JPS60262108A - Production of optical waveguide - Google Patents

Abstract

PURPOSE:To improve quality, ease of production, mass productivity, etc. by sticking a metallic film in which the refractive index in the oxide state is higher than the refractive index of a glass substrate onto the glass substrate and diffusing and oxidizing the metallic film to the glass substrate thereby producing an optical waveguide. CONSTITUTION:The metallic film 12 is stuck onto the glass layer 11 of the glass substrate 10 and a resist film 13 is formed on the film 12. The films are then subjected to pattern printing, resist development, etching and resist removal so that the metallic film 12 having the prescribed shape to allow the formation of the optical waveguide remains on the glass layer 11. The stage for diffusing the film 12 to the glass substrate 10 and the stage for oxidizing the film 12 are executed in optional sequence. The glass layer 11 in the porous or opague state is vitrified to transparent glass and the optical waveguide part 14 is formed on the substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an optical waveguide having a waveguide portion on a glass substrate with a higher refractive index than the glass substrate.

(Prior Art) With the development of optical communications, there is an increasing demand for silica-based optical waveguides having a film thickness comparable to the core diameter of an optical fiber.

Usually, a quartz-based optical waveguide consists of a quartz-based glass substrate 1, a core film 2 formed thereon, and a protective glass film 3, as shown in Fig. 2. In some cases, the glass film 3 may be omitted. However, the core film 2 has a higher refractive index than the glass substrate 1 and the glass film 3, and its film thickness and hb refractive index difference are appropriately determined depending on the application.

Conventionally, in the invention of JP-A No. 49-10054, as a method for manufacturing the optical waveguide, S r Cla is deposited on a glass substrate.
A gas phase raw material such as .

It has already been pointed out that this method lacks uniform reproducibility in the refractive index value and film thickness of the optical waveguide.
Various improvements have been attempted to address this problem.

For example, in the invention disclosed in JP-A-58-8570, glass particles are deposited on a glass substrate in a reaction tube similar to a CVD reaction tube known in the field of semiconductor film formation.

["°"-1,=oM'#=-r:b, meh*"'
57. There is still room for improvement in that the loss is large.

In addition, there is a method to form a uniform glass film by rotating the glass substrate with a turntable, as announced at the 1983 National Conference of the Optical and Radio Division of the Institute of Electronics and Communication Engineers (IEICE), 1983. A liquid phase doping method is also known in which a porous glass layer is impregnated, patterned by exposure, and then impregnated with a dopant solution, but the former requires large equipment and is difficult to mass-produce. In the latter case, there is a problem in achieving high quality.

More recently, a method for manufacturing optical waveguides using C02 laser processing was announced by the Society of Applied Physics Society in 1988, but this method also has a slow processing speed and lacks practicality.

(Problems to be solved by the invention) The present invention aims to solve the above-mentioned problems by improving quality, ease of manufacture,
The present invention aims to provide a method for manufacturing an optical waveguide that is highly practical and has excellent mass productivity.

(Means for Solving the Problem) A method for manufacturing an optical waveguide according to the present invention involves depositing a metal film having a refractive index in an oxide state higher than that of the glass substrate on a glass substrate, and after this step, depositing a metal film on a glass substrate. The method is characterized in that the step of diffusing the film onto the glass substrate and the step of oxidizing the metal film are carried out in any order.

(Function) In the case of the method of the present invention, since an unoxidized metal film is deposited on the glass substrate, the metal film adhesion process is facilitated, and the metal film is diffused onto the glass substrate through the subsequent diffusion process and oxidation process, and the metal film is oxidized. When forming an optical waveguide by controlling the diffusion state of the metal, the dimensions of the optical waveguide (diffusion depth and width) can be achieved with high precision.Furthermore, each process is not difficult, and the number of processes is also compared. Not only is mass production possible due to the small number of targets, but also products with excellent characteristics and quality can be obtained with good reproducibility due to the above-mentioned controllability.

(Example) Next, an example of the method of the present invention will be described with reference to the drawings.

FIG. 1 shows one embodiment of the method of the present invention in the order of its steps.

In the figure, 10 is a quartz-based glass substrate, 11 is a porous or opaque (opaque sintered glass) silica-based glass layer formed on the metal-attached side of the glass substrate 10, and 12 is the glass layer. A metal film deposited on the ll.

The glass substrate 10 is made of S r 02 glass, Vycor glass, etc., and the glass layer 11 of the glass substrate 10
To make this into a porous state, a glass raw material such as S + Cl 4 is oxidized or flame-hydrolyzed, and the reaction product, soot-like glass fine particles, is transferred to the glass substrate 10.
It can be formed by depositing on top.

As another means for forming the glass layer 11 in a porous state,
An organosilicon compound dissolved in a solvent, e.g. Si(O
A so-called sol-gel method for gelling CH3)4, Si(OC2H5)4, etc. can also be employed.

The entire glass substrate 10 may be porous or opaque.

The metal film 12 used is a material that easily diffuses into the glass and can react with the glass through oxidation treatment to form quartz glass having a higher refractive index than the glass substrate 1o. Specific examples of the metal include Ge, Pb, etc. , Zn, Zr, AI,
La, Nd, etc. are used.

On the glass layer 11 of the glass substrate 10 shown in FIG. 1(A), a metal film 12 is first attached by appropriate means as shown in FIG. 1(B).

