skin depth δ, which is the depth at which the amplitude of the electric field of the electromagnetic wave incident on the metal surface is 1 / e, is 17.7 nm. Note that the material of the metal layer 12 and the metal layer 14 is not limited to Al, but Ag, Pt, Cu, Au, Cr, Mo, W, Ti, Pd, Ni, or the like can also be used.

周期構造は、例えば図２及び図３に示す三角波形状と正弦波形状の場合では、その尾根部４（あるいは谷部５）がサブ波長周期で繰り返す構造となっている。サブ波長周期とは、構造周期が入射電磁波の波長と同程度か、それよりも小さいという意味である。透過あるいは反射する波に高次の回折波が発生せず、０次だけの透過光あるいは反射光になる条件を指す。この周期構造は、媒体の屈折率境界で生じるフレネル反射を低減するように作用し、いわゆる反射低減効果を有する。こうした周期構造は、サブ波長格子（Ｓｕｂ−Ｗａｖｅｌｅｎｇｔｈ Ｇｒａｔｉｎｇ：ＳＷＧ）といい、反射防止表面や偏光分離素子として、ディスプレイ、光検出器、発光素子への応用が期待できる。   For example, in the case of the triangular wave shape and the sine wave shape shown in FIGS. 2 and 3, the periodic structure has a structure in which the ridge portion 4 (or valley portion 5) repeats with a sub-wavelength period. The sub-wavelength period means that the structure period is the same as or smaller than the wavelength of the incident electromagnetic wave. This refers to a condition in which a high-order diffracted wave is not generated in a transmitted or reflected wave, and only 0th-order transmitted light or reflected light is obtained. This periodic structure acts to reduce Fresnel reflection occurring at the refractive index boundary of the medium, and has a so-called reflection reduction effect. Such a periodic structure is called a sub-wavelength grating (SWG), and can be expected to be applied to a display, a photodetector, and a light emitting element as an antireflection surface or a polarization separation element.

周期構造の格子形状は、適用する波長（テラヘルツ帯域、近赤外帯域等）において、回折散乱を伴わない構造周期Λ（ラムダ）（＜λ／ｎ）であることが好ましい。ここで、λは波長であり、ｎは基材１１の屈折率である。上記の式「Λ＜λ／ｎ」を満たす範囲内で、金属薄膜のサブ波長格子の周期Λを設定すれば、大きな偏光特性をもたせることができる。   The grating shape of the periodic structure is preferably a structural period Λ (lambda) (<λ / n) that does not involve diffraction scattering at the wavelength to be applied (terahertz band, near infrared band, etc.). Here, λ is the wavelength and n is the refractive index of the substrate 11. If the period Λ of the sub-wavelength grating of the metal thin film is set within a range satisfying the above formula “Λ <λ / n”, a large polarization characteristic can be provided.

赤外帯域では、基材１１をＳｉとした場合、ｎは３．４なので、λ／ｎよりも小さいΛの好ましい範囲は１０〜１００μｍ（遠赤外）、１．５〜１０μｍ（中赤外）、０．２〜１．５μｍ（近赤外）の範囲とすることが好ましい。   In the infrared band, when the substrate 11 is made of Si, n is 3.4. Therefore, the preferable range of Λ smaller than λ / n is 10 to 100 μm (far infrared), 1.5 to 10 μm (middle infrared) ), Preferably in the range of 0.2 to 1.5 μm (near infrared).

周期構造は、図１、図２及び図３に示すような三角波形状や正弦波形状等を例示できる。図示しないが、ノコギリ波形状であってもよい。これらの形状は、尾根部４（凸部）と谷部５（凹部）を有し、上記の構造周期Λは、尾根部４，４間、又は谷部５，５間で評価することができる。   Examples of the periodic structure include a triangular wave shape and a sine wave shape as shown in FIGS. Although not shown, a sawtooth shape may be used. These shapes have a ridge part 4 (convex part) and a valley part 5 (concave part), and the above structural period Λ can be evaluated between the ridge parts 4 and 4 or between the valley parts 5 and 5. .

周期構造を構成する単位構造の尾根部４から谷部５までを高さＬとすると、アスペクト比（Ｌ／Λ［図２、図３では、ｈ／Λ］）は０．５以上が好ましく、１．０以上がより好ましい。アスペクト比が高いほど高い偏光特性を得ることができる。なお、アスペクト比の上限は特にないが、製造容易の観点から現実的なアスペクト比は３．０程度である。こうしたアスペクト比の範囲内になるように、三角波形状や正弦波形状等からなる単位構造の構造周期Λ（ピッチ）と高さＬを規定する。中赤外帯域で好ましい構造周期Λが上記の（１．５〜１０μｍ）の範囲である場合には、その上下限に対応した高さＬは（０．７５〜５μｍ）以上、（４．５〜３０μｍ）以下の範囲となる。   When the height from the ridge part 4 to the valley part 5 of the unit structure constituting the periodic structure is a height L, the aspect ratio (L / Λ [h / Λ in FIGS. 2 and 3]) is preferably 0.5 or more, 1.0 or more is more preferable. Higher polarization characteristics can be obtained as the aspect ratio is higher. The upper limit of the aspect ratio is not particularly limited, but the realistic aspect ratio is about 3.0 from the viewpoint of easy manufacture. The structural period Λ (pitch) and height L of the unit structure having a triangular wave shape, a sine wave shape, or the like are defined so as to be within the range of such an aspect ratio. When the preferable structural period Λ in the mid-infrared band is in the range of (1.5 to 10 μm), the height L corresponding to the upper and lower limits is (0.75 to 5 μm) or more, (4.5 ˜30 μm) or less.

こうした周期構造を含む基材１１の全体の厚さＴは特に限定されないが、例えば５００〜２０００μｍ程度であればよい。周期構造の形成は、基材１１の表面に、干渉露光法や電子ビーム露光法によりレジストの周期構造を作製してそれをそのまま利用するか、あるいはさらにそのレジストの厚み形状をリアクティブイオンエッチングなどにより基材に転写するなどして実現することができる。また、レーザーアブレーションにより表面を走査することによっても周期構造の形成が可能である他、周期構造を形成した金属或いはセラミックスを型として、樹脂等に周期構造を転写して形成することもできる。   Although the total thickness T of the base material 11 including such a periodic structure is not particularly limited, it may be, for example, about 500 to 2000 μm. The periodic structure is formed by forming a resist periodic structure on the surface of the substrate 11 by interference exposure or electron beam exposure and using it as it is, or by changing the thickness of the resist to reactive ion etching or the like. It can be realized by transferring to a substrate. Further, the periodic structure can be formed by scanning the surface by laser ablation, and the periodic structure can be formed by transferring the periodic structure to a resin or the like using a metal or ceramic having the periodic structure as a mold.

（金属層）
金属層１２及び金属層１４の材質は、下記のように、適用する波長帯域に応じた適切な材質のものが選ばれる。なお、図１、図２及び図３では、金属層を二層として示しているが、複数の金属層を有していればよく、三層、四層あるいはそれ以上の数の金属層を設けても良い。 (Metal layer)
The material of the metal layer 12 and the metal layer 14 is selected as appropriate depending on the wavelength band to be applied as described below. 1, 2, and 3, the metal layer is shown as two layers. However, it is only necessary to have a plurality of metal layers, and three, four, or more metal layers are provided. May be.

赤外帯域では、金属層１２及び金属層１４の材質としては、Ｐｔ，アルミニウム，Ａｕ，Ｎｉ等を用いることができるが、中でも、高い虚部κを持つアルミニウムが好ましく用いられる。そして、この帯域で適用する金属層１２及び金属層１４の合計の厚さは、例えば赤外帯域での表皮深さδ程度が好ましく、具体的には例えば波長が１０μｍ（表皮深さδが１７．７ｎｍ）の場合では合計で１８ｎｍの厚さであることが好ましい。   In the infrared band, Pt, aluminum, Au, Ni, or the like can be used as the material of the metal layer 12 and the metal layer 14, and among them, aluminum having a high imaginary part κ is preferably used. The total thickness of the metal layer 12 and the metal layer 14 applied in this band is preferably, for example, about the skin depth δ in the infrared band. Specifically, for example, the wavelength is 10 μm (the skin depth δ is 17). .7 nm), the total thickness is preferably 18 nm.

金属層１２及び金属層１４の合計の厚さが適用波長における表皮深さδ以上である場合には、ＴＭ偏光とＴＥ偏光に対して、高反射ミラーとなってしまう。ＴＭ偏光を透過して偏光子として動作させるためには、金属層１２及び金属層１４の合計の厚さを、上記のように、表皮深さδ程度に薄くすることが望ましい。   When the total thickness of the metal layer 12 and the metal layer 14 is equal to or greater than the skin depth δ at the applied wavelength, a high-reflection mirror is formed for TM polarized light and TE polarized light. In order to transmit TM polarized light and operate as a polarizer, it is desirable that the total thickness of the metal layer 12 and the metal layer 14 be as thin as the skin depth δ as described above.

こうした金属層１２は、スパッタリング法、蒸着法等で周期構造上の全面に形成することができる。また、金属層１４は、金属層１２の形成後、中間層１３を形成した後、同様の方法で形成することができる。   Such a metal layer 12 can be formed on the entire surface of the periodic structure by sputtering, vapor deposition, or the like. The metal layer 14 can be formed by the same method after the formation of the metal layer 12 and the intermediate layer 13.

（中間層）
中間層１３は、金属層１２を形成した後、高周波スパッタリング法や電子ビーム蒸着法によりアモルファスシリコン膜を成膜することによって形成することができる。 (Middle layer)
The intermediate layer 13 can be formed by forming an amorphous silicon film by high frequency sputtering or electron beam evaporation after forming the metal layer 12.

以上説明したように、本発明の偏光子１０は、図１、図２及び図３等に示すように、サブ波長オーダーの周期構造の表面に金属層１２及び金属層１４が形成されているので、ＴＭ偏光を透過し、ＴＥ偏光を反射又は吸収するという特性、すなわちＴＭ偏光を低損失で透過（ＴＭ透過損失が小さい）しＴＥ偏光を高損失で透過（ＴＥ透過損失が大きい）するという高い偏光特性を持っている。こうした特徴を持つ偏光子１０は、分光分析（試薬、セキュリティー）、光通信、光通信アイソレーター等、偏波選択が必要な用途に利用可能である。   As described above, the polarizer 10 of the present invention has the metal layer 12 and the metal layer 14 formed on the surface of the periodic structure in the sub-wavelength order, as shown in FIGS. , TM polarization is transmitted and TE polarization is reflected or absorbed, that is, TM polarization is transmitted with low loss (TM transmission loss is small) and TE polarization is transmitted with high loss (TE transmission loss is large). Has polarization characteristics. The polarizer 10 having such characteristics can be used for applications that require polarization selection, such as spectroscopic analysis (reagents, security), optical communication, and optical communication isolators.

