JPH05281427A - Optical waveguide device and its production - Google Patents

Abstract

PURPOSE:To prevent the fatigue of a glass layer formed with a waveguide. CONSTITUTION:An optical waveguide layer 4 consisting of quartz glass formed by a flame deposition method is provided on a substrate 2 consisting of a quartz wafer. This optical waveguide layer 4 consists of a core part 4a and a clad part 4b. The surface of the optical waveguide layer 4 and the flanks of the substrate 2 are coated with carbon films 6 consisting of the thermally decomposed carbon formed by thermal CVD. This optical waveguide device is fixed by an adhesive into a metallic package and is eventually used outdoors and in various other environments. The thermal cracked carbon which is extremely dense and hardly allows the permeation of gases is used as the carbon film 6 and, therefore, the adhesion of steam on the surface of the optical waveguide layer 4 is effectively prevented. Further, the progression of cracking is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate type optical waveguide device having an optical waveguide used in optical communication and other fields, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
The quartz-based flat plate waveguide device is used by being packaged with a metal such as stainless steel. At this time, the waveguide device and the metal packaging material are fixed with an adhesive such as resin. Therefore, there is a problem that the waveguide device is easily deteriorated due to a large difference in coefficient of thermal expansion between the metal of the packaging material and the silica glass of the waveguide device. Specifically, for example, when the packaging material and the waveguide device are fixed at room temperature and then this device is used at room temperature and high temperature, the waveguide device is subjected to tensile stress.
If minute scratches are present on the surface of the quartz glass constituting the waveguide device, stress concentrates on the scratched portions, and cracks progress from there. Such a phenomenon is called fatigue, and when water is adsorbed in the cracks, the progress of the cracks is significantly accelerated, and eventually the waveguide formed in the quartz glass of the waveguide device is destroyed. Will be. Moreover, since the quartz glass layer formed on the upper part of the waveguide device is formed in a thin film shape from the beginning by the flame deposition method or the like, there is a high possibility that the surface will be scratched,
In addition, the exposed area of the quartz glass layer is extremely large, and the probability of the existence of scratches is accordingly high. Therefore, in such a waveguide device, it is extremely necessary to prevent the progress of cracks generated in the quartz glass layer.

Therefore, an object of the present invention is to provide a flat plate type optical waveguide device which prevents fatigue of a glass layer on which a waveguide is formed and operates stably for a long period of time, and a method of manufacturing such an optical waveguide device. To do.

[0004]

In order to solve the above problems, in a flat plate type optical waveguide device according to the present invention, (a) an optical waveguide layer formed on a substrate, and (b) a surface of the optical waveguide layer. And a carbon thin film layer that covers

The first method for manufacturing a flat plate type optical waveguide device according to the present invention includes (a) a step of heating a substrate on which an optical waveguide layer is formed in a reaction vessel, and (b) an inside of the reaction vessel. And a step of forming a thin film layer of CVD carbon on the surface of the optical waveguide layer by introducing a gas containing a raw material.

Further, in the second method for manufacturing a flat plate type optical waveguide device according to the present invention, a glass fine particle layer is deposited on a substrate by a flame deposition method, and the glass fine particle layer is heated to a high temperature to be transparent. An optical waveguide layer is formed from the glass film thus obtained. Here, in the present manufacturing method, after heating and transparentizing the upper clad layer constituting the optical waveguide layer in the reaction vessel, the gas containing the raw material is introduced into the reaction vessel to form the optical waveguide layer. It is supposed to include a step of forming a thin film layer of CVD carbon on the surface.

[0007]

Since the flat plate type optical waveguide device described above is provided with the carbon thin film layer covering the surface of the optical waveguide layer, it is possible to prevent water from adsorbing to the minute cracks formed on the surface of the optical waveguide layer. It is possible to significantly reduce the progress of cracks. As a result, the waveguide formed in the optical waveguide layer can be prevented from being broken, and the optical waveguide device can be stably operated for a long period of time.

In the first method of manufacturing a flat plate type optical waveguide device according to the present invention, a thin film layer of CVD carbon is formed on the surface of the heated optical waveguide layer. Since the CVD carbon thus obtained is dense, it is possible to effectively prevent the adsorption of water on the cracks.

