JPH01136131A - Waveguide type optical switch - Google Patents

Abstract

PURPOSE:To decrease the power consumption, to facilitate the manufacture which follows up the simplification of a dielectric strength structure and to miniaturize an optical switch element by extending the interval of a waveguide from both ends of a coupling area to the center. CONSTITUTION:On a substrate 10, two pieces of waveguides 11, 12 are placed and formed adjacently. In the coupling area 13 of the waveguides 11, 12, at both ends of its coupling area 13, a waveguide interval is small in order to obtain optical coupling between the waveguides 11, 12, and the waveguide interval is extended from both the ends of the coupling area 13 to the center. How to extend the interval between the waveguide 11 and 12 in the coupling area 13 shall be conformed to a specific function. When the voltage V0 of prescribed polarity applied to electrodes 14-17 is turned ON/OFF, the direction of a waveguide propagated in the waveguides 11, 12 can be switched to a cross state and a bar state. In such a way, the power consumption is decreased, the manufacture is facilitated by following up the simplification of the dielectric strength structure and an optical switching element is miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a waveguide optical switch that electrically switches and controls the traveling direction of an optical signal propagating in a waveguide.

(Prior art) Conventionally, the technology in this field is described in "F Optical Integrated Circuits" by Nishihara, Makige, and Suhara, 1st edition (1986-2-25), Ohmsha P, 304-307. was there. below,
Its configuration will be explained using figures.

FIG. 2 is a perspective view showing a configuration example of a conventional directional coupler type waveguide optical switch.

This optical switch has a substrate 1 having an electro-optic effect,
Two guide Jl? 82.3 are arranged and formed in close proximity to each other, electrodes 4 and 5 are provided on the coupling region of the waveguide 2.3, and the waveguide 2 under the coupling region is , 3, the structure allows control of the refractive index. The length of the coupling region is the length at which the light input to the negative waveguide 2 (or 3) is output from the other waveguide 3 (or 2) when the voltage V□ is not applied. is set to .

Voltage V is applied to electrodes 4 and 5. By applying , the resonance condition of the two waveguides 2 and 3 is broken, and the light that has entered one waveguide 2 (or 3) comes to be output from the same waveguide 2 (or 3). Since light entering from one waveguide 2 (or 3) is completely output from the same waveguide 2 (or 3), the propagation constant difference Δβ (=voltage V) between the two waveguides 2 and 3.

(proportional to) must be a certain value, for example, as shown in the following equation.

π This type of optical switch has the advantage that the operating voltage Vo can be made relatively low and the optical propagation loss is also small.

(Problems to be Solved by the Invention) However, in the optical switch having the above structure, the operating voltage Vo is relatively high, which makes it difficult to manufacture an optical switch element with a withstand voltage structure and increases the size. Furthermore, there is a problem in that power consumption increases.

The present invention provides a waveguide type optical switch that does not solve the problem of the prior art, which is that the operating voltage is relatively high.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method in which a plurality of waveguides are arranged close to each other and electrodes are provided on the coupling region of each waveguide. In the optical coupler type waveguide optical switch, the interval between the waveguides is widened from both ends of the coupling region toward the center.

(Function) According to the present invention, since the waveguide optical switch is configured as described above, the difference in propagation constant between the waveguides in the coupling region is reduced, thereby reducing the operating voltage for switching the optical switch. Therefore, the above-mentioned problem can be eliminated.

(Embodiment) FIG. 1 is a perspective view of a directional coupler type waveguide optical switch showing a first embodiment of the present invention.

This optical switch has a substrate 10 that exhibits an electro-optic effect, such as a single crystal substrate of lithium niobate (L i NbO3) or a compound semiconductor substrate such as gallium arsenide (GaAs). In this case, two waveguides 11 and 12 are arranged close to each other. In the coupling region 13 of the waveguide 11.12, the coupling region 1
In order to couple the light between the waveguides 11 and 12, the waveguide spacing is small, for example, about 3 to 5 μm, at both ends of the coupling region 13, and the waveguide spacing is widened from both ends of the coupling region 13 toward the center. There is. Two waveguides 1 in the coupling region 13
On 1.12, electrodes 14 and 15 are provided, respectively.
Furthermore, electrodes 16.17 are provided along the outside of each electrode 14.15, respectively.

It is assumed that the distance between the waveguides 11 and 12 in the coupling region 13 is increased according to a specific function. For example, waveguide 11
It is assumed that the change in the coupling coefficient between and 12 follows the following equation.

However, Ko; Coupling coefficient L at the minimum point of waveguide spacing; Length Z of the coupling region 13; Propagation distance of guided light (-〇~L) In equation (2), when voltage is applied to the electrodes 14 to 17. For example, in order to create a state (cross state) in which the light input to one waveguide 11 (or 12) is output from the other waveguide 12 (or 11) when the waveguide is not set to π.

And a positive voltage V is applied to the electrodes 15 and 16. , and electrode 1
4. If a negative polarity voltage VO is applied to each of 17, 2
The resonance conditions of the two waveguides 11 and 12 are broken, and the light that has entered one waveguide 11 (or 12) is completely output from the same waveguide 11 (or 12) (bar state). Therefore, the voltage of the predetermined polarity to be applied to the electrodes 14 to 17 is
. By turning on and off, the direction of guided light propagating in the waveguides 11 and 12 can be switched between a cross state and a bar state.

Figure 3 shows the crosstalk (Δβ・
L/π), and the amount of crosstalk (dB) to the waveguide output end in the cross direction is plotted on the vertical axis. Solid line A is the crosstalk characteristic of the first embodiment, and broken line B is the conventional crosstalk characteristic.

As is clear from FIG. 3, the solid line A of the first embodiment switches between the cross state and the bar state at Δβ·L/π′; 1.20, whereas the conventional broken line B switches between the cross state and the bar state at Δβ·L/π′; /π
; At 1.68, switching between the cross state and the bar state is performed. Therefore, in the first embodiment, compared to the conventional one, the
The operating voltage can be reduced by /1.4, thereby reducing power consumption, simplifying manufacturing due to the simplification of the withstand voltage structure, and downsizing the optical switch element.

In addition, in FIG. 1, the two electrodes 14 on the waveguide 11 and 12
．． In addition to 15, two electrodes 16, 17 are provided on its outer part. In the center of the coupling region 13, two waveguides 11
．． 12 becomes wider, and the electric field strength between the electrodes 14 and 15 above it becomes smaller, which may lead to an increase in the operating voltage. Therefore, the electrode B116.17 is provided and the electrode 14.1
5 to prevent the operating voltage from increasing. However, depending on how the distance between the waveguides 11 and 12 is widened, the electrodes 16 and 17 may be omitted.

FIG. 4 is a perspective view of a directional coupler type waveguide optical switch showing a second embodiment of the present invention, and the same elements as those in FIG. 1 are given the same reference numerals. There is.

In this optical switch, the four electrodes 14 of the first embodiment,
15, 16, and 17 are each divided into two in the longitudinal direction, and eight electrodes 14a, 14b, 15a, 15b, 1
6a, 16b, 17a.

17b. and electrodes 14b and 15a.

A positive voltage V is applied to 16a and 17b. , the other electrode 14a
, 15b, 16b, and 17a, a cross state can be obtained by applying a negative voltage Vo to each of them. In addition, electrode 1
5a, 15b, 16a.

Positive voltage V is applied to 16b. , the other electrodes 14a, 1
By applying a voltage Vo of negative polarity to 4b, 17a, and 17b, a bar state is obtained.

In this booklet, each type; fI+14a, 14b ~ 17
The voltage V applied to a and 17b. By changing the polarity of the switch, switching between the cross state and the bar state can be performed.Similarly to the first embodiment, this embodiment has the advantage that switching operation can be performed with a lower operating voltage than the conventional one. . Further, as in the first embodiment, the electrodes 16a, 16b, 17
It is also possible to omit a and 17b.

Note that the present invention is not limited to the illustrated embodiment; for example, the first embodiment
Various modifications are possible, such as making the doglegged waveguides 11 and 12 in the coupling region 13 in FIGS. .

(Effects of the Invention) As explained in detail above, according to the present invention, the spacing between the waveguides is widened from both ends of the coupling region toward the center, so the difference in propagation constant between the waveguides is reduced, and the optical switch is The switching operating voltage is reduced. Therefore, the effects of reducing power consumption, simplifying manufacturing due to the simplification of the withstand voltage structure, and downsizing the optical switch element can be expected.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical switch showing a first embodiment of the present invention, FIG. 2 is a perspective view of a conventional optical switch, and FIG. 3 is a perspective view of a conventional optical switch.
Crosstalk characteristic diagram of the optical switch shown in Fig. 2 and Fig. 4.
The figure is a perspective view of an optical switch showing a second embodiment of the present invention. 10... Substrate, 11.12... Waveguide, 13... Coupling region, 14-17, 14a, 1
4b to 17a, 17b...electrodes. Applicant's representative: Kakimoto Kyo Acid Figure 1 Figure 2

Claims (1)

[Claims] 1. In a waveguide optical switch in which a plurality of waveguides are arranged closely in parallel and electrodes are provided on coupling regions of each waveguide, the spacing between the waveguides is determined by the coupling region. A waveguide optical switch is characterized by a region that expands from both ends toward the center. 2. The waveguide optical switch according to claim 1, wherein the electrode is divided into two in the longitudinal direction of the waveguide.