JPS6319630A - Optical switch - Google Patents

Abstract

PURPOSE:To improve quenching characteristics and to facilitate manufacture by providing a refractive index variation part on at least one of both sides of an optical branching part. CONSTITUTION:When the refractive index of the refractive index variation part 4 is decreased, a light wave incident on the optical branching part 5 from an optical waveguide 2 or 3 travels straight and is projected on an optical waveguide 8 or 7. The optical branching part 5 has the refractive index variation part 4, so the light wave incident from the optical waveguide 2 or 3 advances in a beeline without spreading in this area nor leaking to the optical waveguides 7 and 8, so the quenching characteristics are improved. Further, when the light wave incident from the optical waveguide 2 or 3 is reflected by the optical branching part 5 and projected on the optical waveguide 7 or 8, deterioration in quenching ratio is prevented by increasing the width of the optical branching part 4 and the width of the refractive index variation part 6. Consequently, an optical branching structure is obtained which has an excellent quenching ratio and is easily manufactured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crossing type optical switch using at least two optical waveguides, and particularly relates to an optical branching section that can obtain a good extinction ratio and is easy to manufacture. Regarding structure.

[Conventional technology]

Conventional cross-type optical switches provide a refractive index changing portion in the center of the optical branching section, as described in Inoue et al., Proceedings of the 1985 IEICE Semiconductor and Materials Division National Conference, 57-4. When the refractive index was lowered, light was reflected, and when the refractive index remained unchanged, light was transmitted.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, when a light wave enters the light branching part, the refractive index of the refractive index changing part provided at the center of the light branching part is controlled to achieve a transmission/reflection state of the light wave. When the optical waveguide has a width of only 1 μm to several μm, such as a single-mode waveguide, the central part must be manufactured with a width of about 0.2 to 1 μm (it is extremely difficult to manufacture it with high precision). ), and at this time, if the width of the refractive index changing part is narrow, the light waves will not be completely reflected and some of the light waves will leak into the optical waveguide on the side of the optical path where it is not desired. Extinction ratio deteriorates. Furthermore, in order to increase the width of the refractive index changing section, it is necessary to increase the width of the optical branching section, and there is also the problem that the extinction ratio deteriorates at that time as well.

The purpose of the present invention is to
The object of the present invention is to realize a cross-type optical switch that has good extinction characteristics and is easy to manufacture.

[Means for solving problems]

The above object is achieved by providing the refractive index changing section 4 in the light branching section 5, as shown in FIG.

[Effect]

When the refractive index of the refractive index changing section 4 shown in FIG. 1 is lowered, when a light wave enters the optical branching section 5 from the optical waveguide 2 or 3, the light wave travels straight and exits to the optical waveguides 8 and 7, respectively. . At this time, since the optical branching section 5 has the refractive index changing section 4, the optical wave incident from the optical waveguide 2 or 3 does not spread within this region and travels straight without leaking to the optical waveguide 7°8.
The extinction property is improved compared to the conventional type shown in the figure. Furthermore, the light wave incident from the optical waveguide 2 or 3 is reflected by the optical branching section 5,
When outputting the light to the optical waveguides 7 and 8, this is achieved by providing a refractive index changing section 6 at the center of the optical branch, as in the conventional example shown in FIG. Even if a single mode is used and the optical special wave path width is on the order of 1 μm, deterioration of the extinction ratio can be prevented by increasing the width of the optical branching section 4 and the width of the refractive index changing section 6. As a result, in the conventional example, the extinction ratio deteriorates when the light wave travels straight, but in the present invention, since the refractive index changing section 4 is provided, the extinction ratio does not deteriorate.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 3. FIG. 3 is a sectional view taken along line AA' in FIG. First, a groove 14 was formed on the surface of an n-type InP substrate 1 with a carrier density of 2×101♂]-3 using a normal etching method to form an optical waveguide. The wavelength conversion value of the bandgap energy is 1.
45 μm n-InGaAsP optical waveguide layer, 9 and n
-I n P layers 10 were sequentially formed. Then n-In
Zn was diffused into a part of the P layer 10 to form a current path 11 (which serves as a current confinement layer for the injected current).
Finally, Cr--Au was deposited to provide electrodes 13.15, and Au-Ge-Ni was deposited to provide electrodes 12, completing the optical switch.

Light with a wavelength of 1.55 μm was incident on the optical waveguide 2 of this optical switch, and the intensity of the light emitted from the optical waveguides 7 and 8 was measured to examine the optical switching characteristics.

First, when no current was applied to any electrode, light waves were mainly emitted from the optical waveguide 8, but also slightly emitted from the optical waveguide 7, and the ratio of the two light intensities, that is, the erasure ratio, was 15 dB. Here, when a current is applied to the electrode 13 corresponding to the refractive index changing part 4 to lower the refractive index of the refractive index changing part 4, the extinction ratio is improved to 23 ciB. - When a current was applied only to the refractive index changing portion 6, the refractive index of the refractive index changing portion 6 was lowered, and the light wave was mainly emitted from the leading waveguide 7, an optical path switching occurred, and the switching characteristics were confirmed.

The extinction ratio at this time was 21 dB.

In this example, the refractive index change phenomenon that occurs when a current is injected into a semiconductor material is used to change the refractive index, but it is also possible to use a refractive index change induced by a voltage such as an electro-optic effect. Any technique used to effect the rate change will have a similar effect. In addition, the materials include TnP type, GaAs
As well as other semiconductor materials - LiNb
It goes without saying that any material that can cause a change in refractive index can be used, such as oxides such as Os.

〔Effect of the invention〕

According to the present invention, a practical optical switch with a large extinction ratio can be provided without using extremely fine processing technology, making it easy to construct an optical transmission/communication system, and thus improving its industrial effects. is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline and an embodiment of the present invention, FIG. 2 is a diagram showing an outline of a conventional example, and FIG. 3 is an A-A diagram in FIG. 1.
'This is a cross-sectional view.

Claims (1)

[Claims] 1. In an optical switch that switches the optical path by changing the refractive index of a part of the optical branching part where the optical waveguides formed on the substrate intersect, the refractive index changing part is placed on at least one of both sides of the optical branching part. An optical switch characterized by the following: