JPH01134310A - Production of light guide - Google Patents

Abstract

PURPOSE:To extremely easily produce a light guide having a desired refractive index distribution by subjecting a waveguide material consisting of an org. material to photopolymn. by exposing and by adequately changing the exposure. CONSTITUTION:The waveguide material 12 is formed on a substrate 11 by using an org. material such as polymethyl methacrylate (PMMA). A photomask 13 having a desired waveguide pattern is disposed thereon and the photopolymn. is executed by executing exposing with UV rays, etc. The exposure is adequately changed in accordance with the relation between the exposure and the difference in refractive index at this time. As a result, the light guide having an arbitrary difference in refractive index and an arbitrary shape is thereby extremely simply and easily formed without requiring intricate production processes such as vacuum process and etching at all.

Description

[Detailed Description of the Invention] [Summary] Manufacture of an optical waveguide suitable for obtaining an optical waveguide in which the shape of the guided mode changes, such as a mode matching element connected between a semiconductor laser and an optical fiber. Regarding the method, the aim is to realize an optical waveguide of any shape with an arbitrary refractive index difference by a simple manufacturing process, using an organic material as the waveguide material and creating a desired refractive index distribution by photopolymerizing the waveguide material. A method of manufacturing an optical waveguide for forming an optical waveguide, wherein the photopolymerization is caused by exposure, and the amount of exposure is appropriately changed based on the relationship between the amount of exposure and the refractive index difference. It is configured to obtain a desired refractive index distribution.

[Industrial application field]

The present invention relates to a method of manufacturing an optical waveguide suitable for obtaining an optical waveguide in which the shape of a waveguide mode changes, such as a mode matching element connected between a semiconductor laser and an optical fiber.

[Conventional technology]

Generally, at a connection point between a semiconductor laser and an optical fiber (or an optical functional element), the shapes of the optical waveguides (waveguide modes) are different from each other, resulting in a very large loss. For example, the waveguide mode of a semiconductor laser is elliptical, whereas the waveguide mode of an optical fiber is circular.

Conventionally, in order to reduce the above-mentioned losses, there are devices in which various lenses are incorporated into the connection points, as shown in FIG. That is, in the same figure (al shows the cylindrical lens 3 and the focusing rod lens 4 assembled between the semiconductor laser 1 and the optical fiber 2, and in the same figure (bl shows the optical fiber 2 with the tip 2 assembled).
A is an optical fiber using a tapered spherical fiber (or a reduced diameter spherical fiber), and (0) is an optical fiber 2 with a microlens 2b formed at its tip. This is what I used. With such a configuration, the coupling loss is improved to about 2 to 3 dB.

Furthermore, an attempt has been made to establish a low-loss connection by arranging a mode matching element 5 as shown in FIG. 5 between the semiconductor laser and the optical fiber. This mode matching element 5 is an optical waveguide whose refractive index distribution (refractive index difference) and cross-sectional shape gradually change along the traveling direction of light by thermally diffusing the total refraction of Ag etc. to the glass substrate 5a. 5b is formed. By using the mode matching element 5 with such a configuration, it is possible to prevent the loss due to reflection at the boundary between the lens and the air, which always occurred in the one shown in Fig. 4, making it possible to further reduce the loss. Become.

[Problem that the invention seeks to solve]

Optical waveguide 5b in mode matching element 5 shown in FIG.
is formed by thermal diffusion to the glass substrate 5a as described above. Therefore, the manufacturing process is extremely complicated, and the degree of freedom in the shape (dimensions) and refractive index difference of the waveguide is small.In other words, it is extremely difficult to freely select the desired shape and desired refractive index difference. Met.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a method for manufacturing an optical waveguide that can realize an optical waveguide having an arbitrary shape and an arbitrary refractive index difference through a simple manufacturing process.

[Means for solving problems]

In the present invention, an organic material is used as a waveguide material, and an optical waveguide is formed by photopolymerizing it to give it a desired refractive index distribution. Further, the photopolymerization is caused by exposure, and the amount of exposure is appropriately changed based on the "relationship between the amount of exposure and the difference in refractive index" to obtain the desired refractive index distribution.

[For production]

When the above organic material undergoes photopolymerization due to exposure to light, the refractive index of that portion changes. Therefore, if a desired region is exposed to light using, for example, a light beam or a photomask to cause photopolymerization, a difference in refractive index will occur between that region and other regions, and an optical waveguide will therefore be obtained. That is, the shape pattern of the optical waveguide can be selected very freely depending on the exposure area.

In addition, since the degree of photopolymerization varies depending on the amount of exposure,
The refractive index is also different. That is, a certain relationship exists between the exposure amount and the refractive index (refractive index difference). Therefore, by appropriately changing the exposure amount, the refractive index can be extremely freely selected according to the exposure amount based on the above relationship.

