Optical computing array based on germanium modulator

Abstract

The invention belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to an optical computing array based on germanium modulators, which comprises a cross matrix formed by crossing multiple rows of parallel input optical waveguides and multiple columns of parallel output optical waveguides. A photoelectric detector is arranged at the output end of each row of output optical waveguides; a plurality of optical splitters; each germanium modulator corresponds to one crossed waveguide, and the first input end of each germanium modulator is connected with the output end of the optical splitter through a transmission optical waveguide; each light combiner is connected with the output end of the germanium modulator and the output optical waveguide, through the above structure, the computing array which has a thermal compensation mechanism, can reduce light reflection and is high in responsivity is comprehensively provided, and therefore under the condition that frequent switching is met, the computing array has the advantages that the computing efficiency is improved, and the computing efficiency is improved. And a low-power-consumption large-scale integrated calculation array scheme is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor optoelectronic devices, and in particular relates to an optical computing array based on a germanium modulator. Background Art

[0002] As a new generation of high-performance computing architecture, optical computing technology has shown great potential in the fields of artificial intelligence and signal processing due to its high parallelism and low latency. Its core performance indicators mainly depend on the total computing bandwidth, power consumption and system stability. As the computing scale expands, the amount of data processed by the system per unit time increases linearly, but the power consumption of the optical chip weight unit in the optoelectronic fusion system increases at a square level, resulting in a sharp increase in overall power consumption. This contradiction has become a key bottleneck restricting the practical application of optical computing chips.

[0003] Among the current mainstream technical solutions, the optical computing architecture based on phase change materials (PCM) (such as the existing technology CN111684343B) realizes weight modulation through the reversible transformation of the material's crystalline and amorphous states. Although this solution has extremely low static power consumption (up to μW level) and large-scale matrix integration capabilities, its phase change process has a heat accumulation effect, and the material response speed is limited (usually in the hundreds of nanoseconds), which makes it difficult to meet the millisecond-level frequent switching requirements of weight parameters in deep learning training scenarios. In addition, frequent switching will significantly increase dynamic power consumption (up to mW / unit level), resulting in reduced system energy efficiency.

[0004] Another type of optical computing scheme based on carrier absorption effect (such as the prior application CN116736933A proposed by the applicant) realizes optical modulation by regulating the free carrier concentration under forward bias. Such devices have nanosecond response speed and can support training-level weight update frequency, but their forward conduction current is large (typical value >100 μA / unit), and the total power consumption increases significantly when building large-scale arrays (typical power consumption >10 mW / unit), making it difficult to meet the energy efficiency requirements of highly integrated systems. In addition, long-term high-current operation may cause device reliability issues.

[0005] In view of the above technical defects, there is an urgent need for an optical computing chip solution that takes into account low operating power consumption, high switching tolerance and large-scale integration capabilities. Summary of the invention

[0006] The object of the present invention is to provide an optical computing array based on germanium modulators to partially alleviate or solve the above-mentioned shortcomings and reduce the power consumption of large-scale optical computing chips.

[0007] In order to solve the above-mentioned technical problems, the present invention specifically adopts the following technical solutions: An optical computing array based on germanium modulators, comprising: A cross matrix, wherein the cross matrix is ​​formed by crossing a plurality of rows of mutually parallel input optical waveguides and a plurality of columns of mutually parallel output optical waveguides; and a photodetector is provided at the output end of each column of the output optical waveguide; A plurality of optical splitters, wherein the optical splitters are arranged at the front end of a cross waveguide formed by each row of input optical waveguides and each column of output optical waveguides; A plurality of germanium modulators, each of which corresponds to one of the cross waveguides, and a first input end of the germanium modulator is connected to an output end of the optical splitter through a transmission optical waveguide; A plurality of optical combiners, each of which is connected to the output end of the germanium modulator and the output optical waveguide, and is used to combine the first optical signal of the corresponding cross waveguide and the second optical signal output by the germanium modulator into a third optical signal, and transmit the third optical signal to the next cross waveguide on the same output optical waveguide; Among them, the photoelectric characteristics of the light absorption layer in the germanium modulator can be changed by writing a control signal into its second input terminal, and the germanium modulator can generate a second light signal based on the first light signal input into the first input terminal and send it to the light combiner; the photoelectric characteristics include a light absorption coefficient.

[0008] As an improvement, the germanium modulator comprises: a silicon substrate and an insulating layer deposited on the silicon substrate; a waveguide layer is arranged on the insulating layer; a germanium absorption layer is embedded in the waveguide layer; a first depth of the germanium absorption layer embedded in the waveguide layer is less than the thickness of the waveguide layer, or a second depth of the germanium absorption layer embedded in the waveguide layer is equal to the thickness of the waveguide layer; A heating unit is disposed on the top and / or bottom of the germanium absorption layer, and the heating unit extends along the length direction of the germanium absorption layer; or, Heating units are respectively arranged on both sides of the germanium absorption layer, and the heating units extend along the length direction of the germanium absorption layer; or, Heating unit groups are respectively arranged on both sides of the germanium absorption layer, and the heating unit group on each side includes a plurality of heating units evenly spaced along the length direction of the germanium absorption layer, wherein the heating levels of two adjacent heating units on the same side are primary heating and secondary heating respectively; The heating unit is used to change the photoelectric properties of the light absorbing layer.

[0009] As an improvement, the germanium absorption layer includes a light guiding region and a light absorption region sequentially arranged along the light propagation direction. The cross-sectional area of ​​the light guiding region gradually increases from the incident end in a direction close to the light absorbing region; and the cross-sectional area of ​​the light absorbing region is the same along the light propagation direction.

[0010] As an improvement, when the light guiding area is viewed from above, its width gradually increases along the light propagation direction from the incident end; and when the light guiding area is viewed from the side, its width gradually decreases from top to bottom; or, the interface between the light guiding area and the waveguide layer is fan-shaped; and / or, the cross-section of the light absorption area is rectangular.

[0011] As an improvement, the width and length of the heating unit located at the top and / or bottom of the germanium absorption layer are both smaller than the width and length of the germanium absorption layer.

[0012] An optical computing array based on germanium modulators, comprising: A cross matrix, wherein the cross matrix is ​​formed by crossing a plurality of rows of mutually parallel input optical waveguides and a plurality of columns of mutually parallel electrical buses; A plurality of optical splitters, the optical splitters being arranged at the front end of the intersection node between each row of optical input waveguides and each column of electrical bus; A plurality of germanium modulators, each of which corresponds to one of the cross nodes, and a first input end of the germanium modulator is connected to an output end of the optical splitter through a transmission optical waveguide; A plurality of first photodetectors, each of which is connected to the output end of the germanium modulator and the electrical bus, and is used to convert the optical signal output by the germanium modulator into an electrical signal and send it to the electrical bus; The photoelectric characteristics of the light absorption layer in the germanium modulator can be changed by writing a control signal into its second input terminal, and the germanium modulator can generate a second light signal based on the first light signal inputted from the first input terminal and send it to the first photodetector; the photoelectric characteristics include a light absorption coefficient; Therein, the product of the multiplier value and the multiplicand value is encoded in the optical signal.

[0013] As an improvement, the germanium modulator comprises: a silicon substrate and an insulating layer deposited on the silicon substrate; a waveguide layer is arranged on the insulating layer; a germanium absorption layer is embedded in the waveguide layer; a first depth of the germanium absorption layer embedded in the waveguide layer is less than the thickness of the waveguide layer, or a second depth of the germanium absorption layer embedded in the waveguide layer is equal to the thickness of the waveguide layer; A heating unit is disposed on the top and / or bottom of the germanium absorption layer, and the heating unit extends along the length direction of the germanium absorption layer; or, Heating units are respectively arranged on both sides of the germanium absorption layer, and the heating units extend along the length direction of the germanium absorption layer; or, Heating unit groups are respectively arranged on both sides of the germanium absorption layer, and the heating unit group on each side includes a plurality of heating units evenly spaced along the length direction of the germanium absorption layer, wherein the heating levels of two adjacent heating units on the same side are primary heating and secondary heating, respectively.

[0014] As an improvement, the germanium absorption layer includes a light guiding region and a light absorption region sequentially arranged along the light propagation direction. The cross-sectional area of ​​the light guiding region gradually increases from the incident end in a direction close to the light absorbing region; and the cross-sectional area of ​​the light absorbing region is the same along the light propagation direction.

[0015] As an improvement, when the light guiding area is viewed from above, its width gradually increases along the light propagation direction from the incident end; and when the light guiding area is viewed from the side, its width gradually decreases from top to bottom; or, the interface between the light guiding area and the waveguide layer is fan-shaped; and / or, the cross-section of the light absorption area is rectangular.

[0016] As an improvement, the width and length of the heating unit located at the top and / or bottom of the germanium absorption layer are smaller than the width and length of the germanium absorption layer. The principle and beneficial technical effects of the present invention are: In response to the millisecond-level frequent switching requirements in deep learning training scenarios, the present application provides a high-responsive computing array with a thermal compensation mechanism that can reduce light reflection, so as to achieve the design of a low-power large-scale integrated computing array while meeting the conditions of frequent switching.

[0017] In contrast to the existing methods of using phase change materials for modulation, or changing the carrier concentration by injecting current or applying voltage in the doping to change the light absorption coefficient, the present application provides an optical computing array based on a reverse biased germanium modulator, while also performing multiple controls on the light absorption characteristics of the germanium absorption layer.

[0018] First, the present application regulates the photoresponsivity of the germanium modulator by voltage. The dark current of the germanium modulator under reverse bias is extremely low, and its photocurrent during operation can be at least 2 orders of magnitude smaller than that of the forward-conducting carrier absorption modulator or phase change material modulator, thereby effectively reducing the power consumption of a single device during operation.

[0019] Furthermore, a heating unit is provided on at least one side of the germanium absorption layer, and a real-time feedback mechanism is provided to ensure the consistency and uniformity of the temperature of the entire germanium absorption layer, thereby increasing the electrons in the valence band that can be transferred, thereby changing the light absorption coefficient of the germanium absorption layer and reducing the operating voltage of the electro-absorption modulator. In addition, when abnormalities such as signal distortion caused by temperature (for example, the system power consumption is large, resulting in a high system temperature, or the temperature is high during the modulation process of the heating unit) are detected, the heating unit located inside the optical computing array can also be used for temperature compensation, without the need to separately set up other temperature compensation modules outside the optical computing array; that is, by setting up a dual-purpose heating unit, the light absorption coefficient of the absorption layer can be changed, and temperature compensation can also be performed to alleviate signal distortion.

[0020] Furthermore, in the case where the light absorption cross-sectional area of ​​the light absorption region (germanium absorption layer) is large (for example, "full etching"), the present application performs a partitioned design on the germanium absorption layer (light guiding region and light absorption region), and guides the light signal transmitted from the optical waveguide through a gradient interface formed by gradually changing the height and width of the light guiding region, that is, the cross-sectional area of ​​the light guiding region gradually increases from the incident end in terms of height and length, which can greatly reduce the reflection at the incident end when the light propagates in the light absorption layer (germanium absorption layer) with a larger cross-sectional area, thereby improving the light absorption rate of the modulator. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without paying creative labor.

[0021] Figure 1 is an exemplary side view of a modulator in Embodiment 2 of the present invention; Figure 2 is another exemplary side view of the modulator in the second embodiment of the present invention; Figure 3 is another exemplary side view of the modulator in the second embodiment of the present invention; Figure 4 is a top view of a modulator in Embodiment 2 of the present invention; Figure 5 It is a front view of the germanium absorption layer in the second embodiment of the present invention; Figure 6 is a top view of the germanium absorption layer in the second embodiment of the present invention; Figure 7 is a schematic diagram of the structure of an exemplary optical computing array in Embodiment 1 of the present invention; Figure 8 FIG. 4 is a schematic diagram of the structure of another exemplary optical computing array in Embodiment 1 of the present invention.

[0022] Markings in the figure: 1. Silicon substrate; 2. Waveguide layer; 3. Heating unit; 4. Insulating layer; 5. Germanium absorption layer; 51. Light guiding region; 52. Light absorption region; 6. Electrode; 7. Silicon ribbon; 8. Optical computing unit; 101. Germanium modulator; 102. Input optical waveguide; 103. Transmission optical waveguide; 104. Output optical waveguide; 105. Electrical bus; 106. First photodetector. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments 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 making creative work are within the scope of protection of the present invention.

[0024] Herein, the suffixes such as "module", "component" or "unit" used to represent elements are used only to facilitate the description of the present invention and have no specific meaning in themselves. Therefore, "module", "component" or "unit" can be used in a mixed manner. Herein, the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front", "back", "one end", "the other end", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0025] In this document, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In this document, "plurality" means two or more, that is, it includes two, three, four, five, etc.

[0026] In this article, the "optical splitter" can use optical waveguides, optical couplers, heaters, phase shifters and other components with specific structures to achieve the distribution of optical signals inside the chip in an active or passive manner. Correspondingly, the "optical combiner" can use optical waveguides, optical couplers, heaters, phase shifters and other components with specific structures to achieve the summation of optical signals inside the chip in an active or passive manner.

[0027] Embodiment 1 The present invention provides an optical computing array based on a germanium modulator, comprising: A cross matrix is ​​formed by a plurality of rows of mutually parallel input channels and a plurality of columns of mutually parallel output channels, and a photoelectric detector is arranged at the output end of each column of the output optical waveguide.

[0028] A plurality of optical splitters are arranged at the front end of the cross channel formed by each row of optical input channels and each column of output channels.

