JP4646126B2 - Photonic crystal fabrication method using diffractive optical element - Google Patents

Photonic crystal fabrication method using diffractive optical element Download PDF

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JP4646126B2
JP4646126B2 JP2005286949A JP2005286949A JP4646126B2 JP 4646126 B2 JP4646126 B2 JP 4646126B2 JP 2005286949 A JP2005286949 A JP 2005286949A JP 2005286949 A JP2005286949 A JP 2005286949A JP 4646126 B2 JP4646126 B2 JP 4646126B2
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公夫 伊藤
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Dai Nippon Printing Co Ltd
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Description

本発明は、回折光学素子を用いたフォトニック結晶作製方法に関し、特に、光ビーム分割素子等の光学素子として使用可能な回折光学素子を用いた２次元的、３次元的フォトニック結晶作製方法に関するものである。   The present invention relates to a photonic crystal manufacturing method using a diffractive optical element, and more particularly to a two-dimensional and three-dimensional photonic crystal manufacturing method using a diffractive optical element that can be used as an optical element such as a light beam splitting element. Is.

本願出願人は、特許文献１にて、正方形領域群が碁盤の目状に配置され、隣り合う正方形領域の基準波長光に対する位相差を略πとし、略垂直に入射する光束を４本又は５本の光束に分割する回折光学素子を提案している。   The applicant of the present application disclosed in Patent Document 1 that the square region group is arranged in a grid pattern, the phase difference with respect to the reference wavelength light of the adjacent square regions is approximately π, and four or five light beams incident substantially perpendicularly are used. A diffractive optical element that divides a light beam into a book is proposed.

また、特許文献２においては、透明基板面が同一形状の微細な三角形領域群に分割され、隣り合う三角形領の基準波長光に対する位相差をπとして、略垂直に入射する光束を６本の光束に分割する回折光学素子が提案されている。   Also, in Patent Document 2, the transparent substrate surface is divided into fine triangular region groups having the same shape, and six light beams are incident substantially perpendicularly, where π is a phase difference with respect to the reference wavelength light of adjacent triangular regions. A diffractive optical element that is divided into two parts has been proposed.

一方、非特許文献１において、３つの同じ回折格子を同一マスク面上に相互に１２０°回転配置させて、各回折格子からの回折光を干渉させて六角形アレイを作製している。
特開２００５−７７９６６号公報 米国特許第５，２０８，６２９号明細書 特開２０００−５６１１２号公報 特開２００４−１２６３１２号公報 “Ａｐｐｌ．Ｐｈｙｓ．Ｌｅｔｔ．”，Ｖｏｌ．７９，Ｎｏ．２１，ｐｐ．３３９２〜３３９４ “ＳＰＩＥ”，Ｖｏｌ．８８３（１９８８），ｐｐ．８〜１１ On the other hand, in Non-Patent Document 1, three identical diffraction gratings are mutually rotated by 120 ° on the same mask surface, and the diffracted light from each diffraction grating is caused to interfere to produce a hexagonal array.
JP 2005-77966 A US Pat. No. 5,208,629 JP 2000-56112 A Japanese Patent Laid-Open No. 2004-126312 “Appl. Phys. Lett.”, Vol. 79, no. 21, pp. 3392-3394 “SPIE”, Vol. 883 (1988), p. 8-11

本発明は従来技術のこのような状況に鑑みてなされたものであり、その目的は、入射光を０次透過光１本とそれに対して同じ角度を持ち相互に同じ強さの３本の＋１次光に分割する回折光学素子を用いてフォトニック結晶を作製する方法を提供することである。   The present invention has been made in view of such a situation in the prior art, and its purpose is to make incident light as one zero-order transmitted light and three + 1's having the same angle and the same strength as each other. It is to provide a method for producing a photonic crystal using a diffractive optical element that divides into next light.

