JPS63175808A - Production of optical waveguide - Google Patents

Abstract

PURPOSE:To change not only the width but also the thickness of a waveguide layer and the numerical aperture in the lengthwise direction of a three- dimensional optical waveguide by bringing a solution containing a component, which raises the refractive index, into contact with a porous glass when this glass becomes transparent. CONSTITUTION:The porous glass like a split-phase glass subjected to etching treatment is formed, and the solution containing the component which raises the refractive index is brought into contact with the porous glass to allow this component to penetrate the porous glass when this glass becomes transparent. Thereafter, the glass is locally heated by irradiation of laser light or the like to dry or solidify said component, and the undried component is removed from the porous glass by a solvent. The whole of the glass is subjected to heat treatment to make a transparent glass of the porous glass, thereby producing the optical waveguide. At this time, only the part where said component is dried or solidified has a refractive index higher than that of the peripheral part and becomes a light propagating part. Thus, the three-dimensional optical waveguide is obtained where not only the width but also the thickness of the waveguide layer and the numerical aperture are changed on demand.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method of manufacturing an optical waveguide used in optical communication, optical information processing, etc.

(Prior Art) Conventional methods for producing an optical waveguide having a three-dimensional pattern or a refractive index pattern include the following. First, a glass thin film is formed on a substrate using a CVD method or a VAD method, and after a lithography process using a resist, a process such as reactive sputter etching is performed to form a substrate 31 as shown in FIG. 7 (8). A waveguide 32 having a three-dimensional pattern is formed. Alternatively, after applying a suitable mask by the same lithography process,
By doping the glass with a dopant at a high temperature, a waveguide 33 having a refractive index distribution pattern is formed on the substrate 31 as shown in FIG. 7(B).

Although the optical waveguides produced by these manufacturing methods have relatively good characteristics such as low loss by themselves, it is difficult to combine them with other optical elements such as semiconductor lasers (LDs) or add interference film filters in the middle. When inserting such an optical element, there is a problem that the optical coupling loss with the optical element and the optical coupling loss between the optical waveguides is large. In other words, with conventional manufacturing methods, it is relatively easy to change the width of the optical waveguide in terms of length and direction, but it is extremely difficult to change the thickness and numerical aperture of the waveguide layer. .

Therefore, for example, considering the case where an LD and an optical fiber are directly connected to an optical waveguide via an optical waveguide as shown in FIG. 7(A), it is necessary to improve the optical coupling between the LD and the optical waveguide. It is necessary to increase the numerical aperture of the optical waveguide. However, there is a problem in that increasing the numerical aperture of the optical waveguide increases coupling loss with the optical fiber.

(Problems to be Solved by the Invention) As described above, in the p-dimensional optical waveguide according to the prior art, the width can be relatively easily changed in the direction of the length, but the thickness of the waveguide layer can be changed relatively easily. It was very difficult to change the numerical aperture. Therefore, when coupling with other optical elements or inserting an optical element in the middle, there is a problem that the optical coupling loss with the optical element and the optical coupling loss between the optical waveguides is large.

An object of the present invention is to provide a method for manufacturing an optical waveguide in which not only the width but also the thickness and numerical aperture of the waveguide layer can be varied with respect to the length and direction of the three-dimensional optical waveguide.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve such an object, an optical waveguide manufacturing method according to the present invention includes the following steps.

First, a porous glass such as etched phase split glass is formed, and then the porous glass is brought into contact with a solution containing a component that increases the refractive index when it becomes transparent glass, and this component is added to the porous glass. infiltrate. After that,
The components are locally heated by laser beam irradiation or the like to dry or solidify them, and the undried components are removed from the porous glass using a solvent. Then, the entire structure is heat-treated to turn the porous glass into transparent glass, thereby producing an optical waveguide. At this time,
Only the portion where the component is dried and solidified has a higher refractive index than the surrounding area and becomes a light propagation part.

