On-chip photonic nonlinear activation function device and method of using the same

Abstract

The present invention provides an on-chip photon nonlinear activation function device and a method for using the same, comprising: a substrate, an insulating layer, an n-type doped silicon photonic structure, a first electrode, an isolation layer, a second electrode, and a p-type doped two-dimensional material layer; based on the coupling effect between the two-dimensional material layer and the silicon photonic structure, the bias voltage provided by the first electrode and the second electrode to the heterojunction device formed by the two-dimensional material layer and the silicon photonic structure is adjusted through a specific photocurrent detection feedback control mechanism, so as to change the carrier concentration in the heterojunction device to adjust the Fermi level of the two-dimensional material layer and the refractive index of the silicon photonic structure, thereby realizing the function of modulating the input optical signal and the function of detecting and acquiring the nonlinear activation function. The technical solution of the present invention can realize the modulation and detection of optical signals, and can achieve high integration, low power consumption and ultra-fast response speed.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic devices and semiconductor manufacturing technology, and in particular to an on-chip photon nonlinear activation function device and a method for using the same. Background Art

[0002] In recent years, artificial neural networks have developed rapidly and can now assist people in completing a variety of complex tasks such as face recognition, video synthesis, text sentiment analysis, autonomous driving, disease identification, and quantitative financial transactions. However, with the explosive growth of information data processing, neural networks based on electronic computers have also encountered bottlenecks in energy consumption and data processing speed in hardware. At the same time, photonic neural networks (ONNs) composed of optoelectronic devices have attracted widespread attention. Optoelectronic devices use photons as information carriers, with advantages such as greater bandwidth, higher information capacity, and lower power consumption, showing the potential to break the bottleneck of computer neural network technology. With the development of silicon photonics, integrated photonic neural networks have achieved exciting results in artificial intelligence applications, including symbol recognition, vowel analysis, image classification, etc., marking the advent of a new era of information and communication technology.

[0003] In neural networks, nonlinear activation functions are a crucial component that introduces nonlinearity, enabling the network to perform complex tasks and having an important impact on training speed and computational accuracy. For photonic neural networks, the current academic community is committed to developing on-chip photonic activation functions in all-optical or electro-optical form, and on-chip photonic activation function devices are in the initial stage of research. For all-optical activation functions, the lack of electrical components can help reduce the complexity of network design, but the optical power threshold is relatively large. Common electro-optical activation function device schemes can achieve reconfigurability, but due to the photoelectric conversion, it brings higher power consumption and time delay. At the same time, the phase shift of the photonic activation function is usually ignored, and the photonic neural network is actually complex-valued in nature. Therefore, many classical activation functions used for real-valued neural networks are no longer applicable to complex-valued photonic neural networks. At the same time, photonic activation function devices need to achieve lower power consumption, shorter delays, and higher reconfigurability. Summary of the invention

[0004] Based on the above technical problems of the prior art, the present invention provides an on-chip photonic nonlinear activation function device and a method for using the same.

[0005] The present invention provides an on-chip photon nonlinear activation function device, comprising: a substrate, an insulating layer, an n-type doped silicon photonic structure, a first electrode, an isolation layer, a second electrode and a p-type doped two-dimensional material layer;

[0006] The insulating layer is arranged on the substrate to isolate the substrate from the silicon photonic structure; the silicon photonic structure is arranged on the insulating layer; the first electrode is arranged on one side of the upper surface of the silicon photonic structure to provide a bias voltage to the silicon photonic structure; the isolation layer is arranged on the other side of the upper surface of the silicon photonic structure to isolate the silicon photonic structure from the second electrode; the second electrode is arranged on the isolation layer to provide a bias voltage to the two-dimensional material layer; the two-dimensional material layer is arranged on the isolation layer, the second electrode and the silicon photonic structure, and is in contact with the middle part of the silicon photonic structure, and the two-dimensional material layer is coupled with the silicon photonic structure to form a heterojunction device;

[0007] Among them, based on the coupling effect between the two-dimensional material layer and the silicon photonic structure, the bias voltage provided by the first electrode and the second electrode to the heterojunction device is adjusted through a specific photocurrent detection feedback control mechanism, so as to change the carrier concentration in the heterojunction device to adjust the Fermi level of the two-dimensional material layer and the refractive index of the silicon photonic structure, thereby realizing the function of modulating the input light signal and detecting and acquiring the nonlinear activation function.

[0008] According to an on-chip photon nonlinear activation function device provided by the present invention, the working principle of the on-chip photon nonlinear activation function device specifically includes:

[0009] When the bias voltage of the heterojunction device is a forward bias voltage, the Fermi level of the two-dimensional material layer becomes higher and the optical absorption capability becomes weaker, the width of the space charge region of the silicon photonic structure becomes narrower, the equivalent doping concentration increases, and the refractive index becomes smaller, thereby realizing the function of modulating the input optical signal;

[0010] When the bias voltage of the heterojunction device is reverse bias voltage, the Fermi level of the two-dimensional material layer becomes lower and the optical absorption ability becomes stronger, the width of the space charge region of the silicon photonic structure becomes wider, the equivalent doping concentration decreases and the refractive index becomes larger, thereby realizing the function of detecting the input optical signal and obtaining the nonlinear activation function.

[0011] According to an on-chip photonic nonlinear activation function device provided by the present invention, the silicon photonic structure comprises a first silicon photonic structure, a second silicon photonic structure and a third silicon photonic structure;

[0012] The first part of the silicon photonic structure is an n++-doped silicon waveguide, which is located on the first side of the silicon photonic structure; the second part of the silicon photonic structure is an undoped silicon waveguide, which is located on the second side of the silicon photonic structure; the third part of the silicon photonic structure is an n-doped special structure, which is located in the middle of the silicon photonic structure;

[0013] The two-dimensional material layer is in contact with the third portion of the silicon photonic structure, but is not in contact with the first portion of the silicon photonic structure and is not in contact with the second portion of the silicon photonic structure.

[0014] According to an on-chip photonic nonlinear activation function device provided by the present invention, the first electrode is arranged on the first part of the silicon photonic structure, and there is a gap between the first electrode and the two-dimensional material layer;

[0015] The second electrode is disposed on the second portion of the silicon photonic structure and is not in direct contact with the second portion of the silicon photonic structure.

[0016] According to an on-chip photonic nonlinear activation function device provided by the present invention, the isolation layer includes an oxide layer, and the oxide layer includes aluminum oxide or chromium oxide.

[0017] According to an on-chip photonic nonlinear activation function device provided by the present invention, the silicon photonic structure includes at least one of the following: a microring resonator, a Magnetron interferometer, a two-dimensional photonic crystal and a disk structure.

[0018] According to an on-chip photonic nonlinear activation function device provided by the present invention, the two-dimensional material layer is formed by a single layer or a few layers of a two-dimensional material, or is formed by a van der Waals heterojunction consisting of at least two single layers or a few layers of two-dimensional materials;

[0019] The two-dimensional material includes at least one of the following: graphene, tungsten disulfide, tungsten diselenide, tungsten telluride, molybdenum disulfide, molybdenum diselenide and molybdenum ditelluride.

