JPH02174182A - Optical bistable element - Google Patents

Abstract

PURPOSE:To reduce wavelength dependence of light-receiving elements for mitigating the requirements for the wavelength of input light by integrating one or a plurality of light-receiving elements on a part of active regions or a part of a saturable absorption region of a bistable semiconductor laser. CONSTITUTION:One or a plurality of light-receiving elements 17 to 19 are integrated on a part of active regions 21 and 22 or on a part of a saturable absorption region 20 of bistable semiconductor lasers 11 to 16 provided with the saturable absorption region 20 and the active regions 21 and 22. For instance, the bistable semiconductor lasers 11 to 16 have the saturable absorption region 20 and two active regions 21 and 22 on both sides thereof while phototransistors 17 to 19 as the light-receiving elements are integrated on the active region 22. Thereby, wavelength dependence of the light-receiving elements 17 to 19 is small so that the conditions to be required for the wavelength of input light can be mitigated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an integrated optical bistable device.

[Conventional technology]

FIG. 4 shows an example of a conventional optical bistable element. In the figure, 1 is a p-type, 1IlGaAs contact layer, 2 is an undoped multiple quantum well (MQW) layer, and 3 is an n-type At1GaAs contact layer.
In the contact layer, 4 is a resistor, and 5 is a power supply. This element is usually seeded (S E E D, 5elfElectro
-optic Effect Device).

Next, the operation of this element will be explained. This seed is QC3E.

Quantum Confine 5palk Eff
ect). That is, the effect that the exciton absorption peak shifts to the lower energy side when an electric field is applied to the MQW layer 2 is utilized.

This effect is shown in FIG. FIG. 5 is a wavelength characteristic diagram of absorption in the element of FIG. 4, where the horizontal axis shows the wavelength of input light and the vertical axis shows the magnitude of absorption. Moreover, S1 is a characteristic curve when no electric field is applied, and S2 is a characteristic curve when a strong electric field is applied. When the wavelength of the input light is selected to be the wavelength λi corresponding to the exciton absorption peak in the absence of an electric field, as can be seen from FIG. 5, the absorption of the input light decreases due to the shift of the absorption peak when a strong electric field is applied.

In Fig. 4, when the intensity of the input light a is weak, the MQW layer 2
Since the resistance is larger than that of the external resistance 4, most of the applied voltage is applied to the MQW layer 2, and absorption of the input light a is small. As the intensity of the input light a becomes stronger, the photocurrent generated in the MQW layer 2 increases, and the voltage applied to the MQW layer 2 decreases accordingly. Therefore, the absorption of the input light a increases, and the voltage applied to the MQW layer 2 decreases. on the other hand,
On the other hand, when the intensity of input light a is decreased, the complete opposite positive feedback occurs, that is, decrease in photocurrent = increase in applied voltage of MQW layer 2 - decrease in absorption, and the intensity of transmitted light a suddenly decreases. increases to As a result, as shown in FIG. 6, a bistable relationship is obtained between the power P in of the input light a and the power P out of the transmitted light A.

[Problem to be solved by the invention]

Since the conventional optical bistable device is configured as described above, it has the following problems.

■The wavelength of the input light a must be adjusted with high accuracy (it must match the exciton absorption peak. Therefore, the conditions required for the light source are extremely strict.

(2) Since it is a passive device, the intensity of transmitted light (output light) b is smaller than the intensity of input light a, making it unsuitable for multi-stage connection. Also, the on-off ratio is small.

The present invention has been made in view of these points, and its purpose is to relax the conditions required for the wavelength of input light so that the output light intensity is greater than the input light intensity. The objective is to obtain an optical bistable device.

[Means to solve the problem]

In order to solve such problems, the present invention provides a bistable semiconductor laser having a saturable absorption region and an active region, in which one or more light receiving elements are provided in a part of the active region or in a part of the saturable absorption region. It is designed to integrate.