[0029] A plurality of signal processing units, each of which corresponds to one of the cross channels, and a first input end of the signal processing unit is connected to an output end of the optical splitter through a transmission optical waveguide; the transmission optical waveguide can be made of one of the following optical waveguide materials: silicon (Si), silicon oxide (SiO 2 ), silicon nitride (SiN), indium phosphide (InP), gallium phosphide (GaP), germanium (Ge), lithium niobate (LiNbO 3 ), aluminum nitride (AlN), or any Group IV or III-V semiconductor with a band gap higher than the wavelength of light.

[0030] The signal processing unit is a germanium modulator, or the signal processing unit includes a germanium modulator and a photodetector.

[0031] A plurality of light combiners, each of which is connected to the output end of the signal processing unit and the output channel, and is used to combine the first signal of the corresponding cross channel and the second signal output by the signal processing unit into a third signal, and transmit it to the next cross channel on the same output channel.

[0032] Compared with the existing method of using phase change materials for modulation, or changing the carrier concentration by injecting current or applying voltage in the doping to change the light absorption coefficient. This application proposes a solution that is completely different from the prior art in order to meet the needs of frequent switching in milliseconds in deep learning training scenarios. This application provides an optical computing array based on a reverse-biased germanium modulator. The light responsiveness of the germanium modulator is regulated by voltage. The dark current of the germanium modulator under reverse bias is extremely low. The photocurrent during operation can be at least 2 orders of magnitude smaller than that of a forward-conducting carrier absorption modulator or a phase change material modulator, thereby effectively reducing the power consumption of a single device during operation.

[0033] In some embodiments, the input channel is an input optical waveguide, the output channel is an output optical waveguide, and accordingly, the signal processing unit is a germanium modulator.

[0034] Specifically, the optical computing array includes: A cross matrix, wherein the cross matrix is ​​formed by crossing multiple rows of mutually parallel input optical waveguides and multiple columns of mutually parallel output optical waveguides; and a photodetector is provided at the output end of each column of the output optical waveguide; preferably, the input optical waveguide and the output optical waveguide are arranged vertically.

[0035] A plurality of optical splitters are arranged at the front end of a cross waveguide formed by each row of input optical waveguides and each column of output optical waveguides; preferably, the optical splitter is arranged at the front end of the input optical waveguide in the cross waveguide.

[0036] A plurality of germanium modulators, each of which corresponds to one of the cross waveguides, and a first input end of the germanium modulator is connected to an output end of the optical splitter through a transmission optical waveguide; A plurality of optical combiners, each of which is connected to the output end of the germanium modulator and the output optical waveguide, and is used to combine the first optical signal of the corresponding cross waveguide and the second optical signal output by the germanium modulator into a third optical signal, and transmit the third optical signal to the next cross waveguide on the same output optical waveguide; Among them, the photoelectric characteristics of the light absorption layer in the germanium modulator can be changed by writing a control signal into its second input terminal, and the germanium modulator can generate a second light signal based on the first light signal input into the first input terminal and send it to the light combiner; the photoelectric characteristics include a light absorption coefficient.

[0037] That is, multiple rows of input optical waveguides and multiple rows of output optical waveguides are cross-arranged to divide the optical computing array into multiple optical computing units, and the optical computing units include cross-waveguides, and splitters, germanium modulators and combiners arranged at different positions of the cross-waveguides.

[0038] In other embodiments, the input channel is an input optical waveguide, the output channel is an electrical bus, and accordingly, the signal processing unit is a germanium modulator and a photodetector (ie, the first photodetector hereinafter).

[0039] Specifically, a cross matrix is ​​formed by crossing a plurality of rows of mutually parallel input optical waveguides and a plurality of columns of mutually parallel electrical buses; preferably, the input optical waveguide is perpendicular to the electrical bus.

[0040] A plurality of optical splitters are arranged at the front end of the intersection node between each row of optical input waveguide and each column of electrical bus; preferably, the optical splitter is arranged at the front end of the input optical waveguide in the intersection waveguide.

[0041] A plurality of germanium modulators, each of which corresponds to one of the cross nodes, and a first input end of the germanium modulator is connected to an output end of the optical splitter through a transmission optical waveguide; A plurality of first photodetectors, each of which is connected to the output end of the germanium modulator and the electrical bus, and is used to convert the optical signal output by the germanium modulator into an electrical signal and send it to the electrical bus; The photoelectric characteristics of the light absorption layer in the germanium modulator can be changed by writing a control signal into its second input terminal, and the germanium modulator can generate a second light signal based on the first light signal inputted from the first input terminal and send it to the first photodetector; the photoelectric characteristics include a light absorption coefficient; Therein, the product of the multiplier value and the multiplicand value is encoded in the optical signal.