（複数の金属層１２、金属層１４）
さらに、本発明の偏光子１０は、図１、図２及び図３等に示すように、複数の金属層１２及び金属層１４を有しているため、単一の金属層の場合に比較して、ＴＭ透過損失を小さく、ＴＥ透過損失を大きくすることができる。 (Multiple metal layers 12, metal layers 14)
Furthermore, the polarizer 10 of the present invention has a plurality of metal layers 12 and metal layers 14 as shown in FIGS. 1, 2, 3 and the like, so that it is compared with a single metal layer. Thus, the TM transmission loss can be reduced and the TE transmission loss can be increased.

以下、ＴＥ偏光（ＴＥ波）とＴＭ偏光（ＴＭ派）各々について特性を検討する。
１．ＴＥ波
金属層１４に入射し、金属層１４、中間層１３、金属層１２を透過するＴＥ波については、単純な平板金属膜の透過の場合と同等に考えることができる。透過率は金属中での吸収と金属表面での反射で決まる。 Hereinafter, characteristics will be examined for each of TE polarized light (TE wave) and TM polarized light (TM group).
1. The TE wave incident on the metal layer 14 and transmitted through the metal layer 14, the intermediate layer 13, and the metal layer 12 can be considered equivalent to the case of transmission through a simple flat metal film. The transmittance is determined by absorption in the metal and reflection at the metal surface.

（１）吸収
金属層における吸収は、（吸収係数×金属層の厚さ）で決まる。このため、単層格子（金属層が１層）でも多層格子（金属層が複数層）でも合計の金属厚さ（金属層１２と金属層１４の合計の厚さ）が同じならば吸収による透過損失はほぼ等しい。ただし、多層構造では多重反射が存在するので、厳密には全ての多重反射光成分を加えて減衰量を求める必要がある。 (1) Absorption Absorption in the metal layer is determined by (absorption coefficient × metal layer thickness). Therefore, if the total metal thickness (the total thickness of the metal layer 12 and the metal layer 14) is the same in both the single-layer lattice (single metal layer) and the multilayer lattice (multiple metal layers), the transmission by absorption The loss is almost equal. However, since multiple reflections exist in a multilayer structure, strictly speaking, it is necessary to obtain an attenuation amount by adding all the multiple reflected light components.

（２）反射
金属層における反射は、境界数が多いほど反射の効果は大きくなる。このため、多層にしたほうが単層の時より損失を大きくできる。ただし、多層構造では層間の多重反射による干渉効果が存在するため、Ｄの値に依存する。 (2) Reflection As for the reflection in the metal layer, the effect of reflection increases as the number of boundaries increases. For this reason, the loss can be increased in the multilayer as compared with the single layer. However, in the multilayer structure, there is an interference effect due to multiple reflections between layers, and therefore depends on the value of D.

図５は、入射光の波長λが１μｍ、周期構造の周期Λが２５０ｎｍ、アスペクト比ｈ／Λが１、基材１１の材質がＴｓｕｒｕｐｉｃａ（登録商標）であり、金属層１２と金属層１４の厚さの合計が１８μｍ、中間層１３の材質がＳｉＯ２である場合の、中間層１３の厚さＤの変化に対するＴＥ波とＴＭ波の透過損失特性を、厳密結合波解析（ＲＣＷＡ：Ｒｉｇｏｒｏｕｓ Ｃｏｕｐｌｅｄ Ｗａｖｅ Ａｎａｌｙｓｉｓ））法を用いた数値解析により求めたグラフである。この図５中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 In FIG. 5, the wavelength λ of incident light is 1 μm, the period Λ of the periodic structure is 250 nm, the aspect ratio h / Λ is 1, the material of the substrate 11 is Tsurupica (registered trademark), and the metal layer 12 and the metal layer 14 When the total thickness is 18 μm and the material of the intermediate layer 13 is SiO 2 , the transmission loss characteristics of the TE wave and the TM wave with respect to the change in the thickness D of the intermediate layer 13 are analyzed by a rigorous coupled wave analysis (RCWA: Rigorous Coupled It is the graph calculated | required by the numerical analysis using Wave Analysis)) method. In FIG. 5, the solid line indicates the characteristics when the cross section of the periodic structure has a sinusoidal shape, and the broken line indicates the characteristics when the cross section of the periodic structure has a triangular wave shape.

この図５に示すように、ＴＥ波が中間層１３の厚さＤに対して周期的な変動が生じているのはこの多重反射による干渉である。例えば同図において隣り合うピークが生じるＤの差は、０．３５μｍ（９００−５５０＝３５０ｎｍ）である。即ち、０．３５μｍ（金属膜間隔）×２（往復分）×１．４５（屈折率）が、第１の格子と第２の格子の間を往復する光路長になる。この値は１．０１５となり、波長とほぼ同じになることから多重反射に起因した干渉現象であることがわかる。   As shown in FIG. 5, it is the interference caused by this multiple reflection that the TE wave periodically varies with respect to the thickness D of the intermediate layer 13. For example, the difference in D in which adjacent peaks occur in the figure is 0.35 μm (900−550 = 350 nm). That is, 0.35 μm (metal film interval) × 2 (reciprocation) × 1.45 (refractive index) is the optical path length reciprocating between the first grating and the second grating. This value is 1.015, which is almost the same as the wavelength, so that it is understood that this is an interference phenomenon caused by multiple reflection.

２．ＴＭ波
金属層１４に入射し、金属層１４、中間層１３、金属層１２を透過するＴＭ波の透過は、入射光が金属格子の表面（入射側）および裏面（出射側）に励起される表面プラズモンを介して行われる。このため、透過率は金属境界面の数にはほとんど依存しない。ここで、図６〜図８にモデルを示す。なお、金属膜の厚さは表皮深さδより小さいことが必要であり、δは金属の複素屈折率の虚部をκとするとδ＝λ／（２πκ）である。 2. TM wave Transmission of TM waves incident on the metal layer 14 and transmitted through the metal layer 14, the intermediate layer 13, and the metal layer 12 causes the incident light to be excited on the front surface (incident side) and back surface (exit side) of the metal grating. Done through surface plasmons. For this reason, the transmittance hardly depends on the number of metal interfaces. Here, a model is shown in FIGS. Note that the thickness of the metal film needs to be smaller than the skin depth δ, and δ is δ = λ / (2πκ), where imaginary part of the complex refractive index of the metal is κ.

（ａ）図６は、単層の格子（金属層が一層の格子）の場合の表面（入射側）および裏面（出射側）に励起される表面プラズモン（Ａ１、Ａ２）を概念的に示す図である。このような場合では、多層の格子の場合に比べて１層当りの金属層の膜厚が厚いため、金属層の裏面（出射側）に励起される表面プラズモンＡ２の振幅が小さく、透過損失が大きくなる。 (A) FIG. 6 is a diagram conceptually showing surface plasmons (A1, A2) excited on the front surface (incident side) and the back surface (exit side) in the case of a single-layer lattice (a single-layer lattice). It is. In such a case, since the thickness of the metal layer per layer is thicker than in the case of a multi-layer grating, the amplitude of the surface plasmon A2 excited on the back surface (exit side) of the metal layer is small, and the transmission loss is small. growing.

（ｂ）図７は、二重格子（金属層が二層の格子）で中間層１３の厚さＤが小さい場合の表面（入射側）および裏面（出射側）に励起される表面プラズモン（Ａ１、Ａ４）と、各金属層１２、金属層１４の中間層１３側に励起される表面プラズモン（Ａ２、Ａ３）を概念的に示す図である。このような場合では、２つの金属層の間における表面プラズモン（Ａ２とＡ３）が十分大きな振幅をもたない。この結果、出射側の表面プラズモンＡ４の振幅も入射側の表面プラズモンＡ１と比べて大きくないために透過損失の低減効果は小さい。 (B) FIG. 7 shows a surface plasmon (A1) excited on the front surface (incident side) and the rear surface (exit side) when the thickness D of the intermediate layer 13 is small in a double lattice (a lattice having two metal layers). , A4), and the surface plasmons (A2, A3) excited on the intermediate layer 13 side of each metal layer 12 and metal layer 14 are conceptually shown. In such a case, the surface plasmons (A2 and A3) between the two metal layers do not have a sufficiently large amplitude. As a result, since the amplitude of the surface plasmon A4 on the emission side is not large compared to the surface plasmon A1 on the incident side, the effect of reducing the transmission loss is small.

（ｃ）図８は、一層当りの金属層の膜厚が十分小さい二重格子で、かつ中間層１３の厚さＤが十分大きい場合の表面（入射側）および裏面（出射側）に励起される表面プラズモン（Ａ１、Ａ４）と、各金属層１２、金属層１４の中間層１３側に励起される表面プラズモン（Ａ２、Ａ３）を概念的に示す図である。このような場合では、入射光は第１の金属膜（金属層１４）の表面プラズモン（Ａ１とＡ２）を介して中間層１３の光に結合される。さらに第２の金属膜（金属層１２）の表面プラズモン（Ａ３とＡ４）を介して出射光に高効率で結合する。 (C) FIG. 8 is excited by the front surface (incident side) and the back surface (exit side) when the thickness of the metal layer per layer is sufficiently small and the thickness D of the intermediate layer 13 is sufficiently large. FIG. 2 is a diagram conceptually showing surface plasmons (A1, A4) and surface plasmons (A2, A3) excited on the intermediate layer 13 side of each metal layer 12 and metal layer 14; In such a case, the incident light is coupled to the light of the intermediate layer 13 through the surface plasmons (A1 and A2) of the first metal film (metal layer 14). Furthermore, it couple | bonds with an emitted light with high efficiency through the surface plasmon (A3 and A4) of a 2nd metal film (metal layer 12).

以上の図６〜図８のモデルから以下のことを説明できる。
図５（波長λ＝１μｍの場合）に示すように、中間層１３の厚さＤが大きくなるにつれてＴＭ波の損失が単調に小さくなり、ある程度以上（１００ｎｍ以上）になれば、ほぼ一定になる。 The following can be explained from the models shown in FIGS.
As shown in FIG. 5 (in the case of wavelength λ = 1 μm), the loss of the TM wave monotonously decreases as the thickness D of the intermediate layer 13 increases, and becomes almost constant when the loss becomes a certain level (100 nm or more). .

