JP2006243155A - Optical waveguide and its manufacturing method, and optical connecting method of optical parts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide in which optical loss and coupling loss are practically and sufficiently made lower when a photo setting resin is hardened by irradiating it with light beams from one direction to form an optical waveguide and optically connect a plurality of optical parts, and the allowable range of positioning errors of the optical parts is made larger than a conventional case and which is suitable to form an optical propagation path at a low cost. <P>SOLUTION: An optical fiber 1 is mounted onto a substrate 3, a photo setting resin 2 is supplied onto the substrate 3 so that a light emitting surface 12a of the optical fiber 1 is also covered, the optical fiber 1 is irradiated with light beams 4 having the wavelength, to which the photo setting resin 2 responds, so that the resin 2 is partially hardened and a core 5, which has a tapered shape with a taper full angle 2θ, is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical waveguide, a method for manufacturing the same, and an optical connection method for optical components. The optical waveguide of the present invention can be suitably used for optical connection of a plurality of optical components in, for example, an optical integrated circuit, an optical component for optical interconnection, an opto-electric hybrid printed circuit board, and the like.

  The recent development and popularization of electronic devices has shown remarkable progress, but it is also true that there is a demand for higher speed and higher capacity. As a response to such a demand, for example, a technique for mounting an optical transmission line on a printed wiring board has been proposed, and many studies have been made. Since the optical transmission line converts information into light and transmits it, it is clear that the information transmission speed is dramatically increased.

  The optical transmission line usually includes an optical element such as a surface light emitting element and a surface light receiving element, an optical component such as an optical fiber, and an optical waveguide that optically connects a plurality of optical components. In optical transmission lines, it is required to minimize the optical loss that occurs when light propagates and to transmit information accurately. To that end, the optical axes of multiple optical components and optical waveguides must be accurately aligned. It is necessary to match. For example, in order to mount on a printed wiring board, an optical integrated circuit, etc., an alignment accuracy of at least several microns or submicron order is required. Such extremely precise alignment accuracy is one of the problems to be solved in increasing the cost of forming the optical transmission line and spreading the optical transmission line.

  In order to alleviate the alignment accuracy, for example, it is assumed that the optical components that are misaligned are optically connected without aligning and without increasing the coupling loss. As a method for realizing this, a method using a self-forming optical waveguide has been proposed (for example, see Non-Patent Document 1). That is, according to Non-Patent Document 1, a photocurable resin is filled between two optical fibers that are in a misaligned state, and light having a wavelength that the resin is exposed to from the two optical fibers is simultaneously applied to the resin. By irradiating, an optical waveguide is formed. According to this technique, two optical fibers can be connected with a coupling loss of about 1 dB even when there is an optical axis shift of about 30 μm. Since this technique only irradiates light from both sides of the photocurable resin via the optical fiber, optical connection can be realized very simply. However, although it is certainly easy to irradiate light from both sides at the laboratory level, not only optical wiring but also electrical wiring is mounted on an actual printed wiring board, etc., and other optical parts and electrical parts on the board It is often impractical to irradiate light from both sides, which is not realistic.

  In addition, when irradiating light from only one optical fiber toward the photo-curing resin, it is equivalent to the extension of the optical fiber, and the alignment allowable range is the same as when the self-forming optical waveguide is not used. Less than a micron. However, light irradiation from one direction is a technique that can be actually used in mounting an optical transmission path on a printed wiring board or the like. In one optical transmission line, signal light hardly propagates from both sides of the optical component and / or the optical waveguide, and in most optical transmission lines, signal light propagates only in one direction. Therefore, when forming an optical waveguide using a photo-curable resin, a method that can increase the allowable range of alignment only by light irradiation from one direction is desired.

Osamu Ibaraki, “Development of optical and electrical packaging technology in ASET”, Monthly Optronics, July 2004, pp. 182-186, published by Optronics

  An object of the present invention is to make light loss and coupling loss practically sufficient when optically connecting a plurality of optical components by irradiating light from one direction to a photocurable resin and curing it to form an optical waveguide. It is an object of the present invention to provide an optical waveguide that can be made lower and that can further increase the allowable range of alignment of optical components than before, and is suitable for forming an optical transmission line at a low cost, and a method for manufacturing the same.

  As a result of earnest research to solve the above problems, the present inventor forms a plurality of optical components in a tapered shape by forming the core of the optical waveguide in a tapered shape, The present invention was completed by finding that optical connection can be achieved at low cost with low optical loss and low coupling loss.

