JPS6191623A - Optical switch element - Google Patents

Abstract

PURPOSE:To realize size reduction and high-speed operation by using a semiconductor for an optical switch element and employing loss modulation as the principle of switching. CONSTITUTION:When a forward current is applied to an electrode 20A which connects respective terminals of waveguides 21A and 21B mutually in constitution shown in a figure, a light signal incident from the waveguide 21A is branched and then amplified and projected on the terminal of the waveguide 21B. The loss at a branching and mixing part is >=9.5dB in principle, so when the degree of amplification is >=100dB, projection light has a higher level than the incident light. Further, when a forward current is applied to electrodes 27A and 27D connecting both terminals of the waveguides 21A and 22B, the light signal from the terminal of the waveguide 21A is projected on the terminal of the waveguide 22B. In this constitution, simultaneous output to plural optional terminals is possible and a gain for projection light is obtained. Further, the integration is possible and a light source function is added.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical switch that is compact and capable of high-speed operation.

[Prior Art] FIG. 3 shows a conceptual diagram of a typical directional coupler type optical switch element among conventional optical switch elements.

In the figure, IA and 2A are input optical waveguides, IB and 2A are input optical waveguides,
B is an output optical waveguide connected to waveguides IA and 2A, respectively, 3A and 3B are electrodes, and the waveguide having the above configuration is formed by diffusing Ti into the LiNbO3 crystal substrate IO.

In this case, 0
For example, when the voltage V is not applied to the electrode 3, the optical signal incident from the waveguide IA is outputted to the output waveguide IB, and when the voltage ■ is applied to the electrode 3, the optical signal is outputted to the output waveguide 2B. can be done. In this method, two waveguides are placed close to each other, and the coupling coefficient of the optical signal between them is controlled by an electric field applied by an electrode 3 to perform switching.

Therefore, when the optical signal incident on the input waveguide IA is output to the output waveguide 2B, the input waveguide 2A
The optical signal incident on is output to the output waveguide IB. In this state, it is theoretically impossible to further output the optical signal from the input waveguide 2A to the output waveguide 2B.

Furthermore, since the switching operation is performed by controlling the phase conditions of the light, the manufacturing conditions for the optical waveguide are strict, the characteristics depend on the polarization of the incident light, and there are disadvantages such as poor stability with respect to temperature. Furthermore, since all conventional optical switches of this kind are composed of passive circuits, they have drawbacks such as large insertion loss and large element shapes.

[Objective] Therefore, in order to solve these drawbacks, an object of the present invention is to provide an optical switching element configured using a semiconductor as a material of the optical switching element and using loss modulation as the switching principle. be.

[Structure of the Invention] In order to achieve the above object, the present invention provides an optical switch element having a plurality of input terminals and a plurality of output terminals, and in which an optical waveguide is disposed between these input and output terminals.
A semiconductor waveguide that forms a PN junction is placed in the waveguide connecting each of the terminals, and a P-N junction is formed between any desired terminals.
The present invention is characterized in that the propagation of optical signals between arbitrary desired terminals is controlled depending on the presence or absence of current injected into the N junction.

〔Example] The present invention will be described in detail below based on the drawings.

FIG. 2 is a conceptual diagram for explaining the switching principle used in the complete optical switch element. Here, IIA and IIB are input and output optical waveguides, respectively, 14A and 14B are coupling lenses arranged to face input and output optical waveguides 11A and 11B, respectively, and 15
is a semiconductor element having a PN junction, and the lens 14A
and 14B is a power supply applied to the semiconductor element 15, and R is a protection resistor.

The characteristics of the optical switch with the configuration shown in Fig. 2 are described in the literature rM, Ikeda, "La5er diode".
5w1tch”.

EIectron, Lett, Vol. 17. N
o, 23. pp. 899-1300° 1981J. That is, the optical signal incident from the input waveguide 11A is injected into the PN junction of the semiconductor element 15.

Here, when no current is injected into the PN junction, the incident light is absorbed by the junction and does not emerge; however, when a current is injected into the PN junction in the forward direction, the incident light The optical signal is amplified and emitted by the PN junction, and is coupled to the output waveguide 11B. Here, if a laser diode structure is used as the PN junction element 15, a gain of about 30 dB can be obtained with the element. Therefore, isolation defined as the on/off ratio of the optical signal can be obtained at 80 dB or more.

Next, FIG. 1 shows an embodiment of a complete optical switch element using the principle of the optical switch explained above.

Figure 1 shows a plan view when there are four optical signal terminals.
Here, 21A, 22A, 21B, and 22B are input and output waveguides, respectively, but as described later, they are not limited to the input side or the output side. In this example, the waveguides 21A, 22B, and 22A and 21B are arranged facing each other and perpendicular to each other. 25 is a waveguide 21A.

