JPH065350B2 - Total reflection type optical switch - Google Patents

Description

TECHNICAL FIELD The present invention relates to a total reflection type optical switch that electrically controls the traveling direction of light propagating in an optical waveguide.

[Conventional technology]

Conventionally, as an optical switch of this type, an electrode is provided in a crossed waveguide, and a region with a low refractive index is electrically generated and guided so as to block the optical path of the guided light along the center line of the crossing. Some types change the optical path by totally reflecting the wave light, and this type of optical switch is characterized by its simple structure and extremely small size.

FIG. 4 is a configuration diagram showing the configuration of this type of optical switch.

Two linear waveguides 1a- ▲ ▼ and 1b- ▲ are formed on the substrate 1.
And ▼ are formed so as to intersect at an intersection 3, and an electrode 4 is provided at the intersection 2 along the longitudinal direction thereof.

In this type of optical switch, when no voltage is applied, 1
The light input to a or 1b is ▲ ▼ or ▲ ▼
1a so that the cross state output from
An intersection angle φ formed by- ▲ ▼ and 1b- ▲ ▼ is set.

When a voltage is applied to the electrode 4, the refractive index of a part of the intersection 2 is lowered to totally reflect the light, thereby outputting the light input from 1a or 1b to ▲ ▼ or ▲ ▼. ) The state can be obtained.

However, it is difficult to obtain good crosstalk in the crossed state, and it is necessary to set the crossing angle φ to 8 ° or more in order to obtain good crosstalk.

However, when the crossing angle φ is increased, there is a drawback that the operating voltage is increased because the angle of incidence on the crossing portion 2 which lowers the refractive index is increased.

[Problems to be solved by the invention]

Therefore, it is difficult for the optical switch having the above configuration to reduce crosstalk in the cross state.

As a means to solve this, the refractive index at the intersection was increased.
Although there is a 2Δn type structure, this structure has a problem that when the crossing angle is small, the mode interference effect becomes large and the switching function is not sufficiently exhibited.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a waveguide type optical switch that reduces crosstalk in a cross state.

[Means for solving problems]

In the total reflection type optical switch according to the present invention, the two waveguides have different refractive indexes from each other, and the refractive index at the intersection is equal to or higher than that of the high refractive index waveguide. What is done is summarized.

[Action]

In the total reflection type optical switch having the above structure, when guided light is made incident on the waveguide, coupling between the two waveguides can be reduced except at the intersection.

At the intersection, the waveguide has a confining structure, and the guided light is bent in the waveguide having a small refractive index.

Therefore, crosstalk in the cross state can be reduced.

As a result, the conventional problems can be eliminated.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing a main part of an optical switch according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a substrate, on which a waveguide 14 having a high refractive index and a waveguide 15 having a low refractive index are formed so as to intersect each other at an intersection 3.

At the intersection 2 centered on the intersection 3, the waveguide 14 has a confinement structure, and the waveguide 15 has no confinement structure.

Electrodes (not shown) are provided on the crossing side of the substrate 1 along the longitudinal direction of the crossing 2.

Note that 1a and 1b are input ports, and ▲ ▼ and ▲ ▼ are output ports.

Next, the operation of the optical switch having the above configuration will be described with reference to FIG.

FIG. 2 is an explanatory diagram showing the operation of the optical switch.

As shown in FIG. 2 (a), the guided light 16 is reflected by the input port 1b.
When input to the waveguide 14, the guided light 16 produces light 17a that travels in the waveguide 15 due to the coupling between the waveguides 14 and 15, but the refractive index difference between the waveguides 14 and 15 is large as in a general directional coupler. Therefore, the light 17a is hardly generated.

At the crossing portion 2, the guided light 16 has a confining structure, so the light 16 travels with almost no diffraction.

On the output side as well, there is coupling between the waveguides 14 and 15, but since the difference in the refractive index between the waveguides 14 and 15 is large, almost no light (3) is generated as with the input side.

As shown in FIG. 2 (b), the guided light 17 is reflected by the input port 1a.
Is input to the waveguide 17, the guided light 17 produces light 16b that travels in the waveguide 14 due to the coupling between the waveguides 14 and 15,
Since the waveguides 14 and 15 have a large refractive index as in a general directional coupler, almost no light 16b is generated.

At the intersection 2, as shown by the light 18, the waveguide 14
Since the light is bent in the direction away from, even if there is diffraction, the rate of light 18 leaking into the waveguide 14 decreases.

On the output side as well, there is coupling between the waveguides 14 and 15, but since the difference in the refractive index between the waveguides 14 and 15 is large, almost no light {circle around (2)} is generated as in the input side.

FIG. 3 shows a second embodiment of the present invention.

This second embodiment is almost the same as the first embodiment, but at the intersection 2, the waveguides 14 and 15 are extended so that both the waveguide 14 and the waveguide 15 have a confinement structure. The refractive index of the crossing portion 2 is set to a value larger than that of the waveguide 14 in the overlapping region.

The operation of the second embodiment is almost the same as that of the first embodiment, but the diffraction of the light propagating through the waveguide 15 is reduced,
Crosstalk is further reduced.

Table 1 is experimental data showing a comparison between the conventional example and the second example of crosstalk.

Simulation was performed by the BPM analysis method. As a result, as shown in Table 1, the crosstalk is 7 in the conventional example.
While it was ~ 11 dB, in this second embodiment it was 9-14 dB.
Was improved by 2-3 dB.

The numerical values used in the BPM analysis method are as follows.

Substrate refractive index 2.14, light wavelength 1.3μm, waveguide width 8μm,
Crossing angle φ = 4.6 °, refractive index of waveguide 2.14 + 5 × 10 ^{-3 to} 2.14 + 7
× 10 ^-3 .

[Effect of the Invention] As is clear from the above description, according to the present invention, in the total reflection type optical switch, the two waveguides have different refractive indexes from each other, and the refractive index at the crossing portion is the refractive index. Since the configuration is the same as or higher than that of the high waveguide, the coupling between the two waveguides can be reduced except at the intersection, and the waveguide also has a confinement structure at the intersection. Moreover, in a waveguide with a small refractive index,
The guided light bends.

Therefore, an effect of reducing crosstalk can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a total reflection type optical switch according to a first embodiment of the present invention, FIG. 2 is an explanatory view showing the operation of the optical switch, and FIG. 3 is an optical switch according to the second embodiment. FIG. 4 is a configuration diagram showing a conventional optical switch. 1 ... Substrate, 2 ... Intersection, 4 ... Electrode, 14 ... Waveguide, 15
… Waveguide, φ… Crossing angle

Claims (1)

[Claims] 1. A total reflection type optical switch in which a portion capable of total reflection with a refractive index lowered by an external control signal is formed at an intersection of waveguides of an optical circuit element which intersects at least two waveguides. The total reflection type optical switch, wherein the two waveguides have different refractive indexes, and the refractive index of the intersection is equal to or higher than that of the waveguide having a high refractive index.