JP5169639B2 - Optical waveguide - Google Patents

Description

  The present invention relates to an optical waveguide.

  In recent years, optical communications that transport data using optical frequency carriers have become increasingly important. In such optical communication, there is an optical waveguide as a means for guiding an optical frequency carrier wave from one point to another point.

  For example, the optical waveguide includes a pair of cladding layers and a core layer provided between the pair of cladding layers. The core layer has a linear core portion and clad portions provided on both sides of the core portion so as to sandwich the core portion. The core portion is made of a material that is substantially transparent to light of an optical frequency carrier wave, and the cladding layer and the cladding portion are made of a material having a lower refractive index than the core portion.

  Patent Document 1 discloses a polymer having two clad layers (an upper clad layer and a lower clad layer) and a polysilane layer provided between them and formed using a polysilane composition containing polysilane and an organic peroxide. An optical waveguide is disclosed. In the polysilane layer, a core layer (core portion) and side clad layers (cladding portions) provided on both sides thereof are formed.

  In such an optical waveguide, the core portion is surrounded by a cladding layer and a cladding portion having a refractive index lower than that of the core portion. Therefore, the light introduced from the end portion of the core portion is conveyed along the axis of the core portion while being reflected at the boundary between the cladding layer and the cladding portion.

  Further, a light emitting element such as a semiconductor laser is disposed on the incident side of the optical waveguide, and light generated from the light emitting element is incident on the core portion of the optical waveguide. On the other hand, a light receiving element such as a photodiode is disposed on the exit side of the optical waveguide, and the light propagating through the core is received by the light receiving element. Then, optical communication is enabled based on the blinking pattern of light received by the light receiving element.

  By the way, when the optical waveguide is adjacent to the low refractive index medium, specifically, when the optical waveguide is in the air, not only the boundary between the core portion and the cladding portion but also the cladding portion and the air. Light is also reflected at the boundary.

  Here, on the incident side of the optical waveguide, it is preferable that all of the light generated by the light emitting element is incident on the core part. However, in general, the optical axis is misaligned and the numerical aperture is matched between the optical waveguide and the light emitting element. Some light may be incident on the cladding due to a defect or the like.

  The light incident on the cladding in this way is repeatedly reflected at the boundary with air and propagates to the end. Finally, the light is emitted from the end of the clad portion and is received by the light receiving element together with the light emitted from the core portion. As a result, there is a problem that light propagating through the cladding part becomes noise and lowers the S / N ratio, leading to a decrease in optical communication quality due to crosstalk or the like.

JP 2004-333883 A

  An object of the present invention is to provide an optical waveguide capable of improving the S / N ratio of signal light and capable of high-quality optical communication by having means for guiding light propagating in the cladding part to a position far from the core part. There is to do.

Such an object is achieved by the present inventions (1) to (15) below.
(1) An optical waveguide comprising a core part and a clad part provided adjacent to the core part,
In the cladding portion, the refractive index is lower than that of the core portion, the low refractive index region in contact with the core portion, the refractive index is higher than the low refractive index region, and the core is interposed through the low refractive index region. a first high refractive index region and the second high refractive index region spaced from the section has a,
The first high refractive index region is made of the same material as the core portion, and a difference between the refractive index and the refractive index of the low refractive index region is 0.5% or more, and passes through the core portion. A region having a shape in which the cross-sectional area gradually decreases and the distance from the core portion gradually increases as the light travels forward, and is exposed to the light incident side end face of the optical waveguide. And
The second high-refractive index region is a region that has a higher refractive index than the low-refractive index region and has a long shape parallel to the core portion, and the core portion and the first high-refractive index region. An optical waveguide characterized by being positioned from the middle of the core portion to the light emission side between the regions .
(2) The optical waveguide according to (1) , wherein the second high refractive index region reflects light leaked from the core portion to the low refractive index region and confines it to the core portion side. .

(3) An optical waveguide comprising a core portion and a clad portion provided adjacent to the core portion,
In the cladding portion, the refractive index is lower than that of the core portion, the low refractive index region in contact with the core portion, the refractive index is higher than the low refractive index region, and the core is interposed through the low refractive index region. a first high refractive index region and the third high refractive-index areas separated from the part, has a,
The first high refractive index region is made of the same material as the core portion, and a difference between the refractive index and the refractive index of the low refractive index region is 0.5% or more, and passes through the core portion. A region having a shape in which the cross-sectional area gradually decreases and the distance from the core portion gradually increases as the light travels forward, and is exposed to the light incident side end face of the optical waveguide. And
The third high refractive index region is a region having a refractive index higher than that of the low refractive index region and scattered or aligned in the cladding portion, and the core portion and the first high refractive index region. An optical waveguide characterized by being positioned from the middle of the core portion to the light emitting side .
(4) Each said 3rd high refractive index area | region is what refracts the light which each passes the said cladding part in the direction away from the said core part, or scatters irregularly as described in said (3) . Optical waveguide.

(5) The optical waveguide according to (3) or (4), wherein the third high refractive index region has an elongated shape in plan view.
(6) The optical waveguide according to (5), wherein a length of a long side of the third high refractive index region is 2 to 50 times a short side.

(7) Said 3rd high refractive index area | region is comprised so that the axis line may incline in the back of the advancing direction of the light which passes the said core part with respect to the perpendicular of the axis line of the said core part. The optical waveguide according to 5) or (6).
(8) The optical waveguide according to (5) or (6), wherein an axis of the third high refractive index region is configured to be orthogonal to an axis of the core portion.
(9) The optical waveguide according to (5) or (6), wherein the third high-refractive index region has a shape with an uneven contour.

(10) In any one of the above (1) to (9), the first high refractive index region occupies almost the entire surface of the light incident side of the optical waveguide where the cladding portion is exposed. The optical waveguide described.

(11) The optical waveguide according to any one of (1) to (10) , wherein the first high refractive index region is formed in the same manufacturing process as the core portion.

(12) The optical waveguide has a laminate formed by laminating the first layer, the second layer, and the third layer in this order,
A part of the second layer forms the core part,
The optical waveguide according to any one of (1) to (11) , wherein the remaining portion of the second layer, the first layer, and the third layer constitute the cladding portion.

(13) The optical waveguide according to (12) , wherein the first high refractive index region is provided in the second layer.

(14) The optical waveguide includes a plurality of the core portions and the first high refractive index region provided between the core portions in the second layer,
The first high refractive index region has a shape that converges to an intermediate portion between two adjacent core portions as it goes forward in the traveling direction of light passing through the core portion (1 The optical waveguide according to any one of (13) to (13) .

(15) The optical waveguide according to any one of (1) to (14) , wherein the core portion of the optical waveguide and at least a part of the cladding portion are each composed of a norbornene polymer as a main material. .

  According to the present invention, since the light incident on the clad part is guided away from the core part, the light is suppressed from propagating through the clad part to the output end, and the light propagating through the clad part is received by the light receiving element. The light intensity when receiving light is reduced. Thereby, an optical waveguide capable of high-quality optical communication can be provided by improving the S / N ratio as a carrier wave propagating through the optical waveguide and suppressing crosstalk and the like.

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

<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 (partially cut out and shown in a transparent manner), and FIG. 2 is a plan view showing only the core layer of the optical waveguide shown in FIG. 3 is a diagram illustrating an example of a propagation path of light propagating through the core layer illustrated in FIG. In the following description, the upper side in FIG. 1 is referred to as “upper” or “upper”, the lower side is referred to as “lower” or “lower”, and the right side in FIGS. The left side is referred to as “left” or “incident side”. In FIG. 1, the thickness direction of the layers (the vertical direction in each figure) is exaggerated.

  An optical waveguide 10 shown in FIG. 1 is formed by laminating a cladding layer (cladding portion) 11, a core layer 13 and a cladding layer (cladding portion) 12 in this order from the lower side in FIG. A core portion 14 having a predetermined pattern and a side clad portion 15 (clad portion) adjacent to the core portion (waveguide channel) 14 are formed. In FIG. 1, two core portions 14 and three side clad portions 15 are provided alternately.

  The optical waveguide 10 shown in FIG. 1 totally reflects light incident on the core portion 14 of the incident side end face 10a at the interface between the core portion 14 and the clad portions (the clad layers 11 and 12 and the side clad portions 15). And propagating to the exit side can be taken out from the core portion 14 of the exit side end face 10b.

  As will be described in detail later, each side cladding 15 includes a high refractive index region 151 having a higher refractive index than other regions (low refractive index regions 152) in the side cladding 15 respectively. That is, the side cladding 15 is divided into a high refractive index region 151 and a low refractive index region 152 having a refractive index lower than that of the high refractive index region 151.

  The difference in refractive index between the core portion 14 and the low refractive index region 152 in the side cladding portion 15 is not particularly limited, but is preferably 0.5% or more, and more preferably 0.8% or more. . On the other hand, the upper limit value may not be set, but is preferably about 5.5%. If the difference in refractive index is less than the lower limit, the effect of transmitting light may be reduced, and even if the upper limit is exceeded, no further increase in light transmission efficiency can be expected.

