阅读说明：本技术 一种光学神经网络及芯片 (Optical neural network and chip ) 是由 徐哲 赵雅倩 李辰 葛沅 魏辉 于 2021-09-18 设计创作，主要内容包括：本发明提供一种光学神经网络和包括光学神经网络的芯片,光学神经网络包括：输入层,输入层包括激光器、多个耦合器和多个输入波导,激光器产生光学输入信号,多个输入波导通过耦合器接收不同波长的光学输入信号；前向波导网格,前向波导网格包括线性变换层和非线性激活层,线性变换层和非线性激活层接收输入层输入的光学输入信号,并对光学输入信号进行加权加法线性运算和非线性激活运算；以及输出层,输出层包括多个输出波导和多个光电探测器阵列,多个光电探测器阵列通过输出波导接收从前向波导网格传出的经过线性和非线性运算的光学输出信号。本发明可以实现片上集成波导中进行光学线性和非线性计算的功能。(The present invention provides an optical neural network and a chip including the same, the optical neural network including: an input layer including a laser generating an optical input signal, a plurality of couplers, and a plurality of input waveguides receiving the optical input signal of different wavelengths through the couplers; the forward waveguide grid comprises a linear conversion layer and a nonlinear activation layer, the linear conversion layer and the nonlinear activation layer receive optical input signals input by the input layer and perform weighted addition linear operation and nonlinear activation operation on the optical input signals; and an output layer including a plurality of output waveguides and a plurality of photodetector arrays receiving the linearly and non-linearly operated optical output signals from the grid of forward waveguides through the output waveguides. The invention can realize the function of optical linear and nonlinear calculation in the on-chip integrated waveguide.)

1. An optical neural network, comprising:

an input layer comprising a laser that generates an optical input signal, a plurality of couplers through which the plurality of input waveguides receive optical input signals of different wavelengths, and a plurality of input waveguides;

a forward waveguide grid including a linear transformation layer and a nonlinear activation layer, the linear transformation layer and the nonlinear activation layer receiving an optical input signal input by the input layer and performing weighted addition linear operation and nonlinear activation operation on the optical input signal; and

an output layer comprising a plurality of output waveguides and a plurality of photodetector arrays receiving optical output signals via the output waveguides that are subject to linear and nonlinear operations emanating from the lattice of forward waveguides.

2. The optical neural network of claim 1, wherein the linear transformation layer and the nonlinear activation layer of the forward waveguide grid are cascaded with optical logic gates and ring resonators.

3. The optical neural network of claim 2, wherein the optical logic gate comprises:

two second input waveguides and two second output waveguides;

the input end of the optical coupler is connected with the two second input waveguides, and the output end of the optical coupler is connected with the two second output waveguides; and

an optical phase shifter disposed on one of the two second output waveguides.

4. The optical neural network of claim 3, wherein the ring resonator comprises:

the waveguide comprises two straight waveguides and an annular waveguide, wherein the annular waveguide is arranged between the two straight waveguides;

a second optical phase shifter disposed on one of the two straight waveguides near an output; and

a third optical phase shifter disposed on the annular waveguide proximate the output perpendicular to the second optical phase shifter.

5. The optical neural network of claim 4, wherein the second output waveguide and the straight waveguide are provided with a phase change material layer on a side thereof near the output end.

6. A chip, comprising an optical neural network, the optical neural network comprising:

an input layer comprising a laser that generates an optical input signal, a plurality of couplers through which the plurality of input waveguides receive optical input signals of different wavelengths, and a plurality of input waveguides;

a forward waveguide grid including a linear transformation layer, a signal transmission layer, and a nonlinear active layer, the linear transformation layer and the nonlinear active layer receiving an optical input signal input by the input layer and performing weighted addition linear operation and nonlinear active operation on the optical input signal; and

an output layer comprising a plurality of output waveguides and a plurality of photodetector arrays receiving optical output signals via the output waveguides that are subject to linear and nonlinear operations emanating from the lattice of forward waveguides.

7. The chip of claim 6, wherein the linear transformation layer and the nonlinear activation layer of the forward waveguide grid are cascaded by an optical logic gate and a ring resonator.

8. The chip of claim 7, wherein the optical logic gate comprises:

two second input waveguides and two second output waveguides;

the input end of the optical coupler is connected with the two second input waveguides, and the output end of the optical coupler is connected with the two second output waveguides; and

an optical phase shifter disposed on one of the two second output waveguides.

9. The chip of claim 8, wherein the ring resonator comprises:

the waveguide comprises two straight waveguides and an annular waveguide, wherein the annular waveguide is arranged between the two straight waveguides;

a second optical phase shifter disposed on one of the two straight waveguides near an output; and

a third optical phase shifter disposed on the annular waveguide proximate the output perpendicular to the second optical phase shifter.

