Method of coupling optical parts and refractive index imaging material

What is claimed is:

1. A method of coupling optical parts comprising the steps of:

relatively movably retaining first and second optical parts;

facing optical coupling faces of waveguides of the first and second optical parts with each other and at least partially aligning a part of one optical coupling face with a part of the other optical coupling face; and

fusing the optical coupling faces of the first and second optical parts and bonding them to each other,

wherein the optical coupling face of at least one of the first and second optical parts and the non-coupling face around the optical coupling face are different in hydrophilic and hydrophobic properties.

2. A method of coupling optical parts comprising the steps of:

fixing edges of two optical parts separately from each other;

feeding a refractive-index imaging material having a function serving as an adhesive and forming a refractive-index distribution according to the intensity of light in a specified wave range to the gap between the edges of the two optical parts; and

forming a refractive-index distribution with a focusing lens effect by applying the light in the specified wave range to the refractive-index imaging material from the edge of at least one of the two optical parts.

3. A method of coupling optical parts according to claim 2, wherein the optical parts includes any one of an optical fiber, semiconductor laser, light-emitting diode, photodiode, and semiconductor light amplifier.

4. A method of coupling optical parts according to claim 2, wherein a step of curing the refractive-index imaging material by applying light to or heating the material is included.

5. A method of coupling optical parts according to claim 2, wherein the interval between the optical parts to be coupled is set to 0.1 mm or more.

6. The method of coupling optical parts according to claim 2, wherein the refractive-index imaging material comprises:

a binder consisting of one of a copolymer having alicyclic epoxy, chain epoxy, organic denatured silicone, and ethylene unsaturated compound having a hydroxyl group in one end in the building block of the copolymer and a copolymer having any one of ethylene unsaturated compounds containing silicone in the building block of the copolymer;

a photosensitive monomer made of a mixture including multifunctional acrylate or multifunctional methacrylate and an ethylene unsaturated monomer containing an aromatic ring or halogen; and a photopolymerization initiator.

7. The method of coupling optical parts according to claim 2, wherein the refractive-index imaging material comprises an alicyclic or chain compound having an epoxy group, an ethylene unsaturated compound containing an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and photopolymerization initiator.

8. The method of coupling optical parts according to claim 2, wherein the refractive-index imaging material comprises organic denatured silicone, an ethylene unsaturated compound containing any one of an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and a photopolymerization initiator.

9. The method of coupling optical parts according to claim 2, wherein the refractive-index imaging material comprises:

a copolymer solution obtained by dissolving an ethylene unsaturated compound whose general expression is shown as "R.sub.1 CH=CHCOOR.sub.2 " in which R.sub.1 is any one of CH.sub.3 and H and R.sub.2 is a chain or alicyclic compound group with carbon atoms of 1 to 4, an ethylene unsaturated compound containing silicone, and thermopolymerization initiator in an solvent and heating and agitating the dissolved substances;

an ethylene unsaturated compound containing an aromatic ring or halogen to be added into the copolymer solution cooled up to the room temperature;

multifunctional acrylate or multifunctional methacrylate to be added to the copolymer solution cooled up to the room temperature; and

a photopolymerization initiator to be added to the copolymer solution cooled up to the room temperature.

10. The method of coupling optical parts according to claim 2, wherein the refractive-index imaging material comprises:

a copolymer solution obtained by dissolving an ethylene unsaturated compound whose general expression is shown as "R.sub.1 CH=CHCOOR.sub.2 " in which R.sub.1 is any one of CH.sub.3 and H and R.sub.2 is a chain or alicyclic compound group with carbon atoms of 1 to 4, an ethylene unsaturated compound containing silicone, any one of multifunctional acrylate and multifunctional methacrylate, and thermopolymerization initiator in an solvent and heating and agitating the dissolved substances;

an ethylene unsaturated compound containing an aromatic ring or halogen to be added into the copolymer solution cooled up to the room temperature;

multifunctional acrylate or multifunctional methacrylate to be added to the copolymer solution cooled up to the room temperature; and

a photopolymerization initiator to be added to the copolymer solution cooled down to room temperature.

11. The method of coupling optical parts according to claim 2, wherein the refractive-index imaging material for forming a refractive-index distribution by applying light in a specified wave range comprises a thermosetting copolymer containing acrylate or methacrylate having a hydroxyl group at its end in the building block of the copolymer, an ethylene unsaturated compound containing an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and a photopolymerization initiator.

