JPH01219803A - Production of optical waveguide - Google Patents

Abstract

PURPOSE:To shorten the time for production and to obtain a large refractive index difference by providing a stage which removes the residual monomer of a 2nd org. material failing to make photopolymn. by using a solvent which does not dissolve the polymers of the 1st and 2nd org. materials and dissolves the monomer of the 2nd org. material. CONSTITUTION:The residual monomer of the 2nd org. material failing to make the photopolymn. is removed by such a method of immersing the entire part of a substrate into the solvent (e.g.; ethanol) which does not dissolve the polymers of both the 1st and 2nd org. materials (prescribed PMMA, styrene monomers) and dissolves the monomer of the 2nd org. material. The solvent penetrates rapidly into the polymer of the 1st org. material and the residual monomer existing in said polymer dissolves into the solvent and is thus rapidly released to the outside of the polymer when the entire part of the substrate after the photopolymn. is immersed into the solvent. A short period of about 1min suffices with the time required for the residual monomer to be removed in such a manner and, therefore the time for production over the entire part is shortened. In addition, the temp. of the solvent may be at room temp. and the large refractive index difference is obtainable.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for manufacturing an optical waveguide using photopolymerization of an organic material, and aims to reduce manufacturing time and obtain a large refractive index difference. at least a step of forming a four-wave path material comprising a monomer of a second organic material in a polymer of the first organic material, and causing photopolymerization of the monomer in a region that will become an optical waveguide. In the method of manufacturing an optical waveguide, the method includes at least a solvent that does not dissolve the first and second organic material polymers and dissolves a monomer of the second organic material; A step of removing residual monomer of the second organic material that has not been photopolymerized using a solvent that does not dissolve the highly polymerized polymer of the organic material and dissolves the low polymerized polymer of the second organic material. Configure it as follows.

[Industrial application field]

The present invention relates to a method for manufacturing an optical waveguide using photopolymerization of an organic material.

Currently, in the fields of optical communication and optical information processing, much research is being conducted on waveguide optical devices to reduce loss, reduce size, reduce weight, and improve reliability of optical circuits. Accordingly, optical wiring technology between optical functional elements using optical waveguides has become important.

[Conventional technology]

Conventionally, research has been conducted using glass, semiconductors, lithium niobate, etc. as materials for optical waveguides.

However, optical waveguides using these materials require complicated steps such as thermal diffusion and vacuum processing in the manufacturing process, and have the disadvantage that the degree of freedom in the refractive index that can be obtained is small.

In contrast, optical waveguides using organic materials such as polycarbonate and polymethyl methacrylate (PMMA) are also being considered. According to this, by utilizing photopolymerization, manufacturing becomes simple, a large refractive index difference can be obtained, and the advantages are that it is inexpensive and the transmission IM loss is small. A conventional method for manufacturing an optical waveguide using this photopolymerization is as follows.

(i) A substrate made of glass or the like is coated with a polymer (eg, PMMA) containing a monomer (eg, styrene monomer) as a waveguide material.

(ii) selectively polymerizing the monomer with ultraviolet light to create a difference in refractive index between the core layer and the kraft layer; That is, the region where the monomer is photopolymerized becomes a core region with a high refractive index, and the surrounding region becomes a raft region with a refractive index lower than that of the core layer.

(iii) Remove unreacted residual monomers that have not undergone photopolymerization from the cladding region. This removal is performed by baking in vacuum or air.

[Problem to be solved by the invention]

In the conventional manufacturing method, the residual monomer is removed by baking as shown in (iii) above, which requires a long time (for example, 30 minutes), which increases the overall manufacturing time. There was a problem.

Furthermore, since the above baking is performed at a high temperature of, for example, about 90°C, there is a risk that the residual monomer that should be removed will undergo thermal polymerization, which will reduce the difference in refractive index between the core region and the cladding region. there were. Furthermore,
There was also a risk that the refractive index distribution would be blunted due to thermal diffusion of the polymer in the core region to the cladding region.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to shorten the manufacturing time and to obtain a large refractive index difference.

[Means to solve the problem]

In the present invention, first, a waveguide material containing at least a monomer of a second organic material (eg, styrene monomer) in a polymer of a first organic material (eg, PMMA) is formed on a substrate.

Subsequently, the monomer is photopolymerized in a region that will become an optical waveguide, thereby creating a difference in refractive index between the core region and the cladding region.

Thereafter, at least a solvent that does not dissolve any of the polymers of the first and second organic materials and can dissolve the monomers of the second organic materials, or a solvent that does not dissolve any of the polymers of the first and second organic materials; A solvent (for example, ethanol) is prepared that does not dissolve the highly polymerized polymer but dissolves the low polymerized polymer of the second organic material. Then, by immersing the entire substrate obtained in the above step in this solvent, residual monomers of the second organic material that did not undergo the above photopolymerization are removed.

[For production]

When the entire photopolymerized substrate is immersed in the above solvent, the solvent quickly penetrates into the polymer of the first organic material. The residual monomer present in the polymer is then dissolved into the solvent and quickly released from the polymer.

In this way, a short time of about 1 minute is sufficient to remove the residual monomer, thereby reducing the overall manufacturing time. Moreover, since the temperature of the solvent is very high and high temperatures unlike conventional baking are not required, there is no need to worry about thermal polymerization of residual monomers, and a large refractive index difference can be obtained.

Furthermore, since the polymer in the core (the polymer of the second organic material) does not thermally diffuse into the cladding, a steep refractive index distribution can be obtained.

〔Example〕

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

FIG. 1 is a manufacturing process diagram of an embodiment of the present invention.

In this example, first, as shown in FIG. It is formed to a thickness of about 2 μm.

In this case, for example, PMMA is mixed with a large amount of solvent (e.g. MM
The above-mentioned craft material 2 is obtained by coating the substrate 1 with a solution obtained by melting A, etc.) on the substrate 1 by a spin-coating method and then drying it.

Next, PMM of the same material is placed on the cladding material 2.
A core material 3 containing styrene monomer (St) in A is formed to have a thickness of, for example, about 3 μm. In this case, for example, a solution prepared by dissolving PMMA and styrene monomer (St) in a large amount of solvent (such as 1.4 dioxane or styrene monomer) is coated on the craft material 2 by a spin coating method, and then, By drying this, the core material 3 described above is obtained. Note that the core material 3 contains, for example, an acetophenone-based initiator as a photopolymerization initiator described below.

Next, as shown in FIG. 1(C), a photomask 4 having a desired waveguide pattern is placed close to the core material 3, and a high-pressure mercury lamp (wavelength: 0.36 to 0.05 cm) is placed over the photomask 4.
41 μm) etc. is irradiated with ultraviolet light.

Then, in the ultraviolet light exposed region 3a of the core material 3 (the region that will eventually become the core layer), the styrene monomer (St) contained therein undergoes photopolymerization to form polystyrene (PSt). , so the non-exposed area 3
A difference in refractive index occurs between the

Thereafter, as shown in FIG. ) and which can dissolve the monomer (here, St) (or a solvent which does not dissolve highly polymerized PMMA and pst but dissolves lowly polymerized pst).Therefore,
The ethanol 5 has soaked into the core material 3 (and the unreacted residual monomers present therein (particularly in the non-exposed areas 3).
Most of SL) in b is dissolved in ethanol 5 and released to the outside as it is. Subsequently, the entire substrate is taken out of the ethanol 5 and washed with water to wash off the ethanol 5.

After that, although not shown, another craft material similar to the cladding material 2 is formed on the core material 3. Through the above steps, an optical waveguide is obtained in which the exposed region 3a made of PMMA containing PSt serves as the core layer, and the surrounding region made only of PMMA serves as the cladding layer.

