JP2004133103A - Polymer optical waveguide and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer waveguide having a band-like core layer with smooth side surfaces. <P>SOLUTION: This polymer optical waveguide 50 is provided with a lower clad layer 18, a band-like core layer 22, and an upper clad layer 24 respectively consisting of a polymeric organic compound on a substrate 16. A coating film 52 consisting of the same polymeric organic compound as the core layer 22 intervenes between the upper and side surfaces of the core layer 22 and the upper clad layer 24, and between the lower clad layer 18 and the upper clad layer 24. The coating film 52 has a thickness of 20 nm or more and 1 μm or less. The smoothed side surfaces of the core 22 cause little optical loss in the polymer optical waveguide 50 of the present embodiment. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polymer optical waveguide and a method for manufacturing the same, and more particularly, to a film-shaped low loss excellent in flexibility, used for an optical component such as an interconnection optical component, an optical multiplexer, or an optical demultiplexer. The present invention relates to a polymer optical waveguide and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, inorganic materials such as quartz glass and multi-component glass have been widely used as base materials for optical components or optical fibers because of their low light propagation loss and wide transmission band. Optical components, optical fibers, and the like using high-priced polymer-based materials, which have better workability than materials, have been developed.
For example, as an optical fiber using a polymer material for an optical waveguide, a highly transparent polymer material such as polymethyl methacrylate (PMMA) or polystyrene is used as a core, and a plastic having a lower refractive index than the core material is used as a cladding material. A planar polymer optical waveguide having a core / cladding structure has been manufactured. In addition, a planar polymer optical waveguide using polyimide or polysiloxane, which is a polymer having excellent heat resistance and high transparency, has also been manufactured.
[0003]
Here, as an example of the planar polymer optical waveguide, a method of manufacturing the planar polymer optical waveguide disclosed in Japanese Patent Application Laid-Open No. 8-304650 will be described with reference to FIG. 5 (a) to 5 (c) are cross-sectional views of respective steps when a flat-plate type polymer optical waveguide is manufactured by the method disclosed in the above-mentioned publication.
Prior to the production of a polymer optical waveguide, a copper film 14 having a thickness of about 100 nm is formed on a silicon substrate 12 by a sputtering method to form a substrate 16, and an embedded polymer optical waveguide is produced on the substrate 16.
First, as shown in FIG. 5A, a lower cladding layer 18 made of a solution-type transparent high-molecular organic compound is formed on a substrate 16 by spin coating. Subsequently, a core layer 20 made of a polymer organic compound having a higher refractive index than that of the lower cladding layer 18 is formed on the lower cladding layer 18 by spin coating.
Next, a resist mask (not shown) having a stripe pattern is formed on the core layer 20, and the core layer 20 is etched by a reactive ion etching method using the resist mask as an etching mask, as shown in FIG. Then, it is processed into a band-shaped core layer 22.
Further, as shown in FIG. 5C, an upper cladding layer 24 made of the same high molecular weight organic compound as the lower cladding layer 18 is formed on the lower cladding layer 18 and the core layer 22 by a spin coating method. Then, a polymer optical waveguide structure 26 including the lower cladding layer 18, the core layer 22, and the upper cladding layer 24 is formed.
Next, the polymer optical waveguide structure 26 is peeled from the substrate 16 to obtain a polymer optical waveguide film.
[0004]
Also, Japanese Patent Application Laid-Open No. 10-30961 discloses a method of manufacturing an inclined end face (micromirror) for optical path conversion having a desired inclination angle at a desired position of a polymer optical waveguide.
Here, with reference to FIG. 6, a method for manufacturing a planar polymer optical waveguide having a 45 ° inclined end surface on one side end surface disclosed in the forward tilt publication will be described. FIGS. 6A and 6B are cross-sectional views illustrating a method for manufacturing a planar polymer optical waveguide having a 45 ° inclined end face on one end face.
According to the forward tilt publication, as shown in FIG. 6A, a lower cladding layer 34, a core layer 36 extending on the lower cladding layer 34, and an upper part extending on the core layer 36 are formed on the substrate 32. A planar polymer optical waveguide 40 having a laminated structure of the cladding layer 38 is formed.