The refractive index difference is expressed by the following equation when the refractive index of the core portion 14 is A and the refractive index of the low refractive index region 152 is B.
Refractive index difference (%) = | A / B-1 | × 100

  Moreover, in the structure shown in FIG. 1, although the core part 14 is formed in linear form by planar view, you may curve and branch in the middle and the shape is arbitrary. In addition, if the manufacturing method of the optical waveguide 10 mentioned later is used, the complicated and arbitrary-shaped core part 14 can be formed easily and with sufficient dimensional accuracy.

  Further, the core section 14 has a quadrangular shape such as a square or a rectangle (rectangle) in cross section.

  The width and height of the core part 14 are not particularly limited, but are preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and still more preferably about 10 to 60 μm.

  The core portion 14 is made of a material having a higher refractive index than the low refractive index region 152 in the side clad portion 15, and is made of a material having a higher refractive index than the cladding layers 11 and 12. .

  The constituent materials of the core part 14, the side clad part 15, and the clad layers 11 and 12 are not particularly limited as long as the above-described refractive index difference is generated, but in the present embodiment, the core part 14 and the side clad part 15. Are made of the same material (core layer 13), and the refractive index difference between the core portion 14 and the low refractive index region 152 and the refractive index difference between the high refractive index region 151 and the low refractive index region 152 are , Each is expressed by the difference in the chemical structure of the material.

  Any material can be used as the constituent material of the core layer 13 as long as it is a material that is substantially transparent to the light propagating through the core portion 14. Specifically, an acrylic resin or a methacrylic resin can be used. , Polycarbonate, polystyrene, epoxy resin, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, and various resin materials such as cyclic olefin resin such as benzocyclobutene resin and norbornene resin, quartz glass, borosilicate A glass material such as acid glass can be used.

  Among these, in order to express a difference in refractive index due to a difference in chemical structure as in the present embodiment, the refractive index changes by irradiation with active energy rays such as ultraviolet rays and electron beams (or by further heating). Preferably it is a material.

  Examples of such a material include a material whose chemical structure can be changed by, for example, breaking at least a part of a bond or detaching at least a part of a functional group by irradiation with active energy rays or heating. Can be mentioned.

  Specifically, silane-based resins such as polysilane (eg, polymethylphenylsilane), polysilazane (eg, perhydropolysilazane), and the resin serving as a base for materials with structural changes as described above include molecules on the molecular side. The following resins (1) to (6) having a functional group at the chain or terminal may be mentioned. (1) Addition (co) polymer of norbornene type monomer obtained by addition (co) polymerization of norbornene type monomer, (2) Addition copolymer of norbornene type monomer and ethylene or α-olefins, (3) An addition copolymer of a norbornene-type monomer and a non-conjugated diene and, if necessary, another monomer, (4) a ring-opening (co) polymer of a norbornene-type monomer, and, if necessary, the (co) polymer A hydrogenated resin, (5) a ring-opening copolymer of a norbornene monomer and ethylene or α-olefins, and a resin in which the (co) polymer is hydrogenated, if necessary, (6) a norbornene monomer Ring-opening copolymers with non-conjugated dienes or other monomers, and norbornene-based resins such as resins obtained by hydrogenating the (co) polymers if necessary, other photo-curing reactive monomers An acrylic resin or an epoxy resin obtained by polymerizing a polymer.

  Of these, norbornene resins are particularly preferred. These norbornene-based polymers include, for example, ring-opening metathesis polymerization (ROMP), combination of ROMP and hydrogenation reaction, polymerization by radical or cation, polymerization using a cationic palladium polymerization initiator, and other polymerization initiators ( For example, it can be obtained by any known polymerization method such as polymerization using a polymerization initiator of nickel or another transition metal).

  On the other hand, the clad layers 11 and 12 constitute the clad portions located at the lower part and the upper part of the core part 14, respectively. With such a configuration, the core portion 14 functions as a light guide path whose outer periphery is surrounded by the cladding portion.

  The average thickness of the cladding layers 11 and 12 is preferably about 0.1 to 1.5 times the average thickness of the core layer 13, more preferably about 0.3 to 1.25 times, Specifically, the average thickness of the clad layers 11 and 12 is not particularly limited, but is usually preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and more preferably about 10 to 60 μm. More preferably. Thereby, the function as a clad layer is suitably exhibited while preventing the optical waveguide 10 from being unnecessarily enlarged (thickened).

  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, but a norbornene polymer is particularly preferable.

  In the present embodiment, it is possible to select and use different materials appropriately between the constituent material of the core layer 13 and the constituent materials of the cladding layers 11 and 12 in consideration of the refractive index difference between the two. Is possible. Therefore, in order to ensure total reflection of light at the boundary between the core layer 13 and the cladding layers 11 and 12, a material may be selected so that a sufficient difference in refractive index is generated. Thereby, a sufficient refractive index difference is obtained in the thickness direction of the optical waveguide 10, and light can be prevented from leaking from the core portion 14 to the cladding layers 11 and 12. As a result, attenuation of light propagating through the core portion 14 can be suppressed.

  From the viewpoint of suppressing light attenuation, it is preferable that the adhesion between the core layer 13 and the cladding layers 11 and 12 is high. Therefore, the constituent material of the cladding layers 11 and 12 is any material as long as the refractive index is lower than that of the constituent material of the core layer 13 and the adhesiveness with the constituent material of the core layer 13 is high. May be.

  For example, the norbornene-based polymer having a relatively low refractive index is preferably one containing a norbornene repeating unit having a substituent containing an epoxy structure at the terminal. Such a norbornene-based polymer has a particularly low refractive index and good adhesion.

  Further, the norbornene-based polymer preferably contains an alkylnorbornene repeating unit. Since a norbornene-based polymer containing an alkylnorbornene repeating unit has high flexibility, high flexibility (flexibility) can be imparted to the optical waveguide 10 by using such norbornene-based polymer.

  Examples of the alkyl group that the alkylnorbornene repeating unit has include a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group, and a hexyl group is particularly preferable. These alkyl groups may be either linear or branched.

  By including the repeating unit of hexyl norbornene, it is possible to prevent the refractive index of the entire norbornene-based polymer from increasing. A norbornene-based polymer having a repeating unit of hexyl norbornene is preferable because it has excellent transmittance with respect to light in the wavelength region as described above (particularly in the wavelength region near 850 nm).

  The constituent materials of the clad layer 11, the side clad portion 15, and the clad layer 12 may be the same (same type) or different materials, but these preferably have approximate refractive indexes. .

  The optical waveguide 10 of the present invention is slightly different depending on the optical characteristics of the material of the core portion 14 and is not particularly limited. For example, the optical waveguide 10 is preferably used in data communication using light in the wavelength region of about 600 to 1550 nm. Is done.

  Here, as described above, the side cladding 15 is divided into a high refractive index region 151 and a low refractive index region 152 having a refractive index lower than that of the high refractive index region 151.

  The optical waveguide of the present invention is characterized in that such a high refractive index region is included in a part of the clad portion.

Hereinafter, the high refractive index region 151 and the low refractive index region 152 will be described in detail.
As shown in FIG. 2, the low refractive index region 152 is provided so as to be in contact with each core portion 14 in each side cladding portion 15. On the other hand, the high refractive index region 151 is provided so as not to be in direct contact with each core portion 14 as shown in FIG. That is, the low refractive index region 152 is interposed between the high refractive index region 151 and each core portion 14.

  Further, the high refractive index region 151 extends from the incident side end surface 10 a toward the emission side end surface 10 b in the side cladding portion 15. The high refractive index region 151 has a cross-sectional area that gradually decreases from the incident-side end surface 10a toward the exit-side end surface 10b, and has a so-called “wedge shape” in plan view.

  On the other hand, the low refractive index region 152 also extends from the incident side end face 10 a toward the emission side end face 10 b in the side cladding portion 15. The low refractive index region 152 has a “wedge shape” in which the cross-sectional area gradually increases from the incident side end surface 10a toward the output side end surface 10b.

  Further, among the surfaces constituting the high refractive index region 151, the surface 1510 on the adjacent core portion 14 side is away from the adjacent core portion 14 as it goes from the incident side to the output side, as shown in FIG. Inclined with respect to the axis of the core portion 14. As a result, a sufficient separation distance between the exposed surface of the core portion 14 and the exposed surface of the high refractive index region 151 is ensured on the output-side end surface 10b of the optical waveguide 10.

Here, a conventional optical waveguide will be described.
FIG. 16 is a plan view showing only the core layer 93 of the conventional optical waveguide 90.

  The core layer 93 shown in FIG. 16 is configured by alternately arranging two core portions 94 and three side clad portions 95 provided in parallel. Further, in order to irradiate such core layer 93 with communication light, a light emitting element 97 is provided on the incident side of the optical waveguide 90 corresponding to each core portion 94, and signal light is emitted on the emission side. A light receiving element 98 for receiving light is provided.

