JP2009175475A - Method of manufacturing optical coupler and optical coupler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical coupler which can form a core and a clad of a predetermined shape around the core and is high in mass productivity, and to provide the optical coupler. <P>SOLUTION: The method of manufacturing the optical coupler includes a core manufacturing step and a clad manufacturing step. Also, as a forming means to form a core 111a, a clad 112a, and a damming part 141a, there are used a first exposure mask 142 and a second exposure mask 143, irradiating with light a core material 114 and a clad material 115 which are a photosetting resin. The core 111a and the damming part 141a are simultaneously formed using the same core material 114, reducing the manufacturing steps and providing a manufacturing method capable of forming an optical waveguide 110a in a prescribed shape with high mass-productivity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical coupler for optically coupling an optical transmission line and an optical element provided on an optical circuit board, and a method for manufacturing the same.

  In recent years, in the field of integrated devices made of semiconductors, progress toward high speed and high density has been remarkable, and interconnections using conventional electrical wiring cannot expect sufficient characteristics due to signal delay, attenuation, interference, etc. Is a problem. This problem is said to be an IO bottleneck, and optical interconnection technology has attracted attention in order to solve this problem. The optical interconnection technology is considered to be applied not only between communication devices and between boards in a communication device, but also between integrated circuit elements in one board.

  As a conventional optical circuit board for realizing intra-board optical interconnection, for example, a multilayer printed board on which an optical waveguide disclosed in Patent Document 1 is formed is known. The optical circuit board disclosed in Patent Document 1 is an optical path conversion mirror formed on an optical wiring for signal light emitted in a direction perpendicular to the board from a surface-emitting optical element (VCSEL) mounted on the surface of the board. The reflected light is guided through an optical transmission line, and the guided signal light is reflected by another optical path conversion mirror and received by a surface-receiving optical element (planar photodiode).

  In an optical transmission system using an optical signal, an optical transmission path for propagating an optical signal is required in addition to a light emitting element and a light receiving element, and each light receiving and emitting element is optically coupled to the optical transmission path. . Since an optical signal is represented by the level of light intensity, it is important to maintain the light intensity in an optical transmission system. In addition, since an electric circuit board is required to mount the light emitting / receiving element, and this is mounted between the light receiving / emitting element and the optical transmission path, the light receiving / emitting element and the optical transmission path are separated from each other. . As a result, there is a problem that sufficient light intensity cannot be secured between the light emitting / receiving element and the optical transmission path.

  In the optical transmission system having such a structure, means for optically coupling between the light emitting / receiving element and the optical transmission line with high optical coupling efficiency is necessary to ensure sufficient light intensity. As an optical coupling means for realizing high optical coupling efficiency, one using an optical waveguide for propagating light between a light emitting / receiving element and an optical transmission line has been conventionally known (Patent Document 2). FIG. 7 shows an optical coupling means using an optical waveguide. Here, an example is shown in which an optical waveguide (optical pin) 903 is used for optical coupling between the optical element 901 and the optical transmission line 902.

Non-Patent Document 1 discloses that an optical waveguide for optically coupling between an optical element and an optical transmission line is formed by a so-called self-forming method. A method of forming the optical waveguide of the optical coupler by the self-forming method is shown in FIG. Here, an uncured ultraviolet curable resin 913 is disposed as a core resin on the light receiving and emitting surface of the optical element 911, a mask 914 having a predetermined pattern is placed thereon, and light such as ultraviolet rays is placed thereon. The core 912 is formed by irradiation.
Japanese Patent Publication No. 2006-120956 Japanese Patent Publication No. 2004-157438 The 20th Electronics Packaging Conference Lecture Meeting, 22C-07, “Optical connection of optical fiber and mask transfer method” Tokai University Hiroyuki Kubo et al., 2006.3.22

  However, the conventional optical coupler and the manufacturing method thereof have the following problems. The method of forming an optical waveguide by processing an optical fiber such as the above-described optical pin has a problem of lack of mass productivity. In addition, in the method of forming the core by the self-forming method (ultraviolet exposure method), although it is possible to increase the mass productivity, there is a problem that the reliability is low because the clad is not formed, so that the reliability is improved. In addition, there is a problem that it is difficult to dispose the uncured clad material so as to cover the core in order to form the clad around the core.