図９は、入射光の波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１である場合の、金属層が一層の場合と二層の場合の、ＲＣＷＡ法を用いた数値解析により求めた、金属層の厚さに対するＴＥ波とＴＭ波の透過損失特性を示している。この図９中において、実線は中間層１３の厚さＤが１．５μｍの二層の場合の（金属層の厚さの合計に対する）特性を示しており、破線はＤ＝０すなわち一層の場合の特性を示している。この図９に示すように、金属層の厚さが厚くなるとある厚さ以上で急激にＴＭ波の損失が大きくなる。また、金属層を２分割して二層にしたほうがＴＭ波の損失を大幅に低減することができる。   FIG. 9 shows the RCWA method when the wavelength λ of the incident light is 10 μm, the period Λ of the periodic structure is 2.5 μm, and the aspect ratio h / Λ is 1, when the metal layer is one layer and two layers. The transmission loss characteristics of the TE wave and the TM wave with respect to the thickness of the metal layer obtained by the numerical analysis used are shown. In FIG. 9, the solid line shows the characteristics when the intermediate layer 13 has a thickness D of 1.5 μm (relative to the total thickness of the metal layers), and the broken line shows the case of D = 0, that is, one layer. The characteristics are shown. As shown in FIG. 9, when the thickness of the metal layer is increased, the loss of the TM wave rapidly increases beyond a certain thickness. Further, the loss of the TM wave can be greatly reduced by dividing the metal layer into two layers.

図１０は、入射光の波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、基材１１及び中間層１３の材質がＳｉであり、二重格子（金属層が二層）を構成する金属層の合計の厚さｔが１８μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層１３の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示している。この図１０中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。横軸のＤ＝０の点は、単層の金属の場合の特性に該当する。   In FIG. 10, the wavelength λ of incident light is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, the material of the substrate 11 and the intermediate layer 13 is Si, and a double grating (metal layer) The transmission loss characteristics of TE wave and TM wave with respect to the thickness D of the intermediate layer 13 obtained by numerical analysis using the RCWA method when the total thickness t of the metal layers constituting the two layers) is 18 μm. Is shown. In FIG. 10, the solid line shows the characteristic when the cross section of the periodic structure has a sine wave shape, and the broken line shows the characteristic when the cross section of the periodic structure has a triangular wave shape. The point of D = 0 on the horizontal axis corresponds to the characteristic in the case of a single layer metal.

図１１は、入射光の波長λが１０μｍ、周期構造の周期Λが２．５μｍ、アスペクト比ｈ／Λが１、基材１１及び中間層１３の材質がＳｉであり、四重格子（金属層が四層）を構成する金属層の合計の厚さｔが１８μｍである場合の、ＲＣＷＡ法を用いた数値解析により求めた、中間層１３の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示している。この図１１中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。横軸のＤ＝０の点は、単層の金属の場合の特性に該当する。   In FIG. 11, the wavelength λ of incident light is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ is 1, the material of the base material 11 and the intermediate layer 13 is Si, and a quadruple lattice (metal layer) Transmission wave characteristics of TE wave and TM wave with respect to the thickness D of the intermediate layer 13 obtained by numerical analysis using the RCWA method when the total thickness t of the metal layers constituting the four layers is 18 μm. Is shown. In FIG. 11, the solid line indicates the characteristics when the cross section of the periodic structure has a sinusoidal shape, and the broken line indicates the characteristics when the cross section of the periodic structure has a triangular wave shape. The point of D = 0 on the horizontal axis corresponds to the characteristic in the case of a single layer metal.

図１０と図１１を比較すると明らかなように金属層の分割数を大きくする（一層あたりの金属層厚は単層の場合に対して分割数で除した値）方が特性は向上する。周期構造の断面が三角波形状の場合については、二重格子、四重格子の場合とも、中間層１３の厚さに対してＴＭ波の損失が急激に減少し（四重格子のほうが顕著）、その後Ｄによらず小さい値を保持する。一方ＴＥ波の損失はＤが２〜２．５μｍ程度までＤに比例して大きくなり、２重格子で６０ｄＢ程度、四重格子で８５ｄＢ以上に達する。すなわち、分割数を多くしたほうが特性は向上する。周期構造の断面が正弦波形状の場合についても、中間層１３の厚さＤに対して二重格子、四重格子の場合とも損失が減少し、Ｄが一定の値（３μｍ）以上で四重格子のほうがより損失が小さくなる。ＴＥ波の損失はＤが２〜２．５μｍ程度までＤに比例して大きくなり、２重格子で６０ｄＢ程度、四重格子で７０ｄＢ以上に達する。すなわち、分割数を多くしたほうが特性は向上している。   As is clear from comparison between FIG. 10 and FIG. 11, the characteristics are improved by increasing the number of divisions of the metal layer (the thickness of the metal layer per layer is a value obtained by dividing the number of divisions with respect to a single layer). In the case where the cross section of the periodic structure has a triangular wave shape, the loss of the TM wave sharply decreases with respect to the thickness of the intermediate layer 13 in both the double grating and the quadruple grating (the quadruple grating is more remarkable) Thereafter, a small value is maintained regardless of D. On the other hand, the TE wave loss increases in proportion to D until D reaches about 2 to 2.5 μm, and reaches about 60 dB for the double grating and 85 dB or more for the quadruple grating. That is, the characteristics are improved by increasing the number of divisions. Even in the case where the cross section of the periodic structure has a sine wave shape, the loss is reduced with respect to the thickness D of the intermediate layer 13 in the case of a double lattice or a quadruple lattice, and when D is equal to or greater than a certain value (3 μm) Lattice is less lossy. The TE wave loss increases in proportion to D until D reaches about 2 to 2.5 μm, and reaches about 60 dB for the double grating and 70 dB or more for the quadruple grating. That is, the characteristics are improved by increasing the number of divisions.

以上説明したように、この偏光子１０では、金属層の数を複数とすることにより、ＴＭ偏光を透過し、ＴＥ偏光を反射又は吸収するという特性、すなわちＴＭ偏光を低損失で透過（ＴＭ透過損失が小さい）させ、ＴＥ偏光を高損失で透過（ＴＥ透過損失が大きい）させる偏光特性を向上させることができる。   As described above, the polarizer 10 has a characteristic that it transmits TM polarized light and reflects or absorbs TE polarized light, that is, transmits TM polarized light with low loss (TM transmission) by using a plurality of metal layers. The polarization characteristic of transmitting TE polarized light with high loss (high TE transmission loss) can be improved.

［光モジュール］
本発明に係る光モジュールは、上記した本発明の偏光子１０を用いて構成されるデバイス又は機器である。赤外帯域で用いる光モジュールの例としては、通信用光アイソレーターを挙げることができる。通信用光アイソレーターは、互いに透過する偏光の向きが４５度傾いた２枚の偏光子の間に、偏光の回転角が４５度のファラデー回転子を挿入することにより構成したものである。こうした光アイソレーターによれば、ある方向の光はすべて透過し、逆方向の光は透過しないようにできる。光通信では半導体レーザの発信を安定化するのに必要であり、偏光子は必要不可欠なモジュールの一つの構成部品である。その偏光子に本発明の偏光子１０を用いれば、安価かつ広開口の光アイソレーターが製造できる。 [Optical module]
The optical module according to the present invention is a device or apparatus configured using the above-described polarizer 10 of the present invention. An example of an optical module used in the infrared band is an optical isolator for communication. The communication optical isolator is configured by inserting a Faraday rotator having a polarization rotation angle of 45 degrees between two polarizers whose polarization directions transmitted through each other are inclined by 45 degrees. According to such an optical isolator, it is possible to transmit all light in a certain direction and not transmit light in the opposite direction. In optical communication, it is necessary to stabilize the transmission of a semiconductor laser, and a polarizer is one component of an indispensable module. If the polarizer 10 of the present invention is used for the polarizer, an inexpensive and wide aperture optical isolator can be manufactured.

以下、解析例により本発明をさらに具体的に説明する。   Hereinafter, the present invention will be described more specifically with analysis examples.

［解析例１］
上述の図２及び図３に示す構造をモデリングし、二重格子構造（金属層が二層）について、厳密結合波解析（ＲＣＷＡ）法を用いた数値解析によって、（Ａ）中間層厚依存性、（Ｂ）アスペクト比依存性、（Ｃ）金属層厚依存性を解析した。 [Analysis Example 1]
Modeling the structure shown in FIG. 2 and FIG. 3 above, and (A) intermediate layer thickness dependence by numerical analysis using a rigorous coupled wave analysis (RCWA) method for a double lattice structure (two metal layers) (B) Aspect ratio dependency and (C) Metal layer thickness dependency were analyzed.

これらの数値解析では、入射光の波長λを１０μｍ、周期構造の周期Λを２．５μｍ、基材１１及び中間層１３の材質をＳｉ（ｎ＝３．４、κ＝０）、金属層をＡｌ（屈折率ｎ＝２５．３、消衰係数κ＝８９．８）と仮定している。   In these numerical analyses, the wavelength λ of incident light is 10 μm, the period Λ of the periodic structure is 2.5 μm, the material of the base material 11 and the intermediate layer 13 is Si (n = 3.4, κ = 0), and the metal layer is It is assumed that Al (refractive index n = 25.3, extinction coefficient κ = 89.8).

（Ａ）中間層厚依存性
上述の図１０は、中間層１３の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示している。この数値解析では、アスペクト比ｈ／Λを１、二重格子（金属層が二層）を構成する金属層の合計の厚さｔを１８μｍ（金属層１２及び金属層１４の厚さは各々９μｍ）としている。上述の図１０中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 (A) Dependence on Intermediate Layer Thickness FIG. 10 described above shows transmission loss characteristics of TE waves and TM waves with respect to the thickness D of the intermediate layer 13. In this numerical analysis, the aspect ratio h / Λ is 1, the total thickness t of the metal layers constituting the double lattice (two metal layers) is 18 μm (the thicknesses of the metal layer 12 and the metal layer 14 are each 9 μm). ). In FIG. 10 described above, the solid line indicates the characteristic when the cross section of the periodic structure has a sinusoidal shape, and the broken line indicates the characteristic when the cross section of the periodic structure has a triangular wave shape.

周期構造の断面が正弦波形状及び三角波形状のいずれも、中間層の厚さＤが厚くなるに伴い、ＴＭ波の透過損失は減少する。中間層の厚さＤが０〜１．５μｍのとき、ＴＥ波の透過損失は、Ｄが厚くなるに伴い増加し、Ｄ＞１．５μｍでは減少していく。Ｄ＝１．５μｍ付近でＴＥ波の透過損失が最大となり、Ｄ＝０（単層膜）のときに比べ、消光比が２０ｄＢ以上向上する。以上より、上述のような構成の二重格子構造の場合は、中間層１３（Ｓｉ）の厚さをＤを１．５μｍとすることが望ましい。   In both the sinusoidal and triangular wave sections of the periodic structure, the transmission loss of the TM wave decreases as the thickness D of the intermediate layer increases. When the thickness D of the intermediate layer is 0 to 1.5 μm, the TE wave transmission loss increases as D increases, and decreases when D> 1.5 μm. The TE wave transmission loss is maximized in the vicinity of D = 1.5 μm, and the extinction ratio is improved by 20 dB or more compared to the case of D = 0 (single layer film). As described above, in the case of the double lattice structure configured as described above, it is desirable that the thickness of the intermediate layer 13 (Si) is D = 1.5 μm.

なお、上述の図５に示す波長λが１μｍである場合には、中間層の厚さＤが０．１５μｍのときにＴＥ波の透過損失が最大となる。また、後述の図２４に示す波長λが２０μｍである場合には、中間層の厚さＤが３μのときにＴＥ波の透過損失が最大となる。従って、上述のような構成の二重格子構造の場合で、波長λが１μｍ〜２０μｍの範囲では、Ｄを０．１５λとすることが望ましい。   When the wavelength λ shown in FIG. 5 is 1 μm, the TE wave transmission loss becomes maximum when the thickness D of the intermediate layer is 0.15 μm. When the wavelength λ shown in FIG. 24 described later is 20 μm, the TE wave transmission loss becomes maximum when the thickness D of the intermediate layer is 3 μm. Therefore, in the case of the double grating structure having the above-described configuration, it is desirable that D is 0.15λ in the range where the wavelength λ is 1 μm to 20 μm.

（Ｂ）アスペクト比依存性
図１２は、アスペクト比ｈ／Λに対するＴＥ波とＴＭ波の透過損失特性を示している。この数値解析では、中間層１３の厚さＤを１．５μｍ（二重格子構造であって（Ａ）で仮定した条件において消光比が最大となるＤの値）、二重格子（金属層が二層）を構成する金属層の合計の厚さｔを１８μｍ（金属層１２及び金属層１４の厚さは各々９μｍ）としている。この図１２中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 (B) Aspect Ratio Dependency FIG. 12 shows transmission loss characteristics of TE waves and TM waves with respect to the aspect ratio h / Λ. In this numerical analysis, the thickness D of the intermediate layer 13 is 1.5 μm (the value of D that has a double lattice structure and the extinction ratio is maximum under the conditions assumed in (A)), and the double lattice (the metal layer is The total thickness t of the metal layers constituting the two layers is 18 μm (the thickness of each of the metal layers 12 and 14 is 9 μm). In FIG. 12, the solid line indicates the characteristic when the cross section of the periodic structure has a sine wave shape, and the broken line indicates the characteristic when the cross section of the periodic structure has a triangular wave shape.

この図１２より、アスペクト比ｈ／Λの増加に伴い、ＴＥ波とＴＭ波の透過損失差が大きくなり、高い消光比を得られることがわかる。断面形状ごとの特性を比較すると、正弦波形状の断面を持つ構造では三角波形状に比べ、アスペクト比が小さく（ｈ／Λ＜０．５）なった場合、ＴＭ波の透過損失を抑えることができる。ＴＭ波の透過損失について、ＴＥ波の透過損失を上回る場所が存在しているのは、アスペクト比の変化に伴い電界の振動方向に平行な金属層の厚さも変化することから、特定のアスペクト比（電界の振動方向と平行な厚さと同義）において、金属層で共鳴吸収が起きているためと考えられる。以上より、アスペクト比ｈ／Λの増加によって良好な偏光特性が得られ、挿入損失は、正弦波形状の方が三角波形状に比べ構造のアスペクト比による依存が少ない。また、構造のアスペクト比アスペクト比は、正弦波形状では０．５以上、三角波形状では０．６以上であることが望ましい。   From FIG. 12, it can be seen that as the aspect ratio h / Λ increases, the transmission loss difference between the TE wave and the TM wave increases, and a high extinction ratio can be obtained. Comparing the characteristics of each cross-sectional shape, the transmission loss of TM waves can be suppressed when the aspect ratio is smaller (h / Λ <0.5) in the structure having a sinusoidal cross-section than in the triangular wave shape. . Regarding the TM wave transmission loss, there is a place that exceeds the TE wave transmission loss because the thickness of the metal layer parallel to the vibration direction of the electric field also changes with the change of the aspect ratio. It is considered that resonance absorption occurs in the metal layer in (synonymous with the thickness parallel to the vibration direction of the electric field). As described above, good polarization characteristics can be obtained by increasing the aspect ratio h / Λ, and the insertion loss is less dependent on the aspect ratio of the structure in the sine wave shape than in the triangular wave shape. The aspect ratio of the structure is preferably 0.5 or more for a sine wave shape and 0.6 or more for a triangular wave shape.

（Ｃ）金属層厚依存性
上述の図９は、周期構造の断面が正弦波形状となっている偏光子の、金属層の合計の厚さｔに対する透過損失特性の計算結果を示している。上述の図９中において、実線は中間層１３の厚さＤが１．５μｍである二重格子構造（金属層が二層）の場合の特性を示しており、破線は中間層１３の厚さＤが０すなわち金属層が一層の場合の特性を示している。なお、二重格子構造の場合は各々の金属層の厚さはｔの半分（ｔ／２）である。 (C) Metal Layer Thickness Dependence FIG. 9 described above shows the calculation result of the transmission loss characteristic with respect to the total thickness t of the metal layer of the polarizer having a periodic structure with a sine wave cross section. In FIG. 9 described above, the solid line indicates the characteristics in the case of a double lattice structure (two metal layers) in which the thickness D of the intermediate layer 13 is 1.5 μm, and the broken line indicates the thickness of the intermediate layer 13. The characteristics when D is 0, that is, when the metal layer is one layer are shown. In the case of a double lattice structure, the thickness of each metal layer is half of t (t / 2).

また、図１３は、周期構造の断面が三角波形状となっている偏光子の、金属層の合計の厚さｔに対する透過損失特性の計算結果を示している。図１３中において、実線は中間層１３の厚さＤが１．５μｍである二重格子構造（金属層が二層）の場合の特性を示しており、破線は中間層１３の厚さＤが０すなわち金属層が一層の場合の特性を示している。なお、二重格子構造の場合は各々の金属層の厚さはｔの半分（ｔ／２）である。   FIG. 13 shows the calculation result of the transmission loss characteristic with respect to the total thickness t of the metal layer of the polarizer having a periodic structure with a triangular wave cross section. In FIG. 13, the solid line indicates the characteristics in the case of a double lattice structure (the metal layer is two layers) in which the thickness D of the intermediate layer 13 is 1.5 μm, and the broken line indicates the thickness D of the intermediate layer 13. 0, that is, the characteristics when the metal layer is one layer. In the case of a double lattice structure, the thickness of each metal layer is half of t (t / 2).

上述の図９、図１３のいずれの場合も、金属層の合計の厚さｔの増加に伴い、ＴＥ波、ＴＭ波ともに透過損失が増加する。どちらの断面形状においてもｔ＞１５ｎｍとなると、Ｄ＝１．５μｍの場合では、Ｄ＝０の場合と比較し、ＴＭ波の透過損失（偏光子としての挿入損失）の増加を大きく低減することができる。従って、金属層の合計の厚さｔは、上述の表皮深さ程度にするのが望ましい。   9 and 13, the transmission loss increases for both the TE wave and the TM wave as the total thickness t of the metal layer increases. In both cross-sectional shapes, when t> 15 nm, the increase in TM wave transmission loss (insertion loss as a polarizer) is greatly reduced in the case of D = 1.5 μm compared to the case of D = 0. Can do. Therefore, it is desirable that the total thickness t of the metal layers be about the above-mentioned skin depth.

また、Ｄ＝１．５μｍの場合において、断面形状による特性を比較すると、ＴＥ波の透過損失に大きな差は見られない。しかしながら、三角波形状の断面では、正弦波形状と比較し、膜厚が厚くなったときの挿入損失増加を低減できる。以上より、二重格子構造の偏光子を製造する場合、三角波形状の方が金属層の作製トレランスが高いことがわかる。   Further, in the case of D = 1.5 μm, when the characteristics due to the cross-sectional shapes are compared, there is no significant difference in the TE wave transmission loss. However, in the triangular wave-shaped cross section, an increase in insertion loss when the film thickness is increased can be reduced as compared with the sine wave shape. From the above, it can be seen that when a polarizer having a double grating structure is manufactured, the triangular wave shape has a higher tolerance for forming the metal layer.

［解析例２］
三重格子構造（金属層が三層）について、厳密結合波解析（ＲＣＷＡ）法を用いた数値解析によって、（Ａ）中間層厚依存性、（Ｂ）アスペクト比依存性、（Ｃ）金属層厚依存性を解析した。これらの数値解析では、入射光の波長λを１０μｍ、周期構造の周期Λを２．５μｍ、基材１１及び中間層の材質をＳｉ（ｎ＝３．４、κ＝０）、金属層をＡｌ（屈折率ｎ＝２５．３、消衰係数κ＝８９．８）と仮定している。 [Analysis Example 2]
For a triple lattice structure (three metal layers), (A) intermediate layer thickness dependence, (B) aspect ratio dependence, (C) metal layer thickness by numerical analysis using the rigorous coupled wave analysis (RCWA) method The dependency was analyzed. In these numerical analyses, the wavelength λ of the incident light is 10 μm, the period Λ of the periodic structure is 2.5 μm, the base material 11 and the intermediate layer are made of Si (n = 3.4, κ = 0), and the metal layer is made of Al. (Refractive index n = 25.3, extinction coefficient κ = 89.8) is assumed.

（Ａ）中間層厚依存性
図１４は、中間層の合計の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示している。この数値解析では、アスペクト比ｈ／Λを１、三重格子（金属層が三層）を構成する金属層の合計の厚さｔを１８μｍ（各金属層の厚さは各々６μｍ）としている。この図１４中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 (A) Dependence on Intermediate Layer Thickness FIG. 14 shows the transmission loss characteristics of TE wave and TM wave with respect to the total thickness D of the intermediate layer. In this numerical analysis, the aspect ratio h / Λ is 1, and the total thickness t of the metal layers constituting the triple lattice (three metal layers) is 18 μm (the thickness of each metal layer is 6 μm each). In FIG. 14, the solid line indicates the characteristics when the cross section of the periodic structure has a sine wave shape, and the broken line indicates the characteristics when the cross section of the periodic structure has a triangular wave shape.

周期構造の断面が正弦波形状及び三角波形状のいずれも、中間層の合計の厚さＤが厚くなるに伴い、ＴＭ波の透過損失は減少する。中間層の合計の厚さＤ＝０〜２．５μｍのとき、ＴＥ波の透過損失は、中間層の合計の厚さＤが厚くなるに伴い増加する。Ｄ＝２．５μｍ付近でＴＥ波の透過損失は最大となり、Ｄ＝０（単層膜）のときに比べ、消光比が３０ｄＢ以上向上する。三角波形状の断面では、正弦波形状と比較し、ＴＥ波の透過損失が高い。以上より、三重格子構造の場合、周期構造の断面は三角波形状、中間層の合計の厚さＤを２．５μｍ（各中間層の厚さがＤ／２＝１．２５μｍ）とすることが望ましい。   In both the sinusoidal and triangular wave sections of the periodic structure, the TM wave transmission loss decreases as the total thickness D of the intermediate layer increases. When the total thickness D of the intermediate layer is 0 to 2.5 μm, the transmission loss of TE waves increases as the total thickness D of the intermediate layer increases. The transmission loss of the TE wave is maximized in the vicinity of D = 2.5 μm, and the extinction ratio is improved by 30 dB or more compared to when D = 0 (single layer film). The triangular wave cross section has a higher TE wave transmission loss than the sine wave shape. From the above, in the case of the triple lattice structure, the cross section of the periodic structure is preferably a triangular wave shape, and the total thickness D of the intermediate layers is preferably 2.5 μm (the thickness of each intermediate layer is D / 2 = 1.25 μm). .