12. A method of coupling optical parts comprising the steps of:

feeding a refractive-index imaging material which has a function serving as an adhesive for optical parts and whose refractive-index increases according to the intensity of light in a specified wave range onto a support;

mounting two optical parts on the support by facing the edges of the two optical parts each other through the refractive-index imaging material; and

forming a refractive-index distribution having a focusing lens effect by applying light in the specified wave range to the refractive-index imaging material from the edge of at least one of the two optical parts.

13. The method of coupling optical parts according to claim 12, wherein the refractive-index imaging material comprises:

a binder consisting of one of a copolymer having alicyclic epoxy, chain epoxy, organic denatured silicone, and ethylene unsaturated compound having a hydroxyl group in its end in the building block of the copolymer and a copolymer having any one of ethylene unsaturated compounds containing silicone in the building block of the copolymer;

a photosensitive monomer made of a mixture including multifunctional acrylate or multifunctional methacrylate and an ethylene unsaturated monomer containing an aromatic ring or halogen; and a photopolymerization initiator.

14. A method of coupling optical parts according to claim 12, wherein the optical parts includes any one of an optical fiber, waveguide, semiconductor laser, light-emitting diode, photodiode, and semiconductor light amplifier.

15. A method of coupling optical parts according to claim 12, further comprising a step of curing the refractive-index imaging material by applying light to or heating the material.

16. A method of coupling optical parts according to claim 12, wherein the interval between the optical parts to be coupled is set to 0.1 mm or more.

17. The method of coupling optical parts according to claim 12, wherein the refractive-index imaging material comprises an alicyclic or chain compound having an epoxy group, an ethylene unsaturated compound containing an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and photopolymerization initiator.

18. The method of coupling optical parts according to claim 12, wherein the refractive-index imaging material comprises organic denatured silicone, an ethylene unsaturated compound containing any one of an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and a photopolymerization initiator.

19. The method of coupling optical parts according to claim 12, wherein the refractive-index imaging material comprises:

a copolymer solution obtained by dissolving an ethylene unsaturated compound whose general expression is shown as "R.sub.1 CH=CHCOOR.sub.2 " in which R.sub.1 is any one of CH.sub.3 and H and R.sub.2 is a chain or alicyclic compound group with carbon atoms of 1 to 4, an ethylene unsaturated compound containing silicone, and thermopolymerization initiator in an solvent and heating and agitating the dissolved substances;

an ethylene unsaturated compound containing an aromatic ring or halogen to be added into the copolymer solution cooled up to the room temperature;

multifunctional acrylate or multifunctional methacrylate to be added to the copolymer solution cooled up to the room temperature; and

a photopolymerization initiator to be added to the copolymer solution cooled up to the room temperature.

20. The method of coupling optical parts according to claim 12, wherein the refractive-index imaging material comprises:

a copolymer solution obtained by dissolving an ethylene unsaturated compound whose general expression is shown as "R.sub.1 CH=CHCOOR.sub.2 " in which R.sub.1 is any one of CH.sub.3 and H and R.sub.2 is a chain or alicyclic compound group with carbon atoms of 1 to 4, an ethylene unsaturated compound containing silicone, any one of multifunctional acrylate and multifunctional methacrylate, and thermopolymerization initiator in an solvent and heating and agitating the dissolved substances;

an ethylene unsaturated compound containing an aromatic ring or halogen to be added into the copolymer solution cooled up to the room temperature;

multifunctional acrylate or multifunctional methacrylate to be added to the copolymer solution cooled up to the room temperature; and

a photopolymerization initiator to be added to the copolymer solution cooled up to the room temperature.

21. The method of coupling optical parts according to claim 12, wherein the refractive-index imaging material for forming a refractive-index distribution by applying light in a specified wave range comprises a thermosetting copolymer containing acrylate or methacrylate having a hydroxyl group at its end in the building block of the copolymer, an ethylene unsaturated compound containing an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and a photopolymerization initiator.

22. A method of coupling optical parts comprising the steps of:

attaching a refractive-index imaging material which has a function serving as an adhesive for optical parts and whose refractive index increases according to the intensity of light in a specified wave range to the edge of a first optical part on a support; and

forming a refractive-index distribution having a focusing lens effect by applying the light in the specified wave range from at least one of the edge of the second optical part facing that of the first optical part and the edge of the first optical part.

23. A method of coupling optical parts according to claim 22, wherein the optical parts includes any one of an optical fiber, waveguide, semiconductor laser, light-emitting diode, photodiode, and semiconductor light amplifier.

24. A method of coupling optical parts according to claim 2, further comprising a step of curing the refractive-index imaging material by applying light to or heating the material.

25. A method of coupling optical parts according to claim 22, wherein the interval between the optical parts to be coupled is set to 0.1 mm or more.

26. The method of coupling optical parts according to claim 22, wherein the refractive-index imaging material comprises:

a binder consisting of one of a copolymer having alicyclic epoxy, chain epoxy, organic denatured silicone, and ethylene unsaturated compound having a hydroxyl group in its end in the building block of the copolymer and a copolymer having any one of ethylene unsaturated compounds containing silicone in the building block of the copolymer;

a photosensitive monomer made of a mixture including multifunctional acrylate or multifunctional methacrylate and an ethylene unsaturated monomer containing an aromatic ring or halogen; and

a photopolymerization initiator.

27. The method of coupling optical parts according to claim 22, wherein the refractive-index imaging material comprises an alicyclic or chain compound having an epoxy group, an ethylene unsaturated compound containing an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and photopolymerization initiator.

28. The method of coupling optical parts according to claim 22, wherein the refractive-index imaging material comprises organic denatured silicone, an ethylene unsaturated compound containing any one of an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and a photopolymerization initiator.

29. The method of coupling optical parts according to claim 22, wherein the refractive-index imaging material comprises:

a copolymer solution obtained by dissolving an ethylene unsaturated compound whose general expression is shown as "R.sub.1 CH=CHCOOR.sub.2 " in which R.sub.1 is any one of CH.sub.3 and H and R.sub.2 is a chain or alicyclic compound group with carbon atoms of 1 to 4, an ethylene unsaturated compound containing silicone, and thermopolymerization initiator in an solvent and heating and agitating the dissolved substances;

an ethylene unsaturated compound containing an aromatic ring or halogen to be added into the copolymer solution cooled up to the room temperature;

multifunctional acrylate or multifunctional methacrylate to be added to the copolymer solution cooled up to the room temperature; and

a photopolymerization initiator to be added to the copolymer solution cooled up to the room temperature.

30. The method of coupling optical parts according to claim 22, wherein the refractive-index imaging material comprises:

a copolymer solution obtained by dissolving an ethylene unsaturated compound whose general expression is shown as "R.sub.1 CH=CHCOOR.sub.2 " in which R.sub.1 is any one of CH.sub.3 and H and R.sub.2 is a chain or alicyclic compound group with carbon atoms of 1 to 4, an ethylene unsaturated compound containing silicone, any one of multifunctional acrylate and multifunctional methacrylate, and thermopolymerization initiator in an solvent and heating and agitating the dissolved substances;

an ethylene unsaturated compound containing an aromatic ring or halogen to be added into the copolymer solution cooled up to the room temperature;

multifunctional acrylate or multifunctional methacrylate to be added to the copolymer solution cooled up to the room temperature; and

a photopolymerization initiator to be added to the copolymer solution cooled up to the room temperature.

31. The method of coupling optical parts according to claim 22, wherein the refractive-index imaging material for forming a refractive-index distribution by applying light in a specified wave range comprises a thermosetting copolymer containing acrylate or methacrylate having a hydroxyl group at its end in the building block of the copolymer, an ethylene unsaturated compound containing an aromatic ring or halogen, multifunctional acrylate or multifunctional methacrylate, and a photopolymerization initiator.

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of coupling optical parts and refractive-index imaging material, particularly to a method for coupling optical parts such as optical waveguides and optical devices in optical communication and optical interconnection and to a material used for coupling the optical parts.

2. Description of the Related Art

Optical parts are used for various optical information processing systems including optical interconnection and optical communication. For example, light emitted from a light source such as a semiconductor laser is transmitted through a waveguide or optical fiber and the transmitted light is changed into electric signals by a photodiode.