  In other words, if a large amount of clad material is supplied around the core, it may overflow and affect the surroundings, or the optical axis at the interface will be bent. On the other hand, if the clad material is small, the core cannot be covered sufficiently. There was a problem.

  Furthermore, there is a problem that it is difficult to form the clad into a predetermined shape. Before forming the core and the clad, it is possible to provide a damming part for supplying the core material and the clad material around the core using a commercially available dam agent, but it is formed using a dispenser. For this reason, it is impossible to accurately form the damming portion at a predetermined position in a predetermined shape. Since the shape of the cladding is affected by the shape of the damming portion, there is a problem that if the damming portion cannot be formed in a predetermined manner, the shape of the cladding cannot be formed in a predetermined manner.

  Accordingly, the present invention has been made to solve these problems, and a manufacturing method of an optical coupler with high productivity and an optical coupler capable of forming a core and a clad having a predetermined shape around the core and the periphery thereof. The purpose is to provide.

  According to a first aspect of the optical coupler manufacturing method of the present invention, an optical element is optically coupled to an optical circuit board including an electric circuit board and an optical transmission path provided substantially parallel to the electric circuit board. A method of manufacturing an optical coupler including an optical waveguide for simultaneously forming a core of the optical waveguide and a dam surrounding the core on the light receiving / emitting surface of the optical element or the opening of the electric circuit board. It includes a core manufacturing process and a clad manufacturing process for forming a clad inside the blocking portion.

  Another aspect of the method of manufacturing an optical coupler according to the present invention is characterized in that the core and the damming portion are formed of the same material.

  In another aspect of the method of manufacturing an optical coupler according to the present invention, the core material of the core is a photocurable resin.

  In another aspect of the optical coupler manufacturing method of the present invention, the core manufacturing step irradiates the core material with light through a first exposure mask having a pattern corresponding to the core and the blocking portion. The core and the damming portion are formed in the predetermined shape.

  In another aspect of the method of manufacturing an optical coupler according to the present invention, the core manufacturing step irradiates the core material with light using a mold that transmits light that is cured by the photocurable resin. The damming portion is formed in the predetermined shape.

  In another aspect of the method of manufacturing an optical coupler according to the present invention, in the cladding manufacturing step, the cladding is formed of a photocurable cladding material.

  According to another aspect of the optical coupler manufacturing method of the present invention, in the cladding manufacturing process, the cladding material is supplied at least inside the damming portion, and a second exposure mask is disposed on the cladding material. And irradiating the clad material with light through the second exposure mask.

  In another aspect of the method of manufacturing an optical coupler according to the present invention, the cladding manufacturing process includes a step of supplying the cladding material at least inside the damming portion, and a pattern corresponding to the cladding on the cladding material. Disposing the second exposure mask having, irradiating the cladding material with light through the second exposure mask, and removing the uncured cladding material. To do.

  In another aspect of the method of manufacturing an optical coupler according to the present invention, in the cladding manufacturing step, the cladding is formed of a thermosetting or thermoplastic cladding material.

  In another aspect of the optical coupler manufacturing method of the present invention, the cladding manufacturing process includes a step of supplying the cladding material at least inside the damming portion, and a shape corresponding to the cladding on the cladding material. A step of disposing the mold, a step of thermosetting in a state where the mold is disposed, and a step of releasing the mold.

  According to a first aspect of the optical coupler of the present invention, there is provided an optical circuit for optically coupling an optical element to an optical circuit board including an electric circuit board and an optical transmission path provided substantially parallel to the electric circuit board. An optical coupler including a waveguide, the optical waveguide core having a predetermined shape formed on at least one of a light receiving and emitting surface of the optical element and an opening of the electric circuit board, and surrounding the core As described above, a damming portion formed in a predetermined shape simultaneously with the core and a clad formed inside the damming portion are provided.

  Another aspect of the optical coupler of the present invention is characterized in that the damming portion has an opening at a predetermined position.

  Another aspect of the optical coupler of the present invention is characterized in that the damming portion is formed by arranging a plurality of columnar bodies.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of an optical coupler with high productivity and the optical coupler which can form a clad of a predetermined shape around a core and its circumference.

