JPH0875941A - Production of optical waveguide - Google Patents

Abstract

PURPOSE: To provide a production method of an optical waveguide so that the intraplane difference of waveguide loss can be largely decreased and the production conditions can be stabilized. CONSTITUTION: The core waveguide 5 of an optical waveguide is produced by the following method. A metal is vapor deposited on a ferroelectric crystal substrate 1 and the metal is patterned by photolithography and etching to obtain the same pattern as the core-waveguide pattern. Then, the substrate is heated in a furnace 4 to diffuse the metal into the substrate 1. In this production method, when the substrate 1 is placed in the furnace, the substrate 1 is mounted on a ground quartz glass plate 10, which is covered with a lid 11 of ground quartz glass.

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, and more particularly to a method for manufacturing an optical waveguide utilizing thermal diffusion of Ti.

[0002]

2. Description of the Related Art FIG. 3 is a conceptual diagram of a conventional method for manufacturing an optical waveguide.

In the figure, metal 2 is deposited on a ferroelectric crystal substrate 1 (diameter: about 76 mm), and the metal 2 is patterned by photolithography and etching so as to match the core waveguide pattern. , The electric furnace 4 which puts the substrate on a quartz dish 3 and is filled with an oxygen atmosphere
Put it in. In the electric furnace 4, the metal 2 is thermally diffused into the substrate 1, so that the core waveguide (length 5
0 mm) 5 is formed on the substrate 1 for 20 elements. In the figure, H indicates a heater.

Here, the oxygen atmosphere in the furnace 4 is
This is to prevent a layer for guiding light from being parasitically formed in the vicinity of the surface of the substrate 1 other than the portion where the metal 2 is deposited.

[0005]

In the electric furnace described above, the surface of the substrate is exposed to the oxygen atmosphere, so that a temperature difference occurs between the upstream portion and the downstream portion of the oxygen flow on the substrate. This temperature difference affects the rate of heat diffusion of the metal into the substrate, and causes the loss of elements formed on the substrate to be greatly different in the plane. Moreover, since the in-plane temperature distribution of the substrate is non-uniform, the manufacturing conditions of the optical waveguide become unstable. Furthermore, it is not suitable for mass production because the substrates cannot be stacked.

On the other hand, when a transparent quartz plate and a quartz lid are used, the atmosphere around the substrate is unlikely to be an oxygen atmosphere because the degree of adhesion between the dish and the lid is high. Unless in an oxygen atmosphere, a layer for guiding light is formed in a region other than a desired region. This waveguide layer is also one of the factors that increase the in-plane difference in loss.

Therefore, an object of the present invention is to solve the above-mentioned problems, to provide a method for manufacturing an optical waveguide in which the in-plane difference of the waveguide loss can be significantly reduced and the manufacturing conditions can be stabilized. is there.

[0008]

In order to achieve the above object, the present invention heats a substrate of a ferroelectric crystal having a patterned metal film formed on its surface in a furnace to diffuse the metal into the substrate. In the method of manufacturing the optical waveguide in which the core waveguide is formed by placing the substrate in the furnace, the substrate is placed on a plate made of quartz frosted glass, and the dish is covered with a quartz frosted glass. is there.

[0009]

According to the above construction, the container and the lid are placed on a plate made of quartz frosted glass, and a lid made of quartz frosted glass is placed on the plate as a container for containing the substrate for heat diffusion of metal. Since a gap is created between the container and the container, oxygen flows into the container through the gap and the container is filled with an oxygen atmosphere. Even if there is a temperature difference between the upstream part and the downstream part of the oxygen flow supplied to the furnace, oxygen gradually flows into the container, so that there is no effect on the thermal diffusion rate. Further, since the substrate is housed in the container, the in-plane temperature distribution becomes uniform, the in-plane difference in the waveguide loss can be greatly reduced, and the manufacturing conditions of the optical waveguide are stabilized. Further, since a plurality of containers can be stacked, mass production can be performed.

[0010]

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

FIG. 1 is a conceptual diagram of one embodiment of the method for manufacturing an optical waveguide of the present invention.