Further, in the second method for manufacturing a flat plate type optical waveguide device according to the present invention, after heating and making the upper clad layer constituting the optical waveguide layer transparent in the reaction vessel, A thin film layer of CVD carbon is formed on the surface of the optical waveguide layer by introducing a gas containing a raw material into the optical waveguide layer. Therefore, dense CVD carbon can be easily formed, and the adhesion between the upper clad layer and the thin film layer can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical waveguide device and a method of manufacturing the same according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a side sectional view showing the structure of a flat plate type silica-based optical waveguide device according to an embodiment. In this embodiment, in order to prevent fatigue of the glass layer on which the waveguide is formed,
The surface of this glass layer for waveguides is to be coated with a pyrolytic carbon film which is recognized as having the most excellent properties as a water blocking protective film.

An optical waveguide layer 4 made of silica glass formed by the flame deposition method is provided on a substrate 2 made of a silicon wafer, a quartz wafer or the like. The optical waveguide layer 4 includes a core portion 4a and a clad portion 4b.
The surface of the optical waveguide layer 4 and the side surface of the substrate 2 are covered with a carbon film 6 made of pyrolytic carbon formed by thermal CVD. This optical waveguide device is fixed in a metal package with an adhesive and used outdoors or in various other environments.

The operation of the optical waveguide device of FIG. 1 will be briefly described. In general, the optical waveguide layer 4 may remain with various stresses applied during the manufacturing process. In addition, stress is applied due to the difference in the coefficient of thermal expansion with the substrate material. In this case, there is no problem if the stress applied to the optical waveguide layer 4 is a compressive stress, but when the stress is a tensile stress, the stress concentrates on minute scratches present on the surface of the optical waveguide layer 4, and cracks start from here. May progress or grow. However, in the device of FIG. 1, since the carbon film 6 is provided on the surface of the optical waveguide layer 4 and the carbon film 6 is made of pyrolyzed carbon which is very dense and does not easily allow gas to permeate, the optical waveguide layer 4 Water vapor can be effectively prevented from adhering to the surface of the above, and further, the progress of cracks as described above can be stopped or suppressed. Moreover, when pyrolytic carbon is used as the carbon film 6, not only water vapor but also hydrogen can be blocked or suppressed, so that transmission loss of an optical signal transmitted through the core portion 4a in the optical waveguide layer 4 is reduced. It is possible to suppress the adverse effect of hydrogen.

FIG. 2 shows an apparatus for manufacturing the optical waveguide device of FIG. In the reaction furnace 10 for thermal CVD, quartz is used as the material of the electric tubular furnace and the reaction tube. In the reaction furnace 10, a plurality of device substrates 12 supported by a rotating shaft are arranged. The device substrate 12 is one immediately after the optical waveguide layer 4 made of silica glass is formed on the substrate 2 such as the above-mentioned quartz wafer. The periphery of the reaction furnace 10 is covered with a heater 14 to uniformly heat the internal device substrate 12. As the heater 14, an infrared lamp, an infrared laser, a high frequency induction coil, or the like can be used in addition to the resistance wire heater shown in the drawing. The raw material supply pipe 16 extends inside the reaction furnace 10 and is connected to each device substrate 12
The raw material is uniformly supplied on the top.

A specific manufacturing example of the optical waveguide device of FIG. 1 will be briefly described.

First, the optical waveguide layer 4 is formed on the substrate 2. Since the formation of the optical waveguide layer 4 by the flame deposition method is known, the description is omitted.

Next, the device substrate 12 is set in the device as shown in FIG. 2 and heated to 1200.degree. In this state, a raw material gas is introduced into the reaction furnace 10 through the raw material supply pipe 16 to deposit and deposit a thin film of pyrolytic carbon on the device substrate 12. Specifically, ethylene (C ₂ H ₄ ) gas and chloroform (CHCl ₃ ) are each added to 200 cc.
/ Min and 275 cc / min. As a carrier gas of chloroform, He was used, and this was supplied simultaneously with the raw material at a flow rate of 600 cc / min. Further, N ₂ was supplied at 1000 cc / min as its dilution gas. These gases were mixed and then introduced into the reaction furnace 10 through an introduction pipe that was heated to prevent condensation. The supply of such raw material gas is stopped after a predetermined time, and the apparatus substrate 12 on which the thin film of pyrolytic carbon is deposited is gradually cooled. Device board 12
The thickness of the carbon film 6 covering the film was about 100 nm.

A test for fatigue of the obtained optical waveguide device will be described below. The optical waveguide device is a stainless steel plate (t
= 2 mm) and fixed with an adhesive, and about 50 g of dry sand was sprinkled from a height of about 10 cm. Next, after the relics on the surface of the optical waveguide device are blown off, about 10
Hold for 0 hours. When the state of the surface of the optical waveguide layer of the optical waveguide device after this acceleration test was observed by SEM, no cracks or progress of cracks were observed at all.