  In such a core layer 93, since the refractive index of air is smaller than the refractive index of the side cladding portion 95, total reflection of light occurs at the interface between the side cladding portion 95 and its external space (air). For this reason, the light incident on the side clad part 95 for some reason propagates while repeating total reflection at the interface between the side clad part 95 and air, and is emitted from the emission side end face 90b. Thereby, a part of the light propagating through the side clad portion 95 reaches the light receiving element 98 together with the signal light propagating through the core portion 94. As a result, the light propagating through the side clad portion 95 becomes noise for the signal light, leading to a decrease in the S / N ratio as a carrier wave and the occurrence of crosstalk. For this reason, in the conventional optical waveguide 90, it has been a problem to reduce the light propagating through the side clad portion 95.

  By the way, as one of the causes of the incidence of light on the side clad portion 95, the deviation between the optical axis of the optical waveguide 90 and the optical axis of the light emitting element 97, and the mismatch between the numerical apertures of the optical waveguide 90 and the light emitting element 97 are possible. Is mentioned. Originally, it is preferable to match the numerical apertures so that the optical axis of the core portion 94 coincides with the optical axis of the light emitting element 97 and all the light generated from the light emitting element 97 is incident on the core portion 94. However, when these are insufficient, a part of light is incident on the side clad portion 95 of the incident side end face 90 a of the optical waveguide 90. In addition, since the cross section of the core portion 94 is extremely small, it is extremely difficult to match the optical axes and match the numerical apertures when the light emitting element 97 is disposed.

  Further, even when the optical axis of the optical waveguide 90 and the optical axis of the light receiving element 98 are shifted, and when the numerical apertures of the optical waveguide 90 and the light receiving element 98 are incompatible, the light propagates through the side cladding portion 95. The transmitted light reaches the light receiving element 98, and the S / N ratio as a carrier wave is lowered.

  Therefore, in the present invention, as described above, a part of the side cladding portion 15 has a higher refractive index than other regions (low refractive index regions 152) and has a “wedge shape” as described above. By providing the refractive index region 151, the light propagating through the side cladding portion 15 of the optical waveguide 10 can be guided into the high refractive index region 151 and away from the core portion 14. In addition, at the emission side end face 10 b of the optical waveguide 10, it is possible to ensure a sufficient separation distance between the exposed surface of the core portion 14 and the exposed surface of the high refractive index region 151. As a result, even if light is incident on the side clad portion 15, the light selectively propagates through the high refractive index region 151. Therefore, the light is separated from the core portion 14 along the wedge shape. Can be guided.

  Here, FIG. 3 shows a path of light passing through the optical waveguide shown in FIG. According to the present invention, as shown in FIG. 3, the light (indicated by the broken line arrow) that passes through the side cladding part 15 without affecting the light (indicated by the solid line arrow) that passes through the core part 14. Guided away from the core 14. As a result, on the emission side end face 10b, the emission position 14L of the signal light that has propagated through the core portion 14 and the emission position 151L of the noise light that has propagated through the high refractive index region 151 can be sufficiently separated. And it can suppress that this noise light is received by the light receiving element 18, and can prevent that the S / N ratio as a carrier wave falls.

  Further, the high refractive index region 151 is separated from the core portion 14 as shown in FIG. If the high refractive index region 151 and the core portion 14 are in contact with each other, the light propagating through the core portion 14 from this portion may branch to the high refractive index region 151 side. Since the core part 14 is separated, it is possible to prevent light propagating through the core part 14 from branching to the high refractive index region 151 side.

  Such a high refractive index region 151 may have a refractive index higher than that of the other region of the side cladding portion 15, that is, the low refractive index region 152, but preferably the difference is 0.5% or more. Preferably, the difference is 0.8% or more. Moreover, although an upper limit does not need to be set in particular, Preferably it is set to 5.5%. By providing such a sufficient refractive index difference between the high refractive index region 151 and the low refractive index region 152, total reflection is surely generated at the interface between the high refractive index region 151 and the low refractive index region 152. be able to. As a result, it is possible to more reliably prevent light propagating through the high refractive index region 151 from unintentionally leaking into the low refractive index region 152.

  In FIG. 2, the high refractive index region 151 is exposed on the incident side end face 10 a, so that light that has not entered the core portion 14 among the light generated from the light emitting element is directly refracted. It becomes easy to enter the rate area 151. As a result, light that has not entered the core portion 14 can be reliably incident on the high refractive index region 151 and can be moved away from the core portion 14.

  Furthermore, from the above viewpoint, if the exposed surface of the high refractive index region 151 occupies as much of the exposed surface of the side cladding portion 15 as possible on the incident side end surface 10a, the light that has not entered the core portion 14 can be obtained. More can be incident on the high refractive index region 151. Therefore, as shown in FIG. 2, since the exposed surface of the high refractive index region 151 occupies almost the entire exposed surface of the side cladding portion 15, most of the light not incident on the core portion 14 is in the high refractive index region. 151 and the S / N ratio of the optical waveguide 10 can be further increased.

  On the other hand, as shown in FIG. 2, the high refractive index region 151 is exposed at a position farthest from the core portion 14 on the output side end face 10 b of the optical waveguide 10. That is, among the three side clad parts 15 shown in FIG. 2, in the side clad part 15 sandwiched between the core parts 14, 14, the output side end face of the high refractive index region 151 is between the core parts 14, 14. Located in the center. Further, in the remaining two side clad portions 15, the exit side end face of the high refractive index region 151 is located at the corner farthest from the adjacent core portion 14 among the exposed surfaces of the respective side clad portions 15. As described above, since the high refractive index region 151 is exposed at the position farthest from the core portion 14 on the emission side end face 10b of the optical waveguide 10, the probability that noise light reaches the light receiving element can be particularly reduced. . That is, the intensity of noise light emitted near the boundary between the core portion 14 and the side cladding portion 15 can be reduced, and the S / N ratio can be particularly increased.

  In addition, as shown in FIG. 2, when there are a plurality of core portions 14 and 14 (multichannel), if the high refractive index region 151 as described above is provided, It is possible to effectively suppress noise light received by light receiving elements other than the corresponding light receiving elements, that is, leakage of signal light from another channel (crosstalk).

  In addition, the high refractive index region 151 shown in FIG. 2 gradually moves away from the core portion 14 as the surface 1510 on the adjacent core portion 14 side moves forward in the traveling direction of light passing through the core portion 14. However, such a shape may be provided only on a part of the surface 1510 on the core part 14 side. That is, the surface 1510 on the core portion 14 side of the high refractive index region 151 has a shape such that a part thereof gradually moves away from the core portion 14 as described above, and the remaining portion is parallel to the core portion 14. Also good.

Next, an example of a method for manufacturing the optical waveguide 10 will be described.
The optical waveguide 10 is manufactured by forming a clad layer 11 (first layer), a core layer 13 (second layer), and a clad layer 12 (third layer), and laminating them. The

  In such a manufacturing method, it is necessary to produce so that the site | parts from which a refractive index mutually mutually contacts physically and optically. Specifically, it is necessary to form the low refractive index region 152 and the clad layers 11 and 12 so as to be in close contact with the core portion 14 without a gap. Further, the high refractive index region 151 and the low refractive index region 152 and the clad layers 11 and 12 need to be in close contact with each other.

  The specific manufacturing method is not particularly limited as long as the core part 14, the high refractive index region 151, the low refractive index region 152, and the like can be formed in the same layer (second layer). , Photobleaching method, photolithography method, direct exposure method, nanoimprinting method, monomer diffusion method and the like.

  Here, as a representative, a method for manufacturing the optical waveguide 10 by the monomer diffusion method will be described.

  4 to 8 are cross-sectional views schematically showing process examples of the method for manufacturing the optical waveguide 10 shown in FIG. 5, 6, and 8 are cross-sectional views taken along line AA in FIG. 2.

[1] First, the layer 110 is formed on the support substrate 161 (see FIG. 4).
The layer 110 is formed by a method in which a core layer forming material (varnish) 100 is applied and cured (solidified).

  Specifically, the layer 110 is formed by applying the core layer forming material 100 on the support substrate 161 to form a liquid film, and then placing the support substrate 161 on a ventilated level table so that the surface of the liquid film is not coated. It is formed by leveling the uniform part and evaporating (desolving) the solvent.

  When the layer 110 is formed by a coating method, examples thereof include a doctor blade method, a spin coating method, a dipping method, a table coating method, a spray method, an applicator method, a curtain coating method, a die coating method, and the like. It is not done.

  As the support substrate 161, for example, a silicon substrate, a silicon dioxide substrate, a glass substrate, a quartz substrate, a polyethylene terephthalate (PET) film, or the like is used.

  The core layer-forming material 100 contains a developable material composed of a polymer 115 and an additive 120 (including at least a monomer and a catalyst). It is a material that causes a reaction.