また、後述の図２５は、同様な条件下で、波長λを１μｍとした場合のシミュレーション結果である。また、後述の図２６は、同様な条件下で、波長λを２０μｍとした場合のシミュレーション結果である。後述の図２５に示す結果では、Ｄ＝０．２μｍ（正弦状格子）、０．２５μｍ（三角状格子）でＴＥの損失が最大になる。また、後述の図２６に示す結果では、Ｄ＝５μｍ（正弦状格子）、６μｍ（三角状格子）でＴＥの損失が最大になる。従って、波長に比例したＤの値で最大になることがわかる。   FIG. 25 described later is a simulation result when the wavelength λ is 1 μm under the same conditions. FIG. 26 described later is a simulation result when the wavelength λ is 20 μm under the same conditions. In the result shown in FIG. 25 described later, the loss of TE is maximized when D = 0.2 μm (sine lattice) and 0.25 μm (triangular lattice). Further, in the result shown in FIG. 26 described later, the TE loss is maximized when D = 5 μm (sinusoidal lattice) and 6 μm (triangular lattice). Accordingly, it can be seen that the value D is proportional to the wavelength and becomes maximum.

（Ｂ）アスペクト比依存性
図１５は、アスペクト比ｈ／Λに対するＴＥ波とＴＭ波の透過損失特性を示している。この数値解析では、中間層の合計の厚さＤを２．５μｍ（三重格子構造であって（Ａ）で仮定した条件において消光比が最大となるＤの値）、三重格子（金属層が三層）を構成する金属層の合計の厚さｔを１８μｍ（各金属層の厚さは各々６μｍ）としている。この図１５中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 (B) Aspect Ratio Dependency FIG. 15 shows transmission loss characteristics of TE waves and TM waves with respect to the aspect ratio h / Λ. In this numerical analysis, the total thickness D of the intermediate layer is 2.5 μm (the value of D that has the triple lattice structure and the extinction ratio is maximum under the conditions assumed in (A)), and the triple lattice (the metal layer has three layers). The total thickness t of the metal layers constituting the layer) is 18 μm (the thickness of each metal layer is 6 μm each). In FIG. 15, the solid line indicates the characteristics when the cross section of the periodic structure has a sine wave shape, and the broken line indicates the characteristics when the cross section of the periodic structure has a triangular wave shape.

この図１５より、アスペクト比ｈ／Λの増加に伴い、ＴＥ波とＴＭ波の透過損失差が大きくなり、高い消光比を得られることがわかる。断面形状ごとの特性を比較すると、正弦波形状の断面を持つ構造では三角波形状に比べ、アスペクト比が小さく（ｈ／Λ＜０．５）なった場合、ＴＭ波の透過損失を抑えることができる。以上より、アスペクト比ｈ／Λの増加によって良好な偏光特性が得られ、挿入損失は、正弦波形状の方が三角波形状に比べ構造のアスペクト比による依存が少ない。また、構造のアスペクト比アスペクト比は、正弦波形状では０．３以上、三角波形状では０．５以上であることが望ましい。   From FIG. 15, it can be seen that the transmission loss difference between the TE wave and the TM wave increases as the aspect ratio h / Λ increases, and a high extinction ratio can be obtained. Comparing the characteristics of each cross-sectional shape, the transmission loss of TM waves can be suppressed when the aspect ratio is smaller (h / Λ <0.5) in the structure having a sinusoidal cross-section than in the triangular wave shape. . As described above, good polarization characteristics can be obtained by increasing the aspect ratio h / Λ, and the insertion loss is less dependent on the aspect ratio of the structure in the sine wave shape than in the triangular wave shape. The aspect ratio of the structure is preferably 0.3 or more for a sine wave shape and 0.5 or more for a triangular wave shape.

（Ｃ）金属層厚依存性
図１６は、周期構造の断面が正弦波形状の三重格子構造となっている偏光子の、金属層の合計の厚さｔに対する透過損失特性の計算結果を示している。図１６中において、実線は中間層の合計の厚さＤが２．５μｍである三重格子構造（金属層が三層）の場合の特性を示しており、破線は中間層の厚さＤが０すなわち金属層が一層の場合の特性を示している。なお、三重格子構造の場合は各々の金属層の厚さはｔの３分の１（ｔ／３）であり、各々の中間層の厚さはＤの半分（Ｄ／２）である。 (C) Dependence on Metal Layer Thickness FIG. 16 shows the calculation result of the transmission loss characteristic with respect to the total thickness t of the metal layer of the polarizer having a triple lattice structure having a sinusoidal cross section of the periodic structure. Yes. In FIG. 16, the solid line indicates the characteristics in the case of a triple lattice structure (three metal layers) in which the total thickness D of the intermediate layer is 2.5 μm, and the broken line indicates that the thickness D of the intermediate layer is 0. That is, the characteristics in the case of a single metal layer are shown. In the case of the triple lattice structure, the thickness of each metal layer is one third (t / 3) of t, and the thickness of each intermediate layer is half of D (D / 2).

また、図１７は、周期構造の断面が三角波形状の三重格子構造となっている偏光子の、金属層の合計の厚さｔに対する透過損失特性の計算結果を示している。図１７中において、実線は中間層の合計の厚さＤが２．５μｍである三重格子構造（金属層が三層）の場合の特性を示しており、破線は中間層の厚さＤが０すなわち金属層が一層の場合の特性を示している。なお、三重格子構造の場合は各々の金属層の厚さはｔの３分の１（ｔ／３）であり、各々の中間層の厚さはＤの半分（Ｄ／２）である。   FIG. 17 shows the calculation result of the transmission loss characteristic with respect to the total thickness t of the metal layers of the polarizer having a triple lattice structure in which the cross section of the periodic structure has a triangular wave shape. In FIG. 17, the solid line indicates the characteristics in the case of a triple lattice structure (three metal layers) in which the total thickness D of the intermediate layer is 2.5 μm, and the broken line indicates that the thickness D of the intermediate layer is 0. That is, the characteristics in the case of a single metal layer are shown. In the case of the triple lattice structure, the thickness of each metal layer is one third (t / 3) of t, and the thickness of each intermediate layer is half of D (D / 2).

図１６、図１７のいずれの場合も、金属層の合計の厚さｔの増加に伴い、ＴＥ波、ＴＭ波ともに透過損失が増加する。どちらの断面形状においてもｔ＞１５ｎｍとなると、Ｄ＝２．５μｍの場合では、Ｄ＝０の場合と比較し、ＴＭ波の透過損失（偏光子としての挿入損失）の増加を大きく低減できる。従って、金属層の合計の厚さｔは、上述の表皮深さ程度にするのが望ましい。   In both cases of FIG. 16 and FIG. 17, the transmission loss increases for both the TE wave and the TM wave as the total thickness t of the metal layer increases. In both cross-sectional shapes, when t> 15 nm, the increase in TM wave transmission loss (insertion loss as a polarizer) can be greatly reduced in the case of D = 2.5 μm compared to the case of D = 0. Therefore, it is desirable that the total thickness t of the metal layers be about the above-mentioned skin depth.

Ｄ＝２．５μｍの場合において、断面形状による特性を比較すると、三角波形状の断面では、正弦波形状と比較し、膜厚が厚くなったときの挿入損失増加を低減でき、ＴＥ波の透過損失は、ｔ＝１０〜５０ｎｍの全域で約５ｄＢ高い。以上より、三重格子構造偏光子の場合、三角波形状の方が良好な偏光特性を得られ、加えて金属層の作製トレランスが高いことがわかる。   In the case of D = 2.5 μm, when the characteristics due to the cross-sectional shape are compared, the increase in insertion loss when the film thickness is increased in the triangular wave-shaped cross section, and the TE wave transmission loss is reduced. Is about 5 dB higher in the entire region of t = 10 to 50 nm. From the above, it can be seen that in the case of a triple lattice structure polarizer, a triangular wave shape can provide better polarization characteristics, and in addition, the metal layer can be produced with higher tolerance.

［解析例３］
四重格子構造（金属層が四層）について、厳密結合波解析（ＲＣＷＡ）法を用いた数値解析によって、（Ａ）中間層厚依存性、（Ｂ）金属層厚依存性を解析した。
これらの数値解析では、入射光の波長λを１０μｍ、周期構造の周期Λを２．５μｍ、基材１１及び中間層の材質をＳｉ（ｎ＝３．４、κ＝０）、金属層をＡｌ（屈折率ｎ＝２５．３、消衰係数κ＝８９．８）と仮定している。 [Analysis Example 3]
With respect to the quadruple lattice structure (four metal layers), (A) intermediate layer thickness dependency and (B) metal layer thickness dependency were analyzed by numerical analysis using a rigorous coupled wave analysis (RCWA) method.
In these numerical analyses, the wavelength λ of the incident light is 10 μm, the period Λ of the periodic structure is 2.5 μm, the base material 11 and the intermediate layer are made of Si (n = 3.4, κ = 0), and the metal layer is made of Al. (Refractive index n = 25.3, extinction coefficient κ = 89.8) is assumed.

（Ａ）中間層厚依存性
上述の図１１は、中間層の合計の厚さＤに対するＴＥ波とＴＭ波の透過損失特性を示している。この数値解析では、アスペクト比ｈ／Λを１、四重格子（金属層が四層）を構成する金属層の合計の厚さｔを１８μｍ（各金属層の厚さは各々４．５μｍ）としている。上述の図１１中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 (A) Dependence on Intermediate Layer Thickness FIG. 11 described above shows the transmission loss characteristics of the TE wave and the TM wave with respect to the total thickness D of the intermediate layer. In this numerical analysis, the aspect ratio h / Λ is 1, and the total thickness t of the metal layers constituting the quadruple lattice (four metal layers) is 18 μm (the thickness of each metal layer is 4.5 μm each). Yes. In FIG. 11 described above, the solid line indicates the characteristic when the cross section of the periodic structure has a sine wave shape, and the broken line indicates the characteristic when the cross section of the periodic structure has a triangular wave shape.