Semiconductor element having a waveguide-shaped PN junction connecting terminals 21B, 22A, and 22B, 268 to 280 and 2
7A to 270 are waveguides 21A, 21B, 22A, 22B
These electrodes are electrically separated from each other and placed on the waveguide of the semiconductor element 25 by connecting the respective terminals of the semiconductor element 25, so that current can be injected into each terminal separately and independently. These electrodes 28
The lower waveguide portions of A~280 and 27A~270 are
It has an active layer with a PN junction as explained in FIG. 2, and its structure is similar to that of a buried tuple heterostructure semiconductor laser. The production of a waveguide having a PN junction having the structure shown in FIG. 1 can be achieved by forming a waveguide pattern using a reactive sputter etching technique, and then recrystallizing the area around the waveguide.

Next, a method for operating this optical switch element will be explained. As in the case of FIG. 2, the wavelength of the optical signal is selected approximately at the center of the gain spectrum determined by the semiconductor material used as the active layer of the optical switch element.

Now, a case will be described in which the device operates in the same way as a conventional 2×2 optical switch element. In order to output the optical signal incident from the waveguide 21A to the terminal of the waveguide 21B, a forward current may be injected into the electrode 26A that connects each terminal of the waveguides 21A and 21B, whereby the optical signal is branched. After that, it is amplified and output to the terminal of the waveguide 21B. In principle, the loss at branching and merging sections is 9.5 dB.
i! Therefore, if the amplification degree is 10 dB or more, the level of the emitted light will be amplified to the level of the incident light.

Similarly, the optical signal from the terminal of the waveguide 21A is transferred to the waveguide 22A.
In order to emit the light to the terminal B, a forward current may be injected into the electrodes 27A and 27D connecting both terminals of the waveguides 21A and 22B.

The same applies to the propagation of light from other terminals between waveguides to other terminals. Furthermore, by applying current to a large number of electrodes at the same time, it is of course possible to emit optical signals from a large number of terminals at the same time.

When fabricating an optical switching device with the structure shown in Figure 1 using a normal InGaAsP-based semiconductor material, the optical power must be 10 dB or more when the length of the waveguide with the active layer is 200 pm. Gain and isolation of more than 50 dB could be obtained. therefore.

The optical switch element of the present invention can be constructed with a size of 300 gm' or less.

Also, each electrode 28A to 2B0, 2? By controlling the amount of current injected into A to 27D, the gain in each part can be controlled, so the output light level to each terminal can be made the same, or it can be set to any desired level. It is. This means that there is a large tolerance for precision during manufacturing, and the optical switch element of the present invention is also advantageous in terms of manufacturing efficiency.

[Effects] As explained above, in the present invention, when performing optical switching, switching between gain and absorption loss is used, and the branching waveguide portion is configured with an active layer waveguide, so the following advantages are achieved. is obtained.

(1) Simultaneous output to any desired plural terminals is possible.

(2) Gain can be obtained for the emitted light.

(3) A large-scale switch network can be easily configured.

(4) It can be easily integrated on a semiconductor substrate.

(5) The device of the present invention is not only a switch, but also can emit light, so it can have an additional function as a light source.

(6) Since it is a solid-state device, it has a long life.

(7) Since the tolerance of element accuracy is large, it can be manufactured in large quantities as a paper stock.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the structure of an embodiment of the optical switch element of the present invention, and FIG. 2 is a conceptual diagram illustrating the principle of the optical switch of the present invention. FIG. 3 is a conceptual diagram showing an optical directional coupler as an example of a conventional optical switch element. IA, 2A...input waveguide, 1B, 2B...output waveguide, 3A, 3B...electrode, 6...electrode that can independently inject current into the waveguide connecting each terminal, lO . . . LiNbO3 crystal substrate, 11A .
B, 22A, 22B... Input/output optical branch, 25... Semiconductor element having a waveguide-like PN junction. 26A~2fiD, 2? A~270...electrode. Fig. 1 21A, 21B, 22A, 22B--4 liquid paths 25-
・-6 corresponding positive condition PH Shogo SE ringing 3rd car number Aoko 2GA~2
6T), 2'7A to 27D-Production process diagram 2■ Figure 3■

Claims (1)

[Claims] In an optical switch element having a plurality of input terminals and a plurality of output terminals, and an optical waveguide arranged between these input and output terminals, a PN
A semiconductor waveguide with a junction formed therein is arranged, and propagation of an optical signal between any desired terminals is controlled depending on the presence or absence of a current injected into a PN junction between any desired terminals among the terminals. An optical switch element characterized by: