JP2001091776A - Production method of ion exchanged optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ion exchanged optical waveguide in which the distribution of ion concentration can be controlled with minute periods and desired distribution of refractive index can be formed, and to form a grating with a desired submicron period in an ion exchanged optical waveguide. SOLUTION: An optical waveguide is formed on a glass substrate by an ion exchange method, and the optical waveguide is locally irradiated with electron beams to move the ions and to change the ion concentration to form a part having a different refractive index. In an typical example, an optical waveguide is formed on a glass substrate by an ion exchange method, and the optical waveguide is locally and periodically irradiated with electron beams to move ions so as to periodically vary the ion concentration to form a grating. For example, a glass containing Na is used for the glass substrate, and Ag ion K ion are used as the exchanging ions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a portion having a different refractive index by changing the ion concentration by locally irradiating an electron beam on an optical waveguide formed on a glass substrate by an ion exchange method. The present invention relates to a method for manufacturing an exchangeable optical device. This technique is particularly useful for forming a grating that functions as an optical filter or the like by changing the ion concentration in a minute cycle.

[0002]

2. Description of the Related Art In a planar waveguide type optical circuit, there are an ion exchange method and a flame deposition method as typical methods for forming the optical waveguide. The ion exchange method uses a multi-component glass as a substrate and immerses it in a molten salt to form an optical waveguide by thermal ion exchange or electric field ion exchange, and is a low-temperature process (about 250 to 350 ° C.). This method has the advantage of being easy and inexpensive to manufacture. On the other hand, in the flame deposition method, an optical waveguide is formed by depositing a silica-based glass on a Si substrate, and a high-temperature process (1200 to 130
(About 0 ° C.). This method is exposed to high temperatures during the manufacturing process, so that internal stress and the like act anisotropically, the polarization dependent loss that is important in optical communication is large, the manufacturing method is complicated, and the cost increases.

Meanwhile, a grating is an extremely important technique for forming an optical circuit. This grating has a fine periodic structure formed in an optical waveguide, and is applied to various optical devices such as a wavelength filter, a reflector, and a mode converter.

[0004] In the case of a fiber grating, it is formed by utilizing the fact that the refractive index of a glass material constituting an optical fiber changes by irradiation with ultraviolet light. As a specific method, a transmission diffraction grating (phase mask) having irregularities formed on the surface of quartz glass is installed, and interference fringes of ultraviolet light are reduced by +1.
There is a method of forming by interference between the first and second order transmitted diffraction light. This method is excellent in reproducibility because the pitch of the interference fringes is の of the grating period of the phase mask. As another method, the ultraviolet light is split into two equal intensity light beams by a half mirror, and the optical paths of the two light beams are changed by a total reflection mirror arranged in parallel with each other, and cross each other on an optical fiber. Irradiation method. In this method, two light beams interfere with each other on an optical fiber, and a period Λ = λ /
A light intensity distribution of interference fringes of 2 sin θ is formed. Where λ
Is the wavelength of the ultraviolet light, and θ is the incident angle of the ultraviolet light incident on the optical fiber.

In general, in Ge-doped optical fibers, optical damage is caused by the irradiation of ultraviolet light, and the refractive index of the irradiated portion increases. Accordingly, a periodic change in the refractive index corresponding to the light intensity distribution of the interference fringes occurs in the core of the optical fiber on which the interference fringes of the ultraviolet light are formed. That is, a change in the refractive index having a constant width and period occurs in a portion irradiated with ultraviolet light, and a constant refractive index is maintained in other portions. With such a refractive index distribution, an optical filter is formed which selectively reflects only wavelength components close to the wavelength 2nΛ and transmits light of other wavelength components with a constant loss. Here, n is the average refractive index of the optical fiber core.

[0006] In the case of a planar waveguide type optical circuit, in the case of an optical waveguide formed by the flame deposition method, the core is doped with Ge, so that the grating is formed in the optical waveguide by irradiating ultraviolet light as in the case of the fiber grating. Can be formed.

[0007]

An optical waveguide formed by the flame deposition method has a large polarization dependence, and this type of planar waveguide optical circuit requires a complicated manufacturing method and is expensive. Therefore, the grating also has polarization dependence and is expensive. On the other hand, a planar waveguide type optical circuit using the ion exchange method is easy and inexpensive to manufacture, but an effective method for accurately manufacturing a grating having a small period in the optical waveguide has not yet been developed.

An object of the present invention is to provide a method capable of controlling an ion concentration distribution in a fine cycle and forming a desired refractive index distribution in an ion exchange type optical waveguide.
Another object of the present invention is to provide a method capable of forming a grating in a desired submicron period on an ion-exchange type optical waveguide.

[0009]

When a glass substrate subjected to an ion exchange treatment is locally irradiated with an electron beam, ions move according to the irradiation intensity of the electron beam, irradiation time, and the like, and the ion concentration changes. The present invention is a method devised so that regions having different refractive indices can be freely formed by utilizing this phenomenon.

According to the present invention, an optical waveguide is formed on a glass substrate by an ion exchange method, and the optical waveguide is locally irradiated with an electron beam to move ions. This is a method for manufacturing an ion exchange type optical device that forms As a typical example, by forming an optical waveguide on a glass substrate by an ion exchange method and irradiating the optical waveguide locally and periodically with an electron beam to move ions, the ion concentration is periodically adjusted. There is a method of forming a grating by changing the value.

