JPH01261243A - Production of optical waveguide - Google Patents

Abstract

PURPOSE:To effectively prevent occurrence of crack in mask boundary part in cooling treatment of a glass substrate and contrive high accuracy, by using a Tl-containing mixed salt as a melted salt in production of an optical waveguide. CONSTITUTION:A mixed salt consisting of 10-80mol% Tl2SO4 and/or 0-45mol% and 5-90mol% either one of HgSO4, NiSO4 or CdSO4 is melted to provide a melted salt. Then surface part corresponding to required optical waveguide is brought into contact with the above-mentioned melted salt containing Tl and Tl ion is diffused into the interior of glass and part having high reflex index is formed to produce the optical waveguide.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an optical waveguide manufacturing method for forming an optical waveguide in a glass body, and in particular, to an optimum temperature for ion exchange and smooth cooling of the glass body after ion exchange. This invention relates to a first method for fabricating an optical waveguide.

(Prior art) In the conventional manufacturing method of this type, a glass substrate for forming an optical waveguide is immersed in a molten salt composed of a compound containing exchanged ions, such as T°CNO, etc., to form an optical waveguide. TJ2 ions are diffused into the portion, and this diffused portion has a higher refractive index than the glass substrate, forming an optical waveguide.

Another conventional manufacturing method is disclosed in Japanese Patent Publication No. 18924/1983. Another conventional manufacturing method is to bring molten salt containing thallium into contact with a long and narrow surface portion of the glass substrate surface containing alkali metal ions corresponding to the required optical waveguide, thereby diffusing thallium ions into the glass substrate. In the method for manufacturing a glass body having an optical waveguide with a high refractive index, Tl1 as the molten salt
The composition uses a mixed salt consisting of 10 to 80 mol% of 2504, 0 to 45 mol% of one or both of Na2SO4 and 2SO4, and 5 to 75 mol% of ZnSO4.

The glass substrate must contain alkali metal ions, and the total amount of one or both of Na2O and NaO is at least 1 mol%, preferably 2 mol% or more, Ordinary optical glass satisfies most of the conditions, and commercially available optical glasses can be used as the substrate material.

The elongated surface portion of the surface of the glass substrate corresponding to the required optical waveguide to be brought into contact with the thallium-containing salt is formed, for example, by providing on the substrate a mask having a negative pattern of the optical circuit. The elongated surface of the substrate is brought into contact with a molten salt containing thallium to diffuse thallium ions into the glass, thereby causing ion exchange between the thallium ions in the salt and the alkali metal ions in the substrate. A glass body (optical circuit) having a thallium-rich optical waveguide with a high refractive index inside the portion is obtained.

[Problem to be solved by the invention]

Since the conventional optical waveguide manufacturing method was configured as described above, a compound containing exchanged ions (for example, TJI NO3
etc.) In the case of a molten salt composed of a single substance, it has high performance in the effective temperature range for ion exchange and is easily decomposed (for example, the melting point of TJ2 NO3 is around 350°C), so ion exchange cannot be performed under optimal conditions. There was a problem with this. In addition, in the other conventional optical waveguide manufacturing method, the molten salt is
Since it is composed of a mixed salt of O4 and ZnSO4, the liquid viscosity of the molten salt is high, and there is a problem that cracks occur at the mask boundary surface when the glass substrate (especially in the case of Pyrex glass, etc.) is cooled. Ta.

This invention was made to solve the above problems,
An object of the present invention is to obtain a method for manufacturing an optical waveguide that can perform ion exchange under optimal temperature conditions and can manufacture an optical waveguide without causing cracks on the mask boundary surface, etc. when cooling the glass substrate after ion exchange. do.

(Means for Solving the Problems) In the optical waveguide manufacturing method according to the present invention, Tl12SOa is IO to 80 mol%, Na2SO4 and SO4
The total of one or both of them is 0 to 45 mol%, H
Either gSO4, NiSO4 or CdSO4 is 5
to form a molten salt with a mixed salt consisting of 90 mol%,
A surface portion of the glass substrate containing alkali metal ions corresponding to the required optical waveguide is brought into contact with this molten salt, and the thallium ions in the molten salt are diffused into the glass from this contacted surface portion to create a high refractive index. This method manufactures an optical waveguide using the high refractive index portion as a waveguide.

(Function) The molten salt of the present invention maintains a stable mixed salt liquid state under the optimum temperature conditions for glass ion exchange, and performs effective ion exchange. By suppressing the adhesion of molten salt to the surface of the glass substrate, especially at the boundary between the optical waveguide corresponding portion and the mask, the glass body cooling process is performed smoothly, and no cracks are generated at the mask boundary. High-precision optical waveguides can be manufactured using this molten salt.

(Example) Hereinafter, an example of the present invention will be explained based on Fig. 1 and Fig. 2. Fig. 1 (A), (B), (C),
(D) is a process diagram showing each manufacturing process of the optical waveguide, and FIG. 2 is a transmission type interference micrograph of the surface of the glass substrate.

In each of the above figures, the optical waveguide manufacturing method according to this example is as follows:
A mixed salt containing 50 mol% of 7422504 and 50 mol% of HgSO4 is mixed to form a molten salt, the molten salt is heated to 500° to reach the optimum temperature for ion exchange, and a glass substrate containing alkali metal ions is prepared. (1) Openings (21) corresponding to the required optical waveguides on the surface of the molten salt heated above
(3), and the thallium ions in the molten salt (3) are transferred to the glass substrate (3) through the contact opening (21).
diffused inside the glass to form a part with a high refractive index.
The structure is such that this portion with a high refractive index is manufactured as an optical waveguide (12).