[0042] That is, multiple rows of input optical waveguides and multiple rows of electrical buses are cross-arranged to divide the optical computing array into multiple optical computing units, and the optical computing units include cross-waveguides, and splitters, germanium modulators, first photodetectors and light combiners arranged at different positions of the cross-waveguides.

[0043] Embodiment 2 This embodiment provides a germanium modulator, which is applied to the optical computing array in the first embodiment, including a silicon substrate 1 and an insulating layer 4 deposited on the silicon substrate 1; a waveguide layer 2 is provided on the insulating layer 4; a germanium absorption layer 5 is embedded on the waveguide layer 2; a first depth of the germanium absorption layer 5 embedded in the waveguide layer 2 is less than the thickness of the waveguide layer 2, or a second depth of the germanium absorption layer 5 embedded in the waveguide layer 2 is greater than or equal to the thickness of the waveguide layer 2 (preferably, the second depth of the germanium absorption layer 5 embedded in the waveguide layer 2 is equal to the thickness of the waveguide layer 2, which is "full etching").

[0044] When the second depth is equal to the thickness of the waveguide layer 2 , it indicates that the bottom of the germanium absorption layer 5 is flush with the upper surface of the insulating layer 4 ; when the second depth is greater than the thickness of the waveguide layer 2 , it indicates that the germanium absorption layer 5 is embedded in the insulating layer 4 .

[0045] In the above embodiment, when the second depth is equal to the thickness of the waveguide layer 2, that is, the insulating layer 4 is used as the etching end point, on the one hand, the germanium absorption layer 5 can have a larger cross-section, so that the overlap time with the light field in the modulation area is the longest. At the same length, the responsiveness is higher; at the same responsiveness, the size is smallest. On the other hand, the etching depth is easy to control, and the consistency of the etched groove depth between different modulators can be ensured. In the traditional shallow etching process, since the etching depth is shallow and difficult to accurately control, it is easily affected by factors such as uneven silicon layer thickness, resulting in inconsistent etching depth, which in turn affects the performance uniformity of the modulator. The etching groove process that reaches the insulating layer 4 has better process stability, which is conducive to the large-scale production of high-quality modulators.

[0046] In some embodiments, a heating unit 3 is disposed on at least one side of the germanium absorption layer 5 .

[0047] In some specific embodiments, a heating unit 3 is provided on the top and / or bottom of the germanium absorption layer 5, and the heating unit 3 extends along the length direction of the germanium absorption layer 5; or, heating units 3 are respectively provided on both sides of the germanium absorption layer 5, and the heating units 3 extend along the length direction of the germanium absorption layer 5; or, heating unit 3 groups are respectively provided on both sides of the germanium absorption layer 5, and the heating unit 3 group on each side includes a plurality of heating units 3 evenly spaced along the length direction of the germanium absorption layer 5, wherein the heating levels of two adjacent heating units 3 located on the same side are primary heating and secondary heating, respectively; the heating unit 3 is used to change the photoelectric properties of the light absorption layer.

[0048] Completely different from the traditional idea of ​​relying on high electric field intensity to improve the absorption coefficient and thus ensure the uniformity of the photocurrent density, the present invention provides a thermal compensation mechanism that only targets the end point effect. Specifically, by arranging a heating unit 3 on at least one side (bottom and / or top, or front and back sides) of the germanium absorption layer 5, the heating unit 3 acts on the germanium absorption layer 5 along the length direction of the germanium absorption layer to ensure the consistency and uniformity of the temperature of the entire germanium absorption layer 5, thereby increasing the number of electrons that can transition to the valence band, thereby changing the light absorption coefficient of the germanium absorption layer 5 and reducing the operating voltage of the electro-absorption modulator. In this process, it is only necessary to ensure the final light absorption rate (that is, the ratio of input light to output light / input light), without considering the uniformity of the light absorption coefficient of the germanium absorption layer 5.

[0049] That is to say, the present application provides a thermal compensation mechanism for dual regulation of the light absorption coefficient only for the endpoint effect. First, the light absorption coefficient of the germanium absorption layer is adjusted from the germanium modulator itself by heating the germanium absorption layer, and then the light absorption coefficient of the germanium absorption layer is further adjusted by adjusting the input voltage. In other words, this process does not require high adjustment of the input voltage, that is, while ensuring low energy consumption, the response speed of the computing array can also be guaranteed, thereby being able to meet the requirements of large-scale matrices.

[0050] In some embodiments, the germanium modulator further comprises: The temperature monitoring module is used to monitor the actual temperature value of the germanium absorption layer 5 in real time.