周期構造の断面が正弦波形状及び三角波形状のいずれも、中間層の合計の厚さＤが厚くなるに伴い、ＴＭ波の透過損失は減少する。一方、ＴＥ波の透過損失は、周期構造の断面が正弦波形状の場合にはＤ＝２．５μｍ付近で最大となる。周期構造の断面が三角波形状の場合には、Ｄ＝３．５μｍ付近でＴＥ波の透過損失が最大となる。三角波形状の断面では、正弦波形状と比較し、ＴＥ波の透過損失が高く、Ｄ＝０（単層膜）のときに比べ、消光比が５０ｄＢ以上向上する。以上より、四重格子構造の場合、周期構造の断面は三角波形状、中間層の合計の厚さＤを３．５μｍ（各中間層の厚さがＤ／３＝１．１６７μｍ）とすることが望ましい。   In both the sinusoidal and triangular wave sections of the periodic structure, the TM wave transmission loss decreases as the total thickness D of the intermediate layer increases. On the other hand, the transmission loss of the TE wave is maximized in the vicinity of D = 2.5 μm when the cross section of the periodic structure is sinusoidal. When the cross section of the periodic structure has a triangular wave shape, the TE wave transmission loss is maximized in the vicinity of D = 3.5 μm. In the cross section of the triangular wave shape, the TE wave transmission loss is higher than that of the sine wave shape, and the extinction ratio is improved by 50 dB or more compared to the case of D = 0 (single layer film). From the above, in the case of the quadruple lattice structure, the cross section of the periodic structure has a triangular wave shape, and the total thickness D of the intermediate layers is 3.5 μm (the thickness of each intermediate layer is D / 3 = 1.167 μm). desirable.

（Ｂ）金属層厚依存性
図１８及び図１９は、周期構造の断面が正弦波形状及び三角波形状の四重格子構造となっている偏光子の、金属層の合計の厚さｔに対する透過損失特性の計算結果を示している。図１８は、中間層の合計の厚さが２．５μｍ（正弦波形状で消光比最大）である場合の特性を示しており、図１９は、中間層の合計の厚さが３．５μｍ（三角波形状で消光比最大）である場合の特性を示している。また、図１８及び図１９において、実線は正弦波形状の場合の特性を示しており、破線は三角波形状の場合の特性を示している。なお、四重格子構造の場合は各々の金属層の厚さはｔの４分の１（ｔ／４）であり、各々の中間層の厚さはＤの３分の１（Ｄ／３）である。 (B) Dependence on Metal Layer Thickness FIGS. 18 and 19 show transmission loss with respect to the total thickness t of the metal layer of a polarizer having a quadruple lattice structure in which the cross section of the periodic structure has a sine wave shape and a triangular wave shape. The calculation result of the characteristic is shown. FIG. 18 shows characteristics when the total thickness of the intermediate layer is 2.5 μm (sinusoidal shape and maximum extinction ratio), and FIG. 19 shows the total thickness of the intermediate layer is 3.5 μm ( The characteristic in the case of a triangular wave shape with a maximum extinction ratio) is shown. In FIG. 18 and FIG. 19, the solid line indicates the characteristic in the case of the sine wave shape, and the broken line indicates the characteristic in the case of the triangular wave shape. In the case of a quadruple lattice structure, the thickness of each metal layer is 1/4 of t (t / 4), and the thickness of each intermediate layer is 1/3 of D (D / 3). It is.

図１８、図１９から、金属層厚の増加に伴い、ＴＥ波、ＴＭ波ともに透過損失が増加する。断面形状による特性を比較すると、Ｄ＝２．５μｍの場合、三角波形状の断面では正弦波形状に比べ、膜厚が厚くなったときの挿入損失増加を低減でき、ＴＥ波の透過損失は高くなっている。Ｄ＝３．５μｍの場合、挿入損失はｔ＝１０〜５０ｎｍにおいて断面形状による違いは見られないが、三角波形状の方が正弦波形状に比べ、ＴＥ波の透過損失が非常に高い。以上より、四重格子構造偏光子の場合、三角波形状の方が良好な偏光特性を得られ、加えてＤが薄いとき、金属層の作製トレランスが高いことがわかる。   18 and 19, the transmission loss increases for both the TE wave and the TM wave as the metal layer thickness increases. Comparing the characteristics depending on the cross-sectional shape, when D = 2.5 μm, the triangular wave-shaped cross section can reduce the increase in insertion loss when the film thickness is thicker and the TE wave transmission loss is higher than the sine wave shape. ing. In the case of D = 3.5 μm, the insertion loss is not different depending on the cross-sectional shape at t = 10 to 50 nm, but the transmission loss of the TE wave is much higher in the triangular wave shape than in the sine wave shape. From the above, in the case of a quadruple lattice structure polarizer, it can be seen that the triangular wave shape can provide better polarization characteristics, and when D is thin, the tolerance for forming the metal layer is high.

［解析例４］
（光学特性の波長依存性）
上述の図９及び図１４に示す構造パラメータの中間層厚依存性により得られた、消光比が最大となる中間層Ｓｉの合計の厚さを用い、二重及び三重格子構造の偏光子について、パラメータを入射波長λとしてＲＣＷＡ法により数値解析を行った。この解析では、周期構造の周期（格子周期）Λ＝２．５μｍ、構造のアスペクト比ｈ／Λ＝１、金属層Ａｌの合計の厚さｔ＝２０ｎｍと仮定する。 [Analysis Example 4]
(Wavelength dependence of optical properties)
For the polarizers of the double and triple lattice structure, using the total thickness of the intermediate layer Si with the maximum extinction ratio obtained by the dependency of the structural parameters shown in FIGS. 9 and 14 on the intermediate layer thickness. Numerical analysis was performed by the RCWA method with the parameter being the incident wavelength λ. In this analysis, it is assumed that the period of the periodic structure (lattice period) Λ = 2.5 μm, the aspect ratio h / Λ = 1 of the structure, and the total thickness t of the metal layer Al = 20 nm.

（Ａ）二重格子構造
図２０に、正弦波形状及び三角波形状の断面を持ち、二重格子構造となっている偏光子の、入射波長に対する透過損失特性の計算結果を示す。この図２０中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 (A) Double grating structure FIG. 20 shows a calculation result of transmission loss characteristics with respect to an incident wavelength of a polarizer having a sine wave shape and a triangular wave shape in a double grating structure. In FIG. 20, the solid line indicates the characteristics when the cross section of the periodic structure has a sine wave shape, and the broken line indicates the characteristics when the cross section of the periodic structure has a triangular wave shape.

中間層Ｓｉの厚さをＤ＝１．５μｍと仮定する。断面形状による特性を比較すると、今回用いたパラメータでは、λ＝１０μｍにおいて、三角波形状の方が正弦波形状に比べ低挿入損失であるが、特性の違いは僅かといえる。λ＝１０〜３０μｍにおいて、消光比６０ｄＢ以上が得られる。   Assume that the thickness of the intermediate layer Si is D = 1.5 μm. Comparing the characteristics according to the cross-sectional shape, with the parameters used this time, at λ = 10 μm, the triangular wave shape has a lower insertion loss than the sine wave shape, but it can be said that the characteristic difference is slight. An extinction ratio of 60 dB or more is obtained at λ = 10 to 30 μm.

（Ｂ）三重格子構造
図２１に、正弦波形状及び三角波形状の断面を持ち、二重格子構造となっている偏光子の、入射波長に対する透過損失特性の計算結果を示す。この図２１中において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。 (B) Triple grating structure FIG. 21 shows a calculation result of transmission loss characteristics with respect to an incident wavelength of a polarizer having a sine wave and triangular wave cross section and having a double grating structure. In FIG. 21, the solid line shows the characteristic when the cross section of the periodic structure has a sinusoidal shape, and the broken line shows the characteristic when the cross section of the periodic structure has a triangular wave shape.

中間層Ｓｉの厚さをＤ＝２．５μｍと仮定する。断面形状による特性を比較すると、今回用いたパラメータでは、三角波形状の方が正弦波形状に比べ高消光比である。λ＝１０〜３０μｍにおいて、消光比７０ｄＢ以上が得られる。   Assume that the thickness of the intermediate layer Si is D = 2.5 μm. Comparing the characteristics depending on the cross-sectional shape, the triangular wave shape has a higher extinction ratio than the sine wave shape in the parameters used this time. An extinction ratio of 70 dB or more is obtained at λ = 10 to 30 μm.

［解析例５］
（金属層厚の割合が変化した場合の透過損失特性）
図２２に示すように、二重格子構造の偏光子２０において、金属層２２と金属層２４の厚さをそれぞれｔ１、ｔ２とする。また、入射波長λを１０μｍ、周期構造の周期Λを２．５μ、アスペクト比ｈ／Λを１、中間層２３の厚さＤを１．５μｍとし、金属層２２及び金属層２４をＡｌ、基材１１及び中間層１３をＳｉと仮定する。 [Analysis Example 5]
(Transmission loss characteristics when the ratio of metal layer thickness changes)
As shown in FIG. 22, in the polarizer 20 having a double lattice structure, the thicknesses of the metal layer 22 and the metal layer 24 are t1 and t2, respectively. Further, the incident wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μ, the aspect ratio h / Λ is 1, the thickness D of the intermediate layer 23 is 1.5 μm, and the metal layer 22 and the metal layer 24 are made of Al. The material 11 and the intermediate layer 13 are assumed to be Si.

このような条件で、周期構造の断面が正弦波形状及び三角波形状である二重格子構造となっている偏光子の、金属層の合計の厚さｔを２０ｎｍとし、各金属層の厚さｔ１、ｔ２に対する透過損失特性を求めると、図２３に示すようになる。この図２３において、実線は周期構造の断面が正弦波形状の場合の特性を示しており、破線は周期構造の断面が三角波形状の場合の特性を示している。   Under such conditions, the total thickness t of the metal layers of the polarizer having a double lattice structure in which the cross section of the periodic structure has a sine wave shape and a triangular wave shape is set to 20 nm, and the thickness t1 of each metal layer. FIG. 23 shows the transmission loss characteristics with respect to t2. In FIG. 23, the solid line indicates the characteristics when the cross section of the periodic structure has a sine wave shape, and the broken line indicates the characteristics when the cross section of the periodic structure has a triangular wave shape.

周期構造の断面が正弦波形状及び三角波形状のいずれの断面形状においても、ｔ１及びｔ２が１０ｎｍ付近のときに、ＴＥ波の透過損失が最も高くなり、ＴＭ波の透過損失が最も低くなる。以上より，金属層厚の割合は二重格子構造の場合、ｔ１＝ｔ２＝ｔ／２となるように、同様の厚さとすることが望ましい。   Regardless of whether the periodic structure has a sine wave or triangular wave cross section, when t1 and t2 are around 10 nm, the TE wave transmission loss is the highest and the TM wave transmission loss is the lowest. From the above, in the case of the double lattice structure, it is desirable that the metal layer thickness has the same thickness so that t1 = t2 = t / 2.

［解析例６］
（波長に対する中間層厚依存性）
二重及び三重格子構造の偏光子において、波長に応じて構造を変え、構造パラメータを中間層の合計の厚さＤとして数値解析を行った。 [Analysis Example 6]
(Dependence of interlayer thickness on wavelength)
In the double and triple lattice polarizers, the structure was changed according to the wavelength, and the numerical analysis was performed with the structural parameter as the total thickness D of the intermediate layer.

