JPH04350628A - Waveguide type optical switch - Google Patents

Abstract

PURPOSE:To offer the waveguide type optical switch which has small light loss in switching operation. CONSTITUTION:Optical waveguides A and B are crossed each other to form an intersection part C connecting with incidence port groups A1 and B1 and projection port groups A2 and B2, and refractive index varying means 9 and 11 are disposed at the intersection part C to reflect light which is made incident on one incident port A1 in the incidence port group to one projection port B2 in the projection port group, thus changing the optical path. In this waveguide type optical switch, side parts of the intersection part C which connects the incidence port A1 where the light is made incident and the projection port B2 where the light is reflected are formed in a curve shape. In the switching operation, the reflected light at the intersection part is easily guided to the reflection port, so crosstalk is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type optical switch, and more particularly, to a waveguide type optical switch with low optical loss during switching operation.

0002

2. Description of the Related Art Various types of waveguide type optical switches made of, for example, semiconductor materials have been proposed. Among these, a total reflection type optical switch is shown in a plan pattern diagram in FIG. In the case of this optical switch, a straight waveguide A and a straight waveguide B intersect at an intersection angle θ, forming an intersection C in a region indicated by a dotted line. These waveguides A, B
In each case, a substrate, a lower cladding layer, a core layer (waveguide layer), and an upper cladding layer are sequentially formed using, for example, a semiconductor material, and the entire upper surface thereof is covered with an insulating film.

At the intersection C, the insulating film approximately in the center of the waveguides A and B is removed to form a window 10, and for example,
An upper electrode 11 is attached by vapor depositing a conductive material. In a portion including the intersection C directly under the window 10, a Zn diffusion region in which Zn is diffused is formed, as indicated by a dotted line region 9 in the figure. This upper electrode 11, Zn diffusion region 9
and a lower electrode (not shown) formed on the back surface of the substrate, forming a refractive index changing means.

In this optical switch, when the refractive index changing means is not operated, the light incident from the input port A1 of the waveguide A and the input port B1 of the waveguide B passes through the intersection C.
The light travels straight ahead and exits from the output port A2 of the waveguide A and the output port B2 of the waveguide B, respectively. Here, when a current of a predetermined value is injected from the upper electrode 11, the window 1
In the Zn diffusion region 9 immediately below the zero point, a plasma effect and a band filling effect occur, causing a decrease in the refractive index. It is formed.

[0005] Therefore, for example, light from the input port A1 is reflected at the total reflection surface that appears directly below the window 10 at the intersection C, and propagates to the output port B2. That is, by operating the refractive index changing means of the intersection C, the optical path of the light from the input port A1 is changed from the output port A2 to the output port B2 on the reflection side, and a switching operation occurs here.

[0006]

[Problems to be Solved by the Invention] In the case of the above-mentioned total reflection type optical switch, the linear waveguides A that intersect with each other
, B simply intersect at an intersection angle θ. Therefore, when the refractive index changing means is operated to form a total reflection surface, and the light from the input port A1 is reflected by this total reflection surface and the optical path is changed to the output port B2 on the reflection side, the reflected light is transferred to the output port. B2 is difficult to propagate, and the reflected light may be diffused to locations other than the waveguide, resulting in increased optical loss, ie, increased crosstalk.

SUMMARY OF THE INVENTION An object of the present invention is to provide a waveguide type optical switch which can solve the above-mentioned problems and reduce crosstalk of reflected light during switching operation.

[0008]

[Means for Solving the Problems] In order to achieve the above object, in the present invention, optical waveguides are crossed with each other to form a crossing portion connecting an input port group and an output port group, and the crossing portion A refractive index changing means is disposed in the
In the waveguide type optical switch, the light entering from one input port of the input port group can be reflected to one output port of the output port group to change the optical path. There is provided a waveguide type optical switch characterized in that at least a side portion of the output port of the intersection connecting the port and the output port on the side where light is reflected is curved.

[0009]

[Operation] At least the side of the exit port at the intersection connecting the entrance port and the exit port on the reflection side changes in a curved line, and is not a simple straight line as in the past, so the refractive index changing means is used. By this operation, the light reflected at the substantially central position of the intersection can be smoothly propagated to the output port on the reflection side, and as a result, crosstalk during switching operation is reduced.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical switch of the present invention will be described in detail below with reference to the accompanying drawings showing an embodiment of the optical switch. FIG. 1 is a schematic plan view showing a planar pattern of an optical switch of the present invention. The optical switch of the present invention has both sides C1 of the intersection C.
, C2 has a curved shape.
There is no difference from the conventional optical switch shown as .

That is, both the input ports A1 and B1 and the output ports A2 and B2 are straight waveguides. However, at the intersection C formed by intersecting the waveguides A and B, there is a side C1 connecting the input port A1 and the output port B2, and a side C1 connecting the input port B1 and the output port A.
The side portion C2 connecting between C2 and C2 is a circular arc having a predetermined radius of curvature R.

The radius of curvature R at this time is
1 , B1 and each output port A2 , B2 to the intersection C smoothly, the distance is about 5 to 10 mm. Furthermore, the both sides C1 and C2 of the intersection are not limited to the above-mentioned circular arc shapes, but may be, for example, elliptical shapes. In addition, in the optical switch of the present invention, the input port A
When light is input from 1, the output port B2 becomes the reflection side output port, but only the side C1 of the intersection connecting the input port A1 and the output port B2 is made into an arc or an ellipse, and the other side C2 is made into an arc or an ellipse. It may have a linear shape as in the conventional case. Optical loss will be reduced if both sides C1 and C2 are curved.

