Integrated optics vector-matrix multiplier based on micro-ring resonator
Technical field
The present invention relates to optics vector-matrix multiplier technical field, relate in particular to a kind of integrated optics vector-matrix multiplier (Optical Vector-Matrix Multiplier based on micro-ring resonator, OVMM), (Microring Resonator MRR) arranges by two dimension and realizes this optics vector-matrix multiplier by the micro-ring resonator of tunable straight parallel waveguiding structure.
Background technology
At first, the model of optics vector-matrix multiplier is that the J.W.Goodman of U.S. Stanford university proposes, " Fully parallel; high speed incoherentoptical method for performing discrete Fourier the transforms " (J.W.Goodman that delivered in 1978, OPTICS LETTERS, Vol.2, No.1 1-3) introduces it.Goodman " Stamford vector-matrix multiplier " mainly comprises three parts, i.e. array of source, matrix mask and detector array.At first utilize delegation's light emitting diode as input vector, between light emitting diode matrix and matrix mask, arrange light path to make each light emitting diode only illuminate row of matrix mask, behind matrix mask, arrange such light path again, light from each row of matrix mask is focused on the different detecting elements, thereby realized 10 discrete Fourier transformation.Calculated the huge applications potentiality in field at photometry though it has been recognized that OVMM at that time, but reason owing to technology, the precision of array of source, detector array and spatial light modulator, dimension and speed are all not ideal enough, so the work of this respect stagnates always.In addition, because light signal is propagated and diversity at free space, capacity usage ratio is low, and system design and resetting difficulty are big.These shortcomings have all limited its range of application.
The stagnation that photometry is calculated research is because the photometry calculation itself faces a lot of challenges on the one hand, on the other hand also because development of integrated circuits.Since the seventies in last century,, obtained to reach the quick and lasting development of three more than ten years based on the microprocessor of integrated circuit along with the progress of semiconductor process techniques.We know that transistorized size is done more for a short time on the chip, and the frequency of CPU work just can be high more.Along this thinking, people improve the performance of the CPU prophesy according to Moore's Law again and again.But develop into today, occurred some new problems again, high primary frequency causes the power consumption of CPU sharply to rise, and electric leakage and heat dissipation problem also are difficult to solve.Transistor size integrated on the chip means that near the limit of physics the performance of integrated circuit also will reach capacity, and Moore's Law will lose efficacy soon.At this problem, people begin to consider to adopt new physical principle to realize processor and computing machine, wherein mainly comprise optical computer and quantum computer.Though the universal microprocessor based on these notions also has a segment distance apart from practicability, the development of some essential elements or prototype machine is very meaningful.Because these new ideas computing machines adopt some special physical principles, they may be good at and handle a certain generic task very much.Just has the high advantage of concurrency such as the optical processing mode.This makes them handling for some special duties provide association at present, perhaps can become the microprocessor and the Computer realizing way of main flow in future.
The research of optics vector-matrix multiplier that scientist's early starts such as the Germany Hagen M.Gruber of university are integrated, be published in " Planar-integrated optical vector-matrixmultiplier " (Matthias Gruber in 2002, APPLIED OPTICS, Vol.39, No.29,5367~5373) having put down in writing them realizes the method for OVMM on semiconductor wafer.Its basic thought remains such that professor J.W.Goodman proposes, and has adopted the technology of semiconductor wafer only now.The function of lens adopts the lenticule and the diffraction element (DOE, Diffraction Optical Element) of being made by lithographic technique to realize here in J.W.Goodman professor's the model.Because still adopt the mode of freely propagating (in semiconductor material) to realize the diversity of light signal, the energy efficiency of system is very low, so just very high to the requirement of light source and detector, this just makes it be difficult to real practicability.
The device of a kind of OVMM is disclosed in patent US 4,620,293 " Optical matrix multiplier ".Wherein, utilize light emitting diode (LED) that input vector is provided, provide the matrix of input, utilize photodetector to realize the detection of light signal, realized optics vector-matrix multiplication by spatial light modulator (SLM).As seen, it promptly is the specific implementation of the model of J.W.Goodman proposition.
The device of a kind of OVMM is disclosed in patent EP 1,436,681 " Vector-Matrix Multiplication ".Wherein, utilize vertical cavity surface emitting laser (VCSEL) that input vector is provided, provide the matrix of input, utilize photodetector to realize the detection of light signal, realized optics vector-matrix multiplication by Multiple Quantum Well spatial light modulator (MQW-SLM).And algorithm, function library, storer and peripheral control unit have been designed for it.Although it has adopted more advanced device, but still be the specific implementation of the spatial transmission diversity model of J.W.Goodman proposition.
A kind of device of integrated optics vector-matrix multiplier is disclosed in patent US 4,125,316 " Integrated optical matrix multiplier ".It adopts photoconductive material waveguide a and electrooptical material waveguide b to make, and when light process a, causes that the electric field at b place changes, thereby the light among the b is had an effect.This is to utilize electric field to realize light for media multiplication is finished in the modulation of light in fact.But this scheme need be used photoconductive material and electrooptical material, and is incompatible with integrated circuit technology.
Summary of the invention
(1) technical matters that will solve
In view of this, fundamental purpose of the present invention is to provide a kind of optics vector-matrix multiplier based on micro-ring resonator, to improve message data rate, reduce the delay that information is transmitted, avoid shortcomings such as the low precision, programmability of simulated light computing system be weak, and solve the problem of traditional optical vector-matrix multiplier space diversity inefficiency.
(2) technical scheme
For achieving the above object, the invention provides a kind of integrated optics vector-matrix multiplier, this optics vector-matrix multiplier is made of the inner product operation unit of Parallel coupled, this inner product operation unit has the micro-ring resonator of the tunable parallel waveguide structure of a plurality of one dimensions arrangements, this optics vector-matrix multiplier adopts the mode of integrated optics to realize the multiplication of M * N matrix and N * 1 vector, wherein the element in matrix and the vector is 0 or 1 binary number, and M, N are natural number.
In the such scheme, this micro-ring resonator is the micro-ring resonator that the input and output straight wave guide is parallel to each other, rather than the micro-ring resonator of crossing waveguide structure, does not have coupling between the ring of micro-ring resonator.
In the such scheme, this micro-ring resonator comprises two straight wave guides that are parallel to each other and a disc waveguide, and this disc waveguide and two straight wave guides are tangent.
In the such scheme, the function implementation procedure of this vector-matrix multiplier is:
Input end is the straight wave guide port of M inner product operation unit, and input signal is determined by initial vector, if i element of initial vector is 1, then all M port input all contains corresponding wavelength composition λ
iLaser pulse; If i element of initial vector is 0, then all the input of M port does not contain this wavelength signals;
If the capable j column element of i of matrix is 1, then the resonance wavelength of j MRR of i inner product operation unit is tuned to λ
jIf the capable j column element of i of matrix is 0, then the resonance wavelength of j MRR of i inner product operation unit is adjusted to non-λ
1, λ
2..., λ
NArbitrary wavelength place, j=1 wherein, 2 ..., N;
M output port at optics vector-matrix multiplier surveyed, and the gained light intensity is followed successively by the element of vector-matrix multiplication gained M dimension result vector.
In the such scheme, the different elements corresponding different wavelength of laser pulse respectively in this vector-matrix multiplier input vector, when certain element in the input vector was 0, the laser pulse power of corresponding wavelength was zero; When certain element was 1, the power of the laser pulse of corresponding wavelength was a default normal value; In each computing, the input of each port of vector-matrix multiplier is identical.
In the such scheme, characterize the element of input matrix with the resonant condition of MRR, corresponding inner product operation unit of each row of matrix, the capable j column element of i is 1 o'clock, the resonance frequency of j little ring is λ
jWhen this element was 0, the resonance frequency of j little ring was non-λ
1, λ
2..., λ
NArbitrary wavelength, j=1 wherein, 2 ..., N.
(3) beneficial effect
From technique scheme as can be seen, the present invention has following beneficial effect:
Integrated optics vector-matrix multiplier provided by the invention utilizes ready-made technology, makes device volume little, and is low in energy consumption, and favorable expandability is convenient to electricity component integrated; Utilize laser pulse to transmit information, the speed height postpones little; Carry out signal Processing with digital form, avoided low precision, the weak shortcoming of programmability of simulated light computing system; With high index-contrast waveguide light conducting, solved the problem of traditional optical vector-matrix multiplier space diversity inefficiency.