[0020] According to an on-chip photonic nonlinear activation function device provided by the present invention, the substrate is formed of single crystal silicon, the insulating layer is formed of silicon dioxide, and the thickness of the insulating layer is greater than or equal to 1 micron and less than or equal to 2 microns.

[0021] The present invention also provides a photoelectric device, comprising any one of the above on-chip photonic nonlinear activation function devices.

[0022] The present invention also provides a method for using an on-chip photon nonlinear activation function device, which is applied to any of the above on-chip photon nonlinear activation function devices and introduces nonlinearity through a specific photocurrent detection feedback control mechanism, the method comprising:

[0023] Step 1, constructing an integrated circuit that can apply a bias voltage and measure a photocurrent, and integrating the integrated circuit with an on-chip photonic nonlinear activation function device, wherein the integrated circuit is used to adjust the bias voltage of the on-chip photonic nonlinear activation function device based on a change in the photocurrent;

[0024] Step 2, programming the transfer function between the bias voltage and the tuning voltage into an integrated circuit integrated with the on-chip photonic nonlinear activation function device;

[0025] Step 3, generating an activation function by using a heterojunction device of a transfer function;

[0026] Step 4, by scanning the photocurrent and transmittance of the heterojunction device under different voltages and light input powers, the relationship between transmittance and light input power is established, and the photon nonlinear activation function is obtained therefrom.

[0027] The present invention provides an on-chip photonic nonlinear activation function device and a method for using the same. The on-chip photonic nonlinear activation function device comprises a substrate, an insulating layer, an n-type doped silicon photonic structure, a first electrode, an isolation layer, a second electrode and a p-type doped two-dimensional material layer; the insulating layer is arranged on the substrate to isolate the substrate from the silicon photonic structure; the silicon photonic structure is arranged on the insulating layer; the first electrode is arranged on one side of the upper surface of the silicon photonic structure to provide a bias voltage to the silicon photonic structure; the isolation layer is arranged on the other side of the upper surface of the silicon photonic structure to isolate the silicon photonic structure from the second electrode; the second electrode is arranged on the isolation layer to provide a bias voltage to the two-dimensional material layer; the two-dimensional material layer is arranged on the isolation layer, the second electrode and the silicon photonic structure, and is in contact with the middle part of the silicon photonic structure, and the two-dimensional material layer is coupled with the silicon photonic structure to form a heterojunction device; wherein the bias voltage of the heterojunction device can be adjusted by the first electrode and the second electrode to adjust the Fermi level of the two-dimensional material layer and the refractive index of the silicon photonic structure. In this way, the coupling between the two-dimensional material layer and the silicon photonic structure can change the optical absorption capacity of the two-dimensional material layer and the refractive index (plasma dispersion effect) of the silicon photonic structure, thereby realizing the detection and modulation of the optical signal. At the same time, by utilizing the coupling between the silicon photonic structure and the two-dimensional material layer, through a specific photocurrent detection feedback control mechanism, it is not only possible to realize a highly reconfigurable complex (nonlinear) photon activation function containing phase information, but also to achieve high integration, low power consumption and ultra-fast response speed, and to be easily compatible with CMOS integration processes, which is conducive to large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a schematic diagram of the cross-sectional structure of an on-chip photonic nonlinear activation function device provided by an embodiment of the present invention;

[0030] Figure 2 is a top view of an on-chip photonic nonlinear activation function device provided by an embodiment of the present invention;

[0031] Figure 3This is one of the flow charts of the method for using the on-chip photonic nonlinear activation function device provided by an embodiment of the present invention;

[0032] Figure 4 This is the second flow chart of the method for using the on-chip photonic nonlinear activation function device provided in an embodiment of the present invention.

[0033] Reference numerals:

[0034] 101: substrate; 102: insulating layer; 103, 104, 105: silicon photonic structure; 106: first electrode; 107: isolation layer; 108: second electrode; 109: two-dimensional material layer. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] On-chip photonic nonlinear activation function devices are devices that introduce nonlinearity and enable photonic neural networks to perform complex tasks, and have an important impact on training speed and computational accuracy. Currently, the academic community is committed to developing on-chip photonic activation functions in all-optical or electro-optical forms, but it is still in the initial stage of research. For all-optical activation functions, the lack of electrical components can help reduce the complexity of network design, but the optical power threshold is relatively large. Common electro-optical activation function device schemes can achieve reconfigurability, but due to the photoelectric conversion, it brings higher power consumption and time delay. At the same time, the phase shift of the photonic activation function is usually ignored, and the photonic neural network actually has a complex value. Therefore, many classical activation functions used for real-valued neural networks are no longer applicable to complex-valued photonic neural networks. At the same time, photonic activation function devices need to achieve smaller power thresholds, lower power consumption, shorter delays, smaller sizes, and higher reconfigurability.

[0037] Based on the above technical problem, an embodiment of the present invention provides an on-chip photonic nonlinear activation function device and a method of using the same, which can solve the technical problem.

[0038] Among them, two-dimensional materials have excellent mechanical, thermal, optical and electrical properties, and have become an effective means to solve this problem. First, graphene is a very representative two-dimensional material, whose single-layer carbon atoms are arranged in a honeycomb lattice with a linear, massless, zero-band structure. Graphene has a zero-gap band structure, and the generation of charge carriers in it can be achieved by light absorption over an ultra-wide energy spectrum (from ultraviolet to infrared to terahertz band), which is unmatched by any other material. At the same time, graphene has ultrafast carrier dynamics, wavelength-independent absorption, tunable optical properties through electrostatic doping, low dissipation rate and high mobility, and the ability to confine electromagnetic energy to an unprecedentedly small volume. In particular, high carrier mobility enables ultrafast conversion of photons or plasmas into current or voltage. Graphene is compatible with highly mature silicon-based electronic and photonic platforms, making it an important material for low-cost, large-scale integration into optoelectronic networks and multi-pixel CMOS (Complementary Metal Oxide Semiconductor) readout circuits.

[0039] Secondly, transition metal sulfides (TMDCs) are also a very important two-dimensional material. Its chemical expression is MX2, where M represents transition metals (Mo, W, etc.) and X represents chalcogens (S, Se, Te). Its direct band gap is in the range of 1.0-2.5eV. The band gap structure of TMDCs can also be adjusted by various methods, such as changing the number of layers, inducing element defects, or forming van der Waals heterojunctions with other two-dimensional materials, thereby having a larger operating wavelength range. Due to the exciton characteristics, large binding energy and strong light-matter interaction, single-layer TMDCs have unique photoluminescence (PL) characteristics compared with multilayer films. The position of its PL resonance peak is around 590-750 nanometers and the line width is 2-6meV. At the same time, strong light absorption (>10%) has also been found in single-layer TMDCs, making them good candidate materials for photodetection devices. Finally, the destruction of the inversion symmetry of TMDCs will lead to large optical nonlinearity, making optical nonlinear functions and all-optical signal processing possible. Since two-dimensional materials are thin film materials, the interaction distance of light is short when it propagates in the thin film, which limits the modulation and detection of light by two-dimensional materials.

