JP2014002218A - Optical waveguide and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide with high S/N ratio in which a crosstalk is suppressed, and a highly reliable electronic apparatus provided with the optical waveguide.SOLUTION: An optical waveguide 1 is plate-shaped and includes: four core parts for signal transmission 141 provided in parallel and used for the transmission of optical signals; core parts for evaluation 143 provided between each of the two core parts for signal transmission 141 being in parallel with the core parts for signal transmission 141 and used for the evaluation of transmission characteristics; core parts for dummy 142 provided between each of the two core parts for signal transmission 141 being in parallel with the core parts for signal transmission 141 and not used for the transmission of optical signals; and side face clad parts 15 placed side by side with each of the core parts 141, 142 and 143 respectively, and having a refractive index lower than those of the core parts. Also, recessed parts 170 are formed at the optical waveguide 1, and regions which traverse the core parts for signal transmission 141, among the inner faces of the recessed parts 170, are made to be mirrors (optical path conversion parts) 17 which convert the optical path of the core parts for signal transmission 141.

Description

  The present invention relates to an optical waveguide and an electronic device.

  An optical communication technique for transferring data using an optical carrier wave has been developed. In recent years, an optical waveguide has been widely used as a means for guiding the optical carrier wave 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 the light of the optical carrier wave, 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 transmitted (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.

  For example, Patent Document 1 proposes a signal processing board in which an optical waveguide including a plurality of core portions and a light emitting element and a light receiving element respectively provided corresponding to each core portion are arranged. Has been.

  In such a signal processing board, while the amount of signals used for processing is increasing, the demand for downsizing of the signal processing board is also increasing. For this reason, the effort which suppresses enlargement is calculated | required simultaneously, aiming at increase of the signal processing capacity | capacitance of a signal processing board | substrate. Specifically, the signal processing capacity can be increased by forming many core portions in the optical waveguide and increasing the density of the optical waveguide.

  As the number of core portions formed in the optical waveguide increases, the interval between the core portions decreases. However, when the interval between the core portions is narrowed, the signal light leaking from the core portions crosses the clad portion and interferes with the adjacent core portions, thereby reducing the S / N ratio of optical communication (crosstalk). ) Becomes obvious.

JP 2009-139412 A

  An object of the present invention is to provide an optical waveguide having a high S / N ratio in which crosstalk is suppressed and a highly reliable electronic device including the optical waveguide.

Such an object is achieved by the present inventions (1) to (13) below.
(1) An optical waveguide having a flat plate shape,
Two signal transmission core units provided in parallel and used for transmitting optical signals;
An evaluation core unit provided in parallel with the signal transmission core unit between the two signal transmission core units and used for evaluation of transmission characteristics;
A dummy core portion that is provided in parallel with the signal transmission core portion between the two signal transmission core portions and is not used for transmission of an optical signal;
An optical waveguide comprising: a signal transmission core portion, an evaluation core portion, and a dummy core portion adjacent to each other and a side cladding portion having a lower refractive index than these core portions.

  (2) The optical waveguide according to (1), wherein the dummy core section is provided between the signal transmission core section and the evaluation core section.

  (3) The optical waveguide according to (1) or (2), wherein a width of the dummy core portion is narrower than a width of the signal transmission core portion and the evaluation core portion adjacent to the dummy core portion. .

  (4) The width of the side cladding portion is smaller than the width of the signal transmission core portion, the evaluation core portion, and the dummy core portion adjacent to the side cladding portion. The optical waveguide according to any one of the above.

  (5) The optical waveguide according to any one of (1) to (4), wherein a width of the evaluation core portion is equal to a width of the signal transmission core portion adjacent to the evaluation core portion.

  (6) Further, the signal transmission core unit according to any one of (1) to (5) further including an optical path conversion unit that is provided in the middle of the signal transmission core unit or on an extension line and converts an optical path of the signal transmission core unit. Optical waveguide.

(7) The dummy core part is provided on both sides via the signal transmission core part,
The optical waveguide according to (6), wherein the dummy core section adjacent to the signal transmission core section provided with the optical path conversion section is configured to be interrupted in the vicinity of the optical path conversion section.

  (8) The optical waveguide according to (6) or (7), wherein the evaluation core portion is configured to be exposed on an end face of the optical waveguide.

(9) An optical waveguide having a flat plate shape,
Two signal transmission core units provided in parallel and used for transmitting optical signals;
A plurality of dummy core portions that are provided in parallel with the signal transmission core portion between the two signal transmission core portions and are not used for transmission of optical signals;
An optical waveguide comprising: a side clad portion provided adjacent to each of the signal transmission core portion and the dummy core portion and having a lower refractive index than the core portions.

  (10) The optical waveguide according to any one of (1) to (9), wherein a width of the side clad portion is 5 to 50 μm.

  (11) The optical waveguide according to any one of (1) to (10), wherein all of the widths of the side clad portions located between the two signal transmission core portions are uniform.

  (12) The optical waveguide performs a maskless exposure process on the base material, generates a refractive index difference between the exposed area and the non-exposed area, The optical waveguide according to any one of the above (1) to (11), wherein a region on the refractive index side is the core portion, and a region on the low refractive index side is the side cladding portion.