A high coupling efficiency is requires for optical coupling between optical parts. To obtain a high coupling efficiency, it is necessary to completely align optical electromagnetic fields between optical parts. Therefore, it is necessary to equalize the diameters of optical coupling faces at a joint between the optical parts and minimize optical axis misalignment and angular misalignment of the optical parts. To realize this, it is necessary to accurately align the coupling faces between optical parts. However, it is not easy to improve the alignment accuracy. Therefore, a method for easily and efficiently optically-coupling optical parts such as optical fibers and optical devices is desired.

FIGS. 1(a) to 1(c) show a general step for optical-coupling two optical fibers.

These optical fibers 1 and 2 have a structure in which cores 1a and 2a are enclosed by cladding 1b and 2b and the cores 1a and 2a have larger refractive index than the cladding 1b and 2b.

To optically couple the optical fibers 1 and 2, as shown in FIG. 1(a), the optical fiber 2 is secured to a fiber securing portion 3 and the optical fiber 1 is set to a mobile stage 4. Then, an operator moves the mobile stage 4 while observing it with a microscope 5 to accurately align the edge of the core 2a of the optical fiber 2 with that of the core 1a of the optical fiber 1 as shown in FIG. 1(b). After the alignment is completed, the joint between the optical fibers 1 and 2 is welded with an arc discharge apparatus 6.

However, the above method for optically coupling optical parts has a problem that optical coupling between optical parts cannot easily be performed because it is necessary to previously perform accurate alignment.

A measure for solving the above problem is desired for optical coupling between optical fibers or a coupler for optically coupling a light-emitting device or light-detecting device with an optical fiber or optical waveguide.

To accurately couple optical parts, Japanese Patent Laid-Open Nos. Sho. 53-108452 and Sho. 64-6909 disclose a method for melting the edges of two optical fibers and coupling them by the surface tension. However, these prior art references only disclose the coupling between optical fibers but do not disclose the coupling between other optical parts.

Moreover, accurate optical coupling between optical parts is considered by using couplers.

These couplers are described in the following documents.

[1] Optical Communication Device Optics--Light-Emitting and Light-Detecting Devices Hiroo Yonezu, Kogakutosho, Japan

[2] Optical Fiber Technology In ISDN Age, Katsuhiko Okubo, Rikogakusha, Japan

[3] Optical Communication Handbook, Edited by Hiroshi Hirayama et al., Kagakushinbunsha, Japan

These documents show that an edge emitting laser has a rectangular structure with an active layer of approximately hundreds of nanometers by several microns and its radiation angle ranges between 20.degree. and 60.degree. in the vertical direction and between 5.degree. and 20.degree. in the horizontal direction. A surface emitting LED has a large emitting region diameter of 30 to 40 .mu.m and a radiation angle of approximately 120.degree..

In this connection, a single-mode optical fiber has a core diameter of several to 10 microns and a multiple-mode optical fiber has a core diameter of several tens of microns. Therefore, to couple an optical semiconductor device with an optical fiber, accurate alignment along the order of 1-micron is desirable to decrease the coupling loss.

When accurately aligning and directly coupling a light-emitting device with an optical fiber by contacting the edge of the device with that of the fiber, more specifically, for direct coupling of an edge emitting laser with a single-mode optical fiber, the coupling efficiency approaches 30%. For direct coupling of the edge emitting laser with a multiple-mode optical fiber, the coupling efficiency approaches 50%. For direct coupling of a surface emitting LED with the multiple-mode optical fiber, the coupling efficiency approaches approximately 6%.

A method for setting a lens between an edge emitting laser and single-mode optical fiber has been proposed as a method for coupling the laser with the fiber. In this case, the coupling efficiency is approximately 50%. However, optical coupling becomes further difficult because the number of parts requiring accurate alignment increases.

For direct coupling of an optical fiber with a waveguide, a coupling efficiency of 56 to 79% is obtained by equalizing the core diameter of the waveguide edge diameter with that of the optical fiber and preventing misalignment of axes.

However, there is a problem that the direct coupling of the waveguide with the optical fiber is not easy because the core diameters of the waveguide and optical fiber are limited and accurate alignment at 1 .mu.m order is desired.

Moreover, a method different from the above direct coupling and lens coupling methods is proposed. In Japanese Patent Laid-Open Nos. Sho. 55-43538 and Sho. 60-173508, it is proposed to use a material whose refractive index changes by applying light to the material.

