CN111348611A

CN111348611A - Neuron-like optical pulse output system based on silicon-based microcavity

Info

Publication number: CN111348611A
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: 2020-06-30
Anticipated expiration: 2040-03-10
Also published as: CN111348611B

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 connected with the optical isolator; 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 polaroid; the second end of the polaroid is connected with the first end of the silicon optical mechanical microcavity; the second end of the silicon optical mechanical microcavity is connected with the spectrum analyzer; the second end of the silicon optical mechanical microcavity is connected with the anode of the photodiode; the cathode of the photodiode is respectively connected with the high-speed oscilloscope and the spectrum analyzer. The invention provides a neuron spiking (pulse) like optical pulse output device, wherein the pulse time scale is in a nanosecond range, and the speed is faster than the millisecond time scale of a biological neuron by nearly one million times.

Description

Neuron-like optical pulse output system based on silicon-based microcavity

Technical Field

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

Background

With the rapid development of artificial intelligence and the arrival of a big data era, the processing and calculation amount of data is exponentially increased every year, and the calculation requirements on computers are increasingly strengthened, so that computers working according to the von Neumann principle cannot meet the calculation requirements in many aspects. Research in this year finds that the human brain has very strong intelligent processing capacity, which far exceeds the computer with the highest computing speed at present. Inspired by the human brain, people began to turn their eyes to the study of artificial neurons. The neuron-like optical pulse intelligent chip based on the silicon-based microcavity has the characteristics of low energy consumption, small size and high integration level. The data processing efficiency is improved, meanwhile, the power consumption is reduced, and the cost is saved.

An artificial neuron is a model that transforms a biological model of a biological neuron into a mathematical model. The working principle of the processing unit of the artificial neuron is to weight each input signal to determine its strength, to sum all the input signals to determine the combined effect, and to determine its output by means of an excitation function. Since the 21 st century, the artificial neuron technology has been developed rapidly in various fields, so that the artificial neuron is more and more valued by people. The rapid development of artificial neurons also enables the artificial intelligence field to have wider application space. Google teams developed Alphago, which was artificial intelligence based on deep learning and monte card search algorithms, defeating the world's first chess manual kojie at the wuzhen go peak meeting of 21 months 5 and 2017. In recent years, research on artificial neurons has been progressing in a breakthrough manner, and research teams, consisting of the university of oxford, the university of minster, and the university of eckett, have developed an artificial neuron chip that can mimic biological neurons and synapses under the action of light. The university of barus, uk, designed an artificial neuron chip that can reproduce a series of behaviors of biological neurons. After decades of research and development, artificial neurons penetrate into various fields, show huge potential, and have huge 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 to: the silicon-based micro-cavity-based neuron-like optical pulse output scheme is characterized in that a silicon-based technology and a neuron technology are combined, response behaviors of biological neurons are simulated, and generation of optical pulses of the neuron-like neurons is achieved.

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 connected with the optical isolator;

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 polaroid;

the second end of the polaroid is connected with the first end of the silicon optical mechanical microcavity;

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

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

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

Further, in the above-mentioned case,

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

the polarization controller is used for obtaining linearly polarized light;

the silicon-based photon microcavity chip is used for outputting light pulses through coupling of carrier spontaneous limit ring oscillation and photomechanical 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 the waveform.

Further, in the above-mentioned case,

the silicon-based material of the silicon-based optomechanical microcavity is periodically provided with tiny round holes to obtain a photonic crystal structure working in a C wave band and form an optical energy band structure.

Furthermore, the central region of the silicon photomechanical microcavity is respectively provided with micro-hole displacements of 5nm, 10nm and 15nm, so that the central region of the silicon photomechanical microcavity forms a photonic crystal local defect.

Further, the preparation of the photomechanical crystal on the silicon wafer of the insulator comprises the following steps:

performing reactive ion etching on a silicon film with the thickness of 250nm, and controlling the width of a slit to be a critical width of 80 nanometers;

the patterned profile with resist was approximately 185nm slot line width, then converted to an inclined oxide etch, resulting in an oxide gap with 80nm bottom.

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

The invention has the beneficial effects that:

1. the invention provides a neuron spiking (pulse) like optical pulse output device, wherein the pulse time scale is in a nanosecond range, and the speed is faster than the millisecond time scale of a biological neuron by nearly one million times.

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

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

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

Drawings

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

FIG. 2 is a schematic diagram of an overall system for neuron-like light pulse output

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

FIG. 4 shows typical single Spiking test results obtained from the experiment.

Fig. 5 shows the results of two Spiking tests performed in succession.