Next, as shown in FIG. 6B, the lower cladding layer 34, the core layer 36, and the upper cladding layer 38 are subjected to grinding using a diamond blade 42 whose cutting edge is processed to approximately 90 °, thereby forming a V-groove. It is stated that by forming the 44, a 45 ° inclined end surface 46 can be formed.
[0005]
[Patent Document 1]
JP-A-8-304650 (page 2)
[Patent Document 2]
JP-A-10-30961 (paragraph [0068])
[0006]
[Problems to be solved by the invention]
By the way, according to Japanese Patent Application Laid-Open No. 8-304650, in forming the polymer optical waveguide structure 26, the core layer 20 is etched by a reactive ion etching method to form a band-shaped pattern. The core layer 20 is etched so that the side surface of the strip-shaped core layer 22 becomes a smooth surface orthogonal to the lower clad layer 18 due to disorder of the mask edge and irregular etching in the lateral direction. It is difficult.
As a result, the side surface of the core layer 22 has poor smoothness, as shown in FIG. Therefore, the propagation loss of the produced polymer optical waveguide 26 increases. In this case, it is difficult to put the polymer optical waveguide into practical use. Therefore, in order to reduce the optical loss and put the polymer optical waveguide into practical use, it is necessary to maintain the smoothness of the processed surface after etching.
[0007]
According to Japanese Patent Application Laid-Open No. Hei 10-300961, the V-groove 44 is formed by dicing using the diamond blade 42 in forming the 45 ° inclined end face. It is difficult to maintain good smoothness of the surface 46, and as shown in FIG. 7B, the 45 ° inclined end surface 46, that is, the reflection end surface is roughened.
The surface roughness formed on the reflection surface increases the reflection loss. Therefore, it is necessary to maintain the smoothness of the reflecting mirror surface in order to reduce the optical loss of the polymer optical waveguide.
[0008]
Therefore, an object of the present invention is to provide a polymer optical waveguide in which the side surface of the strip-shaped core layer is a smooth surface, a polymer optical waveguide having a smooth reflective end face, and a method for manufacturing the same.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a polymer optical waveguide according to the present invention (hereinafter, referred to as a first invention) includes a lower clad layer, a band-shaped core layer, and an upper clad layer made of a polymer organic compound, respectively. In the provided polymer optical waveguide,
It is characterized in that a coating film made of a high-molecular organic compound is interposed between the upper and side surfaces of the core layer and the upper clad layer.
[0010]
In the first aspect, the side surface of the core layer is covered with the smooth coating film to make the side surface of the core layer smooth, so that the optical loss of the polymer optical waveguide can be reduced.
[0011]
Further, another polymer optical waveguide according to the present invention (hereinafter, referred to as a second invention) includes a lower cladding layer made of a polymer organic compound, a core layer extending on the lower cladding layer, and a core layer, respectively. In the polymer optical waveguide having an upper clad layer extending upward, and a groove having a groove surface formed by an inclined end surface, the upper clad layer, the core layer, and the lower clad layer,
It is characterized in that a coating film made of a high molecular weight organic compound is formed on the inclined end face.
[0012]
In the second aspect of the present invention, the inclined end face is covered with a smooth coating to make the inclined end face smooth, so that the optical loss due to the reflection at the inclined end face of the polymer optical waveguide can be reduced.
The angle of the inclined end surface with respect to the core layer is not particularly limited.
[0013]
Preferably, the refractive index of the coating film made of a high molecular organic compound is larger than that of the lower clad layer and the upper clad layer, and is equal to or smaller than that of the core layer.
Further, the thickness of the coating film made of a high molecular organic compound may be 20 nm or more and 1 μm or less. If the thickness is less than 20 nm, the effect of the coating film is poor, and even if the film thickness exceeds 1 μm, the effect of the present invention does not increase correspondingly despite the increase in cost.
[0014]
The method for producing a polymer optical waveguide according to the present invention (hereinafter, referred to as a first invention method) is a method for producing a polymer having a lower clad layer, a strip-shaped core layer, and an upper clad layer made of a polymer organic compound, respectively. In the method for manufacturing an optical waveguide,
When the core layer formed on the lower clad layer is etched to form a band-shaped core layer, and then when forming the upper clad layer on the band-shaped core layer,
A thin film made of a high molecular weight organic compound is formed by a coating method on the upper and side surfaces of the band-shaped core layer and the lower clad layer exposed from the band-shaped core layer, and the side surfaces of the band-shaped core layer are smoothed. Is characterized in that an upper clad layer is formed on the core layer.
[0015]
Further, another method for producing a polymer optical waveguide according to the present invention (hereinafter, referred to as a second invention method) includes a lower cladding layer made of a polymer organic compound and a core layer extending on the lower cladding layer, respectively. In the method for producing a polymer optical waveguide having an upper clad layer extending over the core layer, and having a groove having a groove surface formed of an inclined end surface over the upper clad layer, the core layer, and the lower clad layer,
When the upper clad layer, the core layer, and the lower clad layer are cut to form a groove having a groove surface composed of an inclined end face,
The method is characterized in that a thin film made of a high-molecular organic compound is formed on the inclined end face by a coating method to smooth the inclined end face.
[0016]
In the first and second invention methods, the coating method for forming a thin film is not limited, and is applied by, for example, a spin coating method.
The first and second aspects of the present invention can be applied to the polymer optical waveguide without limitation on the types of the high molecular organic compounds constituting the lower cladding layer, the core layer, and the upper cladding layer and the thickness of each layer.
The same applies to the first and second invention methods.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the accompanying drawings by way of example embodiments.
Embodiment 1 of polymer optical waveguide
This embodiment is an example of an embodiment of the polymer optical waveguide according to the first invention, and FIG. 1 is a cross-sectional view showing a configuration of the polymer optical waveguide of the embodiment. 1 which are the same as those in FIG. 5 are denoted by the same reference numerals.
As shown in FIG. 1, the polymer optical waveguide 50 of the present embodiment includes a lower clad layer 18, a band-shaped core layer 22, and an upper clad layer 24 made of a polymer organic compound on a substrate 16, respectively. It is a polymer optical waveguide.
[0018]
In the present embodiment, a coating film 52 made of the same high molecular weight organic compound as the core layer 22 is formed between the upper and side surfaces of the band-shaped core layer 22 and the upper cladding layer 24, and between the lower cladding layer 18 and the upper cladding layer 24. And intervenes between them.
In the present embodiment, the coating film 52 is formed of the same high molecular weight organic compound as the core layer 22, and the thickness of the coating film 52 is not less than 20 nm and not more than 1 μm.
However, the material of the coating film 52 does not necessarily need to be the same high molecular weight organic compound as the core layer 22 and has a refractive index larger than that of the lower and upper cladding layers 18 and 24 and is the same as that of the core layer 22. It is better if it is smaller.
[0019]
Since the side surface of the core layer 22 is covered with the smooth coating film 52 having the same refractive index as that of the core layer 22 and has a smooth surface, the polymer optical waveguide 50 of the present embodiment has a small optical loss.
[0020]
Embodiment 1 of manufacturing method of polymer optical waveguide
This embodiment is an example of an embodiment in which the method for producing a polymer optical waveguide according to the first invention method is applied to the production of the above-described polymer optical waveguide 50. FIGS. FIGS. 3A and 3B are cross-sectional views of respective steps when a polymer optical waveguide is manufactured according to the method of the embodiment. The same parts as those in FIG. 5 among the parts in FIG. 2 are denoted by the same reference numerals.
As in the conventional method, a resist mask 54 having a band-shaped pattern is formed on the core layer 20, and then the core layer 20 on the lower cladding layer 18 is etched using reactive ion etching or the like, and FIG. As shown in a), a strip-shaped core layer 22 is formed.
