JP2001116942A - Manufacturing method of optical waveguide - Google Patents

Abstract

(57) [PROBLEMS] To prevent the generation of voids without complicating the manufacturing process of an optical waveguide, and to reduce the loss of signal light by removing the residual internal stress of each film formation layer. A possible method for manufacturing an optical waveguide is provided. SOLUTION: After forming a core layer directly or via a buffer layer on the surface of a substrate, patterning the core layer into a desired core shape, and forming a cladding layer thereon,
Heat / pressure treatment at a temperature and pressure higher than the film formation temperature of each layer is performed in a state where the clad layer is exposed on the surface, or a desired core shape is formed on the surface of the substrate or the surface of the buffer layer laminated thereon. After forming a concave portion to form a core and forming a core in the concave portion, a heating and pressing treatment at a temperature and pressure higher than the film forming temperature of the core is performed in a state where the core is exposed on the surface, and a cladding layer is formed on the upper portion thereof Is formed, the occurrence of thermal stress between the protective film and the cladding layer can be prevented, and the process can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical waveguide applied to a device for transmitting signal light in, for example, optical communication.

[0002]

2. Description of the Related Art Conventionally, as a planar lightwave circuit (PLC) used for optical communication or the like, an optical waveguide such as a so-called optical star coupler has been used as a branching device, for example. This optical waveguide is generally a buried waveguide structure having a step index type refractive index distribution.

Such an optical waveguide includes a buffer layer (or lower cladding layer), a core, and an upper cladding layer on a substrate made of quartz or silicon wafer or the like.

To manufacture an optical waveguide, first, a low refractive index buffer layer mainly composed of SiO ₂ and a high refractive index core layer are formed on the surface of a substrate by various film forming methods. After a predetermined waveguide pattern is formed on the surface of the substrate by a photoresist, RIE (Reactive Ion) is performed.
Etching), etc.,
A waveguide core having a predetermined pattern is formed. After that, the SiO
An upper cladding layer having a low refractive index and containing ₂ as a main component is formed. Finally, it is cut into a predetermined shape by a dicing device. Each optical waveguide is completed by polishing the light input / output end face.

When forming the core, the refractive index of the core is set to be 0.2% or less than the refractive index of the buffer layer and the upper cladding layer.
To increase the refractive index by about 0.8%, a dopant for increasing the refractive index is added at the time of film formation, or a dopant for lowering the refractive index is added when the buffer layer and the upper clad layer are formed.

[0006]

In the case of forming each of the above layers, after depositing a powder whose main component is SiO ₂ or the like,
There is an FHD method in which the powder is heated to a temperature of 1200 ° C. to 1500 ° C. to form the above-mentioned powder into a transparent glass state. However, the processing temperature is high, so that the dopant diffuses or SiO _{2 as} a main component of each layer. Is difficult to form the above-mentioned layers into a desired shape due to the flow of the glass composed of various chemical vapor deposition methods (CVD methods, for example, plasma CV, etc.).
D method), various physical vapor deposition methods (PVD method, for example, vacuum vapor deposition method), or a film forming method combining these methods (hereinafter, these vapor deposition methods are collectively referred to as a low-temperature film forming method). Proposed. If these low-temperature film forming methods are used, the above-described layers can be formed at a relatively low temperature of, for example, about 500 ° C. as compared with the FHD method. Also, the thickness control is relatively easy.

However, particularly in the case of an optical waveguide 31 such as an optical star coupler, as shown in FIG.
When a plurality of cores 34 are arranged close to each other with a buffer layer 33 interposed therebetween, if the upper cladding layer 34 is formed thereon, the glass is not sufficiently filled between the adjacent cores 34 and the gaps 38 ( Voids). If the voids 38 are provided, the core 34 is not completely buried, so that there is a problem that the loss of the signal light when the optical waveguide transmits the signal light increases. Further, although not shown, when a concave portion is formed in the substrate 32 and a core is formed in the concave portion, the glass constituting the core is not sufficiently filled in the concave portion, so that the signal light is further transmitted than the above. There is a problem that loss increases.

Further, the internal stress may remain in the layer formed by each of the above-mentioned vapor deposition methods, and the polarization dependent loss (PDL) may increase, which also increases the signal light loss.

[0009] Therefore, Japanese Patent Application No. Hei 9
-289813 (JP-A-11-125727)
No.), for example, a hot isostatic pressing method (HIP method: Hot
Isostatic Pressing)
It is described that pressure treatment is performed. By performing the heat / pressure treatment, the residual internal stress in the core and the upper clad layer can be removed and the void can be closed.

When the heating and pressurizing treatment by the HIP method is performed, a gas such as argon (Ar) used for this treatment enters the core and / or the upper cladding layer. Conventionally, a protective film is formed on the exposed surface before the heating / pressurizing treatment, and the protective film is removed after the treatment, since the amount of the film adversely affects the film composition depending on the amount.

However, the process of forming / removing the protective film has been one of the factors that complicates the production of the optical waveguide. In addition, due to the difference in the coefficient of thermal expansion between the protective film and the core and / or upper clad layer, the adverse effect due to the thermal stress generated when performing the above-mentioned heating / pressing process cannot be ignored.

Since the optical waveguide as described above requires relatively high precision in its processing, it is necessary to reduce the number of processes such as film formation, etching and polishing as much as possible and to simplify the structure. Needless to say, this is desirable. For example, Japanese Patent Application Laid-Open No. 61-210304 discloses a structure in which a substrate is used as a buffer layer (lower cladding layer) as a glass substrate. According to this structure, one film forming step can be omitted.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its main object to prevent generation of voids without complicating the manufacturing process of an optical waveguide. An object of the present invention is to provide a method of manufacturing an optical waveguide that can reduce the loss of signal light by removing the residual internal stress of each film formation layer.

[0014]

According to the present invention, there is provided a method for manufacturing an optical waveguide having a core covered by a cladding layer, wherein the core layer is directly formed on a surface of a glass substrate. An optical waveguide, comprising: forming a film, patterning it into a desired core shape, forming a cladding layer thereon, and then performing a heating / pressing process at a temperature and pressure higher than the film forming temperature of each layer. Manufacturing method of, or
After forming the core directly on the concave portion formed so as to form a desired core shape on the surface of the substrate made of glass, a heating and pressurizing treatment is performed at a temperature and pressure higher than the film forming temperature of the core. This is achieved by providing a method for manufacturing an optical waveguide, comprising forming a clad layer on the upper part. Not only can the process be simplified by using a glass substrate as the lower cladding layer, but also a high-precision lower cladding layer with a uniform density can be easily obtained, and by forming the core and upper cladding layer thereon, the overall , The loss of signal light can be reduced. In addition, by applying heat and pressure treatment after film formation, residual internal stress of each layer disappears, and even if a void is generated in the upper clad layer or core during film formation, it can be closed, further reducing the loss of signal light. Can be.

Another object of the present invention is to provide a method for manufacturing an optical waveguide having a core covered by a cladding layer, wherein the core layer is formed directly on the surface of the substrate or via a buffer layer, and the core layer is formed. After patterning into a desired core shape and forming a clad layer on the core, a heating / pressing process at a temperature and pressure higher than the film forming temperature of each layer is performed in a state where the clad layer is exposed on the surface. A method for producing an optical waveguide, or a method for producing an optical waveguide having a core covered by a cladding layer on a substrate surface portion, wherein the substrate surface portion or a buffer layer surface portion laminated on the substrate surface has a desired shape. A recess is formed so as to form a core shape of
After forming the core in the concave portion, performing a heating / pressing process at a temperature and pressure higher than the film forming temperature of the core in a state where the core is exposed on the surface, and forming a clad layer on the core. This is also achieved by providing a method for manufacturing an optical waveguide characterized by the following. By performing the heat and pressure treatment in a state where the upper clad layer or the core is exposed, generation of thermal stress due to the protective film can be prevented, and the process can be simplified. Here, in the case of the above-mentioned optical waveguide, for example, a hot isostatic pressing method (HIP method: Hot Isos) is used to remove residual internal stress of the core and the upper clad layer and to close the void.
Even if the heating / pressing treatment by static pressing is performed in a state where the upper clad layer or the core is exposed, there is no fear that argon (Ar) or the like penetrating the upper clad layer or the core adversely affects the durability and the like. .

[0016]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG.
FIG. 1 is a perspective view of an optical waveguide 1 according to a first embodiment of the present invention. This optical waveguide 1 has a buried waveguide structure,
The core 4 is formed in a pattern that branches the optical signal,
For example, it is used as a branching device in optical communication. For example, signal light is input from one end 6 (input end) of the core 4 located on the left front side in the drawing, and signal light is output from the other end 7 (output end) of the plurality of cores 4 located on the right rear side in the drawing. It has become.

