JP2015087712A - Optical waveguide, opto-electric hybrid substrate, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide that suppresses deterioration in a transmission characteristic and is able to perform high quality optical communication, and to provide an opto-electric hybrid substrate and an electronic apparatus including such the optical waveguide.SOLUTION: An optical waveguide 1 includes: a core part 14; side surface clads 15 and clad layers 11, 12 adjacent to the core part 14; inclined surfaces 171, 172 lined along an axis direction of the core part 14 in the middle of the core part 14. The inclined surfaces 171, 172 have surface roughness different from each other. The inclined surface 171 is a mirror surface, and the inclined surface 172 has a larger surface roughness than that of the inclined surface 171.

Description

  The present invention relates to an optical waveguide, an opto-electric hybrid board, and an electronic device.

  In recent years, optical waveguides are becoming popular as a means for guiding an optical signal from one point to another point. This optical waveguide has a linear core part and a clad part provided so as to cover the periphery thereof. The core part is made of a material that is substantially transparent to light, and the cladding part is made of a material having a refractive index lower than that of the core part.

  In the optical waveguide, light introduced from one end of the core portion is conveyed to the other end while being reflected at the boundary with the cladding portion. A light emitting element such as a semiconductor laser is disposed on the incident side of the optical waveguide, and a light receiving element such as a photodiode is disposed on the emission side. Light incident from the light emitting element propagates through the optical waveguide, is received by the light receiving element, and performs communication based on the flickering pattern of the received light or its intensity pattern.

  When such an optical waveguide replaces, for example, the electrical wiring in the signal processing board, problems specific to electrical signals such as generation of high-frequency noise and deterioration of the electrical signal are eliminated, and the signal processing board can be further increased in throughput. It is expected to be.

  When replacing electrical wiring with an optical waveguide, it is necessary to perform mutual conversion between an electrical signal and an optical signal. Therefore, an optical device including a light emitting element, a light receiving element, and an optical waveguide that optically connects between them. Waveguide modules have been developed.

  For example, as disclosed in Patent Document 1, an optical waveguide used in such an optical waveguide module converts a light path and optically connects to a light emitting element or a light receiving element. A mirror surface constituted by a cut surface cut in a direction inclined with respect to the axis of the core portion is provided.

Japanese Patent Laid-Open No. 10-300961

  In the optical waveguide according to Patent Document 1, a V-shaped groove that crosses the core portion is formed, and one of the two side surfaces of the inner wall surface of the V-shaped groove is used as a mirror surface.

  However, in the optical waveguide according to Patent Document 1, unnecessary light reflection occurs on the other side surface of the two side surfaces described above, and the reflected light interferes with regular light (light propagating through the core portion), There was a problem that crosstalk occurred.

  An object of the present invention is to provide an optical waveguide that can suppress the deterioration of transmission characteristics and perform high-quality optical communication, and an opto-electric hybrid board and an electronic apparatus including the optical waveguide.

Such an object is achieved by the present inventions (1) to (8) below.
(1) the core part;
A cladding portion adjacent to the core portion;
A first surface and a second surface arranged in the middle of the core portion or on an extension line along the axial direction of the core portion;
The optical waveguide, wherein the first surface and the second surface have different surface roughness.

(2) The first surface is a mirror surface inclined with respect to the axis,
The optical waveguide according to (1), wherein the second surface has a surface roughness larger than that of the first surface.

  (3) The optical waveguide according to (2), wherein the first surface and the second surface are inclined in directions opposite to each other with respect to the axis.

  (4) The optical waveguide according to (3), wherein an inclination angle of the second surface with respect to the axis is 30 ° or more.

(5) having a hollow portion located in the middle of the core portion or on an extension line;
The optical waveguide according to any one of (1) to (4), wherein an inner peripheral surface of the hollow portion includes the first surface and the second surface.

(6) a core layer in which the core part and a side cladding part adjacent to the core part are formed;
Two clad layers laminated with the core layer in between,
The optical waveguide according to any one of (1) to (5), wherein the clad portion includes the side clad portion and the two clad layers.

  (7) An opto-electric hybrid board comprising the optical waveguide according to any one of (1) to (6) above.

  (8) An electronic apparatus comprising the optical waveguide according to any one of (1) to (6) above.

  According to the present invention, one of the first surface and the second surface can be used as a mirror surface, and unnecessary light reflection and light transmission on the other surface can be prevented or suppressed. Therefore, the transmission characteristics are excellent, and high-quality optical communication can be performed.

It is a perspective view which shows 1st Embodiment of the optical waveguide of this invention. It is a longitudinal cross-sectional view of the optical waveguide shown in FIG. It is a top view of the optical waveguide shown in FIG. It is a typical longitudinal cross-sectional view for demonstrating the 1st surface and 2nd surface which are shown in FIG. It is a top view which shows the modification of the opening part of the cavity part shown in FIG. It is a longitudinal cross-sectional view which shows the modification which provided the reflecting film on the inner wall surface of the cavity part shown in FIG. It is a top view which shows 2nd Embodiment of the optical waveguide of this invention. It is sectional drawing which shows 3rd Embodiment of the optical waveguide of this invention. It is sectional drawing which shows 4th Embodiment of the optical waveguide of this invention. It is sectional drawing which shows 5th Embodiment of the optical waveguide of this invention. It is a figure for demonstrating the method to manufacture the optical waveguide of this invention by the imprint method. It is a longitudinal cross-sectional view which shows embodiment of the opto-electric hybrid board | substrate of this invention.

