JPH02235033A - Optical logic circuit - Google Patents

Abstract

PURPOSE:To reduce wiring and the number of elements and to realize low power consumption and fast operation by adding an optical filter on the output side of a semiconductor laser and performing exclusive OR operation according to a relation between the light intensity values of respective input light beams and a threshold value. CONSTITUTION:The optical logic circuit (exclusive OR circuit 11) is constituted of a two-electrode type semiconductor laser 12 which has a saturable absorption area 13 and an optical filter 14. When the sum of the light intensity, for example, input light beams A and B which are inputted to the laser 12 does not reach the threshold value P1, the laser 12 does not oscillate, so no output is generated. When the sum exceeds the threshold value P1, the laser 12 begins to oscillate with wavelength lambda2 to output light (wavelength-converted light) with light intensity P0 (>P1). Further, when the sum exceeds a threshold value P2, the laser 12 begins to oscillate with wavelength lambda1 and light (amplified light) with light intensity P0' is outputted. The laser output light is therefore guided to a filter (which transmits the light with the wavelength lambda2 and interrupts the light with the wavelength lambda1) 14. Denoting the output light as F(lambda2), the F(lambda2) is an EXOR output for A(lambda1) and B(lambda1). At this time, the intensity values Pi of the input light beams are P1 and P2/2<=Pi<P2.

Description

[Detailed description of the invention] Industrial field of application Prior art (Figs. 6 and 7) Problems to be solved by the invention Examples of means and actions for solving the problems Explanation of the principle of the present invention (Figs. 1 to 3) ) An embodiment of the present invention (Figures 4 and 5) Effects of the invention [Summary] Regarding optical logic circuits, EXOR operation can be obtained with a simple configuration, and low power consumption can be achieved by reducing the number of optical wiring and elements. The purpose is to provide an optical logic circuit that can shorten propagation time, improve level adjustment of optical input/output signals, and achieve high integration. A semiconductor laser that receives multiple input lights and has a saturable absorption region and an optical filter into which the output light of the semiconductor laser is input and which transmits only the predetermined wavelength-converted light, and the semiconductor laser has an optical filter that receives the output light of the semiconductor laser and transmits only the predetermined wavelength-converted light. outputs a predetermined wavelength-converted light, and outputs only amplified light for optical input having an intensity equal to or higher than a high-level second threshold value to attenuate the wavelength-converted light, The optical filter is added to the output side of the semiconductor laser, and the optical intensity Pi of each of the plurality of input lights input to the semiconductor laser is expressed as P l+(1
/2) P,≦p. <p. By doing so, it is configured to take the exclusive OR of the light input to the semiconductor laser. [Industrial Application Field] The present invention relates to optical logic circuits such as optical computers, and more particularly to an exclusive optical OR circuit suitable for low power consumption and high-speed operation, and an optical half-adder circuit that is an application thereof.

Reduce the number of components of the half adder, which is the basic arithmetic circuit,
Reducing the noise level of wiring is important for optical computers as well as for electronic computers in order to achieve lower power consumption and higher speeds.

[Conventional technology]

As shown in FIG. 6, half adder 1 is a device that outputs sum bit F and carry bit C from the input of addition bit A and augend bit B, and its truth table is as shown in Table 1. become. Carry bit C corresponds to the AND output of A and B, and sum bit F corresponds to the EXOR (exclusive OR) output of A and B.

(This page, blank space below) Table 1 Truth table of half adder AND EXOR FIG. 7 is a diagram showing an example of the configuration of a conventional optical half adder using a semiconductor laser. In this figure, 2 is an optical half adder, and the optical half adder 2 combines optical waveguides 3 to 5 having branches and spatial intersections, and an AND function using an AND function of a semiconductor laser.
type optical logic elements 6 to 9, and input optical signal A.
, B to the optical half adder 2, a sum output optical signal F and a carry output optical signal C can be obtained. [
[Problems to be Solved by the Invention] However, in optical logic circuits using such conventional semiconductor lasers, AND, NAND, OR, etc. can be generated depending on the bias current settings and signal level settings.
Although it is possible to realize NOR and NOT operations, EXOR (exclusive OR) operation has not yet been achieved, so such AND-type optical logic elements can be used to create arithmetic circuits, such as adder circuits. There was a problem in that when trying to assemble a multiplication circuit, a very large number of elements were required.

For example, in order to realize an optical half adder using a conventional semiconductor laser, as shown in FIG. It is necessary to couple the optical waveguides 3 to 5 with each other. This has led to problems such as an increase in power consumption due to an increase in the number of elements, difficulty in integration due to the convergence of optical wiring, complexity in adjusting the level of optical input/output signals, and an increase in propagation delay time. .