From the above, it is possible to easily obtain an optical waveguide of any shape with any refractive index difference without any need for complicated manufacturing processes such as vacuum processing or etching as well as thermal diffusion.

〔Example〕

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

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

Here, a case will be described in which an optical waveguide in a mode matching element used for optical coupling between a semiconductor laser and an optical fiber is manufactured.

Generally, in a single mode optical waveguide, if you are trying to confine light in a thin waveguide, you need a larger refractive index difference, and if you are trying to confine light in a thick waveguide, you need a smaller refractive index difference. Requires difference. From this,
On the side facing the semiconductor laser 1 having a horizontally elongated waveguide mode shape as shown in FIG. 2(al), the horizontal width W2 of the optical waveguide 15 is made longer than the vertical width W1, as shown in FIG. In addition, the refractive index difference in the lateral direction Δn+2 (=n+ n
2) is smaller (, vertical refractive index difference Δn+ 3 (=
n+-n3) needs to be made larger. On the other hand, on the side facing the optical fiber with a circular guided mode shape,
The vertical and horizontal widths W I SW 2 of the optical waveguide 15 are made equal to each other, and accordingly, the refractive index difference Δn12 in the horizontal and vertical directions is
, Δn13 must be equal to each other. In this example, an optical waveguide is manufactured so as to satisfy the conditions of such shape and refractive index difference.

First, as shown in FIG. 1(a), a substrate 11 with a refractive index of n3
A waveguide material 12 having a refractive index n20 is formed thereon to have a thickness Wl. As this waveguide material 12, for example, B
An organic material such as polymethyl methacrylate (PMMA) containing A-mer styrene (SL) is used. Then the first
As shown in Figure (b), a photomask 13 having a desired waveguide pattern in which the semiconductor laser side is wide and the optical fiber side is narrow is placed on the waveguide material 12, and then ultraviolet rays are emitted through the photomask 13. Exposure is performed. At this time, the exposure time is set based on the relationship described below.

That is, when the above-mentioned organic material (S t/PMMA) is exposed to light while keeping the light intensity constant, the difference between the exposure time (exposure M) t and the refractive index difference Δn is as shown in FIG. A certain relationship is obtained.

This relationship is represented by a nonlinear curve in which the amount of change in the refractive index difference Δn gradually decreases as the exposure time (exposure m>t) increases, and when the exposure time t exceeds a certain value, the refractive index difference Δn saturates. This kind of relationship exists in polymers (
The amount of monomer (St) contained in PMMA) is finite, and this finite monomer undergoes photopolymerization by the above exposure and changes into a polymer, and as a result, the refractive index changes. This is because the amount increases. When all the monomers become polymers, the refractive index difference Δn becomes saturated.

Therefore, based on the above relationship, the exposure time in FIG. 1(b) is set to tl. Exposure area 12a and non-exposure area 12b
A large refractive index difference Δn1=n21−n20 can be obtained between the two.

Next, as shown in FIG. 1 (dl), only a predetermined area on the semiconductor laser side is left and the other areas are covered with a photomask 14, and a second exposure is performed through this photomask 14. At this time, By providing a gap d between the photomask 14 and the substrate surface, light is allowed to pass around to the lower region of the photomask 14. Also, the exposure time in this case is set to t2 based on the relationship shown in FIG. Then, on the semiconductor laser side, as shown in FIG. 1 (el), the exposure time t,
A twice-exposed region 12c of +t2 and a once-exposed region 12d of exposure time t2 are generated, and there is a small refractive index difference Δ between them.
It is possible to obtain n2=n23-n22.

The optical waveguide 15 obtained through the above steps has a shape that is wide on the semiconductor laser side and narrow on the optical fiber side. Furthermore, regarding the refractive index distribution, there is a large refractive index difference Δn1 (-n2+-n2o
), with a small refractive index difference Δ on the wide semiconductor laser side.
It has n2 (=n23-n2;). Moreover, 2
During the second exposure, as shown in FIG. 1(d), the gap d was provided in the photomask 14 to allow the light to pass around, so the refractive index difference was smoothed in the general direction of light propagation. It's changing.

Therefore, according to this embodiment, the shape pattern of the optical waveguide can be freely written using a photomask, and the refractive index can be freely selected by exposure ff1 (iF8 light time), which is necessary for a mode matching element. An optical waveguide that satisfies the conditions of shape and refractive index difference can be obtained extremely easily.

Furthermore, the manufacturing process becomes extremely simple since not only thermal diffusion but also complicated treatments such as vacuum processing and etching are not required. Furthermore, since an organic material was used as the waveguide material, the mode matching element obtained in this example is very inexpensive and lightweight.

