Photoelectric nonlinear active device and chip based on monolithic integrated bjt current mirror

Abstract

This invention discloses a photoelectric nonlinear activation device and chip based on a monolithically integrated BJT current mirror. The photoelectric nonlinear activation device integrates a photodetector, a BJT current mirror, and an optical nonlinear device on a single chip. The BJT current mirror directly amplifies the photocurrent to drive the optical device, eliminating the need for a transimpedance amplifier or operational amplifier. Direct current domain transmission eliminates the need for a current-to-voltage conversion stage and feedback network, simplifying the circuit structure. Passive current amplification reduces additional power supply requirements, and combined with on-chip local interconnects, reduces parasitic parameters, effectively lowering power consumption. This achieves a compact, low-power photoelectric nonlinear activation function, thus solving the problems of complex circuit structure and high power consumption in existing hybrid photoelectric nonlinear activation schemes.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic integration technology, and more specifically to an optoelectronic nonlinear activation device and chip based on a monolithically integrated BJT current mirror. Background Technology

[0002] Optical Neural Networks (ONNs) utilize the high-speed propagation of light, wavelength division multiplexing (WDM), and parallel processing capabilities to perform linear operations such as matrix-vector multiplication, convolution, and weighted summation in the optical domain. To enable multilayer networks to fit complex functions, nonlinear activation units are added after the linear calculations.

[0003] Existing on-chip nonlinear activation technologies mainly include two schemes: all-optical nonlinearity and optoelectronic hybrid nonlinearity. All-optical nonlinearity utilizes the Kerr effect, free carrier effect, saturated absorption, or phase-change materials to achieve nonlinear functions, but it typically places high demands on optical power, operating length, material properties, or thermal management, making it difficult to implement in low-power, miniaturized on-chip systems. Optoelectronic hybrid nonlinearity, on the other hand, first converts the optical signal into an electrical signal using a photodetector, then amplifies it through electronic circuitry and drives tunable optical devices such as microring resonators to achieve a nonlinear optical-electrical-optical mapping. Microring resonators are characterized by their small size, strong wavelength selectivity, and significant nonlinearity in their resonant transmission curve. When their carrier concentration, temperature, or effective refractive index changes, the resonant wavelength shifts. Under a fixed detection wavelength, the output optical power varies with the driving signal in a threshold, S-shaped, peak, or saturation manner, making them suitable as on-chip nonlinear activation devices.

[0004] However, existing optoelectronic hybrid nonlinear activation schemes suffer from the following technical problems: First, they typically rely on transimpedance amplifiers to convert weak photocurrents into voltages before driving optical devices. This results in activation units containing operational amplifier gain stages, feedback resistors, and compensation networks, leading to complex structures and layouts that are unfavorable for high-density replication in large-scale optical neural networks. Second, the photocurrent directly output by photodetectors is relatively small, requiring additional voltage amplification stages to provide sufficient device drive current, increasing circuit stages and power consumption. Furthermore, the multiple signal conversions between the current and voltage domains increase power consumption and dynamic range matching difficulties, reducing energy efficiency. Finally, discrete or heterogeneously integrated photodetectors, amplifiers, and optical devices require pads, wire bonding, or cross-layer interconnects, introducing parasitic capacitances, inductances, and series resistances, limiting response speed and array density, and increasing packaging complexity. In addition, different input optical powers, device Q values, coupling coefficients, and thresholds require different gains and biases. Existing fixed circuit structures lack sufficient tunability and reusability, making them unsuitable for large-scale wavelength division multiplexing or neural network array applications.

[0005] Therefore, in order to solve the above problems, the present invention provides a simple and low-power optoelectronic nonlinear activation device and chip based on a monolithically integrated BJT current mirror. Summary of the Invention

[0006] This invention provides a photoelectric nonlinear activation device and chip based on a monolithically integrated BJT current mirror, aiming to solve the problems of complex circuit structure and high power consumption in existing photoelectric hybrid nonlinear activation schemes.

[0007] To achieve the above objectives, on one hand, the present invention provides a photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror, comprising: a photodetector for receiving control light and generating photocurrent; a BJT current mirror including a first bipolar junction transistor (BJT) and a second BJT, wherein the collector and base of the first BJT are connected to form a reference branch, and the output terminal of the photodetector is connected to the reference branch so that the BJT current mirror amplifies the photocurrent to form a driving current, and the collector of the second BJT serves as a current output terminal to output the driving current; and an optical nonlinear device having a current driving terminal directly connected to the current output terminal, wherein the optical nonlinear device receives modulated light and outputs nonlinear optical power under the modulation of the driving current, wherein the photodetector, the BJT current mirror, and the optical nonlinear device are integrated on the same substrate.

[0008] The further technical solution is as follows: the driving current is the current formed after the photocurrent is amplified by the BJT current mirror with a mirror gain greater than a preset gain value, and the mirror gain is set by the effective emitter junction area ratio or the number of parallel units of the first bipolar junction transistor and the second bipolar junction transistor.

[0009] The further technical solution is as follows: the first bipolar junction transistor and the second bipolar junction transistor are selected from any of the following combinations: both are lateral bipolar junction transistors, both are vertical bipolar junction transistors, one of which is a lateral bipolar junction transistor and the other is a vertical bipolar junction transistor.

[0010] The further technical solution is as follows: the emitter region, base region and collector region of the vertical bipolar junction transistor are arranged sequentially along the thickness direction of the substrate, and the emitter region, the base region and the collector region are formed using doped regions and contact structures in standard semiconductor processes.

