JPH1048443A - Polymer waveguide and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a waveguide which has a low loss, a flat upper surface of a clad layer, high dimensional accuracy and a small thickness of a substrate, and can be produced in a simple processes, by forming a core layer which is not to be irradiated with UV rays and forming upper and lower clad layers to be irradiated with UV rays on a buffer layer on a substrate. SOLUTION: The waveguide consists of a buffer layer 32 on a substrate 31, a polymer core layer 33 having an almost rectangular cross section on the buffer layer, a lower clad layer 34 formed on both sides of the core layer 33, and an upper clad layer 35 which covers the upper faces of the core layer 33 and the clad layer 34. The core layer 33 and lower clad layer 34 consist of a polymer material which decreases the refractive index by irradiation of UV rays. The core layer 33 is not irradiated with UV rays. The lower clad layer 34 consists of a polymer material which has been irradiated with UV rays and photoleached. Since the refractive index of the exposed part to LJV rays decreases, the exposed part to UV rays can be used as the clad layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polymer waveguide and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, research and development of polymer waveguides have become active. This is because it is considered to be promising for realizing a low-cost optical device.

FIG. 10 is a sectional view showing a conventional example of a polymer waveguide.

[0004] The polymer waveguide shown in FIG.
A cladding layer 1 made of a polymer material on
1-1 and 11-2 are formed, and the cladding layers 11-1 and 11-2 are formed.
11-2 has a structure in which a core layer 12 made of a polymer material having a higher refractive index than the cladding layers 11-1 and 11-2 is embedded.

The core layer 12 and the cladding layers 11-1 and 11
As the polymer material of -2, PMMA (polymethyl methacrylate), polystyrene, polyimide, polyguide, epoxy resin, polysiloxane, or the like is used.

FIGS. 11A to 11C show a conventional example showing a method for manufacturing a polymer waveguide. On the substrate 10, a photosensitive polymer layer 15 whose refractive index is increased by irradiation with ultraviolet rays
Is formed, a mask 16 is arranged on the polymer layer 15, and ultraviolet rays 17 are irradiated from above the mask 16 (FIG. 11A).

The exposed portion 15a of the polymer layer 15 irradiated with the ultraviolet light 17 transmitted through the mask 16 has a high refractive index, and the unexposed portion 1 not irradiated with the ultraviolet light by the mask 16 is exposed.
5b remains low without change in refractive index (FIG. 11).
(B)).

[0008] Such an unexposed portion 15b is formed by a light waveguide layer,
That is, the polymer waveguide is formed by using the core layer 12 and covering the core layer 12 with the clad layer 11 (FIG. 11C).

FIGS. 12A to 12D show another conventional example showing a method of manufacturing a polymer waveguide.

A core polymer waveguide layer 19 through which light propagates is formed on a substrate 10, and a mask 16 is placed thereon to irradiate ultraviolet rays 17 (FIG. 12A).

The exposed portion 19a irradiated with the ultraviolet light 17 transmitted through the mask 16 is removed by etching, and the unexposed portion 19b not irradiated with the ultraviolet light 17 by the mask 16 remains as the core layer 12 having a substantially rectangular cross-sectional shape (FIG. 12
(B), (c)).

The core layer 12 having a substantially rectangular cross-sectional shape is
By covering with a cladding layer 11 made of a polymer having a refractive index lower than the refractive index of 2, a polymer waveguide is formed (FIG. 12D).

FIGS. 13A to 13D show still another conventional example showing a method of manufacturing a polymer waveguide.

A core polymer waveguide layer 19 through which light propagates is formed on the substrate 10, and a mask pattern 20 is formed on the core polymer waveguide layer 19. As the material of the mask pattern 20, a resist material, an oxide film material or a metal material is used. Next, ultraviolet rays 17 are irradiated from above the mask pattern 20 (FIG. 13A).

The portion of the core polymer waveguide layer 19 where the mask pattern 20 is not formed is irradiated with ultraviolet light 17, and the portion where the mask pattern 20 is formed is irradiated with ultraviolet light 17.
Is not irradiated. Ultraviolet rays 17 of the core polymer waveguide layer 19
The exposed portion irradiated with is removed by etching (FIG. 1).
2 (b)).