Next, the optical waveguide manufacturing process of this embodiment method based on the above configuration will be explained in detail. First, a mass part (2) for preventing ion exchange is formed on the entire surface of the glass substrate (1) by sputtering (FIG. 1(A)). The mask portion (2) vaporized on the entire surface of the glass substrate (1) is patterned with a desired optical waveguide pattern using well-known light exposure technology, and the patterned optical waveguide pattern is etched into openings using dry etching technology. (21) (FIG. 1(B)).

Furthermore, 50 mol% each of Tj22So4 and HgSO4
Molten salt (3) formed by mixing at a ratio of 500℃
The temperature rises to This molten salt (3) becomes a transparent liquid with a slightly brownish color.

This heated molten salt (3) is placed in a container (4), and the glass substrate (1) in which the opening (21) is formed is immersed in the molten salt (3), and electrolysis E is applied (the second Figure 1 (C)
). Due to this electrolysis, thallium ions in the molten salt (3) are diffused into the glass of the glass substrate (1) through the opening (21) and become a portion with a high refractive index, and this portion becomes an optical waveguide (12). (Figure 1 (C). The time for immersing the glass substrate (1) in the molten salt (3) depends on the desired characteristics of the optical waveguide (12), the physical properties of the glass substrate (1) (for example, BK-7, (low melting point glass, etc.), and will be set appropriately according to its characteristics.

Next, the glass substrate (1) that has been subjected to the ion exchange is pulled up from the molten salt (3) and slowly cooled. During this pulling, since the viscosity of the molten salt (3) is extremely low, adhesion of the molten salt (3) to the surface of the glass substrate (1) is minimized. This molten salt (3) is attached to the glass substrate (1
) Since it is less likely to adhere to the surface, the stress applied to the glass substrate (3) during the slow cooling process can be reduced.

Further, the glass substrate cooled by slow cooling is washed with water, and then the mask portion (2) is removed by etching (FIG. 1(D)).

FIG. 2 shows interference micrographs of the optical waveguide (12) manufactured through each of the above steps observed with a transmission type interference microscope. In the same figure, a high refractive index region is formed over a width of 40 to 50 μm, and the central part 2 of this high refractive index region
It is confirmed that 0 μm is formed as a part with a particularly high refractive index. Note that in the figure, the vertical fringes are interference fringes.

In the case of this example, the optical waveguide (12) is connected to the glass substrate (1
) Applicable to optical waveguide type sensors etc. that need to be formed on the surface.

In the above example, the optical waveguide (12) was formed on the surface of the glass substrate (1), but after the final step of the above example, the optical waveguide, which is a high refractive index portion, was further formed by an electric field application ion exchange method. (12) can also be configured such that an optical waveguide having a circular refractive index profile is formed inside the glass substrate (1). In this case, it has the effect of reducing the loss in the waveguide characteristics of the optical waveguide.

Further, in the above embodiment, the temperature of the molten salt is raised to 500° C. to perform ion exchange, but the temperature can be set to an optimum temperature (for example, 400 to 600° C.) depending on the desired characteristics of the optical waveguide.

Furthermore, in the above example, Na2SO4 and K2
The sum of one or both of SO4 was 0 mol% to form a molten salt, but J rx 2504 was IQ to 8
0 mol%, one or both of Na2SO4 and K2SO4 is O to 45 mol%, Hg5o4, )115
A molten salt can be formed by any combination of CdSO4 and CdSO4 as long as it is a mixed salt containing 5 to 90 mol%. The aspect of this combination is selectively set as appropriate based on the desired characteristics of the optical waveguide and the characteristics of the glass substrate.

(Effects of the Invention) As explained above, the present invention has designed a unique structure for the ion exchange molten salt that forms the optical waveguide on the glass substrate. When pulling up the glass substrate after replacement, it is possible to minimize the adhesion of molten salt to the surface of the glass substrate, especially at the boundary between the optical waveguide corresponding part and the mask, which effectively prevents cracks from forming at the mask boundary during the glass substrate cooling process. This has the effect that a highly accurate optical waveguide can be manufactured by preventing the above.

[Brief explanation of the drawing]

FIG. 1 is a mode diagram showing the manufacturing process of an optical waveguide manufacturing method according to an embodiment of the present invention, FIG. 1(A) is an explanatory diagram of the process of vapor depositing a mask on a glass substrate, and FIG. A diagram of the patterning/dry etching process for forming openings corresponding to the wave path pattern, Figure 1 (C) is an explanatory diagram of the ion exchange process, Figure 1 (D) is an explanatory diagram of the mask part removal process, and Figure 2 is an illustration of the interference process. This is an interference micrograph of the crystal structure of an optical waveguide represented by stripes. (1) Glass substrate, (2): Mask part, (3): Molten salt, (4): Container, (11): Fixing part, (12): Optical waveguide, (21)
: opening, E; electric field. Note that the same reference numerals in the figures indicate the same or equivalent parts. Patent applicant: Shimadzu Corporation π6 51, Shiha Ua

Claims (1)

[Claims] A molten salt containing thallium is brought into contact with a portion of the surface of the glass substrate containing alkali metal ions that corresponds to the desired optical waveguide, and the thallium ions are diffused into the glass, forming a portion with a high refractive index and forming a light guide. In the method for manufacturing an optical waveguide, Tl is used as the molten salt.
_2SO_4 is 10 to 80 mol%, Na_2SO_
A method for manufacturing an optical waveguide, characterized in that a mixed salt is used in which a total of one or both of HgSO_4 and K_2SO_4 is 0 to 45 mol%, and any of HgSO_4, NiSO_4, or CdSO_4 is 5 to 90 mol%.