  In the resulting layer 110, all of the polymer (matrix) 115 is substantially uniformly and randomly distributed, and the additive 120 is substantially uniformly and randomly dispersed in the polymer 115. ing. Thereby, the additive 120 is substantially uniformly and arbitrarily dispersed in the layer 110.

  The average thickness of the layer 110 is appropriately set according to the thickness of the core layer 13 to be formed, and is not particularly limited, but is preferably about 5 to 200 μm, and preferably about 10 to 100 μm. More preferably, it is about 15 to 65 μm.

  The polymer 115 has sufficiently high transparency (colorless and transparent) and is compatible with the monomer described later, and the monomer can react (polymerization reaction or crosslinking reaction) as described later. Even after the monomers are polymerized, those having sufficient transparency are preferably used.

Here, “having compatibility” means that the monomer is at least mixed and does not cause phase separation with the polymer 115 in the core layer forming material 100 or the layer 110.
As such a polymer 115, the constituent material of the core layer 13 mentioned above is mentioned.

  When a norbornene-based polymer is used as the polymer 115, since the polymer has high hydrophobicity, it is possible to obtain the core layer 13 that is less likely to cause a dimensional change due to water absorption.

  The norbornene-based polymer may be either a polymer having a single repeating unit (homopolymer) or a polymer having two or more norbornene-based repeating units (copolymer).

  Among these, as an example of the copolymer, a compound having a repeating unit represented by the following formula (1) is preferably used.

［式中、ｍは、１〜４の整数を表し、ｎは、１〜９の整数を表す。］

[Wherein, m represents an integer of 1 to 4, and n represents an integer of 1 to 9. ]

  The types of copolymer include those in which the two units of the above formula (1) are arranged in an arbitrary order (random), those in which they are arranged alternately, those in which each unit is solidified (in a block form), etc. Any of these forms may be used.

  Here, when the norbornene-based polymer is used as the polymer 115, an example of the additive 120 is preferably selected to include a norbornene-based monomer, a promoter (first substance), and a catalyst precursor (second substance). Is done.

  The norbornene-based monomer reacts in the active radiation irradiated region by irradiation with actinic radiation, which will be described later, and forms a reaction product. Due to the presence of this reactant, the layer 110 is irradiated in the irradiated region and in the non-active radiation irradiated region. , A compound capable of producing a refractive index difference.

  Here, the reaction product includes a polymer (polymer) formed by polymerizing a norbornene-based monomer in the polymer (matrix) 115, a crosslinked structure that cross-links the polymers 115, and a polymer polymerized by polymer 115. At least one of the branched structures branched from 115 (branch polymer or side chain (pendant group)).

  Here, in the layer 110, when it is desired that the refractive index of the irradiated region be high, a polymer 115 having a relatively low refractive index and a norbornene-based monomer having a high refractive index with respect to the polymer 115 are obtained. When it is used in combination and it is desired that the refractive index of the irradiated region is low, a polymer 115 having a relatively high refractive index and a norbornene-based monomer having a low refractive index with respect to the polymer 115 are combined. used.

  Note that “high” or “low” in the refractive index does not mean the absolute value of the refractive index but means a relative relationship between certain materials.

  When the refractive index of the irradiated region in the layer 110 decreases due to the reaction of the norbornene-based monomer (generation of a reaction product), the portion becomes the side cladding portion 15, and when the refractive index of the irradiated region increases, the portion is It becomes the core part 14.

  The catalyst precursor (second substance) is a substance capable of initiating the above-described monomer reaction (polymerization reaction, crosslinking reaction, etc.), and is a promoter (first substance) activated by irradiation with actinic radiation described later. It is a substance whose activation temperature changes by the action of.

  As the catalyst precursor (procatalyst), any compound may be used as long as the activation temperature changes (increases or decreases) with irradiation of actinic radiation. Those whose activation temperature decreases with irradiation are preferred. Thereby, the core layer 13 (optical waveguide 10) can be formed by heat treatment at a relatively low temperature, and unnecessary heat is applied to the other layers, so that the characteristics (optical transmission performance) of the optical waveguide 10 are deteriorated. Can be prevented.

  As such a catalyst precursor, a catalyst precursor containing (mainly) at least one of the compounds represented by the following formulas (Ia) and (Ib) is preferably used.

(E (R) ₃ ) ₂ Pd (Q) ₂ ... (Ia)
[(E (R) ₃ ) _a Pd (Q) (LB) _b ] _p [WCA] _r (Ib)
[In the formulas Ia and Ib, E (R) ₃ represents a neutral electron donor ligand of group 15, respectively, E represents an element selected from group 15 of the periodic table, and R represents , Represents a moiety containing a hydrogen atom (or one of its isotopes) or a hydrocarbon group, and Q represents an anionic ligand selected from carboxylate, thiocarboxylate and dithiocarboxylate. In Formula Ib, LB represents a Lewis base, WCA represents a weakly coordinating anion, a represents an integer of 1 to 3, b represents an integer of 0 to 2, and a and b , P and r represent numbers that balance the charge of the palladium cation and the weakly coordinated anion. ]

Typical catalyst precursors according to Formula Ia include Pd (OAc) ₂ (P (i-Pr) ₃ ) ₂ , Pd (OAc) ₂ (P (Cy) ₃ ) ₂ , Pd (O ₂ CCMe ₃ ) ₂ (P (Cy) ₃ ) ₂ , Pd (OAc) ₂ (P (Cp) ₃ ) ₂ , Pd (O ₂ CCF ₃ ) ₂ (P (Cy) ₃ ) ₂ , Pd (O ₂ CC ₆ H ₅ ) ₃ (P (Cy) ₃ ) ₂ may be mentioned, but is not limited thereto. Here, Cp represents a cyclopentyl group, and Cy represents a cyclohexyl group.

  The catalyst precursor represented by the formula Ib is preferably a compound in which p and r are each selected from integers of 1 and 2.

Typical catalyst precursors according to such formula Ib include Pd (OAc) ₂ (P (Cy) ₃ ) ₂ . Here, Cy represents a cyclohexyl group, and Ac represents an acetyl group.

  These catalyst precursors can efficiently react with a monomer (in the case of a norbornene-based monomer, an efficient polymerization reaction, a crosslinking reaction, etc. by an addition polymerization reaction).

  The cocatalyst (first substance) is a substance that can be activated by irradiation with actinic radiation to change the activation temperature of the catalyst precursor (procatalyst) (the temperature at which the monomer reacts).

  As the cocatalyst (cocatalyst), any compound can be used as long as it has a molecular structure that changes (reacts or decomposes) when activated by irradiation with actinic radiation. A compound (photoinitiator) that decomposes upon irradiation with actinic radiation and generates a cation such as a proton or other cation and a weakly coordinated anion (WCA) that can be substituted with a leaving group of the catalyst precursor ( (Mainly) is preferably used.

Examples of the weak coordination anion include tetrakis (pentafluorophenyl) borate ion (FABA ⁻ ), hexafluoroantimonate ion (SbF ₆ ⁻ ), and the like.

  Examples of the promoter (photoacid generator or photobase generator) include tetrakis (pentafluorophenyl) borate and hexafluoroantimonate, tetrakis (pentafluorophenyl) gallate, and aluminates. , Antimonates, other borates, gallates, carboranes, halocarboranes and the like.

  Moreover, you may make it add a sensitizer in the core layer forming material (varnish) 100 as needed.

  Furthermore, an antioxidant can be added to the core layer forming material 100. Thereby, generation of undesirable free radicals and natural oxidation of the polymer 115 can be prevented. As a result, the characteristics of the obtained core layer 13 (optical waveguide 10) can be improved.

The layer 110 is formed using the core layer forming material 100 as described above.
At this time, the layer 110 has a first refractive index. This first refractive index is due to the action of the polymer 115 and monomers that are uniformly dispersed (distributed) in the layer 110.

  Further, in the description of the additive 120 described above, the case where the monomer is a norbornene-based monomer has been described as an example. However, as the other monomer, a compound having a polymerizable site may be used, and acrylic acid (methacrylic acid) may be used. Examples of such monomers include epoxy monomers, epoxy monomers, and styrene monomers, and one or more of these can be used in combination.

  The catalyst in the additive 120 may be appropriately selected according to the type of monomer. For example, in the case of an acrylic acid monomer or an epoxy monomer, the addition of the catalyst precursor (second substance) is omitted. can do.

  [2] Next, a mask (masking) 135 in which an opening (window) 1351 is formed is prepared, and the layer 110 is irradiated with active radiation (active energy light) 130 through the mask 135 (FIG. 5). reference).

  In the following, a case where the monomer has a lower refractive index than that of the polymer 115 and the core layer forming material 100 is described as an example where the refractive index of the irradiated region 125 decreases as the active radiation 130 is irradiated.

  That is, in the example shown here, the irradiation region 125 of the active radiation 130 becomes the low refractive index region 152 in the side cladding portion 15.

  Therefore, in the example shown here, an opening (window) 1351 equivalent to the pattern of the low refractive index region 152 to be formed is formed in the mask 135. This opening 1351 forms a transmission part through which the active radiation 130 to be irradiated passes.

  The mask 135 may be formed in advance (separately formed) (for example, plate-shaped) or may be formed on the layer 110 by, for example, a vapor deposition method or a coating method.

  The actinic radiation 130 to be used is not limited as long as it can cause a photochemical reaction (change) with respect to the promoter. For example, in addition to visible light, ultraviolet light, infrared light, laser light, an electron beam or X Lines or the like can also be used.

  When the layer 110 is irradiated with the active radiation 130 through the mask 135, the cocatalyst (first substance: cocatalyst) present in the irradiation region 125 irradiated with the active radiation 130 reacts by the action of the active radiation 130. (Binding) or decomposition to release (generate) cations (protons or other cations) and weakly coordinating anions (WCA).

  These cations and weakly coordinating anions cause a change (decomposition) in the molecular structure of the catalyst precursor (second substance: procatalyst) present in the irradiation region 125, and this is changed into an active latent state (latent potential). Active state).

  Note that in the case where light having high directivity such as laser light is used as the active radiation 130, the use of the mask 135 may be omitted.

[3] Next, the layer 110 is subjected to heat treatment (first heat treatment).
Thereby, in the irradiation area | region 125, the catalyst precursor of an active latent state is activated (it will be in an active state), and monomer reaction (a polymerization reaction or a crosslinking reaction) will arise.

  As the monomer reaction proceeds, the monomer concentration in the irradiation region 125 gradually decreases. As a result, there is a difference in monomer concentration between the irradiated region 125 and the unirradiated region 140, and in order to eliminate this, the monomer diffuses from the unirradiated region 140 (monomer diffusion) and collects in the irradiated region 125. come.

  As a result, in the irradiated region 125, the monomer and its reaction product (polymer, cross-linked structure or branched structure) increase, and the structure derived from the monomer greatly affects the refractive index of the region, and the first refraction The second refractive index lower than the refractive index. As the monomer polymer, an addition (co) polymer is mainly produced.

  On the other hand, in the unirradiated region 140, the amount of monomer decreases as the monomer diffuses from the region to the irradiated region 125, so that the influence of the polymer 115 appears greatly on the refractive index of the region, and the first refraction The third refractive index is higher than the refractive index.

  In this way, a refractive index difference (second refractive index <third refractive index) occurs between the irradiated region 125 and the non-irradiated region 140, and the core portion 14 and the high refractive index region 151 (unirradiated region). 140) and a low refractive index region 152 (irradiation region 125) are formed (see FIG. 6).

[4] Next, the layer 110 is subjected to a second heat treatment.
As a result, the catalyst precursor remaining in the unirradiated region 140 and / or the irradiated region 125 is activated (in an activated state) directly or with the activation of the cocatalyst. The remaining monomer is reacted.

  In this way, by reacting the monomers remaining in the regions 125 and 140, the core portion 14, the high refractive index region 151, and the low refractive index region 152 obtained can be stabilized.

[5] Next, the layer 110 is subjected to a third heat treatment.
Thereby, reduction of internal stress generated in the obtained core layer 13 and further stabilization of the core part 14, the high refractive index region 151, and the low refractive index region 152 can be achieved.

Through the above steps, the core layer 13 (second layer) is obtained.
For example, a sufficient refractive index difference is obtained between the core portion 14 and the high refractive index region 151 and the low refractive index region 152 before the second heat treatment and the third heat treatment are performed. If present, this step [5] and the step [4] may be omitted.

  [6] Next, the clad layer 11 (12) is formed on the support substrate 162 (see FIG. 7).

  As a method for forming the clad layer 11 (12), a method of applying and curing (solidifying) a varnish (clad layer forming material) including a clad material, and a method of applying and hardening (solidifying) a monomer composition having curability. Any method may be used.

  When the clad layer 11 (12) is formed by a coating method, examples thereof include a spin coating method, a dipping method, a table coating method, a spray method, an applicator method, a curtain coating method, and a die coating method.

As the support substrate 162, a substrate similar to the support substrate 161 can be used.
As described above, the clad layer 11 (12) is formed on the support substrate 162.

  [7] Next, the core layer 13 is peeled from the support substrate 161, and the core layer 13 is separated from the support substrate 162 on which the cladding layer 11 (first layer) is formed and the cladding layer 12 (third layer). Is sandwiched between the support substrate 162 formed with (see FIG. 8).

  Then, as indicated by the arrows in FIG. 8, pressure is applied from the upper surface side of the support substrate 162 on which the cladding layer 12 is formed, and the cladding layers 11 and 12 and the core layer 13 are pressure bonded.

  As a result, the cladding layers 11 and 12 (first and third layers) and the core layer 13 (second layer) are joined and integrated.

  Further, this crimping operation is preferably performed under heating. The heating temperature is appropriately determined depending on the constituent materials of the clad layers 11 and 12 and the core layer 13, and is usually preferably about 80 to 200 ° C., more preferably about 120 to 180 ° C.

  Next, the support substrate 162 is peeled off and removed from the cladding layers 11 and 12, respectively. Thereby, the optical waveguide 10 (the optical waveguide of the present invention) is obtained.

  According to the above method, the core part 14 and the high refractive index region 151 can be formed simultaneously in the same manufacturing process. For this reason, the high refractive index region 151 and the low refractive index region 152 can be efficiently formed in the side cladding portion 15 without increasing the number of steps from the conventional manufacturing method.

  Moreover, the core part 14 and the high refractive index region 151 formed in this way are made of the same kind of material. For this reason, both have the same coefficient of thermal expansion, and it is possible to reduce defects such as deformation of the optical waveguide 10 and delamination due to temperature changes, as compared with the case where they are made of different materials.

  Although the method for manufacturing the optical waveguide 10 by the monomer diffusion method has been described above, as described above, other methods as described above can be used for the method for manufacturing the optical waveguide 10.

  Among these, in the photobleaching method, for example, a release agent (substance) activated by irradiation with actinic radiation, and a main chain and a release agent branched from the main chain and activated, thereby causing at least one molecular structure. A core layer forming material containing a polymer having a leaving group (detachable pendant group) that can be detached from the main chain of the part is used. After this core layer forming material is formed into a layer, a part of this layer is irradiated with actinic radiation such as ultraviolet rays, whereby the leaving group is detached (cut), and the refractive index of the region changes. (Rise or fall). For example, if the refractive index decreases with the removal of the leaving group, the active radiation irradiation region becomes the low refractive index region 152, and the other region becomes the core portion 14 or the high refractive index region 151. After the core layer 13 is formed in this manner, the clad layers 11 and 12 are bonded to both surfaces of the core layer 13 as described above.

  On the other hand, in the photolithography method, for example, a layer of a material for forming a core part having a high refractive index is formed on the cladding layer 11, and a resist having a shape corresponding to the core part 14 and the high refractive index region 151 is formed on this layer. A film is formed by photolithography. Then, using this resist film as a mask, the core portion forming material layer is etched. Thereby, the core part 14 and the high refractive index area | region 151 are obtained. Thereafter, a relatively low refractive index cladding material is formed so as to cover the core portion 14 and the high refractive index region 151, thereby cladding the gap between the core portion 14 and the high refractive index region 151. The portion forming material is filled, and the low refractive index region 152 is obtained. Further, the cladding layer 12 is obtained by supplying the cladding portion forming material so as to cover these (the core portion 14, the high refractive index region 151, and the low refractive index region 152).

Second Embodiment
Next, a second embodiment of the optical waveguide of the present invention will be described.
FIG. 9 is a plan view showing only the core layer of the second embodiment of the optical waveguide of the present invention.

  Hereinafter, the optical waveguide according to the present embodiment will be described. However, differences from the optical waveguide according to the first embodiment will be mainly described, and description of similar matters will be omitted.

  The optical waveguide according to the present embodiment is the same as that of the first embodiment except that the high-refractive index region and the low-refractive index region have different patterns in plan view.

  The side cladding portion 15 shown in FIG. 9 is provided with a high refractive index region 151 having a wedge shape similar to that of the first embodiment, and is provided closer to the core portion 14 than the high refractive index region 151, and has a belt shape in plan view. It has two high refractive index regions 153 (second high refractive index regions).

  These two high-refractive index regions 153 are regions having a higher refractive index than the low-refractive index region 152, similar to the high-refractive index region 151, and are positioned on both sides of the core portion 14 in the core layer 13. .

  Each high refractive index region 153 is provided separately from the high refractive index region 151, and is provided so as not to directly contact each core portion 14. That is, the low refractive index region 152 is inserted between the high refractive index region 153 and the high refractive index region 151 and between the high refractive index region 153 and each core portion 14. Yes.