  (13) An electronic apparatus comprising the optical waveguide according to any one of (1) to (12).

  According to the present invention, by arranging at least one of the dummy core portion and the evaluation core portion between the two signal transmission core portions, crosstalk between the two signal transmission core portions is reduced. Therefore, an optical waveguide having a high S / N ratio can be obtained.

  In addition, according to the present invention, a highly reliable electronic device can be obtained by providing the optical waveguide.

It is a top view which shows the core layer of embodiment of the optical waveguide of this invention. It is a perspective view which shows a part among embodiment of the optical waveguide of this invention. It is a longitudinal cross-sectional view which shows embodiment of the optical waveguide of this invention. It is a top view which shows the other structural example of the core layer of embodiment of the optical waveguide of this invention. 6 is a plan view showing a core layer of an optical waveguide obtained in Example 2. FIG.

  Hereinafter, the optical waveguide and the electronic device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

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

  FIG. 1 is a plan view showing a core layer of an embodiment of the optical waveguide of the present invention, FIG. 2 is a perspective view showing a part of the embodiment of the optical waveguide of the present invention, and FIG. It is a longitudinal cross-sectional view which shows embodiment of a waveguide.

  An optical waveguide 1 shown in FIG. 2 is a member having a belt shape and capable of transmitting an optical signal, and is formed by laminating a cladding layer 11, a core layer 13, and a cladding layer 12 in this order from below.

  Further, the core layer 13 shown in FIG. 1 includes four signal transmission core portions 141 provided in parallel in a plan view and the signal transmission core portion 141 between each of the two signal transmission core portions 141. Are provided in parallel with each other, and are provided in parallel with the signal transmission core 141 between each of the two dummy cores 142 that are not used for optical signal transmission and each of the two signal transmission cores 141, And an evaluation core unit 143 used for evaluating transmission characteristics. Further, the core layer 13 is provided adjacent to the signal transmission core unit 141, the dummy core unit 142, and the evaluation core unit 143 (that is, between the core units 141, 142, and 143 in the core layer 13). The side clad portion 15 having a lower refractive index than the core portions 141, 142, and 143 is also provided. Further, as shown in FIG. 3, the optical waveguide 1 is formed with a concave portion 170 opened on the upper surface of the cladding layer 12, and a region crossing the signal transmission core portion 141 on the inner surface of the concave portion 170 is It is a mirror (optical path conversion unit) 17 that converts the optical path of the signal transmission core unit 141.

  In addition, “parallel” in the present specification refers to a state in which, for example, two core portions are not in contact with each other and extend in substantially the same direction.

  As described above, the optical waveguide 1 shown in FIG. 1 includes four signal transmission core portions 141, a total of six dummy core portions 142 provided therebetween, and a total of three evaluation core portions. 143. Among these, signal light is incident on the signal transmission core portion 141, and optical communication is performed by receiving the emitted light. On the other hand, the dummy core part 142 is a core part that is not used for transmission of optical signals, and the evaluation core part 143 is a core part that is used for evaluation of transmission characteristics.

  The side cladding 15 is provided adjacent to each of the cores 141, 142, and 143.

  By providing such a dummy core portion 142 and an evaluation core portion 143 between the two signal transmission core portions 141, the signal light leaking from the signal transmission core portion 141 is transferred to the dummy core portion 141. 142 and the evaluation core portion 143 are prevented from leaking and the leaked signal light traverses the side cladding portion 15. As a result, the leaked signal light is less likely to be mixed in the adjacent signal transmission cores 141 (crosstalk is suppressed), and a decrease in the S / N ratio of optical communication in the signal transmission cores 141 is suppressed. The

Hereinafter, the configuration of each part of the optical waveguide 1 will be sequentially described.
(Core layer)
As described above, the core layer 13 shown in FIGS. 1 and 2 is formed with the signal transmission core part 141, the dummy core part 142, the evaluation core part 143, and the side cladding part 15. Thereby, each core part 141, 142, 143 is each surrounded by a clad part (side clad part 15 and each clad layer 11, 12). As a result, the signal light is confined in each of the core portions 141, 142, and 143, and the signal light can be propagated.

  The refractive index of the signal transmission core portion 141 may be larger than the refractive index of the cladding portion, but the difference is preferably 0.3% or more, and more preferably 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.

  Further, the refractive index of the dummy core 142 may be larger than the refractive index of the cladding, and the difference is preferably in the above range. Thereby, the dummy core part 142 can reliably confine the signal light leaking from the signal transmission core part 141, and contributes to the suppression of crosstalk.

  Further, the refractive index of the evaluation core portion 143 may be larger than the refractive index of the cladding portion, and the difference is preferably in the above range, and more preferably equal to the refractive index of the signal transmission core portion 141. Thereby, based on the evaluation result of the evaluation core unit 143, the transmission characteristics of the signal transmission core unit 141 can be more accurately evaluated.

The difference in refractive index is expressed by the following equation, where A is the refractive index of each of the core parts 141, 142, and 143, and B is the refractive index of the cladding part.
Refractive index difference (%) = | A / B-1 | × 100

  Further, the refractive index distribution in the cross section of each of the core portions 141, 142, 143 may be any shape distribution. This 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. 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 transmission efficiency is improved.