According to this example, in the step shown in FIG. Since the length is relatively short, the time required to remove the residual St is about 1 minute at most. Therefore, the overall manufacturing time can be significantly shortened compared to the conventional case where long-time baking is used.

Moreover, if the process of removing residual St is completed in a short time as described above, the change over time from 3t to pst can be suppressed to a low level.

Furthermore, the temperature of the ethanol 5 may be room temperature and does not require high temperatures unlike conventional baking, so there is no fear that residual St will undergo thermal polymerization and change into PSt. Therefore, the amount of pst generated in the cladding layer can be suppressed to a minimum, and therefore the difference in refractive index between the core layer and the cladding layer can be maintained large. In order to confirm this effect, the relationship between the exposure amount (exposure time) and the refractive index difference in this embodiment is shown in FIG. 2 in comparison with that in the case of conventional baking. Here, in this example, 1
The figure shows the case of soaking for 30 minutes at 90℃ in the conventional example.
The case where baking was performed for a minute was shown. In the same figure, in the conventional case, only a maximum refractive index difference of about 0.009 can be obtained, whereas in the case of this embodiment, a large refractive index difference of about 0.02, which is more than twice that of the conventional case, can be obtained. ing.

Furthermore, since PSt in the core layer does not thermally diffuse into the cladding layer, a steep refractive index distribution can be obtained.

In the above embodiment, St/PMM is used as the core material 3.
A was used, and PMMA was used as the cladding material 2, but
In addition to these materials, various organic materials that can be made to have a difference in refractive index by photopolymerization can be used.

Furthermore, when a glass substrate is used as the substrate 1, the core material 3 may be directly formed thereon.

Furthermore, as the solvent used to remove the residual monomer, other alcohols such as methanol or isopropyl alcohol may be used instead of the above-mentioned ethanol, or other solvents may be used depending on the various waveguide materials.

Furthermore, the waveguide pattern obtained by exposure may be drawn by scanning a light beam instead of using a photomask as in the above embodiment.

〔Effect of the invention〕

As explained above, according to the present invention, residual monomer that has not been photopolymerized can be removed very quickly, so that the overall manufacturing time can be significantly shortened. Moreover, since high temperatures unlike conventional baking are not required when removing residual monomers, it is possible to prevent thermal polymerization of residual monomers and thermal diffusion of polymer in the core layer to the cladding layer, thereby preventing the gap between the core layer and the cladding layer. can have a steep and large refractive index difference.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are manufacturing process diagrams of one embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between exposure time and refractive index difference in the same embodiment and a conventional example. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Clad material, 3...Core material, 3a...Exposed area, 3b...Non-exposed area, 4...Photomask, 5...Ethanol. Patent Applicant: Fujitsu Ltd. Ugaikou One Embodiment of the Present Invention Exposure r! Time (min) L's Sekii Thread Figure 2

Claims (1)

[Claims] 1) forming a film on the substrate (1) of a waveguide material (3) comprising at least a monomer of a second organic material in a polymer of the first organic material; A method for producing an optical waveguide comprising the step of causing photopolymerization of the monomer in a region that will become an optical waveguide, at least the step of not dissolving the polymers of the first and second organic materials, and the step of causing the monomer to undergo photopolymerization in a region that will become an optical waveguide. A method for manufacturing an optical waveguide, comprising the step of removing residual monomer of the second organic material that has not undergone photopolymerization using a solvent (5) that dissolves the monomer. 2) forming a film of a waveguide material (3) comprising at least a monomer of a second organic material in a polymer of a first organic material on the substrate (1), and forming an optical waveguide with respect to the monomer; A method for manufacturing an optical waveguide comprising a step of causing photopolymerization in a region where the solvent is at least a solvent that does not dissolve the polymers of the first and second organic materials and dissolves the monomer of the second organic material. Alternatively, using a solvent (5) that does not dissolve the highly polymerized polymers of the first and second organic materials but dissolves the low polymerized polymers of the second organic material, 2. A method for manufacturing an optical waveguide, comprising the step of removing residual monomer of an organic material.