JP2002350661A - Optical waveguide element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide element which exhibits low light propagation loss even if there are dents in a sectional shape after embedment of a core material without increasing the number of process steps. SOLUTION: A clad 1 subjected to hollow grooving of a width 10 μm and depth 12 μm is formed by injection molding or the like. These grooves are then spin coated with a polyamide acid solution of a resin concentration 15 wt.% which is the precursor of a polyimide as the core material 2 and thereafter the polyamide acid is imidized by heat treatment. The dent depth 12 attains 5 μm greater than the thickness 11 (2 μm) of the core film formed except in the grooves. When the grooves are then coated with the polyamide acid solution to constitute an upper clad is coated by a method, such as spin coating, and is imidized by heating, by which the polymeric optical waveguide having a width 10 μm and a height 7 μm is spuriously obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide device applicable to optical components such as an optical integrated circuit, an optical interconnection, and an optical multiplexing / demultiplexing device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As an optical component or a base material of an optical fiber, inorganic materials such as quartz glass and multi-component glass, which are characterized by low light propagation loss and a wide transmission band, are widely used.

Recently, a polymer-based material has been developed, and is attracting attention as a material for an optical waveguide because it is superior in workability and price as compared with an inorganic material. For example, a flat plate type having a core-clad structure in which a polymer having excellent transparency such as polymethyl methacrylate (PMMA) or polystyrene is used as a core and a polymer having a lower refractive index than the core material is used as a clad material. An optical waveguide has been manufactured (Japanese Patent Application Laid-Open No. 3-188402). Further, Matsuura et al. Have realized a low-loss planar optical waveguide using polyimide which is a transparent polymer having high heat resistance (Japanese Patent Laid-Open No. 2-110500).

However, in each of these methods, when forming a core structure on the surface of a cladding layer,
It is necessary to form a core pattern using a photoresist for each sheet, and to perform concavo-convex processing by reactive ion etching and the like following this, and there have been problems in terms of mass productivity and cost reduction.

[0005] Therefore, mass production is performed by a method in which a mold having an irregular surface formed on a core pattern of a waveguide is pressed against a polymer in a molten state or a solution state and the polymer is cured as it is to transfer the irregularities to the polymer surface. Studies are being made to improve the performance. After the core material, which has a higher refractive index than the substrate when cured, is dropped in the monomer state on the polymer clad substrate surface with fine grooves formed on the surface, the surface is swept with a squeegee etc. After filling the monomer material only inside, polymerize and cure,
There is a method of manufacturing a polymer optical waveguide.

[0006]

However, in the method of embedding the monomer material into the groove with a squeegee, the embedding amount differs depending on whether the direction of squeegee traverses the groove or at right angles thereto. Are different.

[0007] As a countermeasure, a core material is first buried in a thicker thickness and then etched back by plasma etching or the like to remove an extra core. In this method, a plasma etching apparatus is required, and the manufacturing cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and shows a low light propagation loss even if there is a depression in the cross-sectional shape after embedding the core material without increasing the number of steps. An object of the present invention is to provide an optical waveguide element and a method for manufacturing the same.

[0009]

As a result of intensive studies, the present inventor has found that the above problems can be solved by optimizing the core recess depth and the core film thickness, and has completed the present invention.

[1] The present invention comprises a clad member having a concave groove on the surface, and a core member arranged so as to cover the concave groove and the periphery of the concave groove. The optical waveguide device is characterized in that there is a depression that is reduced by the concave groove, and the depth of the depression is equal to or greater than the thickness of the core member around the concave groove.

[2] In the present invention, the core member is preferably formed of a polymer material. [3] Further, the present invention preferably includes a second clad member arranged so as to cover the surface of the core member.

[4] Also, the present invention provides a step of preparing a first clad member having a concave groove on the surface, and applying a first liquid polymer material on the first clad member, A step of covering the periphery of the concave groove, and heat-treating the applied first liquid polymer material to form a depression on the surface that is lower than the periphery of the concave groove, and that the depth of the depression is around the concave groove. A step of forming a core member having a thickness equal to or larger than the thickness, a step of applying a second liquid polymer material on the first clad member and the core member, and a heat treatment of the applied second liquid polymer material And forming a second clad member.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. Here, the production of a polyimide optical waveguide using a polyamic acid solution which is a precursor of polyimide will be described as an example, but the production is performed using a resin solution of an optical material other than the polyamic acid solution as a material of the optical waveguide. It is of course possible to do so.

FIG. 1 is a process diagram showing an example of an optical waveguide manufacturing process according to the present invention. 1 is a grooved lower clad, 2 is a core material, and 3 is an upper clad.
FIG. 2 is a partially enlarged view showing an example of the embedded cross-sectional shape of the core. Reference numeral 11 in FIG. 2 denotes a core film thickness around the concave groove, and reference numeral 12 denotes a depression depth in the concave groove.