[0051] A first judgment module is used to judge whether the actual temperature value monitored by the temperature monitoring module is greater than a first preset temperature threshold value, and if the actual temperature value is greater than the first preset temperature threshold value, a first control signal indicating stopping heating is generated and sent to the heating unit 3 / the heating unit group; if the actual temperature value is less than the first preset temperature threshold value, a second control signal indicating continuing monitoring is generated and sent to the temperature monitoring module; and / or, The temperature monitoring module is used to monitor in real time the actual temperature value of the germanium absorption layer 5 after being heated by the heating unit 3 which is in the first-level heating state.

[0052] The second judgment module is used to judge whether the actual temperature value monitored by the temperature monitoring module reaches the preset target temperature threshold after a preset period of time. If not, a third control signal is generated and sent to indicate that the heating unit 3 with the secondary heating level started and in a dormant state is started, so that the actual temperature of the germanium absorption layer 5 reaches the preset target temperature threshold.

[0053] Among them, the first temperature threshold can be obtained in advance through a large number of experiments, or can be pre-set by the user based on experience. When the actual temperature is near the first preset temperature threshold, the number of valence band electrons that can transition tends to be maximized, but at the same time it will not cause too much adverse effects on the material itself.

[0054] The division of heating levels (primary and secondary) is only for distinguishing the two and cannot limit the heating power or other characteristics. When only the primary heating is turned on, the heating power is small, and when the primary heating and the secondary heating are turned on at the same time, the heating power increases, and the temperature of the germanium absorption layer 5 can also be increased accordingly.

[0055] The present invention regulates the temperature of the germanium absorption layer 5 through a real-time feedback mechanism. On the one hand, it can maximize the number of valence band electrons that can transition as much as possible. On the other hand, it can improve the temperature stability of the germanium absorption layer 5 and prevent the problem of unstable light signals emitted by the germanium absorption layer 5 due to frequent changes in the temperature of the germanium absorption layer 5.

[0056] In some embodiments, the germanium absorption layer includes a light guiding zone and a light absorption zone arranged in sequence along the light propagation direction, wherein the cross-sectional area of ​​the light guiding zone gradually increases from the incident end in the direction close to the light absorption zone; and the cross-sectional area of ​​the light absorption zone is the same along the light propagation direction.

[0057] In some specific embodiments, the longitudinal section of the light guiding area 51 is a right-angled trapezoid, and the hypotenuse of the right-angled trapezoid corresponds to the interface between the light guiding area 51 and the waveguide layer 2, and the angle α between the hypotenuse and the bottom side is 86°-89°; the longitudinal section of the light absorption area 52 is rectangular; or, the interface between the light guiding area 51 and the waveguide layer 2 is fan-shaped. The longitudinal section refers to a vertical plane parallel to the length direction of the germanium absorption layer.

[0058] When the light guiding area is viewed from above, its width gradually increases from the incident end along the direction of light propagation; and when the light guiding area is viewed from the side, its width gradually decreases from top to bottom; or, the interface between the light guiding area and the waveguide layer is fan-shaped; and / or, the cross-section of the light absorption area is rectangular.

[0059] The purpose of the above arrangement is to achieve a smooth transition of the refractive index, because the refractive index of silicon is about 3.4 and the refractive index of germanium is about 4.4. Through this gradual structural change, the refractive index can be gradually transitioned from the waveguide layer 2 (silicon waveguide) to germanium, reducing the reflection of light at the incident end. When light propagates at the interface of media with different refractive indices, the greater the difference in refractive index, the more severe the reflection. This gradual transition structure allows light to enter the germanium absorption layer 5 more smoothly from the silicon waveguide, improves the coupling efficiency of light, and thus improves the light absorption capacity of the modulator.

[0060] Ideally, the light guiding area is a cone with a small front and a large back. The cone-shaped structure can achieve a more perfect refractive index gradient, minimize reflection of light when entering the germanium absorption layer 5, and theoretically maximize the light coupling efficiency.

[0061] Due to process limitations, a conical light guiding area requires high costs. Therefore, in order to reduce the process difficulty in this embodiment, it is only necessary to gradually increase the cross-sectional area of ​​the light guiding area from the incident end in the direction close to the light absorption area 52. For example, the light guiding area is a triangle with a narrow front and a wide back when viewed from above; and a trapezoid with a large top and a small bottom when viewed from the front. Although it is different from the ideal cone shape, the trapezoidal structure can still achieve a gradual change in the refractive index to a certain extent and reduce light reflection. It is a feasible solution under existing process conditions.