  Hereinafter, the optical waveguide, the opto-electric hybrid board and the electronic apparatus of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

<Optical waveguide>
<< First Embodiment >>
First, a first embodiment of the optical waveguide of the present invention will be described.

  FIG. 1 is a perspective view showing a first embodiment of the optical waveguide of the present invention, and FIG. 2 is a longitudinal sectional view of the optical waveguide shown in FIG. In the following, for convenience of explanation, the lower side in FIGS. 1 and 2 is referred to as “lower” and the upper side is referred to as “upper”.

  The optical waveguide 1 shown in FIG. 1 has a strip shape or a plate shape, and transmits an optical signal between a light incident portion and a light emitting portion to perform optical communication.

An optical waveguide 1 shown in FIG. 1 includes a laminate 10 in which a clad layer 11, a core layer 13, and a clad layer 12 are laminated in this order from the lower side. In the core layer 13, a long core portion 14 and a side clad portion 15 provided adjacent to the side surface are formed. As described above, the core layer 13 sandwiched between the two clad layers 11 and 12 has the core portion 14 and the side clad portion 15, so that the outer periphery of the core portion 14 is composed of the side clad portion 15 and the clad layers 11 and 12. Therefore, the light can be efficiently confined and propagated in the core portion 14.
The optical waveguide 1 is provided with a cavity 170 that penetrates a part of the laminate 10.

  Although the refractive index of the core part 14 should just be larger than the refractive index of a clad part, it is preferable that the difference is 0.3% or more, and it is more preferable that it is 0.5% or more. On the other hand, the upper limit value is not particularly set, but is preferably about 5.5%. If the difference in refractive index is less than the lower limit value, the effect of propagating light may be reduced. On the other hand, if the difference in refractive index exceeds the upper limit value, further improvement in light transmission efficiency cannot be expected.

  The refractive index difference is expressed by the following equation when the maximum refractive index of the core portion 14 is n4 and the minimum refractive indexes of the side cladding portion 15, the cladding layer 11, and the cladding layer 12 are n5, n1, and n2. Is done.

Refractive index difference (%) = | n4 / n5-1 | × 100
Refractive index difference (%) = | n4 / n1-1 | × 100
Refractive index difference (%) = | n4 / n2-1 | × 100

  Further, the refractive index distribution in the width direction of the core layer 13, that is, the depth direction in FIG. 2 (direction perpendicular to the sheet surface) may be any shape distribution. That is, the refractive index distribution may be a so-called step index (SI) type distribution in which the refractive index changes discontinuously, or a so-called graded index (GI) type distribution in which the refractive index changes continuously. It may be. If the SI type distribution is used, it is easy to form a refractive index distribution. If the GI type distribution is used, the probability that the signal light is collected in a region having a high refractive index is increased, so that the transmission efficiency is improved.

  That is, when the refractive index in the vicinity of the boundary between the core portion 14 and the side cladding portion 15 continuously decreases from the core portion 14 side toward the side cladding portion 15 side, more light propagates through the core portion 14. It can be confined effectively.

  Similarly, the refractive index distribution in the thickness direction of the optical waveguide 1, that is, the vertical direction in FIG. 2, may be the above-described step index distribution or the above-described graded index distribution.

  Further, in FIG. 1, the core portion 14 is linear in a plan view (hereinafter simply referred to as “plan view”) viewed from the layer thickness direction of the laminate 10, but is not limited thereto, and is curved in a plan view. It may also be branched or crossed on the way.

  Further, the cross-sectional shape of the core portion 14 is a quadrangle (rectangular shape) in FIG. 1, but is not limited to this, for example, a circle such as a perfect circle, an ellipse, or an oval, a triangle, a pentagon, a hexagon, or the like. Other polygons may be used. However, since the cross-sectional shape of the core portion 14 is a quadrangle (rectangular shape), there is an advantage that the core portion 14 can be easily formed.

  The width and height (the thickness of the core layer 13) of the core part 14 are not particularly limited, but are preferably about 1 to 200 μm, more preferably about 5 to 100 μm. Thereby, it is possible to increase the density of the core part 14 while increasing the transmission efficiency of the core part 14. That is, since the number of core portions 14 that can be laid per unit area can be increased, large-capacity optical communication can be performed even in a small area.

  The number of core portions 14 formed in the core layer 13 is one for convenience of explanation in FIG. 1, but is not limited to this, and is, for example, 1 to 100.

  The constituent materials (main materials) of the core layer 13 and the cladding layers 11 and 12 as described above are, for example, acrylic ether, methacrylic resin, polycarbonate, polystyrene, cyclic ether resin such as epoxy resin and oxetane resin. , Polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resin, fluorine resin, polyurethane, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, polyester such as PET and PBT, polyethylene succinate, polysulfone, poly Various resin materials such as ethers and cyclic olefin resins such as benzocyclobutene resins and norbornene resins can be used. Note that the resin material may be a composite material in which materials having different compositions are combined. Since these are relatively easy to process, they are suitable as constituent materials for the core layer 13 and the cladding layers 11 and 12 in which the cavity 170 is formed.