(Function) The method for manufacturing an optical waveguide according to the present invention can realize an optical waveguide in which not only the width of the three-dimensional optical waveguide but also the thickness and numerical aperture of the waveguide layer are changed as necessary. Hereinafter, the operation of the above technical means will be explained.

It is well known that metal alcoholates become metal oxides by being hydrolyzed, dried, and solidified, and that most oxides become one component of glass. In other words, when a solution containing a metal alcoholate, alcohol, water, etc. is infiltrated into a porous glass mainly composed of silica that remains after etching with a phase-separated double acid, hydrolysis and dehydration proceed in the porous glass, resulting in a sol-like or It becomes gel-like. At this time, heating locally will promote reaction, drying, and solidification only in that area. After heating locally, if the undried solution in the porous glass is removed with a solvent and then heat treated to make the porous glass transparent, the metal oxide will remain only in the heated area. Since almost all metal oxides work to increase the refractive index of the silica-based glass, the heated portion has a higher refractive index than the surrounding area, forming a light propagation section.

By removing the undried solution in porous glass with a solvent, the amount of remaining metal oxide can be controlled by heating temperature and time. By controlling the irradiation time, etc., the length, directional width, and numerical aperture of the optical waveguide can be changed as necessary.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram illustrating a process example of an embodiment of the first invention. First, glass 1 which is easily phase separated by heat treatment is formed. In this example, S! O2・75, B2O3・20
．． Glass having a composition of 5% Na2O was processed into a predetermined shape. This was heat treated at 600'C and 8203-N
A phase in which a20 is the main component and S! The phase was separated into a phase in which Oz was the main component.

Roughly, this was etched with hydrochloric acid, and 8203Naz
The phase in which O is the main component is eluted, and S! A porous glass 2 containing Oz as a main component was formed. Next, this is immersed in a solution 21 containing titanium alcoholate, water, and alcohol, and after the solution is permeated into the porous glass, ArF excimer laser light is applied to the part that should be the light propagation part using a lens with a large numerical aperture. Light is focused on a predetermined location, irradiated, and heated to generate a sol or gel containing titanium oxide.

Thereafter, it is immersed in carbon tetrachloride 22 to remove unreacted titanium alcoholate. Roughly heat this to 1000℃
An optical waveguide 6 was formed in the transparent glass 5 whose main component was 5IO2.

In this step, T! is doped into the quartz glass 5! O
The concentration of z is the concentration of titanium alcoholate in solution 21,
It can be controlled by the intensity of the irradiation light and the irradiation time. That is, since the progress of sol or gelation can be controlled by the intensity of the irradiation light and the irradiation time, by preparing a titanium alcoholate solution with a relatively high concentration, a light propagation part with a desired dopant concentration can be obtained. Also, io
In the heat treatment at 00° C., the volume shrinks by about 30% in the process of becoming transparent glass, but if the glass 1 is processed with the shrinkage taken into account in advance, an optical waveguide of the required dimensions can be obtained.

2 and 3 are diagrams showing an example of an optical waveguide manufactured using the process of the example shown in FIG. 1.

FIG. 2 shows a distributed coupling type branch and coupler, and FIG. 3 shows a star type splitter. Optical waveguides of 7° and 8.9° were created by scanning the laser beam to form the desired patterns for each.

FIGS. 4 to 6 are diagrams illustrating optical waveguides manufactured according to other embodiments of the first invention. In FIG. 4, the numerical aperture of the optical waveguide 10 changes in the longitudinal direction. The optical waveguide in Figure 4 changes the scanning speed of the laser beam,
The larger the numerical aperture of the optical waveguide, the lower the scanning speed. On the other hand, in FIG. 5, the size of the optical waveguide 11 changes in the longitudinal direction. The optical waveguide shown in FIG. 5 used two irradiation light sources, one of which was kept at a constant intensity, and the other was heated while changing its intensity. FIG. 6 is a diagram illustrating an example of an optical waveguide for an optical circuit manufactured by the manufacturing method shown in FIG. A groove 15 into which a branching interference filter is inserted is formed between the three optical waveguides 12, 13, and 14. The light incident on the optical waveguide 12 is converted into a lower mode while propagating through the optical waveguide 12, and the radiation angle near the groove 15 becomes smaller. Therefore, the optical coupling loss between the optical waveguide 12 and the optical waveguide 13 and between the optical waveguide 12 and the optical waveguide 14 is reduced.