[0062] That is to say, the present invention restricts the shape of the light guiding zone so that the cross-sectional area of ​​the light guiding zone gradually increases from the incident end in terms of height and length, thereby greatly reducing the reflection of light at the incident end when propagating in the light absorption layer (germanium absorption layer) with a larger cross-sectional area, thereby improving the light absorption rate of the modulator. In other words, the present application provides a full etching solution with a thermal compensation mechanism that can reduce light reflection.

[0063] In some embodiments, the width and length of the heating unit 3 located at the top and / or bottom of the germanium absorption layer 5 are both smaller than the width and length of the germanium absorption layer 5. In this way, while ensuring the heating effect, unnecessary heat waste will not be caused. In this embodiment, due to the addition of the germanium absorption layer with the above structure, its efficiency of light absorption is improved, but at the same time, once the data is abnormal, such as data distortion, it will be amplified accordingly, so that it is easier to detect data abnormalities in subsequent processes. There are many factors that cause data abnormalities. The specific judgment and identification mechanism can be identified by existing technologies, which will not be repeated here. Once it is identified that the data distortion and other abnormalities are caused by temperature, temperature compensation can be performed by the heating unit accordingly.

[0064] In summary, in response to the millisecond-level frequent switching requirements in deep learning training scenarios, the present application provides a high-responsive computing array with a thermal compensation mechanism that can reduce light reflection, so as to achieve the design of a low-power large-scale integrated computing array while meeting the conditions of frequent switching.

[0065] In contrast to the existing methods of using phase change materials for modulation, or changing the carrier concentration by injecting current or applying voltage in the doping to change the light absorption coefficient, the present application provides an optical computing array based on a reverse biased germanium modulator, while also performing multiple controls on the light absorption characteristics of the germanium absorption layer.

[0066] First, the present application regulates the photoresponsivity of the germanium modulator by voltage. The dark current of the germanium modulator under reverse bias is extremely low, and its photocurrent during operation can be at least 2 orders of magnitude smaller than that of the forward-conducting carrier absorption modulator or phase change material modulator, thereby effectively reducing the power consumption of a single device during operation.

[0067] Furthermore, a heating unit is provided on at least one side of the germanium absorption layer, and a real-time feedback mechanism is provided to ensure the consistency and uniformity of the temperature of the entire germanium absorption layer 5, thereby increasing the number of electrons that can transition to the valence band, thereby changing the light absorption coefficient of the germanium absorption layer 5 and reducing the operating voltage of the electro-absorption modulator.

[0068] Furthermore, in the case where the light absorption cross-sectional area of ​​the light absorption region (germanium absorption layer) is relatively large (for example, "full etching"), the present application performs a partitioning design on the germanium absorption layer (light guiding region and light absorption region), and guides the light signal transmitted from the optical waveguide through a gradient interface formed by gradually changing the height and width of the light guiding region, that is, the cross-sectional area of ​​the light guiding region gradually increases from the incident end in terms of height and length, which can greatly reduce the reflection of light at the incident end when propagating in the light absorption layer (germanium absorption layer) with a larger cross-sectional area, thereby improving the light absorption rate of the modulator. It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0069] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. An optical computing array based on germanium modulators, characterized in that: include: A cross matrix, wherein the cross matrix is ​​formed by crossing a plurality of rows of mutually parallel input optical waveguides and a plurality of columns of mutually parallel output optical waveguides; A photodetector is provided at the output end of each column of the output optical waveguide; A plurality of optical splitters, wherein the optical splitters are arranged at the front end of a cross waveguide formed by each row of input optical waveguides and each column of output optical waveguides; A plurality of germanium modulators, each of which corresponds to one of the cross waveguides, and a first input end of the germanium modulator is connected to an output end of the optical splitter through a transmission optical waveguide; A plurality of optical combiners, each of which is connected to the output end of the germanium modulator and the output optical waveguide, and is used to combine the first optical signal of the corresponding cross waveguide and the second optical signal output by the germanium modulator into a third optical signal, and transmit the third optical signal to the next cross waveguide on the same output optical waveguide; Among them, the photoelectric characteristics of the light absorption layer in the germanium modulator can be changed by writing a control signal into its second input terminal, and the germanium modulator can generate a second light signal based on the first light signal input into the first input terminal and send it to the light combiner; the photoelectric characteristics include a light absorption coefficient.