  In the optical waveguide 1, the clad layer 11 may be provided as necessary and may be omitted. In that case, the air layer serves as the cladding layer 11.

  As described above, the optical waveguide 1 is provided with the cavity 170 that is removed so that a part of the laminated body 10 penetrates. That is, the optical waveguide 1 includes the laminated body 10 and the cavity 170 formed thereon. The cavity 170 shown in FIG. 1 is located in the middle of the core part 14 in the longitudinal direction. Part of the inner wall surface of the cavity 170 is an inclined surface 171 (first surface) and an inclined surface 172 (second surface) that cross in a direction inclined with respect to the axis A of the core portion 14. Here, the “axis A” is a line (center line) passing through the center of the core part 14 and along the optical axis of the core part 14.

  Further, the cavity 170 has a substantially trapezoidal cross-sectional shape when cut by a virtual plane orthogonal to the upper surface of the cladding layer 12 and including the axis A of the core 14. This trapezoid has a short lower side in FIG. 2 and a long upper side. Further, the inclined surface 171 described above and the inclined surface 172 at a position facing the inclined surface 171 correspond to the hypotenuse of the trapezoid. That is, the inclined surfaces 171 and 172 are arranged in the middle of the core portion 14 along the axis A direction of the core portion 14.

  Of the inner wall surface (inner side surface) of the cavity portion 170, two surfaces substantially parallel to the axis A of the core portion 14 are upright surfaces 173 and 174 that are perpendicular to the lower surface of the cladding layer 11, respectively. (See FIG. 1). The two inclined surfaces 171 and 172 and the two upright surfaces 173 and 174 constitute the inner surface of the cavity 170.

Hereinafter, the inclined surfaces 171 and 172 constituting the mirror surface will be described in detail.
FIG. 3 is a plan view of the optical waveguide shown in FIG. 1, and FIG. 4 is a schematic longitudinal sectional view for explaining the first surface and the second surface shown in FIG. In FIG. 3, for convenience of explanation, the X axis and the Y axis are shown as two axes orthogonal to each other. In the following explanation, the direction parallel to the X axis is “X axis direction” and parallel to the Y axis. The direction is called “Y-axis direction”, the X-axis and Y-axis tip sides indicated by arrows are called “+ (plus)”, and the base end side is called “− (minus)”.

  The inclined surface 171 has light reflectivity and functions as a mirror surface (optical path conversion unit) that converts the optical path of the core unit 14. For example, as shown in FIG. 4, the mirror surface composed of the inclined surface 171 reflects the light L1 propagating from the right side to the left side in FIG. Convert.

  On the other hand, the inclined surface 172 is roughened and has anti-reflection properties. The inclined surface 172 is not used as a mirror surface for converting an optical path like the inclined surface 171 described above.

  Here, the portion on the inclined surface 171 side (+ Y-axis direction side) with respect to the cavity portion 170 of the core portion 14 (hereinafter referred to as “the portion on the inclined surface 171 side of the core portion 14”) is emitted from a light emitting element (not shown). The transmitted regular light L1 is transmitted (that is, used for optical communication), but the portion on the inclined surface 172 side (the −Y axis direction side) with respect to the cavity portion 170 of the core portion 14 (hereinafter referred to as “inclination of the core portion 14”). The portion on the surface 172 side ”is not used for optical communication.

  However, unnecessary light such as external light may enter the core layer 13 and the cladding layers 11 and 12 and propagate even in a portion not used for such optical communication. When such unnecessary light is reflected by the inclined surface 172, the reflected light is received by the light receiving element together with the regular light, and crosstalk occurs. Further, when unnecessary light passes through the inclined surface 172, the transmitted light is reflected by the inclined surface 171 or transmitted through the inclined surface 171 and incident on the inclined surface 171 side of the core portion 14, causing crosstalk. It can be a cause.

  Therefore, the inclined surfaces 171 and 172 have different surface roughness. Specifically, the surface roughness of the inclined surface 172 is larger than the surface roughness of the inclined surface 172. As a result, the optical path is converted using the inclined surface 171 and unnecessary reflection and transmission of light on the inclined surface 172 can be prevented or suppressed.

  For example, when light propagating through the inclined surface 171 side of the core portion 14 is reflected by the inclined surface 171 and received by the light receiving element, the light propagates through the inclined surface 172 side portion of the core portion 14 as shown in FIG. It is possible to prevent or suppress unnecessary light L2 (for example, external light) to be reflected on the inclined surface 172, and to diffuse the reflected light even if it is reflected on the inclined surface 172. Therefore, it is possible to prevent or suppress unnecessary light from being received by the light receiving element. Further, unnecessary light L <b> 2 propagating through the inclined surface 172 side of the core portion 14 is prevented or suppressed from being transmitted through the inclined surface 172, and the transmitted light can be diffused even though the inclined surface 172 is transmitted. it can. Therefore, unnecessary light can be prevented or suppressed from causing crosstalk.