[0011] The further technical solution is as follows: the optical nonlinear device is any one of the following: microring resonator, microdisk resonator, Mach-Zehnder interferometer, electroabsorption modulator, Bragg resonator, photonic crystal cavity, thermo-optical phase shifter, and variable optical attenuator.

[0012] The further technical solution is as follows: the micro-ring resonator is an Add-Drop type micro-ring resonator, which includes an input bus waveguide, a download bus waveguide, and a ring waveguide located between the input bus waveguide and the download bus waveguide. The modulated light is input from the input bus waveguide, and after resonance in the ring waveguide, the nonlinear optical power is output from the download end or from the direct end through the download bus waveguide.

[0013] A further technical solution includes an optical coupler, which is an input coupler and / or a beam splitter; wherein the input coupler is a grating coupler or an edge coupler, used to couple the input light into the on-chip waveguide; the beam splitter is a directional coupler or a multimode interference coupler, used to split the input light into a first proportion of light and a second proportion of light, wherein the first proportion of light is used as the control light input to the photodetector, and the second proportion of light is used as the modulated light input to the optical nonlinear device.

[0014] A further technical solution is as follows: the control light is an external light source independent of the modulated light, and the control light and the modulated light have at least one of different wavelengths, powers, or codes.

[0015] The further technical solution is as follows: the photodetector, the BJT current mirror and the optical nonlinear device are arranged adjacent to each other on the same substrate, and at least one of the following is provided between them: optical isolation trench, metal shielding layer and thermal isolation structure.

[0016] To achieve the above objectives, in another aspect, the present invention also provides a photoelectric nonlinear activation chip, comprising: a plurality of photoelectric nonlinear activation devices based on a monolithically integrated BJT current mirror as described in one aspect above, wherein the plurality of photoelectric nonlinear activation devices are arranged along one or more waveguide arrays to form a wavelength division multiplexing parallel nonlinear activation array; wherein each wavelength channel is configured with an independent nonlinear activation unit, or multiple photodetectors jointly drive an optical nonlinear device through a current summing node.

[0017] This invention provides a photoelectric nonlinear activation device and chip based on a monolithically integrated BJT current mirror. The photoelectric nonlinear activation device includes: a photodetector for receiving control light and generating a photocurrent; a BJT current mirror comprising a first bipolar junction transistor (BJT) and a second BJT, wherein the collector and base of the first BJT are connected to form a reference branch, and the output terminal of the photodetector is connected to the reference branch, so that the BJT current mirror amplifies the photocurrent to form a driving current, and the collector of the second BJT serves as a current output terminal to output the driving current; and an optical nonlinear device having a current driving terminal directly connected to the current output terminal, the optical nonlinear device for receiving modulated light and outputting nonlinear optical power under the modulation of the driving current; wherein the photodetector, the BJT current mirror, and the optical nonlinear device are integrated on the same substrate. In this invention, the photodetector, the BJT current mirror, and the optical nonlinear device are monolithically integrated, and the BJT current mirror directly amplifies the photocurrent to drive the optical device, eliminating the need for a transimpedance amplifier or operational amplifier. Direct current-domain transmission eliminates the need for a current-to-voltage conversion stage and feedback network, simplifying the circuit structure. Passive current amplification reduces additional power supply requirements, and combined with on-chip local interconnects, it lowers parasitic parameters, effectively reducing power consumption. This achieves a compact, low-power optoelectronic nonlinear activation function, thus solving the problems of complex circuit structure and high power consumption in existing optoelectronic hybrid nonlinear activation schemes. Attached Figure Description

[0018] Figure 1 A block diagram of a photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror provided in an embodiment of the present invention; Figure 2 A schematic cross-sectional view of a common-emitter dual BJT provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the lateral structure of a common-emitter dual BJT provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the overall structure of a photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of the monolithic fabrication and metal interconnection of a microring, a BJT, and a detector provided in an embodiment of the present invention. Figure 6 The two-port spectrum and nonlinear activation performance test diagram of the Add-Drop type microring resonator provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Similar component reference numerals in the drawings represent similar components. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1 , Figure 1 This is a block diagram of a photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror according to an embodiment of the present invention, as shown below. Figure 1As shown, the photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror includes a photodetector, a BJT current mirror, and an optical nonlinear device. The photodetector receives control light and generates a photocurrent. The BJT current mirror includes a first bipolar junction transistor (BJT) and a second BJT. The collector and base of the first BJT are connected to form a reference branch, and the output of the photodetector is connected to the reference branch. This allows the BJT current mirror to amplify the photocurrent and generate a driving current. The collector of the second BJT serves as the current output terminal, outputting the driving current. The optical nonlinear device has a current driving terminal directly connected to the current output terminal. The optical nonlinear device receives modulated light and outputs nonlinear optical power under the modulation of the driving current. The photodetector, the BJT current mirror, and the optical nonlinear device are integrated on the same substrate. It should be noted that in this embodiment, direct connection means that no transimpedance amplifier or operational amplifier-type current-to-voltage conversion stage is provided between the current output terminal of the BJT current mirror and the current driving terminal of the optical nonlinear device; the current signal is directly transmitted in the current domain. In an optional embodiment of the present invention, auxiliary components such as a bias current source, current-limiting resistor, protection circuit, switch, or current summing node are allowed to be provided between the current output terminal and the current driving terminal. These components do not change the essential characteristics of current domain transmission and still belong to the category of direct connection. It should also be noted that the base of the first bipolar junction transistor is connected to the base of the second bipolar junction transistor, and the emitters of both the first and second bipolar junction transistors are connected to a common low potential terminal. Furthermore, in this embodiment, the photodetector is a silicon / germanium vertical PIN detector formed on an SOI (Silicon-On-Insulator) substrate. The photodetector includes a silicon waveguide coupling region, a germanium absorption region, a P-type region, an I-type or lightly doped absorption region, an N-type region, and a P++ / N++ contact region. Understandably, after the controlled light couples into the germanium absorption region in the silicon waveguide coupling region, electron-hole pairs are generated, forming a photocurrent under zero bias or reverse bias conditions. The photocurrent can be expressed as: I PD = R PD × P PD + I dark Among them, I PD R is the photocurrent output by the photodetector. PD For the responsivity of the photodetector, P PD I represents the optical power received by the photodetector. dark It is dark current.

