JPS62157014A - Optical logic element - Google Patents

Abstract

PURPOSE:To obtain an element which has a high-grade function and a large number of degrees of freedom, by receiving a part of the optical output of a double electrode semiconductor laser by a photodetector and feeding back positively it to the double electrode semiconductor laser. CONSTITUTION:If an optical input Pi is increased from 0 to P2 P4 P1 P3 continuously when an optical feedback rate (f) is relatively high and a triple stable point exists, the characteristic line of a photodetector 2 is moved right in the figure. An optical output P0 is in the level L first because light is not emitted, and the optical output P0 is switched from the level L to the level M when the optical input Pi exceeds P1, and the optical output P0 is switched from the level M to the level H when the optical input Pi exceeds P3. If the optical input Pi is reduced continuously, the optical output P0 is switched from the level H to the level M when the optical input Pi is smaller than P4, and the optical output P0 is switched from the level M to the level L when the optical input Pi is smaller than P2. Thus, this element can be used as a ternary storage element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical logic element that combines a two-electrode semiconductor laser and a photodetector.

[Conventional technology]

FIG. 7 is a schematic diagram showing an example of a conventional two-electrode semiconductor laser, in which 1 is a two-electrode semiconductor laser (hereinafter simply referred to as a semiconductor laser except where particularly necessary), 2 is an electrode, and Po
For example, is the optical output of the semiconductor laser], IN, and Ir injected into the electrode 2? It's the li style.

The conventional semiconductor laser 1 is configured as described above,
One current Ir is fixed at an appropriate value and the other current It'
It has been found through research by the present inventors that by changing , nonlinearity can be created in the gain characteristics above the threshold current. This is shown in the characteristic diagram of optical output versus injection current of the semiconductor laser 1 in FIG. 8(a).

[Problem that the invention seeks to solve]

Incidentally, the recent development of semiconductor device manufacturing technology has been remarkable, and the degree of integration is increasing year by year, and devices are becoming more dense and large-scale. However, even if we simply make each element smaller and increase the degree of integration, we have reached a level where we cannot obtain any benefits.

The first reason for this is that, as the degree of integration increases, the wiring inside the circuit board in which logic elements and memory elements are mounted becomes significantly more complex.

Second, as the size decreases, the problem of crosstalk between wires becomes more serious.

Thirdly, there is the problem of signal propagation delay. (Zunao) If the elements and wiring inside the chip are made even smaller,
The response of the element itself is faster in proportion to the tt6 fraction (however, the transmission delay time between elements does not increase and remains constant.The importance of light is widely recognized as a promising candidate to solve all of these problems. Many attempts have been made to replace computer elements with optical elements.

On the other hand, the minimum unit logic element is not a binary one, but a multi-value one (
(three values or more), the number of elements in the chip can be reduced for the required computational processing power. Naturally, since the number of wiring lines can be reduced, the above-mentioned problems are significantly alleviated. For these reasons, the realization of multi-level optical logic devices is eagerly awaited, but there are very few research reports, and in particular, there are no documents on semiconductor devices suitable for future integration.

This invention was made in order to solve the above problems, and by receiving a part of this optical output with a photodetector and feeding it back to the The objective is to obtain an optical logic element with the following functions.

On the other hand, as shown in the characteristic diagram in Figure 8(b), it is known that a bistable device can be created by combining a normal semiconductor laser whose gain is linear above the threshold voltage and a photodetector. (Optical bistable semiconductor laser, Hiroshi Koyo et al., Applied Physics, October 1983 issue.

Therefore, this invention corresponds to replacing one of these semiconductor lasers with one with special characteristics. [Means for solving the problem] The optical logic device according to the present invention has a structure in which the optical output increases with respect to the injected current at a current value equal to or higher than a threshold value due to a change in the transverse mode. It consists of a two-electrode semiconductor laser having nonlinearity and a photodetector that receives a part of the optical output of the two-electrode semiconductor laser and applies positive feedback.

[Effect]

A part of the optical output of the two-electrode semiconductor laser is received by a photodetector to provide positive feedback to the two-electrode semiconductor laser. The same reference numerals as in Fig. 7 indicate the same parts, 3 is photodetector'h: 4.4 is the T4 flow amplifier, Pl is the optical input to the photodetector 3, fP
o is a part of the optical output Po, and f is a part of the semiconductor laser 1.
This is an optical feedback rate indicating the proportion of the optical output Po that enters the photodetector 3.

Ip is a feedback current from the photodetector 3 to the semiconductor laser 1, and I)+ is a bias current.

First, the case where it is used as a light input and light output element will be described.

Part fP of the optical output Po from the semiconductor laser 1.

is received by the photodetector 3 and fed back to the current e through the current amplifier 4. The current Ir and the bias current Ib are fixed, and the optical input Pi to the photodetector 3 is varied.

The characteristics of the semiconductor laser 1 are simplified as shown in FIG.
rp 10'b Ij (L<Ip+Ib<L)
= M([2<lp +lb<Ia)=b(I
p 10 lb - Is) 10 M (13< Ip 10 Ib)
・・・・・・・・・・・・ (1) Here, a and b are the differential quantum efficiencies in the respective regions, I, , I2. I is a current corresponding to a bending point on the characteristic line of the optical output Po with respect to the injection current IJ of the semiconductor laser 1.

On the other hand, the characteristics of the photodetector 3 are also simplified as shown in FIG. 2(b), and the feedback current
(P i + Chi po<Psi=Ak Ps
(Ps(P i+f Po)・・・−・
−(2). Here, is the conversion coefficient of the feedback current Ip for the optical input P i of the photodetector 3, A is the current amplification factor of the amplifier 4, and Ps is the input optical power at which the output current of the photodetector 3 is saturated. be.

Although the relationship between the optical input P1 and the optical output Po can be understood by eliminating the feedback current ■ρ from the equations (1) and (2), the relationship between the optical input P1 and the optical output Po can be understood.However, to make it easier to understand, a graphical solution will be used.

FIG. 3 shows an example where the optical feedback factor f is relatively high and a triple stable point exists.

In this figure, o, , o2. o:l, o4 is semiconductor 1
Noser 1 injection = light output PO for 7th I p
The bending point on the characteristic line, e, , 12. el, 14 are the characteristic lines of the photodetector passing through the bending points 0+ -02-Oa and Oa, respectively, and Pl p P 21 P 3 p p 4 are the characteristics tl'+ + 1!, respectively. z + Rz r la
Light detection 'Give the characteristics of M43, human power light power, L,
M and H are output light power levels (hereinafter simply referred to as levels) in a region where the output light-human power characteristics are flat.

A stable point among the intersections of the characteristic line of the semiconductor laser 1 and the characteristic line of the photodetector 3 can be the operating point. Figure 3: Optical input Pi
When increasing continuously from 0 to P2→P4→P1→P3, the characteristic line of the photodetector 3 moves to the right in the figure. However, the saturation 'lt flow value A kP s remains unchanged.

At first, no light is emitted, so the optical output Po-=L, and when the optical input Pi exceeds Pl, the optical output is output. Po jumps from level L to level M, and when the optical input P1 exceeds P3, the optical output is output. P.

jumps from level M to level H. Next, when the optical input PI is continuously decreased, the moment the optical input P1 becomes smaller than P4, the optical output PO jumps to level 1 (mustard/bell M), and the optical input P1 becomes smaller than P2. Sometimes optical output PO
jumps from level M to level 1-. Also, when in Bell M, Pl is P4 and 1).

If the value is set between , the signal stays at M. The condition of B is shown in FIG. 4(a), and it is used as a ternary storage element. As a typical example of the opposite, when the optical feedback factor f is sufficiently low, the slope of the characteristic line changes and the input optical power becomes P1<P2<PJ<Pa, as shown in Figure 4(b). (The co-hysteresis phenomenon does not occur and the differential gain characteristic is obtained. In the figure, Pl and P
2, the line between P3 and P4 is drawn diagonally, but it is possible to make it almost perpendicular. P□ and P2
It is sufficient to make P3 and P4 substantially equal. This can be used as a three-value analog-to-denocle conversion element and a logical operation element. Depending on the values of the differential quantum efficiencies a, b and optical feedback rate [of the semiconductor laser 1], the magnitude relationship of the input optical powers P1 to P4 changes (except for the relationship P2<I'3), as shown in FIG. 4(a). As shown in ~ (poor), there are 12 cases in total. Figure 4 (,) shows triple stability, (b) shows differential gain in two places, (f) and (1) show special triple stability, (h) shows bistability, and (g) shows two places. Bistability, etc. (c) p (d) F (eL l), (k),
(e) has both bistability and differential gain property.