  Here, the inclined surface 171 is inclined with respect to the axis A with an inclination angle θ1, and the inclined surface 172 is inclined with respect to the axis A with an inclination angle θ2. Further, the inclined surface 171 and the inclined surface 172 are inclined in directions opposite to each other with respect to the axis A. When the inclined surfaces 171 and 172 are inclined as described above, when the light propagating through the portion on the inclined surface 171 side of the core portion 14 is reflected by the inclined surface 171 and received by the light receiving element, the inclined surface of the core portion 14 Unnecessary light propagating through the portion on the 172 side is easily reflected by the inclined surface 172 and incident on the light receiving element. Therefore, the effect by applying this invention becomes remarkable. Here, θ1 and θ2 refer to inclination angles with respect to the axis A when viewed in the cross section shown in FIG. The inclination angles θ1 and θ2 can be measured by using the JPCA standard “Measurement method for optical wiring board dimensions using an optical waveguide (JPCA-PE02-05-02S)” issued by the Japan Electronic Circuits Association. it can.

  In addition, the inclination angle θ1 with respect to the axis A of the inclined surface 171 is appropriately set according to the position of the coupling destination of the optical path converted by the inclined surface 171, but is preferably set to about 30 to 60 °, more preferably 35. It is set to about ~ 50 °. By setting the inclination angle θ1 within the above range, it is possible to efficiently convert the optical path of the core portion 14 on the inclined surface 171, and to suppress the loss accompanying the optical path conversion.

  Moreover, the inclination angle θ2 with respect to the axis A of the inclined surface 172 may be the same or different, but is preferably 40 ° or more, more preferably about 40 to 60 °, and more preferably 40 to 50 More preferably, it is about °. Thereby, formation of the cavity part 170 becomes easy. Further, in the case of such a range of the inclination angle θ2, unnecessary light propagating through the portion on the inclined surface 172 side of the core portion 14 is easily reflected by the inclined surface 172 and incident on the light receiving element. Therefore, in such a case, the effect of the present invention becomes remarkable.

  Further, the surface roughness SRa of the inclined surface 171 is sufficient as long as the inclined surface 171 can exhibit light reflectivity, but is preferably smaller than 0.15 μm, more preferably 0.01 μm or more and 0.1 μm or less. More preferably, it is 0.02 μm or more and 0.08 μm or less. Thereby, the inclined surface 171 can be used as a mirror surface excellent in light reflectivity.

  Further, the surface roughness SRa of the inclined surface 172 is sufficient as long as the inclined surface 172 can exhibit the antireflection property, but is preferably 0.15 μm or more, more preferably 0.2 μm or more and 5 μm or less. More preferably, it is 4 μm or more and 1 μm or less. Thereby, the formation of the inclined surface 172 can be facilitated, and the light reflection preventing property of the inclined surface 172 can be improved.

  The surface roughness SRa is defined by placing an orthogonal coordinate axis (X axis, Y axis) on the center plane of a portion extracted from the curved surface represented by the surface roughness data by a reference area, and setting the axis orthogonal to the center plane to Z It is a center plane average roughness expressed by an axis and displayed in units of μm in a value given by a predetermined formula.

  Here, in the present embodiment, as shown in FIGS. 1 and 3, the inclined surface 171 is a region that crosses the cladding layers 11 and 12, and a region that crosses the core layer 13. It is constituted by a certain core layer region 141, and has an inclined surface 172 in the same region. In the present embodiment, all the regions of the inclined surface 172 are roughened as described above. Thereby, it is possible to prevent unnecessary light (for example, external light or clad mode light) propagating through the clad layers 11 and 12 and the side clad portion 15 from being reflected by the inclined surface 172. The inclined surface 172 has unnecessary light propagating through the portion on the inclined surface 172 side of the core portion 14 as described above (for example, if at least the region crossing the core portion 14 is roughened as described above) It is possible to prevent or suppress external light) from being reflected by the inclined surface 172.

  In the present embodiment, each of the inclined surfaces 171 and 172 is a flat surface, but may have a concave or convex curved portion.

  A method for forming such inclined surfaces 171 and 172 is not particularly limited, and for example, known processing techniques such as laser processing, etching, and imprinting can be used. Since the inclined surfaces 171 and 172 are configured by a part of the inner wall surface (inner peripheral surface) of the cavity portion 170 located in the middle of the core portion 14 as described above, laser processing, etching, imprint, and the like are known. By forming the cavity 170 using this processing technique, it can be formed relatively easily and with high accuracy.

  Further, when the inclined surface 171 is formed by the imprint method, the inclined surface 171 having the core part region 141a and the side clad part region 141b having different surface roughness as described above can be formed easily and with high accuracy.

  In the case where the inclined surfaces 171 and 172 are formed by the imprint method, an imprint mold having a first forming surface for forming the inclined surface 171 and a second forming surface for forming the inclined surface 172 will be described in detail later. It may be used (see FIG. 10). In this case, the surface roughness of the second molding surface may be made larger than the surface roughness of the first molding surface.

  Even when the inclined surface 171 is formed by laser processing, the inclined surfaces 171 and 172 having different surface roughness as described above can be formed by appropriately adjusting the laser processing conditions.

