CN115327703A - Nonvolatile multi-stage adjustable photon nerve synapse device based on phase change material - Google Patents
Nonvolatile multi-stage adjustable photon nerve synapse device based on phase change material Download PDFInfo
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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- G02F1/025—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements with at least one potential jump barrier, e.g. PN, PIN junction in an optical waveguide structure
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Abstract
The invention discloses a nonvolatile multi-level adjustable photonic neurosynaptic device based on a phase change material, and belongs to the field of optical computing. Comprises a substrate, a slab layer waveguide, a periodic land waveguide and a phase-change film. The slab layer waveguide covers the whole substrate area, the periodic land waveguides are periodically distributed on the upper side of the slab layer waveguide, and the phase change film covers the surfaces of the slab layer waveguide and the periodic land waveguides; the periodic land waveguide comprises waveguide units which are periodically distributed along the propagation direction of a light beam, and each waveguide unit comprises two identical ridge waveguides and a slit structure between the two ridge waveguides. The geometry of the slab-layer waveguide and the periodic land waveguide will affect the effective mode index of the transmission mode within the waveguide by optimizing the period and duty cycle of the periodic land waveguide to achieve different output intensity outputs. By changing the phase state (crystalline state and amorphous state) of the phase change film, the photon nerve synapse has larger output intensity difference under the condition that the phase change film is in different phase states.
Description
Technical Field
The invention belongs to the field of optical computing, and particularly relates to a nonvolatile multi-level adjustable photonic neurosynaptic device based on a phase-change material.
Background
Over the last 50 years, semiconductor processing has matured from the first 180nm process to the current 5nm advanced process, and the 3nm process is now being developedThe integrated circuit technology is rapidly developed, the performance of an electrical computing system is rapidly improved, but the performance is limited by strict requirements on processing precision, the state cannot be developed all the time, and along with the gradual reduction of the size of a transistor, the problems of power consumption, heat dissipation and the like of a chip are gradually revealed, so that the traditional electrical computing system cannot continuously meet the requirements of high-speed, low-energy-consumption and large-scale communication. To solve this problem, researchers have proposed high-performance optical signal processing systems, such as optical processing chips based on a neuromorphic computing network architecture. Generally, a neuromorphic computing network consists of approximately 10 11 Each artificial neuron is used for adjusting the weight based on a light adjustable switch. Thus, the ability of a single optical switch will greatly impact the computational efficiency and power consumption of the optical neuromorphic network. Modulation speed and energy consumption are two key evaluation indexes of the optical switch, however, the current optical switch mainly depends on materials with weak and volatile thermo-optic or electro-optic modulation effects, so that the modulation speed is slow, the energy consumption is high, and the occupied space is large, thereby limiting the development of an optical neuromorphic computing network.
Chalcogenide phase change material Ge 2 Sb 2 Te 5 (GST) has excellent optical contrast between a covalently bonded amorphous state (a _ GST) and a resonance bonded crystalline state (c _ GST), and has found wide application in reconfigurable photonic devices such as optical switches, optical routers, and super-surfaces. Optical switches based on phase change materials, which do not require a static power supply to maintain the switching state and have a modulation speed in the order of sub-nanoseconds, are considered ideal unit devices for designing optical neuromorphic networks. GST is more widely used to design reconfigurable optical switches due to its mature processing technology. However, when a thin film of GST is sputtered directly on top of the silicon ridge waveguide, the light output intensity of the optical switch changes very little when the GST is in different phase states due to the weak interaction between the waveguide mode and the phase change material. Therefore, researchers have designed different waveguide structures such as Mach-Zehnder (MZ) switches and ring coupler switches, and the optical output intensity of these structures using the interference effect and the coupler effect is more sensitive to the phase state of the phase change material, so that the GST phase state can be enhancedThe effect of the change in optical switch output intensity. Their device size is large, which severely hampers large scale integration of optical neuromorphic networks. To solve this problem, some reports have proposed to enhance the interaction effect between the waveguide and the phase change material by designing special waveguide structures such as a land waveguide and a surface plasmon waveguide. However, when GST is in a _ GST and c _ GST states, the difference of the output intensity of the designed optical switch is about 40%, and a small output intensity modulation range is not beneficial to designing a multistage adjustable optical switch, so that the calculation accuracy of the photonic neural morphology calculation network is limited.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a nonvolatile multi-level adjustable photonic neurosynaptic device based on a phase change material, and aims to solve the problem that the normalized output intensity range of the photonic neurosynaptic is too small.