In order to monolithically integrate the optical logic element of this invention, specifically, for example, as shown in FIG.
and the photodetector 3 may be placed adjacent to each other on the same substrate (see the above-mentioned article by Mr. Koyo). In this case, current feedback should be performed inside the element.

In the above explanation, one of the 12 characteristics shown in Figure 4 was selected by changing the optical feedback rate (f in equation (2)), but in the case of this method, the characteristics shown in Figure 5 are as follows. It is difficult to change the characteristics of an integrated circuit after it has been created. Therefore, if we decide to change the current amplification factor (A in equation (2)), Figure 4 (
If the 12 characteristics a) to (b) are obtained, and the feedback current Ip from the photodetector 3 to the semiconductor laser 1 is routed through the outside, the characteristics can be selected from the outside after the integrated circuit is fabricated. It is also possible to use 5L. However, when changing the current amplification factor A, the output light P in FIG.

The level of [I will change.

Further, the device of the invention of B can also be used as a current/light output device. For this purpose, the optical input Pi shown in Fig.
is fixed (may be 0) and the bias current Ib is varied. In this case as well, characteristics almost corresponding to the 12 patterns shown in FIGS. 4(a) to (2) can be obtained, but the value of the top level H of the optical output PO does not change with respect to the bias current Ib. The only difference is that - As an example, the characteristics corresponding to FIG. 4(a) are shown in FIG.

〔Effect of the invention〕

As explained above, the optical logic element according to the present invention is
A two-electrode semiconductor laser has a non-cotton-shaped optical output with respect to the injected current at a current value above the threshold due to changes in the transverse mode, and a part of the optical output of this two-electrode semiconductor laser is received (7 Since the device is configured as a photodetector that provides positive feedback, various logic elements including a triple stable optical logic element made of semiconductor materials, which has never been seen before, can be used.The functions of the device of this invention will be described in detail. If you look at it, there are 12 ways, and it is up to you to decide which function to have among these.
It is very easy to use only 514 i'r of M, and the function can also be changed by changing the value of the current fixed as a parameter. It is a semiconductor material that can be stacked with 84 layers, and is highly functional and flexible. Optical logic element ri!
There are benefits that can be gained.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG. 2 (a
) is a diagram showing a simplified characteristic curve of a semiconductor laser.
Figure ()j) is a diagram showing a simplified characteristic curve of a photodetector,
Figure 3 is an explanatory diagram of the operation of the optical logic element in Figure 1, and Figure 4 (a
) to (poor) are diagrams showing the optical output characteristics with respect to optical input of the optical logic element in Figure 1, Figure 5 is a block diagram showing the case where the optical logic element of the present invention is integrated seven-dimensionally, and Figure 6. FIG. 7 is a schematic diagram showing an example of a conventional semiconductor laser, and FIG. FIG. 8(b) is a diagram showing the optical output characteristics with respect to the injection current of a normal semiconductor laser. In the figure, 1 is a semiconductor, 2 is an electrode, 3 is a photodetector,
4 is a current amplifier. Figure 1(a) (
b) IT +2 13 - If (lp÷lb)
-1p Figure 3 Yo AI: P1 Figure 4 (a) (b) (C) (d)
(e) (f) (9) (hl
(i) (i) (k) (+)
P+ p, P+ Figure 5 Figure 6 Ib

Claims (1)

[Claims] A two-electrode semiconductor laser whose optical output has nonlinearity with respect to the injected current at a current value equal to or higher than a threshold due to a change in the transverse mode, and a part of the optical output of this two-electrode semiconductor laser that receives light. and a photodetector that applies positive feedback.