  The inclined surface 172 may be roughened by another process after laser processing or imprint processing for forming the cavity 170.

(Modification)
Hereinafter, a modification of the cavity 170 shown in FIG. 1 or its peripheral part will be described. In addition, about the matter similar to the structure mentioned above about the following modification, the description is abbreviate | omitted.

FIG. 5 is a plan view showing a modification of the opening of the cavity shown in FIG.
The shape of the opening of the cavity 170 may be a rectangular shape as shown in FIGS. 1 and 3, or may be an oval like an opening 175 shown in FIG. 5. The optical waveguide 1 shown in FIG. 5 is the same as the optical waveguide 1 shown in FIG. 1 except for the following points.

  The opening 175 includes inclined surface upper ends 171a and 172a made of straight line segments corresponding to the two inclined surfaces 171 and 172 described above, and upright surface upper ends 173a and 174a made of arcs corresponding to the two upright surfaces 173 and 174, respectively. Constructed, oval. Thereby, when stress accompanying structural change or thermal change occurs in the vicinity of the cavity 170, it is difficult for the stress to concentrate in the vicinity of the cavity 170. As a result, a reduction in transmission efficiency of the optical waveguide 1 and a reduction in reflection efficiency on the inclined surface 171 can be further suppressed, and the optical waveguide 1 capable of performing high-quality optical communication is obtained.

  On the other hand, when the lower surface of the core layer 13 is used as a reference surface, the angle (acute angle side) formed by the reference surface and the upright surfaces 173 and 174 is preferably about 60 to 90 °, respectively. In each figure, it is illustrated as approximately 90 °. Since the space occupied by such a cavity 170 is minimized, when the plurality of cavities 170 are formed adjacent to each other, the interval between them can be minimized. Therefore, keeping the angle formed by the reference surface and the upright surfaces 173 and 174 within the above range is useful in that the hollow portions 170 can be arranged at a high density even with respect to the core portions 14 provided at a narrow pitch. It is. Further, by keeping the angle formed by the reference surface and the upright surfaces 173 and 174 within the above range, stress concentration due to the difference in physical properties of the materials constituting each layer in the vicinity of the upright surfaces 173 and 174 can be particularly suppressed. As a result, delamination is particularly difficult to occur, so that the reliability of the optical waveguide 1 can be particularly improved.

  The maximum depth of the cavity 170 is appropriately set from the thickness of the laminated body 10 and is not particularly limited. However, from the viewpoint of the mechanical strength and flexibility of the optical waveguide 1, it is preferably 1 to 1. The thickness is about 500 μm, more preferably about 5 to 400 μm.

  The maximum length of the cavity 170, that is, the maximum length in the Y direction of the cavity 170 in FIG. 5 is not particularly limited, but the thickness of the cladding layers 11 and 12 and the core layer 13 and the inclination angle of the inclined surface 171 Therefore, the thickness is preferably about 2 to 1200 μm, more preferably about 10 to 1000 μm.

  Further, the maximum width of the cavity portion 170, that is, the maximum length in the X direction of the cavity portion 170 in FIG. 5 is not particularly limited and is appropriately set according to the width of the core portion 14 and the like, but preferably 20 to 3000 μm. More preferably about 40 to 2000 μm.

  One hollow portion 170 may be provided for one core portion 14, but one hollow portion 170 is provided so as to straddle the plurality of core portions 14. Also good.

  Moreover, when forming the some cavity part 170, those formation positions may mutually be the position mutually shifted in the Y direction.

6 is a longitudinal sectional view showing a modification in which a reflective film is provided on the inner wall surface of the cavity shown in FIG.
The optical waveguide 1 shown in FIG. 6 is the same as the optical waveguide 1 shown in FIG. 1 except that a reflective film 176 is provided on the inner wall surface of the cavity 170.

  By providing such a reflective film 176, the reflection characteristics on the inclined surface 171 can be particularly enhanced. Examples of the reflective film 176 include a metal film, a carbon film, a resin film, a ceramic film, and a silicon film. Among these, a metal film is preferably used. According to the metal film, the reflection film 176 having a high reflectance due to the gloss peculiar to the metal can be obtained. Examples of the constituent material of the metal film include aluminum, iron, chromium, nickel, copper, zinc, silver, platinum, gold, lead and the like.

  The average thickness of the reflective film 176 is not particularly limited, but is preferably about 0.1 to 500 μm, and more preferably about 0.5 to 300 μm. As a result, a reflective film that has sufficient reflectivity and is difficult to peel off can be obtained. Note that the reflective film 176 may be provided at least on the core portion 14 and may not be provided on the clad layer regions 111 and 121 and the side clad portion 15.

  Examples of the method for forming the reflective film 176 include a vacuum deposition method, a physical vapor deposition method such as a sputtering method, a chemical vapor deposition method such as a CVD method, a plating method, a thermal transfer method, a metal foil transfer method, a printing method, and a coating method. Etc. Note that the reflective film 176 is preferably formed after the roughening of the inclined surface 172 described above.

<< Second Embodiment >>
Next, a second embodiment of the optical waveguide of the present invention will be described.
FIG. 7 is a plan view showing a second embodiment of the optical waveguide of the present invention.

  Hereinafter, although 2nd Embodiment is described, in the following description, difference with 1st Embodiment is demonstrated and the description is abbreviate | omitted about the same matter.

  The optical waveguide 1 according to the second embodiment shown in FIG. 7 is the same as the optical waveguide 1 according to the first embodiment except that the formation position of the cavity 170 is different.

That is, the cavity 170 shown in FIG. 7 is formed in the side cladding 15 on the extension line of the core 14. In forming the cavity 170, the cladding layer 12, the core layer 13, and the cladding layer 11 are processed. Of these, the processing position of the core layer 13 is only the constituent material of the side cladding portion 15. Since the portion is configured, the processing conditions such as the processing rate are substantially equal during the processing. As a result, the core layer 13 can be processed with high processing accuracy, and the dimensional accuracy of the cavity 170 to be formed can be particularly increased. Therefore, according to the present embodiment, it is possible to obtain the optical waveguide 1 that includes the cavity portion 170 with high dimensional accuracy, has high reflection efficiency on the inclined surface 171, and can perform high-quality optical communication.
In such a second embodiment, the same operations and effects as in the first embodiment can be obtained.

«Third embodiment»
Next, a third embodiment of the optical waveguide of the present invention will be described.
FIG. 8 is a cross-sectional view showing a third embodiment of the optical waveguide of the present invention.

  Hereinafter, the third embodiment will be described. In the following description, differences from the first embodiment will be described, and description of similar matters will be omitted.

The optical waveguide 1 shown in FIG. 8 includes a flat upright surface 172 ′ that is substantially orthogonal to the axis A in place of the inclined surface 172 in the optical waveguide 1 shown in FIG. The optical waveguide 1 according to the present embodiment is the same as the optical waveguide 1 according to the first embodiment, except for this point.
In such a third embodiment, the same operation and effect as in the first embodiment can be obtained.

<< Fourth Embodiment >>
Next, a fourth embodiment of the optical waveguide of the present invention will be described.
FIG. 9 is a cross-sectional view showing a fourth embodiment of the optical waveguide of the present invention.

  Hereinafter, although 4th Embodiment is described, in the following description, a difference with 1st Embodiment is demonstrated and the description is abbreviate | omitted about the same matter.

  The optical waveguide 1 shown in FIG. 9 further includes the support film 2 laminated on the lower surface of the clad layer 11 and the cover film 3 laminated on the upper surface of the clad layer 12, except for the first embodiment. This is the same as the optical waveguide 1.

The cavity 170 is configured to penetrate the cover film 3. Therefore, the inclined surface 171 is a surface formed continuously from the cover film 3 through the cladding layer 12 and the core layer 13 to the middle of the cladding layer 11.
In such a fourth embodiment, the same operations and effects as in the first embodiment can be obtained.

  Moreover, by using the support film 2 and the cover film 3, the laminated body 10 can be protected from external force, foreign matter adhesion, contamination, and the like.

«Fifth embodiment»
Next, a fifth embodiment of the optical waveguide of the present invention will be described.
FIG. 10 is a cross-sectional view showing a fifth embodiment of the optical waveguide of the present invention.

  Hereinafter, the fifth embodiment will be described. In the following description, differences from the first embodiment will be described, and description of similar matters will be omitted.

  The inclined surface 172 of the optical waveguide 1 shown in FIG. 10 is inclined in the same direction as the inclined surface 171. The optical waveguide 1 according to the present embodiment is the same as the optical waveguide 1 according to the first embodiment, except for this point.

  Even if such an inclined surface 172 inclined to the same direction as the inclined surface 171 reflects unnecessary light L2, the reflection direction of the inclined surface 171 is opposite to the direction in which the inclined surface 171 reflects the regular light L1. Can be direction.

  Therefore, in this embodiment, even if the inclined surface 172 is not roughened, the problem of crosstalk due to the light L2 being reflected by the inclined surface 172 usually does not occur. However, if the inclined surface 172 is not roughened, for example, when part of the light L2 passes through the inclined surface 172, most of the transmitted light reaches the inclined surface 171 and is reflected by the inclined surface 171. Or may be transmitted through the inclined surface 171 and incident on the inclined surface 171 side of the core portion 14 to deteriorate the characteristics.

  Therefore, in the present embodiment, the inclined surface 172 that is inclined in the same direction as the inclined surface 171 is roughened. Thereby, it is possible to prevent or suppress the light L2 from passing through the inclined surface 172, or to diffuse the transmitted light even if the light L2 passes through the inclined surface 172. As a result, it is possible to prevent the deterioration of characteristics as described above.

  In FIG. 10, the inclined surfaces 171 and 172 are formed so as to be parallel to each other, but the inclined surfaces 171 and 172 do not have to be parallel.

<Optical waveguide manufacturing method>
Next, an example of a method for producing the optical waveguide of the present invention will be described. Hereinafter, a case where the optical waveguide 1 shown in FIG. 2 is manufactured will be described as an example.

  The optical waveguide 1 shown in FIG. 2 can be manufactured by a method including a step of sequentially laminating the clad layer 11, the core layer 13, and the clad layer 12 to obtain the laminate 10, and a step of forming the cavity 170. it can.

