Resonant modulators, optical computing systems and photonic integrated systems

Abstract

This application provides a resonant modulator applicable to the field of optoelectronic information technology. The resonant modulator includes a substrate layer, a buried layer, a core layer, and an upper cladding layer. The core layer includes a multimode interference coupler and a connecting waveguide. The multimode interference coupler includes a multimode interference region and a main input port waveguide, a main output port waveguide, a feedback output port waveguide, and a feedback input port waveguide. The two ends of the connecting waveguide are optically connected to the feedback output port waveguide and the feedback input port waveguide, forming an optical feedback loop with the multimode interference coupler. An electro-optic modulation unit is associated with a first region of the connecting waveguide and is used to adjust the effective refractive index of the connecting waveguide by applying an electrical signal to change the resonant state of the resonant modulator. Based on the above structure, the sensitivity to coupling spacing and manufacturing errors can be reduced, and the device operating tolerance and modulation stability can be improved. This application also provides an optical computing system and a photonic integrated system.

Description

Technical Field

[0001] This application relates to the field of optoelectronic information technology, specifically to a resonant modulator, an optical computing system, and a photonic integrated system. Background Technology

[0002] With the rapid development of artificial intelligence applications and the continuous growth of data scale, the demand for communication bandwidth and computing power efficiency is constantly increasing, and traditional electronic architectures are gradually facing bottlenecks in bandwidth and power consumption. Photonic integrated circuits, due to their advantages such as high bandwidth, low power consumption, miniaturization, scalable manufacturing, and compatibility with existing processes, have become an important technological direction for realizing high-speed on-chip interconnection and high-efficiency computing. Among them, micro-ring modulators are widely used due to their small size and good wavelength division multiplexing performance. Existing micro-ring modulators mostly adopt an evanescent field coupling structure between a bus waveguide and a micro-ring. Their coupling strength is highly sensitive to the waveguide gap; even small dimensional deviations during manufacturing can cause the coupling state to deviate from the design target, leading to a decrease in signal extinction ratio or distortion of the resonant waveform. Limited by the thermo-optical effect of the materials themselves, the resonant wavelength of micro-ring modulators is extremely sensitive to changes in ambient temperature. Temperature disturbances can cause the resonant wavelength to drift, thereby disrupting the ideal operating state of the device and affecting its reliability and stability. Therefore, there is an urgent need for an optical modulator structure and control method that can reduce the impact of manufacturing errors and possess good thermal stability. Summary of the Invention

[0003] In view of the above problems, this application provides a resonant modulator, an optical computing system, and a photonic integrated system.

[0004] According to a first aspect of this application, a resonant modulator is provided, comprising: a substrate layer; a buried layer disposed on the substrate layer; a core layer formed on the buried layer; and an upper cladding layer covering at least a portion of the surface of the core layer; wherein the core layer comprises: a multimode interference coupler and a connecting waveguide; the multimode interference coupler includes a multimode interference region and four port waveguides, wherein the multimode interference region includes an input side and an output side; wherein the four port waveguides are divided into: a main input port waveguide and a feedback input port waveguide optically connected to the input side of the multimode interference region through their respective output ends; and a main output port waveguide and a feedback output port waveguide optically connected to the output side of the multimode interference region through their respective input ends; the two ends of the connecting waveguide are optically connected to the output end of the feedback output port waveguide and the input end of the feedback input port waveguide, respectively, such that the connecting waveguide and the multimode interference coupler together form a closed optical feedback loop; and an electro-optic modulation unit, which is associated with a first region along the length direction of the connecting waveguide, for adjusting the effective refractive index of the connecting waveguide by applying an electrical signal to change the resonant state of the resonant modulator.

[0005] According to an embodiment of this application, the resonant modulator further includes a thermal phase shifter, which is associated with a second region of the connecting waveguide along its length and is thermally coupled to the connecting waveguide for adjusting the effective refractive index of the connecting waveguide through a thermo-optical effect.

[0006] According to an embodiment of this application, the thermal phase shifter includes a resistance heating structure and a thermal phase shifter electrode. The resistance heating structure is disposed in the upper cladding, and the thermal phase shifter electrode is electrically connected to the resistance heating structure.

[0007] According to an embodiment of this application, the port waveguide is a tapered waveguide, wherein the dimension of the end of the port waveguide connected to the multimode interference region is larger than the dimension of the end away from the multimode interference region.

[0008] According to an embodiment of this application, the core layer is made of silicon material; the electro-optic modulation unit includes a modulation electrode and a doped region formed based on a connecting waveguide, the doped region including a P-type doped region and an N-type doped region, the P-type doped region and the N-type doped region being used to form a PN junction or a PIN junction; the modulation electrode is electrically connected to the doped region and is used to apply a modulation signal to the PN junction or PIN junction.

[0009] According to embodiments of this application, the core layer is composed of lithium niobate or lithium tantalate.

[0010] According to an embodiment of this application, the electro-optic modulation unit includes a modulation electrode disposed on the surface or inside the upper cladding and forming an electric field coupling with the connecting waveguide, for applying an external electric field in a first region to adjust the effective refractive index of the connecting waveguide through an electro-optic effect.

