JP4865600B2 - Optical coupler - Google Patents

Description

  The present invention relates to an optical coupler for positioning and optically coupling an optical element mounted on an optical element mounting substrate and an optical waveguide provided on the optical circuit board.

  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 on-board optical interconnection, a multilayer printed board on which an optical waveguide disclosed in Patent Document 1 is formed is known. Here, the signal light emitted in the direction perpendicular to the substrate from the surface emitting element (VCSEL) mounted on the substrate surface is reflected by the optical path conversion mirror formed in the optical wiring to guide the optical waveguide. The guided signal light is reflected by another optical path conversion mirror and received by a surface-receiving optical element (planar photodiode).

  In such an optical circuit board, the optical coupling loss between the light emitting element and the light receiving element and the optical waveguide greatly affects the attenuation of the signal. Therefore, in order to suppress such signal attenuation, an optical coupling means for performing alignment between the optical element and the optical waveguide with high accuracy of several μm is required.

As a conventional optical coupling means for performing high-precision alignment as described above on an optical circuit board, for example, the one disclosed in Patent Document 2 shown in FIG. 8 is known. In Patent Document 2, alignment marks 904 and 905 for alignment are applied to a substrate 902 on which an optical element 901 is mounted and an optical circuit substrate 903, respectively, and applied to the alignment mark 904 and the optical circuit substrate 903 applied to the substrate 902, respectively. The aligned alignment mark 905 is aligned and mounted.
JP 2006-120956 A JP 2005-294444 A

  However, the conventional optical coupling means has the following problems. The alignment mark for alignment needs to be attached to a position that can be visually recognized when mounted on a substrate or waveguide, but when it is attached to a position away from the optical coupling portion where the optical element is provided. In this case, the relative position accuracy in the optical coupling portion is lowered, and it becomes difficult to achieve a high accuracy of several μm.

  Also, if the substrate on which the optical element is mounted or the optical circuit board is thermally expanded at the time of mounting, the distance between the alignment mark and the optical coupling portion changes due to the difference in coefficient of thermal expansion between them, and as a result, the relative position accuracy is increased. There is also a problem that it is further reduced.

  Accordingly, the present invention has been made to solve these problems, and includes an optical coupler that is provided with a coupling path for optically coupling two substrates and that can be positioned with high precision on this coupling path. The purpose is to provide.

According to a first aspect of the optical coupler of the present invention, an optical element fixed on an optical element mounting substrate and an optical waveguide formed on the optical circuit board are arranged on an optical axis on a reflecting surface provided on the optical waveguide. The one end face covers the light receiving and emitting part of the optical element and is fixed on the optical element mounting substrate , and the other end face has a first fitting part. Are formed on the optical circuit board through which the optical axis changed by the reflection surface passes, and a second fitting portion is formed on the other end surface. second and coupling path, wherein the first fitting part and the one of the second fitting portion and the other has a convex portion of the unimodal formed in a convex lens shape the convex portions the refractive index of the convex portion with a recess to be fitted is higher than the refractive index of the recess, before by fitting the said and the protrusion recess And positioning the first coupling path and the second coupling path, characterized in that it is optically coupled.

  As described above, according to the present invention, a coupling path for optically coupling the optical element and the optical waveguide is provided on each of the optical circuit board including the optical element-mounted substrate and the optical waveguide. An optical coupler that can be positioned with high accuracy by fitting the paths can be provided.

  In addition, even when the optical element mounting substrate and the optical circuit substrate are formed of a material having a large difference in thermal expansion coefficient, the configuration is such that positioning is performed by fitting two coupling paths. It is possible to reduce the displacement of the optical coupling path due to. Furthermore, misalignment due to self-alignment of solder when the optical element mounting substrate and the optical circuit substrate are electrically connected can be prevented by fitting the two coupling paths.

  The configuration of the optical coupler in 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.

  In the present invention, optical coupling between a substrate on which an optical element is mounted and an optical circuit substrate having an optical waveguide is realized by using an optical coupler having an optical axis in a direction orthogonal to the optical axis of the optical waveguide. A first embodiment of the optical coupler of the present invention will be described below with reference to FIG. The lower part in FIG. 1 is a sectional view schematically showing the first embodiment of the optical coupler of the present invention, and the upper part is the optical element mounting substrate 11 and the light among the lower parts. Only the element 10 and the first coupling path 110 are taken out and viewed from below.

  In FIG. 1, an optical circuit board 20 includes an electric circuit board 21 and an optical waveguide 22 that guides light in a direction parallel to the electric circuit board 21, and a reflection surface 23 is provided at a predetermined position of the optical waveguide 22. ing. The electric circuit board 21 has a structure including conductor pattern layers 21b on both sides of an insulating layer 21a, and the optical waveguide 22 has a structure including a core layer 22a for guiding light and a clad layer 22b surrounding the core layer 22a. .

  The reflection surface 23 provided in the middle of the optical waveguide 22 changes the optical axis of the optical waveguide 22 in the vertical direction, and the light emitted from the optical element 10 is arranged by arranging the optical element 10 in the vertical direction. Can be guided to the core layer 22a of the optical waveguide 22, or the light guided through the core layer 22a can be emitted to the optical element 10.

  The optical coupler 100 according to the present embodiment includes a first coupling path 110 fixed to the optical element mounting substrate 11 on which the optical element 10 is mounted, and a second coupling path 120 fixed to the optical circuit board 20. Has been.

  The first coupling path 110 is fixed on the surface of the optical element mounting substrate 11 on which the optical element 10 is mounted, and is installed so as to cover the light receiving and emitting part of the optical element 10 at the center portion of one end surface thereof. Yes. It is preferable to install the first coupling path 110 so that the optical axis of the first coupling path 110 coincides with the optical axis of the optical element 10. Here, the shape of the first coupling path 110 is a prismatic shape. However, the shape is not limited to this, and an optical element is formed at the center of one end surface of the first coupling path 110 in any shape. It is good to fix so that 10 may be arrange | positioned.

  On the other hand, the second coupling path 120 is fixed at a position where the reflecting surface 23 is installed on the optical circuit board 20, and the optical axis of the second coupling path 120 is changed in the vertical direction by the reflecting surface 23. The optical waveguide 22 is preferably installed so as to coincide with the optical axis. The shape of the second coupling path 120 is a prismatic shape in accordance with the shape of the first coupling path 110, but can be appropriately changed according to the shape of the first coupling path 110.

  A first fitting portion 111 is provided on each of the first coupling path 110 and the second coupling path 120 on the end face opposite to the one end face fixed to the optical element mounting substrate 11 and the optical circuit board 20, respectively. And the 2nd fitting part 121 is formed. In the embodiment shown in FIG. 1, a cylindrical first fitting portion 111 having a convex cross section is formed on the end surface of the first coupling path 110, and the end surface of the second coupling path 120 is fitted. A second fitting portion 121 having a concave cross-section that fits with the joint portion 111 is formed.

  As described above, the first fitting portion 111 and the second fitting portion 121 are formed on the end faces of the first and second connecting passages 110 and 120, and these are fitted. The optical element mounting substrate 11 can be positioned and fixed on the optical circuit substrate 20 with high accuracy.

  That is, the first fitting portion 111 is positioned with high accuracy with respect to the optical axis of the optical element 10 to fix the first coupling path 110 to the optical element mounting substrate 11, and is changed vertically by the reflection surface 23. The second fitting portion 121 is positioned with high accuracy with respect to the optical axis of the optical waveguide 22 to fix the second coupling path 110 to the optical circuit board 20. Thereby, when the 1st fitting part 111 and the 2nd fitting part 121 are fitted, the optical axis of the optical element 10 and the optical axis of the optical waveguide 22 changed perpendicularly by the reflective surface 23 are the same. Positioning can be performed so as to match.

  In addition, the first coupling path 110 and the second coupling path 120 are optical coupling transmission paths and at the same time a positioning unit that positions the optical element mounting substrate 11 and the optical circuit board 20. Thus, there is no problem that an error in the relative position occurs between the optical coupling transmission line and the positioning portion. Even if the optical element mounting substrate 11 and the optical circuit board 20 have different thermal expansion coefficients, the positional deviation between the optical element 10 and the reflecting surface 23 due to the difference in thermal expansion can be reduced, and the optical coupling efficiency can be reduced. A decrease can be avoided.

  The optical element mounting substrate 11 is fixed to the upper surface of the optical circuit substrate 20 using solder 130. The solder 130 also serves to electrically connect the optical element mounting substrate 11 and the optical circuit substrate 20. When two substrates are connected with the solder 130, there has been a risk that the optical coupling transmission line may be displaced due to self-alignment in the past, but in this embodiment, the first coupling path and the first coupling path that are fitted to each other are used. Since the optical element 10 and the optical waveguide 22 are positioned by the optical coupler 100 including two coupling paths, there is no risk of displacement due to self-alignment, and it is possible to suppress a decrease in optical coupling efficiency. It has become.

  The optical coupler 100 of this embodiment can be easily formed using a mold material having a predetermined shape. As an example, a method of forming the first coupling path 110 fixed to the optical element mounting substrate 11 will be described below with reference to FIG.

  In FIG. 2, a resin 140 serving as the first coupling path 110 is disposed in the optical opening (propagation part) of the optical element mounting substrate 11 on which the optical element 10 is mounted (FIG. 2A), and this is uncured. In this state, a mold member 141 having a predetermined concave tip portion is pushed in, and the resin 140 is cured in that state (FIG. 2B). Then, when the mold member 141 is removed after the resin 140 is cured, the first coupling path 110 fixed on the optical element mounting substrate 11 is formed (FIG. 2C).

  Similarly, in the second coupling path 120, a resin serving as the second coupling path 120 is disposed in the light opening portion where the reflecting surface 23 of the optical circuit board 20 is installed, and a mold material having a predetermined convex tip portion is formed. It can be formed by using.

  Alternatively, as another method of forming the first coupling path 110 and the second coupling path 120, a mold having a predetermined size is arranged in advance in the optical opening of the optical element mounting substrate 11 or the optical circuit board 20, A method of filling the inside of the mold with a resin can also be used. After the mold is filled with the resin, it can be formed by pressing a mold material having a concave or convex tip similar to the above in an uncured state and curing the resin in that state.

  Another example of this embodiment will be described below with reference to FIG. The lower part in FIG. 3 is a schematic cross-sectional view of the optical coupler, and the upper part shows only the optical element mounting substrate 11, the optical element 10, and the first coupling path 150 out of the lower part. The state seen from below is shown. In the embodiment shown in FIG. 3, the first fitting portion and the second fitting portion of the optical coupler 101 are different in shape from those shown in FIG. 1. In other words, the first coupling path 150 fixed to the optical element mounting substrate 11 is provided with a first fitting portion 151 in which two convex portions are formed in parallel. In addition, the second coupling path 160 fixed to the optical circuit board 20 is provided with a second fitting portion 161 in which two concave portions having a shape fitting with the first fitting portion 151 are formed in parallel. It has been.

  When the optical coupler 101 configured as described above is used, the optical element mounting board 11 and the optical circuit board are fitted by fitting the first fitting part 151 and the second fitting part 161 together. 20 can be positioned with high accuracy. In addition, there is no restriction | limiting in particular in the number of installation of the convex part of the 1st fitting part 151 and the 2nd fitting part 161, and a recessed part, You may increase more than two. Alternatively, the first fitting portion 151 may be formed with a concave portion, and the second fitting portion 161 may be formed with a convex portion.

  In the present embodiment, the first fitting portion 111 and the second fitting portion 121 having the shape shown in FIG. 1, or the first fitting portion 151 and the second fitting portion having the shape shown in FIG. However, the shape is not limited to 161, and other shapes may be used. Whatever the shape, if the first fitting portion and the second fitting portion can be easily fitted, and when they are fitted, they can be positioned with high accuracy. good.

  Moreover, there is no restriction | limiting in particular in the installation position of a 1st fitting part and a 2nd fitting part, but when not forming in the center part which an optical axis passes and forming in the peripheral part, the 1st fitting It is preferable that both the central part surrounded by the part and the second fitting part intersect perpendicularly to the optical axis.

  A second embodiment of the present invention will be described below with reference to FIG. The lower part in FIG. 4 is a sectional view schematically showing the second embodiment of the optical coupler of the present invention, and the upper part is the optical element mounting substrate 11 and the light among the lower parts. Only the element 10 and the first coupling path 210 are taken out and viewed from below. In the optical coupler 200 of the present embodiment, a convex first fitting portion 211 is formed at a position that intersects with the optical axis of the end surface of the first coupling path 210, and is formed on the end surface of the second coupling path 220. A concave second fitting part 221 is formed. The first fitting portion 211 and the second fitting portion 221 of the present embodiment have a fitting surface formed in a curved shape, and are formed so that the mutual fitting surfaces coincide with each other accurately.

  Also in this embodiment, when the first fitting portion 211 and the second fitting portion 221 are fitted, the light of the optical waveguide 22 that is changed perpendicularly by the optical axis of the optical element 10 and the reflecting surface 23. A first fitting portion 211 and a second fitting portion 221 are formed so that the axes coincide with each other.