2. The optical computing array according to claim 1, characterized in that: The germanium modulator comprises: a silicon substrate and an insulating layer deposited on the silicon substrate; a waveguide layer is arranged on the insulating layer; a germanium absorption layer is embedded on the waveguide layer; a first depth of the germanium absorption layer embedded in the waveguide layer is less than the thickness of the waveguide layer, or a second depth of the germanium absorption layer embedded in the waveguide layer is equal to the thickness of the waveguide layer; A heating unit is disposed on the top and / or bottom of the germanium absorption layer, and the heating unit extends along the length direction of the germanium absorption layer; or, Heating units are respectively arranged on both sides of the germanium absorption layer, and the heating units extend along the length direction of the germanium absorption layer; or, Heating unit groups are respectively arranged on both sides of the germanium absorption layer, and the heating unit group on each side includes a plurality of heating units evenly spaced along the length direction of the germanium absorption layer, wherein the heating levels of two adjacent heating units on the same side are primary heating and secondary heating respectively; The heating unit is used to change the photoelectric properties of the light absorbing layer.

3. The optical computing array according to claim 2, characterized in that: The germanium absorption layer includes a light guiding region and a light absorption region sequentially arranged along the light propagation direction. The cross-sectional area of ​​the light guiding region gradually increases from the incident end in a direction close to the light absorbing region; and the cross-sectional area of ​​the light absorbing region is the same along the light propagation direction.

4. The optical computing array according to claim 3, characterized in that: When the light guiding area is viewed from above, its width gradually increases from the incident end along the direction of light propagation; and when the light guiding area is viewed from the side, its width gradually decreases from top to bottom; or, the interface between the light guiding area and the waveguide layer is fan-shaped; and / or, the cross-section of the light absorption area is rectangular.

5. The optical computing array according to claim 2, characterized in that: The width and length of the heating unit located at the top and / or bottom of the germanium absorption layer are both smaller than the width and length of the germanium absorption layer.

6. An optical computing array based on germanium modulators, characterized in that: include: A cross matrix, wherein the cross matrix is ​​formed by crossing a plurality of rows of mutually parallel input optical waveguides and a plurality of columns of mutually parallel electrical buses; A plurality of optical splitters, the optical splitters being arranged at the front end of the intersection node between each row of optical input waveguides and each column of electrical bus; A plurality of germanium modulators, each of which corresponds to one of the cross nodes, and a first input end of the germanium modulator is connected to an output end of the optical splitter through a transmission optical waveguide; A plurality of first photodetectors, each of which is connected to the output end of the germanium modulator and the electrical bus, and is used to convert the optical signal output by the germanium modulator into an electrical signal and send it to the electrical bus; The photoelectric characteristics of the light absorption layer in the germanium modulator can be changed by writing a control signal into its second input terminal, and the germanium modulator can generate a second light signal based on the first light signal inputted from the first input terminal and send it to the first photodetector; the photoelectric characteristics include a light absorption coefficient; Therein, the product of the multiplier value and the multiplicand value is encoded in the optical signal.

7. The optical computing array according to claim 6, characterized in that: The germanium modulator comprises: a silicon substrate and an insulating layer deposited on the silicon substrate; a waveguide layer is arranged on the insulating layer; a germanium absorption layer is embedded on the waveguide layer; a first depth of the germanium absorption layer embedded in the waveguide layer is less than the thickness of the waveguide layer, or a second depth of the germanium absorption layer embedded in the waveguide layer is equal to the thickness of the waveguide layer; A heating unit is disposed on the top and / or bottom of the germanium absorption layer, and the heating unit extends along the length direction of the germanium absorption layer; or, Heating units are respectively arranged on both sides of the germanium absorption layer, and the heating units extend along the length direction of the germanium absorption layer; or, Heating unit groups are respectively arranged on both sides of the germanium absorption layer, and the heating unit group on each side includes a plurality of heating units evenly spaced along the length direction of the germanium absorption layer, wherein the heating levels of two adjacent heating units on the same side are primary heating and secondary heating, respectively.

8. The optical computing array according to claim 7, characterized in that: The germanium absorption layer includes a light guiding region and a light absorption region sequentially arranged along the light propagation direction. The cross-sectional area of ​​the light guiding region gradually increases from the incident end in a direction close to the light absorbing region; and the cross-sectional area of ​​the light absorbing region is the same along the light propagation direction.

9. The optical computing array according to claim 8, characterized in that: When the light guiding area is viewed from above, its width gradually increases from the incident end along the direction of light propagation; and when the light guiding area is viewed from the side, its width gradually decreases from top to bottom; or, the interface between the light guiding area and the waveguide layer is fan-shaped; and / or, the cross-section of the light absorption area is rectangular.

10. The optical computing array according to claim 7, characterized in that: The width and length of the heating unit located at the top and / or bottom of the germanium absorption layer are both smaller than the width and length of the germanium absorption layer.

Images