[0040] On the other hand, although silicon-based optoelectronics is very promising in the field of on-chip photonic neural networks, a complete neural network requires both linear operations and nonlinear activation of light, which is difficult to achieve on a pure silicon-based platform. In order to solve this problem, a heterojunction integrating two-dimensional materials and silicon photonic structures may be an ideal solution. Based on this, the present application integrates two-dimensional materials with silicon photonic structures to realize highly reconfigurable, highly integrated, low-power and ultra-fast response speed on-chip photonic nonlinear activation function devices.

[0041] The solution provided by the embodiment of the present invention will be explained and illustrated in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Figure 1 is a schematic diagram of a cross-sectional structure of an on-chip photonic nonlinear activation function device provided by an embodiment of the present invention, Figure 2 is a top view of an on-chip photonic nonlinear activation function device provided by an embodiment of the present invention (the reference numerals of some structures are not shown), see Figure 1 and Figure 2 As shown, the on-chip photonic nonlinear activation function device includes: a substrate 101, an insulating layer 102, an n-type doped silicon photonic structure 103 / 104 / 105, a first electrode 106, an isolation layer 107, a second electrode 108 and a p-type doped two-dimensional material layer 109.

[0043] Among them, the above-mentioned insulating layer 102 is arranged on the substrate 101, and is used to isolate the substrate 101 from the silicon photonic structure to avoid current leakage in the silicon photonic structure, thereby reducing energy consumption. As an option, the substrate 101 can be formed of single crystal silicon, and the shape and size of the substrate 101 can be set according to actual conditions. For the insulating layer 102, the insulating layer 102 can be formed of silicon dioxide; the shape and size of the insulating layer 102 can also be set according to actual conditions, and the size of the insulating layer 102 can be greater than or equal to the size of the substrate 101. As for the thickness of the insulating layer 102, as an option, the thickness L of the insulating layer 102 can be greater than or equal to 1 micron and less than or equal to 2 microns, which is expressed by the formula: 1μm≤L≤2μm.

[0044] The silicon photonic structure 103 / 104 / 105 is disposed on the insulating layer 102. Optionally, the silicon photonic structure 103 / 104 / 105 may be composed of three silicon photonic structures, such as a first silicon photonic structure 103, a second silicon photonic structure 105 and a third silicon photonic structure 104.

[0045] Among them, the first part of the silicon photonic structure 103 is an n++ doped silicon waveguide, which is located on the first side of the silicon photonic structure; the first side here, for example, taking the cross-sectional view of the on-chip photonic nonlinear activation function device as an example, can be the left side of the entire silicon photonic structure. The n-doping concentration in this part of the silicon photonic structure is relatively high, which is recorded as n++ doping. The n-doping here, also known as electron doping, is achieved by adding a small amount of reducing-active substances (i.e., n-type dopants) to the organic semiconductor material, thereby introducing additional electrons into the organic semiconductor, so as to achieve precise control of the carrier (electron) concentration in the organic semiconductor and improve the device performance.

[0046] The second part of the silicon photonic structure 105 is an undoped silicon waveguide, located on the second side of the silicon photonic structure; the second side here is a side opposite to the first side, for example, the first side is the left side of the entire silicon photonic structure, then the second side here can be the right side of the entire silicon photonic structure, that is, the second part of the silicon photonic structure 105 is a silicon photonic structure located on the right side of the entire silicon photonic structure. This part of the silicon photonic structure is an undoped structure.

[0047] The third silicon photonic structure 104 is a special structure of n-doping, and is located in the middle of the silicon photonic structure; that is, the third silicon photonic structure 104 is located between the first silicon photonic structure 103 and the second silicon photonic structure 105, and is in direct contact with the two adjacent silicon photonic structures. The n-doping concentration in this part of the silicon photonic structure is less than the n-doping concentration in the first part of the silicon photonic structure 103, and is recorded as n-doping.

[0048] The first electrode 106 is disposed on one side of the upper surface of the silicon photonic structure, and is used to provide a bias voltage to the silicon photonic structure; optionally, the first electrode 106 can be disposed on the first portion of the silicon photonic structure 103, that is, the first electrode 106 is disposed on the upper left of the entire silicon photonic structure. After the external power supply device provides the bias voltage to the first electrode 106, the first electrode 106 can apply the bias voltage to the silicon photonic structure to change the concentration of carriers in the silicon photonic structure.

[0049] The isolation layer 107 is disposed on the other side of the upper surface of the silicon photonic structure, and is used to isolate the silicon photonic structure from the second electrode 108; optionally, the isolation layer 107 is disposed above the second portion of the silicon photonic structure 105 and part of the third portion of the silicon photonic structure 104. The isolation layer 107 is mainly used to isolate the third portion of the silicon photonic structure from the second electrode 108 located above the isolation layer 107, which can prevent the second electrode 108 from applying a bias voltage to the silicon photonic structure, thereby better controlling the bias voltage of the two-dimensional material layer and the silicon photonic structure. The shape and size of the isolation layer 107 can be determined according to the shape and size of the contact surface between the isolation two-dimensional material layer and the second electrode 108 and the third portion of the silicon photonic structure.

[0050] The second electrode 108 is disposed on the isolation layer 107 to provide a bias voltage to the two-dimensional material layer; optionally, the second electrode 108 is not in contact with the first electrode 106, and the second electrode 108 is disposed on the isolation layer 107 and covers a portion of the isolation layer 107, that is, the second electrode 108 and the isolation layer 107 are disposed at the upper right of the entire silicon photonic structure. After the external power supply device provides the bias voltage to the second electrode 108, the second electrode 108 can apply the bias voltage to the two-dimensional material layer to change the concentration of carriers in the two-dimensional material layer.

[0051] The above-mentioned two-dimensional material layer 109 is arranged on the isolation layer 107, the second electrode 108 and the silicon photonic structure, and is in contact with the middle part of the silicon photonic structure. The above-mentioned two-dimensional material layer 109 is coupled with the silicon photonic structure to form a heterojunction device. As an option, the two-dimensional material layer 109 includes a two-dimensional material, and the two-dimensional material may include at least one of the following: graphene, tungsten disulfide, tungsten diselenide, tungsten telluride, molybdenum disulfide, molybdenum diselenide and molybdenum ditelluride. In addition, the two-dimensional material layer is specifically arranged above the second electrode 108, the isolation layer 107 and the silicon photonic structure. As an optional embodiment, the two-dimensional material layer is in contact with the third part of the silicon photonic structure, and is not in contact with the first part of the silicon photonic structure and is not in contact with the second part of the silicon photonic structure. The two-dimensional material layer avoids direct contact with the second part of the silicon photonic structure through the second electrode 108 and the isolation layer 107, and the two-dimensional material layer does not cover the first part of the silicon photonic structure to avoid direct contact with the first part of the silicon photonic structure. In addition, the shape and size of the above-mentioned two-dimensional material layer can be set according to actual conditions. Taking the cross-sectional view of the on-chip photonic nonlinear activation function device as an example, the shape of the two-dimensional material layer can be an irregular shape.

[0052] The above-mentioned two-dimensional material layer 109 and silicon photonic structure 103 / 104 / 105 can be strongly coupled to form a heterojunction device. After the first electrode 106 and the second electrode 108 are powered on, based on the coupling effect between the two-dimensional material layer 109 and the silicon photonic structure 103 / 104 / 105, the bias voltage provided by the first electrode 106 and the second electrode 108 to the heterojunction device is adjusted through a specific photocurrent detection feedback control mechanism to change the carrier concentration in the heterojunction device to adjust the Fermi level of the two-dimensional material layer 109 and the refractive index of the silicon photonic structure 103 / 104 / 105, thereby realizing the function of modulating the input optical signal and detecting and acquiring the nonlinear activation function.

[0053] Specifically, the bias voltages of the first electrode 106 and the second electrode 108 can be adjusted by detecting the photocurrent in the heterojunction device, and the bias voltage applied by the first electrode 106 to the silicon photonic structure and the bias voltage applied by the second electrode 108 to the two-dimensional material layer can be adjusted. In this way, the carrier concentration in the heterojunction device formed by the coupling of the silicon photonic structure and the two-dimensional material layer can be adjusted, and then the Fermi level (optical absorption capacity) of the two-dimensional material and the refractive index (plasma dispersion effect) of the silicon photonic structure can be adjusted to achieve the dual functions of modulation and detection of optical signals. That is, the on-chip photon nonlinear activation function device can not only realize the function of the modulator, that is, realize the modulation of the optical signal, but also realize the function of the detector, that is, realize the detection of the optical signal and obtain the photon nonlinear activation function. At the same time, through a specific photocurrent detection feedback control mechanism, the heterojunction device with the dual functions of modulation and detection can not only realize a highly reconfigurable complex photon activation function containing phase information, but also achieve higher integration, lower power consumption and shorter delay.

[0054] Furthermore, in this embodiment, a two-dimensional material layer is made on the silicon photonic structure, which utilizes the strong light absorption characteristics of the two-dimensional material, and the two-dimensional material surface is naturally passivated without hanging bonds, so it is easy to integrate with the silicon waveguide. Through the coupling effect of the two-dimensional material and the silicon photonic structure, the carrier concentration in the heterojunction device is adjusted by electrical control, and then the Fermi level (optical absorption) of the two-dimensional material and the refractive index (plasma dispersion effect) of the silicon photonic structure are regulated to achieve the modulation and detection of the optical signal. In this case, based on a specific photocurrent detection feedback control mechanism, a heterojunction device with dual-function integration can not only realize a highly reconfigurable complex photon activation function containing phase information, but also achieve higher integration, lower power consumption and shorter delay. Typically, the above-mentioned silicon photonic structure is composed of a silicon waveguide with a thickness of 220 nanometers or 150 nanometers and a width of 400 nanometers-1500 nanometers. When the wavelength of the excitation light is in the near-infrared band, the on-chip photonic nonlinear activation function device can modulate and detect the signal light, and convert the optical signal into an electrical signal using the photoconductivity effect.

[0055] As can be seen from the above description, the on-chip photonic nonlinear activation function device provided in this embodiment realizes modulation or detection of optical signals by designing a suitable silicon photonic structure, using two-dimensional materials as gain materials, coupling with the silicon photonic structure, and regulating the heterojunction device formed by the two-dimensional material layer and the silicon photonic structure. Due to the strong coupling effect between the two-dimensional material and the silicon photonic structure, and the excellent physical properties of the two-dimensional material, the on-chip photonic nonlinear activation function device based on the silicon photonic structure and the heterojunction formed by the two-dimensional material can not only realize a highly reconfigurable complex photon activation function containing phase information, but also realize higher integration, lower power consumption and shorter delay, thereby realizing the function of the on-chip optical nonlinear activation function.

[0056] In this embodiment, the on-chip photonic nonlinear activation function device includes a substrate, an insulating layer, an n-type doped silicon photonic structure, a first electrode, an isolation layer, a second electrode and a p-type doped two-dimensional material layer; the insulating layer is arranged on the substrate to isolate the substrate from the silicon photonic structure; the silicon photonic structure is arranged on the insulating layer; the first electrode is arranged on one side of the upper surface of the silicon photonic structure to provide a bias voltage to the silicon photonic structure; the isolation layer is arranged on the other side of the upper surface of the silicon photonic structure to isolate the silicon photonic structure from the second electrode; the second electrode is arranged on the isolation layer to provide a bias voltage to the two-dimensional material layer; the two-dimensional material layer is arranged on the isolation layer, the second electrode and the silicon photonic structure, and is in contact with the middle part of the silicon photonic structure, and the two-dimensional material layer is coupled with the silicon photonic structure to form a heterojunction device; wherein the bias voltage of the heterojunction device can be adjusted by the first electrode and the second electrode to adjust the Fermi level of the two-dimensional material layer and the refractive index of the silicon photonic structure, so as to realize the function of modulating the input optical signal and the function of detecting and acquiring the nonlinear activation function. In this way, the coupling between the two-dimensional material layer and the silicon photonic structure can change the optical absorption capacity of the two-dimensional material layer and the refractive index (plasma dispersion effect) of the silicon photonic structure, thereby realizing the detection and modulation of the optical signal. At the same time, by utilizing the coupling between the silicon photonic structure and the two-dimensional material layer, through a specific photocurrent detection feedback control mechanism, it is not only possible to realize a highly reconfigurable complex (nonlinear) photon activation function containing phase information, but also to achieve high integration, low power consumption and ultra-fast response speed, and to be easily compatible with CMOS integration processes, which is conducive to large-scale production and application.

[0057] The specific working principle of the on-chip photonic nonlinear activation function device is explained below.

[0058] In one embodiment, the working principle of the above-mentioned on-chip photonic nonlinear activation function device specifically includes: when the bias voltage of the heterojunction device is a forward bias voltage, the Fermi level of the two-dimensional material layer 109 becomes higher and the optical absorption capability becomes weaker, the width of the space charge region of the silicon photonic structure 103 / 104 / 105 becomes narrower, the equivalent doping concentration increases, and the refractive index becomes smaller, thereby realizing the function of modulating the input optical signal; when the bias voltage of the heterojunction device is a reverse bias voltage, the Fermi level of the two-dimensional material layer 109 becomes lower and the optical absorption capability becomes stronger, the width of the space charge region of the silicon photonic structure 103 / 104 / 105 becomes wider, the equivalent doping concentration decreases, and the refractive index increases, thereby realizing the function of detecting the input optical signal and obtaining the nonlinear activation function.

[0059] Specifically, based on the coupling effect between the two-dimensional material layer 109 and the silicon photonic structure 103 / 104 / 105 and utilizing the principle of band engineering, the heterojunction device formed by the two-dimensional material layer 109 and the silicon photonic structure 103 / 104 / 105 can simultaneously realize the modulation and detection of optical signals.

[0060] The following is an explanation of the working principles of heterojunction devices under forward bias voltage and reverse bias voltage respectively.

[0061] When the heterojunction device is under a forward bias voltage (also called forward bias), both the p-type doped two-dimensional material layer and the n-type doped silicon photonic structure are positively charged. The positively charged p-type doped two-dimensional material layer has a higher Fermi level and a weaker optical absorption capacity. At this time, the width of the space charge region of the positively charged n-type doped silicon photonic structure is compressed, resulting in a higher equivalent doping concentration and a smaller refractive index for the n-type doped silicon photonic structure, which is more suitable for modulating the input optical signal, that is, it can realize the modulation function of the optical signal.

[0062] On the contrary, when the heterojunction device is under reverse bias voltage (also called reverse bias), the p-type doped two-dimensional material layer and the n-type doped silicon photonic structure are both negatively charged. The negatively charged p-type doped two-dimensional material layer has a lower corresponding Fermi level and a stronger corresponding light absorption capacity, that is, it exhibits increased optical absorption capacity. At this time, the width of the space charge region of the negatively charged n-type doped silicon photonic structure is wider, resulting in a smaller equivalent doping concentration and a larger refractive index of the n-type doped silicon photonic structure, which is more suitable for detecting the input light signal, that is, it can realize the detection function of the light signal, and then the nonlinear activation function can be obtained through the detected light signal, thereby realizing the function of the on-chip photonic nonlinear activation function device.

[0063] It can be understood that under a larger forward bias, the carrier concentration of the silicon photonic structure is higher and free carrier absorption is dominant. By utilizing the resonance effect, the modulation power is lower than that of the non-resonant structure, and due to the light capture inside the heterojunction device, the photoelectric detection of the heterojunction device is more sensitive, so that a smaller functional threshold can be achieved. In addition, during the tuning of the resonant wavelength, the phase of the output light is also modulated and is very sensitive to the position of the resonant wavelength, which can show complex modulation of the light field.

[0064] In this embodiment, the bias voltage of the heterojunction device is adjusted so that the concentration of carriers in the heterojunction device changes, thereby causing a change in the optical absorption capacity of the two-dimensional material layer and a change in the refractive index of the silicon photonic structure, thereby achieving modulation and detection of the input light signal through the change in the optical absorption capacity of the two-dimensional material layer and a change in the refractive index of the silicon photonic structure.

[0065] In one embodiment, the two-dimensional material layer 109 and the isolation layer 107, as well as the silicon photonic structure 103 / 104 / 105, form a van der Waals contact to form a heterojunction device, thereby simultaneously obtaining the excellent optoelectronic properties of silicon waveguides and two-dimensional materials.

[0066] In one embodiment, the first electrode 106 is disposed on the first portion of the silicon photonic structure 103 , and there is a gap between the first electrode 106 and the two-dimensional material layer 109 ; the second electrode 108 is disposed on the second portion of the silicon photonic structure 105 , and is not in direct contact with the second portion of the silicon photonic structure 105 .

[0067] Continue to see Figure 1 and Figure 2 As shown, the first electrode 106 and the second electrode 108 are arranged on both sides of the third part of the silicon photonic structure 104. Specifically, the first electrode 106 is arranged on the upper surface of the first part of the silicon photonic structure, and the size of the first electrode 106 can be set according to actual conditions, for example, it can be the same as the size of the first part of the silicon photonic structure. The above-mentioned two-dimensional material layer is arranged on the upper surface of the third part of the silicon photonic structure located in the middle, and there is a certain gap between the two-dimensional material layer and the first electrode 106, that is, there is no direct contact between the two-dimensional material layer and the first electrode 106, so that the bias voltage applied by the first electrode 106 can be avoided from being applied to the two-dimensional material layer, affecting the movement of materials in the two-dimensional material layer. The size of the gap can be set according to actual conditions, and is not specifically limited here.

[0068] In addition, the second electrode 108 can be arranged on the second portion of the silicon photonic structure, and specifically can be arranged on an isolation layer 107 covering the second portion of the silicon photonic structure. In this way, the isolation layer 107 can prevent the second electrode 108 from directly contacting the silicon photonic structure, causing the bias voltage applied by the second electrode 108 to be applied to the silicon photonic structure, thereby affecting the movement of matter in the silicon photonic structure.

[0069] During the operation of the above-mentioned on-chip photonic nonlinear activation function device, a suitable voltage can be applied between the first electrode 106, the second electrode 108 and the two-dimensional material layer. The voltage is mainly used to change the carrier concentration in the heterojunction device formed by the silicon photonic structure and the two-dimensional material layer, so as to adjust the Fermi level (light absorption capacity) of the two-dimensional material layer and the refractive index (plasma dispersion effect) of the silicon photonic structure, thereby realizing the modulation and detection functions of the optical signal.

[0070] For example, by adjusting the voltage between the first electrode 106 and the second electrode 108, the Fermi level (light absorption ability) of the two-dimensional material layer and the refractive index (plasma dispersion effect) of the silicon photonic structure are adjusted to adjust the photocurrent size, and then a specific photocurrent detection feedback control mechanism is used. The heterojunction device with the dual functions of modulation and detection can not only realize a highly reconfigurable complex photon activation function containing phase information, but also achieve higher integration, lower power consumption and shorter delay.

[0071] Specifically, the voltage between the first electrode 106 and the second electrode 108 actually regulates the intensity of the photocurrent in the heterojunction device.

[0072] In order to enhance the coupling between the two-dimensional material and the silicon photonic structure, so as to obtain the regulation of the carriers in the heterojunction and thus obtain a high-performance optoelectronic device, this embodiment will select different two-dimensional materials and their heterojunctions to integrate with the silicon photonic structure while optimizing the design of the silicon photonic structure. Therefore, further, when the Fermi level of the two-dimensional material layer is adjusted to be equal to the resonant wavelength of the silicon photonic structure, the coupling between the two is the strongest, and the on-chip photonic nonlinear activation function device can achieve the best performance.

[0073] In addition, in this embodiment, in addition to adjusting the size of the photocurrent, the optical waveguide mode of the silicon photonic structure can also be controlled to adjust the strength of the coupling effect between the silicon photonic structure and the two-dimensional material layer, thereby further realizing the regulation of the carrier effect in the heterojunction device. It should be noted that the scheme of adjusting the Fermi level (light absorption ability) of the two-dimensional material layer and the refractive index (plasma dispersion effect) of the silicon photonic structure by adjusting the voltage between the first electrode 106 and the second electrode 108 to adjust the size of the photocurrent, and the scheme of changing the carrier effect in the heterostructure by controlling the optical waveguide mode of the silicon photonic structure to adjust the strength of the coupling effect between the silicon photonic structure and the two-dimensional material layer, these two schemes can exist simultaneously or separately.