Specific examples of metal film deposition means include metal vapor deposition using gaseous raw materials, melt application, and formation of a compound film followed by reduction.

Next, as shown in FIG. 1(c), a resist film 13 is formed on the metal film 12 by a known resist coating means.

Note that when producing a three-dimensional waveguide, metal etching becomes extremely easy if pattern formation is performed using the resist film 13 in the state of the metal film 12.

The following is the putter 1 shown in Figure 1 (D), (E), (F), and (G). 1. Each step of printing, resist development, etching, and resist removal is performed.

When the process up to FIG. 1 (g) is completed, the glass substrate 10
Only a metal film 12 having a predetermined shape that can form an optical waveguide section by subsequent oxidation treatment is left on the glass layer 11 .

The glass substrate 10 and its deposits that have undergone the process shown in FIG. 1 (G) are subjected to various treatments as shown in FIG. The glass layer 11 in a transparent or opaque state is made into transparent glass, and thus an optical waveguide section 14 serving as a core is formed on the glass substrate 10.

Oxidation, diffusion, and transparent vitrification of the metal film 12 in the above,
For example, evaporation is performed at 10°C/s in an oxidizing atmosphere.
This can be carried out by heating up to about 1500° C. at a temperature increase rate of in.

At this time, the metal may be diffused prior to oxidation, or conversely, the metal may be diffused after oxidation, or the metal oxidation and diffusion may be performed simultaneously.

What is important here is that the oxidation temperature of the metal is lower than its evaporation temperature, and therefore the oxidation temperature, diffusion temperature, etc. of the metal are set to satisfy this requirement.

As an example, the experimental results of the above temperature regarding Ge and Pb are shown: In the case of Ge, the oxidation start temperature = 850 to 850 °
, evaporation temperature: 1200°C, and in the case of pb, oxidation start temperature: 400°C, evaporation temperature: 1000 to 1100°C.

After completing the process shown in FIG. 1(H), a pure quartz glass layer may be formed on the glass substrate 10 that covers the optical waveguide section 14.

Next, specific examples of the method of the present invention will be explained.

A commercially available opaque quartz glass is used as the glass substrate 10. In specific example 1, a metal film 12 made of Ge metal particles is adhered and formed on the glass substrate 10, and in specific example 2, a metal film 12 made of PB metal particles is deposited on the glass substrate 10. The film 12 is deposited and each side is heated at 10°C/ll1 in air.
Heating was performed at a temperature increase rate of in.

In both specific examples 1 and z, oxidation and diffusion of the metal film 12 were observed within the temperature range of the experimental results described above.

Each side was heated to about 1500°C and brought to room temperature, and the metal oxide diffusion situation was investigated.
The following results were obtained.

In the case of specific example 1, the content of G e O2, which is a diffused substance, is about 2 weight 2 and the diffusion film thickness is 201 Lm, and in the case of specific example 2, the content of PbO, which is a diffused substance, is about 60 weight 2.
, the diffusion film thickness was 110007i or more.

In addition, as mentioned above, when the porous glass layer 11 is formed on the metal adhesion side of the glass substrate 10 and a specific example similar to the above is implemented, metal diffusion is affected by various porosity of the porous glass layer 11. Now you can adjust it.

To illustrate the porosity and layer thickness of the porous glass layer 11 produced by the flame hydrolysis reaction of S + Cl 4 , the porosity is 65z and the thickness of one layer is 50 gm.

(Effects of the Invention) As explained above, the method of the present invention includes a step of attaching a metal film whose refractive index in an oxide state is higher than that of the glass substrate on a glass substrate, and a step of diffusing the metal film into the glass substrate. , the process of oxidizing the metal film, etc. All of these processes are easy to implement and controllable when forming the optical liquid guide part, making it possible to mass-produce optical waveguides with uniform quality and good characteristics. become.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the method of the present invention in the order of its steps, and FIG. 2 is an explanatory diagram showing a conventional optical waveguide. 1011e, glass substrate 11... porous or opaque glass layer 12, solid metal film 14... optical waveguide agent patent attorney Yoshio Saito (Figure 1 (a) IIm - IO No. 2 Diagram (zr) m miko 2 l ni 34-

Claims (5)

[Claims] (1) A metal film whose refractive index in an oxide state is higher than that of the glass substrate is deposited on a glass substrate, and after this step, the metal film is diffused into the glass substrate, and the metal film is oxidized. 1. A method for manufacturing an optical waveguide, characterized in that the steps are performed in any order. (2) A patent for carrying out the process of diffusing the metal film onto the glass substrate in advance after completing the process of depositing the metal film on the glass substrate, and the process of oxidizing the metal film being carried out afterwards. A method for manufacturing an optical waveguide according to claim 1. (3) A patent for carrying out a step of oxidizing the metal film after completing the step of attaching the metal film onto the glass substrate, followed by a step of diffusing the metal film onto the glass substrate. A method for manufacturing an optical waveguide according to claim 1. (4) After completing the step of attaching the metal film onto the glass substrate, the step of diffusing the metal film onto the glass substrate and the step of oxidizing the metal film are performed simultaneously. A method for manufacturing an optical waveguide. (5) A method according to any one of claims 1 to 4, in which at least the metal adhesion side of the glass substrate is made into a porous or opaque glass layer, and a metal film is adhered on the glass layer. A method for manufacturing an optical waveguide.