JP3560152B2 - Manufacturing method of self-formed optical waveguide - Google Patents

Description

【００１２】
また、請求項４に記載の手段によれば、請求項１に記載の自己形成光導波路の製造方法において、低屈折率構造物が、長軸を回転軸とした回転楕円体面の一部を形成し、終点領域が、回転楕円体の回転軸を長軸とする楕円断面の一方の焦点を含み、他の焦点が、その位置からは少なくとも自己形成光導波路が直進するよう設計されていることを特徴とする。
【００１３】
また、請求項５に記載の手段によれば、請求項４に記載の自己形成光導波路の製造方法において、空間に座標軸を取り、終点領域が点（０，ｂ／２，０）を中心とするｙ軸に垂直な半径ａの円盤状とし、点（０，−ｂ／２，０）の位置からは少なくとも自己形成光導波路が直進するよう設計されているものとし、略一定径の硬化樹脂部の屈折率をｎ_１、低屈折率構造物の屈折率をｎ_ｍとしたときに、前記回転楕円体面が、ｙ軸を長軸とする次の楕円
【数７】

をｙ軸を回転軸として回転させたものであり、且つ低屈折率構造物の上記楕円上の点で次の式が成立することを特徴とする。
【数８】

【００１４】
また、請求項６に記載の手段によれば、光硬化性樹脂中に微小径の光束を照射し硬化させることで屈折率の上昇した硬化樹脂部を連続形成する際、微小径の光束が硬化樹脂部に閉じ込められることにより光束の通過方向に略一定径とした硬化樹脂部を有する自己形成光導波路の製造方法において、該自己形成光導波路が、予め設計された終点領域に到達するよう、予め設計された形成領域から外れた場合に微小径の光束が反射により屈折するよう例えば金属膜などによる反射構造物を予め設計された形成領域を囲んで配設することを特徴とする。
【００１５】
また、請求項７に記載の手段によれば、請求項６に記載の自己形成光導波路の製造方法において、終点領域が円状の領域であり、反射構造物が円状の領域を上面とする円錐台の側面の内壁を形成することを特徴とする。
【００１６】
また、請求項８に記載の手段によれば、請求項７に記載の自己形成光導波路の製造方法において、終点領域ａを半径ａの円状とし、該半径ａの円の中心から終点領域に垂直に距離ｂの位置からは少なくとも自己形成光導波路が直進するよう設計されているものとし、円錐台の高さをＬとしたときに、円錐台の側壁の傾斜角θ_ｍが次の式を充たすことを特徴とする。
【数９】

【００１７】
また、請求項９に記載の手段によれば、請求項６に記載の自己形成光導波路の製造方法において、反射構造物が、長軸を回転軸とした回転楕円体面の一部を形成し、終点領域が、回転楕円体の回転軸を長軸とする楕円断面の一方の焦点を含み、他の焦点が、その位置からは少なくとも自己形成光導波路が直進するよう設計されていることを特徴とする。
【００１８】
また、請求項１０に記載の手段によれば、請求項９に記載の自己形成光導波路の製造方法において、空間に座標軸を取り、終点領域が点（０，ｂ／２，０）を中心とするｙ軸に垂直な半径ａの円盤状とし、点（０，−ｂ／２，０）の位置からは少なくとも前記自己形成光導波路が直進するよう設計されているものとし、前記回転楕円体面が、ｙ軸を長軸とする次の楕円
【数１０】

