JPH0277030A - Optical logic circuit - Google Patents

Abstract

PURPOSE:To enable exclusive OR, AND, and adding operations by providing a state separator which separates the output light of an optical multistable element and outputs it to respective output terminals. CONSTITUTION:A light input 11 which is inputted to the 1st input terminal of an optical multiplexer 13 and a light input 12 which is supplied to a 2nd input terminal are multiplexed and entered into an optical multistable semiconductor laser 14. The light output of the optical multistable semiconductor laser 14 is entered into a wavelength filter 15, branched according to the wavelength of the light output, and sent out from output terminals 16 and 17 as light outputs 18 and 19. Consequently, the exclusive OR, AND, and half-adding operations are performed by a simple optical system.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is suitable for use in optical communication systems, computers, etc. Regarding circuits.

[Prior Art] As a method for optically calculating exclusive OR, for example, IEEE Journal of Phantom Electronics, Volume 19, Ultra First All Gates 1 (Journal
of Quantum Electronics,
QE-19, pp.

1719-1723 (1983), “An ul
tra fast all-optical gate
Branch interference type LiNbO as reported in
An example of using the nonlinear refractive index change caused by the optical pulse signal of a three-light modulator, and Applied Physics Letters Volume 44, ``Uses of a Single Nonlinear Fabry Perot Etalon As・Optical logic gate J (Applied Phys
ics Letters, 44. pp.

172-174. (1984), Use of
a single nonlinearFabl
y-Perot etalon as opti
There is an example of a nonlinear etalon that utilizes a shift in the transmission characteristics caused by an optical pulse signal of a Fabry-Béro resonator that includes a nonlinear optical medium in the resonator, as reported in ``Cal Logicgates''.

Further, as an example of using an optically active element, there is an example (Japanese Patent Application No. 140540/1982) in which a bistable semiconductor laser and a semiconductor optical switch are combined as shown in FIG. Here, the optical input 51 and the optical input 52 are connected to the bistable semiconductor laser 5.
3 and the semiconductor optical switch 54. The bistable semiconductor laser 53 outputs the logical product of the optical inputs 51 and 52, and the output is input to the control input terminal 55 of the semiconductor optical switch 54. This semiconductor optical switch 54 is
When the control input terminal 55 has optical input, the signal input terminal 5
The optical signal inputted to the signal input terminal 56 is outputted to the output terminal 57, and when there is no optical input to the control input terminal 55, the optical signal inputted to the signal input terminal 56 is outputted to the output terminal 58. As a result, the logical product of the optical input 51 and the optical input 52 is output to the output terminal 57, and the logical product of the optical input 51 and the optical input 52 is output to the output terminal 58.
The exclusive OR with is output. In the figure, 59 and 60
is an optical splitter, and 61 and 62 are optical multiplexers.

[Problem to be solved by the invention]

However, in the example using the above-mentioned branching interference type LiNbO3 optical modulator, an optical input of at least several watts or more is required, which necessitates an increase in the size of the light source, which has the drawback of high power consumption.

Additionally, since nonlinear etalons utilize the resonance characteristics of a Fabry-Béro resonator, they have the disadvantage of requiring stabilization of the absolute frequency of the light source, a single longitudinal mode, and stabilization of the resonator characteristics. be.

Next, the conventional example in which a bistable semiconductor laser and a semiconductor optical switch are combined requires extremely complicated optical wiring and two types of semiconductor optical elements, resulting in a very complicated optical system.

Therefore, an object of the present invention is to solve the above problems and to enable exclusive OR, logical product, and addition operations over a wide wavelength range and with input light of low incident light intensity with a very simple configuration. The purpose of this invention is to provide an optical logic circuit.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a first optical input input to a first input terminal and a second optical input input to a second input terminal. The output of the optical multiplexer is input to the optical multiplexer that combines the optical input of
An optical multistable element that transitions between two stable states and the output of the optical multistable element are input, and the output light of the optical multistable element is separated depending on which of the three stable states the output light takes. First. It is characterized by comprising a state separator that outputs to the second and third output terminals.