FIG. 2 is a sectional view of the optical waveguide 1 taken along line II-II. A core 4 is formed on a substrate 2 made of glass such as quartz and also serving as a buffer layer (lower cladding layer), and an upper cladding layer 5 is formed so as to cover the core 4 and a portion of the substrate 2 where the core 4 is not provided. I have.

The cross section of the core 4 is, for example, a square having a side of about 8 μm. The core 4 is formed to have a slightly higher refractive index than the substrate 2 and the upper clad layer 5, so that signal light used for optical communication or the like passes through the inside. The upper clad layer 5 is formed on the substrate 2 and the core 4 to have a thickness of, for example, about 25 μm so as to cover the core 4 together with the substrate 2.

The procedure for manufacturing the optical waveguide 1 will be described below with reference to FIGS. 3 (a) to 3 (d). First,
On a surface of a glass substrate 2 made of quartz or the like, SiO 2 is deposited at a low temperature of, for example, about 500 ° C. by a CVD method as a low-temperature film forming method.
A core layer 4 'mainly composed of ₂ is formed (FIG. 3
(A)). At this time, 0.2% to
One or two selected from phosphorus (P), titanium (Ti), germanium (Ge), aluminum (Al), boron (B) and fluorine (F) such that the refractive index is increased by about 0.8%. At least one kind of dopant for adjusting the refractive index is added to the core layer 4 '. Phosphorus (P), titanium (Ti), germanium (Ge), and aluminum (Al) are dopants for increasing the refractive index, and boron (B) and fluorine (F) are dopants for decreasing the refractive index. Agent. A desired refractive index can be obtained by adding these alone or in combination.

In general, the refractive index of the core layer 4 'is preferably the same as the refractive index of the core of an optical fiber used for optical communication. In this configuration, only the core layer 4 ′ is doped and the substrate 2 and the upper clad layer 5 are not doped, but only by adjusting the refractive index of the core layer 4 ′, the refractive index between the glass substrate 2 and the upper clad layer 5 is reduced. If the refractive index cannot be made the same as the refractive index of the core of the optical fiber while maintaining the difference in the refractive index, a doping agent for lowering the refractive index is added at the time of manufacturing the glass substrate 2, and at the time of forming the upper clad layer 5, Alternatively, a dopant for lowering the refractive index may be added to adjust the respective refractive indexes.

As shown in FIG.
The apparatus holds a substrate 2 in a holder 23 in a reaction chamber 22 and supplies a reaction gas in a state where the substrate 2 is heated by a heater 24, for example, a general atmospheric pressure CVD for depositing a core layer 4 ′ on the surface of the substrate 2. The apparatus is not limited thereto, and a film forming apparatus using various low-temperature film forming methods such as a plasma CVD apparatus, a PVD apparatus, a vacuum evaporation apparatus, a sputtering apparatus, and an ion plating apparatus can be used.

In this state, if necessary, a preliminary heat treatment is performed at a temperature and pressure higher than the film forming temperature of the core layer 4 'and lower than the heating temperature of the later-described heating / pressing treatment.

Next, a predetermined waveguide pattern is formed on the surface of the core layer 4 'by photoresist, and etching such as RIE is performed to form the waveguide core 4 having a predetermined pattern (FIG. 3B). ).

Thereafter, an upper cladding layer 5 having a low refractive index and containing SiO ₂ as a main component is formed by the same low-temperature film forming method as described above (FIG. 3C). At this time, if a plurality of cores 4 are formed close to each other, the voids 8 may be generated between the adjacent cores 4 because the SiO ₂ forming the upper cladding layer 5 is not sufficiently filled.

Therefore, the optical waveguide 1 is heated and pressurized from the surroundings by the HIP method with the upper clad layer 5 exposed (heating / pressing treatment), so that the void 8 has a size that does not cause any practical problem. The internal stress generated at the time of film formation on the substrate 2 and each of the layers 4 and 5 is removed (FIG. 3D). In this HIP method, an inert gas such as argon (Ar) is
It is desirable to maintain the state of being pressurized to 00 kgf / cm ² and heated to 1100 ° C. for about 2 hours. Here, in the heating / pressing process by the HIP method, the entire optical waveguide 1 is uniformly pressed from the surroundings, so that there is no fear that the core shape or the like changes.