をｙ軸を回転軸として回転させたものであることを特徴とする。
【００１９】
【作用及び発明の効果】
本発明者らの特開平２０００−３４７０４３号公報記載の技術は、自己形成導波路が光の進行方向に沿って自動的に成長していくものである。このとき、光の進行方向が予め設計された終点領域に向かっていなくても、光の反射を利用してその進行方向を終点領域に向かうよう修正する構造物を、予め設計された自己形成導波路の形成領域を囲んで配設することで、進行方向を該終点領域に変更させることができる。このとき、構造物が光導波路の屈折率より低いか、又はいかなる角度からも反射するよう鏡面を形成すれば目的が達成される（請求項１、請求項６）。そのような構造物は、終点領域を上面とする円錐台状にすると容易である（請求項２、請求項７）。
【００２０】
また、その位置からは少なくとも自己形成導波路が直進するよう設計された点、即ちその位置からは設計上、反射、収束又は分散することのない点と、終点領域の中心とを２焦点とする楕円を、長軸を軸として回転させた回転楕円体面を用いれば、前者の点（第１の焦点）から進む光は回転楕円体面で反射し後者の点（第２の焦点）に向かうので、理想的な構造物とすることができる（請求項４、請求項９）。
【００２１】
以下、実施例の欄にて、請求項３、請求項５、請求項８及び請求項１０の条件を有する構造体の作用効果を示す。
【００２２】
【発明の実施の形態】
図１の（ａ）は本願を適用した光モジュールの構成を示す断面図である。尚、斜線を施していない部分も空隙ではない。Ｓで示した部分が本願発明に係る構造体であり、拡大図を図１の（ｂ）に示す。屈折率ｎ_ｍの透明容器３に構造体Ｓを設け、ハーフミラー６１、６２、反射ミラー６３を設けて特開平２０００−３４７０４３号公報記載のように光ファイバ１から光照射で混合樹脂溶液から光伝送路２１１を形成し、分岐２１１ａ、２１１ｂ、及び２１１ｃを形成する。この際、分岐２１１ａ、２１１ｂ、及び２１１ｃが所望の光電変換素子５ａ、５ｂ、５ｃに到達するよう、各々計３箇所に構造体Ｓを設けておく。
【００２３】
図２の（ａ）のように、予め設計された方角（２本の点線の領域）からずれて光導波路ＷＧ（硬化樹脂部）が成長しても、図２の（ｂ）のように、構造体部分で反射されれば、その後の光導波路ＷＧ（硬化樹脂部）が成長する方向は図２の（ｃ）の通り、予め設計された方角側（２本の点線の領域）に修正されることとなる。構造体部分で反射されるためには、例えば金属膜を形成してミラーとする他、構造体の構成材料の屈折率ｎ_ｍを光導波路ＷＧの屈折率ｎ_１より小さくし、且つ入射角度が全反射条件を充たすよう壁面の傾斜を構成すれば良い。
【００２４】
〔第１の構造体例（請求項３）〕
構造体の構成材料の屈折率ｎ_ｍを光導波路ＷＧの屈折率ｎ_１より小さくし、且つ入射角度が全反射条件を充たすよう壁面の傾斜を構成する場合として、終点領域が半径ａの円状で、その中心Ｏ’から円に垂直に距離ｂの点Ｏから光が入射するよう設計されており、構造体が終点領域を上面とする円錐台の側面を壁面とする場合を考える（図３）。円錐台の高さをＬ_ｍ、設計された入射光方向と壁面の成す角をθ_ｍとする。
【００２５】
今、円錐台底面の周上の点Ｐに、点Ｏから光が入射することを考える。ＯＯ’とＯＰとの成す角をθ_１とすると、円錐台壁面とＯＰの成す角はθ_１＋θ_ｍである。点Ｐの線分ＯＯ’との距離を２通りに表してこれらを等しいとおくと、次のとおりである。
【数１１】

【００２６】
一方、ＯＰを通る光が屈折率ｎ_１の光導波路を通った場合、屈折率ｎ_ｍの構造体の点Ｐで全反射するための条件は、次のとおりである。
【数１２】

【００２７】
これらから次の式が成立する。
【数１３】

【００２８】
これを解くと、次の不等式となる。
【数１４】

【００２９】
側壁の傾斜角θ_ｍは、次の式を充たすことで、全反射条件を充たす。
【数１５】

【００３０】
円錐台底面の周上の点Ｐ以外の円錐台側壁の点に点Ｏから入射した場合、その入射角が点Ｐにおける入射角より小さいことは明らかである。よって、上記数１５が成立することで、円錐台側壁の任意の点において、全反射条件を満たす（請求項３）。
【００３１】
図４に、数１５の左辺（θ_ｍの最大値）を、屈折率比ｎ_ｍ／ｎ_１とともにシミュレーションした図を示す。尚、ａ＝０．１５ｍｍ、Ｌ_ｍ＝１ｍｍ、ｂ＝４ｍｍとした。このシミュレーションでは屈折率比ｎ_ｍ／ｎ_１が０．９６で、円錐台側壁の傾斜角は１０度以下とする必要がある。また、図５に、ａ＝０．１５ｍｍ、ｂ＝４ｍｍとし、屈折率比ｎ_ｍ／ｎ_１を０．９３、０．９５、０．９７と変化させて、Ｌ_ｍと数１５の左辺（θ_ｍの最大値）との関係を示す。
【００３２】
〔第２の構造体例（請求項８）〕
第１の構造体で、円錐台の側壁に金属で反射膜を形成した場合は、次のような条件を設けることができる。即ち、１回だけ反射することで半径ａの終点領域に達するよう条件設定する。
【００３３】
やはり図３において、点Ｏから入射した光が円錐台の底面の円周上の点Ｐに到達し、反射して終点領域の外周上の点Ｑに到達したとする。円錐台底面の周上の点Ｐ以外の円錐台側壁の点に点Ｏから入射した場合、反射角は小さくなるので、２度目の反射を起こすことなく終点領域内に到達することは容易に理解できる。
【００３４】
このような条件を充たすためには、次の関係が成立すれば良い。
【数１６】

【００３５】
数１１を用いてこれを展開すると、次のとおりとなる。
【数１７】

【００３６】
数１７は１実解を有する。これが正ならば（３Ｌ＞２ｂならば実解は負）、その解がθ_ｍの最大値である。実際θ_ｍの最大値は次のように求められるので、ａ＝０．１５ｍｍ、ｂ＝４ｍｍとし、Ｌ_ｍと数１７の解（θ_ｍの最大値）との関係を図６示す（請求項８）。
【数１８】

【００３７】
〔第３の構造体例（請求項１０）〕
点Ｏ（光の発射点）と点Ｏ’（終点領域の中心）を焦点とする楕円を、長軸を中心として回転させた回転楕円体面を有する構造体で、壁面に金属膜を有するものは、点Ｏからの光を悉く点Ｏ’に向け反射する（図７参照）。２つの焦点点Ｏ（光の発射点）と点Ｏ’（終点領域の中心）を直交座標（０，−ｂ／２，０）と（０，ｂ／２，０）とし、点（ａ，ｂ／２，０）を通る楕円（図７参照）は次の式で示される。
【数１９】

【００３８】
数１９を充たす楕円をｙ軸で回転させた回転楕円面は、一方の焦点（０，−ｂ／２，０）から回転楕円面に入射する光を反射して他方の焦点（０，ｂ／２，０）（終点領域の中心）に導く（請求項１０）。
【００３９】
〔第４の構造体例（請求項５）〕
第３の構造体の回転楕円体面を有し、第１の構造体のように金属膜を有しない屈折率による全反射条件を求める。数１９の楕円上の座標Ｘ（ｘ，ｙ，０）における接線の角度（ｘ軸の正方向基準、反時計回り）は次のとおりである（図７参照）。
【数２０】