Here, the optical multistable element changes its output optical state between a state of no optical output, a state of the first wavelength, and a state of the second wavelength according to the input optical intensity. It can be an optically multistable semiconductor laser.

Alternatively, the optical multistable element may have an output optical state between a first wavelength, a second wavelength, and a third wavelength depending on the input optical intensity. It is also possible to use an optical multistable semiconductor laser that transitions.

Further, the state separator may be a wavelength filter.

(Operation) When there is no input light, the output light of the optical multistable element takes a first stable state and is output from the first output end of the state separator.First and second inputs Out of the light
When only one of them is input, the output light takes a second stable state and is output from the second output terminal of the state separator. When the first and second input lights are input simultaneously, the output light takes a third stable state,
It is output from the third output terminal of the state separator.

Therefore, the exclusive OR of the first and second input lights is obtained at the second output, and the AND of the first and second input lights appears at the third output. A half adder can now be constructed.

The optical multistable element changes its output optical state between a state of no optical output, a state of light of a first wavelength, and a state of light of a second wavelength, depending on the input light intensity. In the case where the state separator is a wavelength filter, the wavelength filter only needs to have two output ends, a second and a third output end.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. Here, the optical input 11 input to the first input end of the optical multiplexer 13
and the optical input 12 inputted to the second input terminal as well.
The light is multiplexed by the optical multiplexer 13 and input to the optical multistable semiconductor laser 14 . The optical output of this optical multistable semiconductor laser 14 is incident on a wavelength filter 15, branched according to the wavelength of the optical output, and output as optical outputs 18 and 19 from output ends 16 and 17, respectively.

FIG. 2 shows an example of the optical multistable semiconductor laser 14. This optical multistable semiconductor laser 14 is an electrode-divided distributed feedback type laser diode having a uniform diffraction grating 28, in which the electrode is divided into a plurality of parts in the direction of the resonator, and the carrier density inside the resonator can be controlled independently of each other. It is composed of a semiconductor laser 21.

The example in FIG. 2 shows a configuration with electrodes 22 and 23 divided into two. If the region 24 to which current is supplied from the electrode 22 is a saturable absorption region in a low injection current state, the optical output 27 of this device exhibits multistage stability characteristics with respect to the current flowing through the electrode 23, as will be described later. It becomes like this. In addition,
29 is an active layer.

This situation is shown in FIG. Rapid increase in first light output 3
1 is caused by sudden laser oscillation due to absorption characteristics of the region 24 to which the current is supplied from the electrode 22 being saturated by light generated in the region 25 to which the current is supplied from the electrode 23. Also, a rapid increase in the second light output 32
As the gain distribution and refractive index distribution of the resonator change with the change of the current flowing through the electrode 23, the dominant two
This is due to the switching of the oscillating longitudinal moat, which occurs due to the reversal of the gain between the two longitudinal modes. Therefore, the region 33 shown in FIG. 3 oscillates in the first longitudinal oscillation mode, and the region 34 oscillates in the second longitudinal oscillation mode.

Regarding the bistable characteristics based on absorption saturation in semiconductor lasers, see Electronics Letters Part 1.
Volume 7, r Bistable Operations of Semiconductor Lasers Pi Optical Injection 1 (Electronics Letter
s, 17. pp, 741-742 (1981)”B15
table 0operation of Sem1co
ndductorLasers by 0ptical
In addition, switching by injection current control between the two dominant longitudinal modes of a distributed feedback semiconductor laser with a uniform diffraction grating is described in Applied Physics Letters No. 51@ Applied Physics
Letters 51. pp, 1777-1779 (1
987), “Electro-cptical Io
3ic operations with tw
o electrodistributed f
eed-back 1njc'ction 1aser
s”).

In order to operate this device as an optical multistable device, the current supplied to the electrode 23 in FIG.
Set to . In this state, a light input 26 is inputted into the active layer 29 from the end face of the electrode-divided distributed feedback semiconductor laser 21 on the electrode 22 side. When the optical intensity of the optical signal 26 exceeds a certain threshold, the absorption characteristics of the region 24 are saturated by the optical input 26, and laser oscillation in the first oscillation mode suddenly rises. When the light intensity further increases, the gain distribution and refractive index distribution of the resonator change, and the oscillation mode switches to the second oscillation mode. In this way, the optical input 26
In the characteristics of the optical output 27, multistage stable characteristics with different oscillation wavelengths appear.