[0021] In one specific embodiment, the photodetector has a measured responsivity of 0.97 A / W at a wavelength of 1545.6 nm.

[0022] In some embodiments, such as this one, the driving current is the current formed after the photocurrent is amplified by the BJT current mirror with a mirror gain greater than a preset gain value. The mirror gain is set by the effective emitter junction area ratio or the number of parallel units of the first bipolar junction transistor and the second bipolar junction transistor. It should be noted that in this embodiment, the mirror gain is the ratio of the collector output current of the second bipolar junction transistor to the collector reference current of the first bipolar junction transistor. The mirror gain is greater than the preset gain value, which is preferably 1, i.e., the mirror gain is greater than 1. It should also be noted that, considering the finite current amplification factor, device mismatch, and output compliance voltage, the actual mirror gain may have deviations. To improve mirror accuracy, the following structures can be adopted: Wilson current mirror: using a three-transistor structure to improve output impedance and mirror accuracy; β-compensation structure: adding a compensation transistor to reduce the influence of base current on mirror gain; cascaded structure: using a common-emitter-common-base cascade to improve the output compliance voltage range and mirror accuracy.

[0023] In some embodiments, such as this embodiment, the first bipolar junction transistor (BJT) and the second BJT are selected from any combination of the following: both are lateral BJTs, both are vertical BJTs, or one is a lateral BJT and the other is a vertical BJT. Specifically, the emitter region, base region, and collector region of the vertical BJT are sequentially arranged along the thickness direction of the substrate, and the emitter region, base region, and collector region are formed using doped regions and contact structures in standard semiconductor processes. It should be noted that, in this embodiment, a lateral BJT refers to a BJT where the main carrier transport direction is substantially parallel to the substrate surface; a vertical BJT refers to a BJT where the emitter region, base region, and collector region are sequentially arranged along a direction perpendicular to the substrate surface, and the main carrier transport direction is substantially perpendicular to the substrate surface. It should also be noted that, in this embodiment, the first and second bipolar junction transistors in the same BJT current mirror preferably employ the same device structure, doping conditions, and layout units to improve device matching and reduce mirror error. Depending on the process conditions, a combination of lateral and vertical bipolar junction transistors, a complementary NPN and PNP structure, or a multi-level mirror structure can also be used. Furthermore, in this embodiment, the vertical bipolar junction transistor can be formed using the well region, deep well region, substrate region, heavily doped source / drain regions, contact regions, and metal interconnect layers from CMOS, SOI CMOS, or BiCMOS processes. In one embodiment, the vertical NPN bipolar junction transistor includes an N-type collector region, a P-type base region, and an N+ type emitter region disposed along the substrate thickness direction. In another embodiment, the vertical PNP bipolar junction transistor includes a P-type collector region, an N-type base region, and a P+ type emitter region disposed along the substrate thickness direction.

[0024] Understandably, a vertical bipolar junction transistor can be a parasitic bipolar junction transistor formed using existing CMOS process layers, or an independent vertical bipolar junction transistor formed using dedicated base, emitter, or collector processes.

[0025] Please see Figure 2 and Figure 3 , Figure 2 This is a schematic cross-sectional view of a common-emitter dual BJT provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the lateral structure of a common-emitter dual BJT provided in an embodiment of the present invention.

[0026] like Figure 2As shown, the first bipolar junction transistor Q1 and the second bipolar junction transistor Q2 adopt a mirror-symmetric lateral NPN structure, including a collector region (N++ / N), a base region (P), and an emitter region (N++) arranged sequentially along the horizontal direction of the substrate surface. Q1 and Q2 share a central emitter region, with their respective collector regions on either side, and are covered by a SiO2 isolation layer. Figure 3 As shown, Q1 and Q2 are arranged symmetrically on the layout, with collectors (C) on both sides and a common emitter (E) in the middle. The base (B) is located below the emitter region. The collector and base of Q1 are shorted to form a reference branch, and the collector of Q2 serves as the current output terminal to improve device matching and reduce image error.

[0027] In some embodiments, such as this one, the optical nonlinear device is any one of a microring resonator, a microdisk resonator, a Mach-Zehnder interferometer, an electro-absorption modulator, a Bragg resonator, a photonic crystal cavity, a thermo-optical phase shifter, and a variable optical attenuator. Specifically, the microring resonator is an Add-Drop type microring resonator, which includes an input bus waveguide, a download bus waveguide, and a ring waveguide located between the input bus waveguide and the download bus waveguide. The modulated light is input from the input bus waveguide, resonates within the ring waveguide, and is output as nonlinear optical power from the download end or the through end via the download bus waveguide. It should be noted that the optical nonlinear device is an optical device with a current-tunable optical transfer function. The amplified current output from the BJT current mirror is directly input to the current drive terminal of the optical nonlinear device, causing changes in its resonant wavelength, phase, absorption coefficient, coupling state, or transmittance, thereby forming a nonlinear optical output. It should also be noted that the microring resonator has a microring radius of 40 μm, a waveguide width of 500 nm, coupling spacings of 150 nm and 250 nm on both sides, an operating wavelength of 1545.6 nm, a free spectral range of 3.4 nm, and a quality factor of 2630. The microring resonator is current-tuned through carrier injection, carrier depletion, thermo-optic effects, or a combination thereof.

[0028] Please see Figure 4 , Figure 4 This is a schematic diagram of the overall structure of a photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror, according to an embodiment of the present invention. Figure 4 As shown, the photoelectric nonlinear activation device includes a photodetector, a BJT current mirror, and an optical nonlinear device, which is a microring resonator. Figure 4 In this circuit, the microring resonator is simply referred to as a microring. The input probe light is incident on the photodetector, generating an input photocurrent. This photocurrent is amplified by the BJT current mirror to form an output current that drives the microring resonator. The modulated output light is then emitted from the microring. It should be noted that in... Figure 4In the diagram, the diagonal lines represent Si material, the dark lines represent P++ doped regions, and the light lines represent N++ doped regions. It should also be noted that... Figure 4 The output light in Figure 1 The output nonlinear optical power is consistent with that in the process.

[0029] In some embodiments, such as this embodiment, as Figure 1 As shown, the photoelectric nonlinear activation device further includes an optical coupler, which is an input coupler and / or a beam splitter coupler; wherein, the input coupler is a grating coupler or an edge coupler, used to couple the input light into an on-chip waveguide; the beam splitter is a directional coupler or a multimode interference coupler, used to split the input light into a first proportion of light and a second proportion of light according to a ratio, the first proportion of light being used as the control light input to the photodetector, and the second proportion of light being used as the modulated light input to the optical nonlinear device. It should be noted that the control light is an external light source independent of the modulated light, and the control light and the modulated light have at least one of different wavelengths, powers, or codes. It should also be noted that the optical coupler supports two operating modes: (1) Independent control light mode: the control light enters the photodetector to form a photocurrent, and another beam of modulated light enters the optical nonlinear device and is output from the output end. The control light and the modulated light can have at least one of different wavelengths, powers, and codes; (2) Self-activated beam splitting mode: the input light is split by the beam splitter, and the light with a ratio of α enters the photodetector as the first ratio light, and the light with a ratio of 1-α enters the optical nonlinear device as the second ratio light. The photocurrent generated by the photodetector is amplified by the BJT current mirror and directly drives the same optical nonlinear device to realize the optical-electrical-optical nonlinear mapping of the same input signal. It should also be further noted that when the Add-Drop type micro-ring resonator is used, the modulated light is input from the input bus waveguide, resonates in the ring waveguide, and is output from the download end of the download bus waveguide or the through end of the input bus waveguide. During operation, the control light or beam splitter enters the photodetector and generates a reference photocurrent. The BJT current mirror outputs an amplified current according to the effective emitter junction area ratio or the number of parallel units. The amplified current is summed with the selectable bias current and then directly drives the optical nonlinear device, causing changes in its resonant wavelength, loss, or coupling state, thereby forming a nonlinear output at a fixed detection wavelength.

[0030] In some embodiments, such as this one, under the self-activated beam splitting method, the input optical power P IN After being distributed by the beam splitter according to the splitting ratio α, the optical power received by the photodetector is P. PD =α·P IN .

[0031] BJT current mirror output current I Mand the total drive current I of optical nonlinear devices DRV They are respectively: I M =G I ·I PD I DRV =I M +I BIAS Among them, I PD G outputs photocurrent for the photodetector. I I represents the actual current gain (greater than 1) of the BJT current mirror. BIAS This is an optional on-chip bias current used for threshold shifting.

[0032] For a typical current-driven optical nonlinear device, its output optical power can be expressed as: P OUT =P OPT ·F OPT (I DRV ,λ,p) Among them, P OPT To obtain the modulated optical power entering the optical nonlinear device, I DRV The driving current provided by the BJT current mirror, λ is the wavelength of the modulated light, p is the structural parameters and operating state of the optical device, and F OPT This is the power transfer function for optical nonlinear devices.

[0033] When the optical nonlinear device is an Add-Drop type microring resonator, the output optical power is specifically expressed as follows: P OUT =P PROBE ·T[λ probe ,λ res (I DRV )] Among them, P PROBE To fix the probe light power, λ probe For the detection wavelength, T is the power transfer function at the through or download end of the Add-Drop microring resonator, λres(I DRV ) represents the resonant wavelength of the microring that varies with the driving current.

[0034] The nonlinear relationship formation mechanism: The photodetector and the BJT current mirror are approximately linear within the specified operating range, while the transmission rate of the Add-Drop microring resonator changes in a Lorentz-type or notch-type manner with wavelength detuning. Therefore, a nonlinear relationship is formed between the input control optical power and the output optical power.

[0035] Adjustable parameters include: detection wavelength, output port (through or download), image magnification, bias current, coupling distance, and quality factor. By adjusting these parameters, the activation threshold, slope, dynamic range, and saturation region can be adjusted.