【００４０】
また、ベクトルＯＸのｘ軸の正方向と成す角度は次のとおりである。
【数２１】

【００４１】
これらから、接線とベクトルＯＸの成す角（反時計回り）が、スネルの法則を充たすようにするためには次のとおりである（請求項５）。
【数２２】

【００４２】
以上の実施例では、簡単のため一点からの光路を以て本願発明の構造体を説明したが、本願の自己形成光導波路は一定の径を有しているので、それに応じ、設計すれば良い。即ち、一定の領域からの光束に対し、終点領域に達するよう構造体を設計することは何ら困難なことではない。光の照射点Ｏは、光ファイバ先端面或いはミラーの設計点等、そこから自己形成光導波路が障害無しに光電変換素子等を配置した終点領域に達する着目点とすればよい。
【００４３】
また、上記実施例では円錐台と回転楕円体面を以て本願実施例を説明したが、本願の構造体は任意の多面体状壁面又は任意の曲面から成る壁面にて構成できる。その際、図７からも明らかなように、終点領域から着目点に向かって構造体が広がるのみでなく、狭まる部分を有する曲面また多面体面でも良く、場合によっては全体又は一部が逆円錐台形状でも本願発明を実施できる。また、反射回数は１回に限られず、複数回でも良い。
【図面の簡単な説明】
【図１】（ａ）は、本願を適用した光伝送路の構造を示す断面図、（ｂ）は構造体Ｓの拡大図。
【図２】本願を適用した自己形成光導波路の成長の様子を示す段階図。
【図３】円錐台の側面を壁面とする第１又は第２構造体の設計図。
【図４】第１の構造体例におけるシミュレーションのグラフ図。
【図５】第１の構造体例における別のシミュレーションのグラフ図。
【図６】第２の構造体例におけるシミュレーションのグラフ図。
【図７】回転楕円体面を壁面とする第３又は第４構造体の設計図。
【図８】従来の特開平２０００−３４７０４３記載の光伝送路の製造方法を示す工程図。
【図９】従来の自己形成導波路が軸ずれを起こした様子を示す断面図。
【符号の説明】
１ 光ファイバ
２１１ 光導波路
２１１ａ〜ｃ 光導波路の分岐
２３ 光導波路より屈折率の低いクラッド部分
３ 透明容器
５ａ〜ｃ 光電変換素子
６１、６２ ハーフミラー
６３ 反射ミラー
ＷＧ 自己形成光導波路
ａ 円状の終点領域の半径
ｂ 着目点から終点領域中心までの距離
Ｓ 構造体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a self-formed optical waveguide applicable to an inexpensive and low-loss optical interconnection, an optical demultiplexer or a multiplexer in optical communication.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in optical fiber communication, an optical interconnection technology that performs hybrid integration using an optical waveguide device to efficiently couple an optical fiber and a photoelectric conversion element (semiconductor laser, light emitting diode, photodiode, avalanche photodiode) has been developed. Attention has been paid. For example, there is a hybrid waveguide module described in JP-A-2000-275457. This is a method in which a member provided with an optical waveguide circuit for optically coupling an optical fiber and a photoelectric conversion element, a plurality of photoelectric conversion elements, and an optical fiber are hybridly integrated on a base with high precision. .
[0003]
On the other hand, the present inventors have developed a self-formed optical waveguide described in Japanese Patent Application Laid-Open No. 2000-347043. By irradiating the photocurable resin with a light beam having a small diameter, a cured resin portion having a high refractive index is sequentially formed and can be used as it is as an optical waveguide.
[0004]
FIG. 8 schematically shows a method of manufacturing the optical waveguide described in the above publication. An optical fiber 91, a liquid mixture (photocurable liquid resin composition) 92 of photocurable resins 921 and 922 photopolymerized by two different polymerization types, and a transparent container 93 are prepared, and as shown in FIG. , Resin A 921 and Resin B 922 are mixed to prepare a mixed solution 92, which is filled in a transparent container 93. Next, the tip surface 912 of the optical fiber 91 is immersed in the mixed solution 92, and light of a certain wavelength is supplied to the optical fiber 91. Then, as shown in FIG. 8B, a substantially frustoconical hardened resin 9211 is formed from the distal end face 912 of the optical fiber 91, and thereafter, the hardened portion 9211 grows into a substantially cylindrical shape having a constant diameter. ((C) of FIG. 8). When the hardened portion 9211 has a desired length, the supply of the light of the wavelength is stopped, and light of a lower wavelength (94 in the figure) is irradiated from the entire circumference of the transparent container 93 to mix the remaining light in the transparent container 93. The liquid 92 is entirely cured (FIG. 8D).
[0005]
The refractive index of the cured portion 9211 is equal to the refractive index of the resin A after curing, and the refractive index of the cured portion 923 is located between the refractive indices of the resin A and the resin B after curing. In the mixed solution 92, only the resin A is cured to form a long core having a substantially columnar portion having a high refractive index, and both the resin A and the resin B are cured to form a clad having a low refractive index. A wave path can be formed.
[0006]
[Problems to be solved by the invention]
However, in the hybrid waveguide module described in Japanese Patent Application Laid-Open No. 2000-275457, alignment in sub-micron units is required, the degree of freedom of axis alignment is high, and the difficulty is extremely high. In particular, when the number of components is large, if the shapes of the components are fixed in advance, the misalignment is added up. In addition, if there is a component having a shape error, the entire module is affected and the yield is reduced. In addition, the alignment must be performed for each module one by one, and the assembly cost is very large.
[0007]
Further, in the device described in Japanese Patent Application Laid-Open No. 2000-347043 by the present inventors, although the optical waveguide is self-formed, the precision of the disposed optical component determines the position of the self-formed optical waveguide, and If the precision of the provided optical component is low, the optical waveguide is not formed at a desired position, and for example, the optical waveguide may not reach the arranged photoelectric conversion element. That is, as shown in FIG. 9A, when the tip of the optical fiber 91 is slightly shifted in angle, the optical waveguide 9211 does not reach the photoelectric conversion element 95 (the desired end point area). Further, as shown in FIG. 9B, even if the half mirrors 961 and 962 and the reflection mirror 963 are arranged to provide a branch point and a bending point, the alignment of these mirrors 961, 962 and 963 is accurate. Otherwise, the optical waveguides 9211a, 9211b, and 9211c do not reach the photoelectric conversion elements 95a, 95b, and 95c (desired end point areas).
[0008]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to manufacture a self-formed optical waveguide, and to obtain a desired end point region even when the direction in which the optical waveguide is formed is deviated from a desired direction. Is to form an optical waveguide.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, according to the means of claim 1, when continuously forming a cured resin portion having an increased refractive index by irradiating and curing a light beam having a small diameter in a photocurable resin, In a method for manufacturing a self-formed optical waveguide having a cured resin portion having a substantially constant diameter in a light beam passing direction by confining a light beam having a small diameter into the cured resin portion, the self-formed optical waveguide may have a pre-designed end region. The low-refractive-index structure is disposed so as to surround the pre-designed formation region so that a light beam having a small diameter is refracted by total internal reflection when the light beam deviates from the pre-designed formation region so as to reach. .
[0010]
According to a second aspect of the present invention, in the method of manufacturing a self-formed optical waveguide according to the first aspect, the end point region is a circular region, and the low refractive index structure is formed on the circular region on the upper surface. The inner wall of the side surface of the truncated cone is formed.
[0011]
According to a third aspect of the present invention, in the method of manufacturing a self-formed optical waveguide according to the second aspect, the end point region is formed in a circular shape having a radius a, and the center of the circle having the radius a is perpendicular to the end point region. It is assumed that at least the self-formed optical waveguide is designed to travel straight from the position of the distance b, the height of the truncated cone is L, the refractive index of the cured resin portion having a substantially constant diameter is n ₁ , the low refractive index structure portion the refractive index of when the n _m, the inclination angle theta _m frustoconical side walls, characterized in that satisfy the following equation.
(Equation 6)