In the figure, LiN as a ferroelectric crystal
A case will be described where Ti is vapor-deposited as a metal 2 on a substrate made of bO ₃ and a core waveguide pattern having a width of about 5 μm is formed by photolithography and etching.
The same reference numerals are used for the same members as in the conventional example shown in FIG.

The substrate 1 is placed in a dish 10 made of frosted glass made of quartz, and a lid 11 made of frosted glass made of quartz is placed thereon.
, Put it in an electric furnace 4 and heat it in an oxygen atmosphere,
By diffusing Ti into the substrate 1, the core waveguide 5 is formed as shown in FIG.

The flow rate of oxygen supplied to the furnace 4 is about 0.6 liter / minute. The substrate 1 has a diameter of about 76 mm, and 20 elements having a length of about 50 mm are formed on the substrate 1. As shown in FIG. 2, the dish 10 has a digging portion 12 in the portion on which the substrate 1 is placed by the thickness t of the substrate 1, and the substrate 1 can be inserted into the digging portion 12. The lid has the same shape as the dish. The presence of the dug portion 12 prevents the surface of the substrate 1 and the lid 11 from coming into contact with each other.

When the lid 11 made of frosted glass made of quartz is not used, the loss of the core waveguide 5 has a large in-plane difference.
± 0.1 dB / cm. The loss was measured from the element number from 1 to 20 in order from the upstream part to the downstream part of the oxygen flow.
Element 1, 2, 3, 9, 10, 11, 1
A total of 9 elements of 8, 19, and 20 were performed.

On the other hand, when the lid 11 made of frosted glass made of quartz is used, the in-plane difference of the waveguide loss is small and is ± 0.0.
It is 1 dB / cm. The loss was measured in the same manner as when the lid 11 was not used.

When transparent plates are used as the plate 10 and the lid 11 made of frosted glass made of quartz, the substrate 1
A layer for guiding light is formed in the vicinity of the surface, except where the core waveguide pattern is formed. When this waveguide layer is formed, the in-plane difference of the waveguide loss is ± 0.2 dB / cm.
Is. Dish 10 and lid 11 made of frosted glass made of quartz
There is a large in-plane difference in the loss as compared with the case using.

As described above, according to the present embodiment, as a container for housing the substrate for heat diffusion of the metal, the container is placed on a plate made of quartz frosted glass, and the plate is covered with a lid made of quartz frosted glass. Since a gap is created between the plate and the lid, oxygen flows into the container through the gap and the container is filled with the oxygen atmosphere. Even if there is a temperature difference between the upstream part and the downstream part of the oxygen flow supplied to the furnace, oxygen gradually flows into the container, so that there is no effect on the thermal diffusion rate. Further, since the substrate is housed in the container, the in-plane temperature distribution becomes uniform, the in-plane difference in the waveguide loss can be greatly reduced, and the manufacturing conditions of the optical waveguide are stabilized.
Further, since a plurality of containers can be stacked, mass production can be performed.

[0019]

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

The temperature difference in the substrate during diffusion becomes small, and the in-plane difference in the waveguide loss is greatly reduced. Therefore, the yield in mass production is improved. Since the in-plane temperature distribution of the substrate is largely uniformed, the manufacturing conditions can be stabilized. Furthermore, since containers can be stacked, mass production is possible.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an embodiment of a method for manufacturing an optical waveguide of the present invention.

FIG. 2 is an external perspective view of the plate shown in FIG.

FIG. 3 is a conceptual diagram of a conventional method of manufacturing an optical waveguide.

FIG. 4 is an external perspective view of an optical waveguide.

[Explanation of symbols]

 1 substrate 2 metal 4 (electric) furnace 5 core waveguide 10 (made of frosted glass made of quartz) 11 (made of frosted glass made of quartz) lid

Claims (2)

[Claims] 1. A method of manufacturing an optical waveguide in which a core waveguide is formed by heating a ferroelectric crystal substrate having a patterned metal film formed on its surface in a furnace and diffusing the metal into the substrate. In the method for manufacturing an optical waveguide, the substrate is placed on a plate made of quartz frosted glass, and the plate is covered with a lid made of quartz frosted glass when the substrate is placed in the furnace. 2. The method of manufacturing an optical waveguide according to claim 1, wherein LiNbO ₃ is used for the ferroelectric crystal and Ti is used for the metal film.