CN111348611B

CN111348611B - Silicon-based microcavity-based neuron-like light pulse output system

Info

Publication number: CN111348611B
Application number: CN202010160201.3A
Authority: CN
Inventors: 吴加贵; 袁欢; 张金平; 邓阳; 王泽豪
Original assignee: Southwest University
Current assignee: Southwest University
Priority date: 2020-03-10
Filing date: 2020-03-10
Publication date: 2023-05-09
Anticipated expiration: 2040-03-10
Also published as: CN111348611A

Abstract

The invention provides a neuron-like light pulse output system based on a silicon-based microcavity, which comprises a laser light source, an optical isolator, a polarizing plate, a silicon optomechanical microcavity, a photodiode, a high-speed oscilloscope and a spectrum analyzer, wherein the laser light source is arranged on the substrate; the laser light source is connected with the first end of the optical isolator; the second end of the optical isolator is connected with the first end of the positive-deflection light sheet; the second end of the correcting light sheet is connected with the first end of the silicon opto-mechanical micro-cavity; the second end of the silicon optomechanical microcavity is connected with the spectrum analyzer; the second end of the silicon optomechanical microcavity is connected with the anode of the photodiode; the cathode of the photodiode is respectively connected with a high-speed oscilloscope and a spectrum analyzer. The invention provides a light pulse output device similar to neuron spiking (pulse), the pulse time scale is in the nanosecond range, and the speed is nearly one million times faster than the millisecond time scale of biological neurons.

Description

Silicon-based microcavity-based neuron-like light pulse output system

Technical Field

The invention relates to the technical field of brain-like calculation, in particular to a silicon-based microcavity-based neuron-like light pulse output system.

Background

With the rapid development of artificial intelligence, the processing and calculation amount of data are increased exponentially each year, and the calculation requirements on computers are increased increasingly, so that computers working according to von neumann principle cannot meet the calculation requirements in many aspects. Research has been carried out in recent years to find that the human brain has very strong intelligent processing capability, which far exceeds the computer with the highest calculation speed. Inspired by the human brain, people began to look at artificial neurons. The neuron-like optical pulse intelligent chip based on the silicon-based microcavity has the characteristics of low energy consumption, small volume and high integration level. The data processing efficiency is improved, the power consumption is reduced, and the cost is saved.

An artificial neuron is a mathematical model that converts a biological model of a biological neuron. The processing unit of the artificial neuron works on the principle that each input signal is weighted to determine the intensity, all the input signals are summed to determine the combined effect, and the output is determined by the excitation function. Since the 21 st century, there has been rapid development in various fields with artificial neuron technology, so that artificial neurons are increasingly receiving attention from people. The rapid development of artificial neurons also makes the artificial intelligence field have a wider application space. Google team developed Alphago, which is artificial intelligence based on deep learning and monteca search algorithm, defeating the world first player Ke Jie at the peak of the black-town weiqi at 5 months 21 in 2017. In recent years, research on artificial neurons has been advanced in breakthrough, and an artificial neuron chip is developed by a research team consisting of oxford university, minster university and exsiccated university, and can simulate biological neurons and synapses under the action of light. The university of british has devised an artificial neuron chip which can reproduce a series of behaviors of biological neurons. The artificial neuron has great potential in various fields through decades of research and development and infiltration, and has great development space in the fields of face recognition, voice recognition, medical treatment, agriculture and the like in the future.

Disclosure of Invention

The invention aims at: the silicon-based technology is combined with the neuron technology, the response behavior of biological neurons is simulated, and the neuron-like light pulse output scheme based on the silicon-based microcavity is realized.

