JPH08271746A - Optical waveguide and its production - Google Patents

Abstract

PURPOSE: To provide an optical waveguide which is an inexpensive and easily producible, is a waveguide for high-performance optical elements, etc., is particularly a waveguide for single mode and is easily optically couplable with low loss to another optical parts with positioning accuracy of several μm order or below and a production method thereof. CONSTITUTION: The core 7 of the optical waveguide having at least the core 7 and a clad which encloses the core 7 and has the refractive index lower than the refractive index of the core 7 is formed by photosetting or thermally curing a mixture composed of a monomer or oligomer having an epoxy ring and a polymn. initiator. Otherwise, the core 7 is formed by photosetting or thermally curing a mixture composed of a monomer or oligomer having an unsatd. group and a polymn. initiator. The core 7 is formed by photosetting or thermally curing a mixture composed of a monomer or oligomer having a siloxane bond and a polymn. initiator and the viscosity of this mixture is preferably <=10000cps at room temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide which can be used in optical devices used in the fields of optical communication and optical information processing, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, an optical waveguide such as a waveguide type optical element of this type is manufactured by using quartz glass or a dielectric crystal such as LiNbO ₃ as a material. Since its fabrication requires microfabrication, photolithography, dry etching process, etc., which are often used in LSI processes, were combined. About this, Masao Kawauchi's Optical and Quantum E
electronics 22 vol. 391 (1990)
Year) will be helpful.

However, in the conventional manufacturing method, the manufacturing process is complicated and the manufacturing apparatus used is expensive.
It is not suitable for mass production and has a drawback that an optical waveguide such as an inexpensive element cannot be manufactured.

Further, even if an optical waveguide such as an element is manufactured by a conventional manufacturing method, precise adjustment is required when optical coupling with another optical component such as an optical fiber is required thereafter, which is suitable for mass production. There is a problem not.

Furthermore, recently, optical waveguides have also been manufactured using cheaper materials and polymer materials. Regarding this, Electronics by Mr. Imamura et al.
Letters 27 Vol. 1342 (1991)
Year) will be helpful. However, if a waveguide manufacturing method similar to the glass waveguide is used as a manufacturing method, it is necessary to repeat the same patterning process for each substrate,
Since the etching apparatus is expensive, the overall process cost is the same as that of the glass waveguide even if the material is inexpensive, and as a result, it is not cheap. Also in this case, even if the waveguide is manufactured,
After that, when performing optical coupling with another optical component such as an optical fiber, precise adjustment is required, and thus there is a problem that it is not suitable for mass production.

Therefore, in order to reduce the process cost or avoid the complexity of optical coupling, a method of producing a polymer waveguide by a polymer molding method such as injection molding by transferring a mold has been proposed. Although this is a manufacturing method suitable for mass production, it has a drawback that a waveguide having sufficient optical characteristics cannot be realized in manufacturing a single mode waveguide that requires processing accuracy of the order of several μm.

Further, Si is produced by such a polymer molding method.
Using a mold produced based on the V-groove processing applied to the substrate, the V-groove is integrally produced with the polymer waveguide, and the coupling with the optical fiber arranged in the V-groove is simplified. The idea of reducing the cost associated with the production of waveguides such as optical elements has also been proposed. However, particularly in the coupling between the single-mode waveguide and the single-mode optical fiber, alignment accuracy on the order of several μm or less is particularly required, so that there is a drawback that a waveguide having a sufficiently low coupling loss cannot be manufactured. All of these are mainly due to a large difference between the mold size used during molding and the transfer size of the polymer portion after molding.

[0008]

SUMMARY OF THE INVENTION The first object of the present invention is to provide a waveguide for an optical element or the like, which is inexpensive, can be easily manufactured, and has high performance, and in particular a single mode waveguide. An object of the present invention is to provide an optical waveguide which can be easily and low-loss optically coupled with other optical components with alignment accuracy of the order of μm or less.

A second object of the present invention is to provide an efficient method for producing such an optical waveguide.

[0010]

The factors for solving the above problems in the present invention will be briefly described.