Therefore, the present invention can obtain EXOR operation with a simple configuration, and by reducing the number of optical wiring and elements, it achieves lower power consumption, shorter propagation time, improved level adjustment of optical input/output signals, and higher integration. The purpose is to provide an optical logic circuit that can perform [Means for Solving the Problems] In order to achieve the above object, an optical logic circuit according to the present invention receives a plurality of input lights, a semiconductor laser having a saturable absorption region, and an output light of the semiconductor laser, an optical filter that transmits only predetermined wavelength-converted light, and the semiconductor laser outputs predetermined wavelength-converted light in response to an optical input having an intensity equal to or higher than a low-level first threshold;
The device outputs only amplified light for optical input having an intensity equal to or higher than a high-level second threshold value and quenches the wavelength-converted light, and the optical filter is installed on the output side of the semiconductor laser. The light intensity P4 of each of the plurality of input lights added and input to the semiconductor laser is P. , (1/2)P! ≦
By setting pt<pg, the exclusive OR of the light input to the semiconductor laser is performed. [Function] In the present invention, an optical logic circuit is configured by a semiconductor laser having a saturable absorption region and an optical filter having a wavelength selection function.

Therefore, for example, the input A input to the semiconductor laser
When the sum of the light intensities of and B does not reach the threshold value P1, the semiconductor laser does not oscillate and does not output any output. Input A
When the sum of the light intensities of and B exceeds a threshold value P, the semiconductor laser starts oscillating at a wavelength λ8 (≠λ1) and outputs light with an optical intensity Pi (>P,). Further, when the sum of the optical intensities of inputs A and B exceeds the threshold value P2, the semiconductor laser starts oscillating at the wavelength λ1, and the optical intensity P6'
Outputs (po) light. Therefore, the output light of the semiconductor laser is guided to the optical filter that transmits the wavelength λo and does not transmit the wavelength λ1, and the optical output from the optical filter is
(λ2), then F(λ is A(A.), B(λ.)
It becomes EXOR output for . [Example] The present invention will be described below based on the drawings.

Figures 1 to 3 are diagrams for explaining the principle of the present invention.
Figure 1 is its input/output characteristic diagram, Figure 2 is its overall configuration diagram,
FIG. 3 is a diagram showing the relationship between the light intensity and wavelength.

As mentioned above, exclusive OR
If an optical circuit (OR:, EXOR) can be realized with a single optical element by utilizing wavelength conversion/wavelength selection characteristics, it can be expected to simplify optical wiring, shorten propagation delay time, and lower power consumption in optical arithmetic circuits.

The inventor has developed an optical input with a low oscillation threshold (wavelength λ
For 1), we have discovered that wavelength-converted light (wavelength λ2) is output, and for high-level optical output (wavelength λ1), only amplified light (wavelength λ1) is output to attenuate the wavelength-converted light. ．． Figure 1 shows a DFB with wavelength λ1 -1.5374 am!
/- laser light is injected into a wavelength conversion laser via a variable optical attenuator, and the intensity and spectrum of the output light are measured. The oscillation wavelength λ2 of the wavelength conversion laser used in the experiment
is variable within the range of 1.5351 to 1.5391 μm, and FIG. 1 shows the optical input/output characteristics when λ2 =1.5391 μm. As shown in the figure, when there is no optical input, there is no optical output. When the input light intensity Pin is slightly increased, the wavelength conversion laser starts oscillation, and even if Pin is further increased, the output light intensity Pout remains constant within the range below a certain value.If the input light intensity Pin is increased, the wavelength conversion laser starts oscillating. The amplified light indicated by the middle broken line continues to increase, and a state is reached where the wavelength-converted light indicated by the solid line in the figure loses its gain and disappears. When Pin is lowered again, the amplified light decreases and the wavelength-converted light oscillates. In the figure, the hunting region is a region where the intensity of the wavelength-converted light oscillates due to mode competition with the amplified light.

From the above results, by adding a selective transmission filter with wavelength λ2 to the output end of the wavelength conversion laser, the wavelength converted light F(
If only λ2) is output, two human power lights A(λ1) and B(λ
For 1), an optical EXOR function can be realized.

For example, in the case of two people, the "l" level of one input light is 0.5 mW (actually, Q,5 mW ~ 0.8 mW
), when there is one input, the output is O, and when both inputs are not input, and when both inputs are input, the output is L. EXOR operation is performed. .