Next, an embodiment of the second invention will be described in detail with reference to the drawings.

FIG. 7 is a diagram illustrating a process example of an embodiment of the present invention. First, a glass film 52 that easily undergoes phase separation is formed on a substrate 51 . In this embodiment, quartz glass is used as the substrate 51.
S i02 ・75.8203 ・20°Na2O・5
It was deposited by sputtering using glass with a composition of % as a target. This was heat treated at 600℃ to form B203-Na.
The phase was separated into a phase in which zO was the main component and a phase in which 5iOz was the main component. Roughly etch this with hydrochloric acid,
A phase containing B203-Na2O as the main component was eluted, and S!
A porous glass film 53 containing Oz as a main component was formed.

Next, this is immersed in a solution 521 containing titanium alcoholate, water, and alcohol, and after the solution is permeated into the porous glass membrane, the part to be used as the light propagation part is irradiated with ArF excimer laser light. Heating produces a sol or gel containing titanium oxide. After that, carbon tetrachloride 52
2 to remove unreacted titanium alcoholate. Furthermore, this was heat-treated at 100'c to form an optical waveguide 56.

In this step, T! is doped into the quartz glass 55!
The concentration of 02 can be controlled by the concentration of titanium alcoholate in the solution 521, the intensity of the irradiation light, and the irradiation time. That is, since the progress of sol or gelation can be controlled by the intensity of the irradiation light and the irradiation time, by preparing a titanium alcoholate solution with a relatively high concentration, a light propagation part with a desired dopant concentration can be obtained. Also, 1
In the heat treatment at 000'C, the volume shrinks by about 30% in the process of becoming transparent glass, but if the glass film 52 is deposited with the shrinkage taken into account in advance, the required waveguide layer thickness can be obtained. .

8 and 9 are diagrams showing an example of an optical waveguide manufactured using the process of the example shown in FIG. 1. FIG. 8 shows a distributed coupling type splitter and coupler, and FIG. 9 shows a star type splitter, in which optical waveguides 57° and 58 were formed by scanning the laser beam to form the desired pattern.

FIGS. 10 to 14 are diagrams illustrating optical waveguides manufactured according to other embodiments of the second invention. In FIG. 10, the width of the optical waveguide 59 changes in the longitudinal direction.

The optical waveguide shown in FIG. 10 was fabricated by changing the irradiation beam size of the laser beam.

On the other hand, in FIG. 11, the numerical aperture of the optical waveguide 510 changes depending on its length and direction. The optical waveguide shown in FIG. 11 was fabricated by changing the scanning speed of the laser beam, and decreasing the scanning speed as the numerical aperture of the optical waveguide increased. In FIG. 12, an optical waveguide 511 whose waveguide size changes in length and direction is embedded in a glass llll55. 10th
The optical waveguide shown in the figure was created by confining the laser beam with a lens with a large numerical aperture, and by lengthening the irradiation time for the larger waveguide size. As the irradiation time becomes longer, the temperature around the irradiation part increases, and the waveguide size can be increased.

Further, in FIG. 13, the thickness of the glass film 55' changes continuously, and the width of the optical waveguide 512 also changes continuously. The optical waveguide shown in FIG. 13 is produced by repeating the steps of immersing the substrate to be deposited in a solution containing a plurality of metal alcoholates to have the desired glass composition, pulling up, drying, and solidifying the glass film in the process of creating the glass film. The process was carried out using a method of forming.