上記目的を達成する本発明の回折光学素子を用いたフォトニック結晶作製方法は、透明基板の面上に、正三角形の各辺方向に同じ高さで同じ大きさの凸状の正三角形領域が各辺の長さの周期で繰り返し配列され、前記凸状の正三角形領域の間に向きを上下逆転させた同じ低さで前記凸状の正三角形領域と同じ大きさの凹状の正三角形領域が正三角形の各辺方向に各辺の長さの周期で繰り返し配列され、前記凸状の正三角形領域と前記凹状の正三角形領域が相互に隣接して前記透明基板の表面を密に覆うように配置され、前記透明基板を透過する基準波長光に対して、前記凸状の正三角形領域とそれに隣接する前記凹状の正三角形領域の間に、前記透明基板に垂直に入射する基準波長光に対して位相差がπ未満であり、前記透明基板に垂直に入射する基準波長光を４方向へ分岐するために用いられる回折光学素子をマスクとして用い、前記回折光学素子にフェムト秒レーザ光を入射させ、前記回折光学素子から生じる＋１次回折光同士のみを透明媒体中で干渉させることにより２次元的又は３次元的な微細な周期構造に対応する露光量分布のアレイを発生させ、前記透明媒体中に屈折率変調として記録することを特徴とする方法である。   In the photonic crystal manufacturing method using the diffractive optical element of the present invention that achieves the above object, convex equilateral triangular regions having the same height and the same size are provided on each side of the equilateral triangle on the surface of the transparent substrate. A concave equilateral triangular area having the same height as the convex equilateral triangular area at the same height, which is repeatedly arranged with a period of the length of each side, and whose direction is reversed upside down between the convex equilateral triangular areas. It is repeatedly arranged in the direction of each side of the regular triangle with the period of the length of each side so that the convex regular triangular region and the concave regular triangular region are adjacent to each other and cover the surface of the transparent substrate densely. With respect to the reference wavelength light that is disposed and transmitted through the transparent substrate, the reference wavelength light that is perpendicularly incident on the transparent substrate between the convex equilateral triangular region and the concave equilateral triangular region adjacent thereto. The phase difference is less than π and enters the transparent substrate vertically. A diffractive optical element used for branching the reference wavelength light in four directions is used as a mask, femtosecond laser light is incident on the diffractive optical element, and only + first-order diffracted lights generated from the diffractive optical element are in a transparent medium. To generate an exposure dose distribution array corresponding to a two-dimensional or three-dimensional fine periodic structure, and record it as a refractive index modulation in the transparent medium.

この場合、前記回折光学素子の前記位相差が０．８１π〜０．９９πの範囲にあることが望ましい。   In this case, it is desirable that the phase difference of the diffractive optical element is in the range of 0.81π to 0.99π.

２次元的な微細な周期構造としては、反射防止構造体若しくは２次元フォトニック結晶がある。   As the two-dimensional fine periodic structure, there is an antireflection structure or a two-dimensional photonic crystal.

３次元的な微細な周期構造としては、六方最密充填結晶格子状の３次元フォトニック結晶がある。   As a three-dimensional fine periodic structure, there is a hexagonal close-packed crystal lattice-shaped three-dimensional photonic crystal.

本発明においては、凸状の正三角形領域と凹状の正三角形領域を２次元的に交互に密に配置するだけの簡単な構成で、入射光を０次透過光１本とそれに対して同じ角度を持ち同じ強さの３本の＋１次光に分割することができ、それにフェムト秒レーザ光を入射させることで２次元的、３次元的なフォトニック結晶を作製することができる。   In the present invention, a simple configuration in which convex equilateral triangle regions and concave equilateral triangle regions are arranged two-dimensionally and densely is used, and incident light is incident at the same angle with respect to one zero-order transmitted light. Can be divided into three + 1st order light beams having the same intensity, and a femtosecond laser beam can be incident thereon, thereby producing a two-dimensional or three-dimensional photonic crystal.

以下に、本発明の回折光学素子とそれを用いたフォトニック結晶作製方法を実施例に基づいて説明する。   The diffractive optical element of the present invention and a photonic crystal manufacturing method using the same will be described below based on examples.