  In this embodiment, the refractive index of the first coupling path 210 and the refractive index of the second coupling path 220 are different from each other, and the first fitting section 211 having a convex shape is provided. The refractive index of the coupling path 210 is set higher than the refractive index of the second coupling path 220. Thereby, the 1st fitting part 211 can play the role of a convex lens, and can make it condense to optical axis vicinity.

  Further, by forming the convex surface of the first fitting portion 211 in the same manner as the aspherical lens, it is possible to collect light at one point (focal point). In this case, it is preferable to form the convex surface of the first fitting portion 211 as follows. That is, when the optical element 10 is a light emitting element, the focal point is formed on the reflecting surface 23, and when the optical element 10 is a light receiving element, the focal point is positioned on the light receiving surface of the optical element 10. It is good to form like this.

In the embodiment shown in FIG. 4, the first fitting portion 211 has a convex shape, and the second fitting portion 221 has a concave shape. On the contrary, the first fitting portion 211 has a concave shape. It may be formed in a shape, and the second fitting portion 221 may be formed in a convex shape. In this case, by making the refractive index of the second coupling path 220 higher than the refractive index of the first coupling path 210 , the second fitting portion 221 can serve as a convex lens.

  Another example of this embodiment will be described with reference to FIG. The lower part in FIG. 5 is a schematic cross-sectional view of the optical coupler, and the upper part shows only the optical element mounting substrate 11, the optical element 10, and the first coupling path 250 out of the lower part. The state seen from below is shown. In the present embodiment, the shape of the first fitting portion 251 provided in the first coupling path 250 is not a curved surface shape, but is formed in a truncated pyramid shape including a plurality of planes. Correspondingly, the second fitting portion 261 provided in the second coupling path 260 is also formed in a concave shape composed of a plurality of planes.

  Even if the shape of the first fitting portion 251 and the second fitting portion 261 is a convex shape and a concave shape composed of a plurality of planes as described above, the refractive index of the first coupling path 250 is set to the second coupling. By making it higher than the refractive index of the path 260, a lens effect can be obtained. Here, the shape of the first fitting portion 251 in FIG. 5 is a truncated pyramid shape, but is not limited thereto, and may be a pyramid shape, a cone shape, a truncated cone shape, or the like.

  As described above, in the present embodiment, in either the first coupling path or the second coupling path, a convex first fitting portion or second fitting portion is formed at a position intersecting the optical axis. The lens effect is obtained by making the refractive index of the coupling path on the side where the convex fitting portion is formed larger than the refractive index of the other coupling path.

  Thereby, even when the spread angle of light passing through the optical coupling path is large, the spread of light can be suppressed by the lens effect at the fitting interface, and the coupling efficiency can be improved. That is, when the optical element 10 is a light emitting element, the light emitted from the optical element 10 is efficiently condensed on the reflecting surface 23, while when the optical element 10 is a light receiving element, it passes through the optical waveguide 22. The light that is reflected and reflected by the reflecting surface 23 can be efficiently incident on the optical element 10.

  A third embodiment of the present invention will be described below with reference to FIG. The lower part in FIG. 6 is a cross-sectional view schematically showing the third embodiment of the optical coupler of the present invention, and the upper part is the optical element mounting substrate 11, the light among the lower parts. Only the element 10, the first coupling path 310, and the convex lens 330 are taken out and shown in a state viewed from below. In the optical coupler 300 of the present embodiment, the first fitting portion 311 having a concave cross section at each position intersecting the optical axis of the end surface of the first coupling path 310 and the end surface of the second coupling path 320. The second fitting portion 321 is formed, and the convex lens 330 is fitted and sandwiched between the first fitting portion 311 and the second fitting portion 321.

  The convex lens 330 has a refractive index higher than that of at least one of the first coupling path 310 and the second coupling path 320. Thereby, similarly to the second embodiment, light can be efficiently condensed on the reflecting surface 23 or the optical element 10 by the light condensing effect by the convex lens 330.

  Further, when the refractive index of the convex lens 330 is higher than the refractive indexes of both the first coupling path 310 and the second coupling path 320, the light condensing effect by the convex lens 330 can be further enhanced.