  Further, the band-like high refractive index region 153 is exposed on the emission side end face 10b, but is not exposed on the incident side end face 10a.

  Since the optical waveguide 10 according to this embodiment has a high refractive index region 151 having a wedge shape similar to that of the first embodiment, the same operations and effects as those of the first embodiment are obtained. Play.

Here, problems of the conventional optical waveguide will be described.
In the conventional optical waveguide 90 shown in FIG. 16, there is a problem that light unintentionally propagates through the side cladding portion 95, and one of the causes that light enters the side cladding portion 95 is as described above. In the first embodiment, the deviation between the optical axis of the core portion 94 and the optical axis of the light emitting element 97 and the incompatibility of the numerical apertures of the optical waveguide 90 and the light emitting element 97 are mentioned.

  By the way, another cause is that light leaks from the core portion 94 to the side cladding portion 95 in the middle of the optical waveguide 90. The light leaking from the core portion 94 propagates through the side cladding portion 95 and is received by the light receiving element 97 as noise light as described above. Such a phenomenon of light leaking from the core portion 94 occurs when there is no sufficient refractive index difference between the core portion 94 and the side cladding portion 95.

  Therefore, in the present embodiment, in the side clad portion 15 of the optical waveguide 10, in addition to the high refractive index region 151 having a wedge shape, a high refractive index region 153 having a strip shape (second high refractive index region) is provided. It was decided. In such an optical waveguide 10, light leaked from the core portion 14 to the side cladding portion 15 (low refractive index region 152) during the propagation of the light incident from the incident side end surface 10 a to the output side end surface 10 b It is possible to prevent the leaked light from being diffused to the side by being reflected inward by the refractive index region 153. That is, the leaked light can be confined inside the high refractive index region 153. Thereby, it can prevent that signal light changes into noise light in the middle of the optical waveguide 10, and can reduce the light intensity of noise light on the emission side end face 10b. As a result, the S / N ratio as a carrier wave can be further increased as compared with the first embodiment. In the case of multi-channel, crosstalk can be suppressed. In FIG. 9, an example of a propagation path of light leaking from the core portion 14 is indicated by an arrow.

  The high refractive index region 153 can be formed simultaneously in the same manufacturing process as the core portion 14 and the high refractive index region 151. Thereby, the high refractive index region 151, the low refractive index region 152, and the high refractive index region 153 can be efficiently formed in the side cladding portion 15 without increasing the number of steps from the conventional manufacturing method.

  The high refractive index region 153 may be made of any material as long as it has a higher refractive index than the low refractive index region 152, but is made of the same material as the core portion 14 and the high refractive index region 151. As a result, the thermal expansion coefficients of the optical waveguides 10 are equal, and defects such as deformation and delamination of the optical waveguide 10 due to temperature changes can be further reduced as compared with the case where the materials are made of different materials.

  Further, the difference in refractive index between each high refractive index region 153 and low refractive index region 152 is preferably 0.5% or more, more preferably 0.8% or more. Moreover, although an upper limit does not need to be set in particular, Preferably it is set to 5.5%.

<Third Embodiment>
Next, a third embodiment of the optical waveguide of the present invention will be described.
FIG. 10 is a plan view showing only the core layer of the third embodiment of the optical waveguide of the present invention.

  Hereinafter, although the optical waveguide according to the present embodiment will be described, differences from the optical waveguide according to the second embodiment will be mainly described, and description of similar matters will be omitted.

  The optical waveguide according to the present embodiment is the same as that of the second embodiment except that the high-refractive index region and the low-refractive index region have different patterns in plan view.

  The side cladding portion 15 shown in FIG. 10 is provided with a high refractive index region 151 having a wedge shape similar to that of the first embodiment, and is provided closer to the core portion 14 than the high refractive index region 151, and has a strip shape in plan view. And a plurality of high refractive index regions 154 (third high refractive index regions). In addition, each high refractive index area | region 154 shown in FIG. 10 has comprised the parallelogram by planar view.

  The plurality of high-refractive index regions 154 are regions having a higher refractive index than the low-refractive index region 152, as in the high-refractive index region 151, and are aligned on both sides of the core portion 14. Moreover, each high refractive index area | region 154 shown in FIG. 10 has comprised the elongate parallelogram, and it is preferable that the length of a long side is about 2 to 50 times of a short side, and is about 5 to 30 times. Is more preferable.

  Each high refractive index region 154 is provided separately from the high refractive index region 151 and is provided so as not to directly contact each core portion 14. That is, the low refractive index region 152 is interposed between the high refractive index region 154 and the high refractive index region 151 and between the high refractive index region 154 and each core portion 14. .

Here, FIG. 11 shows another configuration example of the third embodiment shown in FIG.
The optical waveguide 10 shown in FIG. 11 is the same as FIG. 10 except that the shape of the high refractive index region having a strip shape is different in plan view. That is, the side cladding portion 15 shown in FIG. 11 is provided with a high refractive index region 151 having a wedge shape similar to that of the first embodiment, and is provided closer to the core portion 14 than the high refractive index region 151, and is a strip in plan view. The plurality of high-refractive index regions 154 ′ (third high-refractive index regions) are formed in a shape, and the plurality of high-refractive index regions 154 ′ form an elongated triangle in plan view.

  Further, like the high refractive index region 154 according to the third embodiment, such a high refractive index region 154 ′ has light whose axis passes through the core portion 14 with respect to the perpendicular of the axis of the core portion 14. It is provided so as to incline backward in the traveling direction.

  Further, each high refractive index region 154 ′ has a shape such that the cross-sectional area gradually increases as the distance from the core portion 14 side increases.

  In FIG. 11, in the plurality of high refractive index regions 154 ′ forming a long and narrow triangle in plan view, the inner angle located on the core portion 14 side is an acute angle and is smaller than the other inner angles. Specifically, the inner angle is preferably about 3 to 30 °, and more preferably about 5 to 20 °. In this case, the length of the side facing the inner corner located on the core part 14 side is shorter than the other two sides.

FIG. 12 shows still another configuration example of the third embodiment shown in FIG.
The optical waveguide 10 shown in FIG. 12 is the same as FIG. 10 except that the shape of the high refractive index region having a strip shape is different in plan view. That is, the side cladding portion 15 shown in FIG. 12 is provided on the side of the core portion 14 with respect to the high refractive index region 151 having a wedge shape similar to that of the first embodiment, and the strip portion in a plan view. A plurality of high-refractive index regions 154 ″ (third high-refractive index regions) having a shape, the plurality of high-refractive index regions 154 ″ having an elongated rectangular shape in plan view, and The axis is arranged so as to be substantially perpendicular to the axis of the core portion 14.

  Each high refractive index region 154 ″ shown in FIG. 12 has an elongated rectangular shape, but the length of the long side is preferably about 2 to 50 times the short side, and is about 5 to 30 times. Is more preferable.

  Each of these high refractive index regions 154 ′ and each high refractive index region 154 ″ has the same function as each of the high refractive index regions 154 described above.

  Since the optical waveguide 10 according to the present embodiment has a high refractive index region 151 having a wedge shape similar to that of the first embodiment, the same operation and function as those of the first embodiment are provided. There is an effect.

  In the present embodiment, in addition to the wedge-shaped high refractive index region 151, a strip-shaped high refractive index region 154 (third high refractive index region) is provided in the side cladding portion 15 of the optical waveguide 10. We decided to provide it. In such an optical waveguide 10, light leaked from the core portion 14 to the side cladding portion 15 (low refractive index region 152) during the propagation of the light incident from the incident side end surface 10 a to the output side end surface 10 b The leaked light can be kept away from the core portion 14 by being refracted or scattered outward in the refractive index region 154. In FIG. 10, an example of a propagation path of light leaking from the core unit 14 is indicated by an arrow.

  From this point of view, the strip-shaped high refractive index region 154 is provided such that each axis thereof is inclined rearward in the traveling direction of the light passing through the core portion 14 with respect to the perpendicular of the axis of the core portion 14. It only has to be done. As a result, the light transmitted through the high refractive index region 154 is refracted so as to be away from the core portion 14 inevitably. As a result, the light leaking from the core part 14 can be kept away from the core part 14, and the light intensity of noise light in the vicinity of the core part 14 can be reduced on the emission side end face 10 b. That is, since the difference in light intensity between the signal light and the noise light can be clarified in the vicinity of the core portion 14, the S / N ratio as a carrier wave can be further increased as compared with the first embodiment. In the case of multi-channel, crosstalk can be suppressed.

  Note that an angle θ (a tilt angle of the high refractive index region 154) θ formed by the perpendicular of the axis of the core portion 14 and the axis of the high refractive index region 154 having a strip shape shown in FIG. 10 is the same as that of the high refractive index region 154. Depending on the difference in refractive index from the low refractive index region 152, the width of the side cladding 15 and the like, the light passing through the side cladding 15 is appropriately set to be refracted as necessary and sufficient.