  That is, the present invention provides an optical waveguide including a core that optically connects a plurality of optical components, and the core has a cross-sectional area perpendicular to the optical axis that increases from the light incident portion toward the light emitting portion, An optical waveguide characterized in that a cross-sectional shape including an optical axis has a tapered shape.

  Furthermore, the optical waveguide of the present invention is characterized in that the core is formed of a cured product of a photocurable resin.

  Furthermore, the optical waveguide of the present invention is characterized in that the core length is 0.1 mm or more and 2 mm or less, and the full taper angle of the core is 1 ° or more.

  Furthermore, the optical waveguide of the present invention is characterized in that the optical component is an optical fiber and / or an optical element.

  The present invention also relates to a method of manufacturing an optical waveguide including a core that optically connects a plurality of optical components, and irradiating light in one direction to an uncured photocurable resin or a solution thereof. Is cured to form a core having a tapered cross-sectional shape including the optical axis.

  Furthermore, in the method for manufacturing an optical waveguide according to the present invention, the cross section perpendicular to the optical axis of the core increases from the light incident portion to the output portion of the core, and the cross sectional shape including the optical axis has a tapered shape. A core is formed.

  Furthermore, the optical waveguide manufacturing method of the present invention forms a tapered core by adjusting the irradiation intensity of light emitted from the emitting part of one optical component toward the incident part of the other optical component. Features.

  According to another aspect of the present invention, there is provided an optical component optical connection method including a core that optically connects a plurality of optical components, wherein the optical component is uncured between an emission portion of one optical component and an incident portion of the other optical component. Including a step of supplying a photocurable resin or a solution thereof, and emitting light from an emitting portion of one optical component toward an incident portion of the other optical component, curing the photocurable resin, and including an optical axis And a step of forming a core having a tapered cross-sectional shape.

  The optical waveguide of the present invention does not require precise alignment of several microns or less of optical components to be optically connected when optically connecting a plurality of optical components due to its shape characteristics. Optical components can be connected easily and at a low cost while suppressing the coupling loss to a practical level.

  The optical waveguide of the present invention can be formed by a simple method of light irradiation from one direction with respect to the photocurable resin.

  FIGS. 1A to 1D are cross-sectional views for explaining a method of manufacturing an optical waveguide according to the first embodiment of the present invention.

  In the method for manufacturing an optical waveguide of the present invention, the optical fiber 1 is used to irradiate the photocurable resin 2 with light for curing the photocurable resin 2. The optical fiber 1 includes a core 12 and a clad 11 formed around the core 12. The optical fiber 1 is not particularly limited, and any one commonly used in this field can be used. For example, a graded index multimode optical fiber having a core 12 having a diameter of 50 μm can be used. Moreover, although the material of the core 12 and the clad | crud 11 is shown as a synthetic resin in FIG. 1, it is not limited to it, Glasses, such as quartz glass, may be sufficient. Further, the air existing around the core 12 may be used as the clad without forming the clad 11. In addition, it is not limited to the optical fiber 1, Other optical components can also be used.