Unexposed portion 19b of core polymer waveguide layer 19
The mask pattern 20 remaining on the core layer 12 is peeled off, and the surfaces of the core layer 12 and the substrate 10 are covered with a cladding layer 11 made of a polymer having a refractive index lower than that of the core layer 12 to form a polymer waveguide ( FIG. 12 (c)).

[0017]

However, FIG.
(A) to FIG. 11 (c), FIG. 12 (a) to FIG.
The polymer waveguide formed by the conventional method shown in FIGS. 13A to 13D has the following problems.

(1) Interfaces 14-1, 14-2, 14-1 and 14-2 between the core layer 12 and the cladding layers 11-1 and 11-2 shown in FIG.
14-3 became non-uniform, and the resulting light scattering loss could not be ignored. Such interface irregularities are:
The core layer 12 is etched or the cladding layers 11-1,
This was inevitable when coating with 11-2.

(2) Further, as shown in FIG. 10, there is a problem that the flatness of the upper surface of the cladding layer 11-2 is poor. In particular, as shown in FIGS. 12 and 13, the core layer 1 has a substantially rectangular cross-sectional shape.
It has been found that it is difficult to flatten the upper surface of the cladding layer 11-2 as long as the method of covering the upper surface with the cladding layer 11 is used after forming No. 2.

As shown in FIG. 14, when the flatness is poor, it is difficult to provide the thin film heater 21 on the cladding layer 11-2. This is because the thin film heater 21 first forms a metal film on the polymer cladding layer 11-2 by vapor deposition, then forms a resist pattern on the metal film, and performs etching by using the resist pattern as a mask. Although formed, the cladding layer 1
If the top surface of 1-2 is not flat, it is difficult to deposit a metal film, it is difficult to apply a resist film to a uniform thickness, and it is difficult to process a fine pattern of the thin film heater 21 by etching. That's why. FIG.
(A) is a plan view when a thin film heater is provided on a conventional polymer waveguide, and (b) is a cross-sectional view taken along the line AA of (a). 22 is a power supply, 23 is a switch, 2
Reference numerals 4 to 26 denote signal lights.

(3) Since the number of manufacturing steps is large, it is difficult to reduce the cost of the polymer waveguide.

(4) A high-performance single-mode transmission polymer waveguide type optical component requiring high dimensional accuracy cannot be realized. For example, optical components such as an optical demultiplexer for N-channel wavelength division multiplexing transmission and a 1 × M (or N × M) optical star coupler can be manufactured with high performance (low loss, control of center wavelength, high isolation characteristics, Distribution deviation characteristics, etc.).

(5) The thickness of the substrate 10 is made extremely thin (1.
It is difficult to form a so-called flexible polymer waveguide type optical component with high performance and high dimensional accuracy. This is because there is a processing process such as etching, and it is difficult to process a thin substrate while maintaining high dimensional accuracy.

Therefore, an object of the present invention is to solve the above-mentioned problems, to achieve low loss, a flat upper surface of the cladding layer, high dimensional accuracy,
An object of the present invention is to provide a polymer waveguide having an extremely thin substrate and a simple process, and a method for manufacturing the same.

[0025]

Means for Solving the Problems] polymer waveguide of the present invention in order to achieve the above object, a substrate, a buffer layer of low refractive index n _b, which is formed on the substrate, is formed on the buffer layer A core layer (refractive index n _w , n _w > n _b ) made of a polymer whose refractive index decreases when irradiated with ultraviolet light, and which is not irradiated with ultraviolet light, and ultraviolet light is irradiated on both sides of the core layer Lower cladding layer (refractive index n _p , n _p <
and n _w), those having a lower clad layer ultraviolet is irradiated on both sides of the polymer of the core layer, an upper cladding layer covering the upper surface of the lower clad layer and the core layer and _{(n c, n c <n} w) It is.

