JPS62297825A - Optical switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical component for optical communication, and in particular has a large extinction ratio.
This invention relates to an optical switch with low loss.

[Conventional technology]

In an optical switch having a structure in which two optical waveguides intersect, it may be desirable for the intersection angle to be close to 90° in terms of miniaturization. This is particularly required when a large number of optical switches are arranged in a matrix.

An optical switch configured with a conventional optical multiplexing circuit to deal with this problem is, for example, Applied Optics 6. No,
12 (1977) pp. 3223-3229 (A
ppl, Opt, Vol, 16, No, 1
2 (1977) pp. 3223-3229).

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, the coupling efficiency between two optical waveguides in the optical multiplexing/demultiplexing section has not been considered.

An object of the present invention is to provide an optical switch that has a high coupling efficiency in an optical multiplexing section, resulting in a large extinction ratio, a large crossing angle of optical waveguides, and a low insertion loss.

[Means for solving problems]

The above purpose is to connect one of the input side optical waveguides (for example 6) and the output side optical waveguide (for example 10) with a bypass optical waveguide (7) as shown in FIG. , 14, 15, 16) are provided with refractive index changing portions,
This is achieved by adjusting the refractive index of the portion.

This adjustment of the refractive index is usually done by increasing the refractive index of the optical waveguide that transmits light, and leaving the refractive index of the optical waveguide that does not transmit unchanged or decreasing it, but depending on the structure of the optical waveguide, various The mode of refractive index change can be considered.

Note that such adjustment of the refractive index can be carried out using well-known techniques such as applying an electric field to the portion, injecting a current, or irradiating the portion with light.

That is, by such a technique, for example, the refractive index of the refractive index changing portion can be increased.

Here, the coupling region refers to a crossing point of an optical waveguide and/or a region near it.

Note that FIG. 1 is a plan view showing the planar arrangement of the optical switch.

[Effect]

In the optical waveguide coupling region of the optical multiplexing/demultiplexing section, the coupling section is configured such that only one optical waveguide among the input optical waveguides is coupled to one optical waveguide within the output optical waveguide. Decrease the refractive index of a portion unnecessary for coupling, or increase the refractive index of a part of the optical waveguide that serves as a coupling path. This improves confinement in the coupling path between the input optical waveguide and the output optical waveguide, reducing leakage to other optical waveguides. The coupling efficiency is increased, and switching with a large extinction ratio becomes possible.

The intersection angle of the optical waveguides may be large.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

An optical waveguide consisting of a core region and a cladding region is made of InGaA.
This is an optical switch that has two input terminals and two output terminals composed of sP and other peripheral InP. The input optical waveguides 6 and 12 are connected to the output optical waveguides 10 and 17, and the X-type optical branching circuit 20 and the Y-type optical branching circuit 18 and Y
The optical multiplexing circuit 19 consists of nine optical switches. The optical coupling portions of the Y-type optical multiplexing/demultiplexing circuits 18 and 19 are provided with regions 13, 14, and 15° 16 in which the refractive index decreases. As a method for lowering the refractive index, there is, for example, a method of injecting carriers. Now, when light 1 enters from the input optical waveguide 6 and is emitted as output light 5 to the output optical waveguide 10, the refractive index of the region 13°15 is lowered. At this time, the optical waveguides 6°7.10 are selectively coupled, and the light waves 5 are efficiently emitted. Furthermore, when guiding the emitted light 4 to the output side optical waveguide 17, by lowering the refractive index of the region 14, the optical waveguides 6, 8, and 17 are selectively coupled, and the light wave 4 is efficiently emitted. When the light wave 11 enters from the input optical waveguide 12 and exits to the output optical waveguide 10, the refractive index of the region 16 is lowered, and the optical waveguide 12°9.10 can be selectively coupled. Without this invention, the coupling loss between the optical waveguides in the Y-type optical multiplexing/demultiplexing circuit 18 and 19 would be 3d.
By using the present invention, what was about B
It was below B. Furthermore, since the optical waveguides are selectively and efficiently coupled according to the present invention, the extinction ratio when the optical wave 1 incident from the input optical waveguide 6 is switched to the output optical waveguides 10 and 17 is 30 d,B or more. , showed extremely good characteristics.

(2) In this embodiment, a case has been described in which the refractive index of only the optical waveguide is changed, but the same effect can be obtained even if the refractive index changing region includes the desired optical waveguide and extends over the cladding region.

(2) Furthermore, in this embodiment, a method of injecting carriers was used as a method of changing the refractive index, but the same effect can be obtained by applying an electric field and changing the refractive index by the electro-optic effect. A similar effect can also be obtained by irradiating the refractive index changing portion with light.

FIG. 2 is a sectional view taken along line A-A' or B-B' in FIG. 1, and FIG. (b) shows an example of light irradiation.

In FIG. 2(a), an electrode 30 is formed on the refractive index changing portions 13, 15, 16, and 18 formed on the substrate and on the back surface of the substrate, and a well-known power source (not shown) is connected to this. By applying an electric field or injecting a current, the refractive index of the portion is changed.

In addition, in FIG. 2(b), the refractive index of the refractive index changing portions 13, 15, 16, and 18 formed on the substrate is changed by irradiating light using a semiconductor laser. can be done.

In this embodiment, the substrate is GaAs or InP when applying an electric field or when injecting light.

LiNb0 is used, and n-GaAs is used for current injection.

n-InP was used. When the substrate was GaAs, n-GaAs was used as the optical waveguide, and n+GaAs was used as the refractive index changing portion. The well-known crystal growth method and photoetching were used as the formation method. others,
Well-known techniques relating to optical waveguides are applicable to the implementation of the present invention.

〔Effect of the invention〕

According to the present invention, the loss in the optical multiplexing/demultiplexing circuit constituting the optical switch becomes extremely small and the extinction ratio becomes large.
The intensity of the emitted optical signal can be maintained high, and the S/N ratio can be increased.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of an embodiment of the present invention, Figures 2 (a), (
b) is a sectional view taken along line A-A' or line B-B' in FIG. 1, respectively; 1.11...Incoming light, 4,5...Outgoing light, 6.7,
8, 9, 10, 12.17... Leading wave path, 13.14
, 15, 16... refractive index change region, 18.19...
Y-type optical multiplexing/demultiplexing circuit, 20...X-type optical branching circuit. ．． 74 Agent Patent Attorney Katsuo Ogawa ゛ゝ-' 7th Hard Hatan／／－－－－－－－、－－－－－One-man power...－－－
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Claims (1)

[Claims] An optical switch that is composed of one, two or more optical waveguides, has at least one crossing point or coupling region, and has two or more input ends and two or more output ends. A bypass optical waveguide is provided to connect one input side optical waveguide and one output side optical waveguide at the intersection point, and a refractive index changing portion is provided in the optical waveguide at the intersection area of the optical waveguide and the bypass optical waveguide. An optical switch characterized by: 2. The optical switch according to claim 1, wherein the refractive index change is caused by carrier injection.