Optical computing array based on reverse bias germanium modulator

Abstract

The invention belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to an optical computing array based on a reverse bias germanium modulator, which comprises a cross matrix 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 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 application belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to an optical computing array based on a reverse-biased germanium modulator. BACKGROUND

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

[0003] In the current mainstream technical solution, the optical computing architecture based on phase change materials (PCM) (for example, the prior art CN111684343B) realizes weight modulation through reversible conversion between the crystalline state and the amorphous state of the material. Although this solution has extremely low static power consumption (up to μW level) and large-scale matrix integration capability, the phase change process has a heat accumulation effect, and the material response speed is limited (usually in the order of hundreds of ns), which is difficult to meet the millisecond-level frequent switching requirements of weight parameters in the deep learning training scenario. In addition, frequent switching will significantly increase the dynamic power consumption (up to mW per unit), resulting in a decrease in system energy efficiency.

[0004] Another type of optical computing scheme based on carrier absorption effect (for example, the prior application CN202310669033.4 proposed by the applicant) realizes optical modulation through free carrier concentration regulation under forward bias. Such devices have a response speed of nanoseconds, which can support the training-level weight update frequency, but their forward conduction current is relatively large (typical value > 100 μA per unit), and the total power consumption increases significantly (typical power consumption > 10 mW per unit) when a large-scale array is constructed, which is difficult to meet the energy efficiency requirements of high-integration systems. In addition, long-term large-current operation may cause reliability problems of the device.

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

[0006] The purpose of the present application is to provide an optical computing array based on a reverse-biased germanium modulator to partially alleviate or solve the above-mentioned deficiencies and reduce the power consumption of a large-scale optical computing chip.

[0007] In order to solve the above-mentioned technical problems, the present application specifically adopts the following technical solutions: An optical computing array based on a reverse-biased germanium modulator, comprising: a cross matrix formed by a plurality of rows of input optical waveguides parallel to each other and a plurality of columns of output optical waveguides parallel to each other; and an output end of each column of the output optical waveguides is provided with a photodetector; a plurality of optical splitters arranged at a 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 corresponding 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 connected to an output end of the germanium modulator and the output optical waveguide, for combining a first optical signal corresponding to the cross waveguide and a second optical signal output by the germanium modulator into a third optical signal and transmitting the third optical signal to a next cross waveguide on the same output optical waveguide; wherein the photoelectric property of the light absorption layer in the germanium modulator can be changed by a control signal written through a second input end, and the germanium modulator can generate a second optical signal based on a first optical signal input through the first input end and send the second optical signal to the optical combiner; the photoelectric property includes an optical absorption coefficient.

[0008] As an improvement, the germanium modulator comprises: a silicon substrate and an insulating layer deposited on the silicon substrate; the insulating layer is provided with a waveguide layer; the waveguide layer is embedded with a germanium absorption layer; a first depth of the germanium absorption layer embedded in the waveguide layer is less than a 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 arranged at 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, a heating unit is arranged at 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, a heating unit group is arranged at each side of the germanium absorption layer, and each heating unit group on each side comprises a plurality of heating units uniformly spaced along the length direction of the germanium absorption layer, wherein the heating levels of adjacent two heating units on the same side are first heating and second heating, respectively; the heating unit is used to change the photoelectric property of the light absorption layer.

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

[0010] As an improvement, the light guiding region has a width gradually increasing along the light propagation direction from the incident end when viewed from the top; and the light guiding region has a width gradually decreasing from the top to the bottom when viewed from the side; or, the interface between the light guiding region and the waveguide layer is in the shape of a sector; and / or, the cross section of the light absorbing region is in the shape of a rectangle.

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

[0012] A germanium modulator-based optical computing array, comprising: a cross matrix formed by the intersection of a plurality of rows of input optical waveguides parallel to each other and a plurality of columns of electrical buses parallel to each other; a plurality of optical splitters arranged at the front end of each intersection node of a row of optical input waveguides and a column of electrical buses; a plurality of germanium modulators, each corresponding to an intersection node, and the first input end of the germanium modulator being connected to the output end of the optical splitter through a transmission optical waveguide; a plurality of first photodetectors, each connected to the output end of the germanium modulator and the electrical bus, for converting the optical signal output by the germanium modulator into an electrical signal and sending it to the electrical bus; wherein the photoelectric property of the light absorbing layer in the germanium modulator can be changed by a control signal written through the second input end, and the germanium modulator can generate a second optical signal based on the first optical signal input through the first input end and send it to the first photodetector; the photoelectric property includes the light absorption coefficient; wherein 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; the insulating layer is provided with a waveguide layer; the waveguide layer is embedded with a germanium absorbing layer; the first depth of the germanium absorbing layer embedded in the waveguide layer is smaller than the thickness of the waveguide layer, or the second depth of the germanium absorbing layer embedded in the waveguide layer is equal to the thickness of the waveguide layer; The top and / or bottom of the germanium absorbing layer is provided with a heating unit, and the heating unit extends along the length direction of the germanium absorbing layer; or, The two sides of the germanium absorbing layer are respectively provided with a heating unit, and the heating unit extends along the length direction of the germanium absorbing layer; or, The two sides of the germanium absorbing layer are respectively provided with a heating unit group, and each side of the heating unit group comprises a plurality of heating units uniformly spaced along the length direction of the germanium absorbing layer, wherein the heating levels of the adjacent two heating units on the same side are respectively first heating and second heating.

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

[0015] As an improvement, the width of the light guiding region gradually increases from the incident end along the light propagation direction when viewed from the top; and the width of the light guiding region gradually decreases from the top to the bottom when viewed from the side; or the interface between the light guiding region and the waveguide layer is in the shape of a sector; and / or the cross-section of the light absorption region is in the shape of a rectangle.

[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. In view of the millisecond-level frequent switching requirement in the deep learning training scene, the application provides a high-response computing array with a thermal compensation mechanism and low light reflection, which can realize the design of a large-scale integrated computing array with low power consumption under the condition of meeting the frequent switching.

[0017] Unlike the existing methods of using phase change materials for modulation or changing the light absorption coefficient by injecting current or applying voltage to change the carrier concentration in doped regions, the application provides an optical computing array based on a reverse-biased germanium modulator, which simultaneously regulates the light absorption characteristics of the germanium absorption layer in multiple ways.

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

[0019] Further, a heating unit is arranged on at least one side of the germanium absorption layer, and is matched with a real-time feedback mechanism to ensure the consistency and uniformity of the temperature of the entire germanium absorption layer, thereby increasing the transitionable valence band electrons and changing the light absorption coefficient of the germanium absorption layer while reducing the operating voltage of the electrical absorption modulator. When an abnormality such as signal distortion caused by temperature (for example, the system temperature is relatively high due to large system power consumption, or the temperature is relatively high during the modulation process of the heating unit) is detected, the heating unit located inside the optical computing array can be used for temperature compensation without the need to separately set other temperature compensation modules outside the optical computing array; that is, by setting a dual-purpose heating unit, the light absorption coefficient of the germanium absorption layer can be changed, and temperature compensation can be performed to alleviate the signal distortion.

[0020] Further, in the case of a large light absorption cross-sectional area of the light absorption region (germanium absorption layer) (for example, "full etching"), the present application can reduce the reflection of light at the incident end when the light propagates in the larger cross-sectional area of the light absorption layer (germanium absorption layer) by gradually changing the height and width of the light guiding region to form a gradient interface to guide the light signal transmitted from the optical waveguide, that is, to gradually increase the cross-sectional area of the light guiding region from the incident end in terms of height and length, thereby improving the light absorption rate of the modulator. BRIEF DESCRIPTION OF DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. In all the drawings, similar elements or parts are generally identified by similar reference signs. In the drawings, each element or part is not necessarily drawn according to the actual proportion. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0021] Figure 1 An exemplary side view of the modulator in Embodiment Two of the present application; Figure 2 Another exemplary side view of the modulator in Embodiment Two of the present application; Figure 3 Still another exemplary side view of the modulator in Embodiment Two of the present application; Figure 4 A top view of the modulator in Embodiment Two of the present application; Figure 5 A front view of the germanium absorption layer in Embodiment Two of the present application; Figure 6 A top view of the germanium absorption layer in Embodiment Two of the present application; Figure 7 An exemplary structural schematic diagram of the optical computing array in Embodiment One of the present application; Figure 8 Another exemplary structural schematic diagram of the optical computing array in Embodiment One of the present application.

[0022] Marked 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 strip; 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 objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0024] Herein, using suffixes such as "module", "component" or "unit" for representing elements is only for facilitating the description of the present application, and has no specific meaning by itself. Therefore, "module", "component" or "unit" can be used mixedly. Herein, the terms "upper", "lower", "inner", "outer", "front", "back", "one end", "the other end" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for facilitating the description of the present application and simplifying the description, and do not indicate or imply that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for description purpose, and cannot be understood as indicating or implying relative importance.

[0025] Herein, unless otherwise explicitly specified and limited, the terms "mount", "provided with", "connected" and the like should be understood broadly, for example, "connected" can be fixed connection, can be detachable connection, or integrally connected; can be mechanical connection, can be directly connected, can be indirectly connected through intermediate medium, can be the communication inside two elements. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. Herein, "a plurality of" means two or more, that is, it includes two, three, four, five and the like.

[0026] Herein, the "optical splitter" can utilize components such as optical waveguide, optical coupler, heater, phase shifter and the like with specific structures to realize the distribution of optical signals inside the chip in an active or passive manner. Correspondingly, the "optical combiner" can utilize components such as optical waveguide, optical coupler, heater, phase shifter and the like with specific structures to realize the summation of optical signals inside the chip in an active or passive manner.

[0027] Embodiment one The present application provides a germanium modulator-based optical computing array, comprising: A cross matrix formed by a plurality of rows of input channels parallel to each other and a plurality of columns of output channels parallel to each other, and each column of the output optical waveguides is provided with a photodetector at the output end.

[0028] a plurality of splitters, each of which is arranged at the front end of each intersection channel formed by each row of light input channels and each column of output channels.

[0029] a plurality of signal processing units, each of which corresponds to one of the intersection channels, and a first input end of each of the signal processing units is connected to an output end of the 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 (SiO2), silicon nitride (SiN), indium phosphide (InP), gallium phosphide (GaP), germanium (Ge), lithium niobate (LiNbO3), aluminum nitride (AlN), or any 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 comprises a germanium modulator and a photodetector.

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

[0032] Compared with the existing modulation methods using phase change materials or changing the light absorption coefficient by injecting current or applying voltage to change the carrier concentration in doped regions. The present application provides a kind of optical computing array based on reverse bias germanium modulator, which is completely different from the prior art. The optical responsivity of the germanium modulator is controlled by voltage. The dark current of the germanium modulator under reverse bias is extremely low. The photocurrent during operation is at least 2 orders of magnitude smaller than that of the carrier absorption modulator or the phase change material modulator under forward conduction. Thus, the power consumption of a single device during operation is effectively reduced.

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

[0034] Specifically, the optical computing array comprises: a cross matrix formed by a plurality of rows of parallel input optical waveguides and a plurality of columns of parallel output optical waveguides; and a photodetector is arranged at the output end of each column of output optical waveguides; preferably, the input optical waveguides and the output optical waveguides are arranged vertically.

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

[0036] a plurality of germanium modulators, each of the germanium modulators corresponding to one of the cross waveguides, and a first input of the germanium modulator being connected to an output of the optical splitter through a transmission optical waveguide; a plurality of optical combiners, each of the optical combiners being connected to an output of the germanium modulator and the transmission optical waveguide, for combining a first optical signal corresponding to the cross waveguide and a second optical signal output by the germanium modulator into a third optical signal and transmitting the third optical signal to a next cross waveguide on the transmission optical waveguide; wherein an optoelectronic property of an optical absorption layer in the germanium modulator is changeable by a write control signal input through a second input of the germanium modulator, and the germanium modulator is capable of generating the second optical signal based on a first optical signal input through the first input and transmitting the second optical signal to the optical combiner, and the optoelectronic property includes an optical absorption coefficient.

[0037] That is, a plurality of rows of input optical waveguides and a plurality of columns of output optical waveguides are arranged in a cross manner to divide the optical computing array into a plurality of optical computing units, and each of the optical computing units includes a cross waveguide, an optical splitter, a germanium modulator and an optical combiner arranged at different positions of the cross waveguide.

[0038] In some other embodiments, the input channel is an input optical waveguide, the output channel is an electrical bus, and correspondingly, the signal processing unit is a germanium modulator and a photodetector (i.e., a first photodetector in the following).

[0039] Specifically, a cross matrix is formed by a plurality of rows of input optical waveguides parallel to each other and a plurality of columns of electrical buses parallel to each other; preferably, the input optical waveguides are perpendicular to the electrical buses.

[0040] a plurality of optical splitters arranged at a front end of each cross node of each row of input optical waveguides and each column of electrical buses; preferably, the optical splitters are arranged at a front end of the input optical waveguide in the cross waveguide.

[0041] a plurality of germanium modulators, each of the germanium modulators corresponding to one of the cross nodes, and a first input of the germanium modulator being connected to an output of the optical splitter through a transmission optical waveguide; a plurality of first photodetectors, each of the first photodetectors being connected to an output of the germanium modulator and the electrical bus, for converting an optical signal output by the germanium modulator into an electrical signal and transmitting the electrical signal to the electrical bus; wherein an optoelectronic property of an optical absorption layer in the germanium modulator is changeable by a write control signal input through a second input of the germanium modulator, and the germanium modulator is capable of generating the second optical signal based on a first optical signal input through the first input and transmitting the second optical signal to the first photodetector, and the optoelectronic property includes an optical absorption coefficient. The product of the multiplier value and the multiplicand value is encoded in the optical signal.

[0042] That is, the multiple rows of input optical waveguides and the multiple rows of electrical buses are cross arranged to divide the optical computing array into multiple optical computing units, the optical computing units comprising a cross waveguide, and an optical splitter, a germanium modulator, a first photodetector, and an optical combiner arranged at different positions of the cross waveguide.

[0043] Embodiment Two The embodiment provides a germanium modulator applied to the optical computing array in the embodiment one, comprising a silicon substrate 1 and an insulating layer 4 deposited on the silicon substrate 1; the insulating layer 4 is provided with a waveguide layer 2; the waveguide layer 2 is embedded with a germanium absorption layer 5; the 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 the 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 means 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 means 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 taken as the etching end point, on the one hand, the germanium absorption layer 5 can have a larger cross section, so that the light field overlapping time in the modulation region is the longest. In the same length, the responsivity is higher; in the same responsivity, the size is the smallest. On the other hand, the etching depth is easy to control, which can ensure the consistency of the etching groove depth between different modulators. In the traditional shallow etching process, due to the shallow etching depth and the difficulty in accurate control, the etching depth is easily affected by the uneven thickness of the silicon layer, resulting in inconsistent etching depth and affecting the performance uniformity of the modulator. The etching groove process reaching the insulating layer 4 has better stability, which is beneficial to mass production of high-quality modulators.

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

[0047] In some specific embodiments, heating units 3 are provided at the top and / or bottom of the germanium absorption layer 5, and the heating units 3 extend along the length direction of the germanium absorption layer 5; or, heating units 3 are 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 groups 3 are provided on both sides of the germanium absorption layer 5, and each heating unit group 3 includes multiple 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 on the same side are primary heating and secondary heating, respectively; the heating units 3 are used to change the photoelectric properties of the light absorption layer.

[0048] Unlike the traditional approach of relying on high electric field strength to increase the absorption coefficient and thus ensure the uniformity of photocurrent density, this invention provides a thermal compensation mechanism that only targets the endpoint effect. Specifically, by setting 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 of the germanium absorption layer, ensuring the consistency and uniformity of the temperature of the entire germanium absorption layer 5, thereby increasing the number of valence band electrons that can jump, thereby changing the light absorption coefficient of the germanium absorption layer 5 while reducing the operating voltage of the electroabsorption modulator. In this process, it is only necessary to ensure the final light absorption rate (i.e., 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] In other words, this application provides a thermal compensation mechanism that dually regulates the light absorption coefficient, targeting only 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. Then, the light absorption coefficient of the germanium absorption layer is further adjusted by adjusting the input voltage. That is to say, the adjustment requirements of the input voltage in this process are not high. In other words, the response speed of the computing array can be guaranteed while ensuring low energy consumption, thereby meeting the requirements of large-scale matrices.

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

[0051] The first judgment module is used to determine whether the actual temperature value monitored by the temperature monitoring module is greater than a first preset temperature threshold. If the actual temperature value is greater than the first preset temperature threshold, a first control signal indicating that heating has stopped 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, a second control signal indicating that monitoring continues is generated and sent to the temperature monitoring module; and / or, A temperature monitoring module is configured to monitor the actual temperature value of the germanium absorption layer 5 in real time after the heating unit 3 in the heating state with the first heating level is heated.

[0052] A second judging module is configured to judge whether the actual temperature value monitored by the temperature monitoring module reaches a preset target temperature threshold value within a preset time length, and if not, generate and send a third control signal representing the heating unit 3 in the heating state with the second heating level is started, so that the actual temperature of the germanium absorption layer 5 reaches the preset target temperature threshold value.

[0053] The first temperature threshold value can be obtained by a large number of experiments in advance, or be preset by the user according to experience. When the actual temperature is near the first preset temperature threshold value, the number of transitionable valence band electrons tends to be maximized, but at the same time, the material itself will not be adversely affected.

[0054] The division of the heating level (first and second) is only to distinguish between the two, and cannot limit the heating power or other characteristics. In the case of only starting the first heating, the heating power is small, and when the first heating and the second heating are started at the same time, the heating power increases, and the temperature of the germanium absorption layer 5 can also be correspondingly increased.

[0055] The present application can maximize the number of transitionable valence band electrons as much as possible, and on the other hand, can improve the stability of the temperature of the germanium absorption layer 5, and prevent the problem that the light signal emitted by the germanium absorption layer 5 is unstable 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 region and a light absorbing region arranged in sequence along the light propagation direction, wherein the cross-sectional area of the light guiding region gradually increases from the incident end along the direction close to the light absorbing region; the cross-sectional area of the light absorbing region is the same along the light propagation direction.

[0057] In some specific embodiments, the longitudinal section of the light guiding region 51 is a right trapezoid, and the included angle a between the hypotenuse of the right trapezoid and the bottom side is 86°-89°, the hypotenuse corresponding to the interface between the light guiding region 51 and the waveguide layer 2; the longitudinal section of the light absorbing region 52 is a rectangle; or the interface between the light guiding region 51 and the waveguide layer 2 is a sector. Wherein, the longitudinal section refers to the vertical plane parallel to the length direction of the germanium absorption layer.

[0058] The width of the light guiding area is gradually increased from the incident end along the light propagation direction in a plan view, and the width of the light guiding area is gradually decreased from the top to the bottom in a side view, or the interface between the light guiding area and the waveguide layer is in a sector shape, and / or the cross section of the light absorbing area is in a rectangular shape.

[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. By gradually changing the structure, 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 in different refractive index media, the greater the difference in refractive index, the more serious the reflection. This gradual transition structure can make the light enter the germanium absorbing layer 5 more smoothly, improve the coupling efficiency of the light, and thus improve the light absorption capacity of the modulator.

[0060] In an ideal case, the light guiding area is a cone with a small front and a large back, and the conical structure can achieve a more perfect refractive index gradient, minimizing the reflection of light when entering the germanium absorbing layer 5, and theoretically maximizing the coupling efficiency of the light.

[0061] Due to process limitations, the conical light guiding area requires high cost. Therefore, in order to reduce the process difficulty in this embodiment, only the cross-sectional area of the light guiding area is gradually increased from the incident end along the direction close to the light absorbing area 52, for example, the light guiding area is a triangle with a narrow front and a wide back in a plan view, and a trapezoid with a large top and a small bottom in a side view. Although it is different from the ideal conical shape, the trapezoidal structure can still achieve a certain degree of refractive index gradient and reduce light reflection, which is a feasible solution under the existing process conditions.

[0062] That is, by limiting the shape of the light guiding area, the cross-sectional area of the light guiding area 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 a larger cross-sectional area of the light absorbing layer (germanium absorbing layer), and improve the light absorption rate of the modulator. That is, the present application provides a full etching scheme with a thermal compensation mechanism and capable of reducing light reflection.

[0063] In some embodiments, the width and length of the heating unit 3 located on the top and / or bottom of the germanium absorption layer 5 are smaller than the width and length of the germanium absorption layer 5. In this way, the heating effect is ensured while unnecessary heat waste is avoided. In the present embodiment, the efficiency of light absorption is improved due to the adoption of the above-mentioned structure of the germanium absorption layer. However, once there is data abnormality, such as data distortion, the data abnormality is amplified accordingly, so that the data abnormality is more easily detected in the subsequent process. There are various factors that cause data abnormality, and the specific judgment and identification mechanism can be identified by using the existing technology, which will not be described here. Once it is identified that the data distortion and other abnormalities are caused by temperature, the temperature compensation can be performed by the heating unit accordingly.

[0064] In summary, for the millisecond-level frequent switching requirement in the deep learning training scene, the present application provides a high-response computing array with a thermal compensation mechanism and low light reflection, which can realize the design of a large-scale integrated computing array with low power consumption under the condition of meeting the frequent switching requirement.

[0065] In contrast to the existing methods of using phase change materials for modulation or changing the light absorption coefficient by injecting current or applying voltage to change the carrier concentration in doped layers, the present application provides a light computing array based on a reverse-biased germanium modulator, which simultaneously performs multiple regulation on the light absorption characteristics of the germanium absorption layer.

[0066] Firstly, the present application regulates the light response of the germanium modulator by voltage. The dark current of the germanium modulator under reverse bias is extremely low. The photocurrent during operation is at least 2 orders of magnitude smaller than that of the carrier absorption modulator or the phase change material modulator under forward conduction, thereby effectively reducing the power consumption of the individual device during operation.

[0067] Further, a heating unit is arranged on at least one side of the germanium absorption layer, and a real-time feedback mechanism is used to ensure the consistency and uniformity of the temperature of the entire germanium absorption layer 5, thereby increasing the transitionable valence band electrons and changing the light absorption coefficient of the germanium absorption layer 5 while reducing the operating voltage of the electrical absorption modulator.

[0068] Further, in the case of a large light absorption cross-sectional area of the light absorption region (germanium absorption layer) (for example, "full etching"), the present application designs the germanium absorption layer in zones (light guiding zone and light absorption zone), and gradually changes the height and width of the light guiding zone to form a gradual interface to guide the light signal transmitted from the optical waveguide, that is, the cross-sectional area of the light guiding zone gradually increases from the incident end in terms of height and length, which can greatly reduce the reflection of light in the incident end when the light propagates in the larger cross-sectional area of the light absorption layer (germanium absorption layer), and improve the light absorption rate of the modulator. It should be noted that, in this document, the terms "comprising", "comprises" or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises a" does not, without more limitations, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0069] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are merely illustrative, not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims.