The present invention is directed to a core layer (refractive index n) having a substantially rectangular cross-section formed of a substrate and a polymer formed on the substrate and having a refractive index which decreases when irradiated with ultraviolet rays.
_w , n _w > n _b ), the lower cladding layer (refractive index n _p , n _p <n _w ) irradiated with ultraviolet light on both sides of the core layer, and the lower part irradiated with ultraviolet light on both sides of the polymer core layer. a clad layer, in which an upper cladding layer covering the upper surface of the lower clad layer and the core layer _{(n c, n c <n} w).

In addition to the above configuration, the polymer waveguide of the present invention
Either a SiO ₂ material or a polymer material may be used for the buffer layer and the upper cladding layer.

In addition to the above configuration, the polymer waveguide of the present invention
The refractive index of the core layer and the lower cladding layer is n _i (n _i <n
_{In w} ), it may be divided vertically by an intermediate layer having a desired thickness.

In addition to the above configuration, the polymer waveguide of the present invention
A plastic material may be used for the substrate.

The method of manufacturing a polymer waveguide according to the present invention includes a first step of sequentially forming a buffer layer, a polymer layer whose refractive index decreases when irradiated with ultraviolet rays, and an upper clad layer on a substrate; Arrange a photomask with a pattern of UV non-transmitting part and UV transmitting part on the upper surface,
A second step of forming a core layer made of a polymer not irradiated with ultraviolet rays and a lower clad layer made of a polymer irradiated with ultraviolet rays by irradiating ultraviolet rays from above the photomask, and upper surfaces of the core layer and the lower clad layer And a third step of forming an upper cladding layer.

In addition to the above structure, in the method of manufacturing a polymer waveguide according to the present invention, in the first step, another polymer layer and an intermediate layer are sequentially formed between the polymer layer and the upper clad layer, and the second step is performed. In the above, a core layer and another core layer made of a polymer not irradiated with ultraviolet rays and a lower clad layer and another clad layer made of a polymer irradiated with ultraviolet rays may be formed.

According to the present invention, a polymer core layer whose refractive index is reduced when irradiated with ultraviolet rays is used, and the polymer core layer is irradiated with ultraviolet rays except for a part to be a core layer, whereby the ultraviolet light exposed portion is exposed. Since the refractive index is lowered, the UV-exposed portion can be used as a cladding layer. For this reason, even if the upper part of the polymer core layer is covered with the upper clad layer, flatness can be ensured, and non-uniformity of the interface between the core layer and the upper clad layer can be eliminated and low loss can be obtained. Further, since the surface of the upper clad layer is flat, mounting of the thin-film metal heater becomes easy. In addition, a high-performance polymer waveguide can be realized at low cost because of the simple process of irradiating ultraviolet rays. Furthermore, since the thickness of the substrate can be made extremely thin, a flexible polymer waveguide can be formed.

[0033]

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

FIG. 1 is a sectional view showing one embodiment of the polymer waveguide of the present invention.

The polymer waveguide 30 shown in FIG.
(A semiconductor material such as Si, a glass material, a plastic material, a magnetic material, or the like is used).
A buffer layer (refractive index n _b) 32 consisting of _2, a core layer comprising a polymer of a rectangular cross-sectional shape substantially formed on the buffer layer 32 (refractive index _{n w, n w> n b} ) and 33, the core layer 33
Lower cladding layers (refractive indices n _p , n
_p <n _w ) 34, core layer 33 and lower cladding layer 34
An upper cladding layer covering the top surface _{(n c, n c <n} w) 35
It is composed of

The core layer 33 and the lower cladding layer 34 are made of a polymer material (polymer core layer) whose refractive index decreases when irradiated with ultraviolet rays. Among them, the core layer 33 is made of a polymer material not irradiated with ultraviolet rays. Lower cladding layer 3
4 is made of a so-called photobleached polymer material irradiated with ultraviolet rays.

Here, as the polymer material, for example, DMA
PN @ α- (4-dimethlaminophenyl) -N-phenylni
tron｝ is used. This is represented by the chemical formula (1).