FIG. 2 is a diagram showing an exclusive OR circuit consisting of a semiconductor laser having a saturable absorption region and an optical filter having a wavelength selective transmission function. In FIG. 2, 11 is an exclusive OR circuit (optical logic circuit), and the exclusive OR circuit 11 receives the lights A and B of wavelength λ1, and the saturable absorption region
A two-electrode semiconductor laser (semiconductor laser) 12 having 3
and a wavelength filter 14 that receives the output light of the two-electrode semiconductor laser 12 and transmits only light of a predetermined wavelength.

Two-electrode semiconductor laser 12 having a saturable absorption region l3
When the bias current 1b just before oscillation is applied and the lights A and B with the wavelength λ1 are input, the results are shown in Fig. 3(a) to (f).
) shows the input/output characteristics as shown below. Figure 3(a)(b)
are the input and output intensity characteristics when the sum of the light intensities of inputs A and B is smaller than the threshold value P1 (A + B < P +), and (c) and (d) in the same figure are the input and output intensity characteristics when the sum of the light intensities is smaller than the threshold value P1 (A + B < P +). Threshold PZ is greater than threshold P1 (P, < P
i and PZ<2Pl) smaller than (P+ <A+B<P
2) The input and output intensity characteristics in the case (e) and (f) of the same figure show that the sum of the light intensities is greater than the threshold P2 (A+B>Pz)
Input and output intensity characteristics are shown for each case, where λ1 represents the wavelength of input light, and λ2 represents the oscillation wavelength of the wavelength conversion laser (two-electrode semiconductor laser 12) itself.

When the sum of the light intensities of inputs A and B does not reach the threshold value P1, the two-electrode semiconductor laser 12 does not oscillate and does not output any output, as shown in FIG. 3(b). Figure (c) (
As shown in d), when the sum of the optical intensities of inputs A and B exceeds the threshold value P, the two-electrode semiconductor laser 12 has a wavelength of λ.
2 (≠λ1), and its optical intensity Po (>P
1) Outputs the light. Furthermore, as shown in (e) and (f) of the same figure, when the sum of the optical intensities of inputs A and B exceeds a threshold value P2, the two-electrode semiconductor laser 12 suppresses the oscillation at wavelength λ2 and oscillates at wavelength λ1. By amplifying the light, the light intensity p
It outputs light of o' (A/Pll). Therefore, the output light of the two-electrode semiconductor laser 12 is guided to the optical filter 14 that transmits the wavelength λ2 and does not transmit the wavelength λ1,
If the optical output from the optical filter 14 is F (λ2), then F
(λt) becomes an EXOR output for A(λI) and B(λI). On the other hand, if the output light of the semiconductor laser 12 is guided to the optical filter 14 that transmits the wavelength λ1 and does not transmit the wavelength λ2, and the optical output from the optical filter 14 is C(λl), then C(λ,) is A( AN for λI), B(λ,)
It becomes D output.

Therefore, in the present invention, as shown in Table 2, the optical input A(λ
AND optical output C(λ1), E for l), B(λl)
The xOR output F(λ2) can be obtained, and an EXOR circuit or an AND circuit can be created using one semiconductor laser and one optical filter.

Table 2 Optical logic operation of the present invention AND EX(E)-R Two juF cells Hereinafter, embodiments will be described based on the above basic principle. Fourth
The figure is a diagram showing an embodiment of the optical logic circuit according to the present invention, and is a sectional view showing the structure of the exclusive optical OR circuit. In this example, an InGaAsP/InP semiconductor laser is
This is an example of integration on a substrate.

In FIG. 4, 21 is an exclusive optical logical sum circuit (optical logic circuit), and the exclusive optical logical phase circuit 21 is a two-electrode semiconductor laser (semiconductor laser) 2 having a saturable absorption region 23.
2 and a distributed feedback semiconductor laser (optical filter) 24 having a wavelength filter function are integrally formed on an InP substrate. Hereinafter, common parts of the two-electrode semiconductor laser 22 and the distributed feedback semiconductor laser 24 will be described with the same reference numerals. 2-electrode semiconductor laser 2
2 is an n-type electrode 25 made of Au-AuGe and an n-type In
A P substrate 26 and an optical waveguide layer (
Wavelength λ. Electrical contact is made between the cladding layer 28 made of n-type 1nP (wavelength λ, = 1.3 μm) 27, the active layer (wavelength λ, = 1.55 μm) 29 made of InGaAsP, and the cladding layer 30 made of p-type InP. a contact layer 31 made of P-type 1nGaAsP for improving
A bias current rb is injected into the active layer 29 directly under the P-type electrodes 32 and 33, which becomes a gain region.
The active layer 29 without the type electrodes 32 and 33 serves as a saturable absorption region 23 to which no current is injected.