C Effect] In the optical bistable element according to the present invention, the wavelength dependence of the light receiving element is small, and the bistable semiconductor laser has active properties.

〔Example〕

The present invention is characterized in that a bistable semiconductor laser, which is an active device, and a light receiving element are integrated.

The above-mentioned light-receiving element has a feature of small wavelength dependence,
Examples include phototransistors and diodes.

FIG. 1 is a block diagram showing one embodiment of an optical bistable device according to the present invention. In the figure, 11 is an electrode, 12 is a substrate, 13 is a lower cladding layer, 14 is an active layer, 15 is an upper cladding layer, 16 is a contact layer, 17 is a collector layer, 1
8 is a base layer, 19 is an emitter layer, 11 to 16 constitute a bistable semiconductor laser which is an active device, and 17
19 constitute a phototransistor as a light receiving element.

Further, a is input light, and c and d are output lights. The bistable semiconductor laser has a saturable absorption region 20 in the center and two active regions 21, 22 on either side of the saturable absorption region 20, on which a phototransistor is integrated.

Next, the operation of the optical bistable device configured in this way will be explained. Active region 21 in a bistable semiconductor laser
and 22, respectively, I! I+I
! If z is the total current! The change in the power P ouL of the output light with respect to =Iz++Izz has bistable characteristics as shown in FIG. Now, the value of I2□ is set to 11, the value just before the laser oscillates, and the value of ■2□ is changed from 0 to 1. When the photocurrent of the phototransistor is varied up to −41, the difference between the power p in of the artificial light a to the phototransistor and the power P ouL of the output light C or d from the bistable semiconductor laser is as shown in Fig. 3. A bistable property like this can be obtained.

In this embodiment, a phototransistor is used as the light receiving element, but a photodiode can also have the same effect.

In addition, in the case of this example, the light receiving element was integrated in a part of the active region, but the light receiving element was integrated in a part of the saturable absorption region.
Optical switch characteristics can be obtained by supplementing absorption saturation with photocurrent.

Furthermore, although the number of light receiving elements is one in this embodiment, it is also possible to use a plurality of light receiving elements, and by using a plurality of light receiving elements, an optical logic element can be constructed. In order to provide a plurality of active regions, the active region may be divided into two or more regions, and a light receiving element may be provided in each region.

In addition, the input light a can be adjusted by making the electrode 11 annular, etc.
It is also possible to enter the electrode 11 from above.

〔Effect of the invention〕

As explained above, the present invention integrates one or more light-receiving elements in a part of the active region or a part of the saturable absorption region of a bistable semiconductor laser having a saturable absorption region and an active region. As a result, the wavelength dependence of the light-receiving element is small, so the response wavelength range is widened, and the requirement for the wavelength of human-powered light is greatly relaxed.

Furthermore, since bistable semiconductor lasers are active integrated devices, they have a large on-off ratio and can be connected in multiple stages.

Furthermore, by providing a plurality of light receiving elements, optical logic elements such as AND and OR can be constructed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an optical bistable device according to the present invention, FIG. 2 is a characteristic diagram of output optical power versus current in the device of FIG. 1, and FIG. 3 is an output of the device of FIG. 1. Figure 4 is a diagram showing the configuration of a conventional optical bistable element; Figure 5 is a characteristic diagram showing the absorption characteristics of the conventional element; Figure 6 is a diagram of the output optical power pair of the conventional element. FIG. 3 is a characteristic diagram of input optical power. DESCRIPTION OF SYMBOLS 11... Electrode, 12... Substrate, 13... Lower cladding layer, 14... Active layer, 15... Upper cladding layer, 16... Contact layer, 17... Collector layer, 1
8... Pace layer, 19... Emitsuta layer, 20...
Saturable absorption region, 21.22... active region.

Claims (1)

[Claims] An optical bistable semiconductor laser comprising a bistable semiconductor laser having a saturable absorption region and an active region, with one or more light-receiving elements integrated in a part of the active region or a part of the saturable absorption region. element.