[0038]

Embedded image

The photochemical rearrangement of this polymer material has a wavelength of 3
Photobleached at 80nm, wavelength 270nm
New absorption of the oxazilidene photoproduct takes place. Photobleaching by irradiation with ultraviolet light having a wavelength of 380 nm is almost completed with a total exposure of 100 mJ / cm ² (see FIGS. 2 and 3; references; new development of photopolymer technology, Toray Research). FIG. 2 is a diagram showing the absorption spectrum of DMAPN, where the horizontal axis is the wavelength and the vertical axis is the optical density. FIG. 3 is a diagram showing the wavelength dependence of the refractive index before and after photobleaching. The horizontal axis represents the wavelength, and the vertical axis represents the refractive index.

The core layer 33 of the polymer waveguide 30 shown in FIG.
In addition, since the thickness of the photo-bleached lower cladding layer 34 is in the range of several μm to several tens μm, the above exposure is sufficient. The unexposed core layer 33 has a wavelength of 815 nm and has a wavelength of 1.553, and the photobleached lower cladding layer has a refractive index of 1.537 at a wavelength of 815 nm. The relative refractive index difference delta ₁ between the core layer 33 and the lower cladding layer 34 is about 1.28%. The buffer layer 32 and the upper cladding layer 35 are made of SiO ₂ . The core layer 33 and the upper cladding layer 35 (a buffer layer 32) relative refractive index difference delta ₂ between the neighboring about 5.2%, the light is transmitted sufficiently confined in the core layer 33. The core layer 33 includes, in addition to DMAPN described above, dyepolymer, 4-alkoxy-4'-
alkylsulfone stilbene PMMA side −chain, 4-dialky
lamino-4'-nitro-stilbene or the like can be used.

The polymer waveguide shown in FIG. 1 is a waveguide for multimode transmission in which the relative refractive index differences Δ ₁ and Δ ₂ are 1% or more, but another embodiment will be described. The same reference numerals are used for members similar to those in the embodiment shown in FIG.

FIG. 4 is a sectional view showing another embodiment of the polymer waveguide of the present invention.

The polymer waveguide 40 shown in the figure is a polymer waveguide for single mode transmission, and a poly-furfuryl methacrylate is provided on the buffer layer 41 and the upper cladding layer 42.
(PFFMA, refractive index about 1.536). By setting the relative refractive index differences Δ ₁ and Δ ₂ to around 1.3%, a single mode transmission waveguide is obtained.
The buffer layer 41 and the upper cladding layer 42 may have various polymer materials other than the above-mentioned polymer materials, for example,
Lycore bisallyl caronate (refractive index 1.517) or the like can be used.

FIG. 5 is a sectional view showing another embodiment of the polymer waveguide of the present invention.

The polymer waveguide 50 shown in FIG.
Using a plastic film of polycarbonate, polyimide, epoxy, polystyrene or the like. The thickness of this film is about 100 μm to several hundreds of μm, and by using such a thin film, the polymer waveguide 50 itself has flexibility. By using this plastic film-shaped substrate 51, elasticity can be provided as compared with a glass, semiconductor, or magnetic substrate. Further, the core layer 33 does not break even with a certain degree of bending. further,
Since it is lightweight, the weight of the device when mounted in the device can be reduced. Also, significant cost reduction can be expected. Note that, in the polymer waveguide shown in the figure, when the refractive index of the substrate 51 made of plastic is lower than the refractive index of the core layer 33, the buffer layer 32 may not be provided.

FIG. 6 is a sectional view showing another embodiment of the polymer waveguide of the present invention.

The polymer waveguide 60 shown in the figure is a waveguide having a structure in which core layers 61 and 62 for transmitting light are stacked on a buffer layer 32 via an intermediate layer 63 having a low refractive index. The optical waveguide structure is effective for realizing an optical circuit such as a directional coupler or an optical filter using light coupling between the core layers 61 and 62. The refractive index n _i of the intermediate layer 63 is lower than the refractive index n _w of the core layer 61 (62), the refractive index n _c of the upper cladding layer 35, and the refractive index n of the photo-bleached lower cladding layers 64 and 65. _p, is selected to the same extent value and the refractive index n _b of the buffer layer 32. In this embodiment, the number of core layers 61 and 62 is two. However, an intermediate layer may be further provided and a large number of core layers may be laminated.