[0013] Input ports A1, B1, exit port A
2, B2 has a structure as shown in FIG. 2, which is a cross-sectional view taken along the line II-II in FIG. 1, and the intersection C is a cross-sectional view taken along the line III-III in FIG. The structure is as shown in 3. These structures are manufactured using, for example, semiconductors in the following manner. That is, first, on a substrate 2 made of n+ GaAs, a buffer layer 3 made of n+ GaAs with a thickness of 0.5 μm, a lower cladding layer 4 made of n+ Al0.1 Ga0.9 As with a thickness of 3.0 μm, and a lower clad layer 4 made of n+ Al0.1 Ga0.9 As are formed by MOCVD. n-GaA
A core layer 5 with a thickness of 0.9 μm consisting of n-Al0.
1 A lower cladding layer 6 of 0.8 μm thick made of Ga0.9 As, and a 0.2 μm thick lower cladding layer 6 made of n-GaAs.
m cap layers 7 are sequentially laminated.

In the case of the input port and the output port, the cap layer 7 and the upper cladding layer 6 are appropriately etched except for the waveguides A1, A2, B1, and B2. For example, in the case of light with a wavelength of 1.3 μm, the upper cladding layer 6 is
．． Etch to leave about 4 μm. Thereafter, the entire surface is covered with an insulating film 8 such as SiO2, and after polishing the lower side of the substrate 2, AuGeNi/Au is deposited thereon to form the lower electrode 1.

In the case of the intersection C, the substrate 2 is
A buffer layer 3 similar to the above, a lower cladding layer 4,
After the core layer 5, upper cladding layer 6, and cap layer 7 are laminated, Zn is diffused into the portion where the refractive index is to be changed to form a Zn diffusion region 9, and then etched in the same manner as for the input/output ports. Do the following. By this etching, the intersection C of the planar pattern shown in FIG. 1 is formed. Thereafter, the entire surface is covered with an insulating film 8, and a portion of the insulating film approximately at the center of the intersection C is removed to form a window 10, where T
After depositing i/Pt/Au and loading the upper electrode 11, the lower surface of the substrate 2 is polished and AuGeNi/Au is deposited thereon to form the lower electrode 1.

Here, the upper electrode 11, the lower electrode 1, and the Zn diffusion region 9 constitute a refractive index changing means, and when a predetermined amount of current is injected from the upper electrode 11, the Zn diffusion region 9
The refractive index of the Zn diffusion region 9 decreases, and the boundary of the Zn diffusion region 9 in the upper cladding layer 6 appears as a reflective surface. In addition to the semiconductor materials described above, the optical switch may be made of a dielectric material such as LiNbO3.

Furthermore, the refractive index changing means is not limited to being operated by current injection from the upper electrode 11 as described above, but can also be operated by voltage application depending on the configuration of the waveguide. Now, FIG. 4 shows the switching characteristics when the radius of curvature R of both sides C1 and C2 at the intersection C in the optical switch shown in FIG. 1 is set to 5 mm.

In the figure, the ◯ marks represent changes in the light reception power of the through port, and the ● marks represent the changes in the light reception power of the reflection port. As is clear from FIG. 4, in this optical switch, when no current is injected from the electrode 11 (non-switching time), for example, light incident from the input port A1 travels straight through the intersection C and passes through the through port (output port A2). ) is propagated. Then, as the injection current from the electrode 11 increases, the refractive index of the Zn diffusion region 9 decreases, and the light reception power at the reflection port (output port B2) increases accordingly, and switching is performed at an injection current of 250 mA. The action is realized.

Next, in the optical switch shown in FIG.
Four types of optical switches were manufactured by setting the crossing angle θ of the waveguides and the radius of curvature R of both sides C1 and C2 of the crossing part to the values shown in Table 1. For these optical switches, the amount of crosstalk during switching operation was measured. The results are shown in Table 1. For comparison, the amount of crosstalk at the time of switching operation was similarly measured for the conventional optical switch shown in FIG. 5 having the intersection angle θ shown in Table 1. The results are also listed in Table 1.

[0020]

[Table 1]

[0021]

[Effects of the Invention] As is clear from the above description, in the waveguide type optical switch of the present invention, the optical waveguides intersect with each other to form an intersection, and the intersection is provided with a refractive index changing means. In the waveguide type optical switch, since the side portion of the intersection connecting the input port where light enters and the output port where light is reflected is curved, optical loss during switching operation is reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing an example of a planar pattern of an optical switch of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is a sectional view taken along line III-III in FIG. 1;

FIG. 4 is a schematic plan view showing a planar pattern of an example of a conventional optical switch.

FIG. 5 is a graph showing an example of switching characteristics of the optical switch of the present invention.

[Explanation of symbols]

A Waveguide A1 Injection port A2 Output port B Waveguide B1 Injection port B2 Output port C Intersection C1, C2 Side of intersection C θ Crossing angle of waveguide R Radius of curvature of side parts C1 and C2 1 Lower electrode 2 Board 3 Buffer layer 4 Lower cladding layer 5 Core layer 6 Upper cladding layer 7 Cap layer 8 Insulating film 9 Zn diffusion area 10 Window 11 Upper electrode

Claims (1)

[Claims] 1. A cross section connecting an input port group and an output port group is formed by intersecting the optical waveguides, and a refractive index changing means is disposed at the cross section, so that one of the input port groups is connected to the input port group. In a waveguide type optical switch that can change the optical path by reflecting light incident from one input port to one output port of the output port group, an input port where the light enters and a side where the light is reflected. A waveguide type optical switch characterized in that at least a side portion of the output port of the intersection connecting the output port and the output port is curved.