Description of drawings
Fig. 1 is the micro-ring resonator of parallel waveguide structure;
Fig. 2 is the inner product operation unit;
Fig. 3 is the structural representation based on the integrated optics vector-matrix multiplier of micro-ring resonator.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
Fig. 1 is the elementary cell that constitutes optics vector-matrix multiplier, the i.e. tunable micro-ring resonator of straight parallel waveguiding structure.Port one is an input end, and port 2 is straight-through end, and port 3 is an output terminal, and supposes that the resonance frequency of little ring is λ
1Utilize single tunable micro-ring resonator can realize the multiplication of two one bits, the input/output end port that it is corresponding and the resonant condition of little ring are as shown in table 1, and table 1 is to utilize single micro-ring resonator to realize the multiplication of two binary numbers.Wherein, the input light of port one and the resonance wavelength of little ring are represented two multipliers respectively, and promptly port one has λ
1Light when input, first multiplier is 1, otherwise is 0, the micro-ring resonant wavelength is λ
1The time, second multiplier is 1, otherwise is 0; Result of calculation is represented that by the output of port 3 it is 1 that the light time ecbatic is arranged, otherwise is 0.
Table 1
Fig. 2 is the inner product operation unit, can realize the inner product operation of two binary vectors.What realize as Fig. 2 is inner product operation between the vector [1011] and [0111].Detailed process is: be respectively λ from the input port input wavelength
1, λ
3, λ
4Light (expression vector [1011]); Modulate the 1st little ring simultaneously, making its resonance wavelength is non-λ
1, λ
2, λ
3Or λ
4Any wavelength, and the resonance wavelength of other little rings is constant, is followed successively by λ
2, λ
3, λ
4(representing another vector [0111]); Then will to comprise wavelength be λ to output terminal
3And λ
4Light, operation result (luminous power of output terminal) records by the photodetector of output terminal.
Fig. 3 is the structural representation based on the integrated optics vector-matrix multiplier of micro-ring resonator.On the basis of the principle of work of having understood inner product operation unit shown in Figure 2, be not difficult to find out that this scheme realizes that vector is very directly perceived with the principle of matrix multiplication operation.So-called matrix-vector multiplier only need repeat to make a plurality of inner product operations unit and get final product, and when OVMM worked: synchronization was imported the vector of all inner product operation devices, and promptly laser pulse combination all is identical; The resonance wavelength of different is all little rings all is independently to control according to matrix to be calculated at that time.
Following formula is the M * N matrix that can finish of this optics vector-matrix multiplier and the general expression formula of N * 1 vector multiplication computing.Formula above below contrasting, Fig. 3 is done the explanation of some necessity:
1) input of four input ports of synchronization all is vectorial X=[x
1x
2x
3x
4], vector element x
iBe 1/0, λ in the corresponding input light wave
iThe having/do not have of composition;
2) row/row of the row of matrix/corresponding little ring array of row difference.As arbitrary matrix element w
Ij=1 o'clock, the resonance wavelength of the micro-ring resonator of the capable j row of corresponding i was λ
jWork as w
Ij=0 o'clock, the resonance wavelength of the micro-ring resonator of the capable j row of corresponding i was non-λ
1, λ
2..., λ
NArbitrary wavelength;
3) each inner product operation unit, the delegation of realization matrix and the inner product operation of input vector obtain an element in the input vector.The multiplying of M * N matrix and N * 1 vector just can be realized in M such unit side by side.
Specify with regard to the principle of work of optics vector-matrix multiplier above, needing more ben is the setting of resonance wavelength.The λ that we mention in front
1, λ
2..., λ
NAnd non-λ
1, λ
2..., λ
NArbitrary wavelength all be to be limited to same free spectral limit (Free Spectral Range is in FSR).This is by the decision of the filtering characteristic of micro-ring resonant wave filter, supposes that N little ring in the inner product operation device has identical FSR and three dB bandwidth, then λ
1, λ
2..., λ
NCan set according to two three dB bandwidths of being separated by successively, so just require FSR to be at least 2N three dB bandwidth doubly, when needing to change 0,1 state of little ring, only the resonance wavelength of little ring need be regulated a three dB bandwidth and get final product.This structure have one outstanding be a little to have favorable expansibility: on the one hand, because the loss of each inner product operation unit only comes the loss in the self-waveguide, so little ring that can a lot of different resonance wavelengths of serial arrangement, promptly Xiang Liang dimension N can get very big; On the other hand, and the line number that increases matrix only means and increase identical inner product operation unit that the value of M is restricted hardly.
Optical vector matrix multiplier based on the parallel ring resonator provided by the invention can be with different material, and as SOI, SiN and III-V family material etc., tuning mode also has multiple choices, and principle is directly perceived, realize simply, and extensibility is strong.All little rings all adopt identical design and processes flow process, just the MRR of different lines has intrinsic separately resonance wavelength in the matrix, and this can be by realizing the different physical dimension (comprising the spacing of radius, straight wave guide and the ring of little ring, the sectional dimension of disc waveguide etc.) of each MRR design.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.