  As the photocurable resin 2, any one commonly used in this field can be used, and examples thereof include acrylic resin, methacrylic resin, urethane resin, epoxy resin, silicone resin, and photosensitive polysilane. Further, the resin is not limited to the above-mentioned resins, and for example, light is applied to a synthetic resin such as polyester, unsaturated polyester, polyvinyl ether, polyvinyl chloride, polycarbonate, polyarylate, polyimide, fluororesin, vinyl acetate resin, alkyd resin, and novolac resin. A photocurable resin having a polymerizable unsaturated group bonded thereto can also be used. Examples of the photopolymerizable unsaturated group include an acryloyl group, a methacryloyl group, a vinyl group, a styryl group, an allyl group, a cinnamoyl group, a cinnamylidene group, and an azide group. These photocurable resins are preferably used in the form of monomers or oligomers and cured by light irradiation. A photosensitizer can be added to such a photocurable resin as necessary. As the photosensitizer, those commonly used in this field can be used. Acetophenones such as isobutylphenone, α, α′-dichloro-4-phenoxyacetophenone, 1-hydroxy-1-cyclohexylacetophenone, diacetylacetophenone, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t- Organic peroxides such as butyl hydroperoxide, di-t-butyldiperoxyisophthalate, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone , Diphenylhalonium salts such as diphenyliodobromide and diphenyliodonium chloride, organic halides such as carbon tetrabromide, chloroform and iodoform, 3-phenyl-5-isoxazolone, 2,4,6-tris (trichloromethyl) Heterocyclic and polycyclic compounds such as 1,3,5-triazinebenzanthrone, 2,2′-azo (2,4-dimethylvaleronitrile), 2,2-azobisisobutyronitrile, Examples include azo compounds such as 1′-azobis (cyclohexane-1-carbonitrile) and 2,2′-azobis (2-methylbutyronitrile), and sulfonium salts, osmium salts, rhodamine 6G, and the like. The photosensitizer can be used alone or in combination of two or more. The photocurable resin 2 is usually in the form of a solution obtained by mixing a general photocurable resin and a photosensitizer in an organic solvent or a resin composition obtained by evaporating a part or all of the organic solvent from the solution. Used. Here, as an organic solvent, what can melt | dissolve or disperse | distribute a photocurable resin and a photosensitive agent as needed can be selected suitably. As long as it is a liquid photocurable resin, a photosensitizer may be added and mixed therewith. As a specific example of the photocurable resin 2, for example, an acrylic photocurable resin (acrylic ultraviolet curable resin) and rhodamine 6G sensitive to light having a wavelength of 532 nm are dissolved in an organic solvent to prepare a solution. And a resin composition obtained by evaporating an organic solvent from this solution. Here, examples of the organic solvent include lower alcohols such as ethanol.

  In the method of manufacturing an optical waveguide according to the present invention, as shown in FIG. 1B, the emitting portion side of the optical fiber 1 is placed on the substrate 3, and the photocurable resin 2 is dropped on the substrate 3. To do. The photocurable resin 2 is dropped on the substrate 3 so as to cover the light emitting surface 12 a of the optical fiber 1. Here, it does not restrict | limit especially as the board | substrate 3, For example, a glass plate, a resin plate, a metal plate, a silicon substrate etc. can be used. Of course, the manufacturing method of the present invention can be carried out without using the substrate 3.

  Next, as shown in FIG. 1 (c), the photocurable resin and / or the photosensitive agent contained in the photocurable resin 2 is exposed to the light emitting portion side of the optical fiber 1, and the photocurable resin 2 is cured. A laser beam 4 having a wavelength is inserted and irradiated toward the photocurable resin 2. When the photocurable resin 2 is, for example, a mixture of an acrylic photocurable resin and rhodamine 6G, green laser light with a wavelength of 532 nm is irradiated.

  Further, as shown in FIG. 1D, the core 5 is formed by the irradiation of the laser beam 4. The core 5 is formed such that the area of the cross section perpendicular to the optical axis increases from the light incident portion toward the output portion, and the cross-sectional shape including the optical axis has a tapered shape. In other words, the tapered core 5 is formed in which the core diameter on the light exit side is larger than the core diameter on the light incident side.

  The taper full angle of the core 5 is preferably 1 ° or more, more preferably 1 ° or more and 20 ° or less, and more preferably 1 ° or more and 12 ° or less. In this specification, the taper full angle is a value twice the taper angle θ. Here, the taper angle θ is an angle formed by the outline 6 that forms a cross section in the vertical (vertical) direction including the optical axis of the core 5 and the parallel movement line 7 of the optical axis of the core 5. If the taper full angle is less than 1 °, the outline 6 of the core 5 becomes a straight line parallel to the optical axis, and the alignment accuracy of the optical component cannot be relaxed. The shape of the core 5 and the full taper angle are affected by the numerical aperture of the optical fiber 1 and the light irradiation intensity. For example, when the numerical aperture of the optical fiber 1 is constant, it is desirable that the light irradiation intensity is large. In general, when the irradiation intensity is weak, the taper shape is not formed by the self-condensing effect, and the core 5 has a rectangular parallelepiped shape. Therefore, the irradiation intensity is appropriately selected according to the type of photocurable resin contained in the photocurable resin 2, the type of photosensitive agent, the amount added, and the like. It is preferable to previously determine the light irradiation intensity at which the core 5 does not have a rectangular parallelepiped shape by experiments.

  As the photocurable resin 2, for example, when using a photocurable resin composition obtained by adding rhodamine 6G at a concentration of about 100 ppm to an acrylic photocurable resin, the core 5 has a rectangular parallelepiped shape with an irradiation intensity of 5 mW or less. When light having an irradiation intensity greater than 5 mW is irradiated, the core 5 having a taper full angle of 1 ° or more is formed.