[0074] In this embodiment, the first electrode is arranged on the first part of the silicon photonic structure and has a gap between it and the two-dimensional material layer, and the second electrode is arranged on the second part of the silicon photonic structure and is not in direct contact with the second part of the silicon photonic structure. This can ensure that the first electrode accurately adjusts the carriers in the silicon photonic structure and the second electrode accurately adjusts the carriers in the two-dimensional material layer.

[0075] In one embodiment, the isolation layer 107 includes an oxide layer, and the oxide layer includes aluminum oxide or chromium oxide.

[0076] The isolation layer including an oxide layer can better protect the second electrode, improve the service life of the second electrode, and isolate the direct contact between the second electrode and the silicon photonic structure, so as to better control the bias of the two-dimensional material layer and the silicon photonic structure.

[0077] In one embodiment, the first electrode 106 and the second electrode 108 are both formed of gold or titanium, which can improve the conductivity of the first electrode 106 and the second electrode 108 .

[0078] The above can be used to change the carrier concentration in the silicon photonic structure and the two-dimensional material heterojunction by adjusting the voltage between the first electrode, the second electrode and the two-dimensional material layer, so as to adjust the Fermi level (light absorption ability) of the two-dimensional material layer and the refractive index (plasma dispersion effect) of the silicon photonic structure, thereby realizing modulation or detection function.

[0079] In one embodiment, the silicon photonic structure 103 / 104 / 105 includes at least one of the following: a microring resonator, a Magnetron interferometer, a two-dimensional photonic crystal, and a disk structure.

[0080] Taking the silicon photonic structure 103 / 104 / 105 as a microring resonator, the microring resonator includes a single straight waveguide and a ring waveguide. The optical signal transmitted to the on-chip photonic nonlinear activation function device is transmitted from one side of the single straight waveguide of the microring resonator and is transmitted from the other side of the single straight waveguide.

[0081] It can be understood that the single straight waveguide is used to propagate the optical signal from the optical waveguide or optical fiber connected to the single straight waveguide to the on-chip photonic nonlinear activation function device. The single straight waveguide is arranged on one side of the microring resonator, and the optical signal transmitted to the on-chip photonic nonlinear activation function device is transmitted from one side of the single straight waveguide and transmitted from the other side of the single straight waveguide. The single straight waveguide and the microring resonator are both made on a silicon substrate 101 and an insulating layer 102, i.e., silicon on insulator (SOI).

[0082] It should be noted that the silicon-on-insulator (SOI) platform is considered an important way to realize the next generation of chip-level optical interconnection networks. It can not only greatly expand the bandwidth of the system, but also use its tunable and powerful optical properties to improve the performance of existing modules and expand new functions, such as on-chip light sources, optical modulators, mode multiplexers, optical amplifiers and switches. However, it is difficult for SOI-based photonic devices to simultaneously achieve light modulation and detection. The main reasons are: silicon is an indirect electronic bandgap structure and cannot directly detect light above 1.2 microns; and the existing germanium used for light detection has technical challenges in growing on silicon substrate 101 due to the mismatch between the lattice constant and the thermal expansion coefficient, and the defects caused by defects during the crystal growth process will also limit the optical and electrical performance of such devices.

[0083] Therefore, the on-chip nonlinear activation function needs to study such on-chip optical modulation and detection dual-in-one devices based on heterojunctions formed by silicon photonic structures and two-dimensional materials. In this embodiment, the heterojunction device is formed by coupling the two-dimensional material and the silicon photonic structure, and the carrier concentration in the heterojunction device is adjusted by electrical control, thereby regulating the Fermi level (optical absorption) of the two-dimensional material and the refractive index (plasma dispersion effect) of the silicon photonic structure, thereby realizing the dual-function integration of modulation and detection of optical signals.

[0084] In one embodiment, the two-dimensional material layer 109 may be a single layer of graphene or transition metal dichalcogenides (TMDCs), or a van der Waals heterojunction.

[0085] In one embodiment, the two-dimensional material layer 109 is formed of a single layer or a few layers of a two-dimensional material, or is formed of a van der Waals heterojunction consisting of at least two single layers or a few layers of two-dimensional materials; the two-dimensional material includes at least one of the following: graphene, tungsten disulfide WS2, tungsten diselenide WSe2, tungsten telluride WTe2, molybdenum disulfide MoS2, molybdenum diselenide MoSe2, and molybdenum ditelluride MoTe2.

[0086] The above-mentioned van der Waals heterojunction can be formed by a single layer or a few layers of any two or three of graphene, tungsten disulfide WS2, tungsten diselenide WSe2, tungsten telluride WTe2, molybdenum disulfide MoS2, molybdenum diselenide MoSe2, and molybdenum ditelluride MoTe2 to form a van der Waals heterojunction.

[0087] That is to say, each of the above two-dimensional materials can be a single layer or a few layers. For example, if the two-dimensional material layer is formed by a two-dimensional material such as graphene, it can be formed by a single layer of graphene or a few layers of graphene. For another example, if the two-dimensional material layer is formed by a van der Waals heterojunction composed of two two-dimensional materials, graphene and tungsten disulfide, it can be formed by a single layer or a few layers of graphene and a single layer or a few layers of tungsten disulfide. The few layers here are generally greater than or equal to two layers, such as two layers, three layers, four layers, five layers, etc.

[0088] In this embodiment, the two-dimensional material layer can be formed by a single layer or a few layers of a two-dimensional material or a van der Waals heterojunction composed of multiple single layers or a few layers of two-dimensional materials. In this way, corresponding adaptive two-dimensional material layers can be produced in different scenarios, thereby realizing the functions of the corresponding on-chip nonlinear activation function device.

[0089] Further, it can be known from the description of the above embodiments that in the on-chip photonic nonlinear activation function device provided by the present embodiment, the optical signal is modulated and detected based on the carrier effect of the heterojunction composed of the silicon photonic structure and the two-dimensional material layer, which does not require complex material growth and micro-nano processing technology, and does not require high excitation light power and high bias voltage. The on-chip photonic nonlinear activation function device based on the heterojunction composed of the silicon photonic structure and the two-dimensional material layer has a light responsivity of up to 1A / W, a response time of the order of microseconds, an incident light power of the order of milliwatts, a modulation bias voltage of the order of sub-millivolts, and can simultaneously modulate and detect in the visible to near-infrared range, meeting the requirements of the working wavelength (1310 nanometers) of the cloud computing center, the modern communication band (1550 nanometers) and other bands (E, S, L, U bands). It can be seen that the on-chip photonic nonlinear activation function device of this embodiment does not require high excitation light power, which can overcome the disadvantages of the optical power threshold of the "all-optical activation function device" solution; does not require a high bias voltage, which can overcome the disadvantages of high power consumption and long delay of the "electro-optical activation function device" solution; and does not require the growth of high-quality III-V group materials on a silicon substrate, which can overcome the disadvantages of lattice mismatch, large power loss and difficulty in integration of the "hybrid III-V group on-chip photonic nonlinear activation function device" solution. Therefore, the on-chip photonic nonlinear activation function device provided by this embodiment is of great significance for the realization of high reconfigurability, integration, low power threshold, low power consumption, low delay and fast response time of photonic nonlinear activation function devices, and is of great significance for the development of on-chip optical networks and future high-performance computers.

