JPH09189816A - Plane type optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the amt. of optical polymers for clads to be used and to prevent the disturbance in signal light by leaking light by providing the surface of a substrate with a non-optical polymer and embedding the clads consisting of the optical polymer into this layer. SOLUTION: A non-fluorinated polyamide film 12 of Kapton type is first formed as the non-optical polymer on the substrate 11 consisting of a Si wafer and is formed with grooves 13 arriving at the substrate 11. Fully fluorinated polyimide is then packed as the clads 14 into these grooves 13 to form grooves 15 for cores. The fully fluorinated polyimide is packed onto grooves 15 to form cores 16. As a result, the regions of the clads 14 is restricted within the necessary range and the amt. of the costly polymers for the clad to be used is decreased. The light leaking from the cores 16 is absorbed by the non-optical polymer and the propagation of this light to unnecessary places is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate type optical waveguide in which a clad and a core made of an optical polymer material are formed on a substrate, and more particularly to a flat plate type optical waveguide in which the disturbance of signal light is reduced.

[0002]

2. Description of the Related Art The basic structure of a flat plate type optical waveguide made of a polymer material is, for example, as shown in FIG. 9, a clad layer 1 is provided on a flat substrate 3, and the clad layer 1 is used for optical waveguide. The core 2 is embedded. Clad layer 1
Is made of a material having a substantially good light transmission property for guided light. As the polymer-based material here, any of a thermosetting type, a plastic type, and an ultraviolet curing type can be used.

In order to produce such an optical waveguide, an expensive polymer for optics is used for the core and the clad, and it is desired to use the polymer in the smallest possible amount. by the way,
As the polymer for the clad, one having a good transmittance is generally used. The reason is that, as described above, the light that is spotted in the clad is also considered to be a part of the guided light, so absorption of the guided light by the clad material results in attenuation of the guided light, which is not desirable. Is. However, a polymer having a good transmittance is generally expensive. In order to avoid light scattering due to contaminants, it is necessary to strictly filter and purify the product, which increases the unit price of the optical polymer.
Further, in terms of materials, examples of polymers having good transparency to light in the near infrared region, which is the current wavelength for communication, include fluorinated or deuterated Si-based polymers, all of which are general-purpose polymers. The unit price is considerably higher than.

However, there is a limit in reducing the amount of the optical polymer used for the following reason. That is, 1) Generally, the thickness of the clad layer is required to be about 20 μm, although it depends on the difference in refractive index between the clad and the core. The reason is as follows. Some of the light guided in the core also exists in the cladding. Therefore, when the clad layer is thin, the light spotted in the clad is absorbed or scattered by the substance outside the clad, and as a result, the guided light is attenuated. 2) When manufacturing a waveguide on a flat substrate, 2
A clad layer having a thickness of about 0 μm is sufficient, but when a waveguide having electronic elements such as a semiconductor laser element (LD) and a photodiode (PD) is manufactured, it is necessary to further increase the clad layer. For example, as shown in FIG. 10, in the case of the LD-mounted waveguide, the cladding layer 1 having a thickness of the LD 4 of about 100 μm is required. Also,
As shown in FIG. 11, the Si substrate 3 is formed into a terrace shape and L
Although it is considered to effectively lower the emission port of D4, the clad material must fill the step of the terrace 3a, and the clad layer 1 thickness of 20 μm or more is required. .

On the other hand, although not limited to polymer materials, leak light is a problem in optical waveguides. For example, in the case of the Mach-Zehnder type optical waveguide shown in FIG. 12, a part 6 of the signal light leaked into the cladding layer 1 from the Y branch at the point A on the incident side 5 along the core 2 without being bent.
Passes through the clad layer 1 and is coupled to the Y branch at the point B to disturb the signal. This occurs because the clad layer 1 portion is also a material having good light transmittance. As a method for avoiding this leaked light, a method of allowing the combined waveguide to have a predetermined curvature to allow the leaked light to escape (see Japanese Patent Laid-Open No. 6-67047), or refraction of the core at the bent portion of the waveguide There is a method of suppressing the leaked light by increasing the rate (see Japanese Patent Application Laid-Open No. 6-67042), but none of them decisively suppresses the leaked light. In addition, there is a method in which a groove is formed in the clad portion of the produced waveguide and a light absorber is provided therein to absorb unnecessary mode light generated in the waveguide (Japanese Patent Publication No. 6-85006). reference). This method is also effective as a method for preventing leakage light. However, this method is not suitable for the purpose of reducing the amount of the above-mentioned expensive optical polymer for cladding.