[0036] In some embodiments, such as this one, the photodetector, the BJT current mirror, and the optical nonlinear device are arranged adjacently on the same substrate, with at least one of optical isolation trenches, a metal shielding layer, and a thermal isolation structure between them. This effectively reduces the impact of control light irradiation of the BJT and driving current heating on the photodetector, improving the stability and reliability of the photoelectric nonlinear activation device. It should be noted that the photodetector, BJT current mirror, optical nonlinear device, optical waveguide, and metal interconnects are formed on the same substrate, and the electrical connection between the photodetector and the BJT current mirror, and between the BJT current mirror and the optical nonlinear device, is achieved through on-chip metal interconnects. It should also be noted that a standard 8-inch, 220 nm device layer SOI platform is used, and the optical nonlinear device is a silicon-based Add-Drop microring resonator. The microring (add-drop type microring resonator) and silicon waveguide are formed by etching the device layer; the microring PN junction and the P-type, N-type, P++, and N++ regions of the BJT are formed through ion implantation and high-temperature annealing; the detector is formed through selective germanium epitaxy and germanium doping; subsequently, a silicon dioxide cladding is deposited, contact holes are formed, silicon is metallized, and aluminum metal is sputtered to form aluminum or other metal interconnects. It should be further noted that the BJT does not use a dedicated transistor material system independent of silicon photonics processes, but instead reuses the silicon doped layers and metal layers required for waveguide modulators, heaters, and detector contacts, thereby reducing or eliminating the need for dedicated transistor masks and additional process steps. Monolithic interconnects allow the distance from the detector to the first bipolar junction transistor reference node and the second bipolar junction transistor output to the optical nonlinear device driver to be shortened to the on-chip local interconnect scale, reducing pads, wire bonding, and packaging parasites. Please refer to [link to relevant documentation]. Figure 5 , Figure 5 This is a schematic diagram illustrating the monolithic fabrication and metal interconnection of a microring, a BJT, and a detector according to an embodiment of the present invention. Figure 5 As shown, the structural types of optoelectronic nonlinear activation devices include silicon waveguide etching, silicon doping, silicon epitaxy and silicon doping, and metal interconnection; Si represents silicon material, P++ represents P-type heavily doped region, N++ represents N-type heavily doped region, Ge represents germanium material, GeN+ represents N-type doped germanium region, SiO2 represents silicon dioxide insulating layer, and Al represents aluminum metal interconnection layer.

[0037] In some embodiments, such as this one, the workflow of the photoelectric nonlinear activation device is described below for ease of understanding: S1. Control light or input light enters the device via an input optical coupler or on-chip waveguide; S2. The photodetector receives all the control light or the input light with a splitting ratio α, and outputs a photocurrent; S3. The first bipolar junction transistor reference branch connected to the photocurrent input diode establishes a common base-emitter voltage; S4. The second bipolar junction transistor outputs amplified current based on the effective emitter-junction area ratio or the number of parallel units; S5. The optional bias current and amplification current are summed at the current node to obtain the drive current; S6. The driving current is directly input to the current driving terminal of the optical nonlinear device, causing changes in its resonant wavelength, phase, absorption coefficient, coupling state, or transmittance; S7. The modulated light is output from the output terminal after being modulated by an optical nonlinear device; when using an Add-Drop type microring resonator, it is output from the through terminal or the download terminal. S8. The nonlinear curve is calibrated and adjusted by adjusting the mirror gain M, splitting ratio α, bias current, input wavelength and output port.

[0038] In some embodiments, such as this one, a photoelectric nonlinear activation chip is also provided. This chip includes multiple photoelectric nonlinear activation devices based on monolithically integrated BJT current mirrors, as described above. These devices are arranged along one or more waveguide arrays to form a wavelength division multiplexing parallel nonlinear activation array. Each wavelength channel is configured with an independent nonlinear activation unit, or multiple photodetectors jointly drive an optical nonlinear device through current summation nodes. It should be noted that when the optical nonlinear device is an Add-Drop type microring resonator, its wavelength selectivity can be used to construct a wavelength division multiplexing parallel activation array. When using a Mach-Zehnder interferometer, an electroabsorption modulator, or other optical nonlinear devices, it can also be combined with a wavelength division multiplexer, demultiplexer, or switching matrix to form a multi-channel parallel structure. Furthermore, the photoelectric nonlinear activation device and chip in this embodiment can be used in optical neural networks, photonic convolution processors, reservoir computing, optical analog-to-digital conversion, optical threshold decision, optical power compression, wavelength-locked front-ends, on-chip sensor readout, and adaptive optics control. For non-neural network applications, a nonlinear photoelectric conversion with settable thresholds and gains can still be formed between the input control light and the output light.

[0039] In some embodiments, such as this one, it should be noted that the following substitutions and modifications can be made without departing from the core idea of ​​direct current mirror driving in this embodiment.

[0040] Transistor type replacement: The NPN type of the first bipolar junction transistor and the second bipolar junction transistor can be replaced with the PNP type; the silicon-based bipolar junction transistor can be replaced with the SiGe heterojunction bipolar transistor or other bipolar devices; a composite bipolar junction transistor, Darlington structure or phototransistor reference branch can be used.

[0041] Current mirror structure replacement: The BJT current mirror can be replaced with a Wilson current mirror, cascaded current mirror, β-compensated current mirror, multi-output current mirror, programmable segmented current mirror, complementary current mirror, or mirror structure with current limiting.

[0042] Photodetector type replacement: Vertical PIN photodetectors can be replaced with horizontal PIN photodetectors, avalanche photodiodes, silicon / germanium heterogeneous photodetectors, graphene or two-dimensional material photodetectors, and phototransistors.