[0090] On the other hand, an embodiment of the present invention further provides an optoelectronic device, which includes an on-chip photonic nonlinear activation function device as described in the above embodiment.

[0091] The optoelectronic device provided in this embodiment can be a CMOS device such as a spectrometer and a sensor, and of course can also be other optoelectronic devices including the above-mentioned on-chip photon nonlinear activation function device, and this embodiment does not impose specific restrictions on this.

[0092] On the other hand, Figure 3 is one of the flow charts of the method for using the on-chip photonic nonlinear activation function device provided by an embodiment of the present invention, such as Figure 3 As shown, an embodiment of the present invention further provides a method for using an on-chip photonic nonlinear activation function device, which can be applied to any of the above on-chip photonic nonlinear activation function devices, and introduces nonlinearity through a specific photocurrent detection feedback control mechanism, and the method includes the following steps:

[0093] Step 1: Build a circuit that can apply bias voltage V bias And measure the photocurrent I pThe integrated circuit is integrated with the on-chip photonic nonlinear activation function device, and the integrated circuit is used to p The bias voltage of the on-chip photonic nonlinear activation function device is adjusted by the change of

[0094] Step 2: Set the bias voltage V bias and tuning voltage V tune The transfer function V tune =H(I p , V bias ) programmed into an integrated circuit integrated with an on-chip photonic nonlinear activation function device;

[0095] Step 3, by using the transfer function V tune =H(I p , V bias ) heterojunction device generates an activation function;

[0096] Step 4, by scanning the photocurrent and transmittance of the heterojunction device under different voltages and light input powers, the relationship between transmittance and light input power is established, and the photon nonlinear activation function is obtained therefrom.

[0097] Among them, the above implementation transfer function V tune =H(I p , V bias ) is a photocurrent stabilization circuit, through which a relatively stable photocurrent can be obtained, thereby obtaining a relatively accurate photon nonlinear activation function.

[0098] The above steps 1-4 mainly illustrate the process of generating a photon nonlinear activation function on a single on-chip photon nonlinear activation function device. In actual situations, the photon nonlinear activation function can also be generated on multiple on-chip photon nonlinear activation function devices. The process may include the following steps:

[0099] Step 1: Build a circuit that can apply bias voltage V bias And measure the photocurrent I p The integrated circuit is integrated with the on-chip photonic nonlinear activation function device, and the integrated circuit is used to p The bias voltage of the on-chip photonic nonlinear activation function device is adjusted by the change of

[0100] Step 2: Set the bias voltage V bias and tuning voltage V tune The transfer function V tune =H(I p , V bias ) programmed into an integrated circuit integrated with an on-chip photonic nonlinear activation function device;

[0101] Step 3, through the two use transfer function V tune =H(I p , V bias ) heterojunction device generates an activation function;

[0102] Step 4, by scanning the photocurrent and transmittance of the two heterojunction devices (heterojunction device 1 and heterojunction device 2) at different voltages and light input powers, the relationship between the transmittance and the light input power is established, and two photon nonlinear activation functions are obtained therefrom.

[0103] Step 5, by applying different transfer functions associated with different photocurrent constants on the heterojunction device of a single on-chip photonic nonlinear activation function device, multiple special complex nonlinear activation functions with phase information can be generated. In addition, by changing the magnitude of the bias voltage or changing the input wavelength, a variety of different activation functions can be constructed.

[0104] In this embodiment, by utilizing the strong coupling between the silicon photonic structure and the two-dimensional material layer and through a specific photocurrent detection feedback control mechanism, not only can a highly reconfigurable complex photon activation function containing phase information be achieved, but also high integration, low power consumption and ultrafast response speed can be achieved, and it is easily compatible with CMOS integration technology, which is conducive to large-scale production and application.

[0105] Figure 4 This is the second flow chart of the method for using the on-chip photonic nonlinear activation function device provided by the embodiment of the present invention. Figure 4 As shown, the on-chip photonic nonlinear activation function device provided by an embodiment of the present invention is used after the on-chip photonic coherence matrix (linear) operation, and the operation result obtained at this time is a complex value; the complex value of the previous step is divided into a real part and an imaginary part, and nonlinear activation is performed separately, that is, a scheme of dynamically monitoring and adjusting the photocurrent is used to adjust the transmittance of the real part and the imaginary part and perform phase shifting; furthermore, the result of the previous step is squared and then combined and outputted, finally realizing the complete operation process of a photonic neural network.

[0106] Compared with other on-chip photonic nonlinear activation function devices, the on-chip photonic nonlinear activation function device provided in this example has the following advantages:

[0107] (1) Due to the strong coupling between the two-dimensional material layer and the silicon photonic structure, it is possible to adjust the Fermi level (optical absorption capacity) of the two-dimensional material layer and the refractive index (plasma dispersion effect) of the silicon photonic structure through the carrier effect, resulting in the heterojunction device formed by the two-dimensional material layer and the silicon photonic structure having the dual functions of a modulator and a detector. Through a specific photocurrent detection feedback control mechanism, the heterojunction device with dual-function characteristics can realize highly reconfigurable complex photon activation function operations containing phase information. In addition, both the two-dimensional material layer and the silicon photonic structure have ultrafast response rates, which ensures the fast response speed of the on-chip photonic nonlinear activation function device based on the heterojunction formed by the two-dimensional material layer and the silicon photonic structure.

[0108] (2) Both two-dimensional materials and silicon photonic structures have ultra-large bandwidths. Typical two-dimensional materials include graphene and TMDCs, among which: graphene has a zero-gap band structure, in which the generation of charge carriers can be achieved through light absorption over an ultra-wide energy spectrum (from ultraviolet to infrared to terahertz bands), which is unmatched by any other material; the direct band gap of TMDCs is in the range of 1.0–2.5 eV, but the band gap structure can be adjusted by a variety of methods, such as changing the number of layers, inducing element defects, or forming van der Waals heterojunctions with other two-dimensional materials, thus allowing a larger operating wavelength range. In addition, the operating bandwidth of silicon photonic structures (such as silicon waveguides) also covers the frequency band of 1.12-2.5 μm. Therefore, the operating wavelengths of the two-dimensional material layer and the silicon photonic structure overlap in a large range, ensuring the ultra-large operating bandwidth of the on-chip photonic nonlinear activation function device based on the heterojunction of the two-dimensional material layer and the silicon photonic structure.

[0109] (3) Low power consumption application. The on-chip photonic nonlinear activation function device provided in this example uses a two-dimensional material as a back gate, thereby being able to perform more effective electrostatic control of the carrier density in the two-dimensional material, thereby reducing the voltage and excitation light power threshold required to operate the on-chip photonic nonlinear activation function device.

[0110] (4) Easy to integrate with CMOS process. The surface of two-dimensional materials is naturally passivated and has no dangling bonds, making them easy to integrate with photonic structures (such as silicon-based optical waveguides and silicon-based optical cavities). They can also construct vertical heterojunctions with other different two-dimensional materials, making them compatible with highly mature silicon optoelectronics platforms and CMOS integration processes without the conventional lattice mismatch problem.