[0006]

As described above, in the flat type optical waveguide made of the conventional polymer material, the amount of expensive optical polymer for the clad used is reduced and the signal light is disturbed by the leaked light. There was a problem that it was difficult to avoid.

[0007]

The present invention has been made to solve the above problems, and a non-optical polymer layer having at least one groove is provided on a substrate, and the groove is
At least a part of a clad made of an optical polymer is embedded, and a core having a larger optical refractive index than the clad is provided in the clad. Here, the optical polymer is a highly filtered one and is also called an optical grade. Further, the non-optical polymer means a polymer which is not highly filtered, and such a configuration can reduce the amount of expensive optical polymer used.

In order to reduce the disturbance of the signal light due to the leaked light, it is preferable to use a material having the following properties as the material of the non-optical polymer. That is, 1) Use a substance that absorbs the guided light used. The value of the light transmission loss of the material is (Y + 0.2) dB at least when the light transmission loss of the cladding material is Y dB / cm.
Those having a light transmission loss of / cm or more are preferable, and the larger the light transmission loss, the better. 2) The refractive index n is preferably n ₁ ≦ n, where n ₁ is the refractive index of the cladding material. The reason is that if the refractive index of this non-optical polymer is smaller than that of the clad material, the non-optical polymer functions as a clad layer and the original clad layer functions as a core layer, preventing the original leaked light. This is because it does not fulfill the function of absorbing. The refractive index of the non-optical polymer is preferably not too high. If the refractive index is much larger than the refractive index of the clad, some of the leaked light will be reflected at the interface between the clad and this non-optical polymer, and this will also cause disturbance of the signal light. is there. Therefore, in order to reduce this reflection, the refractive index of the non-optical polymer is preferably slightly larger than the refractive index of the clad, and more preferably the same as that of the clad. Also,
Most of the spotted light is said to pass through the clad within the range of 20 μm from the core. Therefore, as a structural feature, the non-optical polymer should not be in direct contact with the core, and is more preferably provided at a distance of 20 μm or more from the core.

[0009]

As described above, by providing the non-optical polymer layer having at least one groove on the substrate and embedding at least a part of the clad made of the optical polymer in the groove, the clad region can be formed in a required area. It is possible to reduce the amount of the expensive polymer used for the clad.
Further, with such a structure, the light leaked from the core can be absorbed by the non-optical polymer and prevented from propagating to the unnecessary place.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. Example 1 FIGS. 1A to 1D are explanatory views of a manufacturing process of an example of a flat plate type optical waveguide according to the present invention. This process is as follows. That is, 1) First, a Kapton-based non-fluorinated polyimide film 12 as a non-optical polymer is formed on a substrate 11 made of a Si wafer, and a groove 13 reaching the substrate 11 is formed in the polyimide film 12 by dry etching. (Fig. 1
(A)). 2) Next, the groove 13 is filled with a perfluorinated polyimide having the structural formula shown in FIG.
The groove 15 for the core was formed by dry etching (FIG. 1B). 3) Next, the groove 15 formed in the clad 14 is filled with a perfluorinated polyimide represented by the structural formula shown in FIG.
Coating from the side to complete the Y-branch waveguide (Fig. 1
(C)). In addition, this Y-branch waveguide has the same shape.
This was produced. 4) Next, apply a general-purpose thermosetting epoxy adhesive 17 on one Y-branch waveguide, turn the other Y-branch waveguide upside down, and stack them so that the two Y-branches are vertically stacked and heated. Then, the adhesive 17 was cured to produce a laminated Y-branch flat plate type waveguide (FIG. 1D).