At this time, the optical waveguide 512 was produced in the same manner as in FIG. 10 by continuously changing the pulling speed and reducing the pulling speed in thicker parts. Figure 14 shows the method shown in Figure 13.
It is a figure explaining the example of the produced optical waveguide for optical circuits. A groove 516 into which a branching interference film filter is inserted is formed between the optical waveguides 513, 514, and 515. The light incident on the optical waveguide 513 is converted into a lower mode while propagating through the optical waveguide 513, and the radiation angle near the groove 516 becomes smaller. Therefore, the optical coupling loss between the optical waveguide 513 and the optical waveguide 514 and between the optical waveguide 513 and the optical waveguide 515 is reduced.

[Effects of the Invention] As explained above, the method for manufacturing an optical waveguide according to the present invention can produce an optical waveguide in which not only the width of the three-dimensional optical waveguide but also the thickness and numerical aperture of the waveguide layer are changed as necessary. can be realized. Therefore, optical coupling between optical waveguides can be realized with low loss when coupling with other optical elements such as a semiconductor laser (LD) or when inserting an optical element such as an interference film filter in the middle.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of one process for carrying out the first invention;
6 to 6 are diagrams for explaining examples of optical waveguides manufactured by the manufacturing method of the present invention, FIGS. 7 to 14 are diagrams for explaining the second invention, and FIG. 15 is a diagram for explaining examples of optical waveguides manufactured by the manufacturing method of the present invention. It is a figure explaining the example of a wave path. 1.2, 3, 4.5'...Glass 6, 7.8, 9.10.11.12.13.14, 32
．． 33... Optical waveguide 21... Solution 22
...Solvent 31...Substrate 15...Groove 5
1.531...Substrate 52.53, 54, 55.55', 55"...Glass film 56, 57.58.59.510.511.51
2.513.514.515.532゜533...Optical waveguide 521...Solution 522...Solvent 516...
Mizo Agent Patent Attorney Yudo Nori Chika Takehana Kikuo 1 Police Figure 1 Figure 3 Figure 5 Figure 1z Figure 6 Figure 7 Figure 8 @9 Figure 10 Figure 11 Figure 12 Figure 13 Figure (A) (B) Figure 15

Claims (7)

[Claims] (1) A method for manufacturing an optical waveguide, which includes a step of forming porous glass, and a step of bringing the porous glass into contact with a solution containing a component that increases the refractive index when the porous glass becomes transparent glass. , comprising the steps of locally heating the glass to dry or solidify the components, removing the undried components from the porous glass, and heat-treating the entire porous glass to form transparent glass. Method for manufacturing optical waveguides. (2) Manufacturing the optical waveguide according to claim 1, wherein the porous glass is formed by phase-separating glass that is easily phase-separated by heat treatment and etching with acid. Method. (3) The method for manufacturing an optical waveguide according to claim 2, wherein the glass that easily undergoes phase separation is borosilicate glass containing 10% or less of an alkali metal oxide. (4) The method for manufacturing an optical waveguide according to claim 1, wherein the solution contains at least one type of metal alcoholate. (5) The method for manufacturing an optical waveguide according to claim 1, wherein the local heating is performed by irradiation with electromagnetic waves such as laser light. (6) In the method for manufacturing an optical waveguide, the first step is to form porous glass on the substrate, and to increase the refractive index of the porous glass deposited on the substrate and when the porous glass becomes transparent glass. a second contacting solution containing the components;
A third step is to locally heat this to dry or solidify the components, a fourth step is to remove the undried components from the porous glass, and then the whole is heat-treated to form transparent glass. A method for manufacturing an optical waveguide, comprising a fifth step of: (7) The glass film that easily undergoes phase separation is formed by repeating the steps of dipping the substrate to be deposited into a solution containing multiple metal alcoholates as required components, pulling it up, drying it, and solidifying it. 7. A method for manufacturing an optical waveguide according to claim 6.