Detailed Description

Aiming at the limitations of low processing speed of traditional neuron information and the like, research groups propose a mode of introducing an optical processing mechanism into the neural mimicry calculation. Because photons have the characteristics of high speed and high bandwidth, the photonic crystal is suitable for being applied to a high-density pulse-based ultra-fast processing network, and optical equipment has the characteristic of low power consumption in the information processing process. The optical nerve mimicry shows great potential in the field of ultrafast optical computing. The photon neuron is a basic element for information processing in the calculation of the neural mimicry, and the general working principle is as follows: and processing the input pulse event signal, and outputting a pulse event by the neuron through the pulse generator after the equivalent parameter of the cell membrane potential reaches a certain threshold value. With the development of photon signal processing technology and artificial neurons, it has become possible to develop a photon neuron which has similar physical characteristics to those of a biological neuron, and is different from the biological neuron in that the biological neuron is affected by chemicals inside 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 is beyond the operation speed of other nerve mimicry systems, and complex calculation tasks which cannot be completed by traditional digital or analog light calculation, such as learning, memory, adaptive control and the like, can be realized. The current optical neurons also face some problems, especially low integration level, high power consumption, incompatibility with silicon materials required by CMOS integration 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 an integratable photon neuron technology.

The invention provides a neuron-like optical pulse output system based on a silicon-based microcavity, which mainly comprises the following components: the device comprises a Laser light source (Laser), OI, a polarizing Plate (POL), a Silicon-based photonic micro-cavity chip (Silicon optical chip), a Photodiode (PD), a High-speed oscilloscope (High-speed oscilloscope) and a Post-processing module (Post-processing).

The basic principle of the invention is explained below: and finally outputting the corresponding neuron-like optical pulse by the system through the modulation effect of the micromechanical resonator in the silicon-based photon microcavity structure. In the silicon-based photonic microcavity chip, mainly a micromechanical resonator and a high Q/V optical resonator act on an optical field in a cavity. By analyzing the vibration displacement of the micro-oscillator, the optical field intensity in the cavity, the carrier concentration, the local temperature offset and other direct nonlinear coupling, the basic physical process of the integrated laser chaotic source can be revealed. Basically, in a silicon-based photonic microcavity, 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 between these two nonlinear mechanisms will result in time-domain modulation of the silicon photonic microcavity output. Specifically, when the frequency of the input light is slightly red-shifted with respect to the silicon photonic microcavity. The cavities of the high Q microcavity will result in a significant TPA effect due to the optical field localization. And TPA will further generate a large number of free carriers. The associated FCD and FCA mechanisms will dissipate the free carriers. Where FCD can result in a fast blue-shift of the photonic microcavity, TPA and FCA will heat the photonic microcavity resulting in a slow red-shift. The red shift can finally prevent the blue shift and further red shift the whole photon microcavity, and the red-shifted photon microcavity can quickly weaken the optical field in the cavity, slowly cool the microcavity and finally enter the next cycle. This results in a spontaneous limit cycle oscillation. However, another limit ring oscillation exists in the microcavity, namely an Optomechanical oscillation (OMO), which forms a continuous oscillation when the input optical power exceeds the inherent mechanical damping loss, and the OMO can modulate the intracavity optical field of the silicon-based photonic microcavity. The coexistence of the two will make the system have extra freedom and thus be easy to destabilize. By realizing effective coupling between OMO and spontaneous oscillation, the silicon-based photon microcavity chip enters a neuron spiking-like oscillation state.

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

Fig. 2 is a schematic diagram of an overall system for outputting neuron-like light pulses, as shown in fig. 2, wherein the main structures are: laser: laser light source, OI: opto-isolator, POL: polarizing plate, Silicon optical mechanical microcavities: silicon photomechanical microcavities, PD: photodiode, High speed photodiode: high speed oscilloscope, OSA: spectrum analyzer, ESA: and a spectrum analyzer. Wherein the optical isolator is used for preventing disturbance of external interference light; the function of the polarization controller is to obtain linearly polarized light; the silicon-based photon microcavity chip outputs light pulses through coupling of carrier spontaneous limit ring oscillation and opto-mechanical oscillation; the photodiode converts an optical signal into an electrical signal; the waveform is analyzed by a high-speed oscilloscope, a spectrum analyzer and a spectrum analyzer.

Fig. 3 is a diagram of a time domain test result of an optical pulse output by a laser passing system according to the present invention, as shown in fig. 3, the optical pulse has four typical neuron Spiking pulse characteristics including an absolute refractory period, a relative refractory period, an extraordinary period, and an extraordinary period, when the microcavity enters the Spiking pulse oscillation state to generate an optical pulse, the test result shows that the width of the optical pulse is about 4ns, and then the optical pulse is an absolute refractory period (absolute refractory period), i.e., no new pulse is obtained when the input energy is increased in this interval; then, the device enters a relative refractory period (relative response) during which the increase in input can generate optical pulses, but cannot generate optical pulses of the same amplitude as the original pulses; entering a supernormal period when the relative refractory period is over, wherein hypersexual excitation higher than a normal value occurs; then entering a hypo-normothermic period during which transient sub-normal excitation occurs, consistent with behavioral characteristics of biological neurons.