(1) In the waveguide manufacturing process for manufacturing an optical waveguide such as an optical element, a large-scale apparatus is not used, and a processing method suitable for mass production is used. (2) Material cost is low and processing is difficult. Easy to use polymeric material,
(3) When manufacturing an optical waveguide, it is possible to use a mold in consideration of alignment with other optical components such as an optical fiber, and to simplify the work for optical coupling after manufacturing as much as possible.

In the present invention, an optical waveguide is basically manufactured by molding a cheap polymer material by a molding method for transferring a pattern of a mold, which is a processing method suitable for mass production.
The problem in this case is that, as described above, the size of the mold used at the time of molding and the transfer size of the polymer portion after molding are greatly different. This is because, for example, after injection molding, a polymer is molded by applying a very large pressure at a high temperature and then cooled to room temperature. When a polymer material having a coefficient of thermal expansion is used, it is often difficult to reduce the difference between the die size used during molding and the transfer dimension of the polymer portion after molding.

Therefore, in order to achieve the first object, the invention according to claim 1 is an optical waveguide having at least a core and a clad surrounding the core and having a refractive index lower than that of the core. Is characterized by being photocured or heat-cured from a mixture of a monomer or oligomer having an epoxy ring and a polymerization initiator.

According to a second aspect of the present invention, in an optical waveguide having at least a core and a clad surrounding the core and having a refractive index lower than that of the core, the core initiates polymerization with a monomer or oligomer having an unsaturated group. It is characterized in that a mixture of agents is photocured or heat cured.

According to a third aspect of the present invention, in an optical waveguide having at least a core and a clad surrounding the core and having a refractive index lower than that of the core, the core has a monomer or oligomer having a siloxane bond and a polymerization initiator. It is characterized in that it is a mixture obtained by photo-curing or heat-curing the mixture.

The invention according to claim 4 is the invention according to claims 1 to 3.
In the optical waveguide described in any one of 1. above, the viscosity of the mixture may be 10,000 cps or less at room temperature.

In order to achieve the second object, the invention according to claim 5 uses an optical mold mainly having a photo-curable raw material for a core, which uses a molding die having a desired core shape. In a method for producing an optical waveguide including a step of curing a material by light irradiation or heating to form a core, the molding die has a light-transmitting property, and the light irradiation is performed through the molding die. Is characterized by.

In the production method of the present invention, a polymer material of a type that is cured by light or heat is used, and a material that is cured even when heat is applied and does not require a high temperature is used at the time of molding. The difference between the mold size and the transfer size of the polymer portion after molding can be minimized.

Further, in the method for producing an optical waveguide of the present invention, the structure of a material that is cured by light or heat also has an epoxy ring, an unsaturated group, silicone, etc., so that curing shrinkage is small. Therefore, it is possible to reduce the difference between the size of the mold used at the time of molding and the transfer size of the polymer portion after molding.

Further, in the method of manufacturing the optical waveguide of the present invention,
The optical waveguide and the V-groove for mounting the optical fiber can be integrally formed by making the structure of the molding die used to be specific. Thereby, the optical coupling between the optical waveguide and the optical fiber can be accurately and easily performed.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, one embodiment of the method for producing an optical waveguide of the present invention will be described with reference to FIGS.

As shown in FIG. 1A, a coating layer 2 is provided on a substrate 1 processed into a desired shape by means such as spin coating or dipping. Examples of the material for forming the coating layer 2 include a monomer or an oligomer which has fluidity at room temperature, is cured by irradiation with light, and has a relatively small curing shrinkage, which will be described later.

Next, as shown in (b), the coating layer 2 is covered with a molding die 3 having a long convex portion 3a having a desired shape. In this embodiment, the mold 3 is made of a material that transmits at least light (ultraviolet light) having a wavelength used to cure the coating layer 2. The coating layer 2 is cured by irradiating the light 4 having the above-mentioned transmission wavelength from above the mold 3 to form a cured film 5a to be a lower clad. Of course, at the time of light irradiation, the coating layer 2 may be heated and cured at a predetermined temperature.

Next, as shown in (c), when the mold 3 is removed, a groove having a shape and size corresponding to the long convex portion 3a of the mold 3 is exposed on the upper portion of the cured film 5a, and the groove is exposed in the groove. The core material is contained and the core material layer 6 is formed. Examples of the core material 6 include a monomer or an oligomer that has a higher refractive index than the cured film 5a that is the lower clad at the time of curing and exhibits fluidity at room temperature.

In this step (c), a material to be cured by light irradiation or heating is inserted into the groove. However, if the material has a viscosity of 10,000 cps or more, it is difficult to insert it only into the groove, and the material is cured. After that, a step such as dry etching is required to remove the surplus portion,
The viscosity of the material inserted into the groove is preferably 10,000 cps or less.

Next, as shown in (d), light irradiation 4 is performed again.
Thus, the core material layer 6 is cured to form a cured film 7. Of course, at the time of light irradiation, the core material layer 6 may be heated and cured at a predetermined temperature. At this time, if there is a surplus portion of the core material layer 6 protruding from the groove, it is removed by dry etching or the like.

Next, as shown in (e), a material similar to that of the coating layer 2 is applied onto the cured films 5 and 7, and then a cured film 5b serving as an upper clad is formed by light irradiation to form a core. It is possible to obtain the target waveguide type optical element 8 including the upper and lower clads.

Next, a modification of the above embodiment will be described with reference to FIG.

First, FIG. 2 (a) shows the same state as FIG. 1 (a). In this modified example, the coating layer 2 is cured by light irradiation or heating as shown in FIG. 2B, without using the mold 3 having the long convex portions 3a in FIG. The cured film 5a becomes On the other hand, the core material is housed in the elongated recess 9a formed in the upper portion of the mold 9 to form the core material layer 6. As the core material, as described above, a monomer or an oligomer having a refractive index higher than that of the cured film 5a at the time of curing and exhibiting fluidity at room temperature can be mentioned. As described above, this core material also has a viscosity of 100 in consideration of the difficulty of insertion into the groove.
00cps or less is desirable.

Next, as shown in (c), the substrate 1 is placed on the mold 9 with the cured film 5a facing downward, and if the mold 9 is transparent, light is irradiated from below the mold 9, Alternatively, the core material layer 6 is cured by heating to form the core ridge 10. Type 9
Then, as shown in (d), the core ridge 10 is exposed so as to project onto the cured film 5a. Next, a material similar to the material for forming the coating layer 2 is applied on the core ridge 10 and the hardened film 5a, and is hardened by light irradiation or heating to form a hardened film 5b serving as an upper clad. Through these steps, as shown in (e), it is possible to obtain the desired waveguide type optical element 8 including the core and the upper and lower clads.

The present invention will be described in detail below with reference to specific examples.

Example 1 A method of manufacturing the optical waveguide of the present invention will be described. FIG. 3 shows the manufacturing procedure.

First, as shown in (a), a substrate 21 is prepared, and an epoxy UV monomer (viscosity 1000 cps) as a lower clad material is spin-coated on the substrate 21.
Is applied to form a coating layer 22. The main component of this coating material is the following general formula

[0035]

Embedded image

(Where n is an integer greater than or equal to 0) or the following general formula

[0037]

Embedded image

It is represented by On this coating layer 22,
As shown in (b), the glass mold 24 is covered. The mold 24 has a width of 10 μm, a height of 10 μm, and a length of 5 below.
It has a convex portion 24a of 0 mm. The coating layer 22 is covered with the mold 24, and the coating layer 22 is photocured by ultraviolet irradiation 25 to form the lower clad 23a of the waveguide as shown in FIG. 7C (refractive index n = 1.51, Wavelength 1.31 μm). A recess is formed on the lower clad 23a according to the shape of the protrusion 24a of the mold 24.

Next, as shown in (d), the epoxy-based UV monomer, which has the same main component as the material forming the coating layer 22 and serves as a core material, is provided in the recess of the lower clad 23a. A material (viscosity 100 cps) is inserted to form the core material layer 26. At this time, if the core material having a monomer viscosity of 100 cps or less is selected, the core material can be inserted into only the groove (recess), and the step of removing the protruding material can be omitted.

Next, as shown in (e), the core material layer 26 made of a monomer is photo-cured by irradiation of ultraviolet rays to form the core 2
Form 7. The core 27 has a width of 7 μm and a height of 7 μm.
(Refractive index n = 1.52, wavelength 1.3)
1 μm).

Next, as shown in (f), an epoxy-based UV monomer, which is the same material as the material for forming the coating layer 22, is applied onto the core 27 and the lower clad 23a and cured by irradiation with ultraviolet rays. To form the upper clad 23b. As a result, the optical waveguide 28 including the core and the upper and lower clads can be manufactured.

When the waveguide loss of the obtained optical waveguide 28 was measured using an LD light source (wavelength 1.31 μm), the waveguide loss was 0.3 dB / cm.

Example 2 A waveguide type optical element was manufactured by the same manufacturing method as in Example 1 except that the following monomers having unsaturated groups were used as the main components of the core material and the upper and lower clad materials. However, the waveguide loss is 0.1 dB.
/ Cm (clad refractive index n = 1.47, core refractive index n = 1.48, core width 7 μm, height 7 μm).

[0044]

Embedded image

[0045]

[Chemical 4]

Example 3 A waveguide type optical element was manufactured by the same manufacturing method as in Example 1 except that the following monomers having a siloxane bond were used as the main components of the core material and the upper and lower cladding materials. , The waveguide loss is 0.
1 dB / cm (wavelength 1.3 μm), 0.5 dB / cm
(Wavelength 1.55 μm) (clad refractive index n =
1.50, core refractive index n = 1.51, core width 7 μm, height 7 μm). The monomer having a siloxane bond is represented by the following general formula, where n is a natural number.

[0047]

Embedded image

[0048]

[Chemical 6]

(Embodiment 4) A method for producing a V-grooved waveguide according to the method of the present invention will be described. FIG. 4 shows the manufacturing procedure.

First, as shown in (a), a substrate 30 is prepared, and an epoxy UV monomer is coated on the substrate 30 to form a coating layer 31.

On the other hand, as shown in (b), a glass mold 32 is prepared. The mold 32 has a V-shaped convex portion 33 on a part of the lower side thereof. This convex portion 33 has an opening angle of 60 °, a height of 150 μm, a width of 170 μm, and a length of 20.
It has a dimension of mm.

Next, as shown in (c), the mold 32 is covered on the coating layer 31, and ultraviolet irradiation 34 is performed from above the mold 32 by a UV light source to expose and photo-cure the lower clad (refractive index). (n = 1.51, wavelength 1.31 μm) 35a. The coating layer 31 is cured according to the convex shape on the lower side of the mold 32, and the V groove 36 is formed on the upper surface of the lower clad 35a. The V groove 36 has an opening angle of 60 °, a height of 150 μm,
It has a length of 20 mm.

On the other hand, as shown in (d), another mold 37 is prepared. A convex portion 38 having the same size as the convex portion 33 of the mold 32 is formed on the lower side of the mold 37, and a narrow groove portion extending from the end portion on the center side of the convex portion 38 along the length direction of the convex portion 38. 39
Are formed. The narrow groove portion 39 has a depth of 10 μm,
It has a width of 10 μm and a length of 40 mm.

Next, as shown in (e), the epoxy-based UV monomer 300 serving as a core is inserted into the narrow groove portion 39 of the mold 37, and the lower clad 35a of the substrate 30 is adhered as shown in (c). Let Next, as shown in (f), light is irradiated from below the mold 37 to cure the monomer 300, and the core ridge 301 is formed in a state of being in close contact with the lower clad 35a. At this time, the V groove 36 formed on the lower clad 35a and the V-shaped convex portion 38 of the mold 37 are formed.
By accurately matching and, the core ridge with a width of 10 μm and a height of 10 μm (refractive index n = 1.
52, wavelength 1.31 μm) 301 is aligned with the position of the V groove 36.

Next, as shown in (g), the epoxy UV monomer 31 is applied again and cured by light irradiation to form the upper clad 35b. Thus, the V-groove waveguide 302 including the core ridge 301 and the upper and lower clads 35a and 35b can be manufactured. This waveguide 3
Although the optical fiber can be fixed to the V groove 36 of No. 02, since the V groove 36 is formed integrally with the core ridge 301, the positioning of the optical fiber and the core ridge 301 can be easily performed at the time of optical coupling. And it can be performed with low connection loss. Although the V-shaped groove is used as the groove shape for inserting the optical fiber in this embodiment, it is needless to say that the groove may not be the V-shaped groove as long as the optical fiber can be inserted.

The appearance of the obtained waveguide 302 is shown in FIG. Fix the optical fiber in this V groove 36, and
When the waveguide loss was measured using a D light source (wavelength 1.31 μm), the connection loss with the fiber was 0.2 dB and the waveguide loss was 0.3 dB / cm.

In each of the above examples, an example of producing an optical waveguide using a photo-curing agent was shown, but when polymerization is performed by heat, similar production can be performed by changing the type of polymerization initiator.

[0058]

As described above, according to the present invention,
A low-cost, easy-to-fabricate yet high-performance optical element waveguide, especially a single-mode waveguide of several μm
It is possible to provide an optical waveguide that can be optically coupled to other optical components easily and with low loss with a positioning accuracy of the order or less.

Further, according to the present invention, since the optical waveguide and the groove for fixing the optical fiber are integrally provided, the optical coupling between the optical fiber fixed in the groove and the optical waveguide is accurate and simple. Can be done with low loss.

[Brief description of drawings]

1A to 1E are cross-sectional views showing respective steps in an example of a method for producing an optical waveguide of the present invention.

FIGS. 2A to 2E are cross-sectional views showing respective steps in another embodiment of the method for producing an optical waveguide of the present invention.

3A to 3F are diagrams showing respective steps in still another embodiment of the method for producing an optical waveguide of the present invention, FIG. 3A being a sectional view, and FIG. (F) is a perspective view.

4 (a) to (h) are diagrams showing respective steps in another embodiment of the method for producing an optical waveguide of the present invention, wherein (a), (c), (e) to (e). g) is a sectional view,
(B), (d) and (h) are perspective views.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Monomer or oligomer showing fluidity at room temperature 3 Mold for molding 4 Light irradiation or heating 5a Lower clad 5b Upper clad 6 Core material layer 7 Core 8 Waveguide type optical element 9 Mold for molding 9a Recess 10 Core ridge 21 Substrate 22 Epoxy UV Monomer 23a Lower Clad 23b Upper Clad 24 Mold for Mold 25 Light Irradiation 26 Core Material Layer 27 Core 28 Linear Waveguide 30 Substrate 31 Epoxy UV Monomer 32 Mold for Mold 33 V-Shaped Convex 34 Ultraviolet irradiation 35a Lower clad 35b Upper clad 36 V groove 37 Mold for molding 38 V-shaped convex portion 39 Fine groove portion 300 Core material 301 Core ridge 302 V Waveguide with V groove

Claims (5)

[Claims] 1. An optical waveguide having at least a core and a clad surrounding the core and having a refractive index lower than that of the core, wherein the core photocures a mixture of a monomer or oligomer having an epoxy ring and a polymerization initiator. An optical waveguide characterized by being thermoset. 2. An optical waveguide having at least a core and a clad surrounding the core and having a refractive index lower than that of the core, wherein the core photocures a mixture of an unsaturated group-containing monomer or oligomer and a polymerization initiator. Alternatively, an optical waveguide characterized by being heat-cured. 3. An optical waveguide having at least a core and a clad surrounding the core and having a refractive index lower than that of the core, wherein the core photocures a mixture of a monomer or oligomer having a siloxane bond and a polymerization initiator. An optical waveguide characterized by being thermoset. 4. The viscosity of the mixture is 10 at room temperature.
The optical waveguide according to any one of claims 1 to 3, wherein the optical waveguide has a velocity of 000 cps or less. 5. An optical device comprising a step of forming a core by using a molding die having a desired core shape and curing an optical material mainly composed of a photocurable core raw material by light irradiation or heating. In the method for producing a waveguide, the method for producing an optical waveguide is characterized in that the molding die has optical transparency, and the light irradiation is performed through the molding die.