In order to achieve the above object, the present invention provides a nonvolatile multilevel tunable photonic neurosynaptic device using a phase change material, comprising a substrate, a slab layer waveguide, a periodic land waveguide, and a phase change film; the slab-layer waveguide covers the whole substrate area, the periodic land waveguides are periodically distributed on the upper side of the slab-layer waveguide, and the phase-change film covers the surfaces of the slab-layer waveguide and the periodic land waveguides; the periodic land waveguide comprises waveguide units which are periodically distributed along the propagation direction of a light beam, and each waveguide unit comprises two identical ridge waveguides and a slit structure between the two ridge waveguides; the section geometrical parameters of the slab layer waveguide and the periodic land-type waveguide in the photonic neurosynaptic device are used for regulating and controlling the effective mode refractive index of the transmission mode of incident light; the period and the duty ratio of the periodic land-type waveguide are used for regulating and controlling the coupling efficiency between a transmission mode of incident light and a periodic structure, and the period of the periodic land-type waveguide is also used for controlling the modulation length of a device; by optimizing the parameters, the regulation and control of the output intensity of the photonic neural synapses are realized.
The light output by the laser enters the photonic neurosynaptic device for transmission after passing through the coupling waveguide, the cross-sectional geometrical parameters of different slab layer waveguides and the periodic land-type waveguide affect the effective mode refractive index of a transmission mode in the photonic neurosynaptic, and the imaginary part of the effective refractive index of the transmission mode affects the transmission loss of the mode in the photonic neurosynaptic. The effective refractive index of a propagation mode in the photonic neural synapse is changed by adjusting the phase state (crystalline state and amorphous state) of the phase-change film, when the phase-change film is in the amorphous state, the mode energy is mainly concentrated in a silicon waveguide region, and when the phase-change film is in the crystalline state, part of the mode energy is coupled into the phase-change film, so that greater optical loss is caused, and the effect of regulating the output intensity of the photonic neural synapse is achieved.
Further, when the phase-change film is in different phase states, the larger the difference value of the effective refractive index imaginary part of the mode in the photonic synapse is, the larger the regulation range of the phase-change film on the output intensity of the photonic synapse is, and meanwhile, the period and the duty ratio of the periodic land-type waveguide also influence the output intensity of the photonic synapse. When the optical field is transmitted in the photonic nerve synapse, the cycle and the duty ratio of the periodic land-type waveguide affect the coupling efficiency of different modes and the photonic nerve synapse, and when the phase-change film is in an amorphous state, more optical field energy can be stably transmitted in the waveguide; when the phase-change film is in an amorphous state, most of the optical field energy needs to be lost in the transmission process, so that the purpose of regulating and controlling the output intensity of the photonic synapse is realized.
Furthermore, the cross-sectional geometrical parameters (height, width, period and duty ratio) of the slab layer waveguide and the periodic land waveguide are optimized, so that the nonvolatile multi-stage adjustable photonic neurosynaptic device based on the phase change material can achieve the maximum optical output intensity regulation range when the phase change film is in different phase states. Preferably, the initial cross-sectional geometrical parameters of the nonvolatile multi-stage adjustable photonic neurosynaptic device based on the phase change material are as follows: slab layer waveguide height (h) slab ) 100nm, the height of the periodic land-type waveguide is 240nm, and the width (w) of the silicon waveguide of the periodic land-type waveguide si ) 300nm, groove width (w) of periodic land-type waveguide slot ) At 100nm, the periodic land-type waveguide has a period (period) of 200nm and a duty cycle (h) of 50%.
Further, the material of the phase change film (4) is a chalcogenide phase change material Ge 2 Sb 2 Te 5 (GST)。
Further, the nonvolatile multi-level tunable photonic neurosynaptic device based on the phase change material can be processed on a silicon-on-insulator (SOI) platform with the height of 340nm or other high-level semiconductor platforms.
Further, the slab layer waveguide and the periodic land waveguide may be silicon waveguides or other low loss waveguides.
Further, the phase change film is selected to enhance the interaction between the optical field and the phase change film as much as possible.
Furthermore, the phase-change film is distributed on the surface of the slab layer waveguide.
Further, the period of the periodic land-type waveguide can be a fixed period or a multi-period mixture.
Further, the phase change film is covered on the slab layer waveguide and the periodic land-type waveguide, wherein the thickness of the phase change film 4 covered on the slab layer waveguide is more than or equal to 0.
Further, the cladding of the periodic land waveguide with the fixed period or the multiple periods mixed can be air or other materials, such as silicon dioxide.
Further, an oxidation prevention layer, such as noble metal gold or an ITO material, is coated on the phase change film to prevent oxidation denaturation of the phase change material.
Further, the cross-sectional geometrical parameters of the periodic land waveguide and the phase-change thin film are constant or slowly varying in the propagation direction.
Compared with the prior art, the nonvolatile multilevel adjustable photonic neurosynaptic device based on the phase-change material is provided by the technical scheme, and the nonvolatile multilevel adjustable optical switch based on the phase-change material is realized by designing the periodic land waveguide on the silicon platform. The waveguide section designed by the invention is similar to a land waveguide, and the coupling effect between the optical field and the phase change material can be enhanced. Meanwhile, a periodic structure is designed in the transmission direction of the optical waveguide, so that the output intensity difference of the optical switch when the phase change film is in different phase states is increased. The invention provides a nonvolatile multi-stage adjustable photonic neurosynaptic device which has very important significance and value in future optical neural network design, optical computation and optical communication.
Drawings
FIG. 1 is a three-dimensional schematic and a two-dimensional cross-sectional schematic of a non-volatile multi-level tunable photonic neurosynaptic device based on phase change materials.
Fig. 2 is a simulation result diagram of the electric field distribution of the photonic neurosynaptic after cross-sectional geometric parameter optimization, where (a) and (b) represent the electric field distribution of the phase-change thin film 4 in the amorphous state and the crystalline state, respectively.
Fig. 3 is a simulation result diagram of the transmission electric field distribution of the photonic neurosynaptic after cross-sectional geometric parameter optimization, where (a) and (b) represent the transmission electric field distribution of the phase-change thin film 4 in the amorphous state and the crystalline state, respectively.
FIG. 4 is a diagram of simulation results obtained from a nonvolatile multi-level tunable photonic neurosynaptic device based on a phase change material, where (a) and (b) represent normalized electric field distributions of the phase change thin film 4 in an amorphous state and a crystalline state, respectively.
FIG. 5 is a diagram of simulation results obtained from a phase-change material-based nonvolatile multi-level tunable photonic neurosynaptic device, where (a) and (b) represent the distribution of transmission electric fields of the phase-change thin film 4 in the amorphous and crystalline states, respectively.
Fig. 6 is a graph of the relationship between the silicon waveguide width of periodic land waveguide 3 and the optical output intensity difference.
Fig. 7 is a graph of the relationship between the height of the slab layer waveguide 2 and the optical output intensity difference.
Fig. 8 is a graph showing the relationship between the groove width of the periodic land waveguide 3 and the optical output intensity difference.
Fig. 9 is a graph showing the relationship between the period of the periodic land waveguide 3 and the difference in optical output intensity.
Fig. 10 is a graph of the duty cycle of periodic land waveguide 3 versus the optical output intensity difference.
Fig. 11 is a graph of the relationship between the number of periods of the periodic land waveguide 3 and the difference in optical output intensity.
