JPH01183629A - Optically bistable semiconductor laser - Google Patents

Abstract

PURPOSE:To reduce increase of a threshold level, and also, to stabilize a characteristic due to decrease of the number of control electrodes by allowing plural input use optical waveguides to intersect and couple against one saturable absorption area of an output use optical waveguide. CONSTITUTION:As for this composite type bistable laser, two input use optical waveguides are coupled to one saturable absorption area by allowing them to intersect at an inclination angle. According to such constitution, an operation of OR and AND can be executed in the same way as a conventional composite type bistable laser. Also, by controlling an injection current which is supplied to an output use optical waveguide, a threshold level is set so that an output light O1 is outputted, when one of input light beams I1, I2 is made incident. Moreover, as for an AND operation, by controlling the injection current, the shreshold level is set so that the output light O1 is outputted, when both of the input light beams I1, I2 are made incident. In such a state, by forming the input use optical waveguide by the same active area as that of the output use optical waveguide and injecting a current, it is also possible to amplify the input light beam, and also, it is also possible to decrease the saturable absorption area and the number of electrodes.

Description

[Detailed Description of the Invention] [Summary] Concerning the configuration of an optical bistable semiconductor laser whose optical output is bistable with respect to optical input, in order to prevent an increase in the threshold value and stabilize the characteristics, the saturable absorption region is In the optical bistable semiconductor laser having the above, a plurality of input optical waveguides are cross-coupled to one saturable absorption region of the output optical waveguide.

[Industrial application field] The present invention relates to the structure of an optical bistable semiconductor laser.

Optical bistable semiconductor lasers are being used as functional devices for memory, arithmetic, and other functions in the fields of communication and information processing that utilize light, and their development is being strongly promoted because they can be made compact and highly integrated.

Improving performance is an extremely important issue in such optical bistable semiconductor lasers.

[Prior art and problems to be solved by the invention] First, J.
, proposed by 1asher (Solid 5
tate Electronics Volume 7 (1964)
, PP, 707-716). Furthermore, through subsequent research, it was announced that bistable operation could be obtained by injecting external laser light with almost the same wavelength from the direction of the cavity (El
ectron Letters, 17. No, 20. (
1981), PP, 741).

FIGS. 3(a) to 3(C) are perspective views of the optical bistable semiconductor laser (hereinafter referred to as a bistable laser) (FIG. 3(al)).

It shows a plan sectional view ((b) in the same figure; a concave section AA in the same figure (a), and a side sectional view ((C) in the same figure; a cross section BB in the same figure (a)), where ■ is the active region, 2 is a saturable absorption region, and 3 and 4 are electrodes.By independently controlling the bias current flowing through the divided electrodes 3 and measuring the output light relative to the input light, two stable states are obtained, and a hysteresis curve is drawn. Figure 4 shows the behavior of the output light relative to the input light of the bistable laser.
The width of this hysteresis can be arbitrarily set by changing the bias current. Further, when the bias current is set in the bistable region of the current-optical output characteristic and a light pulse is applied, laser oscillation is maintained and the device can be operated as a memory. Furthermore, this also enables switching operation, and FIG. 5 is a diagram showing the switching operation of the output light with respect to the trigger input light of the bistable laser.

In this method, the optical bias of the trigger input light is located at the center of the hysteresis curve, and the switching operation is obtained by manual input of optical pulses.

The internal cross section of a semiconductor laser capable of such operation is shown in the sixth section.
FIG. 6 is an example of an InGaAs P optical bistable laser. In the figure, 21 is an n-InP substrate, 22 is an n-1nP buffer layer, and 1 and 2 are InGaAs.
P active layer (the optical waveguide consists of this active region 1 and saturable absorption region 2), 23 is a p-1nP cladding layer, 24
3 indicates ten electrodes, and 4 indicates one electrode. Although not shown, both sides are replaced with semi-insulating InP layers.

By the way, in such a bistable laser, the optical waveguide is a striped straight line, and the input light and output light are coaxial, so even if there is a saturable absorption region in the middle of the optical waveguide, the input Light leakage (transmission) affects the output light and causes S
There is a drawback that the N ratio (noise ratio) is not good.

In order to alleviate these drawbacks, a bistable laser has been proposed in which the optical waveguide for the input light intersects the optical waveguide for the output light from the lateral direction at right angles (Japanese Patent Application Laid-Open No. 61-1999). 79282).

FIG. 7 shows a plan cross-sectional view of the improved conventional composite bistable laser, and the figure shows an implementation in which two saturable absorption regions are each coupled to one input optical waveguide by crossing them. In the example, IO in the figure is an output optical waveguide (an optical waveguide consisting of an active region and a saturable absorption region), 11.12 is a saturable absorption region, 21.22 is an input optical waveguide, II
+12 is input light, O! is the output light. Then,
When input light enters the saturable absorption region from the lateral input optical waveguide, the light is absorbed by the saturable absorption region and output from the output optical waveguide, transitions to a bistable state, and enters the eighth
It becomes possible to perform logical sum and logical product operations as shown in the figure.

That is, by controlling the injection current applied to the output optical waveguide, the output light calculated by the logical sum or logical product shown in FIG. 8 can be obtained.

However, the structure of the conventional composite bistable laser shown in FIG. 7 requires the same number of saturable absorption regions as the number of inputs, resulting in an increase in the threshold value and an increase in the number of control electrodes. For example, the threshold value can be increased by increasing the resonator length (length of the optical waveguide) by 3
00μm, and if one saturable absorption region with a length of 30μm is provided, the threshold value of 20mA becomes 30mA and 10
It increases by about mΔ. Therefore, if more saturable absorption regions are provided, the threshold value becomes higher and driving becomes difficult, which becomes a major cause of shortening the lifetime of the bistable laser.

Further, an increase in the number of electrodes becomes a factor causing instability of laser oscillation characteristics. Therefore, an increase in the saturable absorption region is not desirable for a bistable laser.

The present invention proposes an improved structure of a composite bistable laser aimed at reducing such problems, preventing an increase in the threshold value, and stabilizing the characteristics.

[Means for solving the problem] The purpose is to cross the output optical waveguide with the input optical waveguide from the side, so that a plurality of manual optical waveguides can be connected to one saturable absorption region of the output optical waveguide. This is accomplished by a bistable laser whose wavepaths are cross-coupled.

[Operation] In other words, the present invention has a structure in which two or more optical waveguides for manual power are coupled to one saturable absorption region of the output optical waveguide at an angle from the lateral direction. In this way, the saturable absorption region can be reduced without increasing the number of electrodes in proportion to the number of input optical waveguides.

A composite bistable laser with a small number of electrodes is constructed, which reduces the increase in threshold value and stabilizes the laser oscillation characteristics.

[Example code] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a cross-sectional plan view of a composite bistable laser according to the present invention, and is an embodiment in which two input optical waveguides are coupled to one saturable absorption region by crossing them at an inclination angle. 10 in the figure is an output optical waveguide.

11 is a saturable absorption region, 31.32 is an input optical waveguide.

r, , r2 are input lights, and ol is output light.

With this configuration, logical sum and logical product operations similar to those of the conventional composite bistable laser shown in FIG. 5 are possible.
The logical operation is shown in FIG. 2 (al, fb). Second
In the figure (al indicates a logical sum operation, the injection current applied to the output optical waveguide is controlled, and the threshold value is set so that the output light 01 is output when either the input light 1. or I2 is incident. In addition, Fig. 2(b) shows the AND operation, and the injection current is controlled so that the threshold value is set so that the output light 01 is output when both the human power lights +, , and r2 are incident. Set.

If the input optical waveguide is formed with the same active region as the output optical waveguide and current is injected here, it is also possible to amplify the input light.

Although the above is an example, by doing so, the saturable absorption region and the number of electrodes can be reduced in a composite bistable laser having operating characteristics similar to those of the conventional laser.

[Effects of the Invention Therefore, according to the composite bistable laser according to the present invention,
The structure has a plurality of input optical waveguides coupled to one saturable absorption region, which reduces the increase in threshold value, and
The characteristics can be further stabilized by reducing the number of control electrodes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional plan view of a composite bistable laser according to the present invention. FIG. 2 is a diagram showing the logical operation of a composite bistable laser according to the present invention. FIG. 3 is a diagram showing a conventional bistable laser. Figure 4 is a diagram showing the operation of a bistable laser, Figure 5 is a diagram showing the switching operation of a bistable laser, Figure 6 is a cross-sectional view of an InGaAs P optical bistable laser, and Figure 7 is a diagram showing a conventional composite bistable laser. FIG. 8, a plan cross-sectional view of the stable laser, is a diagram showing logical operations. In the figure, 1 is an active region, 2 is a saturable absorption region, 3.4 is an electrode, 10 is an output optical waveguide (an optical waveguide consisting of an active region and a saturable absorption region), and 11 and 12 are saturable absorption regions. , 21, 22.3L 32 is an input optical waveguide, io, ji,
I2 indicates human power light, and Oo, O, indicates output light. O is JL ↑ 1st, 2nd figure pf fixed one length ゛＾Mataitch>7'tpQ@hon 1st flash 5U
A Figure 6 shows i5 Hikimori Motoyo disciples←

Claims (1)

[Claims] An optical bistable semiconductor laser having a saturable absorption region, characterized in that a plurality of input optical waveguides are cross-coupled to one saturable absorption region of an output optical waveguide. Optical bistable semiconductor laser.