  Moreover, each core part 141, 142, 143 may be linear shape or curved shape by planar view.

  In addition, the core portions 142 and 143 may be provided in parallel with the signal transmission core portion 141 in a part of the optical waveguide 1 and may be omitted in other parts of the optical waveguide 1. Good. Note that the two signal transmission core portions 141 in such a region may cross each other or branch.

  In addition, the cross-sectional shape of each core part 141, 142, 143 is not specifically limited, For example, even if it is circular, such as a perfect circle, an ellipse, and an ellipse, and polygons, such as a triangle, a rectangle, a pentagon, and a hexagon, Although it is good, there exists an advantage which is easy to form each core part 141, 142, 143 by being square (rectangular shape).

  Signal light is incident on the signal transmission core unit 141 formed in the core layer 13 shown in FIG. 1, thereby performing optical communication.

  On the other hand, no signal light is incident on the dummy core part 142, and the signal light leaking from the signal transmission core part 141 to the side cladding part 15 is confined, so that it leaks again to the side cladding part 15. It is suppressed. As a result, crosstalk that occurs between the two signal transmission cores 141 can be suppressed.

  In addition, light for evaluating transmission characteristics is incident on the evaluation core unit 143, and the transmission efficiency and the like can be measured by measuring the intensity and the like of the emitted light. Thereby, the transmission characteristic of the signal transmission core 141 adjacent to the evaluation core 143 can be indirectly evaluated.

  Note that the evaluation core unit 143 has the same function as the dummy core unit 142 described above in addition to such an evaluation function. Therefore, as shown in FIG. 1, by providing one evaluation core part 143 between each two dummy core parts 142, the same cross as in the case of providing three dummy core parts 142 is provided. A talk suppressing effect can be obtained.

  Here, each dummy core 142 shown in FIG. 1 is provided between the signal transmission core 141 and the evaluation core 143, respectively. This makes it difficult for stray light to enter the signal transmission core unit 141 and the evaluation core unit 143, thereby improving the respective S / N ratios. As a result, the quality of optical communication in the signal transmission core unit 141 is improved, and the evaluation accuracy of the transmission characteristics evaluated in the evaluation core unit 143 is improved.

  In FIG. 1, two dummy core portions 142 are provided between the two signal transmission core portions 141. By providing a plurality of dummy core portions 142 in this way, the crosstalk suppression effect is particularly enhanced. This is because the number of interfaces between the dummy core portions 142 and the side cladding portions 15 is increased by providing a plurality of dummy core portions 142 as compared with the case where only one is provided. This is considered to be due to the high probability that light leaking from 141 is reflected and diffused at this interface.

  Further, the width and height (the thickness of the core layer 13) of each of the core parts 141, 142, and 143 are not particularly limited, but are preferably about 10 to 200 μm, and preferably about 15 to 100 μm. More preferably, it is about 20-70 micrometers. Accordingly, it is possible to increase the density of the signal transmission core portion 141 while suppressing a decrease in the transmission efficiency of the optical waveguide 1. As a result, the transmission capacity of the optical waveguide 1 can be increased.

  On the other hand, the width of the side cladding portion 15 positioned between the core portions 141, 142, 143 is preferably about 5 to 50 μm, more preferably about 7 to 45 μm, and about 10 to 40 μm. More preferably. Thereby, it is possible to increase the density of the optical waveguide 1 while preventing optical signals from being mixed (crosstalk) between the signal transmission core portions 141.

  The width of the dummy core part 142 is preferably narrower than the widths of the signal transmission core part 141 and the evaluation core part 143 adjacent to the dummy core part 142. By setting the width of the dummy core portion 142 in this way, it is possible to suppress crosstalk and increase the density of the optical waveguide 1.

  Specifically, the width of the dummy core part 142 is preferably about 10 to 95% of the width of the adjacent signal transmission core part 141, and more preferably about 15 to 90%.

  The “signal transmission core unit 141 and the evaluation core unit 143 adjacent to the dummy core unit 142” are the signal transmission core unit 141 that is closest to the dummy core unit 142 via the side clad unit 15 or the like. And the core part 143 for evaluation is pointed out.

  The width of the side cladding 15 is preferably narrower than the width of the signal transmission core 141, the dummy core 142 and the evaluation core 143 adjacent to the side cladding 15. By setting the width of the side cladding portion 15 in this way, it is possible to suppress crosstalk and increase the density of the optical waveguide 1.

  Specifically, the width of the side cladding 15 is preferably about 5 to 95% of the width of the adjacent signal transmission core 141, and more preferably about 10 to 90%.