[0011] According to an embodiment of this application, the resonant modulator further includes an input waveguide and an output waveguide, wherein the input waveguide is optically connected to the input end of the main input port waveguide, and the output waveguide is optically connected to the output end of the main output port waveguide.

[0012] According to embodiments of this application, the P-type doped region includes a P-doped region, a P+ doped region, and a P++ doped region, and the N-type doped region includes an N-doped region, an N+ doped region, and an N++ doped region.

[0013] According to embodiments of this application, the substrate layer is made of silicon material, and the buried layer and the upper cladding layer are made of silicon dioxide material.

[0014] A second aspect of this application provides an optical computing system, comprising: a laser source; a first resonant modulator and a second resonant modulator, both of which are the aforementioned resonant modulators, wherein the first resonant modulator is configured as a data loading node and the second resonant modulator is configured as a weight loading node; wherein the output end of the laser source is optically connected to the input end of the main input port waveguide of the first resonant modulator, and the output end of the main output port waveguide of the first resonant modulator is optically connected to the input end of the main input port waveguide of the second resonant modulator.

[0015] A third aspect of this application provides a photonic integrated system, comprising: a plurality of the aforementioned resonant modulators; wherein the plurality of resonant modulators are optically connected to each other to form one of the following topologies or any combination thereof: series connection, parallel connection, two-dimensional matrix network connection, nested recursive connection.

[0016] The embodiments provided in this application construct a closed optical feedback loop by using a multimode interference coupler and a connecting waveguide. This allows the optical signal to propagate cyclically within the loop and generate a resonance effect. This addresses the issue of the high sensitivity of the coupling spacing to evanescent wave-coupled microring resonators in terms of structural design, enhances the robustness of the device to manufacturing errors, and facilitates obtaining a more stable coupling ratio and output characteristics. Simultaneously, an electro-optic modulation unit is set on the connecting waveguide. By applying an electrical signal to adjust the effective refractive index of the connecting waveguide, the resonance state of the resonant modulator is changed, achieving efficient dynamic control of the optical signal. Attached Figure Description

[0017] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of a multimode interference coupler structure according to an embodiment of this application is shown.

[0019] Figure 2 A schematic diagram illustrating the waveguide connection configuration of a multimode interference coupler according to an embodiment of this application is shown.

[0020] Figure 3 A schematic top view of a resonant modulator according to a first embodiment of this application is shown;

[0021] Figure 4 A schematic cross-sectional view of a resonant modulator according to a first embodiment of this application is shown.

[0022] Figure 5 A second schematic cross-sectional view of a resonant modulator according to the first embodiment of this application is shown.

[0023] Figure 6A schematic top view of a resonant modulator according to a second embodiment of this application is shown;

[0024] Figure 7 A schematic diagram illustrating the electric field intensity distribution of a multimode interference coupler according to an embodiment of this application is shown.

[0025] Figure 8 The transmittance simulation curve of a multimode interference coupler according to an embodiment of this application is schematically shown;

[0026] Figure 9 The transmission loss simulation curve of the resonant modulator according to an embodiment of this application is illustrated schematically;

[0027] Figure 10 The diagram schematically illustrates a simulation comparison of the normalized full width at half maximum (FWHM) and quality factor of a resonant modulator according to an embodiment of this application and a conventional directionally coupled micro-ring modulator.

[0028] Figure 11 A schematic diagram of an optical computing system structure constructed using a resonant modulator according to an embodiment of this application is shown.

[0029] Figure 12 A schematic diagram of a photonic integrated system structure constructed using a resonant modulator according to an embodiment of this application is shown. Figure 12 (a) shows the series connection method. Figure 12 (b) shows the parallel connection method. Figure 12 (c) shows the connection method of the two-dimensional matrix network. Figure 12 (d) and (e) in the diagram illustrate the connection methods of hierarchical nesting and combined expansion.

[0030] The meanings of the reference numerals in the above figures are as follows:

[0031] 1: Multimode interference region;

[0032] 2: Feedback input port waveguide;

[0033] 3: Main input port waveguide;

[0034] 4: Feedback output port waveguide;

[0035] 5: Main output port waveguide;

[0036] 6: Connect the waveguide;

[0037] 7: Electro-optic modulation unit;

[0038] 8: Thermal phase shifter;

[0039] 9: Input waveguide;

[0040] 10: Output waveguide;

[0041] 11: Substrate layer;

[0042] 12: Buried layer;

[0043] 13: Upper cladding;

[0044] 71: Modulation electrode;

[0045] 72: P++ doped region;

[0046] 73: P+ doped region;

[0047] 74: P-doped region;

[0048] 75: N-doped region;

[0049] 76: N+ doped region;

[0050] 77: N++ doped region;

[0051] 81: Resistance heating structure;

[0052] 82: Heat-shifting phase electrode. Detailed Implementation

[0053] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0054] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0055] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0056] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0057] Figure 1 A schematic diagram of a multimode interference coupler structure according to an embodiment of this application is shown.