本発明の回折光学素子１は、図１に斜視図を示すように、透明基板２の面上に、正三角形の各辺方向に同じ高さで同じ大きさの凸状の正三角形領域３が各辺の長さの周期で繰り返し配列され、その正三角形領域３の間に向きを上下逆転させた同じ低さで正三角形領域３と同じ大きさの凹状の正三角形領域４が同様に正三角形の各辺方向に各辺の長さの周期で繰り返し配列され、凸状の正三角形領域３と凹状の正三角形領域４が相互に隣接して透明基板２の表面を密に覆うようにし、透明基板２を透過する基準波長光に対して、凸状の正三角形領域３とそれに隣接する凹状の正三角形領域４の間に位相差φを与えるように構成されている。   In the diffractive optical element 1 according to the present invention, as shown in a perspective view in FIG. 1, convex equilateral triangular regions 3 having the same height and the same size in each side direction of the equilateral triangle are formed on the surface of the transparent substrate 2. A concave equilateral triangle region 4 having the same height and the same size as the equilateral triangle region 3 is arranged in an equilateral triangle in the same height, which is repeatedly arranged with a period of the length of each side, and the direction is inverted between the equilateral triangle regions 3. The convex regular triangle region 3 and the concave regular triangle region 4 are adjacent to each other so as to cover the surface of the transparent substrate 2 closely and transparently. With respect to the reference wavelength light transmitted through the substrate 2, a phase difference φ is provided between the convex equilateral triangle region 3 and the concave equilateral triangle region 4 adjacent thereto.

そして、本発明においては、ＲＣＷＡ手法あるいはベクトル回折理論（非特許文献２）を用いて、透明基板２に垂直に基準波長λの光を入射させた場合に、回折光学素子１を透過する０次透過光と、その０次透過光に対して同じ角度を持つ３本の＋１次回折光とに分割するようにするための位相差φを求めた。   In the present invention, when the light having the reference wavelength λ is incident on the transparent substrate 2 perpendicularly using the RCWA method or the vector diffraction theory (Non-patent Document 2), the 0th order that passes through the diffractive optical element 1 is transmitted. A phase difference φ for dividing the transmitted light into three + 1st order diffracted lights having the same angle with respect to the zeroth order transmitted light was obtained.

図２に、回折光学素子１と回折光の関係を示す。図２（ａ）は斜視図であり、図２（ｂ）は回折光学素子１の回折側から見た正面図である。透明基板２裏面に垂直に基準波長λの入射光１１を入射させた場合、図２（ｂ）に示すように、０次回折光１２が１本、＋１次回折光１３が３本、−１次回折光１４が３本発生するが、＋１次回折光１３と−１次回折光１４は必ずしも同じ強さで出るとは限らない。位相差φによっては、＋１次回折光１３が相対的に強く、−１次回折光１４が無視できる場合がある。すなわち、位相差φに依存して回折光が４本（０次回折光１２と＋１次回折光１３）から７本（０次回折光１２と＋１次回折光１３と−１次回折光１４）に変化する。なお、＋１次回折光１３は、図２（ｂ）に示すように、回折光学素子１の面に投影したとき、凹状の正三角形領域４の辺に直交する外側方向に射出し、−１次回折光１４は凸状の正三角形領域３の辺に直交する外側方向に射出する。したがって、回折光学素子１の面に投影したとき、＋１次回折光１３相互は１２０°をなし、−１次回折光１４は＋１次回折光１３の方向とは反対の方向を向いている。また、図２（ａ）に示すように、＋１次回折光１３は０次回折光１２に対して３本共同じ角度αをなして回折光学素子１から出る。   FIG. 2 shows the relationship between the diffractive optical element 1 and the diffracted light. 2A is a perspective view, and FIG. 2B is a front view of the diffractive optical element 1 viewed from the diffraction side. When incident light 11 having a reference wavelength λ is incident perpendicularly to the back surface of the transparent substrate 2, as shown in FIG. 2B, one 0th-order diffracted light 12, one + 1st-order diffracted light 13, and −1st-order diffracted light Although three 14 are generated, the + 1st order diffracted light 13 and the −1st order diffracted light 14 do not necessarily have the same intensity. Depending on the phase difference φ, the + 1st order diffracted light 13 may be relatively strong and the −1st order diffracted light 14 may be ignored. That is, depending on the phase difference φ, the number of diffracted lights changes from four (0th order diffracted light 12 and + 1st order diffracted light 13) to 7 (0th order diffracted light 12, + 1st order diffracted light 13 and −1st order diffracted light 14). As shown in FIG. 2 (b), the + 1st order diffracted light 13 is emitted in the outward direction perpendicular to the side of the concave equilateral triangular region 4 when projected onto the surface of the diffractive optical element 1, and the −1st order diffracted light. 14 injects in the outward direction orthogonal to the side of the convex equilateral triangle region 3. Therefore, when projected onto the surface of the diffractive optical element 1, the + 1st order diffracted light 13 forms 120 °, and the −1st order diffracted light 14 faces in a direction opposite to the direction of the + 1st order diffracted light 13. Further, as shown in FIG. 2A, the + 1st order diffracted light 13 exits the diffractive optical element 1 at the same angle α with respect to the 0th order diffracted light 12.

