JPS60191207A - Optical waveguide element - Google Patents

Abstract

PURPOSE:To obtain an optical waveguide element having a good operating characteristic, less propagation loss of light and excellent practicability by constituting the optical waveguide element of a line waveguide part consisting of a specific crystal structure and an element waveguide part consisting of a thin film having the other specific crystal structure. CONSTITUTION:A powder mixture composed of the oxides of Pb, La, Zr and Ti is deposited by high-frequency sputtering on a quartz glass substrate 11 and is heat-treated to form a thin film 12 having a pyrochlore type crystal structure. Such film 12 is partially annealed by scanning of an IR laser 13 to form a thin film 14 having a perovskite type structure. A pattern 21 of a total reflection type switch waveguide is formed by etching on the thin film in such a way that the perovskite thin film part 14 serves as an element part to provided electrodes 22. Incident light 23 changes from transparent light 24 to reflected light 25 when a voltage is impressed between the electrodes 22. The optical waveguide element having a good operating characteristic, less propagation loss of light and excellent practicability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical waveguide device applied to optical integrated circuits, original information processing, and the like.

Conventional configurations and their problems Research on optical waveguide devices has been conducted as optoelectronics is expected to play a role in the advanced information society. There are two main types of structures conventionally used as optical waveguide devices. One is to create a waveguide that becomes an optical element by diffusing or implanting an arbitrary element into a dielectric bulk that has a physical optical effect. For example, an optical waveguide element in which a waveguide is formed by diffusing titanium into LiNbOs, which is an electro-optic crystal, has been most widely used. However, the problem with this cylindrical structure is that the bulk materials from which the diffusion waveguide can be fabricated are limited, and materials with sufficient physical optical effects, such as electro-optic effects, cannot be used. However, it lacked practicality in terms of device operation. For example, in a total reflection type optical waveguide device using titanium-diffused LINbOs, the operating voltage is around eoV, and practical operation that can be directly connected to TTL etc. is not possible, so there is a desire to reduce the operating voltage. Ta.

Another structure is to grow a dielectric thin film having a physical optical effect on an arbitrary substrate to produce a waveguide that becomes an optical element. In this case, if a material with a sufficiently large physical optical effect, such as an electro-optical effect, is selected as the dielectric thin film, good device operation can be achieved. One of the most promising thin film materials of this type has been known to have a perovskite crystal structure represented by the chemical formula ABO3. Peropskite type I old is characterized by its superior physical optical effects, such as electro-optical effects, due to its structure. However, growing thin films of this kind of material is not easy;
It is necessary to set strict growth conditions, and deviations in the growth conditions often result in the contamination of crystals with a pyrochlore type crystal structure (chemical formula A2B206) that has no physical optical effect.

Even if a thin film with a single perovskite structure could be made, it is difficult to obtain one with the excellent light transmittance necessary for use as a waveguide element. The reason for this is not clear, but it is probably due to the complex crystal structure and the relationship between multiple components. In the end, waveguide devices using thin films with a perovskite structure have excellent device operation functions, but have the disadvantage of large light propagation loss, which has been a problem in practical use.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide an optical waveguide device which has good operating characteristics and low optical propagation loss, and is highly practical.

Structure of the Invention The optical waveguide device of the present invention is composed of a line waveguide portion made of a thin film having a pyrochlore crystal structure and an element waveguide portion made of a thin film having a perovskite crystal structure. Conventionally, various thin film devices have been produced using perovskite materials that have a large physical optical effect. It was fabricated by converting a structured thin film into a perovskite structure by annealing. In this way, the conditions for growing a thin film with a perovskite structure are very strict, and the stability of the film quality is poor due to fluctuations in each condition, resulting in non-uniformity and non-reproducibility of properties, as well as low propagation loss, which is important for elements. was difficult to obtain. Since the pyrochlore structure has no physical optical effect at all, sufficient annealing is performed to prevent it from remaining in the crystal structure of the thin film as much as possible. The present inventors have focused on the low propagation loss and ease of growth of this pyrochlore structured thin film, and have used a thin film with this structure in the line waveguide section, which occupies most of the leading waveguide element. The present invention was made based on the discovery that an optical waveguide device having excellent operating characteristics and propagation loss can be optimally configured by using a thin film having a perovskite structure.

1) In the optical waveguide device of the present invention, a device waveguide portion of a thin film having a perovskite crystal structure is obtained by first annealing a part of a thin film having a pyrochlore crystal structure grown on the entire surface of a substrate. As mentioned above, the pyrochlore type thin film is
Since it is very easy to grow, the optical waveguide device with the above configuration can be easily grown. The present inventors have confirmed that the easiest method is to first apply a pyrochlore type thin film to the entire surface of the substrate and then partially anneal it to obtain a perovskite type thin film. In this case, a simple method for annealing is to irradiate a part of the thin film with heating light from an infrared lamp or infrared laser using, for example, a metal mask. For this purpose, the present invention will be explained below with reference to specific examples. Lead, lantern, zirco/,
Titanium oxide powder was prepared in a molar ratio of lead (pb) to lanthanum (La) to zircon (Zr) to titanium (Ti).
) with a ratio of 9:1:5:3 as a target, a thin film is grown on a quartz glass substrate by high-frequency sputtering. 4,000 polycrystalline thin films with a pyrochlore type crystal structure were grown under conditions of a substrate temperature of 400°C and a growth rate of 60 people/min.
It's a personal thing.

The crystal structure was confirmed by X-ray diffraction, and no optical effect was observed, and the optical propagation loss was less than 1 dB/cn+ for a wavelength of Q, 633/Jm. In FIG. 1, a pyrochlore thin film 12 on a quartz glass 11 is partially annealed by scanning with an infrared laser beam 13 to obtain an element portion 14 having a perovskite structure. The X-ray diffraction image of this minute part shows a perovskite structure, and the electro-optic effect has a Kerr constant R = I x 1.0'', 6
(m/V).

As shown in FIG. 2, a total reflection type switch waveguide pattern 21 was formed on this thin film by etching so that the perovskite thin film portion 14 would become an element portion, and an electrode 22 was formed. By applying a voltage between the electrodes 22, the incident light 23
A total internal reflection type optical switch element that switches from transmitted light 24 to reflected light 25 was realized. The operating voltage was 3 dB due to the large electro-optic effect, which is extremely low compared to conventional total reflection switches, and the optical loss was only slightly observed in the element section, and was as small as 2 dB overall.

It was also confirmed that if the boundary between the waveguide between the line section and the element section is tapered as shown in FIG. 2, loss due to boundary reflection is reduced.

Effects of the Invention As described above, the optical waveguide device of the present invention, which has achieved high efficiency operating characteristics and low optical loss, is excellent in practicality and solves the conventional problems, and the industrial value of the present invention is is expensive.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing how an element part of an optical waveguide device according to an embodiment of the present invention is obtained, and FIG. 2 is a 4° view of a total reflection type optical waveguide device according to an embodiment of the present invention. 1... quartz glass substrate, 12...) Thin film with Irochlore type structure, 13... infrared laser beam, 1
4... thin film with perovskite structure, 21 waveguide pattern, 22... electrode, 23 incident light, 24...
Transmitted light, 25...Reflected light.

Claims (2)

[Claims] (1) An optical waveguide device comprising a line waveguide portion made of a thin film having a pyrochlore crystal structure and an element waveguide portion made of a thin film having a perovskite crystal structure. (2) The device waveguide section made of a thin film having a perovskite crystal structure is obtained by annealing a part of a thin film having a pyrochlore crystal structure that is first grown on the entire surface of a substrate. The optical waveguide device according to scope 1.