[0058] like Figure 1 As shown, the 2×2 multimode interferometer (MMI) coupler in the figure includes a multimode interferometer region and four port waveguides connected to this region. Wherein, E i1 and E i2 For two input ports, E o1 and E o2 For two output ports, W M L represents the width of the multimode interference region. N This indicates the length of the multimode interference region. Multimode interference couplers operate based on the self-imaging principle, achieving on-demand power distribution at the output port by exciting interference effects of multiple modes in the multimode waveguide region. Compared to traditional directional or point-coupled structures, multimode interference couplers do not require submicron-level critical coupling gaps, exhibit higher robustness to nanoscale manufacturing errors, maintain precise power distribution ratios over a wider spectral range (such as the C-band), and their power distribution characteristics are relatively insensitive to temperature fluctuations.

[0059] Figure 2 A schematic diagram of the waveguide connection configuration of a multimode interference coupler according to an embodiment of this application is shown.

[0060] like Figure 2 As shown, Figure 1 The 2×2 multimode interference coupler shown is connected to one output port E. o2 The port waveguide is connected to the input port E at a symmetrical position. i2 The port waveguides are connected via connecting waveguides to form a closed optical feedback loop. The optical signal is input from the other side, port E. i1 The light enters and passes through the corresponding port waveguide into the multimode interference region. Within the multimode interference region, the optical field is distributed to each output port: a portion of the light exits from the corresponding output port E. o1 The output is another portion of the light, which comes from the output port E. o2 It enters the connecting waveguide through its port waveguide, and is fed back to the input port E through the connecting waveguide. i2The light wave enters the multimode interference region again and interferes with the input light. The light wave propagates cyclically within this ring path, creating a resonant effect similar to a micro-ring resonator, ultimately reaching the output port E. o1 It exhibits a wavelength-selective transmission spectrum. This feedback structure based on a multimode interference coupler retains the wavelength selectivity of the microring resonator while reducing the problem of high sensitivity to fine coupling spacing, thereby improving the manufacturing tolerance and stability of the device.

[0061] Figure 3 A schematic top view of a resonant modulator according to a first embodiment of this application is shown.

[0062] It should be noted that, Figure 3 Primarily used to demonstrate the planar layout of the core waveguide structure. In reality, components such as the thermal phase shifter 8 and the modulation electrode 71 of the electro-optic modulation unit 7 are typically located in or on the surface of the upper cladding above the core waveguide. To facilitate a visual illustration of the relative positions of these upper components to the underlying core waveguide on the plane, Figure 3 They are shown together in a perspective overlay manner. This illustration does not indicate that the above components are on the same physical level as the core waveguide structure.

[0063] also, Figure 3 Lines AA′ and BB′ are cutting lines, used to indicate... Figure 4 and Figure 5 The section position. This section line is only used to illustrate the relative relationship between the section plane and the core waveguide.

[0064] Figure 4 One of the schematic cross-sectional structural diagrams of a resonant modulator according to a first embodiment of this application is shown.

[0065] Figure 5 The diagram illustrates a second cross-sectional view of a resonant modulator according to the first embodiment of this application.

[0066] like Figures 3-5 As shown, embodiments of this application relate to an MMI-based resonant modulator (MMI-RM). The core optical path structure of the resonant modulator is located in the core layer, mainly including the MMI-RM and the connecting waveguide 6. Combined with... Figure 3As shown in the planar layout, the multimode interferometric coupler includes a central multimode interferometric region 1 and four port waveguides connected to it. The multimode interferometric region 1 has an input side and an output side. The four port waveguides are divided into: a feedback input port waveguide 2 and a main input port waveguide 3, which are optically connected to the input side of the multimode interferometric region 1 through their respective output ends; and a feedback output port waveguide 4 and a main output port waveguide 5, which are optically connected to the output side of the multimode interferometric region 1 through their respective input ends.

[0067] In the embodiments of this application, the two ends of the connecting waveguide 6 are respectively connected to the output end of the feedback output port waveguide 4 (i.e., the end furthest from the multimode interference region 1) and the input end of the feedback input port waveguide 2 (i.e., the end furthest from the multimode interference region 1). This end-to-end routing method allows the connecting waveguide 6 and the multimode interference coupler to form a closed optical feedback loop. In this structure, the two ends of the connecting waveguide 6 are optically connected to the feedback output port waveguide 4 and the feedback input port waveguide 2, respectively, and evanescent field coupling does not rely on the preset coupling gap between adjacent waveguides.

[0068] In the embodiments of this application, based on the aforementioned closed loop, the resonant modulator is configured with independent functional units for optical signal modulation, namely, an electro-optic modulation unit 7 and a thermal phase shifter 8. This design, which integrates both the thermal phase shifter and the electro-optic modulation unit in the structure, employs a dual control mechanism of "thermo-optic + electro-optic" synergy. The thermal phase shifter is used for low-speed thermal tuning and bias point locking, while the electro-optic modulation unit is used to load a high-speed electrical signal to achieve high-speed modulation of the output optical signal. Specifically, the electro-optic modulation unit 7 is associated with a first region along the length of the connecting waveguide 6, and is used to adjust the effective refractive index of the connecting waveguide by applying an electrical signal to change the resonant state of the resonant modulator. The thermal phase shifter 8 is associated with a second region along the length of the connecting waveguide 6 and forms thermal coupling with the connecting waveguide, and is used to adjust the effective refractive index of the connecting waveguide 6 through the thermo-optic effect to adjust and stabilize the device's operating point. In the embodiments of this application, "associated setting" means that the corresponding functional unit is set in a manner that allows it to act on the corresponding region of the connecting waveguide 6 and adjust the effective refractive index of that corresponding region. It should be noted that the first region and the second region are different regions distributed along the length of the connecting waveguide 6, and the specific location of the second region can be flexibly determined according to actual needs. For example, it can be located between the first region and the feedback output port waveguide 4, or between the first region and the feedback input port waveguide 2. Furthermore, the thermal phase shifter 8 includes a resistive heating structure 81 and a thermal phase shifter electrode 82, which are electrically connected. The resistive heating structure 81 is spaced apart from and adjacent to the connecting waveguide, thus forming thermal coupling with the connecting waveguide 6. Based on the above structural configuration, the thermal phase shifter 8 can achieve stable control of the device's operating point, and the electro-optic modulation unit 7 can achieve high-speed dynamic modulation near this operating point, thereby balancing operating point stability and high-speed modulation performance.

