JPS6161081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a planar optical waveguide used in optical communication or optical information processing.

Planar optical waveguides are used as semiconductor light sources in the field of optical communication.
It is an essential element in realizing repeaters, transmitters, etc. using optical integrated circuits obtained by combining optical modulators, photodetectors, optical filters, and optical fibers. In particular, the reduction in loss of optical fibers and the extension of the lifespan of optical semiconductor devices have a great influence on the promotion of practical use of optical fiber communications, and the need for optical integrated circuits, especially planar optical waveguides, is increasing. Further, optical integrated circuits, which have been considered in the field of optical information processing, are now being considered for practical use due to the invention of various high-speed optical switches, bistable optical devices, and the like. Although there are various requirements for a planar optical waveguide used in these applications, it is especially important that the transmission loss be small and that the manufacturing process be simple and easy to manufacture.

Conventionally, various methods for manufacturing planar optical waveguides have been proposed, but the method for manufacturing planar optical waveguides with relatively low loss is a method that combines a sputtering method and a photolithography method.

Conventionally, an optical branching circuit, which is one form of a planar optical waveguide shown in FIG. 1, is manufactured by combining sputtering and photolithography as described below. A glass layer having a higher refractive index than the glass substrate is formed by sputtering on the glass substrate 11 whose surface has been sufficiently polished in the first manufacturing process. Thereafter, a portion of the sputtering layer is removed by a second process, photolithography, to create an optical branch circuit. The photolithography method used here is to apply photoresist to the glass surface of the two-layer structure, then expose the pattern of the optical branch circuit, remove the photoresist in the exposed area, and then remove the photoresist. This refers to the process of removing the removed portion of the high refractive index glass layer by etching, and then removing the remaining photoresist film to create a patterned planar optical waveguide. However, the planar waveguide manufactured by the photolithography method mentioned above is
As shown in the figure, the lateral boundary 13 of the waveguide 12 tends to be uneven, making it difficult to obtain a low-loss planar optical waveguide, and as mentioned above, the photolithography method requires a very complicated manufacturing process. It wasn't easy.

Therefore, an object of the present invention is to provide a method for manufacturing a planar optical waveguide, which allows a planar optical waveguide with low loss to be obtained through a simple manufacturing process.

According to this invention, a glass layer containing a glass material having a higher refractive index and higher volatility than the glass substrate is formed on the glass substrate, and then perpendicular to the glass substrate and having a high refractive index. Forming a low refractive index portion by locally irradiating a focused electron beam from a direction facing the high refractive index glass layer to volatilize the highly volatile glass material contained in the high refractive index glass layer; A method for manufacturing a planar optical waveguide is obtained, characterized in that a high refractive index portion sandwiched between low refractive index portions formed by electron beam irradiation is used as an optical waveguide.

Next, one embodiment of the present invention will be described using the drawings. Figure 2 shows a glass substrate made of soda borosilicate with thallium oxide diffused on the surface to increase the refractive index of the surface, 21 shows a high refractive index layer in which thallium oxide is diffused, and 22 shows a low refractive index layer. It shows the layers. A method for manufacturing a glass substrate having such a two-layer structure is described in detail in the patent "Optical Transmission Body" (Japanese Patent Publication No. 47-10455) filed by Nippon Self-Ock Co., Ltd., and will not be described here.

Figure 3 shows a method for manufacturing a planar optical waveguide by irradiating an electron beam perpendicularly to the glass substrate onto a soda borosilicate glass substrate in which thallium oxide is diffused to increase the refractive index of the surface. show. In FIG. 3, 31 is a focused electron beam, 32 is a high refractive index layer in which thallium oxide is diffused, and 33 is a low refractive index layer containing almost no thallium oxide.

When the two-layered glass substrate is irradiated with an electron beam 31, the molecular bonds of thallium oxide are broken in the irradiated portion by the electron beam. When the molecular bonds are broken, thallium oxide easily detaches from the glass with a small amount of energy. The molecular bonds of thallium oxide are weaker than those of other glass components such as silicon oxide, so thallium oxide volatilizes best. Then, the refractive index of the part where thallium oxide has volatilized decreases. By moving the irradiation position of the electron beam along the irradiation section 34 in FIG. 3, a high refractive index section 35 surrounded by low refractive index grooves is obtained. Here, since the position where the electron beam is irradiated was moved so as to obtain an optical branch circuit, the high refractive index section 35 becomes an optical waveguide section of the optical branch circuit.

In the above embodiment, the electron beam irradiation position was moved to obtain an optical branch circuit, but since the electron beam irradiation position can be moved arbitrarily, it is not limited to optical branch circuits, and can be used to create optical branch circuits with different patterns. It is clear that it can also be applied to optical circuits.

In the above embodiment, soda borosilicate glass was used as the base glass and thallium oxide was used as the volatile component, but cesium oxide or phosphorus oxide may be used as the volatile component. In the above example, the high refractive index layer on the base glass was formed by ion diffusion, but a quartz glass film containing a mixture of germalium oxide, phosphorus oxide, etc. was deposited on the glass base by sputtering or chemical vapor deposition. A two-layer structure may also be used.

Finally, the advantage of the present invention is that a low-loss planar light guide can be obtained through a simple manufacturing process.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a planar optical waveguide made by a conventional manufacturing method, FIG. 2 is a perspective view of a two-layer glass substrate used in the present invention, and FIG. 3 is a planar optical waveguide according to the present invention. FIG. 11 is a glass substrate, 12 is a waveguide section, 13 is a lateral boundary of the waveguide, 14 is an incident light, 15 is an output light, 21 is a high refractive index layer in which thallium oxide is diffused, and 22 is a low refractive index soda boro. A silicate glass substrate, 31 an electron beam, 32 a high refractive index layer,
33 is a low refractive index layer, 34 is an irradiation section which is a portion whose refractive index is lowered by the electron beam, and 35 is an optical waveguide section.

Claims (1)

[Scope of Claims] 1. A glass layer containing a glass material having a higher refractive index and higher volatility than the glass substrate is formed on a glass substrate, and then a glass layer containing a glass material having a higher refractive index and higher volatility than the glass substrate is formed perpendicular to the glass layer having a high refractive index. A low refractive index portion is formed by locally irradiating a focused electron beam from a direction to volatilize the highly volatile glass material contained in the high refractive index glass layer, and forming the low refractive index portion by electron beam irradiation. 1. A method for manufacturing a planar optical waveguide, characterized in that a high refractive index portion sandwiched between low refractive index portions is used as an optical waveguide. 2. The method of manufacturing a planar optical waveguide according to claim 1, wherein the glass substrate is soda borosilicate glass, and the glass substrate is ion-exchanged with thallium oxide to form a high refractive index glass layer.