（Ａ）二重格子構造
上述の図５は、正弦波形状及び三角波形状の断面を持ち、二重格子構造となっている偏光子の、波長λが１μｍの場合での中間層の厚さに対する透過損失特性の計算結果を示す。周期構造の周期Λを２５０ｎｍ、アスペクト比ｈ／Λを１、金属層の合計の厚さｔ＝１８ｎｍ（ｔ／２＝９ｎｍ）、金属層をＡｌ（ｎ＝１．３５、κ＝９．５８）、基材をＴｓｕｒｕｐｉｃａ（登録商標）（ｎ＝１．５３、κ＝０）、中間層をＳｉＯ２（ｎ＝１．４５、κ＝０）と仮定する。 (A) Double-grating structure FIG. 5 described above shows the thickness of the intermediate layer when the wavelength λ is 1 μm of a polarizer having a sine wave-shaped and triangular wave-shaped cross section and having a double-grating structure. The calculation result of the transmission loss characteristic is shown. The period Λ of the periodic structure is 250 nm, the aspect ratio h / Λ is 1, the total thickness of the metal layer t = 18 nm (t / 2 = 9 nm), and the metal layer is Al (n = 1.35, κ = 9.58). ), The substrate is assumed to be Tsurpica (registered trademark) (n = 1.53, κ = 0), and the intermediate layer is assumed to be SiO 2 (n = 1.45, κ = 0).

中間層の厚さＤの増加に伴い、ＴＭ波の透過損失は減少し、Ｄ＞２００ｎｍでは一定となる。一方、ＴＥ波の透過損失は、Ｄの増加に伴い、中間層厚による干渉を繰り返し波打った特性となる。Ｄ＝１５０ｎｍ付近でＴＥ波の透過損失は最大となり、Ｄ＝０（単層膜）のときに比べ、消光比が約５ｄＢ向上する。   As the thickness D of the intermediate layer increases, the TM wave transmission loss decreases and becomes constant when D> 200 nm. On the other hand, the transmission loss of the TE wave has a characteristic in which the interference due to the intermediate layer thickness is repeatedly waved as D increases. The transmission loss of the TE wave is maximized in the vicinity of D = 150 nm, and the extinction ratio is improved by about 5 dB compared to when D = 0 (single layer film).

図２４に、正弦波形状及び三角波形状の断面を持ち、二重格子構造となっている偏光子の、波長λが２０μｍの場合での中間層の厚さに対する透過損失特性の計算結果を示す。周期構造の周期Λを５μｍ、アスペクト比ｈ／Λを１、金属層の合計の厚さｔ＝１８ｎｍ（ｔ／２＝９ｎｍ）、金属層をＡｌ（ｎ＝６０．７、κ＝１４７）、基材及び中間層をＳｉ（ｎ＝３．４、κ＝０）と仮定する。   FIG. 24 shows a calculation result of transmission loss characteristics with respect to the thickness of the intermediate layer of a polarizer having a sine wave shape and a triangular wave shape cross section and having a double grating structure when the wavelength λ is 20 μm. The period Λ of the periodic structure is 5 μm, the aspect ratio h / Λ is 1, the total thickness of the metal layer t = 18 nm (t / 2 = 9 nm), the metal layer is Al (n = 60.7, κ = 147), The substrate and intermediate layer are assumed to be Si (n = 3.4, κ = 0).

中間層の厚さＤの増加に伴い、ＴＭ波の透過損失は減少する。一方、ＴＥ波の透過損失はＤの増加とともに増加し、Ｄ＝３μｍ付近で最大となり、Ｄ＝０（単層膜）のときに比べ、消光比が２０ｄＢ以上向上する。   As the thickness D of the intermediate layer increases, the TM wave transmission loss decreases. On the other hand, the transmission loss of the TE wave increases with an increase in D, reaches a maximum in the vicinity of D = 3 μm, and improves the extinction ratio by 20 dB or more compared to when D = 0 (single layer film).

以上より、二重格子構造の場合、中間層厚を波長λが１μｍの場合で中間層の厚さＤを１５０ｎｍとし、λ＝２０μｍでＤ＝３μｍとすることが望ましく、上述の解析例１（Ａ）の結果からλ＝１０μｍにおいてはＤ＝１．５μｍとすることで最良となるため、波長に対して中間層厚をＤ＝０．１５λと設定したときに、ＴＥ波の透過損失が最大になると考えられる。また、これらの上述の図５、図２４から、中間層の厚さＤを０．０８λ〜０．２５λ程度にすれば、良好な特性を得ることができる。   From the above, in the case of the double lattice structure, it is desirable that the thickness D of the intermediate layer is 150 nm when the wavelength λ is 1 μm, and D = 3 μm when λ = 20 μm. From the result of A), when λ = 10 μm, it is best to set D = 1.5 μm. Therefore, when the thickness of the intermediate layer is set to D = 0.15λ with respect to the wavelength, the TE wave transmission loss is maximum. It is thought to become. Further, from these FIGS. 5 and 24, if the thickness D of the intermediate layer is set to about 0.08λ to 0.25λ, good characteristics can be obtained.

（Ｂ）三重格子構造
図２５に、正弦波形状及び三角波形状の断面を持ち、三重格子構造となっている偏光子の、波長λが１μｍでの中間層の厚さに対する透過損失特性の計算結果を示す。周期構造の周期Λを２５０ｎｍ、アスペクトｈ／Λを１、金属層の合計の厚さｔ＝１８ｎｍ（ｔ／３＝６ｎｍ）、金属層をＡｌ、基材をＴｓｕｒｕｐｉｃａ（登録商標）、中間層をＳｉＯ２と仮定する。 (B) Triple grating structure FIG. 25 shows a calculation result of transmission loss characteristics with respect to the thickness of the intermediate layer of a polarizer having a sine wave shape and a triangular wave cross section and having a triple grating structure at a wavelength λ of 1 μm. Indicates. The period Λ of the periodic structure is 250 nm, the aspect h / Λ is 1, the total thickness of the metal layer t = 18 nm (t / 3 = 6 nm), the metal layer is Al, the substrate is Tsurpica (registered trademark), and the intermediate layer is Assume SiO 2 .

中間層の合計の厚さＤの増加に伴い、ＴＭ波の透過損失は減少する。周期構造の断面の形状が正弦波形状の場合、Ｄ＝４００ｎｍ付近でＴＭ波の透過損失が増加しているのは、特定の中間層厚において干渉が起きているためと考えられる。一方、ＴＥ波の透過損失はＤの増加とともに増加し、正弦波形状の場合には、Ｄ＝２００ｎｍ付近で最大となる。三角波形状の場合には、Ｄ＝２５０ｎｍ付近で最大となる。三角波状の断面形状では正弦波状に比べ、ＴＥ波の透過損失が高くなっている。Ｄ＝０（単層膜）のときに比べ、正弦波形状で消光比が約５ｄＢ向上、三角波形状で約７ｄＢ向上する。   As the total thickness D of the intermediate layer increases, the TM wave transmission loss decreases. When the cross-sectional shape of the periodic structure is sinusoidal, the TM wave transmission loss increases near D = 400 nm because interference occurs at a specific intermediate layer thickness. On the other hand, the transmission loss of the TE wave increases with an increase in D. In the case of a sine wave shape, the transmission loss becomes maximum at around D = 200 nm. In the case of a triangular wave shape, the maximum is in the vicinity of D = 250 nm. The triangular wave cross-sectional shape has a higher TE wave transmission loss than the sine wave shape. Compared to D = 0 (single layer film), the extinction ratio is improved by about 5 dB in the sine wave shape, and is improved by about 7 dB in the triangular wave shape.

図２６に、正弦波形状及び三角波形状の断面を持ち、三重格子構造となっている偏光子の、波長λが２０μｍでの中間層の厚さに対する透過損失特性の計算結果を示す。周期構造の周期Λを５μｍ、アスペクト比ｈ／Λを１、金属層の合計の厚さｔ＝１８ｎｍ（ｔ／３＝６ｎｍ）、金属層をＡｌ、基材及び中間層をＳｉと仮定する。   FIG. 26 shows a calculation result of transmission loss characteristics with respect to the thickness of the intermediate layer of a polarizer having a sinusoidal and triangular wave cross section and having a triple lattice structure and a wavelength λ of 20 μm. It is assumed that the period Λ of the periodic structure is 5 μm, the aspect ratio h / Λ is 1, the total thickness of the metal layer t = 18 nm (t / 3 = 6 nm), the metal layer is Al, and the base material and the intermediate layer are Si.

中間層の合計の厚さＤの増加に伴い、ＴＭ波の透過損失は減少する。一方、ＴＥ波の透過損失はＤの増加とともに増加し、正弦波形状の場合にはＤ＝５μｍ付近で最大となる。三角波形状の場合にはＤ＝６μｍ付近で最大となり、Ｄ＝０（単層膜）のときに比べ、消光比が４０ｄＢ以上向上する。三角波状の断面形状では正弦波状に比べ、ＴＥ波の透過損失が高く、Ｄ＜６μｍのときＴＭ波の透過損失が低くなっている。   As the total thickness D of the intermediate layer increases, the TM wave transmission loss decreases. On the other hand, the transmission loss of the TE wave increases with an increase in D. In the case of a sine wave shape, the transmission loss becomes maximum around D = 5 μm. In the case of a triangular wave shape, the maximum is obtained in the vicinity of D = 6 μm, and the extinction ratio is improved by 40 dB or more compared to the case of D = 0 (single layer film). The triangular wave cross-sectional shape has a higher TE wave transmission loss than the sinusoidal wave shape, and the TM wave transmission loss is lower when D <6 μm.

以上より、三重格子構造の場合、正弦波形状では中間層厚を波長λ＝１μｍでＤ＝２００ｎｍ、波長λ＝２０μｍでＤ＝５μｍとすることが望ましい。また、三角波形状では波長λ＝１μｍでＤ＝２５０ｎｍ、波長λ＝２０μｍでＤ＝６μｍとすることが望ましい。上述の解析例２（Ａ）の結果からλ＝１０μｍにおいてはＤ＝２．５μｍとすることで最良となるため、波長に対して中間層の合計の厚さＤを、正弦波形状の場合ではＤ＝０．２０λ〜０．２５λ、三角波形状の場合ではＤ＝０．２５λ〜０．３０λと設定したときに、ＴＥ波の透過損失が最大になると考えられる。   From the above, in the case of the triple lattice structure, in the sine wave shape, it is desirable that the intermediate layer thickness is D = 200 nm at the wavelength λ = 1 μm, and D = 5 μm at the wavelength λ = 20 μm. In the triangular wave shape, it is desirable that D = 250 nm at a wavelength λ = 1 μm, and D = 6 μm at a wavelength λ = 20 μm. From the result of the above-mentioned analysis example 2 (A), when λ = 10 μm, it is best to set D = 2.5 μm. Therefore, the total thickness D of the intermediate layer with respect to the wavelength is set to be sinusoidal. In the case of D = 0.20λ to 0.25λ and triangular wave shape, it is considered that the transmission loss of TE wave is maximized when D = 0.25λ to 0.30λ.