[0069] In embodiments of this application, the resonant modulator comprises, from bottom to top: a substrate layer 11; a buried layer 12 disposed on the substrate layer; the aforementioned core layer formed on the buried layer 12; and an upper cladding layer 13 covering at least a portion of the surface of the core layer. In embodiments of this application, the substrate layer 11 is made of silicon (Si) material, and the buried layer 12 (i.e., buried oxide layer, BOX) and the upper cladding layer 13 are made of silicon dioxide (SiO2) material. The low-refractive-index silicon dioxide not only provides good optical isolation and protection, but also provides space for the resistive heating structure 81 of the aforementioned thermal phase shifter 8. In addition, the resonant modulator also includes an input waveguide 9 and an output waveguide 10, the input waveguide 9 being optically connected to the input end of the main input port waveguide 3, and the output waveguide 10 being optically connected to the output end of the main output port waveguide 5.

[0070] To further optimize the optical performance of the device, all four port waveguides are configured as tapered waveguides. That is, the dimension of the end of the port waveguide connected to multimode interference region 1 is larger than the dimension of the end farther from multimode interference region 1. The tapered waveguide is used to achieve mode field matching between the port waveguide and the multimode interference region. Since the width of the multimode interference region is typically much larger than the width of the single-mode waveguide, direct connection could lead to mode mismatch and significant transmission loss. By adopting a tapered structure, the port waveguide has a larger lateral width at the output end connected to the multimode interference region and a smaller lateral width at the input end farther from the multimode interference region. This allows for a smooth transition from the single-mode waveguide to the multimode interference region, reducing mode conversion loss and improving the overall transmission efficiency of the device.

[0071] In the overall working mechanism, the fundamental mode light from the optical input end a enters the input waveguide 9 through fiber-to-chip coupling, is transmitted to the main input port waveguide 3, and coupled into the multimode interference region 1. Within the multimode interference region 1, the optical field is distributed: a portion of the light is transmitted through the main output port waveguide 5 to the output waveguide 10, and finally output to the optical receiver end b; the other portion of the light enters the connecting waveguide 6 and propagates cyclically along the feedback loop, thus forming a wavelength-selective output response. During operation, the thermal phase shifter 8 changes the effective refractive index of the waveguide through the Joule heating effect and, combined with feedback control, thermally tunes the resonant spectrum of the device to adjust the device's operating point to a preset bias position, thereby providing suitable operating conditions for subsequent high-speed electro-optic modulation. The electro-optic modulation unit 7 is used to load a high-speed electrical signal near this operating point, dynamically modulating the resonant state of the multimode interference coupler-based resonant modulator by rapidly changing the effective refractive index of the waveguide, thereby achieving high-speed modulation of the optical carrier by the data signal.

[0072] It should be noted that the propagation characteristics of an optical signal in a waveguide are related to the effective refractive index of the waveguide. When the effective refractive index of waveguide 6 changes, the phase accumulated by the optical signal during its propagation through the closed optical feedback loop formed by the multimode interference coupler and waveguide 6 also changes. Since the resonance condition of the closed optical feedback loop is related to phase accumulation, when the effective refractive index of waveguide 6 changes, leading to a change in phase accumulation, the resonance condition of the closed optical feedback loop also changes, thereby changing the output response corresponding to a fixed operating wavelength, which manifests as a change in output light intensity.

[0073] From the perspective of the device's external response, the resonant modulator can be said to have a transmission spectrum. The transmission spectrum characterizes the relationship between the input light wavelength and the output light intensity via the resonant modulator; that is, it is the transmission curve formed by the change in output light intensity with the input light wavelength. When the resonance condition of the closed optical feedback loop changes, the position of the wavelength satisfying the resonance condition changes accordingly, which can be observed externally as a shift in the transmission spectrum along the wavelength axis. For a fixed input operating wavelength, although the input operating wavelength itself remains unchanged, the output light intensity corresponding to the fixed operating wavelength on the transmission spectrum will change due to the shift in the transmission spectrum position, thus enabling modulation of the output optical signal.