図３に、基準波長λ＝８００ｎｍ、正三角形領域３、４の辺に沿う方向の繰り返し周期１．０７μｍの場合の±１次回折光（±１次光）１３、１４と０次回折光（０次光）１２の回折効率（効率）と位相差φとの関係を求めた結果を示す。なお、他の波長、他の繰り返し周期の場合も同様の傾向を示す。   FIG. 3 shows ± first-order diffracted light (± first-order light) 13 and 14 and zero-order diffracted light (0th-order light) when the reference wavelength λ = 800 nm and the repetition period 1.07 μm in the direction along the sides of the equilateral triangle regions 3 and 4. The result of having calculated | required the relationship between the diffraction efficiency (efficiency) of 12 and the phase difference (phi) is shown. The same tendency is shown for other wavelengths and other repetition periods.

図３の結果から、入射光１１を略同じ強度の０次回折光１２と＋１次回折光１３の４本の光束に分割する用途の場合は、位相差φは、０．７π≦φ＜１．０πの範囲にあることが望ましく、また、後記するように、＋１次回折光１３相互を干渉させてフォトニック結晶構造を作る用途には、０．８π≦φ＜１．０の範囲にあることが望ましく、両者合わせて０．７π≦φ＜１．０、より望ましくは、０．８１π≦φ≦０．９９πの範囲にあることが好ましいことが分かる。   From the results shown in FIG. 3, in the case of dividing the incident light 11 into four light beams of 0th order diffracted light 12 and + 1st order diffracted light 13 having substantially the same intensity, the phase difference φ is 0.7π ≦ φ <1.0π. In addition, as will be described later, it is desirable to have a range of 0.8π ≦ φ <1.0 for applications in which the + 1st order diffracted light 13 is caused to interfere with each other to form a photonic crystal structure, as will be described later. In addition, it is understood that it is preferable that both be in the range of 0.7π ≦ φ <1.0, more preferably 0.81π ≦ φ ≦ 0.99π.

本発明の回折光学素子１からの３本の＋１次回折光１３を相互に干渉させるようにして、２次元的又は３次元的な露光量分布を得ることができる。すなわち、透明媒体に屈折率変調を与えることが可能であるとされているフェムト秒レーザ（特許文献３）と本発明の回折光学素子１を用いれば、透明な媒体（石英、プラスチック等）の内部に一挙に六方最密充填結晶格子状の２次元的又は３次元的フォトニック結晶構造を作製することが可能となる。   A two-dimensional or three-dimensional exposure amount distribution can be obtained by causing the three + 1st order diffracted beams 13 from the diffractive optical element 1 of the present invention to interfere with each other. That is, if a femtosecond laser (Patent Document 3) that is supposed to be capable of applying refractive index modulation to a transparent medium and the diffractive optical element 1 of the present invention are used, the inside of the transparent medium (quartz, plastic, etc.) It is possible to produce a hexagonal close-packed crystal lattice-like two-dimensional or three-dimensional photonic crystal structure at once.

以下に、まず、入射光１１としてフェムト秒レーザ光を用いることで、０次回折光１２と＋１次回折光１３を干渉させないで、＋１次回折光１３同士のみを干渉させることができることを説明する。図４に示すように、露光には例えばＴｉサファイア発振器で繰り返し周波数は１ｋＨｚでパルス幅は１５０ｆｓであって、波長は８００ｎｍ、パルス幅１５０ｆｓ間に進む光の距離（光学距離）４５μｍのフェムト秒レーザ光を入射光１１として回折光学素子１に垂直に入射させると、図４（ａ）に示すように、回折光学素子１から出た直後では回折光学素子１に垂直な方向（Ｚ方向）では０次回折光１２のパルスと３本の＋１次回折光１３のパルスの位置の差はないが、図４（ｂ）に示すように、回折光学素子１から１ｍｍ程度の位置で、すでにＺ方向に５００μｍの位置の差が出てしまい、お互いに干渉しない。したがって、＋１次回折光１３のパルス同士のみが干渉し、後記の実施例から明らかなように、図５に示したような六方最密充填結晶格子状の３次元フォトニック結晶構造が形成されることになる。各格子点は、＋１次回折光１３のパルス同士が干渉して導入された屈折率変調部分である。   Hereinafter, first, it will be described that by using femtosecond laser light as the incident light 11, only the + 1st order diffracted light 13 can be interfered with each other without causing the 0th order diffracted light 12 and the + 1st order diffracted light 13 to interfere with each other. As shown in FIG. 4, for exposure, for example, a Ti sapphire oscillator has a repetition frequency of 1 kHz, a pulse width of 150 fs, a wavelength of 800 nm, and a light distance (optical distance) of 45 μm that travels between pulse widths of 150 fs. When light enters the diffractive optical element 1 perpendicularly as incident light 11, as shown in FIG. 4A, immediately after exiting the diffractive optical element 1, it is 0 in the direction perpendicular to the diffractive optical element 1 (Z direction). Although there is no difference in the position of the pulse of the next-order diffracted light 12 and the pulses of the three + 1st-order diffracted lights 13, as shown in FIG. 4B, at a position of about 1 mm from the diffractive optical element 1, it is already 500 μm in the Z direction. Differences in position occur and do not interfere with each other. Therefore, only the pulses of the + 1st order diffracted light 13 interfere with each other, and a hexagonal close-packed crystal lattice-shaped three-dimensional photonic crystal structure as shown in FIG. become. Each grating point is a refractive index modulation portion introduced by interference of pulses of the + 1st order diffracted light 13.

このようなフォトニック結晶の用途としては、光導波路があげられる。３次元的な格子点の周期構造中に欠陥に相当するものを導入する必要があるが、このような周期構造さえできれば、後工程でそのような欠陥を導入することが可能である。３次元フォトニック結晶が実現すれば、光回路等、電気回路以上に高速で細密なＬＳＩも実現できる。   An example of the use of such a photonic crystal is an optical waveguide. Although it is necessary to introduce a defect corresponding to a defect in a three-dimensional periodic structure of lattice points, it is possible to introduce such a defect in a subsequent process as long as such a periodic structure is obtained. If a three-dimensional photonic crystal is realized, it is possible to realize an LSI that is faster and finer than an electric circuit, such as an optical circuit.

従来、３次元的なホログラフィック記録方法としては、特許文献４に示すものがあるが、分割して干渉させるビームは４本であり、本発明の３本とは異なり、かつ、作製されるものは六方最密な３次元的な構造ではない。また、３次元記録を実用化するには、フェムト秒パルスのパルス幅が短いため、４本のパルス光束を１点で干渉露光させるためには複雑な露光系が必要とされていたが、本発明では回折光学素子１だけを用いているので、系が単純化され、容易に３本の光束を干渉させることが可能となる。   Conventionally, as a three-dimensional holographic recording method, there is one shown in Patent Document 4, but there are four beams to be divided and interfered, which is different from the three of the present invention and is produced. Is not a hexagonal close-packed three-dimensional structure. In order to put 3D recording into practical use, since the pulse width of femtosecond pulses is short, a complex exposure system is required to perform interference exposure of four pulsed light beams at one point. Since only the diffractive optical element 1 is used in the invention, the system is simplified, and three light beams can be easily interfered with each other.