The invention provides a neuron-like light pulse output system based on a silicon-based microcavity, which comprises a laser light source, an optical isolator, a polarizing plate, a silicon optomechanical microcavity, a photodiode, a high-speed oscilloscope and a spectrum analyzer, wherein the laser light source is arranged on the substrate;

the laser light source is connected with the first end of the optical isolator;

the second end of the optical isolator is connected with the first end of the positive-deflection light sheet;

the second end of the correcting light sheet is connected with the first end of the silicon opto-mechanical micro-cavity;

the second end of the silicon optomechanical microcavity is connected with the spectrum analyzer;

the second end of the silicon optomechanical microcavity is connected with the anode of the photodiode;

the cathode of the photodiode is respectively connected with a high-speed oscilloscope and a spectrum analyzer.

Further, the method comprises the steps of,

the optical isolator is used for preventing disturbance of external disturbance light;

the polarization controller is used for obtaining linearly polarized light;

the silicon-based photon microcavity chip is used for outputting optical pulses through coupling of carrier spontaneous limit cycle oscillation and opto-mechanical oscillation; the photodiode is used for converting an optical signal into an electrical signal;

the high-speed oscilloscope and the spectrum analyzer are used for analyzing waveforms.

Further, the method comprises the steps of,

and periodically arranging micro round holes on the silicon-based material of the silicon optomechanical microcavity to obtain a photonic crystal structure working in a C wave band, and forming an optical energy band structure.

Further, the micro hole displacement of 5nm,10nm and 15nm is respectively arranged in the central area of the silicon optical mechanical micro-cavity, so that the photonic crystal local defect is formed in the central area of the silicon optical mechanical micro-cavity.

Further, the preparation of the silicon wafer of the opto-mechanical crystal on the insulator comprises the following steps:

reactive ion etching is carried out on a silicon film with the thickness of 250nm, and the width of the slit is controlled to be critical 80 nanometers;

the patterned profile of the resist was used to approximate 185nm slot line width and then converted to an angled oxide etch to give an oxide gap with a bottom of 80 nm.

Further, the silicon-based material of the silicon opto-mechanical microcavity has a lattice constant of 500nm, and the difference between the pore radius and the lattice constant is 0.34.

The beneficial effects of the invention are as follows:

1. the invention provides a light pulse output device similar to neuron spiking (pulse), the pulse time scale is in the nanosecond range, and the speed is nearly one million times faster than the millisecond time scale of biological neurons.

2. Compared with the traditional optical neuron scheme, the optical microcavity has the size of about 10 microns, is obviously improved in the aspect of integration level, and can be applied to a high-density ultrafast information processing network.

3. The invention is neuron-like pulse output realized on the silicon-based material, and the scheme has good advantages in the aspect of expandability and integrability because of the natural compatibility of the silicon material and the CMOS process.

The invention combines silicon and photon neurons to provide a silicon-based neuron-like optical pulse spiking generation scheme, and the invention is based on optical signal processing, has a pulse width in the range of about 4 nanoseconds and has a millions of times faster speed than millisecond-level biological neuron pulses. The silicon material-based integrable optical neuron has the natural advantages of super high speed, large bandwidth, low power consumption and the like, is superior to an electrical nerve mimicry hardware system, and can realize the calculation task of super high speed and low power consumption in the future.

Drawings

Figure 1 is a block diagram of a silicon-based photonic microcavity chip,

FIG. 2 is a schematic diagram of a neuron-like optical pulse output overall system

Fig. 3 is a graph of the optical pulse time domain test result of the laser output by the system according to the present invention.

Fig. 4 is an experimental result of a typical single Spiking test.

Fig. 5 shows the results of two Spiking tests produced in succession in an experiment.