10. The chip of claim 9, wherein the second output waveguide and the straight waveguide are provided with a phase change material layer on a side close to the output end.

Technical Field

The present invention relates to the field of chips, and more particularly, to an optical neural network and a chip including the same.

Background

The innovation of artificial intelligence technology, especially artificial neural networks, has led to the revolution of many fields of applications, such as web search, computer recognition and recognition of languages and images. As one of the most important models of artificial intelligence, the artificial neural network can be used for simulating the capability of the biological neural network for processing information, and is widely applied to various scenes due to good generalization capability and robustness. However, electronic computers based on von neumann architecture and harvard architecture of silicon-based electronic chips have transmission bottleneck, power consumption increase, and computational bottleneck, and it has become increasingly difficult to meet the demands for computational power and power consumption in the big data era, so increasing the computational speed while reducing the computational power consumption is a critical problem faced by current optical computing technologies. In addition, the silicon-based electronic chip also has the problem of mutual interference of electronic signals and the problem of tide data, which greatly hinders the technical realization of an artificial neural network with high-density connection.

With the development and deepening of integrated optics, silicon photonics and nano material research, the on-chip optical neural network can organically combine the photoelectronic technology with a traditional neural network model, is expected to break through the technical bottlenecks of long time delay, high power consumption and the like of the traditional electronic neural network, and can also be used for constructing an optical processor. Photons are used for enabling artificial intelligence, and photons or light paths are used for replacing traditional electronic calculation to achieve artificial intelligence calculation with higher efficiency. On the other hand, with the development of advanced artificial neural networks, especially machine learning algorithms, the development of artificial neural networks also provides an efficient method for the design of nano-optical devices, further promotes the development of optical neural networks and nano-optics, and accelerates the design and optimization of optical devices.

Compared with the electronic neural network developed at present, the photonic neural network still has wide promotion space in aspects of trainability, integration level, scale, practicality and the like. On one hand, the nonideal and low stability of the performance of the photoelectronic device inhibit the trainable performance, integration level and scale of the photonic neural network, and more severe requirements are provided for constructing a neural network model with more complex functions; on the other hand, the application field of the photonic neural network is also limited by the all-optical nonlinear activation function, and the nonlinear operation is difficult to operate at a low intensity level.

Disclosure of Invention

In view of the above, an object of an embodiment of the present invention is to provide an optical neural network and a chip, in which a phase-change material is introduced, a nonlinear response of the phase-change material is amplified by using an on-chip waveguide structure, and a photo-thermal effect is reduced, so that a design of an on-chip integrated nonlinear active layer is completed, a purpose of performing nonlinear calculation in an on-chip integrated waveguide is achieved, problems of strong optical absorption and weak nonlinearity of the optical nonlinear material are solved, a biological neuron signal processing mode is simulated, a defect of photoelectric conversion inside the chip is avoided, and a possibility is provided for realizing a multilayer all-optical neural network.

In view of the above object, an aspect of the embodiments of the present invention provides an optical neural network, including: an input layer comprising a laser that generates an optical input signal, a plurality of couplers through which the plurality of input waveguides receive optical input signals of different wavelengths, and a plurality of input waveguides; a forward waveguide grid including a linear transformation layer and a nonlinear activation layer, the linear transformation layer and the nonlinear activation layer receiving an optical input signal input by the input layer and performing weighted addition linear operation and nonlinear activation operation on the optical input signal; and an output layer comprising a plurality of output waveguides and a plurality of photodetector arrays receiving optical output signals via the output waveguides that are both linearly and non-linearly operated upon from the lattice of forward waveguides.

In some embodiments, the linear transformation layer and the nonlinear activation layer of the forward waveguide grid are cascaded with an optical logic gate and a ring resonator.

In some embodiments, the optical logic gate comprises: two second input waveguides and two second output waveguides; the input end of the optical coupler is connected with the two second input waveguides, and the output end of the optical coupler is connected with the two second output waveguides; and an optical phase shifter disposed on one of the two second output waveguides.

In some embodiments, the ring resonator comprises: the waveguide comprises two straight waveguides and an annular waveguide, wherein the annular waveguide is arranged between the two straight waveguides; a second optical phase shifter disposed on one of the two straight waveguides near an output; and a third optical phase shifter disposed on the annular waveguide proximate the output end perpendicular to the second optical phase shifter.

In some embodiments, the second output waveguide and the side of the straight waveguide close to the output end are provided with a phase change material layer.