The present inventors observed the disappearance of the void 8 when the temperature and pressure conditions in the HIP method were changed parametrically as shown in Table 1. still,
In Table 1, the temperatures are 800 ° C, 1000 ° C and 110 ° C.
0 ° C and the pressure was 300 kgf / cm ² , 100
^{0kgf / cm 2, 1500kgf / cm} 2 and 170
It is changed to 0 kgf / cm ² .

[0027]

[Table 1]

According to Table 1, the pressure is 300 kgf /
cm^Two And 1000kgf / cm^Two And when the temperature is 80
At 0 ° C., it is difficult to eliminate void 8
It became clear. Also, the pressure is 1500 kgf / c
m^Two When the temperature is 1100 ℃ or more, void 8
Can be extinguished, pressure is 1700kgf / cm ^Two 
Void 8 disappears when the temperature is over 1000 ° C
It became clear that it could be done.

Therefore, in the present embodiment, the heating and pressurizing conditions by the HIP method are set such that the pressure is 1500 kgf / cm.
² and the temperature is 1100 ° C, but the pressure is 170
The temperature may be 0 kgf / cm ² and the temperature may be 1000 ° C. or higher. However, the processing temperature and pressure are set to the minimum as long as voids can be filled.

Here, when the heating and pressurizing treatment is performed by the HIP method, there is a concern that argon (Ar) may enter the upper clad layer 5 to lower the durability and the like. In the range, that is, when the temperature and pressure are such that the void 8 is reduced to a size having no practical problem or eliminated and the internal stress generated during the film formation on the substrate 2 and each of the layers 4 and 5 is removed, the upper cladding layer It has been found by durability evaluation that the optical waveguide of the present configuration has no problem in durability even if argon (Ar) enters the interior of the optical waveguide 5. Therefore, the protective film can be omitted in the case of performing the heating and pressurizing treatment by the HIP method, and the process is simplified.

Finally, the substrate 2 is cut by a dicing apparatus.
Is cut into a predetermined shape, and the end faces of the input and output ends 6 and 7 are polished to be optically flattened, thereby obtaining individual optical waveguides 1 such as an optical star coupler as shown in FIG.

FIG. 5 is a sectional view similar to FIG. 2 of the second embodiment of the present invention. In this configuration, a core 4 is formed on a substrate 2 made of glass or ceramic such as quartz via a buffer layer (lower cladding layer) 3 so as to cover the core 4 and a portion of the buffer layer 3 where the core 4 is not provided. An upper clad layer 5 is formed.

The procedure for manufacturing the optical waveguide 1 will be described below with reference to FIGS. 6 (a) to 6 (e). First,
A buffer layer 3 mainly composed of SiO ₂ is formed on the surface of the substrate 2 by a CVD method as a low-temperature film forming method as in the first embodiment (FIG. 6A).

Next, the CV is similarly applied to the surface of the buffer layer 3.
A core layer 4 'mainly composed of SiO ₂ is formed by the method D (FIG. 6B). At this time, as in the first embodiment, a dopant for adjusting the refractive index is added to the core layer 4 '. Here also, a doping agent for lowering the refractive index is added when forming the buffer layer 3 as needed, and a doping agent for lowering the refractive index is also added when forming the upper cladding layer 5 to adjust each refractive index. Is also good. In this state, if necessary, heat is applied from the surroundings at a high pressure or a normal pressure to perform preliminary heat treatment.

Next, a predetermined waveguide pattern is formed on the surface of the core layer 5 by using a photoresist, and etching such as RIE is performed, so that the waveguide core 4 having the predetermined pattern is formed.
Is formed (FIG. 6C).

Next, SiO _{2 is formed} by the same CVD method as described above.
The upper clad layer 5 having a low refractive index and containing as a main component is formed (FIG. 6D). Then, the optical waveguide 1 is heated and pressurized from the periphery by the HIP method in a state where the upper clad layer 5 is exposed (heating / pressing treatment), so that the void 8 is reduced to a size having no practical problem. Or the substrate 2 and the layers 3, 4, 5
Is removed (FIG. 6 (e)). afterwards,
By performing the same cutting, polishing, and the like as described above, the optical waveguide 1 is completed.

FIGS. 7A to 7E show a third embodiment of the present invention.
FIG. 4 is a process explanatory view similar to FIG. 3, showing the embodiment. In the optical waveguide 11 having this configuration, a concave portion 12a is formed in a substrate 12, and a core 14 is formed in the concave portion 12a. The upper clad layer 15 is formed on the surfaces of the substrate 12 and the core 14 which are on the same plane.
(E)).