FIG. 7A is a side view showing an embodiment of an optical branch circuit using the polymer waveguide according to the present invention, and FIG. 7B is a sectional view taken along line BB of FIG. That is, a pattern diagram of the core layer).

The optical branching circuit 70 shown in FIG.
Into the core layer 72, and the core layer 73 and the core layer 74
To the incident light 71 as indicated by arrows 75 and 76.
Is an optical branching circuit for equal distribution, but in order to realize this equal distribution with low excess loss, δ and L of the branching portion must be precisely formed.

In particular, the value of δ is preferably about 1 μm, but it was extremely difficult to realize the value of δ by the conventional manufacturing method. However, according to the photobleaching of the present invention, An optical circuit pattern requiring a fine dimension of about 1 μm can be realized. For example, an optical directional coupling circuit or an optical circuit in which two core layers are arranged in parallel at an interval of 1 to 2 μm by a desired length to split light into two equal parts, or to split optical signals having different wavelengths. It is suitable for realizing an optical grating circuit or an optical filter circuit that alternately provides core layers having different refractive indexes in the propagation direction and reflects or transmits only an optical signal of a desired wavelength.

FIG. 8 is a process chart showing one embodiment of a method for manufacturing a polymer waveguide according to the present invention.

First, a buffer layer 32 is formed on a substrate 31 as shown in FIG. The buffer layer 23 is made of SiO
₂ or SiO ₂ containing at least one kind of additive for controlling the refractive index such as B, F, P, Ti, Ge, and Al, the buffer layer 32 may be formed by a CVD method or a plasma CVD method.
It is formed by a sputtering method, a sputtering method, an electron beam evaporation method, a spin coating method, or the like. When the buffer layer 32 is made of a polymer, it is formed by a spin coating method, a vacuum evaporation method, or the like. A photobleaching polymer core layer 34a is formed on the buffer layer 32. The photobleaching polymer core layer 34a is formed by a spin coating method, a vacuum evaporation method, or the like. In the polymer spin coating method, a polymer solution dissolved in a solvent is applied by a spin coating method, followed by drying and curing after pre-baking and post-baking.

Next, as shown in FIG. 2B, the upper cladding layer 3 is formed on the polymer core layer 34a for photobleaching.
5 is formed. This upper cladding layer 35 is
2 and is formed by the same method.

As shown in FIG. 3C, the upper cladding layer 3
5, a photomask 36 is arranged, and ultraviolet rays 37 are irradiated from above the photomask 36. When the photobleaching polymer layer 34a is, for example, the DMAPN described above, the ultraviolet light 37 is irradiated with light having a wavelength of 380 nm. The irradiation amount of the ultraviolet rays is set to 100 mJ / cm ² . When the ultraviolet ray 37 is irradiated, the refractive index of the portion corresponding to the ultraviolet ray transmitting portion 36b other than the ultraviolet ray non-transmitting portion 36a is reduced by photobleaching (refractive index 1.537), and FIG.
Lower cladding layer 3 photo-bleached as shown in FIG.
It becomes 4. The portion not irradiated with the ultraviolet rays 37 becomes the core layer 33, and the polymer waveguide shown in FIG. 1 is formed (refractive index: 1.553).

As described above, since the polymer waveguide can be realized by forming the film and irradiating the ultraviolet rays, the interface 14-1, 14 of the polymer core layer 14, which has been a problem in the conventional polymer waveguide, has been problematic. No roughening of -2 and 14-3 occurs (see FIG. 10). Also, since the flatness can be maintained on the upper surface of the upper cladding layer 35, it is necessary to further form an optical waveguide, provide a thin film heater, or mount an optical component or an electronic component on the upper surface of the upper cladding layer 35. Becomes easier. Furthermore, since there is no conventional etching process, the manufacturing method is simple and the manufacturing can be performed at low cost.

FIG. 9 is a process chart showing another embodiment of the method for manufacturing a polymer waveguide according to the present invention.