Note that the waveguide pattern may be drawn by scanning a light beam instead of using a photomask as in the above embodiment. Further, the exposure amount may be adjusted by changing the light intensity instead of by changing the exposure time.

Furthermore, as the waveguide material, in addition to the above-mentioned St/PMMA, it is possible to use various organic materials that have a certain relationship between the exposure amount and the refractive index difference, as shown in Figure 3. can.

Furthermore, the present invention is not only applicable to the production of a mode matching element between a semiconductor laser and an optical fiber (or between optical functional elements) as described above, but also can be applied to various types of devices in which the waveguide mode shape changes. It is ideal for fabricating optical waveguides.

〔Effect of the invention〕

As explained above, according to the present invention, an optical waveguide having an arbitrary shape (size) having an arbitrary refractive index difference can be freely produced. That is, the degree of freedom in the shape of the optical waveguide and the difference in refractive index is very large. Therefore, it is possible to extremely easily obtain an optical waveguide such as a mode matching element in which the waveguide mode shape changes. Moreover, since no complicated process such as thermal diffusion is required, the manufacturing process is extremely simple. Furthermore, since an organic material is used as the waveguide material, the optical waveguide produced in the present invention is lightweight and inexpensive.

[Brief explanation of the drawing]

Figures 1 (a) to (e) are manufacturing process diagrams showing one embodiment of the present invention, Figure 2 (al and (bl) are diagrams showing waveguide mode shapes of general semiconductor lasers and cross-sections of optical waveguides. Figure 3 is a diagram showing the conditions of shape and refractive index difference. Figure 3 is a diagram showing the relationship between exposure time (exposure fl) t and refractive index difference Δn in an organic material used in an embodiment of the present invention. Figure 4 fa) to (C) are diagrams showing a conventional connection structure between a semiconductor laser and an optical fiber, and FIG. 5 is a perspective view showing a conventional mode matching element. 12...Waveguide material, 13.14...・Photomask, 15... Optical waveguide. Patent applicant: Fujitsu Ltd. (b) (C) A look at "Removal of semiconductors from optical fibers" shown in Fig. 4 ( b) Watertight sun and moon (d) 11 units.

Claims (1)

[Claims] 1) An optical guide in which an organic material is used as a waveguide material (12) and the waveguide material (12) is given a desired refractive index distribution by photopolymerization to form an optical waveguide (15). A method for manufacturing a wave path, characterized in that the photopolymerization is caused by exposure, and the desired refractive index distribution is obtained by appropriately changing the amount of exposure based on the relationship between the amount of exposure and the difference in refractive index. A method for manufacturing an optical waveguide. 2) The method for manufacturing an optical waveguide according to claim 1, characterized in that the exposure is performed only on desired areas through a photomask (13, 14). 3) The method of manufacturing an optical waveguide according to claim 1, wherein the exposure is performed only on a desired area by scanning a light beam. 4) The optical waveguide according to any one of claims 1 to 3, wherein the exposure amount is adjusted by changing the exposure time while keeping the light intensity constant. Production method. 5) The optical waveguide (15) is formed so that its cross-sectional shape changes with respect to the propagation direction of light, according to any one of claims 1 to 4. A method for manufacturing an optical waveguide. 6) The optical waveguide (15) is formed such that the difference in refractive index with the surrounding area changes with respect to the propagation direction of light. The method for manufacturing an optical waveguide according to item 1. 7) The relationship between the exposure amount and the refractive index difference is expressed by a nonlinear curve in which the amount of change in the refractive index difference gradually decreases as the exposure amount increases, and the refractive index difference increases for an exposure amount equal to or higher than a predetermined value. The method for manufacturing an optical waveguide according to any one of claims 1 to 6, characterized in that the optical waveguide is saturated. 8) According to any one of claims 1 to 7, the optical waveguide is an optical waveguide in a mode matching element used for optical coupling between a semiconductor laser and an optical fiber. A method of manufacturing the optical waveguide described above. 9) Any one of claims 1 to 7, wherein the optical waveguide is an optical waveguide in a mode matching element used for optical coupling between optical functional elements.
The method for manufacturing an optical waveguide described in . 10) The organic material has a second organic material in the polymer of the first organic material.
The light guide according to any one of claims 1 to 9, characterized in that the light guide comprises a monomer of an organic material, and the monomer is converted into a polymer by the photopolymerization. Method of manufacturing wave channels. 11) The method for manufacturing an optical waveguide according to claim 10, wherein the first organic material is methyl methacrylate. 12) The method for manufacturing an optical waveguide according to claim 10 or 11, wherein the second organic material is styrene.