[0074] Furthermore, at different positions in the transmission spectrum, the output light intensity change caused by the same magnitude of transmission spectrum shift is not the same. When the fixed operating wavelength is located in the non-resonant wavelength region, even if the transmission spectrum shifts to a certain extent, the change in output light intensity is usually small; while when the fixed operating wavelength is near the resonant wavelength, a small transmission spectrum shift can cause a more significant change in output light intensity, thereby improving modulation sensitivity. Preferably, the fixed operating wavelength can correspond to the operating region with a large transmission spectrum slope, such as the region near the maximum slope. In some embodiments, the effective refractive index of the connecting waveguide 6 can be slowly adjusted by the thermal phase shifter 8 to make the fixed operating wavelength correspond to a preset operating region with a large transmission spectrum slope; based on this, the electro-optic modulation unit 7 can further quickly adjust the effective refractive index of the connecting waveguide 6 to make the transmission spectrum dynamically shift slightly relative to the fixed operating wavelength, thereby converting the input electrical signal into a change in output light intensity and realizing high-speed information modulation.

[0075] In the first embodiment of this application, the resonant modulator is fabricated based on a silicon-on-insulator (SOI) platform, with the core layer composed of silicon material. Under this material system, the electro-optic modulation unit 7 operates based on the plasma dispersion effect. By adjusting the free carrier concentration in the relevant regions of the PN junction or PIN junction, the effective refractive index of the waveguide is changed, thereby altering the propagation phase of the optical signal to achieve high-speed electro-optic modulation of the output optical signal of the resonant modulator.

[0076] like Figure 4 As shown, the electro-optic modulation unit 7 includes a doped region formed based on the connecting waveguide 6 and a modulation electrode 71. The doped region includes a P-type doped region and an N-type doped region, which form a PN junction (or PIN junction) in the connecting waveguide 6. In the doped region, the connecting waveguide 6 presents a ridge waveguide structure, with the central protrusion forming the main body of the connecting waveguide for carrying the optical mode, and the two sides being widened portions.

[0077] In this embodiment, to further optimize electrical performance, the P-type doped region can be further subdivided into P++ doped region 72, P+ doped region 73, and P doped region 74, and the N-type doped region can be further subdivided into N doped region 75, N+ doped region 76, and N++ doped region 77. In embodiments employing a PIN junction structure, an intrinsic region can also be provided between the P-type and N-type doped regions. It should be understood that the above doping distribution is merely illustrative, and this application is not limited to the specific segmentation and positional distribution of P++ / P+ / P and N++ / N+ / N; without departing from the technical concept of this application, the number of layers, doping concentration gradient, distribution morphology, and relative positions of the P-type and N-type doped regions in the waveguide cross-section can be adjusted according to device process and performance requirements to form the desired carrier depletion-type and / or injection-type modulation structure.

[0078] The modulation electrode 71 is disposed in the upper cladding 13 and electrically connected to the doped region. During operation, a modulation signal is applied to the PN junction or PIN junction through the modulation electrode 71 to change the free carrier concentration distribution in the junction region, thereby changing the effective refractive index of the connected waveguide 6 and the propagation phase of the optical signal, realizing high-speed electro-optic modulation of the output optical signal of the resonant modulator.

[0079] like Figure 5 As shown, the resistive heating structure 81 and the thermal phase shifter electrode 82 of the thermal phase shifter 8 are disposed in the upper cladding 13. The resistive heating structure is disposed adjacent to the connecting waveguide 6 to form thermal coupling. During operation, an electrical signal is applied through the thermal phase shifter electrode 82, causing the resistive heating structure 81 to generate Joule heating, changing the temperature of a local area of ​​the connecting waveguide 6, and thus utilizing the thermo-optical effect of silicon material to change the effective refractive index of the connecting waveguide 6, thereby adjusting the operating point of the device.

[0080] Figure 6 A schematic top view of a resonant modulator according to a second embodiment of this application is shown.

[0081] It should be noted that, Figure 6 Primarily used to demonstrate the planar layout of the core waveguide structure. In reality, both the thermal phase shifter 8 and the electro-optic modulation unit 7 are disposed in or on the surface of the upper cladding 13 above the core waveguide. Figure 6 The relative positions of the components to the core waveguide are indicated by perspective overlay. This illustration does not imply that the components and the core waveguide structure are on the same physical plane.

[0082] like Figure 6As shown, the second embodiment of this application maintains the same overall architecture, optical path connection, and functional positioning as the first embodiment. The main difference lies in the material system and the physical implementation of the electro-optic modulation unit. Specifically, in this embodiment, the core layer of the resonant modulator can be composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3) material, for example, it can be implemented based on a thin-film lithium niobate or thin-film lithium tantalate platform. X-cut oriented thin-film lithium niobate is used as an example for illustration. The layout and connection relationship of the multimode interference region 1, feedback input port waveguide 2, main input port waveguide 3, feedback output port waveguide 4, main output port waveguide 5, and connecting waveguide 6 correspond to those of the first embodiment. Each port waveguide can also be configured as a tapered structure to achieve mode field matching with the multimode interference region 1. Furthermore, this embodiment also includes an input waveguide 9 and an output waveguide 10, which are optically connected to the input end of the main input port waveguide 3 and the output end of the main output port waveguide 5, respectively.

[0083] In the aforementioned material system, the electro-optic modulation unit 7 no longer relies on carrier dispersion effects, but instead utilizes the material's own linear electro-optic effect (Pockels effect) to achieve high-speed phase modulation. The principle is as follows: under the action of an applied electric field, the characteristic that the refractive index of a non-centrosymmetric crystal changes linearly with the electric field intensity is used to achieve high-speed dynamic modulation of the optical signal.

[0084] Specifically, the electro-optic modulation unit 7 includes a modulation electrode disposed in or on the surface of the upper cladding 13. The modulation electrode has no direct physical contact with the bottom connecting waveguide 6, but forms an electric field coupling with the first region of the connecting waveguide 6. To match the specific physical properties of lithium niobate / lithium tantalate materials (such as refractive index, electro-optic coefficient, dielectric constant, and microwave loss), the modulation electrode can be designed accordingly: for example, the electrode material can be gold (Au); the electrode configuration can be a GS (Ground-Signal) or GSG (Ground-Signal-Ground) coplanar waveguide; simultaneously, the electrode size can be optimized to reduce electrode capacitance and match the refractive indices of microwaves and light waves, thereby meeting high bandwidth requirements and ensuring a large electro-optic mode overlap integral. During operation, an external radio frequency electric field is applied to the first region of the connecting waveguide 6 through the modulation electrode, and the effective refractive index of the connecting waveguide 6 is changed using the linear electro-optic effect, thereby achieving phase modulation of the optical signal propagating in the optical feedback loop.

[0085] In this embodiment, the structure and function of the thermal phase shifter 8 are the same as in the first embodiment, and its resistance heating structure and thermal phase shifter electrodes are also disposed in the upper cladding 13. To match the current material system, the resistance heating structure of the thermal phase shifter 8 can be made of materials such as nickel-chromium alloy (NiCr), and the phase bias of the optical signal can be adjusted at a low speed through the Joule heating effect.

[0086] contrast Figure 3 and Figure 6 As can be seen, in the first embodiment, the thermal phase shifter 8 is generally positioned directly above the connecting waveguide 6, while in the second embodiment, the thermal phase shifter 8 can be positioned to the side and above the connecting waveguide 6. This difference in the accompanying drawings precisely demonstrates the flexibility in the placement of related components in this application. Whether the thermal phase shifter modulates the optical signal at low speed through thermal coupling, or the electro-optic modulation unit modulates the optical signal at high speed through electric field coupling, neither depends on a specific fixed spatial orientation, as long as effective physical field (thermal field or electric field) coupling can be formed. This flexible configuration of spatial layout further illustrates the broad meaning of the "associated placement" of functional units and connecting waveguides in this application: regardless of whether the heating structure or modulation electrode is located directly above, to the side and above the waveguide, or in other non-contact positions that can form effective physical field coupling, it clearly falls within the protection scope of this application.

[0087] Furthermore, in the actual fabrication process, the waveguide width, etching depth, cladding thickness, and other geometric dimensions can be optimized without altering the overall optical path connection to maintain the waveguide's single-mode transmission characteristics and the target coupling ratio. These adjustments are conventional equivalent parameter changes due to material system substitution and do not alter the basic topology and core working principle of the resonant modulator based on a multimode interference coupler in this application.

[0088] In terms of overall working mechanism, the optical path of this embodiment is the same as that of the first embodiment: the fundamental mode light from the optical input end a enters the input waveguide 9 through fiber-to-chip coupling, is transmitted to the main input port waveguide 3, and is coupled into the multimode interference region 1. Within the multimode interference region 1, the optical field is distributed: a portion of the light is transmitted through the main output port waveguide 5 to the output waveguide 10, and finally output to the optical receiver end b; the other portion of the light enters the connecting waveguide 6 and propagates cyclically along the feedback loop, thereby forming a wavelength-selective output response. In this feedback loop, phase calibration and bias point locking are performed using a thermal phase shifter 8, and dynamic high-speed phase modulation is performed using an electro-optic modulation unit 7. The light is then fed back to the multimode interference region 1 via the connecting waveguide 6 and the feedback input port waveguide 2, interfering with the input light. This cycle repeats to form a stable output.

[0089] It should be noted that the technical solution described in this application can be modified in various ways, but it does not depart from the core technical concept of this application.

[0090] The structure of a multimode interference coupler is not limited to the regular geometry shown in the figure. On the one hand, by adjusting geometric parameters such as the aspect ratio of the multimode interference region, the position of the tapered waveguide at the port, and the gradient slope, parameters such as the power distribution ratio at the output port and the propagation loss of the connecting waveguide can be controlled. This allows the resonant modulator to operate in or approach different states such as critical coupling, overcoupling, or undercoupling to adapt to different application requirements. On the other hand, reverse engineering, topology optimization, or machine learning algorithms can be used to optimize the multimode interference region and / or the port waveguide, generating non-intuitive, irregular contour structures (such as pixelated boundaries, free-form curve boundaries, etc.) to achieve more precise power distribution ratio control, lower propagation loss, and / or higher process / manufacturing tolerance.

[0091] Furthermore, the geometry of the connecting waveguide can be adjusted to circular, Euler-curved, or helical structures according to layout requirements. The electro-optic modulation unit can be driven by single-arm modulation, dual-arm push-pull, or differential driving, and the electrode type can be selected as lumped electrode, segmented electrode, or traveling-wave electrode depending on the application. Specifically, in silicon-based platforms, the electro-optic modulation unit can employ modulation structures such as MOS capacitor type, PN junction depletion type, or PIN junction injection type; in lithium niobate or lithium tantalate platforms, the electro-optic modulation unit can employ a modulation structure based on the linear electro-optic effect.

[0092] All the above-mentioned changes, without altering the basic technical concept of this application, fall within the scope of protection of this application.

[0093] To verify the device performance of the first embodiment described above, optical simulation and characteristic analysis were performed on the multimode interference coupler based on the silicon-on-insulator platform and the resonant modulator formed therefrom. Figures 7 to 10 The relevant simulation results are presented.

[0094] Figure 7 A schematic diagram illustrating the electric field intensity distribution of a multimode interference coupler according to an embodiment of this application is shown.

[0095] like Figure 7 As shown, under the TE0 fundamental mode input condition (1550 nm wavelength), simulation results demonstrate that the light field excites multiple modes and causes interference within the multimode interference region, ultimately achieving energy redistribution at the output port. The simulation results verify that the multimode interference coupler can achieve stable power distribution and confirm the working mechanism based on the self-imaging principle. The color intensity in the figure represents the magnitude of the electric field strength; the gradient from blue (low intensity) to red (high intensity) clearly illustrates the propagation and interference process of light waves within the multimode interference region.

[0096] Figure 8 The transmittance simulation curve of a multimode interference coupler according to an embodiment of this application is schematically shown.

[0097] like Figure 8 As shown, the simulation results show that the two output ports E of the multimode interference coupler o1 and E o2 The transmittance remains stable in the wavelength range of 1540 nm to 1560 nm, consistently around 50%, indicating that the multimode interference coupler has good broadband characteristics.

[0098] Figure 9 The transmission loss simulation curve of the resonant modulator according to an embodiment of this application is illustrated schematically.

[0099] like Figure 9 As shown, the device has an output port E o1 It exhibits typical periodic resonance peaks, verifying the resonance effect formed by feedback connection.

[0100] Figure 10 The diagram schematically illustrates a simulation comparison of the normalized full width at half maximum (FWHM) and quality factor of a resonant modulator according to an embodiment of this application and a conventional directionally coupled micro-ring modulator.

[0101] like Figure 10 As shown, the horizontal axis represents the wavelength offset relative to the resonant wavelength, and the vertical axis represents the normalized transmittance. The blue curve (MRR) represents the traditional micro-ring modulator, and the red curve (MMI-ring) represents the resonant modulator based on a multimode interference coupler. Simulation comparison results show that the quality factor (Q value) of the traditional micro-ring modulator is 2.48 × 10⁻⁶. 5 The full width at half maximum (FWHM) is 0.0042 nm; the Q value of the resonant modulator based on the multimode interference coupler is 1.52 × 10⁻⁶. 4 The FWHM is 0.068 nm. The resonant modulator based on the multimode interference coupler exhibits a wider resonant linewidth and a lower quality factor, which helps to reduce the sensitivity of the device's operating point to resonant wavelength drift and improve the operating tolerance in practical applications.

[0102] Figure 11 A schematic diagram of an optical computing system structure constructed using a resonant modulator according to an embodiment of this application is shown.

[0103] In an embodiment of this application, an optical computing system constructed using a resonant modulator according to an embodiment of this application is also provided, comprising: a laser source; a first resonant modulator and a second resonant modulator, both of which are the aforementioned resonant modulators based on a multimode interference coupler, wherein the first resonant modulator is configured as a data loading node and the second resonant modulator is configured as a weight loading node; wherein the output end of the laser source is optically connected to the input end of the main input port waveguide of the first resonant modulator, and the output end of the main output port waveguide of the first resonant modulator is optically connected to the input end of the main input port waveguide of the second resonant modulator.

[0104] like Figure 11 As shown, the optical computing system employs a cascaded approach of two resonant modulators based on multimode interference couplers to achieve analog multiplication operations in the optical domain. The continuous light output from the laser source first enters the first resonant modulator (labeled X), which is configured as a data loading node, modulating the optical carrier by applying a data signal. The optical signal modulated by the first resonant modulator then enters the second resonant modulator (labeled W), which is configured as a weight loading node, modulating the modulated optical signal by applying a weight signal. Through this cascaded modulation physical mechanism, the system can efficiently perform analog multiplication operations in the optical domain, thereby achieving hardware acceleration of core algorithms such as matrix-vector multiplication, convolution, and fully connected neural networks.

[0105] Figure 12 A schematic diagram of a photonic integrated system structure constructed using a resonant modulator according to an embodiment of this application is shown.

[0106] Another aspect of this application provides a photonic integrated system constructed from resonant modulators according to embodiments of this application, comprising: a plurality of the aforementioned resonant modulators based on multimode interference couplers; wherein the plurality of resonant modulators are optically interconnected to form one of the following topologies or any combination thereof: series connection, parallel connection, two-dimensional matrix network connection, and nested recursive connection. This photonic integrated system can be applied to scenarios such as on-chip optical interconnects, high-speed optical communication, optical computing, optical neural networks, and microwave photonic signal processing.