For comparison, an acceleration test was also conducted on a normal optical waveguide device in which the surface treatment of the carbon film was not performed. In this case, the formation of the optical waveguide layer was similar to that in the example. As a result of observing the surface state of the optical waveguide layer after the acceleration test with SEM, some cracks and cracks were found.

The present invention is not limited to the above embodiment. For example, in the above manufacturing method, various carbon compounds can be used as the source gas. However, using a mixed gas of a hydrocarbon gas and a gas containing halogen such as Cl ₂ or a halogenated hydrocarbon such as chloroform is advantageous in terms of the growth rate of the carbon film and its properties. In this case, H as carrier gas
In addition to e, Ar, N _{2 and the} like can also be used.

Further, the thickness of the carbon film may be arbitrary. However, if the carbon film is too thin, the gas permeability becomes large, and conversely, if it is too thick, cracks will form in the entire film.
It is preferable that the film thickness is about the same.

Further, as the structure of the carbon film, a graphite structure or an amorphous structure based on graphite is preferable from the viewpoint of gas barrier property.
In order to obtain such a structure, the temperature of the device substrate 12 in the reaction furnace 10 shown in FIG. 2 is desirably 800 ° C. or higher, preferably 1000 ° C. or higher. However, in order to prevent deterioration of the optical waveguide layer and the like, it is desirable to set the temperature to 1400 ° C or lower. In some cases, the amorphous structure of the carbon film can be controlled by pulling up the device substrate 12 from the reaction furnace 10 after forming the carbon film.

Further, it is preferable that the step of forming the carbon film is performed continuously while controlling the temperature in succession to the step of sintering the clad layer, which is the final step of the optical waveguide layer forming step. This is because not only the process can be simplified but also the adhesion between the carbon film and the optical waveguide layer can be made excellent.

Further, a carbon film may be formed on the entire periphery of the device substrate 12. Similar fatigue prevention can be achieved by depositing a carbon film only on the upper surface of the optical waveguide layer and leaving the side surface exposed.

[0025]

As described above, since the flat plate type optical waveguide device according to the present invention has the carbon thin film layer covering the surface of the optical waveguide layer, it is possible to reduce the amount of the fine particles formed on the surface of the optical waveguide layer. Water can be prevented from adsorbing to the cracks, and the progress of the cracks can be significantly reduced. As a result, the waveguide formed in the optical waveguide layer can be prevented from being broken, the optical waveguide device can be stably operated for a long period of time, the environment resistance of the optical waveguide device can be improved, and its handling is easy. In addition, the long-term reliability can be significantly improved.

Further, in the first and the second flat plate type optical waveguide device manufacturing methods according to the present invention, the thin film layer of CVD carbon is formed on the surface of the optical waveguide layer. Since the CVD carbon thus obtained is dense, it is possible to effectively prevent the adsorption of water on the cracks.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a configuration of an optical waveguide device according to an embodiment.

FIG. 2 is a sectional view showing an apparatus for manufacturing the optical waveguide device of FIG.

[Explanation of symbols]

 2 ... Substrate, 4 ... Optical waveguide layer, 6 ... Thin film layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Hirose 1 Taya-cho, Sakae-ku, Yokohama, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Shinji Ishikawa 1 Taya-cho, Sakae-ku, Yokohama, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Masahide Saito 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries Co., Ltd. Yokohama Works

Claims (5)

[Claims] 1. A flat plate type optical waveguide device comprising an optical waveguide layer formed on a substrate and a carbon thin film layer covering the surface of the optical waveguide layer. 2. The optical waveguide device according to claim 1, wherein the thin film layer is pyrolytic carbon. 3. The optical waveguide device according to claim 1, wherein the thin film layer is graphite or amorphous carbon. 4. A step of heating a substrate on which an optical waveguide layer is formed in a reaction vessel, and a CVD process on the surface of the optical waveguide layer by introducing a gas containing a raw material into the reaction vessel.
And a step of forming a carbon thin film layer. 5. A flat plate type optical device for forming an optical waveguide layer from a glass film obtained by depositing a glass fine particle layer on a substrate by a flame deposition method and heating the glass fine particle layer to high temperature to make it transparent. In the method for manufacturing a waveguide device, after heating and making the upper clad layer constituting the optical waveguide layer transparent in a reaction vessel, the optical waveguide layer is introduced by introducing a gas containing a raw material into the reaction vessel. 1. A method of manufacturing a flat plate type optical waveguide device, comprising the step of forming a thin film layer of CVD carbon on the surface of the substrate.