In this waveguide, a non-optical polymer is used.
The refractive index of a certain polyimide film 12 is n _Four, Non-optical polymers
The refractive index of the epoxy adhesive 17_Three, Clutch
The refractive index of do 14 is n_Two, The refractive index of the core 16 is n₁To be
And these relationships_Four> n _Three> n₁> n_TwoAnd Ma
Also, the core 16 and the polyimide film 1 which is a non-optical polymer
2 and the closest distance to the epoxy adhesive 17 is 20μ
m, the thickness of the adhesive 17 layers is 20 μm, and the cores are stacked one above the other.
The side surface spacing of 16 and 16 was 60 μm. Lower Y branch
Light of 1.65 μm is incident from the first port 18, and the upper and lower layers
Measure the intensity of the light coming out of each second port 19 and 20 of the layer
Specified. Based on the intensity of the light emitted from the lower port 20
Table 1 shows the output light intensity from the upper port 19 when
Indicated.

Embodiment 2 FIGS. 4 (a) to 4 (d) are views for explaining manufacturing steps of another embodiment of the flat plate type optical waveguide according to the present invention. This process is as follows. That is, 1) First, a Kapton-based non-fluorinated polyimide film 12 as a non-optical polymer was formed on a substrate 11 made of a Si wafer, and a groove 13 was formed in the polyimide film 12 by dry etching (FIG. 4). (A)). 2) Next, as shown in FIG.
Copolymer type fluorinated polyimide having the structural formula shown in (a) and (b) was filled, and the groove 15 for the core was formed by dry etching (FIG. 4B). 3) Next, the groove 15 formed in the clad 14 was filled with the fluorinated polyimide represented by the structural formula shown in FIG. 5B to form the core 16 (FIG. 4C). 4) Next, polyimide for clad was filled from above the core 16 again, and the heater 21 was attached to the coupling portion to fabricate a directional coupler waveguide TO switch utilizing the thermo-optic effect (Fig. 4 (d)).

In this waveguide, the closest distance between the core 16 and the polyimide film 12 which is a non-optical polymer is 25.
μm. If the refractive index of the non-optical polymer polyimide film 12 is n ₃ , the refractive index of the clad 14 is n ₂ , and the refractive index of the core 16 is n ₁ , then these relationships are n ₃ > n ₁ > n ₂ And Then, 1.3 μm light is incident from the first port 22, and the current value applied to the two heaters 21 is adjusted, whereby the second and third ports 23,
The place where the extinction ratio of the light emitted from 24 is the largest is searched, and when the second port 23 is bright, the switch is defined as ON, and when the third port 24 is bright, it is defined as OFF. Table 1 shows the intensity of the emitted light from the third port 24 at that time, based on the intensity of the emitted light from the second port 23 in the switch ON state.

Example 3 FIGS. 6 (a) and 6 (b) are explanatory views of a manufacturing process of another example of the flat plate type optical waveguide according to the present invention. This process is as follows. That is, 1) It becomes a non-optical polymer by the injection polymerization method.
CR-39 mixed with 05 wt% carbon black
The molded body 31 of was produced (FIG. 6A). 2) The refractive index is n _{2 in} the groove 32 of the non-optical polymer.
Clad 3 made of UV-curable fluorinated epoxy resin
3 and a core 34 made of an ultraviolet curable fluorinated epoxy resin having a refractive index of n ₁ are formed, and as shown in FIG.
A branching waveguide having continuous branches was manufactured. In this waveguide, the molded body 31 and the core 3 which are non-optical polymers
The closest distance to 4 was 30 μm, and the thickness from the surface of the clad 33 to the core 34 buried in the groove 32 was 20 μm. Further, assuming that the refractive index of the non-optical polymer is n ₃ , the relationship of the refractive index of each material was n ₁ > n ₃ > n ₂ . Light of 633 nm was incident from the first port 35, and the intensity of light emitted from the second and third ports 36 and 37 was measured. Table 1 shows the intensity of the emitted light from the second port 36 at that time, based on the intensity of the emitted light from the third port 37. The intensity of the emitted light is 0.1 dB or less, which is extremely small. This means that the intensity of the emitted light from the second and third ports 36 and 37 is almost equal and is not affected by the adjacent fourth port 38. Shows.