[0012]
According to a fourth aspect of the present invention, in the method for manufacturing a self-formed optical waveguide according to the first aspect, the low refractive index structure forms a part of a spheroidal surface having a major axis as a rotation axis. Then, the end point region includes one focal point of the elliptical cross section whose major axis is the rotation axis of the spheroid, and the other focal point is designed so that at least the self-formed optical waveguide goes straight from that position. Features.
[0013]
According to a fifth aspect of the present invention, in the method of manufacturing a self-formed optical waveguide according to the fourth aspect, a coordinate axis is set in a space, and the end point region is centered on the point (0, b / 2, 0). And is designed so that at least the self-formed optical waveguide goes straight from the position of the point (0, -b / 2, 0), and is a cured resin having a substantially constant diameter. Assuming that the refractive index of the portion is n ₁ and the refractive index of the low refractive index structure is _nm , the spheroidal surface has the following ellipse with the y axis as the major axis.

Is rotated about the y axis as a rotation axis, and the following equation is satisfied at the point on the ellipse of the low refractive index structure.
(Equation 8)

[0014]
According to the means of claim 6, when the cured resin portion having the increased refractive index is continuously formed by irradiating the photocurable resin with the light beam having a small diameter and curing the light beam, the light beam having the small diameter is cured. In a method for manufacturing a self-formed optical waveguide having a cured resin portion having a substantially constant diameter in a light beam passing direction by being confined in a resin portion, the self-formed optical waveguide is preliminarily arriving at an end point region designed in advance. A reflective structure such as a metal film is provided so as to surround a previously designed formation region so that a light beam having a small diameter is refracted by reflection when deviating from the designed formation region.
[0015]
According to a seventh aspect of the present invention, in the method for manufacturing a self-formed optical waveguide according to the sixth aspect, the end point region is a circular region, and the reflective structure has a circular region as an upper surface. It is characterized in that an inner wall on the side surface of the truncated cone is formed.
[0016]
According to the means described in claim 8, in the method of manufacturing a self-formed optical waveguide according to claim 7, the end point region a is formed into a circle having a radius a, and the end point region is shifted from the center of the circle having the radius a to the end point region. At least from the position of the distance b, it is assumed that the self-formed optical waveguide is designed to go straight. When the height of the truncated cone is L, the inclination angle θ _m of the side wall of the truncated cone is expressed by the following equation. It is characterized by being satisfied.
(Equation 9)

[0017]
According to a ninth aspect of the present invention, in the method of manufacturing a self-formed optical waveguide according to the sixth aspect, the reflecting structure forms a part of a spheroidal surface having a major axis as a rotation axis, The end point region includes one focal point of the elliptical cross section having the major axis as the rotation axis of the spheroid, and the other focal point is designed so that at least the self-formed optical waveguide goes straight from that position. I do.
[0018]
According to a tenth aspect of the present invention, in the method for manufacturing a self-formed optical waveguide according to the ninth aspect, a coordinate axis is set in the space, and the end point region is centered on the point (0, b / 2, 0). It is assumed that at least the self-formed optical waveguide is designed to go straight from the position of the point (0, -b / 2, 0), and the spheroidal surface is , The next ellipse with the y axis as the major axis