First, a clad 1 having a width of 10 μm and a depth of 12 μm is formed by injection molding or the like.
Next, a polyamic acid solution having a resin concentration of 15 wt%, which is a polyimide precursor, is spin-coated as a core material 2 in the groove, and then imidized by heat treatment. At this time, the core film thickness 11 formed in portions other than the groove portions is 2 μm. This film thickness can be adjusted only by changing the rotation speed of spin coating. The depression depth 12 is 5 μm, which is larger than the thickness of the core formed except for the groove.

Next, a polyamic acid solution to be an upper clad is coated by spin coating or the like, and is heated and imidized. At this time, a core having a width of 10 μm and a height of 7 μm has been pseudo-formed. In this manner, a polymer optical waveguide can be manufactured using the method of embedding the polymer in the solution state in the groove.

[0017]

The present invention will be described in more detail with reference to several examples. It is apparent that an unlimited number of polymer optical waveguides of the present invention can be obtained by using solutions of various polymers having different molecular structures. Therefore, the present invention is not limited to only these examples.

(Example 1) 2, formed by injection molding
2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2-bis (trifluoromethyl) -4,4′-diaminobiphenyl (TFDB) width 10 μm × depth 12 μm X length 5cm
6F to be the core material on 100 grooved polyimide
15w of DA and 4,4'-oxydianiline (ODA)
A t% polyamic acid solution was spin-coated and imidized by heating. The protruding thickness 11 of the core was 1.5 μm, and the recess depth 12 of the groove was 5 μm.

Next, from above, 1 of 6FDA / TFDB
A 5 wt% polyamic acid solution was applied by spin coating, and heated and imidized to form an upper clad.

In this way, a core diameter of 10 μm ×
A 7 μm embedded polyimide optical waveguide was produced.

The coupling loss between the optical fiber having a mode field diameter of 9.5 μm and this optical waveguide was about 0.4 dB at both ends, and the light propagation loss was 0.5 dB / cm. Also,
There was no light leakage to the protruding part. This is the same performance as the case where the core material other than the core portion described below is removed, and it is understood that a complicated removal process does not need to be used.

(Comparative Example 1) 6F formed by injection molding
DA / TFDB width 10 μm × depth 7 μm × length 5 cm
6F to be the core material on 100 grooved polyimide
DA / ODA 20wt% polyamic acid solution with thickness 10
The solution was dropped under the condition of μm, and imidized by heating.

Next, excess core material protruding from the groove was removed by dry etching. Next, from above, 6F
A 15 wt% polyamic acid solution of DA / TFDB was applied by spin coating and heat imidized to form an upper clad.

The coupling loss between the optical fiber having a mode field diameter of 9.5 μm and this optical waveguide was about 0.4 dB at both ends, and the light propagation loss was 0.5 dB / cm. However, the number of dry etching steps that are not suitable for mass productivity or the like increases.

(Comparative Example 2) 6F formed by injection molding
DA / TFDB width 10 μm × depth 7 μm × length 5 cm
6F to be the core material on 100 grooved polyimide
DA / ODA 20wt% polyamic acid solution with thickness 7μ
The mixture was dropped under the condition of m, and imidized by heating. The core protrusion thickness 11 was 7 μm, and the recess depth 12 of the groove was 4 μm.

Next, from above, 1 of 6FDA / TFDB
A 5 wt% polyamic acid solution was applied by spin coating, and heated and imidized to form an upper clad.

At this time, the light leaked to the protruding portion of the core. Therefore, the light propagation loss is 10 dB / cm
That's it.

[0028]

As described above in detail, according to the present invention, by optimizing the relationship between the depth of the dent present on the surface of the core member and the thickness of the core member around the concave groove, the core is formed around the concave groove. Light propagation loss can be reduced even if the members remain. Therefore, an optical waveguide element can be manufactured by applying a polymer material in a solution state, and polymer optical waveguides of various materials can be mass-produced at low cost.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of manufacturing an optical waveguide including a step of embedding a core material according to the present invention.

FIG. 2 is a partially enlarged view showing an example of an embedded cross-sectional shape of a core.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Groove processing lower clad 2 Core 3 Upper clad 11 Core film thickness around a concave groove 12 Depression depth in a concave groove

Claims (4)

[Claims] A cladding member having a concave groove on a surface thereof; and a core member disposed so as to cover the concave groove and the periphery of the concave groove, wherein the surface of the core member is lower in the concave groove than in the peripheral groove. An optical waveguide device having a depression, wherein the depth of the depression is equal to or greater than the thickness of the core member around the concave groove. 2. The optical waveguide device according to claim 1, wherein the core member is formed of a polymer material. 3. The semiconductor device according to claim 1, further comprising a second clad member disposed so as to cover a surface of the core member.
An optical waveguide device as described in the above. 4. A step of preparing a first clad member having a groove on the surface, and a step of applying a first liquid polymer material on the first clad member to cover the groove and the periphery of the groove. And heat-treating the applied first liquid polymer material to have a depression on the surface that is lower in the groove than in the vicinity of the groove, and the depth of the depression is equal to or less than the thickness in the vicinity of the groove. Forming a large core member; applying a second liquid polymer material onto the first clad member and the core member; heat treating the applied second liquid polymer material to form a second liquid polymer material; Forming a clad member.