FIG. 12 is a bar graph illustrating step control of output intensity for a multi-level tunable photonic neurosynaptic device.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a nonvolatile multilevel adjustable photonic neurosynaptic device based on a phase-change material, which comprises a substrate 1, a flat-layer waveguide 2, a periodic land waveguide 3 and a phase-change film 4; the slab layer waveguide 2 covers the whole area of the substrate 1, the periodic land waveguides 3 are periodically distributed on the upper side of the slab layer waveguide 2, and the phase change film 4 covers the surfaces of the slab layer waveguide 2 and the periodic land waveguides 3; the periodic land waveguide 3 includes waveguide units periodically distributed in the light beam propagation direction, each of which includes two identical ridge waveguides and a slit structure therebetween.
Taking the silicon waveguide width of the periodic land-type waveguide 3 as 140nm, the height of the slab layer waveguide 2 as 130nm, the groove width of the periodic land-type waveguide 3 as 100nm and the period of the periodic land-type waveguide 3 as 200nm, the duty ratio of the periodic land-type waveguide 3 as 50 percent and the period number as 30 percent as the initial section geometrical parameters of the nonvolatile multilevel adjustable photonic neurosynaptic device based on the phase change material, and selecting the chalcogenide phase change material Ge as the phase change film 2 Sb 2 Te 5 (GST). At this time, when the phase change film 4 is in different phase states (crystalline state, amorphous state), the difference of the optical output intensity is 70.7%.
Examples
As shown in FIG. 1, the multi-level tunable photonic neurosynaptic device of the present embodiment includes a substrate 1, a slab layer waveguide 2, a periodic land waveguide 3, and a phase change thin film 4; light output by the laser enters the photonic neurosynaptic device for transmission after passing through the coupling waveguide, different section geometric parameters of the slab layer waveguide 2 and the periodic land-type waveguide 3 affect the effective mode refractive index of a transmission mode in the waveguide, the regulation and control of the waveguide output intensity are realized by changing specific parameters, and the period and the duty ratio of the periodic land-type waveguide 3 also affect the waveguide output intensity; when the optical field is transmitted in the waveguide, part of the energy is coupled into the phase-change film 4, and the output intensity of the waveguide is regulated and controlled by changing the phase state (crystalline state and amorphous state) of the phase-change film 4. In the case of the initial cross-sectional geometry, the normalized electric field distribution of the phase-change film 4 in the amorphous and crystalline states is shown in fig. 2, and the transmission electric field distribution is shown in fig. 3.
For the conventional ridge waveguide, the mode energy distribution change caused by the phase change film changing the phase state is not obvious, and the non-volatile multi-level tunable photonic neurosynaptic device based on the phase change material can realize the obvious mode energy distribution change, as shown in fig. 4.
Compared with the conventional continuous waveguide structure, the phase-change-material-based nonvolatile multi-level tunable photonic neurosynaptic device has a larger output intensity difference when the phase-change material is in different phase states, and the specific result is shown in fig. 5.
Specifically, the silicon waveguide width of the periodic land waveguide 3 was changed to observe the change in the optical output intensity difference value when the phase change film 4 was in different phase states. The relationship between the silicon waveguide width of the periodic land waveguide 3 and the optical output intensity difference is shown in fig. 6. It was found that the light output intensity of the periodic land waveguide slowly decreased with increasing silicon waveguide width of periodic land waveguide 3 when GST was in the amorphous and crystalline states. And the optical output intensity difference at 140nm reached a maximum of 67.6%. The reason why the optical output intensity difference tends to decrease gradually over the entire modulation range is that when the silicon waveguide width of the periodic land waveguide 3 is small, the mode field cannot exist stably in the land region but exists in the slab layer waveguide 2, so that the interaction between the optical field and the phase change film 4 is reduced, and therefore the transmission loss caused by the GST material is reduced. It has furthermore been found that during the gradual reduction of the optical output intensity difference, there is also a local increase. This is because the real part of the effective refractive index of the transmission mode in the waveguide also gradually changes, and the coupling efficiency between the electric field and the periodic land-type waveguide 3 also exhibits periodic changes in the process of increasing the width of the silicon waveguide.