In another aspect of the embodiments of the present invention, there is provided a chip, where the chip includes an optical neural network, and the optical neural network includes: an input layer comprising a laser that generates an optical input signal, a plurality of couplers through which the plurality of input waveguides receive optical input signals of different wavelengths, and a plurality of input waveguides; a forward waveguide grid including a linear transformation layer and a nonlinear activation layer, the linear transformation layer and the nonlinear activation layer receiving an optical input signal input by the input layer and performing weighted addition linear operation and nonlinear activation operation on the optical input signal; and an output layer comprising a plurality of output waveguides and a plurality of photodetector arrays receiving optical output signals via the output waveguides that are both linearly and non-linearly operated upon from the lattice of forward waveguides.

In some embodiments, the linear transformation layer and the nonlinear activation layer of the forward waveguide grid are cascaded with an optical logic gate and a ring resonator.

In some embodiments, the optical logic gate comprises: two second input waveguides and two second output waveguides; the input end of the optical coupler is connected with the two second input waveguides, and the output end of the optical coupler is connected with the two second output waveguides; and an optical phase shifter disposed on one of the two second output waveguides.

In some embodiments, the ring resonator comprises: the waveguide comprises two straight waveguides and an annular waveguide, wherein the annular waveguide is arranged between the two straight waveguides; a second optical phase shifter disposed on one of the two straight waveguides near an output; and a third optical phase shifter disposed on the annular waveguide proximate the output end perpendicular to the second optical phase shifter.

In some embodiments, the second output waveguide and the side of the straight waveguide close to the output end are provided with a phase change material layer.

The invention has the following beneficial technical effects: by introducing the phase-change material, the nonlinear response of the phase-change material is amplified by utilizing the on-chip waveguide structure, the photo-thermal effect is reduced, the design of the on-chip integrated nonlinear activation layer is completed, the purpose of nonlinear calculation in the on-chip integrated waveguide is realized, the problems of strong optical absorption and weak nonlinearity of the optical nonlinear material are solved, the biological neuron signal processing mode is simulated, the defect of photoelectric conversion in a chip is avoided, and the possibility is provided for realizing the multilayer all-optical neural network.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained by using the drawings without creative efforts.

FIG. 1 is an overall schematic diagram of an optical neural network provided by the present invention;

FIG. 2 is a schematic diagram of an input layer of an optical neural network provided in the present invention;

FIG. 3 is a schematic diagram of an output layer of an optical neural network provided by the present invention;

FIG. 4 is a schematic diagram of an optical logic gate of the optical neural network provided in the present invention;

FIG. 5 is a schematic diagram of a ring resonator of an optical neural network provided in the present invention;

fig. 6 is a schematic diagram of a strip waveguide of an optical neural network provided by the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention are described in further detail with reference to the accompanying drawings.

It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are used for distinguishing two entities with the same name but different names or different parameters, and it should be noted that "first" and "second" are merely for convenience of description and should not be construed as limitations of the embodiments of the present invention, and they are not described in any more detail in the following embodiments.

In a first aspect of embodiments of the present invention, embodiments of an optical neural network are presented. Fig. 1 is an overall schematic diagram of an embodiment of the optical neural network provided by the present invention. As shown in fig. 1, an embodiment of the present invention includes:

an input layer comprising a laser that generates an optical input signal, a plurality of couplers through which the plurality of input waveguides receive optical input signals of different wavelengths, and a plurality of input waveguides;

a forward waveguide grid including a linear transformation layer and a nonlinear activation layer, the linear transformation layer and the nonlinear activation layer receiving an optical input signal input by the input layer and performing weighted addition linear operation and nonlinear activation operation on the optical input signal; and

an output layer comprising a plurality of output waveguides and a plurality of photodetector arrays receiving optical output signals via the output waveguides that are subject to linear and nonlinear operations emanating from the lattice of forward waveguides.

The embodiment of the invention comprises a tunable nano laser, optical weighting, optical addition, optical nonlinear activation and a nano photoelectric detector array on the same glass substrate. In the embodiment of the invention, the input light source is an on-chip integrated tunable nano laser, and the output wavelength of the on-chip integrated tunable nano laser is in an optical communication C wave band, particularly 1530 nm-1565 nm, because the C wave band shows the lowest optical loss, the on-chip integrated tunable nano laser is convenient to integrate and expand with an optical fiber system. The optical empowerment, the optical addition and the optical nonlinear activation comprise different nano-optical devices which are arranged and cascaded in different topological modes, perform transmission, linear and nonlinear operations, and control part of the tunable structure by computer software. The nano photoelectric detector is used as an output end and is used for detecting the optical signal of the output waveguide and extracting and processing the signal.

Suppose the laser input signal is x_iThe signal after optical weighting is w_ix_iTaking into account the linear offset w_ix_i+b_iThe signal after optical addition isAfter passing through the nonlinear activation function δ, the final signal isThe input layer is the laser input, the programmable forward waveguide grid is the optical weighting, optical addition and optical nonlinear activation, and the output layer is the detector output.

Fig. 2 is a schematic diagram of an input layer of the optical neural network provided by the present invention. As shown in fig. 2, the input layer includes: a tunable on-chip nano-laser, a plurality of nano-couplers, and a plurality of strip waveguides (i.e., input waveguides). The strip waveguide receives optical input signals of different wavelengths through the coupler, and the phase of the input optical signals can be adjusted and controlled according to the coupler.

Fig. 3 is a schematic diagram of an output layer of the optical neural network provided by the present invention. As shown in fig. 3, the output layer includes: a plurality of strip waveguides (namely output waveguides), a nano-photoelectric detector array and a computer software module. The present neural network can be viewed as N x M optical logic gates, where N is the input wave derivative and M is the output wave derivative, and optical calculations are performed inside the grid.

In some embodiments, the linear transformation layer and the nonlinear activation layer of the forward waveguide grid are cascaded with an optical logic gate and a ring resonator. The programmable forward waveguide grid includes: the optical fiber comprises a linear conversion layer (comprising an optical weighting module and an optical adding module), a signal transmission layer and a nonlinear activation layer. The embodiment of the invention at least comprises a linear conversion layer and a nonlinear activation layer, and analog operation is realized by an optical method. The programmable forward waveguide grid comprises two basic building blocks: the two structures can be cascaded in different topological modes, and a required neural network is built according to target requirements to realize different target operations.

In some embodiments, the optical logic gate comprises: two second input waveguides and two second output waveguides; the input end of the optical coupler is connected with the two second input waveguides, and the output end of the optical coupler is connected with the two second output waveguides; and an optical phase shifter disposed on one of the two second output waveguides.

Fig. 4 is a schematic diagram of an optical logic gate of the optical neural network provided by the present invention. As shown in fig. 4, the 2 x 2 optical logic gate includes: two second input waveguides (i.e., the input waveguides in the figure, to be separated from the input waveguides of the input layer), two second output waveguides (i.e., the output waveguides in the figure, to be separated from the output waveguides of the output layer), a split-ratio tunable optical coupler, and a programmable optical phase shifter. The optical phase shifter is arranged on the second output waveguide to realize power matching and relative phase delay, the optical coupler realizes direction control and beam splitting ratio adjustment of the optical path, and the two devices are controlled according to computer software programming.

In some embodiments, the ring resonator comprises: the waveguide comprises two straight waveguides and an annular waveguide, wherein the annular waveguide is arranged between the two straight waveguides; a second optical phase shifter disposed on one of the two straight waveguides near an output; and a third optical phase shifter disposed on the annular waveguide proximate the output end perpendicular to the second optical phase shifter.

Fig. 5 is a schematic diagram of a ring resonator of the optical neural network provided by the present invention. As shown in fig. 5, the ring resonator includes: two straight waveguides, a ring waveguide, two programmable optical phase shifters. The optical phase shifters are respectively arranged on the straight waveguide and the annular waveguide to realize power matching and relative phase delay. And the second optical phase shifter is arranged on one of the two straight waveguides close to the output end, and the third optical phase shifter is arranged on the annular waveguide close to the output end and perpendicular to the second optical phase shifter.

The optical phase shifter, the second optical phase shifter and the third optical phase shifter can be programmable nano acousto-optic modulators, and acoustic signals are loaded onto the strip waveguide by utilizing the transduction effect of the piezoelectric ceramics, so that optical modulation is realized. The acousto-optic modulator can be used in the field of ultrafast optical signal processing, and avoids the defects caused by adopting other modulation modes, such as low conversion efficiency, slow response, complex electrothermal modulation device, large energy dissipation and heat accumulation effect.

In the embodiment of the present invention, each of the optical logic gate and the ring resonator structure includes two input terminals and two output terminals, wherein any one of the output terminals can be connected to the upper input terminal or the lower input terminal of the next optical logic gate or the upper input terminal or the lower input terminal of the ring resonator. Waveguide grids after cascading are mainly divided into two main categories: unidirectional networks and circular networks.

In some embodiments, the second output waveguide and the side of the straight waveguide close to the output end are provided with a phase change material layer.

Fig. 6 is a schematic diagram of a strip waveguide of an optical neural network provided by the present invention. As shown in fig. 6, the strip waveguide in the embodiment of the present invention includes: silicon stripe waveguide and Sb₂S₃An overlying silicon strip waveguide. Silicon strip waveguide as light conducting and heat sink device, Sb₂S₃The covered strip waveguide acts as a nonlinear operation device. Sb₂S₃Is a wide band gap phase change material and is therefore optically transparent over the optical communications band, maintaining an almost uniform change in refractive index between its amorphous and crystalline states. The strip waveguide is arranged on a glass substrate, has a thickness of 220nm, is compatible with standard CMOS technology and has a width of 500 nm. Sb₂S₃The thickness of the optical waveguide is 20 nm-50 nm, the width of the optical waveguide is consistent with that of the strip waveguide, the conversion between a crystalline state and an amorphous state is realized through programmable pump laser, computer software mainly controls the light intensity and polarization of pump light, and the pump light is usually 800nm ultrafast laser. Sb₂S₃The silicon strip waveguide is arranged on the silicon and used as a radiator, so that the Joule heat can be diffused quickly, and unstable state transition is prevented. Specifically, when the pump light power is lower than the threshold power, the phase-change material is in a crystal state, and a large amount of signal light is absorbed; when the pump light power is higher than the threshold power, the phase change material is in an amorphous state and a large amount of signal light can pass through. The "summation" and "weighting" of the neural network itself depends on the silicon strip waveguide and Sb₂S₃And the phase change material is arranged on one side of the output waveguide of the optical logic gate and the ring resonant cavity to realize the function of the nonlinear activation function of the optical neural network.

The embodiment of the invention does not need conversion between electro-optic and photoelectric, and avoids the influence of thermal effect. The device collects the input multi-path optical signals through programmable forwardThe waveguide grid structure performs a weighted additive linear operation, via Sb₂S₃The phase change material performs a nonlinear activation operation and finally detects an output signal by an optical detector.

In order to solve the problem of low efficiency of the current photonic neural network, silicon is used as an integrated optical device substrate, so that on one hand, the existing integrated circuit process can be used for manufacturing an optical device, and the cost is reduced; on the other hand, the silicon material has small light absorption to the communication waveband, which is beneficial to reducing the device loss, and the refractive index difference between the silicon and the silicon dioxide material is large, thereby enhancing the limitation of the optical device to the optical field, being beneficial to reducing the size of the silicon-based optical integrated device, and further improving the integration density of the chip. The adopted MZI and the ring resonant cavity both belong to the basic structure of the nano-optics field, and are convenient to process and manufacture and convenient to cascade, thereby reducing the manufacturing complexity and the future system cost. The invention introduces Sb₂S₃The nonlinear material utilizes the on-chip waveguide structure to amplify the nonlinear response of the phase change material and reduce the photo-thermal effect, thereby completing the design of the on-chip integrated nonlinear activation layer and realizing the purpose of nonlinear calculation in the on-chip integrated waveguide. The invention adopts the all-optical nano optical device, has programmability, small structure size and high operation speed, is convenient for system upgrade and realizes various complex mathematical operations.

In view of the above object, a second aspect of the embodiments of the present invention provides a chip, where the chip includes an optical neural network, and the optical neural network includes: an input layer comprising a laser that generates an optical input signal, a plurality of couplers through which the plurality of input waveguides receive optical input signals of different wavelengths, and a plurality of input waveguides; a forward waveguide grid including a linear transformation layer and a nonlinear activation layer, the linear transformation layer and the nonlinear activation layer receiving an optical input signal input by the input layer and performing weighted addition linear operation and nonlinear activation operation on the optical input signal; and an output layer comprising a plurality of output waveguides and a plurality of photodetector arrays receiving optical output signals via the output waveguides that are both linearly and non-linearly operated upon from the lattice of forward waveguides.

It should be understood by those skilled in the art that the technical features and technical effects of the optical neural network described above are applicable to a chip, and are not described herein again for brevity of the description.

The foregoing is an exemplary embodiment of the present disclosure, but it should be noted that various changes and modifications could be made herein without departing from the scope of the present disclosure as defined by the appended claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. Furthermore, although elements of the disclosed embodiments of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

It should be understood that, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly supports the exception. It should also be understood that "and/or" as used herein is meant to include any and all possible combinations of one or more of the associated listed items.

The numbers of the embodiments disclosed in the embodiments of the present invention are merely for description, and do not represent the merits of the embodiments.

Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, of embodiments of the invention is limited to these examples; within the idea of an embodiment of the invention, also technical features in the above embodiment or in different embodiments may be combined and there are many other variations of the different aspects of the embodiments of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of the embodiments of the present invention are intended to be included within the scope of the embodiments of the present invention.