  The core length of the core 5 is preferably 0.1 mm or more and 2 mm or less. If it is less than 0.1 mm, the light emitted from the optical component such as the optical fiber 1 is used, so that the shape of the core 5 does not easily become a tapered shape. On the other hand, if it exceeds 2 mm, a bent portion is generated in the core 5, and there is a possibility that light loss at that portion becomes large.

  FIG. 2A is a cross-sectional view schematically showing the configuration of the optical transmission line 10 formed by the optical component connecting method of the present invention. FIG. 2B is a perspective view showing an appearance of the optical transmission line 10 shown in FIG.

  The optical transmission line 10 includes optical fibers 1 and 21 and an optical waveguide 24 including a core 22 that optically connects the optical fibers 1 and 21.

  The optical fibers 1 and 21 have the same core diameter (50 μm), and are arranged on the substrate 3 so that the emission surface 12a of the optical fiber 1 and the incident surface 21a of the optical fiber 21 face each other and are spaced by, for example, 0.5 mm. Placed on.

  The core 22 is made of a cured product by light irradiation of a photocurable resin, and has a tapered shape in which the core diameter (cross-sectional diameter in a direction perpendicular to the optical axis) continuously increases from the incident portion to the emission portion in the core 22. The taper full angle is 1 ° or more. That is, in the core 22, the core diameter at the contact surface with the optical fiber 1 is substantially the same as the core diameter of the core 12 of the optical fiber 1, but the core diameter increases as the distance from the optical fiber 21 increases. The core diameter at the contact surface with 21 is substantially the same as the diameter of the optical fiber 21. Therefore, even if there is a deviation of about 10 to 20 μm in the optical fibers 1 and 21, if the tapered core 22 is formed as in the present invention, the alignment between the cores of the optical fibers 1 and 21 can be achieved without performing alignment. An optical connection can be surely made. For example, when the signal propagation light 23 is inserted from the side of the optical fiber 21 having the larger core diameter of the core 22 and received by the side of the optical fiber 1 having the smaller core diameter, the alignment tolerance is increased as compared with a straight or rectangular parallelepiped optical waveguide. I can do it.

  The core length of the core 22 is preferably 0.1 mm or more and 2 mm or less as described above. Here, the core length means the length of the optical axis from the contact surface of the core 22 with the output surface 12a of the optical fiber 1 to the contact surface with the output surface 21a of the optical fiber 21.

  The present invention will be specifically described below with reference to examples and comparative examples. It is not clear that the polymer optical waveguide of the present invention can be obtained by using various polymer solutions having different molecular structures. Therefore, the present invention is not limited only to these examples.

Example 1
1 g of acrylic UV curable resin (trade name: MH7623, manufactured by Mitsubishi Rayon Co., Ltd.) and 0.1 g of rhodamine 6G dissolved in 0.1 g of ethanol are mixed, and the ethanol is evaporated from the mixture to produce an optical waveguide. A resin composition was prepared.

  On the other hand, two graded index multimode optical fibers (core diameter 50 μm) are mounted on a glass slide with an interval of 0.5 mm so that one exit surface and the other entrance surface face each other. I put it. At this time, the optical axes of both were previously aligned by active alignment. 2 g of the resin composition for producing an optical waveguide is dropped into the space between the two optical fibers, a green laser beam having a wavelength of 532 nm is inserted into one of the optical fibers, and the light intensity (irradiation intensity) at the output end of the optical fiber is 16 mW. When the optical waveguide forming resin was irradiated for 10 seconds, the two optical fibers were optically connected by the optical waveguide including the core.

  The core diameter on the green laser light incident side of the core was 43 μm, and the core diameter on the emission side was 81 μm. The taper full angle of the core was about 4 °. A laser beam with a wavelength of 850 nm was inserted into an optical fiber connected to the output side of the core, and the optical loss was measured. The result was 2 dB. In this case, air becomes a clad, and the optical waveguide includes the core and air (clad).

  Next, in the optical transmission line 10 shown in FIG. 2B, the core 22 and the optical fiber 21 on the side where the core diameter of the core 22 is increased are coated in advance with a release agent on the optical fiber 21 side. 22 is deviated from the end face of the optical fiber 21, and the optical axis of the optical fiber 21 is shifted in advance by 5 μm in the + X axis direction or the −X axis direction in FIG. Formed and the coupling loss was measured. As a result, the positional deviation at which the coupling loss was 3 dB was ± 16 μm.