Hereinafter, each process will be described sequentially.
[1] First, (a) a composition for forming the cladding layer 11, a composition for forming the core layer 13, and a composition for forming the cladding layer 12 are sequentially formed and manufactured. Method, (b) a method of laminating the clad layer 11, the core layer 13 and the clad layer 12 by using each composition, and then laminating, and (c) producing a laminate by simultaneously extruding three kinds of compositions. By such a method, a core layer forming layer or a multilayer structure including the core layer forming layer is obtained.

  At this time, if the composition for forming the core layer 13 has a refractive index modulation ability whose refractive index changes upon exposure, a desired pattern can be obtained only by performing an exposure process on the core layer forming layer. As a result, the core layer 13 including the core portion 14 laid can be obtained.

  In addition, the manufacturing method of the core layer 13 is not limited to such a method. For example, the core layer 13 including the core portion 14 laid in a desired pattern can be obtained by repeatedly performing a film forming process and a patterning process in which a photolithography technique and an etching technique are combined.

  [2] Next, the cavity 170 is formed. Thereby, the optical waveguide 1 is obtained. There are various methods for forming the cavity 170. For example, a laser processing method, an electron beam processing method, an imprint method, etc. other than machining methods, such as cutting and grinding, are mentioned. Among these, according to the laser processing method or the imprint method, the cavity 170 with high dimensional accuracy can be formed relatively easily. Hereinafter, a method for forming the cavity 170 by the imprint method will be described.

  FIG. 11 is a diagram for explaining a method of manufacturing the optical waveguide of the present invention by the imprint method.

  First, as shown in FIG. 11 (a), the laminate 10 obtained as described above is prepared.

  Next, as shown in FIG. 11B, the imprint mold 900 is pressed against the laminate 10 so that the portions having the molding surfaces 901 and 902 of the imprint mold 900 are buried in the laminate 10. At this time, heat treatment may be performed as necessary.

  Here, the imprint mold 900 has an outer shape that matches the inner wall surface of the cavity 170. That is, the imprint mold 900 has molding surfaces 901 and 902 for molding the inclined surfaces 171 and 172.

The molding surface 901 is a first molding surface that molds the inclined surface 171, and the molding surface 902 is a second molding surface that molds the inclined surface 172. The molding surface 902 is roughened and has a larger surface roughness than the molding surface 901.
Such molding surfaces 901 and 902 are subjected to mold release treatment as necessary.

  Thereafter, the imprint mold 900 is released from the laminate 10 to obtain the optical waveguide 1 as shown in FIG.

  According to the manufacturing method of the optical waveguide 1 using such an imprint mold 900, the inclined surface 171 as described above can be formed easily and with high accuracy.

<Opto-electric hybrid board>
Next, an embodiment of the opto-electric hybrid board according to the present invention will be described.
FIG. 12 is a longitudinal sectional view showing an embodiment of the opto-electric hybrid board of the present invention.

  An opto-electric hybrid board 100 shown in FIG. 12 includes an optical waveguide 1 (optical waveguide of the present invention), an electric wiring board 5 laminated on the upper surface thereof, and an adhesive sheet 9 that is interposed between them to bond them together. ,have.

  The electrical wiring board 5 shown in FIG. 12 has a multilayer board 50 having a core board 51 and a buildup layer 52 laminated on both sides thereof, and a through hole 53 provided on the lower surface of the multilayer board 50. doing.

  The core substrate 51 is a substrate that supports the electrical wiring substrate 5, and examples of the constituent material thereof include various resin materials. In addition, paper, glass cloth, resin film, etc. as a base material, and the base material impregnated with a resin material, specifically, glass cloth / epoxy copper clad laminate, glass nonwoven fabric / epoxy copper clad laminate In addition to insulating substrates used in composite copper-clad laminates such as heat-resistant and thermoplastic organic rigid substrates such as polyetherimide resin substrates, polyetherketone resin substrates, polysulfone resin substrates, alumina substrates, and nitriding It may be a ceramic rigid substrate such as an aluminum substrate or a silicon carbide substrate.

  Each of the conductor layer 522 and the through wiring is made of a conductive material such as a simple metal such as copper, aluminum, nickel, chromium, zinc, tin, gold, silver, or an alloy containing these metal elements. .

  The insulating layer 521 is made of a silicon compound such as silicon oxide or silicon nitride, a resin material such as a polyimide resin or an epoxy resin, or the like.

  In this way, an electrical circuit that extends not only in the plane direction but also in the thickness direction can be constructed in the buildup layer 52, and the density of the electrical circuit can be increased.

  In addition, although such a multilayer substrate 50 may be formed by what kind of construction method, it is formed by various buildup construction methods, such as an additive method, a semi-additive method, and a subtractive method, as an example.

  The electrical wiring board provided in the opto-electric hybrid board of the present invention is not limited to the one including the multilayer board such as the electrical wiring board 5 described above. For example, the multilayer board is a single-layer electrical wiring board (rigid board). It may be replaced, or may be replaced with various flexible substrates such as a polyimide substrate, a polyester substrate, and an aramid film substrate. The multilayer substrate 50 can be replaced with a coreless multilayer substrate that does not include the core substrate 51.

