JPS58118609A - Production of optical waveguide - Google Patents

Abstract

PURPOSE:To make coupling of an optical waveguide to optical fibers with high efficiency possible by penetrating metallic ions into substrates of glass or the like to increase the refractive index thereof, and applying an electric field while heating a diffusion source and the substrates thereby decreasing optical guiding loss, making the waveguide stable thermally and mechanically, and making the section thereof roughly circular. CONSTITUTION:A diffusion preventing layer 2, a thin film layer 3 of silver and an anode electrode 4 consisting of chromium are vapor deposited on a glass substrate 1. A cathode electrode of aluminum is vacuum deposited on the opposite side thereof. The substrate 1 is heated and an electric field is applied thereto to ionize the silver of the layer 3 and to penetrate the same into the substrate, whereby a high refractive index part of a semicircular section is obtained. Further, a mixture of sodium nitrate and clay is kneaded into paste and the paste is coated on the substrate and is dried; thereafter, the substrate is dried and heated and an electric field is applied thereto to embed the part 7 into the substrate 1, whereby the high refractive index part 7' of roughly a circular sectional shape is obtained and said part is acted as an optical waveguide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a dimensional waveguide formed in a substrate.

Optical waveguides formed on substrates play an important role in reducing the size and integration of optical circuits and improving their reliability. This optical waveguide basically has an extremely high refractive index t
- A core portion having a relatively low refractive index 't- is covered by a cladding portion having a relatively low refractive index 't. Conventionally, as a method for manufacturing such a rigid optical waveguide, a method has been known in which a fine amount of metal ions forming a high refractive index layer is diffused near the surface of a substrate to form an optical waveguide W&W. However, as shown in FIG. 1, this method has the disadvantage that the cross-sectional shape of the dimensional waveguide 102 formed on the substrate 101 is a thousand circles, which leads to a decrease in the coupling efficiency with the original fiber. Also, the original power propagating through the optical waveguide Wr102t is concentrated near the surface of the substrate 1010, which is affected by scratches, dust, etc. on the surface of the substrate 1010, resulting in a large scattering loss.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an optical waveguide that eliminates the above-mentioned drawbacks, has high coupling efficiency with the original fiber, and has low original propagation loss.

That is, the present invention provides a method of forming a high refractive index portion by selectively permeating a first metal ion, which permeates into the substrate and increases the refractive index of the substrate, into an optically transparent substrate. 1 and the high refractive index layer by infiltrating into the substrate a second metal ion which, when infiltrated into the substrate, makes the refractive index of the substrate smaller than the refractive index of the high refractive index layer. a second step of embedding a high refractive index portion inside the substrate; 2
The i@ consisting of a mixture of salt and clay containing metal ions of
A second metal ion diffusion source is provided, and the second metal ions are infiltrated into the substrate by heating the diffusion source and the substrate, melting the salt, and applying an electric field. The method for manufacturing an optical waveguide is characterized in that the second step is performed.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIGS. 2(a) to 2(d) are process diagrams showing one embodiment of the method for manufacturing an optical waveguide according to the present invention. As shown in FIG. 2(, l), first, a diffusion blocking layer 2 made of aluminum with a shiva pattern formed thereon by a lift-off method and a thin film of silver with a thickness of about 1 to 10 μm are deposited on a substrate l made of BK7 glass. A layer 3 and a positive electrode 4 made of chromium are successively formed by vacuum evaporation. Moreover, these diffusion prevention layers 2. of the substrate 1. A negative electrode 5 made of aluminum is formed by vacuum evaporation on the side where the silver thin film layer 3 and the positive electrode 4 are not formed.

Here, the diffusion prevention layer 2. Silver thin film layer 3. The substrate 1'i on which the positive electrode 4 and the negative electrode 5 are formed, 250 ° C. ~ 5
The silver in the silver thin film layer 3 is ionized by heating with a heater 6t to a temperature below the glass strain temperature of about 50° C. and applying an electric field of 2 to 300 V/sm. Let it penetrate inside. As a result, as shown in FIG. 2(b), a high refractive index portion 7 having a semicircular cross section is obtained near the surface of the substrate 1.