  In addition, it is preferable that the width of the side cladding portion 15 located between the signal transmission core portions 141 is uniform throughout the entire optical waveguide 1. Thereby, the optical transmission environment around the signal transmission core unit 141 and the periphery of the evaluation core unit 143 can be made uniform. As a result, the optical transmission characteristics of the signal transmission core unit 141 become uniform, and the transmission efficiency is improved. This is because if the optical transmission characteristics are not uniform, a so-called bottleneck occurs and the overall transmission efficiency decreases. Further, the optical transmission characteristics of the evaluation core part 143 can be made uniform, and the evaluation accuracy can be improved. Note that the widths of the side cladding portions 15 are all uniform. The widths of the plurality of side cladding portions 15 located between the signal transmission core portions 141 in the entire optical waveguide 1 are the same, and each side surface The width of the clad portion 15 is also constant from one end to the other end. More preferably, the side cladding 15 that is not located between the signal transmission cores 141, and the side cladding 15 in the uppermost part and the lowermost part (in the blank part) in FIG. The width is made equal to the width of the other side clad portion 15.

  Further, the width of the evaluation core part 143 is preferably equal to the width of the signal transmission core part 141 adjacent to the evaluation core part 143. By setting the width of the evaluation core part 143 in this way, the evaluation core part 143 and the signal transmission core part 141 have the same structure. For this reason, it can be considered that both transmission characteristics are substantially the same, and by evaluating the transmission characteristics in the evaluation core section 143, the transmission characteristics in the signal transmission core section 141 are highly reliable. Can be indirectly evaluated. Note that, in the vicinity of at least one of the signal transmission core unit 141 and the evaluation core unit 143, a mark for distinguishing them may be attached as necessary.

  Here, as described above, the evaluation core unit 143 is a core unit for evaluating the transmission characteristics, and the signal transmission core unit 141 is not directly evaluated by evaluating the evaluation core unit 143. Can also be indirectly evaluated.

  In the first place, the transmission characteristics of the signal transmission core unit 141 are evaluated based on the intensity of the emitted light and the like when light enters the signal transmission core unit 141. However, there are manufacturers (laminated body manufacturers) that manufacture a laminated body of the clad layer 11, the core layer 13, and the clad layer 12, and manufacturers (electronic equipment manufacturers) that form mirrors 17 in the laminated body and incorporate them into electronic devices. In such a case, there is a problem in that the transmission characteristics of the signal transmission core unit 141 formed in the laminate cannot be evaluated at the stage where the laminate manufacturer ships the laminate. Specifically, on the assumption that an electronic device manufacturer forms a mirror, the signal transmission core portion 141 may not be exposed on the end face of the laminate. In such a case, signal transmission is performed at the stage of the laminate. The light cannot enter the core portion 141 for use. In this case, the laminate manufacturer cannot inspect the quality of the laminate to be shipped, and cannot guarantee the quality.

  In light of this problem, in the present invention, by providing the evaluation core portion 143 configured to allow light to enter even at the stage of the laminate, the signal transmission core portion 141 is not exposed on the surface of the laminate. Even in this case, the laminate manufacturer can indirectly inspect and evaluate the transmission characteristics and the like of the signal transmission core unit 141 at the time of shipment of the laminate. That is, according to the optical waveguide of the present invention, the transmission characteristics and the like can be evaluated regardless of the shape of the signal transmission core 141.

  Further, in the electronic equipment manufacturer, a light emitting element and a light receiving element are arranged corresponding to each signal transmission core portion 141 of the optical waveguide 1 and these are incorporated in the electronic equipment. Thereafter, when evaluating the operation of the electronic device, the signal light is incident on the signal transmission core unit 141.

  Here, when an abnormality is found in the operation of the electronic device, it is necessary to evaluate the characteristics of the optical waveguide alone in the process of investigating the cause. However, in a state where the optical waveguide is incorporated in the electronic device, light emitting elements and light receiving elements are arranged corresponding to the respective signal transmission core portions 141, and the intensity of the signal light emitted from the optical waveguide 1 depends on these elements. Therefore, there is a problem that the characteristics of the optical waveguide alone cannot be evaluated.

  On the other hand, if the evaluation core part 143 is not blocked by a light emitting element, a light receiving element, or the like, the characteristics of the optical waveguide alone can be evaluated by making light incident on the evaluation core part 143. It becomes possible. Thereby, the cause of the malfunction of an electronic device can be investigated reliably and a countermeasure can be taken.

  The constituent material (main material) of the core layer 13 as described above is, for example, acrylic resin, methacrylic resin, polycarbonate, polystyrene, cyclic ether resin such as epoxy resin or oxetane resin, polyamide, polyimide, poly Benzoxazole, polysilane, polysilazane, silicone resin, fluorine resin, polyurethane, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, polyester such as PET and PBT, polyethylene succinate, polysulfone, polyether, benzocyclo In addition to various resin materials such as cyclic olefin resins such as butene resin and norbornene resin, glass materials such as quartz glass and borosilicate glass can be used. Note that the resin material may be a composite material in which materials having different compositions are combined.

  Among these, at least one selected from the group consisting of (meth) acrylic resins, epoxy resins, silicone resins, polyimide resins, fluorine resins, and polyolefin resins is particularly preferable. A resin or epoxy resin is more preferable. Since these resin materials have high light transmittance, the optical waveguide 1 with particularly small transmission loss can be obtained.

  The evaluation core part 143 may be provided as necessary, and may be omitted. Even in this case, since the two dummy core portions 142 are provided between the two signal transmission core portions 141, crosstalk can be sufficiently suppressed.

(Clad layer)
On the other hand, the clad layers 11 and 12 are located below and above the core layer 13.

  The average thickness of the cladding layers 11 and 12 is preferably about 0.05 to 1.5 times the average thickness of the core layer 13, and more preferably about 0.1 to 1.25 times. Specifically, the average thickness of the cladding layers 11 and 12 is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and further preferably about 5 to 60 μm. Thereby, the function as a clad part is ensured while preventing the optical waveguide 1 from becoming thicker than necessary.

  Further, as the constituent material of the cladding layers 11 and 12, for example, the same material as the constituent material of the core layer 13 described above can be used, and in particular, (meth) acrylic resin, epoxy resin, silicone resin, It is preferably at least one selected from the group consisting of polyimide resins, fluorine resins, and polyolefin resins, and (meth) acrylic resins or epoxy resins are more preferable.

  The refractive index distribution in the thickness direction of the cross section of the optical waveguide 1 is not particularly limited, and examples thereof include SI type and GI type distributions.

  The number of signal transmission core portions 141 formed in the optical waveguide 1 is not particularly limited, but is preferably about 2 to 100, and more preferably about 2 to 50. If the number of signal transmission core portions 141 is large, the optical waveguide 1 may be multilayered as necessary. Specifically, the optical waveguide 1 shown in FIG. 2 can be multilayered by alternately stacking core layers and cladding layers.

  Further, the number of dummy core portions 142 provided between the two signal transmission core portions 141 is preferably about 2 to 10, more preferably about 2 to 8. Thereby, the density of the optical waveguide 1 can be increased while sufficiently suppressing the crosstalk generated between the signal transmission core portions 141.

  Further, the number of evaluation cores 143 provided between the two signal transmission cores 141 is preferably about 1 to 3.

  Further, if necessary, a support film may be provided on the lower surface of the optical waveguide 1 and a cover film may be provided on the upper surface, if necessary.

  Examples of the constituent material of the support film and the cover film include various resin materials such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polyimide, and polyamide.

  Moreover, although the average thickness of a support film and a cover film is not specifically limited, It is preferable that it is about 5-500 micrometers, and it is more preferable that it is about 10-400 micrometers. Thereby, since a support film and a cover film will have moderate rigidity, while supporting the optical waveguide 1 reliably, the optical waveguide 1 can be reliably protected from external force and an external environment.

(mirror)
The optical waveguide 1 according to this embodiment includes a mirror (optical path conversion unit) 17 that converts the optical path of the signal transmission core unit 141.

  FIGS. 1 and 3 are diagrams illustrating an example in which a mirror 17 is formed in the middle of the signal transmission core portion 141 of the optical waveguide 1.

  In the optical waveguide 1 shown in FIGS. 1 and 3, a concave portion 170 having a V-shaped longitudinal section is formed in the middle of the signal transmission core portion 141 so as to penetrate the signal transmission core portion 141 in the thickness direction. ing. The mirror 17 is constituted by a part of the inner surface of the recess 170. The mirror 17 has a planar shape and is inclined by 45 ° with respect to the axis (optical axis) of the signal transmission core 141. The light propagating through the signal transmission core unit 141 is reflected by the mirror 17, and the optical path is converted by 90 ° downward in FIG. Further, the light propagating from below in FIG. 3 is reflected by the mirror 17 and enters the signal transmission core unit 141. That is, the mirror 17 has an optical path conversion function for converting the optical path of the light propagating through the signal transmission core unit 141.

  If necessary, a reflective film may be formed on the surface of the processed surface constituting the mirror 17. Examples of the reflective film include a metal film such as Au, Ag, and Al, and a film made of a material having a lower refractive index than the signal transmission core portion 141. Examples of the metal film forming method include physical vapor deposition such as vacuum vapor deposition, chemical vapor deposition such as CVD, and plating.

  Further, the mirror 17 may be provided not in the middle of the signal transmission core portion 141 but in the side cladding portion 15 and on an extension line of the signal transmission core portion 141.

FIG. 4 is a plan view showing another configuration example of the core layer of the embodiment of the optical waveguide of the present invention.
In FIG. 4, the signal transmission core portion 141 does not reach the end of the optical waveguide 1 and is interrupted in the middle, and the side cladding portion 15 is formed there. A mirror 17 is formed in the side cladding portion 15. In such a case, the thin side cladding 15 exists between the mirror 17 and the signal transmission core 141, but the signal light propagates through the side cladding 15.

  The mirror 17 can be replaced with another optical path conversion unit such as a curved waveguide.

  Further, as shown in FIG. 1, the dummy core portion 142 adjacent to the signal transmission core portion 141 is configured to be interrupted in the vicinity of the mirror 17, that is, in a portion corresponding to the mirror 17. This prevents the dummy core part 142 from being exposed to the mirror 17. That is, since the width of the concave portion 170 is generally set wider than the width of the signal transmission core portion 141, when the dummy core portion 142 is not configured to be interrupted, the concave portion 170 and the dummy portion 170 There is a possibility that the dummy core part 142 may be exposed to the mirror 17 due to interference with the core part 142, but the dummy core part 142 becomes distant from the mirror 17 by interrupting the dummy core part 142 in the vicinity of the mirror 17. It can be prevented from being exposed. As a result, light leaking from the signal transmission core portion 141 or other stray light enters the dummy core portion 142 and is emitted from the mirror 17 to reach the light receiving element, or light emitted from the light emitting element. Is prevented from entering the dummy core portion 142 from the mirror 17. And it can avoid that the S / N ratio in optical communication falls.