  Specifically, the inclination angle θ of the high refractive index region 154 is preferably about 10 to 85 °, and more preferably about 20 to 70 °. By setting the inclination angle θ within the above range, the light leaked from the core portion 14 is refracted so as to be surely separated from the core portion 14, and the signal light and the noise light are separated at the emission side end face 10 b of the optical waveguide 10. Can be separated. As a result, the S / N ratio as a carrier wave can be more reliably increased.

  Also, the separation distance between the high refractive index regions 154 is appropriately set according to the refractive index difference between the high refractive index region 154 and the low refractive index region 152, the width of the side cladding portion 15, and the like.

  Furthermore, the width of each high-refractive index region 154 is also set as appropriate, but as an example, it is preferably about 1 to 30 μm, more preferably about 3 to 20 μm.

  Further, the difference in refractive index between each high refractive index region 154 and low refractive index region 152 is preferably 0.5% or more, and more preferably 0.8% or more. Moreover, although an upper limit does not need to be set in particular, Preferably it is set to 5.5%.

<Fourth embodiment>
Next, a fourth embodiment of the optical waveguide of the present invention will be described.
FIG. 13 is a plan view showing only the core layer of the fourth embodiment of the optical waveguide of the present invention.

  Hereinafter, the optical waveguide according to the present embodiment will be described, but the description will focus on differences from the optical waveguide according to the third embodiment, and description of similar matters will be omitted.

  The optical waveguide according to this embodiment is the same as that of the third embodiment except that the high-refractive index region and the low-refractive index region have different patterns in plan view.

  The side cladding portion 15 shown in FIG. 13 is provided on the side of the core portion 14 with respect to the high refractive index region 151 having a wedge shape similar to that of the first embodiment, and is granular in a plan view. A plurality of high refractive index regions 155 (third high refractive index regions).

  The plurality of high-refractive index regions 155 are regions having a higher refractive index than the low-refractive index region 152, as in the high-refractive index region 151, and are scattered on both sides of the core portion 14.

  The high refractive index regions 155 are independent from each other, are provided separately from the high refractive index regions 151, and are provided so as not to directly contact the core portions 14. That is, the low refractive index region 152 is interposed between the high refractive index region 155 and the high refractive index region 151 and between the high refractive index region 154 and each core portion 14. .

  Since the optical waveguide 10 according to this embodiment has a high refractive index region 151 having a wedge shape similar to that of the first embodiment, the same operations and effects as those of the first embodiment are obtained. Play.

  In this embodiment, in addition to the high refractive index region 151 having a wedge shape, a granular high refractive index region 155 (third high refractive index region) is provided in the side cladding portion 15 of the optical waveguide 10. It was decided. In such an optical waveguide 10, the light leaked from the core portion 14 to the side cladding portion 15 (low refractive index region 152) during the propagation of the light incident from the incident side end surface 10 a to the output side end surface 10 b is high. When the refractive index region 155 is reached, it is scattered irregularly there. As a result, the light leaking from the core portion 14 to the side cladding portion 15 spreads over a wide range and attenuates before reaching the emission-side end surface 10b. As a result, at the emission side end face 10b, the light intensity of the noise light emitted from the side cladding portion 15 is reduced, and the difference in light intensity between the signal light and the noise light can be clarified. The S / N ratio can be further increased compared to the first embodiment. In the case of multi-channel, crosstalk can be suppressed.

  The shape of the high refractive index region 155 having a granular shape in plan view is not particularly limited. For example, the shape is a circle such as a perfect circle, an ellipse, or an ellipse, a triangle, a quadrangle, a hexagon, an octagon, or a star shape. It can be a square, semicircle, fan, needle, or the like.

  Further, the outline of the high refractive index region 155 preferably has irregularities as shown in FIG. As a result, the contour of the high refractive index region 155 has irregularity on the surface that receives the light leaking from the core portion 14, and can reliably diffuse the light.

  The average particle size of each high refractive index region 155 is preferably about 10 to 500 μm, and more preferably about 20 to 300 μm. By setting the average particle diameter of each high refractive index region 155 within the above range, the probability that each high refractive index region 155 scatters light can be sufficiently increased.

  The arrangement density of each high refractive index region 155 is appropriately set according to the refractive index difference between the high refractive index region 155 and the low refractive index region 152, the width of the side cladding portion 15, and the like. Preferably, it is irregular (random). By making the arrangement pattern random, it is possible to sufficiently exhibit the function of the high refractive index region 155 that prevents scattered light from interfering and disperses and attenuates noise light.

  The difference in refractive index between each high refractive index region 155 and low refractive index region 152 is preferably 0.5% or more, more preferably 0.8% or more. Moreover, although an upper limit does not need to be set in particular, Preferably it is set to 5.5%.

  As mentioned above, although the optical waveguide of the present invention has been described based on the illustrated embodiments, the present invention is not limited to these, and the configuration of each part is replaced with any configuration that can exhibit the same function. In addition, an arbitrary configuration may be added.

  Moreover, the optical waveguide of the present invention may be an appropriate combination of any two or more of the configurations of the above embodiments.

  Furthermore, in each said embodiment, although the two core parts 14 are provided in the core layer 13, the number of the core parts 14 may be 1 or 3 or more.

  In each of the above embodiments, the high refractive index regions 151, 153, 154, and 155 are provided in the side cladding portion 15, but these high refractive index regions are provided in the cladding layers 11 and 12. May be.

  Such an optical waveguide of the present invention can be used for an optical wiring for optical communication, for example.

  In addition, this optical wiring can be combined with existing electrical wiring on a substrate to constitute a so-called “optical / electrical mixed substrate”. In such an optical / electrical hybrid substrate, for example, an optical signal transmitted through an optical wiring (core portion of an optical waveguide) is converted into an electrical signal in an optical device and transmitted to the electrical wiring. As a result, high-speed and large-capacity information transmission can be achieved in the optical wiring portion as compared with the conventional electric wiring. Therefore, for example, by applying this optical / electrical hybrid board to a bus or the like that connects between an arithmetic device such as a CPU or LSI and a storage device such as a RAM, the performance of the entire system is improved and electromagnetic noise is generated. Can be suppressed.

  It is conceivable that the optical / electrical hybrid board is mounted on electronic devices that transmit large amounts of data at high speed, such as mobile phones, game machines, personal computers, televisions, home servers, and the like.

  Hereinafter, specific examples of the present invention will be described.

1. Production of optical waveguide (Example 1)
First, a core layer forming material containing a norbornene polymer having a repeating unit represented by the following formula (2) was prepared.

  Next, this core layer forming material was applied onto a substrate to form a liquid film. Next, this liquid film was dried to obtain a layer of a material for forming a core layer.

  Next, this layer was irradiated with ultraviolet rays through a mask having an opening (window) corresponding to the low refractive index region to be formed. The layer was then heated in an oven. Thereby, the region irradiated with ultraviolet rays becomes a low refractive index region (refractive index: 1.54), and the region not irradiated with ultraviolet rays is the core portion (refractive index: 1.55) and a high refractive index region (refractive index). : 1.55), and as a result, a core layer was obtained. The core portion, the high refractive index region, and the low refractive index region have the shapes shown in FIG.

  Next, a norbornene-based polymer having a refractive index lower than that of the polymer used for the core layer forming material was prepared, and a clad layer forming material including this was prepared.

  Next, this clad layer forming material was applied on each of the two substrates to form a liquid film. Next, these liquid coatings were dried to obtain clad layers.

  And the clad layer was bonded together on both surfaces of the obtained core layer. Thereby, an optical waveguide was obtained.

(Example 2)
An optical waveguide was obtained in the same manner as in Example 1 except that the shapes of the core portion, the high refractive index region, and the low refractive index region were changed to the shapes shown in FIG.

(Example 3)
An optical waveguide was obtained in the same manner as in Example 1 except that the shapes of the core portion, the high refractive index region, and the low refractive index region were changed to the shapes shown in FIG. However, the inclination angle of the high refractive index region was 45 °.

Example 4
An optical waveguide was obtained in the same manner as in Example 1 except that the shapes of the core portion, the high refractive index region, and the low refractive index region were changed to the shapes shown in FIG. However, the inclination angle of the high refractive index region is the same as in Example 3.

(Example 5)
An optical waveguide was obtained in the same manner as in Example 1 except that the shapes of the core portion, the high refractive index region, and the low refractive index region were changed to the shapes shown in FIG.

(Example 6)
An optical waveguide was obtained in the same manner as in Example 1 except that the shapes of the core portion, the high refractive index region, and the low refractive index region were changed to the shapes shown in FIG.

(Comparative example)
Except for the formation of the high refractive index region and the low refractive index region, and as shown in FIG. 16, the core portion and the clad portions on both sides thereof are formed in the core layer. Thus, an optical waveguide was obtained.

2. Evaluation Results of Optical Waveguide The light intensity at the emission side end face of each of the optical waveguides obtained in each example and the optical waveguide obtained in the comparative example was measured by the following method.