以上は、３本の光束の３次元干渉によるものであるが、２次元的な干渉を得ることも可能なことは明らかである。非特許文献１に記載のものと同様に、六角形アレイを作製して、反射防止構造体や２次元的フォトニック結晶を得ることができる。露光波長は、干渉部分を記録できる波長にすればよく、例えば紫外線感光レジストを使用する場合には、紫外線波長に対して位相差φの範囲を設定すればよい。   The above is due to the three-dimensional interference of the three light beams, but it is obvious that two-dimensional interference can be obtained. Similar to that described in Non-Patent Document 1, a hexagonal array can be produced to obtain an antireflection structure or a two-dimensional photonic crystal. The exposure wavelength may be set to a wavelength at which the interference portion can be recorded. For example, when an ultraviolet photosensitive resist is used, the range of the phase difference φ may be set with respect to the ultraviolet wavelength.

なお、本願出願人による特許文献１の場合に比較して、本発明の回折光学素子１を用いた場合、露光量強度分布が密になるため、フォトニック結晶構造、反射防止構造体を作製する際も、より優位な設計が可能となる。   Note that, when the diffractive optical element 1 of the present invention is used, the exposure intensity distribution is denser than in the case of Patent Document 1 by the present applicant, so that a photonic crystal structure and an antireflection structure are produced. Even more advantageous design is possible.

以下に、具体的な回折光学素子１の実施例を説明する。この実施例の回折光学素子１は、凸状の正三角形領域３、凹状の正三角形領域４の１辺が１．０７μｍの正三角形からなる三角格子について、ＲＣＷＡ手法による電磁場解析を行った。出射する光は、略０次回折光１２と＋１次回折光１３との４本であり、これによる干渉計算も行った。   Specific examples of the diffractive optical element 1 will be described below. In the diffractive optical element 1 of this example, an electromagnetic field analysis was performed by the RCWA method on a triangular lattice formed of a regular triangle having one side of a convex regular triangular region 3 and a concave regular triangular region 4 having a side of 1.07 μm. The emitted light is approximately four of the 0th-order diffracted light 12 and the + 1st-order diffracted light 13, and the interference calculation was also performed.

入射光１１の波長は０．８μｍのランダム偏光であり、回折光学素子１の背面（正三角形領域３、４が配置された面とは反対側の面）から垂直に入射させた。   The wavelength of the incident light 11 is 0.8 μm random polarization, and is incident perpendicularly from the back surface of the diffractive optical element 1 (surface opposite to the surface on which the equilateral triangular regions 3 and 4 are arranged).

回折光学素子１の屈折率は１．４６０、位相差φは０．９８７πである。   The refractive index of the diffractive optical element 1 is 1.460, and the phase difference φ is 0.987π.

図２のように、入射光１１がそのまま回折光学素子１を通過して０次回折光１２となる光が存在するが、上記の３方向に分岐する＋１次回折光１３は、この０次回折光１２とα＝５９．７°の等しい角度をなし、それぞれ同じ強度である。それらの強度は以下のようになった。   As shown in FIG. 2, there is light in which the incident light 11 passes through the diffractive optical element 1 as it is and becomes 0th order diffracted light 12, but the + 1st order diffracted light 13 branched in the above three directions is α = 59.7 ° and the same angle, respectively. Their strength was as follows.

０次回折光１２ ：４３．５％
＋１次回折光１３合計：４３．６％
この＋１次回折光１３の３本の光束の干渉で、図５のような３次元フォトニック結晶構造を作ることができた。図５のａ面、ｂ面、ｃ面、ｄ面（ａ面）の露光量強度分布を図６（ａ）から（ｄ）に示した。結像位置によって、強度分布が交互に現れ、六方最密充填格子ができていることが観察できる。なお、図６（ａ）はＺ＝９０．３５μｍの面、図６（ｂ）はＺ＝９０．６２μｍの面、図６（ｃ）はＺ＝９０．８９μｍの面、図６（ｄ）はＺ＝９１．１６μｍの面である。 Zero-order diffracted light 12: 43.5%
+ 1st order diffracted light 13 total: 43.6%
The three-dimensional photonic crystal structure as shown in FIG. FIGS. 6A to 6D show the exposure intensity distributions on the a-plane, b-plane, c-plane and d-plane (a-plane) in FIG. It can be observed that the intensity distribution appears alternately depending on the imaging position and a hexagonal close-packed lattice is formed. 6A is a surface with Z = 90.35 μm, FIG. 6B is a surface with Z = 90.62 μm, FIG. 6C is a surface with Z = 90.89 μm, and FIG. Z = 91.16 μm.