[0043] Replacement of optical nonlinear devices: Add-Drop type microring resonators can be replaced with All-Pass type microring resonators, microdisk resonators, Mach-Zehnder interferometers, Bragg resonators, photonic crystal cavities, electro-absorption modulators, thermo-optical phase shifters, or variable optical attenuators.

[0044] Driving mechanism replacement: Carrier injection, carrier depletion, thermo-optical tuning, electro-absorption, phase change material tuning, or electromechanical tuning can be used individually or in combination.

[0045] Optical path configuration replacement: Independent control light and modulated light can be used, or the same input light can be split and self-feedback can be used; single wavelength, wavelength division multiplexing, multimode multiplexing or polarization multiplexing can be used.

[0046] Substrate material replacement: SOI substrates can be replaced with silicon nitride / silicon hybrid integrated substrates, SiGe substrates, InP substrates, thin-film lithium niobate and silicon electronic hybrid substrates, as long as photodetectors, BJT current mirrors and optical nonlinear devices can be monolithically or tightly heterogeneously integrated on the same substrate.

[0047] Bias mode replacement: The bias current can be provided by an on-chip current source, resistor, digital-to-analog converter, third bipolar junction transistor branch or external current source; or it can be set by simply relying on the detuning of the operating wavelength without additional bias current.

[0048] In some embodiments, such as this one, experiments have demonstrated that the microring exhibits a significant resonant response near 1545.6 nm. After setting the probe wavelength near the resonant position, the input optical power is converted by a vertical PIN photodetector with a responsivity of 0.97 A / W and amplified by a bipolar junction transistor current mirror, which drives a change in the resonant state of the microring. The measured output optical power shows a significant nonlinear growth relationship with the input optical power, exhibiting a low-input hold region, a fast response region, and a high-input asymptotic region, verifying that the monolithic optoelectronic fusion structure in this embodiment can achieve nonlinear activation functions suitable for optical neural networks. Please refer to [link to relevant documentation]. Figure 6 , Figure 6 The two-port spectrum and nonlinear activation performance test diagram of an Add-Drop type microring resonator provided in an embodiment of the present invention are shown below. Figure 6 (a) shows the power transfer curves of the through end and the download end, with the fixed probe wavelength selected around 1545.6 nm; (b) shows the measured curves of the output optical power of the through end and the download end when the input control optical power changes; (c) shows that the input and output power are first converted from dBm to linear power, and then normalized to 0 to 1 according to the minimum and maximum values ​​of their respective test intervals.

[0049] To facilitate understanding, several specific implementation methods of optoelectronic nonlinear activation devices based on monolithically integrated BJT current mirrors are described below: 1. Nonlinear activation device for independent control of light and modulated light This embodiment includes a control light input terminal, a photodetector, a BJT current mirror, an add-drop microring resonator, a modulated light input terminal, and an output terminal. The photodetector, BJT current mirror, and optical nonlinear devices are integrated on the same SOI substrate and connected by on-chip metal interconnects.

[0050] The photodetector is a silicon / germanium vertical PIN photodetector with a measured responsivity of 0.97 A / W near 1545.6 nm. The output of the photodetector is connected to the reference branch of the BJT current mirror.

[0051] The BJT current mirror includes a first bipolar junction transistor (BJT) Q1 and a second BJT Q2. The collector and base of the first BJT are connected to form a reference branch. The base of the first BJT is connected to the base of the second BJT. The emitters of both the first and second BJTs are connected to a common low-potential terminal. The collector of the second BJT serves as the current output terminal and is connected to the current drive terminal of a micro-ring resonator. By increasing the effective emitter junction area of ​​the second BJT or by connecting multiple second BJT units in parallel, the current mirror gain is made greater than 1. Its output current I... M It can be represented as: I M = G I × I PD Among them, I PD G outputs photocurrent for the photodetector. I This represents the actual current gain.

[0052] The optical nonlinear device employs an Add-Drop type microring resonator, comprising an input bus waveguide, a download bus waveguide, and a ring waveguide located between the input and download bus waveguides. The microring radius is 40 μm, the waveguide width is 500 nm, and the coupling spacings between the ring waveguide and the two bus waveguides are 150 nm and 250 nm, respectively. The microring resonant wavelength is approximately 1545.6 nm, the free spectral range is 3.4 nm, and the quality factor is 2630.

[0053] During testing, the control light is input to the photodetector, and the resulting photocurrent is amplified by the BJT current mirror to form a driving current that directly drives the microring (microring is short for Add-Drop type microring resonator); another beam of modulated light enters the microring, and the wavelength of the modulated light is fixed at the resonant dip position near 1545.6 nm, and the output nonlinear optical power is read from the through end or download end.

[0054] The output optical power of the microring resonator can be expressed as: P OUT = P PROBE × T[λ probe , λ res (I M )] To verify the nonlinear activation performance of the device, the transmission spectra of the through-end and download-end of the microring were first tested. The microring exhibited a significant resonant response near 1545.6 nm, with the through-end forming a transmission dip of approximately -17 dB at the resonant position, and the download-end forming an output peak of approximately -8 dB near the same wavelength. The two output ends showed complementary spectral responses. During testing, the wavelength of the modulated light was fixed near the resonant position.