Embodiment 4 FIGS. 7 (a) and 7 (b) are manufacturing process explanatory views of another embodiment of the flat plate type optical waveguide according to the present invention. This process is as follows. That is, 1) A polystyrene molded body 41 mixed with 0.05 wt% of carbon black as a non-optical polymer was produced by the injection method (FIG. 7).
(A)). 2) In the groove 42 of the molded body 41, a clad 43 made of an ultraviolet curing fluorinated epoxy resin having a refractive index of n ₂ ,
A core 44 made of an ultraviolet curable fluorinated epoxy resin having a refractive index of n ₁ is formed, and a heater 45 is further attached to the coupling portion as shown in FIG. A switch was made. In this waveguide, the closest distance between the core 44 and the molded body 41 is 30 μm.
Met. Further, the refractive index of the non-optical polymer When n _3, the relationship of the refractive index of each material were _{n 3> n 1> n 2} . Then, 633 μm light is made incident from the first port 46, and the current value applied to the two heaters 45 is adjusted to find the place where the extinction ratio of the light emitted from the second and third ports 47, 48 is the largest. If the second port 47 is bright, turn on this switch, and the third port 4
When 8 was bright, it was defined as OFF. Based on the intensity of the light emitted from the second port 47 when the switch is on,
Table 1 shows the intensity of light emitted from the third port 48 at that time.

Embodiment 5 FIGS. 8 (a) to 8 (c) are views for explaining manufacturing steps of another embodiment of the flat plate type optical waveguide according to the present invention. This process is as follows. That is, 1) A groove 52 is formed in a substrate 51 made of a Si wafer (FIG. 8A). 2) Next, this groove 52 is filled with Kapton-based non-fluorinated polyimide as a non-optical polymer, and the groove 52a is covered with the polyimide 53 by dry etching.
Was formed (FIG. 8B). 3) Thereafter, a directional coupler waveguide type TO switch was manufactured in the same manner as in Example 2 (FIG. 8C). In the figure, 54 is a clad, 55 is a core, and 56 is a heater. Polyimide 53, which is a non-optical polymer in this waveguide
Was 20 μm everywhere, and the closest distance between the core 54 and the polyimide 53 was 20 μm. In addition, the refractive index of the non-optical polymer polyimide 53 is n ₃ , the cladding 5
When the refractive index of 4 is n ₂ and the refractive index of the core 55 is n ₁ ,
These relationships were n ₃ > n ₁ > n ₂ . Then, 1.3 μm light is incident from the first port 57, and the current value applied to the two heaters 56 is adjusted, so that the extinction ratio of the light emitted from the second and third ports 58 and 59 is the largest. And the case where the second port 58 is bright is defined as ON of this switch, and the case where the third port 59 is bright is defined as OFF. The intensity of the emitted light from the third port 59 at that time was measured with reference to the intensity of the emitted light from the second port 58 when the switch was in the ON state. As a result, as shown in Table 1, a value equivalent to that in Example 2 was obtained. It was

Comparative Example 1 This comparative example corresponds to Example 1. Using a Si wafer as a substrate, a perfluorinated polyimide film having the structural formula shown in FIG. 2 was produced as a clad, and a groove for a core was produced by dry etching this. Figure 3 in this groove
A perfluorinated polyimide represented by the structural formula (1) was filled to form a core, and the clad was further coated from above to complete a Y-branch waveguide. A perfluorinated polyimide for clad having a thickness of 20 μm was formed thereon, and a Y-branch waveguide of the perfluorinated polyimide was further formed thereon by the same method.
A laminated Y-branch flat plate type waveguide was completed. The distance between the upper surface of the lower core and the lower surface of the upper core was 60 μm.
Then, as in Example 1, 1.65 μm light was made incident from the first port of the lower layer Y branch, and the intensity of the light emitted from each of the upper layer and lower layer second ports was measured. Table 1 shows the intensity of light emitted from the second port of the upper layer, based on the intensity of the light emitted from the second port of the lower layer.