次に、比較例を説明する。この比較例の回折光学素子は上記実施例のような構成をしており、位相差φのみが異なり１．５０７πである。そのため、その回折光学素子の背面から垂直に入射させた波長０．８μｍのランダム偏光の入射光は、そのまま通過する０次回折光と、６方向に分岐する＋１次回折光、−１次回折光の７本に分岐する。   Next, a comparative example will be described. The diffractive optical element of this comparative example is configured as in the above-described embodiment, and only the phase difference φ is different and is 1.507π. For this reason, the incident light of 0.8 μm wavelength, which is incident perpendicularly from the back surface of the diffractive optical element, is zero-order diffracted light that passes as it is, seven + 1st-order diffracted light and −1st-order diffracted light that branch in six directions. Branch to

０次回折光 ：５７．１％
＋１次回折光合計 ：２１．２％
−１次回折光合計 ：２１．７％
±１次回折光６本が干渉することにより、図７（ａ）から（ｄ）に示した強度分布が得られる。図７（ａ）はＺ＝９０．３５μｍの面、図７（ｂ）はＺ＝９０．６２μｍの面、図７（ｃ）はＺ＝９０．８９μｍの面、図７（ｄ）はＺ＝９１．１６μｍの面である。図７から明らかなように、干渉位置によって干渉縞は周期的に現れず、六方最密充填格子作製用位相マスクとして機能しないことが分かる。 0th order diffracted light: 57.1%
+ 1st order diffracted light total: 21.2%
-1st order diffracted light total: 21.7%
When six ± first-order diffracted beams interfere, the intensity distributions shown in FIGS. 7A to 7D are obtained. FIG. 7A shows a surface with Z = 90.35 μm, FIG. 7B shows a surface with Z = 90.62 μm, FIG. 7C shows a surface with Z = 90.89 μm, and FIG. The surface is 91.16 μm. As is apparent from FIG. 7, it can be seen that interference fringes do not appear periodically depending on the interference position and do not function as a phase mask for producing a hexagonal close-packed grating.

以上、本発明の回折光学素子とそれを用いたフォトニック結晶作製方法をその原理と実施例に基づいて説明してきたが、本発明はこれら実施例に限定されず種々の変形が可能である。   The diffractive optical element of the present invention and the photonic crystal manufacturing method using the diffractive optical element have been described based on the principle and examples, but the present invention is not limited to these examples and can be variously modified.

本発明による回折光学素子の構成を示す斜視図である。It is a perspective view which shows the structure of the diffractive optical element by this invention. 本発明による回折光学素子と回折光の関係を示す斜視図と正面図である。It is the perspective view and front view which show the relationship between the diffractive optical element by this invention, and diffracted light. 図１の回折光学素子の±１次回折光と０次回折光の回折効率と位相差との関係を求めた結果を示す図である。FIG. 2 is a diagram illustrating a result of obtaining a relationship between diffraction efficiency and phase difference of ± first-order diffracted light and zero-order diffracted light of the diffractive optical element in FIG. 1. フェムト秒レーザ光を用いる場合に本発明による回折光学素子による＋１次回折光同士のみを干渉させることができることを説明するための図である。It is a figure for demonstrating that only + 1st-order diffracted light by the diffractive optical element by this invention can be made to interfere when using a femtosecond laser beam. 本発明の方法により形成可能な六方最密充填結晶格子状の３次元フォトニック結晶構造を示す斜視図である。It is a perspective view which shows the hexagonal close-packed crystal lattice-like three-dimensional photonic crystal structure which can be formed by the method of this invention. 本発明の１実施例の回折光学素子を用いて得られる図５のａ面、ｂ面、ｃ面、ｄ面に対応する位置での露光量強度分布を示す図である。It is a figure which shows exposure amount intensity distribution in the position corresponding to the a surface of FIG. 5, b surface, c surface, and d surface obtained using the diffractive optical element of one Example of this invention. 本発明の比較例の回折光学素子を用いて得られる図６と対応する位置での露光量強度分布を示す図である。It is a figure which shows exposure amount intensity distribution in the position corresponding to FIG. 6 obtained using the diffractive optical element of the comparative example of this invention.