  A method for manufacturing an optical coupler and an optical coupler according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

  An optical coupler manufacturing method according to a first embodiment of the present invention and an optical coupler manufactured by using this manufacturing method will be described below with reference to FIGS. FIG. 1 is a schematic process diagram for explaining a method of manufacturing an optical coupler according to this embodiment, and FIG. 2 uses an optical coupler manufactured by the method of manufacturing an optical coupler according to this embodiment. The sectional view showing an embodiment in which the optical circuit board and the optical element are optically coupled and the bottom view of the optical element mounting substrate are shown.

  In FIG. 2, the optical coupler 100 according to the present embodiment optically couples the optical element 120 mounted on the optical element mounting substrate 121 and the optical transmission path 131 included in the optical circuit board 130 with high efficiency. It is used for. The optical circuit board 130 includes an electric circuit board 132 and an optical transmission path 131 installed substantially parallel thereto. The optical coupler 100 includes an element-side optical waveguide 110a installed on the light receiving / emitting surface 120a of the optical element 120 and a substrate-side optical waveguide installed on the opening 133 of the electric circuit board 132 formed on the upper surface of the optical transmission path 131. It is comprised with the waveguide 110b.

  The element-side optical waveguide 110a and the substrate-side optical waveguide 110b are respectively composed of cores 111a and 111b and clads 112a and 112b formed on the outer peripheral surfaces thereof, and the light receiving and emitting surfaces 120a and the electric circuit of the optical element 120, respectively. It is formed separately in the opening 133 of the substrate 132. The optical element mounting substrate 121 is electrically connected to the electric circuit substrate 132 with solder 151. The element side optical waveguide 110 a and the substrate side optical waveguide 110 b are integrally fixed together with the solder 151 by an adhesive 152.

  The bottom view of the optical element mounting substrate 121 shown in FIG. 2 is a view of the element side optical waveguide 110a formed on the optical element mounting substrate 121 as viewed from below, but a damming portion around the element side optical waveguide 110a. 141a is formed. Similarly, a damming portion 141b is also formed around the substrate-side optical waveguide 110b in the optical circuit board 130.

  By optically coupling the optical element 120 and the optical circuit board 130 using the optical coupler 100, the inside of the cores 111 a and 111 b is connected between the optical element 120 and the reflecting surface 134 provided in the optical transmission path 131. It is configured to transmit light, and thereby high optical coupling can be realized while suppressing attenuation of light.

  An optical coupler manufacturing method according to an embodiment of the present invention for manufacturing the optical coupler 100 as described above will be described below. FIG. 1 shows an example in which the element-side optical waveguide 110a is formed on the light receiving / emitting surface 120a of the optical element 120, but the substrate-side optical waveguide 110b may be formed in the opening 133 of the electric circuit board 132 as well. The same manufacturing method can be used.

  In the optical coupler manufacturing method of this embodiment, the element-side optical waveguide 110a is formed by the core manufacturing process shown in FIG. 1A and the clad manufacturing process shown in FIG. Here, the first exposure mask 142 and the second exposure mask 143 are used as molding means for forming the core 111a, the clad 112a, and the damming portion 141a. A means for irradiating a certain core material 114 and cladding material 115 with light is used.

  In the core manufacturing process, first, as a first step, the core material 114 is supplied to a position where the core 111a and the blocking portion 141a are formed. In the next second stage, the first exposure mask 142 is disposed on the core material 114, and the core 111a and the blocking portion 141a are formed by irradiating light from the top. Further, in the third stage, the core material 114 remaining uncured is removed.

  In the above core manufacturing process, in the first stage, a sufficient amount of core material 114 is formed on the optical element mounting substrate 121 to form the core 111a and the blocking portion 141a. In the second stage, the first exposure mask 142 having a light transmission pattern formed so as to transmit light only at the position where the core 111a and the blocking portion 141a are formed is disposed on the core material 114. . At this time, alignment is performed so that the formation position of the core coincides with the position of the light emitting and receiving unit of the optical element 120. Thereafter, light is irradiated from above the first exposure mask 142, and the light transmitted through the first exposure mask 142 cures the core material 114. As a result, the core 111 a and the blocking portion 141 a are formed on the optical element mounting substrate 121. At this time, the light is preferably parallel light.

  The core 111a and the blocking portion 141a formed by the core manufacturing process are formed in a shape corresponding to the light transmission pattern formed on the first exposure mask 142. Therefore, by appropriately forming the light transmission pattern of the first exposure mask 142, the core 111a and the damming portion 141a having a predetermined shape can be formed.

  In the first stage of the core manufacturing process, the core material 114 is supplied onto the optical element mounting substrate 121. However, in FIG. 1A, a member for blocking the core material 114 is not particularly used. When an appropriate member is disposed so as to surround the position where the damming portion 141a is formed and the core material 114 is supplied to the inside thereof, the core 111a and the damming portion 141a are reduced with a smaller amount of the core material 114. Can be formed.

  FIG. 1A shows a case where the means for supporting the first exposure mask 142 on the upper portion of the core material 114 in the second stage is not particularly used.

  In the third stage of the core manufacturing process, the uncured core material 114 excluding those used for forming the core 111a and the blocking portion 141a is removed using, for example, ethanol. As a result, the core 111a and the damming portion 141a formed by curing the core material 114 into a predetermined shape are left on the optical element mounting substrate 121.

  Subsequent to the core manufacturing process, a cladding manufacturing process is performed. In the cladding manufacturing process, first, as a first step, the cladding material 115 is supplied onto the core 111a and the damming portion 141a formed in the core manufacturing process. In the next second stage, the second exposure mask 143 is disposed on the core 111a and the blocking portion 141a, and the cladding 112a is formed by irradiating light from the upper portion. Further, in the third stage, the cladding material 115 remaining uncured is removed.

  In the above clad manufacturing process, a sufficient amount of the clad material 115 is supplied so as to cover the core 111a and the blocking portion 141a in the first stage. If the clad material 115 is not supplied sufficiently, the clad 112a may not be formed up to the tip of the core 111a. In the optical coupler manufacturing method of this embodiment, since the damming portion 141a is formed in the core manufacturing process, the cladding 112a is formed up to the tip of the core 111a by filling the cladding material 115 therein. It becomes possible. In addition, since the clad material 115 can be prevented from spreading to the periphery, the clad 112a can be formed with a smaller amount of the clad material 115.

  In the second stage of the clad manufacturing process, a clad 112 a having a predetermined shape can be formed by appropriately forming a light transmission pattern on the second exposure mask 143. In FIG. 1B, a clad material 115 having a predetermined width is hardened not only inside the blocking portion 141a but also outside thereof. As another example, the clad 112a can be formed only inside the damming portion 141a by forming a light transmission pattern so as to transmit light only inside the damming portion 141a.

  In the third stage, the uncured cladding material 115 left outside the blocking portion 141a and the like is removed using, for example, ethanol. Thereby, the element side optical waveguide 110a provided with the core 111a and the clad 112a of a predetermined shape is formed.

  As described above, in the method of manufacturing an optical coupler according to the present embodiment, the core 111a and the blocking portion 141a are formed simultaneously using the same core material 114, thereby shortening the manufacturing process. . In addition, it is a highly mass-produced manufacturing method capable of forming the core 111a and the clad 112a in a predetermined shape at a predetermined position by molding means using the first exposure mask 142 and the second exposure mask 143. ing.

  The core manufacturing process of this embodiment will be described in more detail with reference to FIG. FIG. 3 shows the case where the support stage 144 that supports the first exposure mask on the upper portion of the core material 114 is used in the second stage. In the first step of FIG. 3A, the optical element mounting substrate 121 is installed horizontally. In FIG. 3, the display of the optical element 120 is omitted. In the next second step, the support table 144 is arranged at a predetermined position on the optical element mounting substrate 121. The support base 144 is disposed so as to surround at least a region wider than the installation position of the damming portion 141a.

  In the third step of FIG. 3C, the core material 114 is supplied into the region surrounded by the support table 144. At this time, the core material 114 is supplied beyond the position and height at which the core 111a and the blocking portion 141a are formed. In the fourth step, the first exposure mask 142 is placed on the support table 144. The first exposure mask 142 is formed with a light transmission pattern so as to transmit light only at positions where the core 111a and the blocking portion 141a are formed.

  In the fifth step of FIG. 3E, light is irradiated from above the first exposure mask 142 using the light guide 145. For example, UV light can be used as the irradiation light. The light transmitted according to the light transmission pattern of the first exposure mask 142 reaches the core material 114, and the core material 114 of the portion irradiated with the light is cured. The core material 114 cured in this way becomes the core 111a and the blocking portion 141a.

  In the sixth step of FIG. 3F, the first exposure mask 142 and the support table 144 are removed, and the uncured core material 114 is removed. As a removal method, the uncured core material 114 can be removed by washing with, for example, ethanol. FIG. 3G shows a state where the core 111 a and the damming portion 141 a are completed on the optical element mounting substrate 121.

  Next, the cladding manufacturing process of the present embodiment will be described in more detail with reference to FIG. In the first step of FIG. 4A, the optical element mounting substrate 121 including the core 111a and the damming portion 141a produced in the core manufacturing process is horizontally installed. .

  In the second step of FIG. 4B, the clad material 115 is supplied into the region surrounded by the blocking portion 141a. At this time, the clad material 115 is supplied to at least the height of the core 111a at least inside the blocking portion 141a. In the third step, the second exposure mask 143 is placed on the damming portion 141a. On the second exposure mask 143, a desired shape of the cladding 112a is formed as a light transmission pattern.

  In the fourth step of FIG. 4D, light is irradiated from above the second exposure mask 143 using the light guide 145. Again, for example, UV light can be used as the irradiation light. The light transmitted according to the light transmission pattern of the second exposure mask 143 reaches the cladding material 115 and the portion of the cladding material 115 irradiated with the light is cured. The clad material 115 thus cured becomes the clad 112a.

  In the fifth step of FIG. 4E, the second exposure mask 143 and the support base 144 are removed, and the uncured core material 114 is removed. As a removal method, the uncured cladding material 115 can be removed by washing with, for example, ethanol. FIG. 4F shows a state in which the element-side optical waveguide 110a including the core 111a and the clad 112a and the damming portion 141a are completed on the optical element mounting substrate 121.

  As described above, according to the present embodiment, by forming the damming portion having a predetermined shape at a predetermined position simultaneously with the formation of the core, the cladding having a predetermined shape can be formed around the core and the periphery thereof. It is possible to provide an optical coupler manufacturing method and an optical coupler that are capable of mass production.

As another embodiment of the manufacturing method of the optical coupler of the present invention, a thermosetting resin or a thermoplastic resin is used as a cladding material, and the thermosetting cladding material is put into a mold having a predetermined shape and cured by heating. The clad can be formed by putting a thermoplastic clad material into a mold having a predetermined shape and cooling it in a heated or heated state.
It is also possible to use hot air as the heating method. It is also possible to form a clad by applying hot air to a mold having a predetermined shape and curing the clad material by the passed heat.

  According to the method for manufacturing an optical coupler of the present invention, it is possible to appropriately form a damming portion having a preferable shape. In the embodiment shown in FIG. 2, the blocking portion 141a is formed in a rectangular shape surrounding the core 111a and the clad 112a. In addition to the shape surrounding the entire circumference of the clad 112a, for example, a plurality of columnar bodies 203 arranged as shown in FIG.

  In the dam member 202 shown in FIG. 5, a plurality of gaps are formed between the columnar bodies 203, but even in such a shape, each of the dam members 202 is caused by the viscosity of the core material 114 and the clad material. It is possible to confine inside. The number, the arrangement interval, and the like of the columnar bodies 203 can be appropriately determined from the diameter of the clad, the viscosity of the core material 114 and the clad material, and the like. Further, in order to remove the uncured core material 114 and the clad material with, for example, ethanol, a shape in which a gap is provided like the dam member 202 is preferable.

  Yet another embodiment of the weir is shown in FIG. The dam member 302 of the present embodiment has a rectangular shape that surrounds the core 301 similar to the dam member 141a shown in FIG. 2, and is further provided with an opening 303. By appropriately providing such an opening 303, the uncured core material 114 or the cladding material 115 can be easily removed. The size and the like of the opening 303 can be determined from the viscosity of the core material 114 and the clad material 115, ease of cleaning, and the like.