[0021]
After removing the etching mask 54, the same high molecular organic compound material as that of the core layer 20 is spin-coated on the upper and side surfaces of the core layer 22 and on the lower cladding layer 18 in order to improve the smoothness of the side surfaces of the core layer 22. A thin film 52 having a coating thickness of 20 nm or more and 1 μm or less is formed by a coating method such as a coating method.
Subsequently, the polymer optical waveguide 50 shown in FIG. 1 can be manufactured by forming the upper clad layer 24 on the core layer 22 and the lower clad layer 18 as in the conventional case.
[0022]
Embodiment 2 of polymer optical waveguide
This embodiment is an example of an embodiment of the polymer optical waveguide according to the second invention, and FIG. 3 is a cross-sectional view showing a configuration of the polymer optical waveguide of the embodiment. The same parts as those in FIG. 6 among the parts in FIG. 3 are denoted by the same reference numerals.
The polymer optical waveguide 60 of the present embodiment is a polymer optical waveguide used for an optical path conversion element and the like, and as shown in FIG. A substrate 32 includes a core layer 36 extending over the layer 34 and an upper cladding layer 38 extending over the core layer 36.
A V-shaped groove 44 having a 45 ° inclined end surface 46 is formed over the upper clad layer 38, the core layer 36, and the lower clad layer 34.
Further, in the present embodiment, a coating 62 made of the same high molecular weight organic compound as the core layer 36 is formed on the 45 ° inclined end surface 46. However, the material of the coating film 62 does not necessarily need to be the same high molecular weight organic compound as the core layer 36, and has a higher refractive index than the lower and upper cladding layers 34 and 38 and is the same as the core layer 36 or the core layer 36. It is better if it is smaller.
[0023]
In the present embodiment, since the 45 ° inclined end surface 46 is covered with a smooth coating film having the same refractive index as the core layer 36 and has a smooth surface, light loss due to reflection at the 45 ° inclined end surface 46 is reduced. Can be reduced.
[0024]
Embodiment 2 of manufacturing method of polymer optical waveguide
The present embodiment is an example of an embodiment in which the method for producing a polymer optical waveguide according to the second invention method is applied to the production of the above-described polymer optical waveguide 60, and FIG. It is sectional drawing of one process at the time of producing a polymer optical waveguide. 4 that are the same as those in FIG. 6 are denoted by the same reference numerals.
A lower cladding layer 34, a core layer 36, and an upper cladding layer 38 are formed on a substrate 32 in the same manner as before, and then, as shown in FIG. 34 is cut with a diamond blade or the like to form a V-shaped groove 44 having a 45 ° inclined end surface 46.
Next, as shown in FIG. 3, a thin film 62 having a thickness of 20 nm or more and 1 μm or less made of the same high molecular organic compound as the core layer 36 is formed on the 45 ° inclined end surface 46 by a coating method such as a spin coating method. The 45 ° inclined end surface 46 is smoothed.
[0025]
【The invention's effect】
According to the first invention, a coating film composed of a high molecular weight organic compound is interposed between the upper and side surfaces of the core layer and the upper cladding layer, and the side surface of the core layer is covered with a smooth coating film. The light loss can be reduced by smoothing the side surface.
According to the second aspect of the present invention, a coating film made of a high molecular weight organic compound is formed on the inclined end surface and covered with a smooth coating film, and the inclined end surface is smoothed, so that light loss accompanying reflection at the inclined end surface is obtained. Can be reduced.
The first and second invention methods realize methods for easily fabricating the polymer optical waveguide according to the first and second inventions, respectively.
[0026]
ADVANTAGE OF THE INVENTION According to this invention, the deterioration of the surface smoothness which arises at the time of forming a core and a reflection mirror in a polymer optical waveguide can be improved, and the propagation loss and reflection loss of a waveguide can be reduced effectively. Further, the present invention can be widely applied without depending on the type of the polymer material constituting the polymer optical waveguide. Further, the optical loss of the polymer optical waveguide can be improved without distinction between single mode and multimode.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a polymer optical waveguide according to a first embodiment.