符号の説明Explanation of symbols

１…回折光学素子
２…透明基板
３…凸状の正三角形領域
４…凹状の正三角形領域
１１…入射光
１２…０次回折光
１３…＋１次回折光
１４…−１次回折光 DESCRIPTION OF SYMBOLS 1 ... Diffractive optical element 2 ... Transparent substrate 3 ... Convex equilateral triangle area | region 4 ... Concave equilateral triangle area | region 11 ... Incident light 12 ... 0th order diffracted light 13 ... + 1st order diffracted light 14 ... -1st order diffracted light

Claims (4)

透明基板の面上に、正三角形の各辺方向に同じ高さで同じ大きさの凸状の正三角形領域が各辺の長さの周期で繰り返し配列され、前記凸状の正三角形領域の間に向きを上下逆転させた同じ低さで前記凸状の正三角形領域と同じ大きさの凹状の正三角形領域が正三角形の各辺方向に各辺の長さの周期で繰り返し配列され、前記凸状の正三角形領域と前記凹状の正三角形領域が相互に隣接して前記透明基板の表面を密に覆うように配置され、前記透明基板を透過する基準波長光に対して、前記凸状の正三角形領域とそれに隣接する前記凹状の正三角形領域の間に、前記透明基板に垂直に入射する基準波長光に対して位相差がπ未満であり、前記透明基板に垂直に入射する基準波長光を４方向へ分岐するために用いられる回折光学素子をマスクとして用い、前記回折光学素子にフェムト秒レーザ光を入射させ、前記回折光学素子から生じる＋１次回折光同士のみを透明媒体中で干渉させることにより２次元的又は３次元的な微細な周期構造に対応する露光量分布のアレイを発生させ、前記透明媒体中に屈折率変調として記録することを特徴とするフォトニック結晶作製方法。 On the surface of the transparent substrate, convex equilateral triangular regions having the same height and the same size in each side direction of the equilateral triangle are repeatedly arranged with a period of the length of each side, and between the convex equilateral triangular regions. A concave equilateral triangle region having the same height as the convex equilateral triangle region, the direction of which is reversed upside down, is repeatedly arranged in each side direction of the equilateral triangle with a period of each side length, A convex equilateral triangular region and the concave equilateral triangular region are arranged adjacent to each other so as to cover the surface of the transparent substrate closely, and the convex positive triangular region is transmitted with respect to the reference wavelength light transmitted through the transparent substrate. Between the triangular region and the concave equilateral triangular region adjacent thereto, the phase difference is less than π with respect to the reference wavelength light perpendicularly incident on the transparent substrate, and the reference wavelength light perpendicularly incident on the transparent substrate is 4 as a mask the diffractive optical element used to branch to the direction The femtosecond laser beam is incident on the diffractive optical element, and only the + 1st order diffracted lights generated from the diffractive optical element interfere with each other in the transparent medium, thereby corresponding to a two-dimensional or three-dimensional fine periodic structure. An array of exposure dose distribution is generated and recorded as refractive index modulation in the transparent medium. 前記回折光学素子の前記位相差が０．８１π〜０．９９πの範囲にあることを特徴とする請求項１記載のフォトニック結晶作製方法。 The photonic crystal manufacturing method according to claim 1 , wherein the phase difference of the diffractive optical element is in a range of 0.81π to 0.99π . 前記２次元的な微細な周期構造が、反射防止構造体若しくは２次元フォトニック結晶であることを特徴とする請求項１又は２記載のフォトニック結晶作製方法。 Photonic crystal manufacturing method according to claim 1 or 2, wherein said two-dimensional fine periodic structure is a anti-reflection structure or a two-dimensional photonic crystal. 前記３次元的な微細な周期構造が、六方最密充填結晶格子状の３次元フォトニック結晶であることを特徴とする請求項１又は２記載のフォトニック結晶作製方法。 The three-dimensional fine periodic structure, the photonic crystal manufacturing method according to claim 1 or 2, wherein it is a hexagonal close-packed lattice-like three-dimensional photonic crystal.
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JP2000329920A (en) * 1999-05-21 2000-11-30 Japan Science & Technology Corp Formation of photonic crystal structure by laser interference
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