JP2827379B2 - Optical neuro element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neural element for performing pattern recognition and associative processing of information at a high speed, and more particularly, to an optical neural element using parallel operation by an optical waveguide. Things.

[Prior art] A neurocomputer that simulates an excellent information processing function of a biological system is relatively easy to process associative, learning, pattern recognition, combination optimization problems, etc., which are difficult with a conventional von Neumann-type computer. It is said that it can be realized. The basis of a neurocomputer excellent in intelligent information processing functions such as association, inference, learning and the like is parallel processing, and information is accumulated in connection strength between elements called many neurons. This means that the conventional neurocomputer has good matching with light having spatial parallelism, and as shown in FIG. 8, an optical mask 81, a light receiving element 82, a comparator
83, one neuron is optically formed by the light emitting element 84,
Optical wiring between neurons is realized using a matrix-shaped optical mask 81. The excitation state of each neuron corresponds to the blinking state of the LEDs 84 arranged in a line. The output V _j (j = 1, 2,... N; N is the number of neurons) from each light emitting element 84 is wavefront transformed into a fan-shaped beam using a lens system (not shown), and is converted into a coupling intensity matrix T _ij . Only the j-th column component of the corresponding optical mask 81 is uniformly irradiated. T
_ij is calculated by using, for example, accumulated information vectors V ^(A) , V ^(J) , and V ^(E) representing A, J, and E shown in FIG. When the magnitude of T _ij is given as the light transmittance of the optical mask 81, the output light intensity is proportional to T _ij V _j . Next, all the i-row components of the output light from the optical mask 81 are focused on one of the light receiving element arrays 82 by a lens system (not shown). Therefore, the i-th light receiving element output u
_i is And a matrix-vector product is obtained at the output of the light receiving element.
The signal photoelectrically converted by the light receiving element array 82 is subjected to threshold processing by the comparator 83, and is fed back to the LED array 84.
By this repetitive operation, for example, for the incomplete input 85, the most similar A among the accumulated complete information A, J, E is selected, and a complete output 86 is obtained. In practice, the matrix T _ij is bipolar having positive and negative components corresponding to excitatory and inhibitory synaptic connections, and therefore only T _ij ^(+), which is a collection of only positive components of T _ij , and only negative components Using a two-channel optical system corresponding to the collected T _ij ^(-) , the difference between them is taken before the comparator 83. Also, an optical neuro device using a thin film waveguide as described in Miyazaki, 1989 IEICE Spring National Convention SD-1-6 and Miyazaki, 1989 IEICE Autumn National Convention D-217. Has also been proposed.

[Problem to be Solved by the Invention] However, since this optical neurocomputer is composed of individual optical components such as a light emitting element, a light receiving element, and an optical mask, the dimensions are large, the optical axis adjustment is troublesome, and mass production is difficult. And reliability problems. Further, the pattern of the optical mask is fixed, and its application range is limited in advance, and there is a problem that it cannot be applied to other applications.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A surface acoustic wave is applied to a plurality of light fluxes, each of which has been intensity-modulated, and the refractive index of the waveguide surface is perpendicular to the light propagation direction. The parallel operation is performed by focusing and detecting the light beam by the light focusing waveguide having distribution in the direction, and the purpose is to integrate the optical components on one substrate, An object of the present invention is to provide an optical neuro element which is small in size, does not require optical axis adjustment, is excellent in mass productivity and reliability, and can cope with various kinds of processing by controlling surface acoustic waves.

[Means for Solving the Problems] To achieve this object, an optical neuron device according to the present invention includes a light source that emits a plurality of light beams, a light modulation unit that modulates the intensity of each of the light beams, and diffracts each of the light beams. A single surface acoustic wave excitation means for exciting surface acoustic waves for
A light converging waveguide for condensing a light beam diffracted by the surface acoustic wave, a plurality of light receiving elements for detecting the condensed light beam, and a unit for performing threshold processing on an output signal from the light receiving element And