Are rotated around the y axis as a rotation axis.
[0019]
[Action and effect of the invention]
The technique described in Japanese Patent Application Laid-Open No. 2000-347043 of the present inventors is such that a self-formed waveguide grows automatically along the traveling direction of light. At this time, even if the traveling direction of the light is not toward the pre-designed end point region, a structure that corrects the traveling direction using the reflection of light so as to be directed to the end point region can be used as a pre-designed self-forming guide. By arranging it around the formation area of the wave path, the traveling direction can be changed to the end point area. At this time, the object is achieved by forming a mirror surface such that the structure is lower than the refractive index of the optical waveguide or reflects the light from any angle (claims 1 and 6). Such a structure can be easily formed in a truncated cone shape with the end point region as the upper surface (claims 2 and 7).
[0020]
Also, at least a point designed so that the self-formed waveguide goes straight from that position, that is, a point that does not reflect, converge or disperse from the position, and a center of the end point region are set as two focal points. If a spheroid obtained by rotating the ellipse about the major axis is used, light traveling from the former point (first focus) is reflected by the spheroid and travels to the latter point (second focus). An ideal structure can be obtained (claims 4 and 9).
[0021]
The effects of the structures having the conditions of claims 3, 5, 8, and 10 will be described below in the section of Examples.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1A is a cross-sectional view illustrating a configuration of an optical module to which the present invention is applied. In addition, the part without hatching is not a void. The portion indicated by S is the structure according to the present invention, and an enlarged view is shown in FIG. The structure S is provided in the transparent container 3 having a refractive index _{n m,} the light from the mixed resin solution in the light emitted from the optical fiber 1 as the half mirror 61 and 62, JP-A 2000-347043 JP by the reflecting mirror 63 is provided A transmission path 211 is formed, and branches 211a, 211b, and 211c are formed. At this time, the structures S are provided at a total of three places so that the branches 211a, 211b, and 211c reach the desired photoelectric conversion elements 5a, 5b, and 5c.
[0023]
Even if the optical waveguide WG (cured resin portion) grows as shown in FIG. 2A from a direction designed in advance (the area indicated by the two dotted lines), as shown in FIG. If the light is reflected by the structure portion, the direction in which the optical waveguide WG (cured resin portion) grows is corrected to a previously designed direction side (a region indicated by two dotted lines) as shown in FIG. The Rukoto. To be reflected in the structure portion, for example, addition to the mirror by forming a metal film, the refractive index n _m of the material of the structure is smaller than the refractive index n ₁ of the optical waveguide WG, is and incident angle What is necessary is just to configure the inclination of the wall surface so as to satisfy the condition of total reflection.
[0024]
[Example of First Structure (Claim 3)]
The refractive index n _m of the material of the structure is smaller than the refractive index n ₁ of the optical waveguide WG, and as if the incident angle constitutes a tilt of the wall surface so as to satisfy the total reflection condition, the end point area like a circle of radius a Then, a case is considered in which light is designed to be incident from a point O at a distance b perpendicular to the circle from the center O ′ and the side surface of the truncated cone having the end point region as an upper surface is a wall surface (FIG. 3). ). Of the truncated cone height L _m, the angle formed by the designed incident light direction and the wall surface and theta _m.
[0025]
Now, consider that light is incident from a point O to a point P on the circumference of the bottom surface of the truncated cone. OO 'and the the angle between OP and theta _1, the angle formed by the frustoconical wall and the OP is θ _{1 +} θ _m. If the distance between the point P and the line segment OO ′ is expressed in two ways and they are equal, the following is obtained.
(Equation 11)

[0026]
On the other hand, when the light passing through the OP has passed through the optical waveguide refractive index n _1, the conditions for total reflection at the point P of the structure of the refractive index n _m are as follows.
(Equation 12)

[0027]
From these, the following equation holds.
(Equation 13)

[0028]
Solving this gives the following inequality:
[Equation 14]

[0029]
The inclination angle θ _{m of the} side wall satisfies the condition of total reflection by satisfying the following expression.
(Equation 15)

[0030]
Obviously, when the light enters from the point O to a point on the side of the truncated cone other than the point P on the circumference of the bottom of the truncated cone, the incident angle is smaller than the incident angle at the point P. Therefore, when the above equation 15 is satisfied, the total reflection condition is satisfied at an arbitrary point on the side wall of the truncated cone.
[0031]
4, the number 15 left-hand side of (the maximum value of theta _m), shows a diagram of a simulation with a refractive index ratio _n m / _{n 1.} In addition, a = 0.15 mm, L _m = 1 mm, and b = 4 mm. The refractive index ratio n _{m /} n ₁ In this simulation 0.96, the inclination angle of the frustoconical sidewall is required to be 10 degrees or less. Further, in FIG. 5, a = 0.15 mm, and b = 4 mm, and a refractive index ratio _n m / _{n 1} is changed from 0.93,0.95,0.97, _{L m} the number 15 the left-hand side of ( ₍ the maximum value of θm).
[0032]
[Example of second structure (Claim 8)]
In the first structure, when the reflection film is formed of metal on the side wall of the truncated cone, the following conditions can be provided. That is, the condition is set so that the light is reflected only once to reach the end point area of the radius a.
[0033]
3, it is assumed that the light incident from the point O reaches the point P on the circumference of the bottom surface of the truncated cone, is reflected, and reaches the point Q on the outer circumference of the end point region. It is easy to understand that when a point O is incident on a point on the frustoconical side wall other than the point P on the circumference of the frustum of the truncated cone from the point O, the reflection angle becomes small, and the light reaches the end point region without causing the second reflection. it can.
[0034]
In order to satisfy such a condition, the following relationship may be satisfied.
(Equation 16)

[0035]
When this is expanded using Equation 11, the following is obtained.
[Equation 17]

[0036]
Equation 17 has one real solution. If this is positive (3L> 2b if real solutions are negative), the maximum value of the solution is theta _m. Actually, since the maximum value of θ _m is obtained as follows, a = 0.15 mm and b = 4 mm, and the relationship between L _m and the solution of Equation 17 (the maximum value of θ _m ) is shown in FIG. 8).
(Equation 18)

[0037]
[Example of Third Structure (Claim 10)]
A structure having a spheroidal surface obtained by rotating an ellipse having a focus on a point O (a light emitting point) and a point O ′ (the center of an end point region) about a long axis, and having a metal film on a wall surface is , And all the light from point O is reflected toward point O ′ (see FIG. 7). The two focal points O (light emission points) and O ′ (center of the end point area) are defined as rectangular coordinates (0, −b / 2, 0) and (0, b / 2, 0), and the points (a, The ellipse passing through (b / 2,0) (see FIG. 7) is represented by the following equation.
[Equation 19]

[0038]
The spheroid obtained by rotating the ellipse satisfying Expression 19 on the y-axis reflects light incident on the spheroid from one focal point (0, -b / 2, 0) and reflects the light incident on the other focal point (0, b / 2,0) (the center of the end point area) (claim 10).
[0039]
[Example of fourth structure (Claim 5)]
The total reflection condition based on the refractive index having the spheroidal surface of the third structure and not having the metal film as in the first structure is obtained. The angles of the tangents at the coordinates X (x, y, 0) on the ellipse of Expression 19 (positive reference of the x-axis, counterclockwise) are as follows (see FIG. 7).
(Equation 20)

[0040]
The angle formed by the vector OX and the positive direction of the x-axis is as follows.
(Equation 21)

[0041]
From these, the angle (counterclockwise) formed by the tangent and the vector OX is as follows in order to satisfy Snell's law (claim 5).
(Equation 22)

[0042]
In the above embodiments, the structure of the present invention has been described by using an optical path from one point for simplicity. However, the self-formed optical waveguide of the present invention has a constant diameter, so that it may be designed accordingly. That is, it is not difficult at all to design the structure to reach the end point region for the light beam from a certain region. The light irradiation point O may be a point of interest such as a design point of an optical fiber tip surface or a mirror, from which the self-formed optical waveguide reaches an end point region where the photoelectric conversion element and the like are arranged without obstacles.
[0043]
Further, in the above embodiment, the embodiment of the present application has been described using the truncated cone and the spheroidal surface. However, the structure of the present invention can be constituted by an arbitrary polyhedral wall surface or an arbitrary curved wall surface. At this time, as is clear from FIG. 7, the structure may not only expand from the end point region to the point of interest, but may be a curved surface or a polyhedral surface having a narrowing portion. The present invention can be practiced with a shape. Further, the number of reflections is not limited to one, and may be plural.
[Brief description of the drawings]
1A is a cross-sectional view showing a structure of an optical transmission line to which the present invention is applied, and FIG. 1B is an enlarged view of a structure S.
FIG. 2 is a stage diagram showing a state of growth of a self-formed optical waveguide to which the present invention is applied.
FIG. 3 is a design diagram of a first or second structure having a side surface of a truncated cone as a wall surface.
FIG. 4 is a graph of a simulation in the first structural example.
FIG. 5 is a graph of another simulation in the first structure example.
FIG. 6 is a graph of a simulation in the second structural example.
FIG. 7 is a design diagram of a third or fourth structure having a spheroidal surface as a wall surface.
FIG. 8 is a process chart showing a conventional method for manufacturing an optical transmission line described in JP-A-2000-347043.
FIG. 9 is a cross-sectional view showing a state in which a conventional self-formed waveguide has undergone axial misalignment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical fiber 211 Optical waveguide 211a-c Branch 23 of optical waveguide 23 Cladding part 3 with lower refractive index than optical waveguide 3 Transparent container 5a-c Photoelectric conversion element 61, 62 Half mirror 63 Reflection mirror WG Self-forming optical waveguide a Circular end point Area radius b Distance S from the point of interest to the center of the end point area S Structure

Claims (10)

When a cured resin portion having an increased refractive index is continuously formed by irradiating a light beam having a small diameter into the photocurable resin and curing the light beam, the light beam having the small diameter is confined in the cured resin portion so that the light beam passes therethrough. In the method for producing a self-formed optical waveguide having the cured resin portion having a substantially constant diameter in the direction,
The low-refractive-index structure is designed such that the light beam having a small diameter is refracted by total reflection when the self-formed optical waveguide reaches a predesigned end region and deviates from the predesigned formation region. A method for manufacturing a self-formed optical waveguide, wherein the method is provided so as to surround a formed formation region. The self-forming light guide according to claim 1, wherein the end point region is a circular region, and the low refractive index structure forms an inner wall of a side surface of a truncated cone having the circular region as an upper surface. Waveguide manufacturing method. The end point region has a circular shape with a radius a, and at least the self-formed optical waveguide is designed to go straight from a position of a distance b perpendicularly to the end point region from the center of the circle with the radius a, and the truncated cone. Is the height of L _m , the refractive index of the cured resin part having a substantially constant diameter is n ₁ , and the refractive index of the low refractive index structure part is _nm , the inclination angle θ _m of the side wall of the truncated cone is as follows: The method according to claim 2, wherein the following formula is satisfied.

The low-refractive-index structure forms a part of a spheroid surface having a major axis as a rotation axis, and the end point region includes one focal point of an ellipse cross section having a spheroid rotation axis as a major axis. 2. The method of manufacturing a self-formed optical waveguide according to claim 1, wherein the other focus is designed so that at least the self-formed optical waveguide goes straight from that position. A coordinate axis is set in the space, and the end point region is a disk shape having a radius a perpendicular to the y axis centered on the point (0, b / 2, 0), and from the position of the point (0, -b / 2, 0). It is assumed that at least the self-formed optical waveguide is designed to go straight, and when the refractive index of the cured resin portion having a substantially constant diameter is n ₁ and the refractive index of the low refractive index structure is _nm , the rotation is Ellipsoidal surface is the next ellipse whose major axis is the y-axis

5. The self-forming optical waveguide according to claim 4, wherein the following equation is satisfied at the point on the ellipse of the low-refractive-index structure. Method.

When a cured resin portion having an increased refractive index is continuously formed by irradiating a light beam having a small diameter into the photocurable resin and curing the light beam, the light beam having the small diameter is confined in the cured resin portion so that the light beam passes therethrough. In the method for producing a self-formed optical waveguide having the cured resin portion having a substantially constant diameter in the direction,
The self-forming optical waveguide reaches the pre-designed end point region, and the reflecting structure is formed by changing the pre-designed forming region so that the light beam of the small diameter is refracted when the light beam deviates from the pre-designed forming region. A method for manufacturing a self-formed optical waveguide, wherein the method is to surround and arrange. 7. The self-forming optical waveguide according to claim 6, wherein the end point region is a circular region, and the reflection structure forms an inner wall of a side surface of a truncated cone having the circular region as an upper surface. Production method. The end point area a is formed in a circular shape having a radius a, and at least the self-formed optical waveguide is designed to travel straight from a position at a distance b perpendicular to the end point area from the center of the circle having the radius a. pedestal height is taken as L _m, a manufacturing method of the self-forming optical waveguide according to claim 7 in which the inclination angle theta _m of the frustoconical side walls is characterized in that satisfy the following equation.

The reflective structure forms a part of a spheroidal surface having a major axis as a rotation axis, and the end point region includes one focal point of an elliptical cross section having the spheroid as a major axis. 7. The method for manufacturing a self-formed optical waveguide according to claim 6, wherein a focal point of the self-formed optical waveguide is designed so that at least the self-formed optical waveguide goes straight from that position. A coordinate axis is set in the space, and the end point region is a disk shape having a radius a perpendicular to the y axis centered on the point (0, b / 2, 0), and from the position of the point (0, -b / 2, 0). Is designed so that at least the self-formed optical waveguide goes straight, and the spheroidal surface is the next ellipse whose major axis is the y axis.

10. The method for manufacturing a self-formed optical waveguide according to claim 9, wherein is rotated about the y axis as a rotation axis.

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