[0055] Subsequently, keeping the modulated light wavelength and input power constant, the control light power input to the photodetector is changed. The photocurrent generated by the photodetector is amplified by the BJT current mirror and directly drives the microring resonator, causing the microring resonant state to change with the control light power. When the control light input power increases from approximately -40 dBm to approximately -3 dBm, the output light power at the through end increases from approximately -25 dBm to approximately -8 dBm, a variation range of approximately 17 dB; simultaneously, the output light power at the download end decreases from approximately -15.5 dBm to approximately -21 dBm.

[0056] The through-port output exhibits a low-input hold region, a rapidly changing intermediate region, and a high-input asymptotic region, forming a rising-type saturated nonlinear response. The download end, on the other hand, exhibits a complementary nonlinear response that decreases with increasing input optical power. After converting the output power of both ports to the linear power domain and normalizing them, the normalized output of the through-port gradually approaches 1 from 0, while the normalized output of the download end gradually approaches 0 from 1. This indicates that the photoelectric nonlinear activation device can simultaneously provide a pair of complementary nonlinear activation outputs.

[0057] The two-port outputs can be used as rising and falling activation functions respectively, or they can be differentially, summed, or weighted to construct bipolar activation, differential activation, or positive and negative weighted encoding. Therefore, the micro-ring can not only provide single-ended nonlinear output, but also achieve complementary or differential nonlinear processing using the pass-through and download ends.

[0058] 2. Self-activating device for splitting the same input light This embodiment includes an input optical terminal, a beam splitter coupler, a photodetector, a BJT current mirror, an Add-Drop microring resonator, and an output optical terminal.

[0059] After the input light to be activated enters the directional coupler or multimode interference coupler, it is split into two paths. The light with a ratio of α enters the photodetector as the first ratio light, and the light with a ratio of 1-α enters the microring resonator as the second ratio light.

[0060] The photocurrent generated by the photodetector is: I PD = R PD × α × P IN + Idark After being amplified by the BJT current mirror, the driving current of the micro-ring resonator is: I DRV = I BIAS + G I × I PD By setting the effective emitter junction area ratio or the number of parallel units, the actual current gain G, considering the finite current amplification factor and the base current, can be increased. I Greater than 1.

[0061] The output power of the micro-ring is: P OUT = (1-α) × P IN × T[λ0, λ res ( IDRV )] Since the input light simultaneously determines the optical power entering the microring resonator and the driving current driving the microring resonator, a nonlinear relationship is formed between the output optical power and the input optical power.

[0062] By changing the splitting ratio α, the current mirror gain, the microring operating wavelength, and the bias current, the threshold, slope, and output range of the nonlinear curve can be adjusted. This embodiment does not require independent control of the light source and is suitable for use as an interstage activation unit in a multi-level optical neural network.

[0063] 3. Multiplexed Parallel Nonlinear Activation Array This embodiment provides a photoelectric nonlinear activation chip, which includes multiple photoelectric nonlinear activation units arranged in parallel. Each photoelectric nonlinear activation unit includes a photodetector, a BJT current mirror, and an Add-Drop type microring resonator, and is integrated on the same SOI substrate.

[0064] The input multiplexed light includes multiple wavelength channels: λ1, λ2, …, λN The resonant wavelength of each microring is set near the corresponding wavelength channel, used for selection and modulation of that channel. The photodetector in each channel generates a photocurrent, which is amplified by the corresponding BJT current mirror and then directly drives the microring.

[0065] The output optical power of the i-th channel can be expressed as: P OUT,i = P IN,i × T i [λ i , λ res,i (I BIAS,i + G I,i × I PD,i )] By setting the current gain, bias current, and initial detuning of each channel, the differences in photodetector responsivity, waveguide loss, and microring performance can be compensated.

[0066] Multiple channels can share power, ground, and bias buses. Since each channel uses a current mirror composed of a small number of bipolar junction transistors, there is no need for a separate transimpedance amplifier and its feedback network, which is beneficial for improving the integration density of wavelength division multiplexing optical neural networks.

[0067] Multiple optoelectronic nonlinear activation devices are arranged along one or more waveguide arrays to form a wavelength division multiplexing parallel nonlinear activation array; wherein each wavelength channel is configured with an independent nonlinear activation unit, or multiple photodetectors jointly drive an optical nonlinear device through a current summing node.

[0068] 4. Other implementation methods In other embodiments, the Add-Drop type microring resonator in the above embodiments can be replaced with other optical nonlinear devices. For example, when using a Mach-Zehnder interferometer, the output current of the BJT current mirror is directly input into its carrier injection phase shifter or thermo-optical phase shifter, and a nonlinear output is formed by changing the phase difference between the two interference arms; when using an electro-absorption modulator, the amplified current is directly input into its absorption modulation region, and a nonlinear output is formed by changing the absorption coefficient; when using a microdisk resonator, Bragg resonator, or photonic crystal cavity, the amplified current changes its resonance state and forms a nonlinear transmission or reflection response at a fixed operating wavelength. In the above structure, no transimpedance amplifier or operational amplifier-type current-to-voltage conversion stage is set between the current output terminal of the BJT current mirror and the current drive terminal of the optical nonlinear device, realizing direct transmission in the current domain.