However, the optical coupler connection method proposed in Laid-Open No. Sho. 55-43538 includes a method for manufacturing an optical coupler characterized by applying light to the optical coupler substrate made of a material whose refractive index changes proportionally to a light intensity from a position where light should be inputted or outputted and changing the refractive index of the optical coupler substrate so as to form an optical waveguide in self-alignment. To use the optical coupler, it is necessary to arrange and secure optical parts including optical fibers to be coupled by the optical coupler. Therefore, for example, a hole for inserting an optical fiber is formed on the optical coupler.

In Laid-Open No. Sho. 60-173508, an optical waveguide connection method is proposed which is characterized by setting a phase-change-type photosensitive medium material between two waveguides facing each other, applying light to the photosensitive medium material from the both waveguides, and locally denaturalizing the photosensitive medium so as to form a waveguide for optical coupling.

This reference purposes to set a photosensitive medium material between waveguides to be mutually connected, form a waveguide for optical coupling in it, and thereby decrease a loss due to misalignment of optical axes and it is preferable to set the interval between waveguides to 0.1 mm or less and use ultraviolet rays as the light to be applied to the photosensitive medium material. As a result, though the light spreads due to diffraction in the photosensitive medium material, a waveguide for coupling with a small spread is formed. The optical coupling disclosed in the laid-open official this reference uses connection between waveguides formed in the photosensitive medium and misalignment between waveguides to be connected is also taken over between waveguides in the photosensitive medium. Therefore, it is impossible to correspond to a large misalignment exceeding a core diameter.

The following materials can be used for the optical coupler.

For example, gazette Laid-Open No. Sho. 55-43538 mentioned above discloses that a chalcogenide-based amorphous semiconductor or macromolecular material containing photopolymerizable monomer is used for the optical coupler and Laid-Open No. Sho. 60-173508 discloses that the photopolymer made by DU PONT LIMITED, Photoresist KPR (trade name) made by KODAK LOMITED, and U.V. 57 (trade name) made by OPTION CHEMICAL LIMITED are known.

The following are refractive-index imaging materials whose refractive indexes change by applying light to them.

For example, Japanese Patent Laid-Open No. Hei. 2-3081 discloses a material made of thermoplastic polymers, ethylene-based unsaturated monomers, and polymerization initiator. Japanese Patent Laid-Open No. Hei. 2-3082 discloses a material made of interpolymers containing such segments as polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, and polyvinyl formal as the main part, or made of polymerizable binder selected among groups made of the mixture of the segments, ethylene-based unsaturated monomers, and an optical initiator. Japanese Patent Laid-Open No. Hei. 3-50588 discloses a material made of solvent-soluble fluorine-contained polymerizable binder, ethylene-based unsaturated monomers, and a photopolymerization initiator. Moreover, Japanese Patent Laid-Open No. Hei. 3-36582 discloses a material made of allyl diglycol carbonate, 2,2,-bis{3,5-dibromo-4-(2-mathasryroiloxiethoxy)phenyl} propane, and a photopolymerization initiator.

However, these materials have a low heat resistance because they use thermoplastic resin and methacryroil-based polymeric products as a binder.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an optical part coupling method for simplifying optical coupling between optical parts and improving optical coupling efficiency and also to provide a refractive-index imaging material used for optical coupling.

According to the present invention, a first optical waveguide is coupled with a second optical waveguide by relatively movably retaining the waveguides, facing the optical coupling faces of the waveguides with each other, and fusing the optical coupling faces of the waveguide to each other.

When the optical coupling faces of the first and second optical waveguides are fused, surface tension works on the fused portions. In this case, because the first and second optical waveguides are relatively movably retained, the first and second optical waveguides relatively move each other by the fact that the surface tension works on the fused portions.

Because the surface tension works so as to minimize the surface area of a fused object in general, the first and second optical waveguides move in the direction in which the surface areas of the fused portions of the waveguides are minimized. As a result, the waveguides are coupled under the state in which the optical axes of the waveguides are almost completely aligned and the optical coupling efficiency is maximized.

According to another aspect of the present invention, optical parts are optically coupled with each other by securing the coupling faces of optical parts so that the parts face each other at an interval, feeding an adhesive refractive-index imaging material between the optical parts, applying light to the material from at least one of the parts, and thereby forming a refractive index distribution having the beam-condensing lens effect.

To form the beam-condensing refractive-index distribution, it is necessary to keep the distance between the optical parts at 0.1 mm or more. This condition is contrary to the condition preferred to form a waveguide disclosed in Japanese Patent Laid-Open No. Sho. 60-173508. It is desirable to use a long-wavelength light for the light for forming a refractive index in order to increase the spread of a beam after emitted from the optical part. However, it is easier to increase the distance between the optical parts because the spread of the beam is also limited depending on a characteristic such as the photosensitive wavelength zone of the refractive-index imaging material.

Thus, the coupling efficiency between the optical parts is improved by a refractive-index imaging material, a high accuracy is not needed for alignment of the parts, and the yield is improved. Moreover, because the optical parts to be coupled are secured and the refractive-index imaging material is supplied before the refractive-index distribution is formed by using the light emitted from the optical part, the refractive-index distribution is formed in self-alignment in accordance with the positions where the optical parts are secured. Therefore, the optical parts can be secured by rough alignment and moreover, the labor for forming optical fiber inserting holes to arrange and secure the devices to be coupled is unnecessary.

According to still another aspect of the present invention, alicyclic epoxy, chain epoxy, organic denatured silicone, and copolymer having an ethylene unsaturated compound having a hydroxyl group at the end in its building block or copolymer having an ethylene unsaturated compound containing silicone in its building block are used as the binder constituting the refractive-index imaging material used for optical coupling of optical parts. Moreover, a mixture having multifunctional acrylate or multifunctional methacrylate and an ethylene unsaturated monomer containing aromatic rings or halogen are used as the optical reaction monomer constituting the refractive-index imaging material. Furthermore, an optical initiator is contained in the refractive-index imaging material.

The above refractive-index imaging material is able to form a refractive-index distribution only by applying light and moreover, able to core by heating a binder compound of applying light because a compound having the above reactive group can be used as a binder, and has a high durability. Furthermore, when using the refractive-index imaging material, a refractive-index distribution having a lens effect of a high refractive index is formed in accordance with a light intensity because the monomer density in the region where monomers are polymerized by applying light with a certain wavelength increases. After optical devices are coupled by using the refractive-index imaging material and a refractive-index distribution having a lens effect is formed by applying light from the optical devices, unreacted monomers in the material react by either light application or heating.

By using the above coupling method and refractive-index imaging material, optical parts are efficiently coupled by rough alignment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) to 1(c) are side views showing an existing optical coupling method;

FIGS. 2(a) and 2(b) and 3(a) and 3(b) are side views showing the steps of the optical coupling method of the first embodiment of the present invention;

FIG. 4 is a side view showing the optical coupling method of the second embodiment of the present invention;

FIG. 5 is a side view showing the initial state of the optical coupling method of the third embodiment of the present invention;

FIG. 6 is a perspective view showing the initial state of the optical coupling method of the third embodiment of the present invention;

FIGS. 7(a) to 7(c) are side views showing the steps of the optical coupling method of the third embodiment of the present invention;

FIG. 8 is a side view showing the initial state of the optical coupling method of the fourth embodiment of the present invention;

FIGS. 9(a) to 9(d) are side views showing the steps of the optical coupling method of the fourth embodiment of the present invention;

FIG. 10 is a side view showing the optical coupling method of the fifth embodiment of the present invention;

FIG. 11 is a perspective view showing the initial state of the optical coupling method of the sixth embodiment of the present invention;

FIGS. 12(a) to 12(c) are side views showing the steps of the optical coupling method of the sixth embodiment of the present invention;

FIG. 13 is a perspective view showing the initial state of the optical coupling method of the seventh embodiment of the present invention;

FIGS. 14(a) to 14(d) are side views showing the steps of the optical coupling method of the seventh embodiment of the present invention;

FIG. 15(a) is a perspective view showing the initial state of the optical coupling method of the eighth embodiment of the present invention and FIGS. 15(b) to 15(d) are sectional views showing the optical coupling method of the eighth embodiment of the present invention;

FIG. 16 is a sectional view showing another configuration of the optical coupling method of the eighth embodiment of the present invention;

FIG. 17 is a refractive-index distribution diagram between optical parts coupled by the eighth embodiment of the present invention;

FIG. 18 is an illustration showing a light propagation pattern between optical parts coupled by the eighth embodiment of the present invention;

FIG. 19 is a refractive-index distribution diagram between optical parts with misalignment of optical axes coupled by the eighth embodiment of the present invention;

FIG. 20(a) is a sectional view showing the state of coupling the optical fiber with the semiconductor laser in the eighth embodiment of the present invention, FIG. 20(b) is a sectional view showing the state of coupling the optical fiber with the semiconductor laser in the eighth embodiment of the present invention, and FIG. 20(c) is a sectional view showing the state of coupling the optical fiber with the photodiode in the eleventh embodiment of the present invention;

FIGS. 21(a) to 21(d) are sectional views showing the steps of the optical coupling method of the ninth embodiment of the present invention;

FIGS. 22(a) to 22(c) are sectional views showing the steps of the optical coupling method of the twelfth embodiment of the present invention and FIG. 22(d) is a sectional view showing another configuration of the optical coupling method of the twelfth embodiment of the present invention;

FIGS. 23(a) to 23(c) are sectional views showing the steps of the optical coupling methods of the thirteenth to seventeenth embodiments of the present invention and FIG. 23(d) is a sectional view showing another configuration of the optical coupling methods of the thirteenth to seventeenth embodiments of the present invention; and

FIG. 24(a) is a perspective view showing the initial state of the optical coupling method of the eighteenth embodiment of the present invention and FIGS. 24(b) to 24(c) are sectional views showing the steps of the optical coupling method of the eighteenth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

FIGS. 2(a), 2(b), 3(a) and 3(b) show the optical coupling steps of the first embodiment of the present invention.

In these figures, symbols 11 and 12 are first and second optical parts, and concretely they show optical fibers.

The optical fibers 11 and 12 comprise cores 11a and 12a in which light is confined, cladding 11b and 12b for concentrically enclosing the cores 11a and 12a, and jackets 11c and 12c for protecting the cladding 11b and 12b.

The refractive index of the cores 11a and 12a is larger than the refractive index of the cladding 11b and 12b. The light incoming from the edge of an optical fiber is confined in the cores 11a and 12a and propagates in the optical fiber.

The cores 11a and 12a and the cladding 11b and 12b use a fusible optical waveguide material. Though the optical waveguide material is not restricted as long as it is fused by heating and transparent for guided light, organic materials and glass are particularly desirable.

For example, organic materials include thermoplastic resins such as polymethyl methacrylate, polystyrene, polyester, polycarbonate, polyolefin, styrene-methylmethacrylate copolymer, styrene-acrylonitrile copolymer, and poly-4-methylpentene-1-polyvinyl chloride. Moreover, it is possible to use thermosetting or photo-curing resins such as epoxy resin, polyamide, crosslinkable polyester, crosslinkable polyacrylate, and silicon in order to improve the heat resistance and mechanical strength after fusion. Furthermore, it is possible to thermopolymerizable or photopolymerizable monomers such as styrene, methacrylate, acrylate, acrylic compound, and isocyanate compound.

It is also possible to use hybrid materials made by mixing the above resins and monomers.

Moreover, it is possible to properly add polymerization initiator to the mixed hybrid materials so as to quickly start polymerization by heat or light. Furthermore, it is possible to use a proper additive to the materials in order to adjust the properties such as the viscosity, fusing temperature, refractive index, and transparency of them. In this case, even if the material is liquid, it is possible to fuse it by increasing the viscosity of the material.

The glass material can use soda glass, pyrex, or quartz. It is also possible to add a proper additive to the material in order to adjust the properties of the material such as the fusing temperature, refractive index, and transparency.

The following is the description of optical coupling of an optical fiber.

An optical fiber 11 is set to a movable retainer 13. In the movable retainer 13, a fiber securing portion 13a is coupled with a movable fiber retaining portion 13b for retaining the optical fiber 11 by a spring 13c and the movable fiber retaining portion 13b is kept movable. The optical fiber 11 is secured to the movable fiber retaining portion 13b and kept movable relative to a fiber securing portion 13a.

The movable fiber retaining portion 13b is constituted so that it is movable from a fixed retainer 14 for retaining an optical fiber 12 in order to position the op