Detailed Description

Aiming at the limitations of slow processing speed of the traditional neuron information and the like, a research group proposes a mode of introducing an optical processing mechanism in the nerve mimicry calculation. The photons have the characteristics of high speed and high bandwidth, so the method is suitable for being applied to ultra-fast processing networks with high density and based on pulses, and the optical equipment has the characteristic of low power consumption in the process of processing information. Optical neuromorphics have great potential in the field of ultrafast optical computing. The photon neuron is a basic element for information processing in nerve mimicry calculation, and the general working principle is as follows: the input pulse event signal is processed, and when the equivalent parameter of the cell membrane potential reaches a certain threshold value, the neuron outputs a pulse event through the pulse generator. With the development of photon signal processing technology and artificial neurons, it is possible to develop a photon neuron, which has similar physical characteristics as a biological neuron, but is different in that the biological neuron is affected by a chemical substance in the organism, and the photon neuron is affected by the semiconductor characteristics of the optical device itself. The operation speed of the optical neuron is millions to billions times of that of the biological neuron, and the optical neuron cannot exceed that of other nerve mimicry systems, and can also realize complex calculation tasks which cannot be completed by traditional digital or analog optical calculation, such as learning and memory, self-adaptive control and the like. The existing optical neurons also face some problems, in particular low integration level, high power consumption, incompatibility with silicon materials required by a CMOS integrated process and the like.

Aiming at the existing pulse neuron technology, the invention aims to provide a neuron-like light pulse output scheme based on a silicon-based microcavity, and the invention combines the silicon-based technology with the neuron technology, can simulate the response behavior of biological neurons, realizes the generation of the light pulse of the neuron-like, can realize ultra-low power consumption and is beneficial to the development of the integrated photon neuron technology.

The invention provides a silicon-based microcavity-based neuron-like light pulse output system, which mainly comprises the following components: laser source (Laser), OI, polaroid (POL), silicon-based photon microcavity chip (Silicon optomechanical chip), photodiode (PD), high-speed oscilloscope (High speed oscilloscope), post-processing module (Post-processing).

The basic principle of the invention is described below: the system finally outputs corresponding neuron-like light pulses through the modulation action of the micromechanical resonator in the silicon-based photon microcavity structure. In which the silicon-based photonic microcavity chip is mainly a micromechanical resonator and a high Q/V optical resonator to act on the optical field inside the cavity. By analyzing the vibration displacement of the micro vibrator, the direct nonlinear coupling of the optical field intensity, the carrier concentration, the local temperature offset and the like in the cavity can reveal the basic physical process of the integrated laser chaotic source. Basically, in silicon-based photonic microcavities, free Carrier Dispersion (FCD) will result in a blue-shift of the cavity, while two-photon absorption (TPA) and Free Carrier Absorption (FCA) will result in a red-shift. Competition for these two nonlinear mechanisms will result in time-domain modulation of the silicon photonic microcavity output. In particular, when the input optical frequency is slightly red shifted with respect to the silicon photonic microcavity. The intracavity of the high Q microcavity will result in significant TPA effects because of optical field localization. While TPA will further generate a large amount of free carriers. The associated FCD and FCA mechanisms will dissipate the free carriers. Wherein FCD may cause a fast photonic microcavity to blue shift, while TPA and FCA will heat the photonic microcavity resulting in a slow red shift. This red shift eventually prevents the blue shift and further red shifts the entire photonic microcavity, which will rapidly attenuate the light field in the cavity, slowly cooling the microcavity, and eventually the microcavity into the next cycle. This results in a spontaneous limit cycle oscillation. However, there is another limit cycle oscillation in the microcavity, namely optomechanical oscillation (Optomechanical oscillation, OMO), which can modulate the intra-cavity optical field of the silicon-based photonic microcavity when the input optical power exceeds the inherent mechanical damping loss, creating a continuous oscillation. The coexistence of the two will allow the system additional degrees of freedom and thus be relatively prone to destabilization. Through realizing effective coupling between OMO and spontaneous oscillation, the silicon-based photon microcavity chip enters an oscillation state of neuron-like spiking.

Fig. 1 is a schematic diagram of a silicon-based photonic microcavity chip, as shown in fig. 1, in which an input optical pulse is modulated by coupling carrier spontaneous limit cycle oscillation and opto-mechanical oscillation, and when the microcavity enters a pulse oscillation state similar to neuron Spiking, a neuron-like optical pulse is outputted.