[0069] In summary, the photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror provided in this embodiment directly drives the optical nonlinear device using the BJT current mirror. This eliminates the need for transimpedance amplifiers or operational amplifier-type current-to-voltage conversion stages, thus removing complex feedback networks and compensation circuits, significantly simplifying the device structure and reducing design and manufacturing complexity. The BJT current mirror itself is a passive current amplification structure, requiring no additional power supply circuits or bias networks. Direct current domain transmission avoids multiple current-to-voltage-to-current conversion losses, which is beneficial for large-scale integrated applications. The photodetector, BJT current mirror, and optical nonlinear device are integrated on the same substrate, with on-chip metal interconnects for electrical connection. The distance from the photodetector to the current mirror reference node and from the current mirror output to the optical nonlinear device driving end can be shortened to the scale of on-chip local interconnects, reducing pads, wire bonding, and packaging parasites, and improving response speed and signal integrity. The BJT current mirror can reuse standard CMOS and SOI... The doped and metal layers in CMOS, BiCMOS, or silicon photonics processes do not require additional dedicated transistor masks or process steps, ensuring compatibility with existing semiconductor processes and facilitating mass production and cost control. The image gain (greater than 1) can be flexibly set by adjusting the effective emitter junction area ratio or the number of parallel units of the first and second bipolar junction transistors. Combined with parameters such as bias current, splitting ratio, probe wavelength, output port, coupling distance, and quality factor, the activation threshold, slope, dynamic range, and saturation region can be precisely calibrated and adjusted. The optocoupler supports independent control of the optical mode and self-activated splitting mode. The device offers two operating modes to adapt to different application scenarios. Various types of optical nonlinear devices can be selected, including microring resonators, Mach-Zehnder interferometers, and electroabsorption modulators, providing excellent versatility and scalability. When using an Add-Drop type microring resonator, the through-end and download end can simultaneously provide a pair of complementary nonlinear activation outputs, which can be used as rising and falling activation functions respectively. Differential, summation, or weighted combinations can also be performed to construct bipolar activation, differential activation, or positive and negative weighted encoding, enhancing signal processing capabilities. The optoelectronic nonlinear activation chip is beneficial for improving the integration density and parallel processing capabilities of optical neural networks.

[0070] The present invention has been described above in conjunction with the preferred embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations made in accordance with the essence of the present invention.

Claims

1. A photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror, characterized in that, include: Photodetectors are used to receive control light and generate photocurrent. The BJT current mirror includes a first bipolar junction transistor and a second bipolar junction transistor. The collector and base of the first bipolar junction transistor are connected to form a reference branch. The output terminal of the photodetector is connected to the reference branch so that the BJT current mirror amplifies the photocurrent to form a driving current. The collector of the second bipolar junction transistor serves as a current output terminal to output the driving current. An optical nonlinear device having a current driving terminal directly connected to a current output terminal, the optical nonlinear device being used to receive modulated light and output nonlinear optical power under the modulation of the driving current; The photodetector, the BJT current mirror, and the optical nonlinear device are integrated on the same substrate.

2. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 1, characterized in that, The driving current is the current formed after the photocurrent is amplified by the BJT current mirror with a mirror gain greater than a preset gain value. The mirror gain is set by the effective emitter junction area ratio or the number of parallel units of the first bipolar junction transistor and the second bipolar junction transistor.

3. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 1, characterized in that, The first bipolar junction transistor and the second bipolar junction transistor are selected from any of the following combinations: both are lateral bipolar junction transistors, both are vertical bipolar junction transistors, one of which is a lateral bipolar junction transistor and the other is a vertical bipolar junction transistor.

4. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 3, characterized in that, The emitter region, base region, and collector region of the vertical bipolar junction transistor are arranged sequentially along the thickness direction of the substrate, and the emitter region, the base region, and the collector region are formed using doped regions and contact structures in standard semiconductor processes.

5. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 1, characterized in that, The optical nonlinear device is any one of the following: microring resonator, microdisk resonator, Mach-Zehnder interferometer, electroabsorption modulator, Bragg resonator, photonic crystal cavity, thermo-optical phase shifter, and variable optical attenuator.

6. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 5, characterized in that, The micro-ring resonator is an Add-Drop type micro-ring resonator, which includes an input bus waveguide, a download bus waveguide, and a ring waveguide located between the input bus waveguide and the download bus waveguide. The modulated light is input from the input bus waveguide, and after resonance in the ring waveguide, the nonlinear optical power is output from the download end or from the through end via the download bus waveguide.

7. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 1, characterized in that, It also includes an optical coupler, which is an input coupler and / or a beam splitter; wherein the input coupler is a grating coupler or an edge coupler, used to couple the input light into the on-chip waveguide; the beam splitter is a directional coupler or a multimode interference coupler, used to split the input light into a first proportion of light and a second proportion of light, wherein the first proportion of light is used as the control light input to the photodetector, and the second proportion of light is used as the modulated light input to the optical nonlinear device.

8. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 1, characterized in that, The control light is an external light source independent of the modulated light, and the control light and the modulated light have at least one of different wavelengths, powers, or codes.

9. The photoelectric nonlinear activation device based on a monolithically integrated BJT current mirror as described in claim 1, characterized in that, The photodetector, the BJT current mirror, and the optical nonlinear device are arranged adjacent to each other on the same substrate, with at least one of optical isolation trenches, a metal shielding layer, and a thermal isolation structure disposed therebetween.

10. A photoelectric nonlinear activation chip, characterized in that, The invention includes multiple photoelectric nonlinear activation devices based on monolithically integrated BJT current mirrors as described in any one of claims 1 to 9, wherein the multiple photoelectric nonlinear activation devices are arranged along one or more waveguide arrays to form a wavelength division multiplexing parallel nonlinear activation array; wherein each wavelength channel is configured with an independent nonlinear activation unit, or multiple photodetectors jointly drive an optical nonlinear device through a current summing node.

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