Specifically, the silicon waveguide width of the periodic land waveguide 3 was set to 140nm, and the height of the slab-layer waveguide 2 was changed to observe the change in the optical output intensity difference value when the phase-change film 4 was in a different phase state. It should be noted that the sum of the heights of slab-layer waveguide 2 and periodic land-type waveguide 3 is always 340nm. The height of the slab layer waveguide 2 is related to the optical output intensity difference as shown in fig. 7. When the height of the slab-layer waveguide 2 is less than 60nm, the light output intensity of the periodic land waveguide is very low regardless of whether GST is in the aGST state or the cGST state. This is because the waveguide having the height of the slab-layer waveguide 2 smaller than 60nm cannot limit the electric field on the premise that the silicon waveguide width of the periodic land-type waveguide 3 is 140nm, resulting in a corresponding waveguide mode having a large mode loss. When the slab-layer waveguide 2 is increased in height so that the waveguide can confine the electric field, the light output intensity of the periodic land waveguide will gradually increase when the GST is in the a GST state or the c GST state. The increase in height of slab layer waveguide 2 allows more of the optical field to be distributed in the slab layer, reducing the interaction of the optical field with the GST, and thus reducing the transmission loss due to depletion of the GST material. Finally, when the silicon waveguide width of the periodic land waveguide 3 is 140nm and the height of the slab waveguide 2 is 130nm, the optical output intensity difference reaches a maximum value of 70.7%.
Specifically, when the GST is in a different phase, the optical output intensity of the periodic land waveguide gradually decreases as the groove width of the periodic land waveguide 3 increases. When the silicon waveguide width of the periodic land waveguide 3 was 140nm, the height of the slab layer waveguide 2 was 130nm, and the groove width of the periodic land waveguide 3 was 100nm, the optical output intensity difference reached a maximum of 70.7%. As shown in fig. 8.
Specifically, since the output intensity of the periodic land waveguide is related to the period of the sub-wavelength grating, adjusting the period of the periodic land waveguide 3 can also significantly affect the difference in optical output intensity when the GST is in different phases, as shown in FIG. 9. The optical output intensity difference of the periodic land waveguide first decreases and then increases when the GST is in the a GST state with increasing periodicity. This is because the effective refractive index of the propagating mode in the waveguide is determined after determining the values of the silicon waveguide width of periodic land waveguide 3, the height of slab-layer waveguide 2, and the groove width of periodic land waveguide 3. When the real part of the effective index of the propagating mode in the waveguide is related to the grating period to satisfy the bragg reflection condition, little light energy can pass through the periodic land waveguide. This can also be supported by another detail in fig. 9. When the phase state of the phase change film 4 is amorphous, the optical output intensity of the periodic land waveguide should be greater than that of the waveguide when the phase state of the phase change film 4 is crystalline, because the optical loss of cGST is much greater than atst. However, the difference in optical output intensity of the periodic land waveguide when the GST is in a different phase is negative at a period of 310 nm. This is because when the phase change material is a GST, the real part of the effective refractive index of the propagating mode in the waveguide satisfies the bragg reflection condition in relation to the grating period, resulting in a significant reduction in optical output intensity. Finally, when the width of the silicon waveguide of the periodic land waveguide 3 is 140nm, the height of the slab waveguide 2 is 130nm, the width of the groove of the periodic land waveguide 3 is 100nm, and the period of the periodic land waveguide 3 is 200nm, the difference in optical output intensity reaches a maximum value of 70.7%.
Specifically, varying the duty cycle of the periodic land waveguide 3 affects the average refractive index of the grating, which in turn affects the coupling efficiency between the propagating mode in the waveguide and the periodic land waveguide 3. Thus, it can be seen in FIG. 10 that the periodic land waveguide has a peak in the light output intensity difference when the GST is in different phases. When the silicon waveguide width of the periodic land waveguide 3 is 140nm, the height of the slab layer waveguide 2 is 130nm, the groove width of the periodic land waveguide 3 is 100nm, and the period of the periodic land waveguide 3 is 200nm, the output intensity difference reaches the maximum value, i.e., 70.7% when the duty ratio of the periodic land waveguide 3 is 50%.