Claims

1. An optical computing array based on reverse-biased germanium modulators, characterized in that, The application relates to a cross-matrix formed by a plurality of rows of parallel input optical waveguides and a plurality of columns of parallel output optical waveguides. A plurality of light splitters are arranged at the front end of the cross waveguide formed by each row of input optical waveguides and each column of output optical waveguides. A plurality of germanium modulators are provided, each corresponding to one cross waveguide, and the first input end of the germanium modulator is connected to the output end of the light splitter through a transmission optical waveguide. A plurality of light combiners are connected to the output end of the germanium modulator and the output optical waveguide respectively, and are used for combining 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 transmitting the third optical signal to the next cross waveguide on the same output optical waveguide. The photoelectric property of the light absorption layer in the germanium modulator can be changed by the control signal input through the second input end, and the germanium modulator can generate the second optical signal based on the first optical signal input through the first input end and send the second optical signal to the light combiner; the photoelectric property includes the light absorption coefficient. 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; and a germanium absorption layer is embedded in the waveguide layer. At least one side of the germanium absorption layer is provided with a heating unit; the heating unit is used for changing the photoelectric property of the light absorption layer. The germanium absorption layer comprises a light guiding area and a light absorption area arranged in sequence along the light propagation direction, wherein the cross-sectional area of the light guiding area gradually increases along the direction close to the light absorption area from the incident end; and the cross-sectional area of the light absorption area is the same along the light propagation direction. The first depth at which the germanium absorption layer is embedded in the waveguide layer is smaller than the thickness of the waveguide layer, or the second depth at which the germanium absorption layer is embedded in the waveguide layer is equal to the thickness of the waveguide layer.

2. The reverse-biased germanium modulator-based optical computing array of claim 1, wherein, The heating unit is arranged 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 3. The reverse-biased germanium modulator-based optical computing array of claim 1, wherein, The heating unit is arranged on the two sides of the germanium absorption layer, and the heating unit extends along the length direction of the germanium absorption layer; or A heating unit group is arranged on each side of the germanium absorption layer, and each heating unit group comprises a plurality of heating units uniformly and spacedly arranged along the length direction of the germanium absorption layer, wherein the heating levels of the adjacent two heating units on the same side are first heating and second heating respectively. The width of the light guiding area gradually increases from the incident end along the light propagation direction when viewed from the top; and the width of the light guiding area gradually decreases from the top to the bottom when viewed from the side.

4. The reverse-biased germanium modulator-based optical computing array of claim 1, wherein, The width and length of the heating unit arranged on the top and / or bottom of the germanium absorption layer are smaller than the width and length of the germanium absorption layer.

5. The reverse-biased germanium modulator-based optical computing array of claim 3, wherein, The input optical waveguide and the output optical waveguide are arranged vertically.

6. The reverse-biased germanium modulator-based optical computing array of claim 1, wherein, The germanium modulator further comprises:

7. The reverse-biased germanium modulator-based optical computing array of claim 1, wherein, A temperature monitoring module for monitoring the actual temperature value of the germanium absorption layer in real time.

8. The reverse-biased germanium modulator-based optical computing array of claim 3, wherein, ​ ​ The first judging module is configured 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, generate and send a first control signal representing stopping heating to the heating unit or the heating unit group; if the actual temperature value is less than the first preset temperature threshold value, generate and send a second control signal representing continuing monitoring to the temperature monitoring module; Alternatively, the temperature monitoring module is configured to monitor the actual temperature value of the germanium absorption layer after the heating unit in a heating state and with a heating level of one level is heated in real time. The second judging module is configured to judge whether the actual temperature value monitored by the temperature monitoring module reaches a preset target temperature threshold value after a preset time length, and if not, generate and send a third control signal representing starting the heating unit in a dormant state and with a heating level of two levels, so that the actual temperature of the germanium absorption layer 5 reaches the preset target temperature threshold value.

9. The reverse-biased germanium modulator-based optical computing array of claim 1, wherein, The longitudinal section of the light guiding area is a right trapezoid, and the hypotenuse of the right trapezoid corresponds to the interface between the light guiding area and the waveguide layer, and the included angle α between the hypotenuse and the base is 86°-89°.

10. The reverse-biased germanium modulator-based optical computing array of claim 1, wherein: The interface between the light guiding area and the waveguide layer is a sector, and the longitudinal section of the light absorbing area is a rectangle.

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