[0107] like Figure 12 As shown, the resonant modulator in this embodiment can be expanded into a large array using various topologies to construct complex photonic integrated systems. Figure 12 (a) in the diagram illustrates a series connection method, in which multiple resonant modulators are arranged sequentially along the same bus waveguide to achieve step-by-step signal processing or multi-channel wavelength division multiplexing. Figure 12 (b) shows a parallel connection method where multiple resonant modulators share the input, enabling power distribution or multi-path parallel processing; Figure 12(c) shows a two-dimensional matrix network connection method, which forms a mesh topology through cross-connection, enabling programmable optical routing and matrix operations; Figure 12 (d) and Figure 12 Figure (e) illustrates a connection method based on hierarchical nesting and combined expansion. Building upon the serial main link, recursive expansion of serial and parallel connections is achieved by introducing local parallel branches and hierarchically nested combined structures, thus constructing an optical connection topology with higher degrees of freedom. It should be noted that the above topology is not limited to the example shown in the figure; those skilled in the art can design other connection methods or combinations according to actual application requirements. Through independent phase control of each unit, these extended structures can be reconfigured into various functional modules such as programmable optical computing units (performing convolution, matrix multiplication, and nonlinear activation), tunable filters, optical routing, or wavelength division multiplexing components. The high process tolerance and thermal stability of the resonant modulator based on the multimode interference coupler enable this large-scale array system to maintain reliable performance in complex manufacturing environments, providing a flexible and robust technical solution for the design of high-density photonic integrated chips.

[0108] The embodiments of this application have now been described in detail with reference to the accompanying drawings.

[0109] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application.

Claims

1. A resonant modulator, characterized in that, include: Substrate layer; A buried layer is disposed on the substrate layer; A core layer is formed on the buried layer; An upper cladding layer covers at least a portion of the surface of the core layer; The core layer includes: a multimode interference coupler and a connecting waveguide; The multimode interference coupler includes a multimode interference region and four port waveguides, wherein the multimode interference region includes an input side and an output side; The four port waveguides are divided into: a main input port waveguide and a feedback input port waveguide that are optically connected to the input side of the multimode interference region through their respective output ends; and a main output port waveguide and a feedback output port waveguide that are optically connected to the output side of the multimode interference region through their respective input ends. The two ends of the connecting waveguide are optically connected to the output end of the feedback output port waveguide and the input end of the feedback input port waveguide, respectively, so that the connecting waveguide and the multimode interference coupler together form a closed optical feedback loop. An electro-optic modulation unit is associated with a first region along the length of the connecting waveguide and is used to adjust the effective refractive index of the connecting waveguide by applying an electrical signal to change the resonant state of the resonant modulator.

2. The resonant modulator according to claim 1, characterized in that, It also includes a thermal phase shifter, which is associated with a second region along the length of the connecting waveguide and thermally coupled to the connecting waveguide to adjust the effective refractive index of the connecting waveguide through a thermo-optical effect.

3. The resonant modulator according to claim 2, characterized in that, The thermal phase shifter includes a resistance heating structure and a thermal phase shifter electrode. The resistance heating structure is disposed in the upper cladding, and the thermal phase shifter electrode is electrically connected to the resistance heating structure.

4. The resonant modulator according to claim 1, characterized in that, The port waveguide is a tapered waveguide, wherein the dimension of the end of the port waveguide connected to the multimode interference region is larger than the dimension of the end away from the multimode interference region.

5. The resonant modulator according to claim 1, characterized in that, The core layer is made of silicon material; The electro-optic modulation unit includes a modulation electrode and a doped region formed based on the connecting waveguide. The doped region includes a P-type doped region and an N-type doped region, which are used to form a PN junction or a PIN junction. The modulation electrode is electrically connected to the doped region and is used to apply a modulation signal to the PN junction or PIN junction.

6. The resonant modulator according to claim 1, characterized in that, The core layer is made of lithium niobate or lithium tantalate.

7. The resonant modulator according to claim 6, characterized in that, The electro-optic modulation unit includes a modulation electrode disposed on the surface or inside the upper cladding and forming an electric field coupling with the connecting waveguide, for applying an external electric field in the first region to adjust the effective refractive index of the connecting waveguide through the electro-optic effect.

8. The resonant modulator according to claim 1, characterized in that, It also includes an input waveguide and an output waveguide, wherein the input waveguide is optically connected to the input end of the main input port waveguide, and the output waveguide is optically connected to the output end of the main output port waveguide.

9. The resonant modulator according to claim 5, characterized in that, The P-type doped region includes a P-doped region, a P+ doped region, and a P++ doped region, and the N-type doped region includes an N-doped region, an N+ doped region, and an N++ doped region.

10. The resonant modulator according to claim 1, characterized in that, The substrate is made of silicon, and the buried layer and the upper cladding are made of silicon dioxide.

11. An optical computing system, characterized in that, include: Laser source; The first resonant modulator and the second resonant modulator are both resonant modulators according to any one of claims 1-10, wherein the first resonant modulator is configured as a data loading node and the second resonant modulator is configured as a weight loading node. The output end of the laser source is optically connected to the input end of the main input port waveguide of the first resonant modulator, and the output end of the main output port waveguide of the first resonant modulator is optically connected to the input end of the main input port waveguide of the second resonant modulator.

12. A photonic integrated system, characterized in that, include: Multiple resonant modulators according to any one of claims 1-10; The multiple resonant modulators are optically connected to each other to form one of the following topologies or any combination thereof: series connection, parallel connection, two-dimensional matrix network connection, and nested recursive connection.

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