Comparative Example 2 This comparative example corresponds to Example 2. Without using Kapton-based non-fluorinated polyimide as a non-optical polymer, the perfluorinated polyimide film used for the cladding in Example 2 was suddenly formed on a Si wafer, and the same procedure as in Example 2 was performed below. A directional coupler waveguide type TO switch was manufactured. Then, similarly to the second embodiment, 1.3 μm light is incident from the first port and the current value applied to the two heaters is adjusted to obtain the most extinction ratio of the light emitted from the second and third ports. Look for the big part, the second of them
The switch is defined as ON when the port is bright and OFF when the third port is bright. Switch on in the table
Based on the intensity of the light emitted from the 3rd port in the state,
The intensity of the light emitted from the third port at that time is shown.

Comparative Example 3 This comparative example corresponds to Example 3. A non-optical polymer was not used, an ultraviolet curable resin film for cladding was formed on a Si wafer, and a branching waveguide was prepared in the same manner as in Example 3 below. Then, as in Example 3, light of 633 nm was made incident from the first port, and the intensity of light emitted from the second and third ports was measured. Table 1 shows the intensity of the emitted light from the second port at that time with reference to the intensity of the emitted light from the third port.

Comparative Example 4 This comparative example corresponds to Example 4. 0.05wt which becomes non-optical polymer by using injection method instead of carbon black polystyrene.
% PM black was mixed to prepare a PMMA molded body, and a directional coupler waveguide TO switch was manufactured in the same manner as in Example 4 below. Further, assuming that the refractive index of each material is the light absorber n ₃ , the cladding n ₂ , and the core n ₁ , the relations of these are n ₁ > n ₂ > n ₃ . Then, as in the case of Example 4, by adjusting the current value applied to the two heaters with 633 μm light incident from the first port, the extinction ratio of the light emitted from the second and third ports is the largest. Look for, and turn on this switch when the second port is bright, and turn it on when the third port is bright.
It was defined as FF. Table 1 shows the intensity of light emitted from the third port when the intensity of light emitted from the second port when the switch was in the ON state was used as a reference.

Comparative Example 5 This comparative example corresponds to Example 2. Unlike Comparative Example 2, a Kapton-based non-fluorinated polyimide was used as a light absorber immediately on a Si wafer,
In addition, a film was made of a material that becomes the clad. This material is obtained by adding 0.5 wt% of the dye rhodamine B to the copolymer type fluorinated polyimide having the structural formula shown in FIGS. 5 (a) and 5 (b). However, the refractive index of this material is the same as that of the cladding material of Example 2. Hereinafter, a directional coupler waveguide type TO switch was manufactured in the same manner as in Example 2. However, in this case, since the clad material also serves as the light absorber, the core and the light absorber are in direct contact with each other. Then, in the same manner as in Example 2, the light of 1.3 μm is incident from the first port 1 and the current value applied to the two heaters is adjusted to adjust the extinction ratio of the light emitted from the second and third ports. The largest part was searched for, and when the second port was bright, it was defined as ON, and when the third port was bright, it was defined as OFF. When the output light intensity from the third port at that time was measured with reference to the output light intensity from the second port when the switch was in the ON state, the amount of light passing through the core was small, and the extinction ratio was determined. There wasn't.