For example, as a glass substrate, a glass containing Na is used. An optical waveguide is formed by using Ag ions or K ions as exchange ions and exchanging the Ag ions or K ions with Na in the glass. When this optical waveguide is irradiated with an electron beam, ions move at the irradiated portion, causing a change in concentration, and as a result, the refractive index locally changes. Since the electron beam can irradiate only a minute portion as in the case of electron beam exposure, a concentration distribution of a minute period can be produced in the ion exchange type optical waveguide. By this method, a submicron period (0.1 to 1.0 μm) is used.
m) can be easily manufactured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of forming an optical waveguide may be basically the same as the conventional one. The surface of the glass substrate is covered with an ion permeation preventing mask provided with an opening of a desired waveguide pattern, and immersed in a molten salt containing ions (for example, Ag) for increasing the refractive index to diffuse ions from the opening. Thus, an ion exchange type optical waveguide is formed. A thermal ion exchange method or an electric field ion exchange method may be used. Surface type by one-stage ion exchange method may be used,
It may be configured to be embedded shallowly by the step ion exchange method.

An optical waveguide formed on a glass substrate is irradiated with an electron beam having a predetermined intensity (for example, 15 to 20 kV or more).
For example, spot irradiation on the optical waveguide or line irradiation that crosses the optical waveguide may be used. In any case, the electron beam is irradiated so as to scan for a predetermined time or at a predetermined speed with a spot diameter corresponding to the size of the region where the ion concentration is to be changed. When forming a grating, spot irradiation or line irradiation is repeated at predetermined intervals in the direction along the optical waveguide. As a result, local ion migration occurs, the ion concentration changes, portions having different refractive indexes are formed, and an ion-exchange type optical device having a grating that is a fine periodic structure in an optical waveguide can be manufactured. it can.

[0014]

[Experimental Example] Soda glass was used as a glass material, and the glass substrate was immersed in a molten salt of silver nitrate (AgNO ₃ ) at 280 ° C. for 6 hours, so that Na and Ag on the substrate surface were
Was subjected to ion exchange. This glass substrate was irradiated with an electron beam of 20 kV. Then, a BSE image (backscattered electron beam image) of the obtained glass substrate was observed. In each of the case where the electron beam was irradiated with the line and the case where the electron beam was irradiated with the spot, the electron beam-irradiated portion was discolored to black. In the BSE image, the larger the atomic number, the more the backscattering occurs.
The whole glass substrate looks whitish due to scattering from the light. Therefore, the discoloration is slightly darkened by the electron beam irradiation because the Ag concentration is reduced.

FIG. 1 shows the result of analyzing the ion concentration distribution after the irradiation of the electron beam spot on the measurement line. A in FIG.
Shows a BSE image after irradiation with an electron beam spot, and FIG. 1B shows quantitative analysis values by EDX (energy dispersive X-ray spectroscopy). Judging from A in FIG. 1, the portion affected by the irradiation of the spot of the electron beam (the portion discolored black) is between the measurement points G12 to G20. Correspondingly, according to the analysis result of FIG.
It can be seen that the g concentration is clearly reduced and the Na concentration is also slightly reduced.

From the results of this experiment, it has been proved that the ion concentration of only the irradiated portion can be selectively controlled by electron beam irradiation.

In the above embodiment, Na ion and Ag were used.
Although the ion exchange of ions has been described, the same effect is obtained in the ion exchange between Na ions and K ions.

[0018]

As described above, the present invention is a method for moving ions by irradiating the optical waveguide with an electron beam as described above. Therefore, even in the case of an ion exchange type optical waveguide, the refractive index of the optical waveguide is changed by changing the ion concentration. It is possible to manufacture an ion exchange type optical device having different portions. Further, since the ion concentration distribution can be controlled in a fine cycle and a desired refractive index distribution can be formed, a grating having a submicron cycle can be formed.

Since the present invention is a technique applicable to an ion exchange type optical waveguide, various ion exchange type optical devices can be easily manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a BSE image after electron beam irradiation and the results of ion concentration analysis.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masaru Tosho 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (72) Inventor Junko Ishizu 5-36-11 Shimbashi, Minato-ku, Tokyo F-term in Fuji Electric Chemical Co., Ltd. (reference) 2H047 LA01 PA11 PA13 PA21 PA30 QA04 TA43

Claims (4)

[Claims] 1. An optical waveguide is formed on a glass substrate by an ion exchange method, and the optical waveguide is locally irradiated with an electron beam to move ions, thereby changing the ion concentration to form a portion having a different refractive index. A method of manufacturing an ion-exchange optical device. 2. An optical waveguide is formed on a glass substrate by an ion exchange method, and the optical waveguide is locally and periodically irradiated with an electron beam to move ions, thereby changing the ion concentration periodically. A method for manufacturing an ion-exchange optical device, comprising forming a grating. 3. The method for manufacturing an ion-exchange optical device according to claim 2, wherein the grating period at which the ion concentration changes is 0.1 to 1.0 μm. 4. An optical waveguide is formed by using a glass containing Na as a glass substrate, using Ag ions or K ions as exchange ions, and exchanging the Ag ions or K ions with Na in the glass, 4. The method according to claim 1, wherein the concentration of Ag ions or K ions is locally reduced by electron beam irradiation.