The distributed feedback semiconductor laser 24 has an n-type electrode 25 and an n-type 1
An nP type substrate 26, a diffraction grating 34 with a depth of 400 and a period of 2400, an optical waveguide layer 27, a grading layer 28, an active layer 29, a grading layer 30, a contact layer 31,
Si. N. It is composed of anti-reflection coating films 35 and 36 consisting of P-type electrodes 37. In the figure, Ib is the saturable absorption region 2
3 and the bias current of the semiconductor laser 22 having I
F is a bias current of the distributed feedback semiconductor laser 24 having a wavelength filter function.

By appropriately setting I2, the wavelength to be transmitted can be selected. Further, rb is biased immediately before laser oscillation.

In addition to the embodiment shown in FIG. 4 as the optical filter for wavelength selection, for example, a silica-based Matsuha-Zehnder type interference optical waveguide can also be used.

FIG. 5 shows a configuration example of an optical half adder using an exclusive OR circuit 21, in which input optical signals A and B are combined and inputted to an AND type optical logic element and an EXOR type optical logic element through a distributor. By doing this, a sum output optical signal F and a carry output optical signal C can be obtained.

As described above, according to this embodiment, EXOR operation can be obtained by connecting the semiconductor laser 22 and the optical filter for wavelength selection (distributed feedback semiconductor laser 24), and as shown in FIG. You can make an optical half adder. Therefore, compared to the conventional EXOR circuit and optical half adder 2 shown in FIG. 7, the optical half adder can be made simpler with fewer optical wirings, and thus a smaller optical half adder with lower loss and lower power consumption can be realized. In addition, since the number of cascaded elements is reduced, a human-powered boat (
The propagation time from A, B) to the output boat (C, F) can be shortened, making it suitable for high-speed operation. Furthermore, since the number of branching and merging of light is small, it becomes extremely easy to adjust the light input/output level at the intermediate portion.

Furthermore, it is now possible to form an array of semiconductor lasers and wavelength selection filters and optically couple them, making it suitable for integration and ease of assembly in hybrid actual equipment.

〔Effect of the invention〕

According to the present invention, EXOR operation can be obtained with a simple configuration, and by reducing the number of optical wiring and elements, power consumption is reduced, propagation time is reduced, level adjustment of optical input/output signals is improved, and high integration is achieved. can be achieved.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams for explaining the principle of the present invention. Figure 1 is its input/output characteristic diagram, Figure 2 is its overall configuration diagram, and Figure 3 is the relationship between the intensity and wavelength of the outgoing light. 4 and 5 are diagrams showing an embodiment of the optical logic circuit according to the present invention, FIG. 4 is a cross-sectional view showing its structure, and FIG. 5 is a configuration example of a half adder thereof. Figures 6 and 7 are diagrams showing conventional optical logic circuits, Figure 6 is a diagram for explaining the operation of the half adder, and Figure 7 is an example of the configuration of the half adder. FIG. l1...Exclusive OR circuit (optical logic circuit), 1
2...Two-electrode semiconductor laser (semiconductor laser)
13... Saturable absorption region, l4... Optical filter, 2l... Exclusive OR circuit (optical logic circuit), 2
2...Two-electrode semiconductor laser (semiconductor laser)
23... Saturable absorption region, 24... Distributed feedback semiconductor laser (optical filter) 25... N-type electrode, 26... N-type InP substrate , 27... optical waveguide layer, 28, 30... ground layer, 29... active layer, 31... contact layer, 32, 33, 37... ...P-type electrode, 34...
...Diffraction grating, 35, 36... Anti-reflection coating film. Ib・
... Semiconductor laser 2 having a saturable absorption region 23
2, bias current of the distributed feedback semiconductor laser 24 having a wavelength filter function. (a) A+B<Pi (b) (e) A+B>Pi<2P, (f) Diagram showing the relationship between crowd intensity and wavelength for explaining the principle. A diagram showing an example of the configuration of a half adder according to an embodiment.

Claims (1)

[Claims] A semiconductor laser that receives a plurality of input lights and has a saturable absorption region; and an optical filter that receives output light of the semiconductor laser and transmits only predetermined wavelength-converted light, The semiconductor laser outputs predetermined wavelength-converted light in response to an optical input having an intensity equal to or higher than a first low-level threshold, and outputs a predetermined wavelength-converted light to an optical input having an intensity equal to or higher than a high-level second threshold. On the other hand, it outputs only the amplified light and attenuates the wavelength-converted light, and the optical filter is added to the output side of the semiconductor laser, and each of the plurality of input lights input to the semiconductor laser is Light intensity P_i is P_1, (1/2)P_2≦P_i<P_2
An optical logic circuit characterized in that an exclusive OR of light input to the semiconductor laser is calculated by doing so.