Comparative Example 6 This comparative example corresponds to Example 4. Instead of polystyrene containing carbon black, a molded body was produced by casting with Ni, and a directional coupler waveguide type TO switch was produced in the same manner as in Example 4 below. Assuming that the refractive index of each material is n _{3 for} Ni, n _{2 for} the cladding, and n ₁ for the core, these relationships were n ₃ >> n ₁ > n ₂ . Then, as in the case of Example 4, by adjusting the current value applied to the two heaters by injecting 633 μm light from the first port, the extinction ratio of the light emitted from the second and third ports is the largest. And the case where the second port is bright is defined as ON of this switch, and the case where the third port is bright is defined as OFF. Table 1 shows the intensity of light emitted from the third port when the intensity of light emitted from the second port when the switch was in the ON state was used as a reference.

[0023] Note) ・ Unit: dB ・ *: The extinction ratio could not be obtained because the amount of light transmitted through the core was too small.

The following can be seen from Table 1. That is, 1) From the measurement results of Example 1 and Comparative Example 1, the example in which the non-optical polymer is used between the laminated waveguides has a smaller light leakage and a larger extinction ratio. 2) From the measurement results of Example 2 and Comparative Example 2, the example in which the polymer for non-optics is used between the waveguides in the same plane has a smaller light leakage and a larger extinction ratio. 3) From the measurement results of Example 3 and Comparative Example 3, the light separation can be more accurately performed in the Example having the non-optical polymer. 4) From the measurement results of Example 4 and Comparative Example 4, in the example in which the refractive index of the non-optical polymer is larger than that of the clad, the refractive index of the non-optical polymer is smaller than that of the clad. Light leakage is smaller than in the comparative example, and a large extinction ratio can be obtained. 5) From the measurement results of Example 2, Comparative Example 2 and Comparative Example 5,
In Comparative Example 5 in which the core and the non-optical polymer are in direct contact, the light in the core is significantly attenuated. 6) Since Comparative Example 6 uses Ni which is not a light absorbing material,
The leakage light exists in the clad without being attenuated, and the extinction ratio is poor. That is, the effect of the present invention cannot be obtained with a simple light shielding material having no light absorbing property. Since Ni has an excessively high refractive index, it has an adverse effect. 7) As shown in Example 5, not only on a flat substrate,
It is also possible to form an uneven substrate or a groove in the substrate in advance and form an optical waveguide therein.

The following materials can be used as the material for the non-optical polymer. 1) For 1.65 μm (wavelength for future line monitoring) Most polymers can be used as light absorbers. This is because most polymers do not transmit light having a wavelength of about 1.6 μm or more except for special cases such as perfluorinated polymers. 2) For 1.3 and 1.55 μm (current communication wavelength) A substance having a C—H bond that is not directly bound to a benzene ring or a substance having an O—H bond is preferable. This is because in the case of such a material, the absorption band of the C—H or O—H bond extends to 1.3 and 1.55 μm, and these lights are absorbed. As a specific example, most common polymers are applicable. Examples thereof include transparent resins such as polycarbonate, polystyrene, PMMA, PET and polyimide, turbid resins such as polyethylene and polypropylene due to crystallinity, and elastomers such as EVA. Furthermore, molecules having C—H or O—H bonds, or polymers including particles can also be used. For example, it is a polymer in which a general-purpose dye such as rhodamine B or Neil Blue is dissolved or dispersed, or a polymer in which carbon black is dispersed. In this case, since the added molecules or particles play a role of absorbing leakage light, the resin serving as the base polymer may be a communication wavelength transmitting polymer such as fluorinated polyimide or deuterated PMMA. Further, the molecules and particles to be dispersed are not limited to those having C—H or O—H bond, and are not particularly limited as long as they are substances that absorb the light having the wavelengths of 1.3 and 1.55 μm. For example, germanium, P
The bS particles and the like are raised. 3) Visible light region A polymer having an absorption band at the wavelength of the used light, or a polymer to which a dye having an absorption band is added is preferable. For example, when the used light is near the short wavelength such as blue, one that absorbs blue is necessary, and one that looks like a brown system or a black system when viewed through the light is applicable. Further, when the used light is near the long wavelength, a polymer that absorbs red color or a polymer to which those substances are added is preferable.

As for the material, as described above, a material that easily absorbs the light should be selected depending on the wavelength of the light used while taking the value of the refractive index into consideration. Also, in the process of manufacturing the waveguide, even when the upper surface of the waveguide is covered with a light absorber,
It is preferable to use a polymer that is transparent and allows the opposite side to be better observed through the polymer than a darkly colored polymer or an opaque polymer because of the advantage that a microscope can be observed from above after the waveguide is manufactured.

Further, the waveguide structure may be a flat plate type waveguide as a whole, and may have a single-layered core, a multi-layered core, or a combination of upper and lower cores. good.

The method for molding the non-optical polymer is not particularly limited. A grooved non-optical polymer molded body may be prepared by using a general polymer molding method by injection or molding, or only a necessary portion is dry or wet etched after the non-optical polymer coating film is prepared. May be used for groove processing. The non-optical polymer itself may be used as the waveguide substrate, or a substrate such as a Si wafer may be used as the waveguide substrate and the non-optical polymer may be provided thereon. Furthermore, the cross-sectional shape of the groove does not have to be particularly rectangular, and may have any shape.

[0029]

According to the first aspect, as described above,
A non-optical polymer layer having at least one groove is provided on a substrate, and at least a part of a clad made of an optical polymer is embedded in the groove, and the optical refractive index is higher than that of the clad in the clad. Since a large core is provided, there is an excellent effect that it is possible to reduce the amount of expensive optical polymer used for cladding. According to claim 2, the light transmission loss of the non-optical polymer is 0.2 than the light transmission loss of the clad.
Since it is larger than dB / cm, there is an excellent effect that the disturbance of the signal light due to the leaked light can be avoided.

[Brief description of the drawings]

1A to 1D are explanatory views of a manufacturing process of Example 1 of a plate type optical waveguide according to the present invention.

FIG. 2 is a structural formula of a perfluorinated polyimide serving as a clad material in Example 1.

FIG. 3 is another structural formula of the perfluorinated polyimide used as the core material of Example 1.

4 (a) to 4 (d) are explanatory views of a manufacturing process according to the second embodiment of the present invention.

5 (a) and 5 (b) are structural formulas of a fluorinated polyimide as a clad material and a core material of Example 2, respectively.

6 (a) and 6 (b) are manufacturing process explanatory diagrams of Embodiment 3 of the present invention.

7A and 7B are explanatory views of a manufacturing process according to the fourth embodiment of the present invention.

8 (a) to 8 (c) are explanatory views of a manufacturing process according to a fifth embodiment of the present invention.

FIG. 9 is a perspective view of a conventional flat plate type optical waveguide.

FIG. 10 is a cross-sectional view of another conventional flat plate type optical waveguide.

FIG. 11 is a cross-sectional view of another conventional flat plate type optical waveguide.

FIG. 12 is a plan view of still another conventional flat plate type optical waveguide.

[Explanation of symbols]

11, 51 Substrate 12 Polyimide film 13, 15, 32, 42, 52, 52a Groove 14, 33, 54, 43 Clad 16, 34, 44, 55 Core 17 Adhesive 18, 22, 35, 46, 57 1st port 19, 20, 23, 36, 47, 58 Second port 21, 45, 56 Heater 24, 37, 48, 59 Third port 31, 41 Molded body 38 Fourth port 53 Polyimide

Claims (4)

[Claims] 1. A non-optical polymer layer having at least one groove is provided on a substrate, and at least a part of a clad made of an optical polymer is embedded in the groove, and the clad is contained in the clad. A flat plate type optical waveguide characterized in that a core having a larger optical refractive index is provided. 2. The light transmission loss of the non-optical polymer is
2. The plate type optical waveguide according to claim 1, wherein the optical transmission loss of the clad is larger by 0.2 dB / cm or more. 3. The distance between the core and the light absorber is 20 μm.
The flat optical waveguide according to claim 2, wherein the flat optical waveguide has a length of m or more. 4. The flat type optical waveguide according to claim 1, wherein the refractive index of the light absorber is equal to or higher than the refractive index of the clad.