[Operation] In the optical neuron device of the present invention having the above-described configuration, a plurality of light beams emitted from the light source are modulated by the incomplete input signal by the light modulation unit. When a surface acoustic wave is applied to the plurality of modulated light beams, the light is diffracted in a direction of an angle corresponding to the frequency of the surface acoustic wave with a diffraction intensity corresponding to the intensity of the surface acoustic wave. After converging the diffracted light components diffracted in the same direction from different light beams to one point by the light focusing waveguide, and the diffracted light components diffracted in the other direction are condensed to the other point,
Each is detected by a light receiving element. As a result, a vector given by the intensity of the light beam and a matrix given by the intensity of the surface acoustic wave are calculated, and the result is given by the output of the light receiving element. The output of the light receiving element is subjected to threshold processing, and is fed back to the light modulating means to perform feedback. By this repetition processing, the most similar to the incomplete input among the stored complete information is obtained as a complete output.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of an optical neuron element 11 according to the present invention. The optical neuron element 11 includes a slab type waveguide 12, an optical focusing waveguide 13, semiconductor lasers 14a, 14b, 14c, a collimator lens 15a, 15b, 15c, comb-shaped electrode 1 for exciting surface acoustic waves
6. Light receiving elements 17a, 17b, 17c for detecting light diffracted by the surface acoustic wave and condensed by the light-converging waveguide 13, and comparators 18a, 18b, 18c.

The light focusing waveguide 13 is made of LiNb as shown in FIG.
_On a crystal substrate 26 of O ₃ or the like, a metal 28 such as Ti is formed by a sputtering method so that the film thickness distribution becomes larger toward the center. Thereafter, the waveguide 13 having a refractive index distribution as shown in FIG. Incidentally, the film thickness distribution of Ti28 shown in FIG.
And a shadow mask method of performing sputtering. Light waves emitted from a point light source propagating through such a gradient index waveguide are shown in Yamauchi, Miyazaki,
As described in IEICE MW84-128, it can be used as a light-converging waveguide because it is condensed every certain length and propagates as a periodic beam as shown in FIG.

In FIG. 1, semiconductor lasers 14a, 14b, 14
The light emitted from c becomes parallel light beams 31a, 31b, and 31c by collimator lenses 15a, 15b, and 15c such as Selfoc lenses, and propagates through the slab waveguide 12. Slab type optical waveguide 12
Can be easily produced by uniformly diffusing Ti into a substrate such as LiNbO ₃ as is well known.
The current flowing through the semiconductor lasers 14a, 14b, 14c is incompletely input to 32a, 3
2b, the light flux 31 having by controlling the magnitude corresponding to 32c, incomplete input 32a, 32b, the intensity V _1, V _2, V ₃ corresponding to 32c
a, 31b and 31c are obtained.

The light beams 31a, 31b, 31c are diffracted by the surface acoustic waves excited by the comb electrodes 16. As shown in FIG.
The strength of the surface acoustic wave 41 is represented by the coupling strength matrix T _i1 , T _i2 , T
By modulating the intensity of the surface acoustic wave 41 so as to _i3, theta _i angle diffracted diffracted light of, 33a, 33b, the strength of the 33c, respectively _{T i1 V 1, T i2 V} 2, T i3 the V _3. Here, by changing the frequency of the surface acoustic wave 41, the diffraction angle θ _i
Can be changed.

The diffracted lights 33a, 33b, 33c are collected while propagating through the light-converging waveguide 13 as shown in FIG. The intensity of the collected light is the sum of the intensities of the diffracted lights 33a, 33b, 33c: u _i = T _i1 V ₁ + T _i2 V ₂ + T _i3 V ₃ (3) By changing the frequency of the surface acoustic wave 41 to f ₁ , f ₂ , f ₃ , the diffraction angle also changes, and the light condensing position becomes the position of the photodetectors 17a, 17b, 17c, respectively, and the three diffracted lights 33a, 33b , the sum u _i of the intensity of 33c is obtained as a photodetector output. Thereby, the vector-matrix operation of the expression (2) can be performed.

The outputs of the photodetectors 17a, 17b, 17c are subjected to threshold processing by the comparators 18a, 18b, 18c, and fed back to the modulation currents of the semiconductor lasers 14a, 14b, 14c. Thereby, the luminous fluxes 31a, 31b, 31c
And the same calculation is repeatedly performed, and the most similar information is selected from the complete information accumulated as the surface acoustic wave intensity T _ij for the incomplete inputs 32a, 32b, and 32c, and the complete Outputs 44a, 44b and 44c are obtained. Here, in the present embodiment, the semiconductor lasers 14a, 14b, 14c as light sources
From the collimator lenses 15a, 15b,
After being collimated at 15c respectively, a single comb-shaped electrode 16
Are each diffracted by the surface acoustic wave excited by driving. At this time, the coupling intensity matrix affected by each light beam is T _i1 for the light beam 31a, T _i2 for the light beam 31b, and T _i3 for the light beam 31c as shown in FIG. . In order to function as a neuro element, the combination of the corresponding coupling intensity matrices of one light beam must be invariable, so it is understood that in this embodiment, feedback is performed when the coupling intensity matrix for each light beam is the same. Should.