Next, the diffusion prevention layer 2. The high refractive index portion 7 of the substrate 1 from which the anode 4 and the cathode 5 have been removed and the surface has been exposed is coated with nitric acid on the next surface and the opposite surface.
A mixture of Jum and clay is made into a paste with water and applied. These serve as a diffusion source 8 for IJium ions (on the side where the high refractive index portion 7 is formed), and serve as an ion absorption layer 9 that absorbs sodium ions, etc. that have migrated from the substrate 1 on the opposite side. . Furthermore, an anode plate 10 and a cathode plate 11t each made of a titanium plate are installed on the opposite side of the diffusion source 8 and the ion absorption layer 9 from the substrate 1. Remove any moisture contained and dry thoroughly. Here, the substrate 1t'', 250
The sodium ion gold of the sodium nitrate in a molten state is heated using a heater 6 to a temperature below the glass strain temperature of approximately 550°C to 550°C, and an electric field of 2 to 300V/■ is applied to the substrate 1. The high refractive index portion 7 is embedded inside the substrate 1 by diffusion. Here, the diffusion source 81 ion absorption layer 9. When the anode plate lO and the cathode plate 11t are removed, as a result of the embedding, a high refractive index portion 7' having a substantially circular cross-sectional shape is embedded inside the substrate 1, as shown in FIG. 2(d). is obtained.

This becomes an optical waveguide.

The T optical waveguide obtained in this example is compared with the conventional optical waveguide having a semicircular −r plane shape. The coupling efficiency is high during the process, and since the dimensional waveguide is embedded inside the substrate, it is less susceptible to scattering caused by scratches, dust, etc. on the substrate surface.
<, is superior in that the original propagation loss is small.

An embodiment of the present invention has been described above. Here, the first
Although silver ions are used as the metal ions, thallium ions, lithium ions, etc. may also be used. Alternatively, a dry process may be used as a method for infiltrating the first ions into the first substrate, and a wet process may be used in which the metal ions in the molten salt are infiltrated into the substrate. Furthermore, when carrying out the second process, which is the embedding process, the IJ cum ions are infiltrated into the substrate. Any metal ion that is also small in size will suffice. l? Although a mixture of sodium nitrate and clay is used as the ion absorption layer, a metal thin film made of alumium or the like may also be used.

Finally, the characteristics of the optical waveguide manufactured using the manufacturing method according to the present invention are as follows: an optical waveguide with a substantially circular cross-section can be obtained; it has good coupling efficiency when connected to a nine-point fiber; The optical waveguide is formed inside the substrate, has low optical waveguide loss, and is thermally and mechanically stable.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a dimensional waveguide made by the conventional method;
Figures (a) to (d) are process diagrams showing one example of the method for manufacturing an optical waveguide according to the present invention. 101...Substrate, 102...Optical waveguide, 1...Substrate, 2...Diffusion prevention layer, 3
... Thin film layer of silk, 4 ... Positive electrode, 5.
...Cathode, 6...Heater, 7゜7'・
...High refractive index section, 8... Diffusion source, 9...
... Ion absorption layer, 10 ... Anode plate, 11
...Cathode plate. 'J-z (I

Claims (1)

[Claims] a first step of selectively infiltrating into a highly optically transparent substrate a first metal ion that increases the refractive index of the substrate when infiltrated into the iron substrate to form the entire high refractive index portion; By infiltrating the substrate with second metal ions, the refractive index of the substrate becomes smaller than the refractive index of the high refractive index portion. a second step of embedding the second metal ion into the inside of the substrate, the second metal ion gold plate is placed on the surface of the substrate that has undergone the first step on the side where the high refractive index portion is formed; the second metal ion diffusion source made of a mixture of salt and clay, heating the diffusion source and the substrate, melting the salt, and applying an electric field. of metal ions permeate into the substrate to form the second
1. A method for manufacturing an optical waveguide, comprising the steps of: