JPS6188587A - Writing system of optical memory - Google Patents

Abstract

PURPOSE:To memorize either one of optical signals applied to both ends of an active layer by separately controlling injection currents fed to two electrodes for a bistable semiconductor laser having structure in which an electrode is divided into two. CONSTITUTION:Electrodes 301,302 divided into two in a bistable semiconductor laser 300 are each supplied with injection currents i1, i2 by variable constant- current sources 100, 101. In the laser 300, currents i1 and i2 are severally con trolled, thus memorizing either one of two optical signals P1 and P2 respectively projected to one end 304 and the other end 305 of an active layer 303, then emitting optical signals P0 from both ends of the active layer 303. That is, bidirectional memory operation can be acquired according to the system.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical memory insertion method using a bistable semi-diamond laser exhibiting hysteresis characteristics between the injection current and the amount of emitted light.

(Prior art) Conventionally, current mode logic is known as a device that performs logical operations on electrical signals at high speed, using a current switch as a basic block, and in recent years, GaAs
Research is progressing on ultra-high-speed logical operation devices using FETs, Joseph Non coupling elements, and the like.

However, high-speed digital information processing of a large amount of two-dimensional data such as image information using electrical signals has limitations in terms of calculation speed, power consumption, etc.

Therefore, it is desired to realize an optical logic operation device that can digitally process optical signals that are compatible with high-speed, two-dimensional parallel information processing. A source memory that can read and write information is essential.

As such an optical memory, for example, the literature Electronics Letter
A bistable semiconductor laser described on page 741 of Vol. 17 is known.

FIG. 5 500 is a sectional view showing a specific example of a bistable semiconductor laser. The structure is almost the same as a commonly used current injection type semiconductor laser, for example, GaAtAs/GaA
This is a laser with a double heterojunction structure made of S or InGaAsP-/InP. However, it differs from a normal semiconductor laser in that the electrode 501 is not uniform and there is a portion 502 into which current is not injected. Since the current non-injection region 502 functions as a saturable absorber, the bistable semiconductor radar shown in FIG. 5 can have a hysteresis characteristic in the injection current i versus optical output P characteristic. In addition, instead of making the electrode non-uniform, it is possible to provide similar bistable characteristics by making the active layer, which is the light emitting region, non-uniform and providing a saturable absorption region in a part. can. In these bistable semiconductor lasers, by appropriately selecting the injection current l, the output light P with respect to the externally injected light Pi. Bistable properties can also be obtained in the properties of .

FIGS. 6(a) and 6(b) are diagrams for explaining the operation of the bistable semiconductor laser shown in FIG. 5. Figure 6 (,)
is a diagram showing the relationship between the injection current l and the output light amount P0 when the incident light i Pi ”O. In other words, the injection current i
When increasing from 10, the output light Hp suddenly increases at 1==iu. fJ''-increases, and conversely, when the injected current i is decreased from a value equal to or higher than iu, the output light amount P exhibits a hysteresis characteristic such that it rapidly decreases at 1=id, and i2lb
The output light amounts O and P at . It has two stable points A and B of h. 600 shown in FIG. 6(b) is the incident light amount Pi and the outgoing light amount P when the injection current 1=iw in FIG. Indicates the relationship between That is, if the incident light amount P1 is increased from O when the output light amount P0 is at the first stable point A where the output light amount P0=0, the output light amount P. increases rapidly when Pi=Piu, and thereafter, when the incident amount Pi=P1h is decreased, the output light amount P0 hardly decreases and becomes the output light iP. =P0. Move to the second stable point B.

Points A and B in Fig. 6(,) are respectively Fig. 6(b)
represents the same point as points A and B in .

(A rough point to be solved by the invention) In Fig. 6(,), the value of the injection current l is changed from i to ib.
As shown in 601 in FIG. 6(b), the total characteristics of the human emitted light are determined by the incident light iPf where the emitted light amount P rises.
increases from P to Piu, which makes bistable i
It becomes impossible to set the lu semiconductor radar depending on the amount of incident light of Pih.

Figure 7 shows an optical memory writing method according to the prior art.
The same components as in the figure are shown.

FIG. 8 shows a time chart for explaining the operation of the optical memory shown in FIG.

According to FIG. 8, the bistable semiconductor laser 5 shown in FIG.
00 is supplied with an injection current l indicated by 800 by a variable constant current source 700, which stores an optical signal Pi indicated by 801 input from one end 702 of the active layer 701. An optical signal P indicated by 802 is emitted from one end 702 and the other end 703 of the active layer 701 .

As shown in FIG. 6(b), as long as the value of the injected current 1 is ib, the bistable semiconductor laser 500 shown in FIG. The emitted light P is held at either a light amount of 0 or 1; Poh depending on the value entered.

Here, as shown in FIG. 8 803, the value of the injection current i is changed from ib shown in FIG. 6 (,) once to i. The bistable semiconductor laser 500 is reduced to A as shown in FIG.

B It is reset at any stable point, and the output light P0
The amount of light is O. After this, as shown in FIG. 8 804, when the value of the injection current i is increased to iW shown in FIG. 6(a), the bistable semiconductor laser 500 as shown in FIG. 6(b)
can be set by the incident light P1 of the scene Pih. That is, the bistable semiconductor laser 5 shown in FIG.
00 stores a value corresponding to the optical signal Pi incident on one end 702 of the active layer 701 during the period 804 when the value of the injection current i is 1, and thereafter stores that value as long as the value of the injection current i is i5. Hold.

The optical memory according to the prior art shown in FIG.
The O value is latched by controlling the injection current i.

An object of the present invention is to provide an optical memory writing system that can select and store one of two optical signals incident on one end of the active layer and the other island, respectively.

(Means for Solving the Problems) The present invention provides an arrangement in which the electrodes are arranged in two directions of the first and second electrodes in the direction of the resonance axis.
In an optical memory configured by a bistable semiconductor laser that is divided into two, and first and second variable current sources that supply first and second injection currents to the first and second electrodes, respectively. , by controlling the first and second injection current values independently of each other, two optical signals are input from the first electrode side end surface and the 20th electrode side end surface of the active layer of the bistable semiconductor radar, respectively. This is an optical memory writing method characterized by storing one of the values.

(Function) By employing the above-described configuration, the present invention makes it possible to select and store one of the optical signals applied to both ends of the active layer of a bistable semiconductor laser.

In other words, a bistable semiconductor laser with a tandem electrode structure in which the electrode is divided into two in the direction of the resonance axis with a groove in between is used as a bistable semiconductor laser, and two injection currents are supplied to each of the two electrodes. Through individual control, it is possible to select and store one of the optical signals incident on both ends of the active layer.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 3 300 is a sectional view showing a specific example of a bistable semiconductor laser used in the present invention. The basic structure is almost the same as the bistable semiconductor laser 500 shown in FIG.
It differs from the bistable semiconductor laser 500 shown in FIG. 5 in that it is divided into two parts, 3Q2.

Such a bistable semiconductor laser is described in the 1985 National Conference of Electronics and Communication Society, Optical and Radio Division National Conference Papers (Volume 2).
) 272 incense is known.

Electrode 301 of bistable semiconductor laser 300 shown in FIG.
and 302 are supplied with injection currents 11 and 12, respectively), thereby causing one end 304 of the active layer 303 to
One of the two optical signals P and P2 input to the other end 305 stores one value, and the optical signal P is emitted from both ends of the active layer 303.

FIG. 4 is a diagram showing the characteristics of the bistable semiconductor laser 300 shown in FIG. 3. As shown in FIG. 4(,), the bistable semiconductor laser 300 shown in FIG. 3 has an incident light 1P1=Q,
When the injection current is 12 ”” 12 b, the injection current is 11
and the exit scene P. It has a hysteresis characteristic shown as 400 between the two, and two stable points A and B are shown by setting the value of the injection current i to 11b.

FIG. 4(b) shows the amount of incident light P1 and the output light iP when the injection current 12 = l2b. The bistable semiconductor laser 300 shown in FIG.
By setting the values of i and b to the values of i and b shown in FIG. 4(a), the characteristic shown by 401 is obtained. Here, the injection current l,
When the value of is set to 11 W as shown in FIG. 4(b), the bistable semiconductor laser 300 exhibits the characteristics indicated by 402.

On the other hand, as shown in FIG. 4(c), the bistable semiconductor radar 300 shown in FIG.
=i, injection current 12 and output light amount 2
It has a hysteresis characteristic 403 between b P and two stable points A and B are shown by setting the value of the injection current 12 to 12b. FIG. 4(d) shows the injection current 11=
11b is a diagram showing the relationship between the incident light amount P2 and the output light ftPo. In the bistable semiconductor laser 300 shown in FIG. 3, the value of the injection current 12 is shown in FIG. 4(c). 1
By setting the value to 2b, the characteristic shown by 404 is obtained. Here, the value of the injection current 12 is '2' as shown in FIG. 4(C).
When set to w, the bistable semiconductor laser 300 exhibits the characteristics indicated by 403. Point A in Figure 4 (,).

B represents the same point as the bottom points A and B in FIGS. 4(b) to 4(d), respectively.

FIG. 1 is a diagram showing an embodiment of the present invention.

In Figure 1, the same numbers as in Figure 3 are numbered 3.
The same components as in the figure are shown.

FIG. 2 is a time chart for explaining the operation of the optical memory shown in FIG. 1. According to FIG. 2, electrodes 301 and 302 of the bistable semiconductor radar 300 shown in FIG.
are supplied with injection currents 200 and 201 by variable constant current sources 100 and 101, respectively.
As a result, one end 304 and the other end 30 of the active layer 303
The value of one of the optical signals P and P2 inputted from the active layer 303 and shown as 202 and 203 in FIG. Emits light.

As shown in FIG. 4(b) and (d), the injection current 11
As long as ゜12 is i, b + 12b, respectively, even if the optical signals P1 and P2 of the light amount P and h''2h are incident on one end 304 and the other end 305 of the active layer 303, respectively, the twin shown in FIG. The stable semiconductor laser 300 holds the emitted light P at either the light amount o or "oh" according to the value written last time.

Here, as shown in FIG. 2 205 and 206, the injection current i
, p i2 in Figure 4 (a
).

When the angle is reduced to 11c*12° as shown in FIG. 4(b), the bistable semiconductor laser 300 becomes
, B is reset at any stable point, and the output light P
The amount of light becomes 0. After this, for example, as shown in FIG. 2 206, when the value of the injection current 12 is increased to '2w shown in FIG. can be set by the incident light P1 of the injection current 1. As long as the values of l and b are maintained, the optical signal P incident on one end 304 of the active layer 303
, has no effect on the set operation described above. That is, the semiconductor laser 300 shown in FIG. 1 responds to the optical signal P2 incident on the other end 305 of the active layer 303 during a period 206 in which the injection current l, maintains i, b and the value of the injection current 12 becomes '2w. The value is memorized, and from now on the injection current amount 1, 1
1b where each value of □ is 1 zl ″C
2b Holds its value for a limited time.

Similarly, the semiconductor laser 300 of FIG.
is 1□, and the value of the injection current i is 1. A period 2
07, an optical signal P incident on one end 304 of the active layer 303
, and thereafter hold the values as long as the values of the injection currents i4 and 1□ are '1bl' and 2b, respectively.

(Effect of the invention) As described above, the bistable semiconductor L/- shown in FIG.
-! ;) According to '300, two electrodes 301, 30
2, one end 304 of the active layer 303 and the other end 3
Which of the optical signals P1 + P2 respectively applied to 05 is selected and stored, and 1. An optical signal P0 can be emitted from one end 303 and the other end 305 of the active layer 303.

That is, the optical memory t writing method according to the present invention has the effect that bidirectional original memory operation can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of the optical memory shown in FIG. 1, and FIG. 3 is a bistable semiconductor laser used in the present invention. 4 is a diagram showing the characteristics of the bistable semiconductor laser shown in FIG. 3, and FIG. 5 is a sectional view showing a specific example of the bistable semiconductor laser used in the conventional optical memory. 6 is a diagram showing the characteristics of the bistable semiconductor laser shown in FIG. 5, FIG. 7 is a diagram showing the conventional optical memory enlightenment method, and FIG. 8 is a diagram showing the optical memory shown in FIG. 7. FIG. 2 is a diagram showing a timing chart for explaining the operation of FIG. In the figure, 100, 101 and 700 represent variable constant current sources, and 300 and 500 represent bistable semiconductor radars, respectively. Patent applicant: NEC Corporation, 7/'1-1 representative patent attorney: Susumu Uchihara 1. Figure 1 Figure 2 30/, 302: @ pole 303: Active layer Figure 4 (C) Po (d) Figure 5 Figure 7 70/: 5 [Soil layer Kabuto Figure 8]

Claims (1)

[Claims] (1) A bistable semiconductor laser in which the electrode is divided into two electrodes, a first and a second electrode, in the direction of the resonance axis, and first and second press-fit currents are supplied to the first and second electrodes, respectively. an optical memory configured with a first and a second variable current source, the first electrode side of the active layer of the bistable semiconductor laser is controlled by controlling the first and second injection current values independently of each other; An optical memory writing method characterized by storing the value of one of two optical signals incident from an end surface and a second electrode side end surface.