  In addition, the description in this Embodiment shows an example of the optical coupler which concerns on this invention, and its manufacturing method, It is not limited to this. The detailed configuration and detailed operation of the optical coupler and the manufacturing method thereof in this embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is a schematic process drawing explaining the manufacturing method of the optical coupler which concerns on embodiment of this invention. It is the top view and sectional drawing which show the Example which optically coupled the optical circuit board and the optical element using the optical coupler which concerns on embodiment of this invention. It is a detailed process drawing explaining the core manufacturing process of this embodiment. It is a detailed process drawing explaining the clad manufacturing process of this embodiment. It is a perspective view which shows another Example of a dam part. It is a perspective view which shows another Example of a dam part. It is a figure which shows an example of the conventional optical coupling means. It is a figure which shows the example which forms the optical waveguide for the conventional optical coupling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical coupler 110a, 110b Optical waveguide 111a, 111b, 201,301 Core 112a, 112b Clad 114 Core material 115 Clad material 120, 901, 911 Optical element 120a Light receiving / emitting surface 121 Optical element mounting substrate 130 Optical circuit board 131, 902 Optical transmission path 132 Electric circuit board 133 Opening part 134 Reflecting surface 141a, 141b Damping part 142 First exposure mask 143 Second exposure mask 144 Support base 145 Light guide 151 Solder 152 Adhesive 202, 302 Damping part 203 Columnar body 303 Opening

Claims (13)

An optical coupler manufacturing method comprising: an optical circuit board comprising: an optical circuit board; and an optical circuit board comprising an optical transmission line provided substantially parallel to the electric circuit board, and an optical waveguide for optically coupling an optical element. ,
A core manufacturing process for simultaneously producing a core of the optical waveguide and a weir surrounding the core at the light emitting / receiving surface of the optical element or the opening of the electric circuit board; and
And a clad manufacturing process for forming a clad inside at least the damming portion. The said core manufacturing process forms the said core and the said damming part with the same material. The manufacturing method of the optical coupler of Claim 1 characterized by the above-mentioned. The method for manufacturing an optical coupler according to claim 1, wherein the core material of the core is a photocurable resin. The core manufacturing step forms the core and the damming portion in the predetermined shape by irradiating light to the core material through a first exposure mask having a pattern corresponding to the core and the damming portion. The method of manufacturing an optical coupler according to claim 3. In the core manufacturing process, the core and the damming portion are formed in the predetermined shape by irradiating the core material with light using a mold that transmits light to be cured by the photocurable resin. The manufacturing method of the optical coupler of Claim 3. The method for manufacturing an optical coupler according to claim 1, wherein the cladding is formed of a photocurable cladding material. The clad manufacturing process includes the steps of supplying the clad material to at least the inside of the damming portion, disposing a second exposure mask on the clad material, and the clad through the second exposure mask. Irradiating the material with light. The method of manufacturing an optical coupler according to claim 6. The clad manufacturing process includes the step of supplying the clad material at least inside the damming portion, the step of disposing a second exposure mask having a pattern corresponding to the clad on the clad material, and the second The method of manufacturing an optical coupler according to claim 6, comprising: irradiating the clad material with light through the exposure mask; and removing the uncured clad material. 6. The method of manufacturing an optical coupler according to claim 1, wherein in the clad manufacturing step, the clad is formed of a thermosetting or thermoplastic clad material. The clad manufacturing process includes a step of supplying the clad material at least inside the damming portion, a step of placing a mold having a shape corresponding to the clad on the clad material, and a state in which the die is disposed. The method for manufacturing an optical coupler according to claim 9, comprising a step of thermosetting and a step of releasing the mold. An optical coupler provided with an optical waveguide for optically coupling an optical element to an optical circuit board comprising an electric circuit board and an optical transmission path provided substantially parallel to the electric circuit board,
A core of the optical waveguide having a predetermined shape formed on at least one of the light emitting / receiving surface of the optical element and the opening of the electric circuit board;
A damming portion formed in a predetermined shape simultaneously with the core so as to surround the core;
An optical coupler comprising: a clad formed inside the damming portion. The optical coupler according to claim 13, wherein the damming portion has an opening at a predetermined position. The optical coupler according to claim 13, wherein the damming portion is formed by arranging a plurality of columnar bodies.

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