In the above-described configuration, it is possible to perform an operation when the coupling strength matrix T _ij is positive. If T _ij takes a positive and negative values, the two optical neuro elements 51 and 52 of the above configuration used, as of FIG. 5, on the other hand, T in T _ij is positive, on the other hand 52 51
The operation when _ij is negative is performed using the absolute value of T _ij , and the output of the photodetectors 17a, 17b, 17c of one neuro element 51, that is, the operation result when T _ij is positive, Element 5
By subtracting the output of the second photodetectors 54a, 54b, 54c, that is, the operation result when T _ij is negative by the differential amplifiers 55a, 55b, 55c, the operation result when T _ij takes a positive or negative value is obtained. can get.
The results are thresholded by the comparators 56a, 56b, 56c, and the semiconductor lasers 14a, 14b, 14c, 58a, 58
What is necessary is just to feed back to the modulation current of b, 58c.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

For example, as shown in FIG. 6, light from a semiconductor laser 61 is converted into parallel light by a collimator lens 62, collected by a cylindrical lens 63, made incident on the slab type waveguide 12, and intensity-modulated by a light modulator 64. It may be converted into a plurality of light beams. Optical modulator 64
Is a metal clad 71 using Al or the like as shown in FIG.
It comprises an electrode 72 and a buffer layer 73. Buffer layer 73
Functions to prevent the light wave from being attenuated by the electrode 72. Electrode 72
The TE mode is converted to the TM mode by the electro-optic effect by applying a voltage to the
Since the light is attenuated at 74, a light beam having an intensity corresponding to the modulation current is obtained. Here, since the metal cladding 75 below the portion without the metal 72 is long, both the TE and TM modes are attenuated, and no light wave is output from the portion without the electrode 72. Further, in a portion of the electrode 72, the TE mode is hardly attenuated because the metal clad 74 is short, and only the TM mode is attenuated. As described above, by using the optical modulator, the number of light beams can be made very large, and a large amount of information can be processed. The following operation is the same as that of the above-described embodiment, and the diffracted light diffracted by the surface acoustic wave excited by the comb-shaped electrode 16 is condensed by the converging waveguide, received by the light receiving element 76, and After the threshold processing at 77, the signal is fed back to the optical modulator 64. As a result, the information most similar to the incomplete input 78 is obtained as the output 79 from the stored information. Although the electro-optic effect has been used for the optical modulator, a magneto-optic effect, an acousto-optic effect, or the like may be used.

Further, the number of light beams and the material of the waveguide are not particularly limited.

[Effects of the Invention] As is clear from the above description, according to the present invention, a surface acoustic wave acts on a light wave propagating through an optical waveguide,
A parallel operation is performed by converging the diffracted light with the light-converging waveguide to constitute an optical neuro element. That is,
The optical neuron device of the present invention can perform parallel operations on waveguides formed on one substrate, and is therefore compact, does not require optical axis adjustment, and is excellent in mass productivity and reliability.
Furthermore, since the coupling strength matrix can be changed by controlling the surface acoustic wave, it is possible to cope with various processes.

[Brief description of the drawings]

1 to 7 show an embodiment embodying the present invention. FIG. 1 is a configuration diagram of an optical neuron element according to an embodiment of the present invention, and FIG. 2 is a light focusing waveguide. FIG. 3 is an explanatory view showing propagation of a light wave in a light-converging waveguide, FIG. 4 is an explanatory view showing diffraction of a light wave by a surface acoustic wave, and FIG. FIG. 6 is a configuration diagram showing a configuration when two neuro elements corresponding to a matrix are used, FIG. 6 is a configuration diagram showing another embodiment of an optical neuro element,
FIG. 7 is a configuration diagram of an optical modulator, FIG. 8 is a configuration diagram showing another embodiment of a conventional optical neuro element, and FIG. 9 is an explanatory diagram showing accumulated information. In the figure, 11 is an optical neuro element, 12 is a slab type waveguide, 13 is a light focusing waveguide, 14a, 14b, 14c are semiconductor lasers, 15a, 15
b, 15c are selfoc lenses, 16 are comb electrodes, 1717a, 1
7b, 17c are light receiving elements, 18a, 18b, 18c are comparators, 31a, 31b, 31c
Is a light beam, and 33a, 33b, and 33c are diffracted lights.

Claims (1)

(57) [Claims] 1. A light source for emitting a plurality of light beams, light modulating means for modulating the intensity of each of the light beams, and a single surface acoustic wave exciting means for exciting a surface acoustic wave for diffracting each of the light beams. A light converging waveguide for condensing a light beam diffracted by the surface acoustic wave, a plurality of light receiving elements for detecting the condensed light beam, and performing a threshold process on an output signal from the light receiving element And an optical neuron device.