  FIG. 14 is a diagram for explaining a method of measuring the light intensity at the output-side end face of the optical waveguide. In this method, first, an incident side optical fiber 21 having a diameter of 50 μm was arranged on the light incident side of the optical waveguide 10 to be measured. The incident side optical fiber 21 is connected to a light emitting element (not shown) for entering light into the optical waveguide 10, and the optical axis thereof coincides with the optical axis of the core portion 14 of the optical waveguide 10. Are arranged as follows. The incident side optical fiber 21 can scan the same plane as the core layer 13 along the incident side end face 10 a of the optical waveguide 10. The scanning width is set to 250 μm on both sides around the optical axis of the core portion 14 of the optical waveguide 10.

  On the other hand, an emission side optical fiber 22 having a diameter of 200 μm is disposed on the light emission side of the optical waveguide 10. The emission side optical fiber 22 is connected to a light receiving element (not shown) for receiving the light emitted from the optical waveguide 10, and its optical axis extends from the optical axis of the core portion 14 of the optical waveguide 10 to the side surface. It arrange | positions so that it may be located in the location which shifted | deviated 125 micrometers on the clad part 15 side.

  When measuring the light intensity, if the incident side optical fiber 21 is scanned while emitting light, a part of the light that has passed through the optical waveguide 10 reaches the output side optical fiber 22. Then, by measuring the light intensity incident on the emission side optical fiber 22 at this time, the relationship between the position of the incident side optical fiber 21 and the intensity of the light incident on the emission side optical fiber 22 was evaluated.

  Of these measurement results, those of Example 1 and Comparative Example are shown in FIG. 15 as representative. The horizontal axis of the graph in FIG. 15 represents the position of the incident side optical fiber with respect to the optical axis of the core portion of the optical waveguide, and the vertical axis represents the intensity of light propagating through the core portion of the optical waveguide (incident side light). It represents the light intensity ratio (loss) based on the light intensity when the optical axis of the fiber and the optical axis of the output side optical fiber coincide with the core portion of the optical waveguide.

  As is clear from FIG. 15, in the optical waveguide obtained in the comparative example, the light intensity ratio is particularly large when the incident side optical fiber is at a position near 80 to 200 mm with respect to the optical axis of the core portion of the optical waveguide. It was. From this, it was recognized that in the optical waveguide of the comparative example, the light incident on the side clad portion propagates to the extent that it is hardly different from the core portion.

  On the other hand, the optical waveguide obtained in Example 1 had a small light intensity ratio as a whole. That is, in the optical waveguide of Example 1, it was confirmed that a sufficient S / N ratio was obtained because the light incident on the side cladding portion was greatly attenuated.

  In addition, about the optical waveguide obtained by each Example 2-6, although illustration of the light intensity ratio was abbreviate | omitted, the behavior similar to Example 1 was shown.

1 is a perspective view showing a first embodiment of an optical waveguide of the present invention (partially cut out and shown through). It is a top view which shows only the core layer of the optical waveguide shown in FIG. It is a figure which shows an example of the propagation path of the light which propagates the core layer shown in FIG. It is sectional drawing which shows typically the process example of the manufacturing method of the optical waveguide shown in FIG. It is sectional drawing which shows typically the process example of the manufacturing method of the optical waveguide shown in FIG. It is sectional drawing which shows typically the process example of the manufacturing method of the optical waveguide shown in FIG. It is sectional drawing which shows typically the process example of the manufacturing method of the optical waveguide shown in FIG. It is sectional drawing which shows typically the process example of the manufacturing method of the optical waveguide shown in FIG. It is a top view which shows only the core layer of 2nd Embodiment of the optical waveguide of this invention. It is a top view which shows only the core layer of 3rd Embodiment of the optical waveguide of this invention. It is a figure which shows another structural example of 3rd Embodiment shown in FIG. It is a figure which shows another example of a structure of 3rd Embodiment shown in FIG. It is a top view which shows only the core layer of 4th Embodiment of the optical waveguide of this invention. It is a figure for demonstrating the method to measure the light intensity in the output side end surface of an optical waveguide. It is a graph which shows the relationship between the position of an incident side optical fiber, and the light intensity in an output side end surface about the optical waveguide obtained by Example 1, and the optical waveguide obtained by the comparative example. It is a top view which shows only the core layer of the conventional optical waveguide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical waveguide 10a Incident side end surface 10b Outgoing side end surface 11, 12 Clad layer 13 Core layer 14 Core part 14L Output position of signal light 15 Side clad part 151,153,154,154 ', 154 ", 155 High refractive index area | region 1510 Core side surface 152 Low refractive index region 151L Noise light emission position 17 Light emitting element 18 Light receiving element 100 Core layer forming material (varnish)
110 layer 115 polymer 120 additive 125 irradiation region 130 actinic radiation (active energy ray)
135 Mask 1351 Opening (window)
140 Non-irradiation region 161, 162 Support substrate 21 Incident side optical fiber 22 Emission side optical fiber 90 Optical waveguide 90a Incident side end face 90b Emission side end face 93 Core layer 94 Core part 95 Side clad part 97 Light emitting element 98 Light receiving element

Claims (15)

An optical waveguide comprising a core portion and a cladding portion provided adjacent to the core portion,
In the cladding portion, the refractive index is lower than that of the core portion, the low refractive index region in contact with the core portion, the refractive index is higher than the low refractive index region, and the core is interposed through the low refractive index region. a first high refractive index region and the second high refractive index region spaced from the section has a,
The first high refractive index region is made of the same material as the core portion, and a difference between the refractive index and the refractive index of the low refractive index region is 0.5% or more, and passes through the core portion. A region having a shape in which the cross-sectional area gradually decreases and the distance from the core portion gradually increases as the light travels forward, and is exposed to the light incident side end face of the optical waveguide. And
The second high-refractive index region is a region that has a higher refractive index than the low-refractive index region and has a long shape parallel to the core portion, and the core portion and the first high-refractive index region. An optical waveguide characterized by being positioned from the middle of the core portion to the light emission side between the regions . 2. The optical waveguide according to claim 1 , wherein the second high refractive index region reflects light leaking from the core portion to the low refractive index region and confines the light to the core portion side. An optical waveguide comprising a core portion and a cladding portion provided adjacent to the core portion,
In the cladding portion, the refractive index is lower than that of the core portion, the low refractive index region in contact with the core portion, the refractive index is higher than the low refractive index region, and the core is interposed through the low refractive index region. a first high refractive index region and the third high refractive-index areas separated from the part, has a,
The first high refractive index region is made of the same material as the core portion, and a difference between the refractive index and the refractive index of the low refractive index region is 0.5% or more, and passes through the core portion. A region having a shape in which the cross-sectional area gradually decreases and the distance from the core portion gradually increases as the light travels forward, and is exposed to the light incident side end face of the optical waveguide. And
The third high refractive index region is a region having a refractive index higher than that of the low refractive index region and scattered or aligned in the cladding portion, and the core portion and the first high refractive index region. An optical waveguide characterized by being positioned from the middle of the core portion to the light emitting side . 4. The optical waveguide according to claim 3 , wherein each of the third high refractive index regions refracts light passing through the cladding part in a direction away from the core part or scatters light irregularly. 5. The optical waveguide according to claim 3 or 4, wherein the third high refractive index region has an elongated shape in a plan view. The optical waveguide according to claim 5, wherein a length of a long side of the third high refractive index region is 2 to 50 times a short side. The third high refractive index region is configured such that an axis thereof is inclined rearward in a traveling direction of light passing through the core portion with respect to a perpendicular line of the axis of the core portion. An optical waveguide according to 1. The optical waveguide according to claim 5 or 6, wherein the third high refractive index region is configured such that an axis thereof is orthogonal to an axis of the core portion. The optical waveguide according to claim 5 or 6, wherein the third high-refractive index region has a shape with an uneven contour. The optical waveguide according to any one of claims 1 to 9, wherein the first high refractive index region occupies substantially the entire surface of the optical waveguide on the light incident side where the cladding portion is exposed. The first high refractive index region, the optical waveguide according to any one of claims 1 to 10 and is formed in the same manufacturing process as the core portion. The optical waveguide has a laminate formed by laminating a first layer, a second layer, and a third layer in this order,
A part of the second layer forms the core part,
The remainder of the second layer, the first layer and the third layer, the optical waveguide according to any one of the claims 1 constitutes a cladding portion 11. The optical waveguide according to claim 12 , wherein the first high refractive index region is provided in the second layer. The optical waveguide has a plurality of the core portions and the first high refractive index region provided between the core portions in the second layer,
The first high-refractive index region has a shape that converges to an intermediate portion between two adjacent core portions as it goes forward in the traveling direction of light passing through the core portion. 14. The optical waveguide according to any one of 13 to 13 . The optical waveguide according to any one of claims 1 to 14 , wherein the core portion and at least a part of the clad portion of the optical waveguide are each composed of a norbornene-based polymer as a main material.

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