The procedure for manufacturing the optical waveguide 11 is as follows. First, a predetermined waveguide pattern is formed by a photoresist on the surface of a glass substrate 2 made of quartz or the like, and etching such as RIE is performed to form a concave portion 12a having a predetermined pattern. Is formed (FIG. 7A).

Next, the core layer 14 'is formed by the same low-temperature film forming method as described above (FIG. 7B), and the refractive index is about 0.2% to 0.8% higher than that of the glass substrate 2 as described above. The dopant for adjusting the refractive index is added to the core layer 14 ′ so that
To be added. At this time, the voids 18 may be generated because the SiO ₂ forming the core layer 14 ′ is not sufficiently filled in the recess 12 a.

Therefore, the optical waveguide 11 is provided with the core layer 14 '.
In the state where is exposed, it is heated from the surroundings by the HIP method,
By applying pressure (heating / pressing treatment), void 1
8 is reduced to a practically acceptable size or eliminated, and the internal stress generated at the time of film formation on the substrate 2 and the core layer 14 'is removed (FIG. 7C).

Next, the core layer 14 'is removed by etching or polishing to expose the surface of the substrate 2 and flatten it (FIG. 7D).

Next, an upper clad layer 15 mainly composed of SiO ₂ and having a low refractive index is formed by the same low-temperature film forming method as described above (FIG. 7E). Thereafter, the same cutting, polishing, and the like are performed as described above, and the optical waveguide 11 is completed.

FIGS. 8A to 8F show a fourth embodiment of the present invention.
It is a process explanatory view showing an embodiment. The optical waveguide 11 of this configuration is provided with a recess 1 in a buffer layer 13 formed on a substrate 12.
3a are formed, a core 14 is formed in the recess 13a, and the buffer layer 13 and the core 14
The upper clad layer 15 is formed on the surface of FIG.

The procedure for manufacturing the optical waveguide 11 is as follows. First, the same CV as described above is placed on the surface of a glass substrate 12 made of quartz or the like.
The buffer layer 13 is formed by the method D (FIG. 8A).
Then, a predetermined waveguide pattern is formed on the buffer layer 13 by a photoresist, and etching such as RIE is performed to form a concave portion 13a having a predetermined pattern (FIG. 8B).

Next, the core layer 14 'is formed by the same CVD method as described above (FIG. 8C), and the refractive index is about 0.2% to 0.8% higher than that of the glass substrate 12 as described above. The doping agent for adjusting the refractive index is added to the core layer 1 so as to increase the refractive index.
Add to 4 '. At this time, the core layer 1 is placed in the recess 13a.
Voids 18 may be formed due to insufficient filling of the SiO ₂ forming 4 ′.

Therefore, the optical waveguide 11 is provided with the core layer 14 '.
In the state where is exposed, it is heated from the surroundings by the HIP method,
By applying pressure (heating / pressing treatment), void 1
8 is reduced to a practically acceptable size or eliminated, and the internal stress generated during film formation on the substrate 12 and the core layer 14 'is removed (FIG. 8D).

Next, by performing etching or polishing, the unnecessary core layer 14 ′ is removed to expose the surface of the substrate 12, and the surface of the core 14 and the surface of the substrate 12 are flattened (FIG. 4B). FIG. 8 (e).

Thereafter, S is formed by the same CVD method as described above.
An upper cladding layer 15 having a low refractive index containing iO ₂ as a main component is formed (FIG. 8F). Thereafter, the same cutting, polishing, and the like are performed as described above, and the optical waveguide 11 is completed.

[0049]

As is apparent from the above description, according to the method for manufacturing an optical waveguide according to the present invention, a core layer is formed directly on the surface of a glass substrate and patterned into a desired core shape. After forming a cladding layer on top,
After applying heat / pressure treatment at a temperature and pressure higher than the film formation temperature of each layer, or directly forming a core layer in a concave portion formed to have a desired core shape on the surface of a glass substrate By performing a heating and pressurizing process at a temperature and pressure higher than the core layer forming temperature and forming a clad layer thereon, the process can be simplified,
A high-precision lower cladding layer with uniform density can be easily obtained,
By forming the core and the upper clad layer thereon, the overall accuracy is also improved, so that the loss of signal light can be reduced. In addition, by applying heat and pressure treatment after film formation, residual internal stress of each layer disappears, and even if a void is generated in the upper clad layer or core during film formation, it can be closed, further reducing the loss of signal light. Can be.

Further, a core layer is formed directly or via a buffer layer on the surface of the substrate, the core layer is patterned into a desired core shape, and a clad layer is formed on the core layer. Heat and pressure treatment at a temperature and pressure higher than the film temperature is performed with the clad layer exposed on the surface,
Alternatively, a concave portion is formed on the surface of the substrate or on the surface of the buffer layer laminated thereon so as to form a desired core shape,
After the core is formed in the recess, the core is exposed to heat and pressure at a temperature and pressure higher than the core's film formation temperature, and the cladding layer is formed on the core to protect the core. Generation of thermal stress between the film and the cladding layer can be prevented, and the process can be simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical star coupler as an optical waveguide according to a first embodiment to which the present invention is applied.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIGS. 3 (a) to 3 (d) are process explanatory views showing a process of manufacturing the optical waveguide of FIG.

FIG. 4 is a conceptual diagram illustrating a CVD method.

FIG. 5 is an enlarged sectional view of an optical waveguide according to a second embodiment to which the present invention is applied.

6 (a) to 6 (e) are process explanatory views showing a manufacturing process of the optical waveguide of FIG. 5;

FIGS. 7A to 7E are process explanatory views showing a manufacturing process of an optical waveguide according to a third embodiment to which the present invention is applied.

FIGS. 8A to 8F are process explanatory views showing a manufacturing process of an optical waveguide according to a fourth embodiment to which the present invention is applied.

FIG. 9 is an enlarged cross-sectional view of an optical star coupler as a conventional optical waveguide.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical waveguide 2 glass substrate 3 buffer layer 4 core 4 ′ core layer 5 upper cladding layer 6, 7 input / output end 8 void 11 optical waveguide 12 glass substrate 13 buffer layer 14 core 14 ′ core layer 15 upper cladding layer 18 void 22 reaction Chamber 23 Holder 24 Heater 31 Optical waveguide 32 Substrate 33 Buffer layer 34 Core 35 Upper cladding layer 38 Void

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yutaka Natsume 3-10-10, Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Japan Co., Ltd. (72) Inventor Takayuki Senda 3--10, Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Japan F term (reference) within 2H047 KA04 PA00 PA03 PA11 PA21 QA04 TA31 TA42

Claims (7)

[Claims] 1. A method for manufacturing an optical waveguide having a core covered by a clad layer, comprising: forming a core layer directly on a surface of a glass substrate, patterning the core layer into a desired core shape, and forming a clad layer on the core layer. A method for manufacturing an optical waveguide, comprising, after forming a layer, performing a heating / pressing process at a temperature and pressure higher than the film forming temperature of each layer. 2. A method for manufacturing an optical waveguide having a core covered by a cladding layer, wherein a concave portion is formed on a surface of a substrate made of glass so as to have a desired core shape, and a core is formed in the concave portion. And then subjecting the core to a heating and pressurizing treatment at a temperature and pressure higher than the film forming temperature, and forming a clad layer on the core. 3. A method for manufacturing an optical waveguide having a core covered by a cladding layer, comprising forming a core layer directly on a surface of a substrate or via a buffer layer, and forming the core layer into a desired core shape. Patterned into
After forming a cladding layer on the upper part thereof, a heating / pressing process at a temperature and pressure higher than the film forming temperature of each layer is performed in a state where the cladding layer is exposed on the surface. Method. 4. A method for manufacturing an optical waveguide having a core covered by a cladding layer on a substrate surface, wherein a desired core shape is formed on the surface of the substrate or on the surface of a buffer layer laminated thereon. After forming a concave portion and forming a core in the concave portion, a heating / pressing process at a temperature and pressure higher than the film forming temperature of the core is performed in a state where the core is exposed on the surface, and a cladding layer is formed on the upper portion. A method for manufacturing an optical waveguide, comprising: 5. One or more selected from phosphorus (P), titanium (Ti), germanium (Ge), aluminum (Al), boron (B) and fluorine (F) to adjust the refractive index of the core. The method of manufacturing an optical waveguide according to claim 1, wherein two or more dopants are added to the core. 6. The method of manufacturing an optical waveguide according to claim 1, wherein the heating / pressing treatment is performed by a hot isostatic pressing method. 7. The method according to claim 1, wherein each of the layers is formed by one of a chemical vapor deposition method, a physical vapor deposition method, and a low-temperature film forming method in which these are combined.
The method for manufacturing an optical waveguide according to any one of the above.