An example of this characteristic is shown in FIG. 4(a). Here, when the intensity of the optical input 26 takes the first threshold P1, rapid laser oscillation starts in the first oscillation longitudinal mode, and at the second threshold P2, the laser oscillation starts from the first oscillation longitudinal mode. The oscillation mode switches to the second oscillation longitudinal mode, and a rapid increase in optical output occurs accordingly.

Since the first oscillation longitudinal mode and the second oscillation longitudinal mode have different oscillation wavelengths, they can be separated by the wavelength filter 15. In the following, the separated first oscillation band moat,
and the optical output of the second oscillation longitudinal mode will be explained as the optical output of the first optical output ends 16 and 17 of the wavelength filter 15 in FIG. 1, respectively.

The characteristics of the optical output separated in such a wavelength region are expressed as
Figures 4(b) and 4(c) are plotted along the same horizontal axis as in Figure (a). Now, as shown in FIG. 4(d), the first optical input in FIG. 1! The light intensities P of the first and second optical inputs 12 are set to satisfy 2P>P2>P>P+. When only one of the optical inputs 11 and 12 is input to the semiconductor laser 21, it oscillates in the first oscillation longitudinal mode, so the optical output 18 is at pi level, and when both are input at the same time, both Since the sum of the light intensities exceeds P2, oscillation occurs in the second oscillation longitudinal mode, and the light output 19 becomes high level. In this way, the first wavelength filter 15 in FIG.
The exclusive OR of the optical inputs 11 and 12 is output to the optical output 18, and the optical output 19 outputs the exclusive OR of the optical inputs 11 and 12.
The logical AND with 2 is output.

Further, by setting the optical output 18 as an addition output and the optical output 19 as a carry output, this optical logic circuit operates as a proactive adder. Here, since absorption saturation is used as the operating principle, it is possible to operate for optical input in a wide wavelength range of at least 10 nm or more. In addition, the required incident light intensity is very small, less than milliwatts.

As the wavelength filter 15 in this example, a diffraction grating, an interference film filter, or an interferometer based on various principles can be used. Furthermore, the optical multistable semiconductor laser 21 may utilize the mode hopping phenomenon between the three oscillation longitudinal modes of a Fabry-Bero type semiconductor laser.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, since the configuration uses a photon stabilizing element and a state separator, a very simple optical system can perform exclusive OR, logical product, and half Addition can be performed. Furthermore, if a split-electrode distributed feedback semiconductor laser with a uniform diffraction grating is used as a photon stabilizing element and a wavelength filter is used as a state separator, a wide wavelength range of at least 10 nm or more and a low wavelength of less than milliwatts can be obtained. It has the advantage of being able to operate satisfactorily with a light input of incident intensity.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a perspective view showing an example of an electrode split distributed feedback semiconductor laser having a uniform diffraction grating, and Fig. 3 shows electrodes having a uniform diffraction grating. A characteristic diagram showing an example of the characteristics of injection current versus output light intensity of a split distribution feedback semiconductor laser. Figure 4 shows the characteristics of input light intensity versus output light intensity of a split electrode distribution feedback semiconductor laser with a uniform diffraction grating. Explanatory diagram: FIG. 5 is a configuration diagram showing a conventional example. 11, 12... Optical input, 13... Optical multiplexer, 14... Multistable semiconductor laser, 15... Wavelength filter, 16.17... Output end, 18.19-... Optical output . Figure 1: λ force 26 electrodes, 26 electrodes, 26 electrodes

Claims (1)

[Claims] 1) an optical multiplexer that multiplexes a first optical input input to a first input terminal and a second optical input input to a second input terminal; an optical multistable element to which the output of the optical wave generator is input, and the state of the output light transitions between three stable states according to the input light;
and a state separator that separates the output light of the optical multistable element depending on which of the two stable states it takes, and outputs it to the first, second, and third output terminals. optical logic circuit.