FIGS. 2A and 2B are cross-sectional views of respective steps when a polymer optical waveguide is manufactured according to the method of Embodiment 1. FIG.
FIG. 3 is a cross-sectional view illustrating a configuration of a polymer optical waveguide according to a second embodiment.
FIG. 4 is a cross-sectional view of one step when a polymer optical waveguide is manufactured according to the method of Embodiment 2;
FIGS. 5 (a) to 5 (c) are cross-sectional views of respective steps when manufacturing a planar polymer optical waveguide by a method according to JP-A-8-304650.
FIGS. 6A and 6B are cross-sectional views illustrating a method of manufacturing a planar polymer optical waveguide having a 45 ° inclined end surface on one end surface.
FIGS. 7A and 7B are cross-sectional views illustrating a problem of a conventional polymer optical waveguide.
[Explanation of symbols]
12 silicon substrate, 14 copper film, 16 substrate, 18 lower clad layer, 20 core layer, 22 band-shaped core layer, 24 upper clad layer, 26 polymer Optical waveguide structure, 32 substrate, 34 lower clad layer, 36 core layer, 38 upper clad layer, 40 polymer optical waveguide structure, 42 diamond blade, 44 V groove, 46: 45 ° inclined end face, 50: polymer optical waveguide of the embodiment, 52: coating film, 54: resist mask, 60: polymer optical waveguide of the embodiment, 62: coating film.

Claims (8)

In a polymer optical waveguide having a lower clad layer, a band-shaped core layer, and an upper clad layer made of a polymer organic compound, respectively,
A polymer optical waveguide, wherein a coating film made of a polymer organic compound is interposed between the upper and side surfaces of the core layer and the upper clad layer. A lower cladding layer made of a high-molecular organic compound, a core layer extending on the lower cladding layer, and an upper cladding layer extending on the core layer, and a groove having a groove surface composed of an inclined end face is formed on the upper cladding layer. In the polymer optical waveguide having the layer, the core layer, and the lower clad layer,
A polymer optical waveguide, wherein a coating film made of a polymer organic compound is formed on the inclined end face. 3. The polymer photoconductor according to claim 1, wherein the refractive index of the coating film made of a high molecular organic compound is higher than that of the lower cladding layer and the upper cladding layer, and is equal to or smaller than that of the core layer. Wave path. The polymer optical waveguide according to any one of claims 1 to 3, wherein the thickness of the coating film made of a high molecular organic compound is 20 nm or more and 1 µm or less. In the method for producing a polymer optical waveguide having a lower clad layer, a band-shaped core layer, and an upper clad layer, each of which is made of a polymer organic compound,
When the core layer formed on the lower clad layer is etched to form a band-shaped core layer, and then when forming the upper clad layer on the band-shaped core layer,
On the upper and side surfaces of the band-shaped core layer, and on the lower clad layer exposed from the band-shaped core layer, a thin film made of a high molecular organic compound is formed by a coating method, and the side surfaces of the band-shaped core layer are smoothed. Forming an upper clad layer on the core layer of (1). A lower cladding layer made of a high-molecular organic compound, a core layer extending on the lower cladding layer, and an upper cladding layer extending on the core layer, and a groove having a groove surface composed of an inclined end face is formed on the upper cladding layer. In the method for producing a polymer optical waveguide having a layer, a core layer, and a lower clad layer,
When the upper clad layer, the core layer, and the lower clad layer are cut to form a groove having a groove surface composed of an inclined end face,
A method for producing a polymer optical waveguide, characterized in that a thin film made of a high-molecular organic compound is formed on an inclined end face by a coating method to smooth the inclined end face. 7. The coating film according to claim 5, wherein the coating film is formed of a high molecular weight organic compound having a refractive index higher than that of the lower cladding layer and the upper cladding layer and smaller than or equal to that of the core layer. Manufacturing method of molecular optical waveguide. The method for producing a polymer optical waveguide according to any one of claims 5 to 7, wherein the thickness of the coating film made of a high-molecular organic compound is 20 nm or more and 1 µm or less.

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