(Example 2)
In the same manner as in Example 1 except that one of the two optical fibers is installed by shifting by 10 μm from the axis connecting the two fibers in the + X axis direction shown in FIG. 2B, between the two optical fibers, Optical connection was made by an optical waveguide including a core. The core diameter on the green laser beam incident side of the core was 43 μm, and the core diameter on the emission side was 81 μm. The taper full angle of the core was about 4 °.

  Next, after unabsorbing the uncured resin with a cotton swab, an acrylic ultraviolet curable resin having a refractive index lower than that of the core was filled and cured by irradiating with ultraviolet rays to form a clad. A laser beam with a wavelength of 850 nm was inserted into an optical fiber connected to the output side of the core, and the optical loss was measured to be 2.5 dB. Thus, it was found that the optical loss remained at a low value of 2.5 dB even when shifted by 10 μm from the axis connecting the two optical fibers.

(Comparative Example 1)
Two optical fibers were optically connected by an optical waveguide including a core in the same manner as in Example 1 except that the amount of light was 1 mW and the irradiation time was 20 seconds. The core diameters of the green laser beam incident side and the emitting side in the core were both 43 μm. Further, when the coupling loss was measured in the same manner as in Example 1, it was 2 dB.

  Next, in the optical transmission line 10 shown in FIG. 2B, the core 22 and the optical fiber 21 on the side where the core diameter of the core 22 is increased are coated in advance with a release agent on the optical fiber 21 side. 22 is deviated from the end face of the optical fiber 21, and the optical axis of the optical fiber 21 is shifted in advance by 5 μm in the + X axis direction or the −X axis direction in FIG. Formed and subjected to coupling loss measurements. As a result, the positional deviation at which the coupling loss was 3 dB was ± 7 μm.

  From the above results, it can be seen that by using the tapered optical waveguide of the present invention, the positional deviation allowable range is expanded by ± 9 μm.

FIGS. 1A to 1D are cross-sectional views for explaining a method of manufacturing an optical waveguide according to the first embodiment of the present invention. FIG. 2A is a cross-sectional view schematically showing the configuration of the optical transmission line 10 formed by the optical component connecting method of the present invention. FIG. 2B is a perspective view showing an appearance of the optical transmission line shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,21 Optical fiber 2 Photocurable resin 3 Board | substrate 4 Laser beam 5, 12, 22 Core 6 Contour line 7 Optical axis parallel displacement line 10 Optical transmission path 11 Cladding 12a Outgoing surface 21a Incident surface 23 Signal propagation light 24 Optical waveguide

Claims (8)

In an optical waveguide including a core that optically connects a plurality of optical components,
The core is formed such that an area of a cross section perpendicular to the optical axis increases from the light incident portion toward the light emitting portion, and the cross-sectional shape including the optical axis has a tapered shape. Optical waveguide.   The optical waveguide according to claim 1, wherein the core is formed of a cured product of a photocurable resin.   The optical waveguide according to claim 1 or 2, wherein the core length is 0.1 mm or more and 2 mm or less, and the taper full angle of the core is 1 ° or more.   The optical waveguide according to any one of claims 1 to 3, wherein the optical component is an optical fiber and / or an optical element. In a method of manufacturing an optical waveguide including a core that optically connects a plurality of optical components,
An uncured photocurable resin or a solution thereof is irradiated with light in one direction to cure the photocurable resin to form a core having a tapered cross section including the optical axis. Manufacturing method of optical waveguide.   The core is formed so that a cross section perpendicular to the optical axis of the core increases from a light incident portion to an output portion in the core, and the cross-sectional shape including the optical axis has a tapered shape. 5. A method for producing an optical waveguide according to 5.   7. The light guide according to claim 5, wherein a tapered core is formed by adjusting an irradiation intensity of light emitted from an emission portion of one optical component toward an incidence portion of the other optical component. A method for manufacturing a waveguide. In an optical connecting method of an optical component including a core for optically connecting a plurality of optical components,
Supplying an uncured photocurable resin or a solution thereof between the exit portion of one optical component and the entrance portion of the other optical component;
A step of emitting light from the emitting portion of one optical component toward the incident portion of the other optical component, curing the photocurable resin, and forming a core having a tapered cross section including the optical axis; An optical connection method for an optical component comprising:

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