［解析例７］
（中間層を厚くした場合）
多重格子構造において、中間層が非常に厚くなったとき、一層当たりの金属層厚とした金属単層膜の偏光子における透過損失を倍とした値に漸近するかを確認する。上述の図１０、図２７及びこれらをまとめた図２８に、正弦波状及び三角波状の断面形状を持ち、二重格子構造となっている偏光子の、中間層の厚さ（Ｄ＝０〜３μｍ［上述の図１０］、Ｄ＝３５〜５０μｍ［図２７］）に対する透過損失特性の計算結果を示す。 [Analysis Example 7]
(When the intermediate layer is thickened)
In the multi-grating structure, when the intermediate layer becomes very thick, it is confirmed whether or not the transmission loss in the polarizer of the metal single layer film having the metal layer thickness per layer is gradually approached. 10 and 27 described above and FIG. 28 in which these are combined, the thickness of the intermediate layer (D = 0 to 3 μm) of the polarizer having a sine wave and triangular wave cross section and having a double lattice structure. [The above-mentioned FIG. 10] and the calculation result of the transmission loss characteristic with respect to D = 35-50 micrometers [FIG.

ここで、波長λを１０μｍ、周期構造の周期Λを２．５μｍ、アスペクト比ｈ／Λ＝１、金属層の合計の厚さｔ＝１８ｎｍ（ｔ／２＝９ｎｍ）とし、金属層をＡｌ、基材及び中間層をＳｉと仮定する。   Here, the wavelength λ is 10 μm, the period Λ of the periodic structure is 2.5 μm, the aspect ratio h / Λ = 1, the total thickness t = 18 nm (t / 2 = 9 nm), and the metal layer is made of Al, Assume that the substrate and intermediate layer are Si.

中間層の厚さＤが増加すると、ＴＭ波の透過損失は、どちらの断面形状においても０．５ｄＢ以下で安定しているが、ＴＥの透過損失は、Ｄとともに増加し３０〜４０ｄＢとなっている。ここで、ｔ＝９ｎｍである金属単層膜の偏光子の損失を２倍すると、正弦波形状では、ＴＥ波の透過損失４７．３ｄＢ、ＴＭ波の透過損失０．５０４ｄＢ、三角波形状では、ＴＥ波の透過損失４９．２ｄＢ、ＴＭ波の透過損失０．２２０ｄＢである。以上より、Ｄが増加したとき、ＴＭ波の透過損失は、金属単層膜の特性の２倍に漸近しているといえる。ＴＥ波の透過損失は、Ｄ＝５０μｍではまだ十分に漸近していないが、さらにＤが増加した場合、漸近していくと考えられる。   When the thickness D of the intermediate layer increases, the transmission loss of TM waves is stable at 0.5 dB or less in both cross-sectional shapes, but the transmission loss of TE increases with D to 30 to 40 dB. Yes. Here, when the loss of the polarizer of the metal single layer film with t = 9 nm is doubled, the transmission loss of TE wave is 47.3 dB in the sinusoidal shape, the transmission loss of 0.504 dB in TM wave, and the TE loss is in the triangular wave shape. The wave transmission loss is 49.2 dB, and the TM wave transmission loss is 0.220 dB. From the above, it can be said that when D increases, the transmission loss of TM waves is asymptotic to twice the characteristics of the metal single layer film. The transmission loss of the TE wave is not asymptotic yet sufficiently when D = 50 μm, but it is considered that the transmission loss becomes asymptotic when D further increases.

（結論）
以上説明したように、金属薄膜サブ波長多重格子構造偏光子を提案した。中赤外域における偏光特性の数値解析結果について報告した。数値解析により、λ＝１０μｍにおいて、中間層Ｓｉ（屈折率３．４）の厚さを二重格子構造の場合Ｄ＝１．５μｍ（図１０より、Ｄ＝波長λ／（２×屈折率）、三重格子構造の場合Ｄ＝２．５μｍ（図１６より）とすることで消光比が最大となる。すなわち、中間層の素材をＳｉとした場合には、波長に対する中間層厚依存性により、二重格子の場合Ｄ＝０．１５λ、三重格子の場合Ｄ＝０．２０λ〜０．２５λ（正弦波状）、Ｄ＝０．２５λ〜０．３０λ（三角波状）とすることで高い偏光特性が得られる。これらのシミュレーション結果より、中間層の合計の厚さＤは、これらの値の±６０％程度の値が妥当であると考えられる。 (Conclusion)
As described above, a metal thin film subwavelength multiple grating structure polarizer has been proposed. The numerical analysis results of polarization characteristics in the mid-infrared region are reported. According to numerical analysis, when λ = 10 μm, the thickness of the intermediate layer Si (refractive index 3.4) is D = 1.5 μm in the case of a double lattice structure (from FIG. In the case of a triple lattice structure, the extinction ratio is maximized by setting D = 2.5 μm (from FIG. 16), that is, when the material of the intermediate layer is Si, due to the dependency of the intermediate layer thickness on the wavelength, In the case of a double grating D = 0.15λ, in the case of a triple grating D = 0.20λ to 0.25λ (sinusoidal), and D = 0.25λ to 0.30λ (triangular wave), high polarization characteristics. From these simulation results, it is considered that the value of about ± 60% of these values is appropriate for the total thickness D of the intermediate layer.

なお、この値は、中間層の屈折率に応じて変わるため、中間層の材質をＳｉＯ２をとした場合には、三重格子の場合には、中間層の合計の厚さの上限をＤ＝０．５８λ（正弦波状）程度、Ｄ＝０．７λ（三角波状）とすることが望ましい。 Since this value varies depending on the refractive index of the intermediate layer, when the material of the intermediate layer is SiO 2 , in the case of a triple lattice, the upper limit of the total thickness of the intermediate layer is D = It is desirable to set about 0.58λ (sinusoidal) and D = 0.7λ (triangular).

また、これらのシミュレーション結果により、λ＝１０〜３０μｍにおいて、二重格子構造で消光比理論値６０ｄＢ以上、三重格子構造で７０ｄＢ以上が得られ、金属薄膜サブ波長格子を多重化することで、中赤外域において良好な偏光特性が得られることが分かる。   Also, from these simulation results, at λ = 10 to 30 μm, a theoretical extinction ratio of 60 dB or more is obtained with a double lattice structure, and 70 dB or more with a triple lattice structure. By multiplexing metal thin film subwavelength gratings, It can be seen that good polarization characteristics can be obtained in the infrared region.

３ 表面
４ 尾根部
５ 谷部
１０ 偏光子
１１ 基材
１２ 金属層
１３ 中間層
１４ 金属層
２０ 偏光子
２１ 基材
２２ 金属層
２３ 中間層
２４ 金属層 3 Surface 4 Ridge 5 Valley 9 Polarizer 11 Base 12 Metal Layer 13 Intermediate Layer 14 Metal Layer 20 Polarizer 21 Base 22 Metal Layer 23 Intermediate Layer 24 Metal Layer

Λ 構造周期のピッチ
ｈ 周期構造（三角波形状又は正弦波形状）の高さ
Ｄ 中間層
ｔ 金属層の合計の厚さ Λ Pitch of structure period h Height of periodic structure (triangular wave shape or sine wave shape) D Intermediate layer t Total thickness of metal layer

Claims (6)

基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化する単位構造をλ（入射する電磁波の波長）より小さな周期で繰り返す周期構造を有した基材と、前記周期構造の表面に中間層を介して複数設けられた金属層と、を有することを特徴とする偏光子。   A base material having a periodic structure in which a unit structure whose occupation ratio continuously changes with respect to an electromagnetic wave incident on the base material surface at a predetermined angle is repeated with a period smaller than λ (wavelength of the incident electromagnetic wave), and the periodic structure And a plurality of metal layers provided on the surface of the polarizer with an intermediate layer interposed therebetween. 前記周期構造の断面が三角波形状又は正弦波形状である、請求項１に記載の偏光子。   The polarizer of Claim 1 whose cross section of the said periodic structure is a triangular wave shape or a sine wave shape. 前記金属層が二層であり、前記中間層の厚さが０より大きくλ／ｎ以下である、請求項１または２に記載の偏光子。   3. The polarizer according to claim 1, wherein the metal layer has two layers, and the thickness of the intermediate layer is greater than 0 and equal to or less than λ / n. 基材面に所定の角度で入射する電磁波に対して占有率が連続的に変化する単位構造をλ（入射する電磁波の波長）より小さな周期で繰り返す周期構造を前記基材面に形成する工程と、
前記周期構造の表面に金属層を形成する工程と、
前記金属層の表面に中間層を形成する工程と、
前記中間層の表面に金属層を形成する工程と、を有することを特徴とする偏光子の製造方法。 Forming a periodic structure on the substrate surface that repeats a unit structure whose occupancy continuously changes with respect to electromagnetic waves incident on the substrate surface at a predetermined angle with a period smaller than λ (wavelength of incident electromagnetic waves); ,
Forming a metal layer on the surface of the periodic structure;
Forming an intermediate layer on the surface of the metal layer;
And a step of forming a metal layer on the surface of the intermediate layer. 前記周期構造の断面が三角波形状又は正弦波形状である、請求項４に記載の偏光子の製造方法。   The method for manufacturing a polarizer according to claim 4, wherein a cross section of the periodic structure has a triangular wave shape or a sine wave shape. 請求項１〜５のいずれか１項に記載の偏光子を用いたことを特徴とする光モジュール。   An optical module comprising the polarizer according to claim 1.
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WO2008018247A1 (en) * 2006-08-09 2008-02-14 Nippon Sheet Glass Company, Limited Transmission type polarizing element, and complex polarizing plate using the element
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JP2000258645A (en) * 1999-03-08 2000-09-22 Nippon Telegr & Teleph Corp <Ntt> Three-dimensional periodic structure and two- dimensional periodic structure as well as their manufacture
WO2008018247A1 (en) * 2006-08-09 2008-02-14 Nippon Sheet Glass Company, Limited Transmission type polarizing element, and complex polarizing plate using the element
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JP2009128879A (en) * 2007-11-28 2009-06-11 Ricoh Opt Ind Co Ltd Optical isolator using photonic crystal and method of manufacturing the same
JP2010256840A (en) * 2009-03-29 2010-11-11 Utsunomiya Univ Polarizer, method for manufacturing the same, and optical module

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Publication number Priority date Publication date Assignee Title
JP2014191062A (en) * 2013-03-26 2014-10-06 Seiko Epson Corp Method for manufacturing polarizing element, polarizing element, liquid crystal device, and electronic equipment

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