<Optical waveguide manufacturing method>
Next, a method for manufacturing the optical waveguide of the present invention will be described.

  The optical waveguide 1 is manufactured by laminating a clad layer 11, a core layer 13, and a clad layer 12 in this order and press-bonding or bonding them. Of these, a signal transmission core portion 141 and a dummy core are provided in the core layer 13. In order to form the part 142, the evaluation core part 143, and the side cladding part 15, for example, a nanoimprint method, a direct drawing method, a direct exposure self-forming method, or the like is used. In the direct drawing method, irradiation with radiation such as light locally irradiates radiation toward a film having a refractive index modulation ability capable of forming a refractive index difference between an exposed area and an unexposed area, and then refracts. Each core part 141,142,143 and the side clad part 15 are formed by forming a rate difference.

  Examples of the principle of refractive index modulation include monomer diffusion, photobleaching, photoisomerization, photodimerization, and the like, and one or a combination of two or more of these is used. Of these, monomer diffusion is particularly preferably employed as the principle of refractive index modulation. In monomer diffusion, light is exposed (exposed) partially to a layer composed of a material in which a photopolymerizable monomer having a refractive index different from that of the polymer is dispersed in the polymer to polymerize the photopolymerizable monomer. In addition to causing the photopolymerizable monomer to move and be unevenly distributed, the refractive index is biased in the layer. That is, a difference in refractive index occurs between the exposed area and the non-exposed area of the layer. There are cases where the refractive index of the exposed region increases or decreases depending on the relationship in refractive index between the polymer and the photopolymerizable monomer. Accordingly, of the exposed region and the non-exposed region, the region on the high refractive index side becomes the core portions 141, 142, and 143, and the region on the low refractive index side becomes the side cladding portion 15.

  In the refractive index modulation based on such a principle, the core portions 141, 142, and 143 having any shape can be easily formed by simply selecting a region to be irradiated with light, so that the optical waveguide 1 is extremely efficient. Can be manufactured well. In addition, since the refractive index distribution formed by such a principle is formed corresponding to the concentration distribution of the photopolymerizable monomer, the refractive index distribution in the cross section of each of the formed core portions 141, 142, 143 is It is accompanied by a smooth refractive index change. As a result, the manufactured optical waveguide 1 has a GI-type refractive index distribution and has high transmission characteristics.

  Examples of a material that causes such monomer diffusion include a photosensitive resin composition described in Japanese Patent Application Laid-Open No. 2010-090328.

  On the other hand, in the case of refractive index modulation based on the principles of photobleaching, photoisomerization, and photodimerization, the amount of change in refractive index can be adjusted according to the amount of irradiated light (radiation amount). In photobleaching, the molecular structure in the material is cleaved by light irradiation, and the leaving group is detached from the main chain. As a result, the refractive index of the material is changed to form the core portions 141, 142, and 143. In photoisomerization and photodimerization, light irradiation causes photoisomerization or photodimerization of the material, and the refractive index of the material changes. Thereby, each core part 141, 142, 143 is formed.

  Examples of the material that causes photobleaching include core film materials described in JP-A-2009-145867.

  Examples of materials that cause photoisomerization include norbornene resins described in JP-A-2005-164650.

  Moreover, as a material which produces photodimerization, the photosensitive resin composition etc. which were described in Unexamined-Japanese-Patent No. 2011-105791 are mentioned, for example.

  In addition, by gradually changing the irradiation amount of the light to be irradiated, the formed refractive index distribution is accompanied by a smooth refractive index change. As a method of gradually changing the irradiation amount of the irradiated light, for example, a method using a multi-tone mask such as a gray-tone mask or a half-tone mask, a method of scanning a light beam having a distribution of light intensity, irradiation for each region Examples include a method of irradiating while changing the time.

  Alternatively, the refractive index difference may be formed by diffusing the refractive index adjusting agent in the polymer and continuously changing the concentration of the refractive index adjusting agent. Examples of a method for supplying the refractive index adjusting agent into the polymer include methods such as coating, spraying, adhesion, dipping, and deposition. When supplying the refractive index adjusting agent by such a supply method, an arbitrary refractive index distribution can be formed by adjusting the supply amount for each region. In addition, as a refractive index regulator, what was described in Unexamined-Japanese-Patent No. 2006-276735 is mentioned, for example.

  In addition, as an exposure apparatus used for the exposure process, an apparatus that performs exposure through a photomask corresponding to the waveguide pattern to be formed may be used. However, the photomask is controlled by finely controlling the light irradiation region. It is preferable to use an apparatus (maskless exposure apparatus) that selectively irradiates light only to an area to be exposed without using it. As a result, the exposure process can be efficiently performed with high spatial resolution. Further, since no photomask is required, the cost of the exposure process can be reduced, and different waveguide patterns can be quickly switched, so that a variety of products can be produced in small quantities.

  Examples of maskless exposure apparatuses include various spatial light modulation elements such as a reflection-side spatial light modulation element such as a digital micromirror device (DMD) and a transmission spatial light modulation element such as a liquid crystal display element (LCD). And a light source that emits light from a light source as a spatially modulated light beam.

Among these, as a light source, a lamp, a laser light source, LED, etc. are used, for example.
Other spatial light modulators than the above are MEMS (Micro Electro Mechanical System) -type spatial light modulators such as spatial light modulators (SLMs) and electro-optic effects such as PLZT elements. Examples thereof include a spatial light modulation element that modulates light and a liquid crystal light shutter.

  Further, a light source in which a plurality of light emitting points are arranged in a grid, for example, a laser diode (LD) array, a light emitting diode (LED) array, an organic EL array, or the like can be used for this exposure process. When such a light source is used, the spatial light modulation element can be omitted.

  In addition to the light source and the spatial light modulator, the maskless exposure apparatus may include an XYZ stage that drives the object to be processed, various optical systems, a control unit that controls the operation of the light source and the spatial light modulator, and the like. Good.

  Each core part 141, 142, 143 is formed simultaneously by the above methods. Therefore, it is considered that the signal transmission core portion 141 and the evaluation core portion 143 have undergone the same manufacturing history, and the composition, molecular structure, and the like are substantially equal. For this reason, based on the evaluation by the evaluation core unit 143, the transmission characteristics of the signal transmission core unit 141 can be accurately evaluated while being indirect.

<Electronic equipment>
As described above, the optical waveguide of the present invention as described above can suppress a decrease in transmission efficiency in the optical waveguide even when connected to other optical components. Therefore, 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, by providing such an electronic device with the optical waveguide of the present invention, problems such as noise and signal degradation peculiar to electrical wiring are eliminated, and a dramatic improvement in performance can be expected.

  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.

  As mentioned above, although the optical waveguide and electronic device of this invention were demonstrated based on embodiment of illustration, this invention is not limited to these.

Next, specific examples of the present invention will be described.
1. Production of optical waveguide (Example 1)
(1) Production of Cladding Layer Forming Resin Composition Daicel Chemical Industries, Ltd. Alicyclic Epoxy Resin, Celoxide 2081 20 g, ADEKA Co., Ltd. Cationic Polymerization Initiator, Adekaoptomer SP-170 0.6 g A solution was prepared by stirring and mixing 80 g of methyl isobutyl ketone.

  Subsequently, the obtained solution was filtered with a PTFE filter having a pore size of 0.2 μm to obtain a clean and colorless and transparent resin composition for forming a cladding layer.

(2) Manufacture of photosensitive resin composition As an epoxy polymer, phenoxy resin manufactured by Nippon Steel Chemical Co., Ltd., 20 g of YP-50S, 5 g of Celoxide 2021P manufactured by Daicel Chemical Industries, Ltd. as a photopolymerizable monomer, and polymerization As an initiator, 0.2 g of Adekaoptomer SP-170 manufactured by ADEKA Corporation was put into 80 g of methyl isobutyl ketone, and dissolved by stirring to prepare a solution.

  Subsequently, the obtained solution was filtered with a PTFE filter having a pore size of 0.2 μm to obtain a clean, colorless and transparent photosensitive resin composition.

(3) Production of lower clad layer The clad layer-forming resin composition was uniformly applied onto a polyimide film having a thickness of 25 µm by a doctor blade, and then placed in a dryer at 50 ° C for 10 minutes. After the solvent was completely removed, the entire surface was irradiated with ultraviolet rays with a UV exposure machine to cure the applied resin composition. As a result, a colorless and transparent lower cladding layer having a thickness of 10 μm was obtained. The cumulative amount of ultraviolet light was 500 mJ / cm ² .

(4) Production of core layer The photosensitive resin composition was uniformly applied by a doctor blade on the produced lower clad layer, and then placed in a dryer at 40 ° C for 5 minutes. After completely removing the solvent to form a film, ultraviolet rays were irradiated by a maskless exposure apparatus so as to draw a linear pattern of lines and spaces on the obtained film. The cumulative amount of ultraviolet light was 1000 mJ / cm ² .

  Next, the exposed film was placed in an oven at 150 ° C. for 30 minutes. Upon removal from the oven, it was confirmed that a clear waveguide pattern appeared on the coating. Details of the waveguide pattern are shown below.

<Waveguide pattern>
One evaluation core part was disposed between the two signal transmission core parts, and a dummy core part was disposed between the signal transmission core part and the evaluation core part. And the side clad part was arrange | positioned on both sides so that each core part might be pinched | interposed. The dummy core part was formed so as to be interrupted in the vicinity of the part where the mirror is formed (see FIG. 1).

-Number of signal transmission cores: 4 Width: 66 μm
Pitch: 250 μm
-Number of dummy cores: 6 Width: 39 μm
・ Evaluation core part Number: 3 Width: 66 μm
-Number of side cladding parts (between signal transmission core parts): 12 (other than between signal transmission core parts): 2 Width: 10 μm
In addition, the thickness of the obtained core layer was 50 micrometers.

(5) Production of upper clad layer A clad layer-forming resin composition was applied to the produced core layer in the same manner as in (3) to obtain a colorless and transparent upper clad layer having a thickness of 10 μm.

(6) Fabrication of mirror Next, a recess was formed by laser processing to fabricate a mirror. Thereby, an optical waveguide having a length of 10 cm was obtained.

(Example 2)
An optical waveguide was obtained in the same manner as in Example 1 except that the evaluation core was omitted. FIG. 5 is a plan view showing the core layer of the optical waveguide obtained in the second embodiment.

(Comparative Example 1)
An optical waveguide was obtained in the same manner as in Example 1 except that the dummy core and the evaluation core were omitted.

2. Evaluation of optical waveguide When the light is incident on one signal transmission core portion among the optical waveguides obtained in each of the examples and comparative examples, the intensity of the light emitted from the adjacent signal transmission core portion is measured. Was used to evaluate the presence or absence of crosstalk.

  As a result, in the optical waveguides obtained in the respective examples, it became clear that the intensity of the light emitted from the adjacent signal transmission cores is small, and the occurrence of crosstalk is suppressed. In particular, the tendency was remarkable in the optical waveguide obtained in Example 1.

  On the other hand, in the optical waveguide obtained in Comparative Example 1, the intensity of the light emitted from the adjacent signal transmission cores was slightly high, and the occurrence of crosstalk was recognized.

  From the above results, it is clear that the occurrence of crosstalk can be sufficiently suppressed in the optical waveguide according to the present invention.

  Moreover, the transmission efficiency of each optical waveguide was measured by the cutback method. At this time, transmission efficiency was measured for both the signal transmission core and the evaluation core. As a result, the difference in transmission efficiency between the signal transmission core unit and the evaluation core unit was 0.1% or less of the transmission efficiency of the signal transmission core unit. Furthermore, the difference in transmission efficiency measured for each of the four signal transmission core portions and the three evaluation core portions was also 0.1% or less of the transmission efficiency of the signal transmission core portion. Therefore, in the optical waveguide according to the present invention, it is recognized that the transmission characteristic of the signal transmission core part formed in the optical waveguide can be indirectly evaluated by evaluating the transmission characteristic of the evaluation core part. It was.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 11, 12 Clad layer 13 Core layer 141 Core part for signal transmission 142 Core part for dummy 143 Core part for evaluation 15 Side clad part 170 Recessed part 17 Mirror

Claims (13)

An optical waveguide having a flat plate shape,
Two signal transmission core units provided in parallel and used for transmitting optical signals;
An evaluation core unit provided in parallel with the signal transmission core unit between the two signal transmission core units and used for evaluation of transmission characteristics;
A dummy core portion that is provided in parallel with the signal transmission core portion between the two signal transmission core portions and is not used for transmission of an optical signal;
An optical waveguide comprising: a signal transmission core portion, an evaluation core portion, and a dummy core portion adjacent to each other and a side cladding portion having a lower refractive index than these core portions.   The optical waveguide according to claim 1, wherein the dummy core portion is provided between the signal transmission core portion and the evaluation core portion.   3. The optical waveguide according to claim 1, wherein a width of the dummy core portion is narrower than a width of the signal transmission core portion and the evaluation core portion adjacent to the dummy core portion.   4. The optical device according to claim 1, wherein a width of the side cladding portion is narrower than a width of the signal transmission core portion, the evaluation core portion, and the dummy core portion adjacent to the side cladding portion. Waveguide.   5. The optical waveguide according to claim 1, wherein a width of the evaluation core portion is equal to a width of the signal transmission core portion adjacent to the evaluation core portion.   The optical waveguide according to any one of claims 1 to 5, further comprising an optical path conversion unit that is provided in the middle of the signal transmission core unit or on an extension line and converts an optical path of the signal transmission core unit. The dummy core part is provided on both sides via the signal transmission core part,
The optical waveguide according to claim 6, wherein the dummy core section adjacent to the signal transmission core section provided with the optical path conversion section is configured to be interrupted in the vicinity of the optical path conversion section.   The optical waveguide according to claim 6 or 7, wherein the evaluation core part is configured to be exposed at an end face of the optical waveguide. An optical waveguide having a flat plate shape,
Two signal transmission core units provided in parallel and used for transmitting optical signals;
A plurality of dummy core portions that are provided in parallel with the signal transmission core portion between the two signal transmission core portions and are not used for transmission of optical signals;
An optical waveguide comprising: a side clad portion provided adjacent to each of the signal transmission core portion and the dummy core portion and having a lower refractive index than the core portions.   The optical waveguide according to claim 1, wherein a width of the side clad portion is 5 to 50 μm.   11. The optical waveguide according to claim 1, wherein all of the widths of the side clad portions located between the two signal transmission core portions are uniform.   The optical waveguide performs a maskless exposure process on the base material to generate a refractive index difference between the exposed area and the non-exposed area, and the higher refractive index side of the exposed area and the non-exposed area. The optical waveguide according to any one of claims 1 to 11, wherein the regions are formed as the core portions, and the region on the low refractive index side is the side cladding portion.   An electronic apparatus comprising the optical waveguide according to claim 1.

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