  As described above, in the optical coupler 300 of the present embodiment, even when the spread angle of light passing through the optical coupling path is large, the light spread can be suppressed by the light collecting effect of the convex lens 330, and the coupling efficiency is improved. Is possible. When the refractive index of the convex lens 330 is higher than the refractive indexes of both the first coupling path 310 and the second coupling path 320, a higher light condensing effect can be realized.

  A fourth embodiment of the present invention will be described below with reference to FIG. The lower part in FIG. 7 is a cross-sectional view schematically showing a fourth embodiment of the optical coupler of the present invention, and the upper part is the optical element mounting substrate 11 and the light among the lower parts. Only the element 10 and the first coupling path 410 are taken out and shown from below. In the optical coupler 400 of the present embodiment, the first fitting portion 411 and the second fitting portion 421 are arranged in the same manner as the optical coupler 101 of the first embodiment shown in FIG. Each of the end surface 410 and the end surface of the second coupling path 420 is provided in a peripheral portion that does not intersect the optical axis.

  In the optical coupler 400 of the present embodiment, in addition to forming the first fitting portion 411 and the second fitting portion 421, the first coupling path 410 and the second coupling path 420 are respectively provided. Core portions 410a and 420a that transmit light are formed.

  That is, in the first coupling path 410, a core portion 410a is formed so as to face the light receiving and emitting portion of the optical element 10 and to be perpendicular thereto. By making the refractive index of the core portion 410a higher than the portion (cladding portion 410b) surrounding the core portion 410a of the first coupling path 410, the first coupling path 410 is an optical waveguide having the core portion 410a and the cladding portion 410b. It can be a waveguide.

  Similarly, in the second coupling path 420, the core part 420a of the second coupling path 420 is formed on the extension of the core part 410a of the first coupling path 410. By making the refractive index of the core part 420a higher than the part (cladding part 420b) surrounding the core part 420a of the second coupling path 420, the second coupling path 420 is an optical waveguide having the core part 420a and the cladding part 420b. It can be a waveguide.

  As described above, the optical coupler 400 of this embodiment is formed so as to be an optical waveguide having a core portion and a cladding portion, thereby efficiently guiding light between the optical element 10 and the optical waveguide 22. Thus, the coupling efficiency between the optical element 10 and the optical waveguide 22 can be improved. Further, according to the optical coupler 400 of the present embodiment, even when the optical element 10 and the optical waveguide 22 are separated from each other, light can be confined and efficiently guided in the core portion, thereby preventing a decrease in coupling efficiency. can do.

  Note that the description in the present embodiment shows an example of the optical coupler according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the optical coupler in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is a schematic diagram explaining 1st Embodiment of the optical coupler of this invention. It is a figure explaining the method of forming the 1st coupling path of this invention. It is a schematic diagram explaining another Example of 1st Embodiment of the optical coupler of this invention. It is a schematic diagram explaining 2nd Embodiment of the optical coupler of this invention. It is a schematic diagram explaining another Example of 2nd Embodiment of the optical coupler of this invention. It is a schematic diagram explaining 3rd Embodiment of the optical coupler of this invention. It is a schematic diagram explaining 4th Embodiment of the optical coupler of this invention. It is a figure for demonstrating the method of aligning the conventional optical circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical element 11 Optical element mounting substrate 20 Optical circuit board 21 Electric circuit board 22 Optical waveguide 23 Reflecting surface 100, 101, 200, 300, 400 Optical coupler 110, 150, 210, 250, 310, 410 1st coupling path 111, 151, 211, 251, 311, 411 First fitting portion 120, 160, 220, 260, 320, 420 Second coupling path 121, 161, 221, 261, 321, 421 Second fitting portion 130 Solder 140 Resin 141 Mold Material 330 Convex Lens

Claims (1)

An optical coupler that optically couples an optical element fixed on an optical element mounting substrate and an optical waveguide formed on the optical circuit board by changing an optical axis with a reflection surface provided on the optical waveguide. And
A first coupling path in which one end face covers the light receiving and emitting part of the optical element and is fixed on the optical element mounting substrate, and a first fitting part is formed on the other end face ;
A second coupling path having one end face fixed on the optical circuit board through which the optical axis changed by the reflecting surface passes, and a second fitting portion formed on the other end face ;
Either the first fitting portion or the second fitting portion has a single-peak convex portion formed in a convex lens shape, and the other has a concave portion that fits the convex portion. The refractive index of the part is higher than the refractive index of the recess,
The optical coupler is characterized in that the first coupling path and the second coupling path are positioned and optically coupled by fitting the convex portion and the concave portion .

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