  12 has a solder resist layer 54 provided on the upper surface of the multilayer substrate 50. The electrical wiring substrate 5 shown in FIG. By providing the solder resist layer 54, the conductor layer 522 of the electrical wiring board 5 is protected from oxidation, corrosion, and the like.

  Note that an electrical element (not shown) may be mounted on the electrical wiring board 5. Examples of the electric element include IC, LSI, RAM, ROM, capacitor, coil, resistor, and diode.

  Also, the opto-electric hybrid board 100 shown in FIG.

  The optical element 6 shown in FIG. 12 has an element body 60, a light emitting / receiving unit 61 and a terminal 62 provided on the lower surface of the element body 60, and a bump 63 provided so as to protrude downward from the terminal 62. ing. The light emitting / receiving unit refers to a light receiving unit, a light emitting unit, or a unit having both functions.

  The optical element 6 is arranged such that the optical axis of the light emitting / receiving unit 61 coincides with the optical axis of the core unit 14 via the inclined surface 171 (mirror) of the cavity 170 of the optical waveguide 1. Thereby, the optical waveguide 1 and the optical element 6 are optically connected, and the optical signal propagating through the optical waveguide 1 is received by the optical element 6, or the optical signal emitted from the optical element 6 is incident on the optical waveguide 1. You can do it.

  Examples of the optical element 6 include a light emitting element such as a surface emitting laser (VCSEL), a light emitting diode (LED), and an organic EL element, and a light receiving element such as a photodiode (PD, APD).

<Electronic equipment>
The optical waveguide according to the present invention as described above has high transmission efficiency and excellent optical coupling efficiency with other optical components. For this reason, by providing the optical waveguide of the present invention, a highly reliable electronic device (electronic device of the present invention) capable of performing high-quality optical communication can be obtained.

  Examples of the electronic device including the optical waveguide of the present invention include electronic devices such as a mobile phone, a game machine, a router device, a WDM device, a personal computer, a television, and a home server. In any of these electronic devices, it is necessary to transmit a large amount of data at high speed between an arithmetic device such as an LSI and a storage device such as a RAM. Therefore, since such an electronic device includes the optical waveguide of the present invention, problems such as noise and signal degradation peculiar to electric wiring are eliminated, and a dramatic improvement in performance can be expected. This can contribute to cost reduction.

  In addition, the amount of heat generated in the optical waveguide portion is greatly reduced compared to electrical wiring. For this reason, the electric power required for cooling can be reduced and the power consumption of the whole electronic device can be reduced.

  The optical waveguide, the opto-electric hybrid board, and the electronic device of the present invention have been described above. However, the present invention is not limited to this, and for example, an arbitrary component may be added to the optical waveguide.

  In addition, when the inclined surface 171 is used as a light incident side mirror, the light emitting side may emit light from the end surface of the core portion 14 along the optical axis of the core portion 14. May be equipped with a connector. On the other hand, when the inclined surface 171 is used as a light output side mirror, the light incident side may make light incident along the optical axis of the core portion 14 from the end surface of the core portion 14. At that time, a connector may be attached to the incident end.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 2 Support film 3 Cover film 5 Electric wiring board 50 Multilayer board 51 Core board 52 Build-up layer 521 Insulating layer 522 Conductor layer 53 Through-hole 54 Solder resist layer 6 Optical element 60 Element main body 61 Light emitting / receiving part 62 Terminal 63 Bump DESCRIPTION OF SYMBOLS 10 Laminate 11 Cladding layer 12 Cladding layer 13 Core layer 14 Core part 15 Side surface clad part 9 Adhesive sheet 100 Opto-electric hybrid board 111, 121 Cladding layer area 141 Core layer area 170 Cavity 171 Inclined surface (mirror surface)
171a, 172a Inclined surface upper end 172 Inclined surface 172 ′ Upright surface 173, 174 Upright surface 173a, 174a Upright surface upper end 175 Opening portion 176 Reflective film 900 Imprint mold 901 Molding surface 902 Molding surface A Axis θ1 Tilt angle θ2 Tilt angle L1 , L2 light

Claims (8)

The core,
A cladding portion adjacent to the core portion;
A first surface and a second surface arranged in the middle of the core portion or on an extension line along the axial direction of the core portion;
The optical waveguide, wherein the first surface and the second surface have different surface roughness. The first surface is a mirror surface inclined with respect to the axis;
The optical waveguide according to claim 1, wherein the second surface has a surface roughness larger than that of the first surface.   The optical waveguide according to claim 2, wherein the first surface and the second surface are inclined in directions opposite to each other with respect to the axis.   The optical waveguide according to claim 3, wherein an inclination angle of the second surface with respect to the axis is 30 ° or more. It has a hollow portion located in the middle of the core portion or on an extension line,
The optical waveguide according to any one of claims 1 to 4, wherein an inner peripheral surface of the hollow portion includes the first surface and the second surface. A core layer in which the core part and a side cladding part adjacent to the core part are formed;
Two clad layers laminated with the core layer in between,
6. The optical waveguide according to claim 1, wherein the clad part includes the side clad part and the two clad layers. 7.   An opto-electric hybrid board comprising the optical waveguide according to claim 1. An electronic apparatus comprising the optical waveguide according to claim 1.

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