Specifically, in the present invention, as shown in fig. 1, a micro-cavity chip based on a silicon-on-insulator (SOI) opto-mechanical crystal is designed, and equivalent mass in picogram order is realized. First, the optical and cavity opto-mechanical coupling of the opto-mechanical crystal is designed. Then, the designed device is prepared and then performance testing is performed in an experimental testing scheme. 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 micro round holes (the lattice constant of the photonic crystal structure is 500nm, and the difference between the radius of the holes and the lattice constant is 0.34) on a silicon-based material, so that an optical energy band structure is formed, the light wave transmitted in the photonic crystal structure is regulated, and a photonic crystal local defect is formed by setting the displacement of the micro holes of 5nm, 10nm and 15nm in the central region of a microcavity, so that the light wave is bound. Specifically, the invention obtains the acoustic oscillation by introducing microgrooves of about 100nm on the central symmetry axis of the silicon photonic crystal in the scheme.

The following description is provided for device design and fabrication in the practice of the present invention: the opto-mechanical crystal of the present invention is fabricated on a silicon-on-insulator (SOI) wafer using a 250nm thick silicon film for reactive ion etching. The width of the slit is controlled to be the critical 80nm width, the patterning profile using the resist is about 185nm slit line width, then the slit line width is converted into inclined oxide etching, the oxide gap with the bottom of 80nm is obtained, and efficient coupling of light waves (optical fields) and elastic waves (mechanical vibration) is realized, so that spiking oscillation signals are favorably obtained.

As shown in FIG. 2, firstly, the tunable laser is used to output light with a wavelength of 1538.7nm, the light is isolated by an Optical Isolator (OI) and then prevented from being disturbed by external interference light, enters a polarization controller (POL) to obtain good linearly polarized light, and the light is injected into the microcavity of the experimental silicon optical instrument through a coupling lens. The temperature of the microcavity is controlled to enable the wavelength of the driving light and the frequency of the cavity to implement quantity maintenance, and the specific implementation quantity can be selected to be-10 pm, so that the wavelength of the light entering the silicon optical microcavity can strongly modulate the microcavity and excite strong carrier spontaneous limit ring oscillation and photomechanical oscillation, and the coexistence of the two enables the cavity to have enough freedom and the threshold to be easy to destabilize. Through the coupling between the OMO and the spontaneous oscillation, the microcavity enters a pulse oscillation state similar to neuron Spiking, further the optical pulse of the neuron is output, the optical pulse is injected into a high-speed photoelectric detector, an optical signal is converted into an electric signal so as to facilitate the subsequent equipment analysis and detection, and meanwhile, part of the light output by the microcavity is injected into a high-resolution spectrometer to implement accurate measurement. FIG. 3 is a typical Spiking result obtained from testing a microcavity, showing four typical characteristics of Spiking: absolute refractory period (Absolute refractory), relative refractory period (relative refractory), hyper-normal period (Supernormal phase), hypo-normal period (Subnormal phase), FIG. 4 is a typical single Spiking pulse result from the test; fig. 5 shows the results of a typical cascading Spiking pulse obtained from the test.

In the embodiment, the lattice constant of the silicon-based material of the silicon-based optomechanical microcavity is 500nm, the difference between the pore radius and the lattice constant is 0.34, and the central region of the silicon-based optomechanical microcavity is provided with micro-pore displacements of 5nm, 10nm and 15nm respectively so as to form a photonic crystal local defect. Photomechanical crystals were fabricated on silicon-on-insulator (SOI) wafers using reactive ion etching on a 250nm thick silicon film. The width of the slit is controlled to be the critical 80nm width, the patterned profile using resist is approximately 185nm slot line width, and then converted to an inclined oxide etch, resulting in an 80nm oxide gap at the bottom. The inventor provides fig. 3, fig. 4 and fig. 5 through experiments, and proves that the parameter selection can achieve the technical effect of enabling the silicon optomechanical microcavity to enter a pulse oscillation state similar to neuron Spiking and further outputting a neuron-like light pulse.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A neuron-like light pulse output system based on a silicon-based microcavity is characterized by comprising a laser light source, an optical isolator, a polarized light sheet, 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;

2. The neuron-like optical pulse output system based on the silicon-based microcavity as claimed in claim 1, wherein the optical isolator is configured to prevent disturbance of external interfering light;

the polarization controller is used for obtaining linearly polarized light;

the silicon-based photon microcavity chip is used for outputting light pulses through coupling of carrier spontaneous limit ring oscillation and photomechanical oscillation;

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

3. The neuron-like optical pulse output system based on the silicon-based microcavity as recited in claim 1, wherein,