First, as shown in FIG. 1A, a buffer layer 32 and a photobleaching polymer layer 64 are formed on a substrate 31.
a, an intermediate layer 63, a bleaching polymer layer 65a, and an upper cladding layer 35 are sequentially deposited. Buffer layer 3
2. The photobleaching polymer layers 64a and 65a and the upper cladding layer 35 are formed by the same method as in the manufacturing method shown in FIG. When the material of the intermediate layer 63 is SiO ₂ or SiO ₂ containing at least one kind of a refractive index controlling additive such as B, F, P, Ti, Ge, or Al,
A CVD method, a plasma CVD method, and an electron beam evaporation method are used. When the material is a material such as a spin-on-glass solution or a material such as a polymer solution dissolved in a solvent, it is formed by spin coating, pre-baking, or post-baking.

Next, as shown in FIG. 6B, a photomask 66 is disposed on the upper cladding layer 35, and the upper surface of the photomask 66 is irradiated with ultraviolet rays 67. UV rays 6
7 denotes an upper clad layer 3 which transmits through the ultraviolet transmitting portion 67a.
5. Photobleaching polymer layer 65a, intermediate layer 6
3. The photobleaching polymer layer 64a, the buffer layer 32 and the substrate 31 are reached. When the photobleaching polymer layers 64a and 65a are photobleached, the refractive index of the polymer layers is reduced, and the photobleached lower cladding layers 64 and 65 are formed.

On the other hand, the photobleaching polymer layers 64a, 6b under the ultraviolet non-transmissive portion 66b of the photomask 66.
The portion 5a is the unexposed portion, and becomes the core layers 61 and 62 without lowering the refractive index. The shapes of the core layers 61 and 62 are as follows:
When the total thickness of each of the lower cladding layers 64 and 65, the photobleaching polymer layers 64a and 65a, and the intermediate layer 63 is 30 μm or less, the dimensions are substantially the same. When the sum of the thicknesses of the respective layers is 35 μm or more, the shapes of the core layers 61 and 62 are slightly different. When the photobleaching polymer layers 64a and 65a are thick, that is, for multi-mode transmission, the photomask 66 is formed on the photobleaching polymer layer 65a before the upper cladding layer 35 is formed. Are arranged and photo-bleaching is performed, and then the upper clad layer 35 is formed, so that the core layers 61 and 62 can be formed with higher accuracy and the photo-bleached lower clad layers 64 and 65 can be formed. A polymer waveguide 60 having a uniform refractive index is obtained.

Incidentally, in the case where the method of manufacturing the polymer waveguide shown in FIG. 8 is used, photobleaching may be performed in the same manner.

As described above, according to the present invention, (1) the non-uniformity of the interface between the polymer core layer and the clad layer is almost eliminated, and a low-loss optical waveguide can be realized.

(2) Since the upper surface of the upper cladding layer is flat,
It becomes easy to form a thin film metal heater and a thin film magnetic material. Also, mounting of optical components and electronic components becomes easy.

(3) Since a core pattern layer having a simple process and high dimensional accuracy can be formed, a high-performance waveguide-type optical component can be realized at low cost.

(4) A so-called flexible polymer waveguide type optical component having an extremely thin substrate can be manufactured with high performance and high dimensional accuracy. Moreover, it is not bent and broken, and is easily mounted in the device.

[0065]

In summary, according to the present invention, the following excellent effects are exhibited.

The cladding layers are formed on both sides of the core layer by irradiating the ultraviolet rays except for the portion of the polymer core layer which is to be the core layer, the refractive index of which decreases when irradiated with the ultraviolet rays. The upper surface becomes flat, and a very thin polymer waveguide with high dimensional accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a polymer waveguide according to the present invention.

FIG. 2 is a diagram showing an absorption spectrum of DMAPN.

FIG. 3 is a diagram showing the wavelength dependence of the refractive index before and after photobleaching.

FIG. 4 is a sectional view showing another embodiment of the polymer waveguide of the present invention.

FIG. 5 is a sectional view showing another embodiment of the polymer waveguide of the present invention.

FIG. 6 is a cross-sectional view showing another embodiment of the polymer waveguide of the present invention.

7A is a side view showing an embodiment of an optical branch circuit using the polymer waveguide of the present invention, and FIG. 7B is a cross-sectional view taken along the line BB of FIG.

FIG. 8 is a process chart showing one embodiment of a method for manufacturing a polymer waveguide of the present invention.

FIG. 9 is a process chart showing another embodiment of the method for producing a polymer waveguide of the present invention.

FIG. 10 is a cross-sectional view showing a conventional example of a polymer waveguide.

FIGS. 11A to 11C are conventional examples showing a method for manufacturing a polymer waveguide.

FIGS. 12A to 12D are other conventional examples showing a method for manufacturing a polymer waveguide.

FIGS. 13A to 13D show still another conventional example illustrating a method for manufacturing a polymer waveguide.

FIG. 14A is a plan view showing a case where a thin film heater is provided on a conventional polymer waveguide, and FIG. 14B is a plan view of AA in FIG.
It is a line sectional view.

[Explanation of symbols]

 Reference Signs List 30 polymer waveguide 31 substrate 32 buffer layer 33 core layer 34 lower clad layer 34a polymer core layer 35 upper clad layer

Claims (7)

[Claims] 1. A substrate, a buffer layer having a low refractive index n _b formed on the substrate, and a polymer formed on the buffer layer and having a refractive index which is reduced when irradiated with ultraviolet rays. A core layer having a substantially rectangular cross-sectional shape that is not irradiated (refractive index n
_w , n _w > n _b ), the lower cladding layer (refractive index n _p , n _p <n _w ) irradiated with ultraviolet light on both sides of the core layer, and ultraviolet light irradiation on both sides of the core layer of the polymer. It is a lower cladding layer, a polymer waveguide, characterized in that it comprises an upper cladding layer covering the upper surface of the lower cladding layer and the core layer and _{(n c, n c <n} w). 2. A core layer (refractive index n _w , n _w ) comprising a substrate and a polymer formed on the substrate and having a refractive index which decreases when irradiated with ultraviolet rays, and which is not irradiated with ultraviolet rays.
_w > n _b ), a lower cladding layer (refractive index n _p , n _p <n _w ) irradiated with ultraviolet light on both sides of the core layer, and a lower part irradiated with ultraviolet light on both sides of the core layer of the polymer. polymer waveguide and a cladding layer, characterized in that an upper cladding layer covering the upper surface of the lower cladding layer and the core layer _{(n c, n c <n} w). 3. The polymer waveguide according to claim 1, wherein the buffer layer and the upper cladding layer are made of one of a SiO ₂ material and a polymer material. 4. The method according to claim 1, wherein the core layer and the lower clad layer are
4. The polymer waveguide according to claim 1, wherein the polymer waveguide is vertically divided by an intermediate layer having a refractive index of _ni ( _ni < _nw ) and a desired thickness. 5. The polymer waveguide according to claim 1, wherein a plastic material is used for the substrate. 6. A first step of sequentially forming a buffer layer, a polymer layer whose refractive index decreases when irradiated with ultraviolet light and an upper clad layer on a substrate, and an ultraviolet non-transmissive portion and ultraviolet light on the upper surface of the upper clad layer. By arranging a photomask on which a pattern of the transmission portion is formed, and irradiating ultraviolet rays from above the photomask, a core layer made of a polymer not irradiated with ultraviolet rays and a lower clad layer made of a polymer irradiated with ultraviolet rays are formed. A method for manufacturing a polymer waveguide, comprising: a second step of forming; and a third step of forming an upper clad layer on the upper surfaces of the core layer and the lower clad layer. 7. In the first step, another polymer layer and an intermediate layer are sequentially formed between the polymer layer and the upper clad layer, and in the second step, a core layer made of a polymer which is not irradiated with ultraviolet rays. 7. The method of manufacturing a polymer waveguide according to claim 6, wherein another core layer, a lower cladding layer made of a polymer irradiated with ultraviolet rays, and another cladding layer are formed.