Fig. 2 is a schematic diagram of a system for outputting a neuron-like optical pulse, as shown in fig. 2, wherein the main structures are as follows: laser: laser light source, OI: optical isolator, POL: polarizing plate, silicon optomechanical microcavity: silicon opto-mechanical microcavity, PD: photodiode, high speed oscilloscope: high speed oscilloscope, OSA: spectrum analyzer, ESA: a spectrum analyzer. Wherein the optical isolator is used for preventing disturbance of external disturbance light; the polarization controller has the function of obtaining linearly polarized light; the silicon-based photon microcavity chip outputs optical pulses through the coupling of carrier spontaneous limit cycle oscillation and opto-mechanical oscillation; photodiodes convert optical signals into electrical signals; the waveforms were analyzed by a high-speed oscilloscope, a spectrum analyzer, and a spectrum analyzer.

FIG. 3 is a graph showing the time domain test results of the optical pulse output by the laser passing system according to the present invention, as shown in FIG. 3, which has four typical neuron Spiking pulse characteristics including absolute refractory period, relative refractory period, super-normal period, and low-normal period, when the microcavity enters the pulse oscillation state of Spiking to generate an optical pulse, the test results show that the width of the optical pulse is about 4ns, and then the period is absolute refractory period (Absolutely refractory), i.e. the input energy is increased in the interval and no new pulse is obtained; then, the device enters a relative refractory period (Relatively refractory) during which an increased input can produce a pulse of light but not a pulse of light of the same amplitude as the original pulse; the corresponding non-response period is ended, namely, the abnormal period is entered, and transient excitation higher than a normal value occurs in the period; then enters a low-normal period during which transient sub-normal excitations occur, conforming to the behavioral characteristics of biological neurons.

Specifically, in the present invention, as shown in fig. 1, the present invention designs a micro-cavity chip based on silicon-on-insulator (SOI) opto-mechanical crystal, which realizes equivalent quality on the order of picograms. First, the optical sum of the optomechanical crystal and the cavity optomechanical coupling are designed. The designed devices were then prepared and then tested for performance in an experimental test protocol. The device is based on a two-dimensional planar optomechanical crystal theory, a photonic crystal structure working in a C wave band is obtained by periodically arranging tiny round holes (the lattice constant of the photonic crystal structure is 500nm, and the difference between the hole radius and the lattice constant is 0.34) in a silicon-based material, so that an optical energy band structure is formed, and accordingly light waves transmitted in the photonic crystal structure are regulated and controlled, and 5nm,10nm and 15nm tiny hole displacement is arranged in the central area of a microcavity, so that local defects of the photonic crystal are formed, constraint on the light waves is realized, and in addition, phonon crystals are formed by spatially and periodically arranged micropores of a material III, so that the acoustic energy band structure is provided. Specifically, in the scheme, the invention obtains the acoustic oscillation by introducing a micro groove of about 100nm on the central symmetry axis of the silicon photonic crystal.

The following describes the design and manufacture of the device in the implementation of the present invention: the opto-mechanical crystal of the present invention is fabricated on silicon-on-insulator (SOI) wafers using reactive ion etching on 250nm thick silicon films. The width of the slit is controlled to be critical 80 nanometers, the patterning outline of the resist is about 185nm of the line width of the slit, then the patterning outline is converted into inclined oxide etching, the oxide gap with the bottom of 80nm is obtained, and efficient coupling of light waves (light fields) and elastic waves (mechanical vibration) is realized so as to be beneficial to obtaining spiking oscillation signals.

Device test protocol as shown in fig. 2, light with a wavelength of 1538.7nm was first output by using an adjustable laser, which was isolated by an Optical Isolator (OI) and protected from disturbance by external disturbance light, and then entered a polarization controller (POL) to obtain good linearly polarized light, which was injected into the silicon optical instrument microcavity of the experiment through a coupling lens. The wavelength of the driving light and the frequency of the cavity are maintained by controlling the temperature of the microcavity, the specific implementation quantity can be selected to be-10 pm, the light length entering the silicon optical microcavity at the moment can carry out strong modulation on the microcavity, strong spontaneous carrier limit cycle oscillation and opto-mechanical oscillation are excited, and the coexistence of the two enables the cavity to have enough freedom degree and the threshold value to be easily unstable. Through the coupling between OMO and spontaneous oscillation, the microcavity enters a pulse oscillation state similar to neuron Spiking, so that a light pulse similar to neuron is output, the light pulse is injected into a high-speed photoelectric detector, an optical signal is changed into an electric signal so as to facilitate subsequent equipment analysis and detection, and part of light output by the microcavity is injected into a high-resolution spectrometer to implement accurate measurement. Fig. 3 is a graph of typical Spiking results obtained from testing microcavities, showing four typical features of Spiking: absolute refractory period (Absolutely refractory), relative refractory period (Relatively refractory), hypernormal period (Supernormal phase), hyponormal period (Subnormal phase), fig. 4 is a typical single Spiking pulse result from the test; fig. 5 is a typical cascade Spiking pulse result from the test.

In the present embodiment, the lattice constant of the silicon-based material of the silicon opto-mechanical microcavity is 500nm, the difference between the pore radius and the lattice constant is 0.34, and the central region of the silicon opto-mechanical microcavity is respectively provided with 5nm and 10nm and 15nm of micro-pore displacement, so that the photonic crystal local defect is formed. Optomechanical crystals were fabricated on silicon-on-insulator (SOI) wafers using reactive ion etching on 250nm thick silicon films. The width of the slit was controlled to critical 80nm width and the patterned profile of the resist was used to approximate 185nm slit line width, which was then converted to an angled oxide etch to give an oxide gap with a bottom of 80 nm. The inventor provides fig. 3, fig. 4 and fig. 5 through experiments, and proves that the above parameter selection can realize the technical effect that the silicon opto-mechanical microcavity enters a pulse oscillation state similar to neuron Spiking so as to output the optical pulse of the neuron.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The neuron-like optical pulse output system based on the silicon-based microcavity is characterized by comprising a laser light source, an optical isolator, a polarizing plate, a silicon optomechanical microcavity, a photodiode, a high-speed oscilloscope and a spectrum analyzer;

the laser light source is connected with the first end of the optical isolator;

the second end of the optical isolator is connected with the first end of the polarizing plate;

the second end of the polarizing film is connected with the first end of the silicon opto-mechanical microcavity;

the cathode of the photodiode is respectively connected with a high-speed oscilloscope and a spectrum analyzer;

the silicon-based material of the silicon opto-mechanical microcavity is periodically provided with micro round holes to obtain a photonic crystal structure working in a C wave band, and an optical energy band structure is formed;

the lattice constant of the silicon-based material of the silicon opto-mechanical microcavity is 500nm, the difference between the pore radius and the lattice constant is 0.34, the central area of the silicon opto-mechanical microcavity is respectively provided with 5nm and 10nm and 15nm of micro-pore displacement, opto-mechanical crystals are manufactured on a silicon wafer on an insulator, the silicon film with the thickness of 250nm is used for reactive ion etching, the width of a slit is controlled to be critical 80 nanometers, the patterning profile of the resist is 185nm slit line width, and then the patterning profile is converted into inclined oxide etching, so that the oxide gap with the bottom of 80nm is obtained.

2. A silicon-based microcavity-based neuron-like optical pulse output system according to claim 1, wherein the optical isolator is used to prevent disturbance of ambient interfering light;

the polarizing plate is used for obtaining linearly polarized light;

the silicon optomechanical microcavity is used for outputting optical pulses through coupling of carrier spontaneous limit cycle oscillation and optomechanical oscillation;

the photodiode is used for converting an optical signal into an electrical signal;