In particular, fig. 11 shows the effect of the number of periods (period numbers) on the light output intensity of the periodic land waveguide. Since the optical switch has a certain transmission loss, the transmittance of the periodic land waveguide gradually decreases as the transmission distance increases when the GST is in the amorphous and crystalline states. However, the modes propagating in the periodic land waveguide have different transmission losses when the GST is in the amorphous and crystalline states, and thus the rate at which the light output intensity of the SWGST waveguide drops is different when the GST is in the different phases. As can be seen from fig. 11, when the width of the silicon waveguide of the periodic land waveguide 3 is 140nm, the height of the slab layer waveguide 2 is 130nm, the width of the slot of the periodic land waveguide 3 is 100nm, and the period of the periodic land waveguide 3 is 200nm, when the duty ratio of the periodic land waveguide 3 is 50% and the period number is 30, the output intensity difference reaches the maximum value, which is 70.7%, and is almost twice as large as the conventional structure, and the method is suitable for the design of a multilevel adjustable nonvolatile optical switch in practical application.
In the multistage dimmable switch, the optical refractive index of the phase change film 4 can be changed by changing the degree of crystallization of the phase change film 4, wherein the relationship between the degree of crystallization and the optical refractive index satisfies:
wherein p represents the degree of crystallization, e a And e c Preferably, the phase change material used in the present invention is GST, and the refractive indices of the crystalline state and the amorphous state are 4.6+0.18i and 7.2+1.9i, respectively. Simulation results show that a multi-level dimmable switch can control the light output intensity at 65 different levels, corresponding to approximately 6-bit programming resolution, as shown in fig. 12. The nonvolatile multi-level adjustable photon nerve synapse device based on the phase change material has the advantages ofThe invention has large optical output intensity regulation range, can realize 64-level (6-bit) coding on the basis of ensuring that the output intensity difference of adjacent regulation levels is 1 percent, and is twice as large as other output intensity regulation type nonvolatile optical switches.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A nonvolatile multi-level adjustable photonic neurosynaptic device based on a phase change material is characterized by comprising a substrate (1), a slab-layer waveguide (2), periodic land waveguides (3) and a phase change film (4), wherein the slab-layer waveguide (2) covers the whole substrate (1) area, the periodic land waveguides (3) are distributed on the upper side of the slab-layer waveguide (2), and the phase change film (4) covers the surface of the periodic land waveguides (3); the periodic land waveguide (3) comprises waveguide units which are periodically distributed along the propagation direction of the light beam, and each waveguide unit comprises two identical ridge waveguides and a slit structure between the two ridge waveguides.
2. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein the period, duty cycle and number of periods of the periodic land waveguide (3) are selected such that the difference in coupling efficiency of the transmission mode within the waveguide and the periodic structure is maximized when the phase change material is in different phase states.
3. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein the cross-sectional geometry of the slab-layer waveguide (2) and the periodic land waveguide (3) is selected such that the mode loss difference of the transmission modes within the waveguides is maximized when the phase change material is in different phase states.
4. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein cross-sectional geometrical parameters of the periodic land waveguide (3) and the phase change thin film (4) are fixed in the propagation direction.
5. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein the periodicity of the periodic land-type waveguide (3) is a fixed period or a mixture of multiple periods.
6. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein the phase change thin film (4) is further distributed on the surface of the slab layer waveguide (2).
7. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein the material of the phase change thin film (4) is a chalcogenide phase change material Ge 2 Sb 2 Te 5 。
8. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein the slab-layer waveguide (2) and the periodic land waveguide (3) are silicon waveguides or silicon nitride waveguides.
9. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1 or 6, wherein the cladding of the periodic land-type waveguide (3) is air or silica.
10. The non-volatile multilevel tunable photonic neurosynaptic device according to claim 1, wherein an oxidation prevention layer is further covered on the phase change thin film (4), and the material is gold or ITO.
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