[0111] In summary, the embodiment of the present invention utilizes the integration of two-dimensional materials and silicon photonic structures to realize highly reconfigurable complex photon activation function operations containing phase information. The on-chip photonic nonlinear activation function device achieves strong coupling between the silicon photonic structure and the two-dimensional material by designing a suitable silicon photonic structure and adjusting the energy band structure of the two-dimensional material, making it possible to adjust the Fermi level (optical absorption capacity) of the two-dimensional material and the refractive index (plasma dispersion effect) of the silicon photonic structure through the carrier effect, resulting in the heterojunction having the dual functions of a modulator and a detector in one. The design of the geometric structure of the silicon photonic structure also needs to consider the experimental conditions, such as selecting a suitable excitation light wavelength, which should be within the energy band of the photonic structure, and the intrinsic loss of the silicon photonic structure should be selected as low as possible. More importantly, by electrically controlling the carrier density in the heterojunction device formed by the two-dimensional material layer and the silicon photonic structure, more effective electrostatic control is performed on the electro-optical modulation efficiency and light response of the on-chip photonic nonlinear activation function device. This design scheme can greatly improve the reconfigurability of on-chip photonic nonlinear activation function devices, which is of great significance for the development of on-chip photonic nonlinear activation function devices with large bandwidth, fast response speed, low power consumption and high integration.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An on-chip photonic nonlinear activation function device, characterized in that: include: A substrate, an insulating layer, an n-type doped silicon photonic structure, a first electrode, an isolation layer, a second electrode, and a p-type doped two-dimensional material layer; The insulating layer is disposed on the substrate to isolate the substrate from the silicon photonic structure; the silicon photonic structure is disposed on the insulating layer; The first electrode is disposed on one side of the upper surface of the silicon photonic structure, and is used to provide a bias voltage to the silicon photonic structure; The isolation layer is arranged on the other side of the upper surface of the silicon photonic structure, and is used to isolate the silicon photonic structure from the second electrode; the second electrode is arranged on the isolation layer, and is used to provide a bias voltage to the two-dimensional material layer; the two-dimensional material layer is arranged on the isolation layer, the second electrode and the silicon photonic structure, and is in contact with the middle part of the silicon photonic structure, and the two-dimensional material layer is coupled with the silicon photonic structure to form a heterojunction device; Among them, based on the coupling effect between the two-dimensional material layer and the silicon photonic structure, the bias voltage provided by the first electrode and the second electrode to the heterojunction device is adjusted through a specific photocurrent detection feedback control mechanism to change the carrier concentration in the heterojunction device to adjust the Fermi level of the two-dimensional material layer and the refractive index of the silicon photonic structure, thereby realizing the function of modulating the input light signal and detecting and acquiring the nonlinear activation function.

2. The on-chip photonic nonlinear activation function device according to claim 1, characterized in that: The working principle of the on-chip photonic nonlinear activation function device specifically includes: When the bias voltage of the heterojunction device is a forward bias voltage, the Fermi level of the two-dimensional material layer becomes higher and the optical absorption capability becomes weaker, the width of the space charge region of the silicon photonic structure becomes narrower, the equivalent doping concentration increases, and the refractive index becomes smaller, thereby realizing the function of modulating the input optical signal; When the bias voltage of the heterojunction device is a reverse bias voltage, the Fermi level of the two-dimensional material layer becomes lower and the optical absorption capacity becomes stronger, the width of the space charge region of the silicon photonic structure becomes wider, the equivalent doping concentration decreases, and the refractive index becomes larger, thereby realizing the function of detecting the input light signal and obtaining the nonlinear activation function.

3. The on-chip photonic nonlinear activation function device according to claim 1, characterized in that: The silicon photonic structure comprises a first silicon photonic structure, a second silicon photonic structure and a third silicon photonic structure; The first portion of the silicon photonic structure is an n++-doped silicon waveguide, and is located on a first side of the silicon photonic structure; The second part of the silicon photonic structure is an undoped silicon waveguide, located at the second side of the silicon photonic structure; the third part of the silicon photonic structure is an n-doped special structure, located in the middle of the silicon photonic structure; The two-dimensional material layer is in contact with the third portion of the silicon photonic structure, and is not in contact with the first portion of the silicon photonic structure and is not in contact with the second portion of the silicon photonic structure.

4. The on-chip photonic nonlinear activation function device according to claim 3, characterized in that: The first electrode is disposed on the first portion of the silicon photonic structure, and a gap is provided between the first electrode and the two-dimensional material layer; The second electrode is disposed on the second portion of the silicon photonic structure and is not in direct contact with the second portion of the silicon photonic structure.

5. The on-chip photonic nonlinear activation function device according to any one of claims 1 to 4, characterized in that: The isolation layer includes an oxide layer, and the oxide layer includes aluminum oxide or chromium oxide.

6. The on-chip photonic nonlinear activation function device according to any one of claims 1 to 4, characterized in that: The silicon photonic structure includes at least one of the following: a microring resonator, a Magnetron interferometer, a two-dimensional photonic crystal, and a disk structure.

7. The on-chip photonic nonlinear activation function device according to any one of claims 1 to 4, characterized in that: The two-dimensional material layer is formed of a single layer or a few layers of one two-dimensional material, or is formed of a van der Waals heterojunction consisting of at least two single layers or a few layers of two-dimensional materials; The two-dimensional material includes at least one of the following: graphene, tungsten disulfide, tungsten diselenide, tungsten telluride, molybdenum disulfide, molybdenum diselenide and molybdenum ditelluride.

8. The on-chip photonic nonlinear activation function device according to any one of claims 1 to 4, characterized in that: The substrate is formed of single crystal silicon, the insulating layer is formed of silicon dioxide, and the thickness of the insulating layer is greater than or equal to 1 micrometer and less than or equal to 2 micrometers.

9. A photoelectric device, characterized in that: It comprises an on-chip photonic nonlinear activation function device as described in any one of claims 1 to 8.

10. A method for using an on-chip photonic nonlinear activation function device, characterized in that: Applied to the on-chip photonic nonlinear activation function device according to any one of claims 1 to 8, and introducing nonlinearity through a specific photocurrent detection feedback control mechanism, the method comprising: Step 1, constructing an integrated circuit capable of applying a bias voltage and measuring a photocurrent, and integrating the integrated circuit with the on-chip photonic nonlinear activation function device, wherein the integrated circuit is used to adjust the bias voltage of the on-chip photonic nonlinear activation function device based on a change in the photocurrent; Step 2, programming the transfer function between the bias voltage and the tuning voltage into an integrated circuit integrated with the on-chip photonic nonlinear activation function device; Step 3, generating an activation function by using a heterojunction device using the transfer function; Step 4, by scanning the photocurrent and transmittance of the heterojunction device under different voltages and light input powers, a relationship between transmittance and light input power is established, and a photon nonlinear activation function is obtained therefrom.

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