Ridge waveguide fully integrated cavity optical force accelerometer

Abstract

The invention discloses a ridge waveguide fully integrated cavity optical force accelerometer, which comprises a distributed feedback laser, an on-chip silicon waveguide structure, a mechanical sensitive structure, an on-chip integrated microcavity, an on-chip germanium photoelectric detector, a signal conditioning module, a DC (Direct Current) stabilizing module, a DC power socket and a signal output interface, the on-chip silicon waveguide structure is connected with the mechanical sensitive structure and the on-chip integrated microcavity coupling structure, the mechanical sensitive structure and the on-chip integrated microcavity coupling structure are connected with the on-chip germanium photoelectric detector, the on-chip germanium photoelectric detector is connected with the signal conditioning module, and the signal conditioning module is connected with the DC stabilization module and the signal output interface. The DC stabilization module is respectively connected with the distributed feedback laser and the DC power socket; the distributed feedback laser provides a single longitudinal mode laser source with stable wavelength and strong coherence, ensures efficient generation of an optical mechanical coupling effect, and is a core light source for realizing acceleration high-sensitivity detection.

Description

Technical Field

[0001] This invention belongs to the fields of micro-opto-electro-mechanical systems (MOEMS), silicon-based photonics and inertial sensing technology, and specifically relates to a ridge waveguide fully integrated cavity optical accelerometer. Background Technology

[0002] Accelerometers, as core components of inertial sensing, play a crucial role in inertial navigation, industrial inspection, and consumer electronics. While traditional accelerometers (such as piezoelectric and capacitive sensors) have achieved widespread application, they have significant limitations: piezoelectric sensors face a trade-off between sensitivity and bandwidth, making it difficult to simultaneously meet the requirements of high sensitivity and wide bandwidth; capacitive sensors are susceptible to electromagnetic interference, and after miniaturization, parasitic capacitance has a significant impact, limiting detection accuracy; furthermore, traditional sensors have low integration levels, making it difficult to adapt to the current trend of miniaturization and multifunctionality in equipment development.

[0003] Cavity optical force sensing technology, based on the optomechanical coupling effect, utilizes the high sensitivity of optical resonant cavities to achieve precise detection of weak mechanical motion, providing a new technological path for acceleration sensing. However, existing cavity optical force accelerometers mostly rely on external optical components (such as fiber lasers, discrete optical resonant cavities, and external photodetectors), resulting in problems such as large system size, high optical transmission loss, and difficulty in optical alignment, which severely restricts their application in portable and integrated scenarios. In summary, existing integrated acceleration sensing solutions still face challenges in achieving a balance between miniaturization, high sensitivity, low power consumption, and wide bandwidth response. Especially in applications with high spatial resolution and high precision requirements, there is a lack of a low-power, high-stability sensor solution that can co-integrate mechanical, electrical, and optical mechanisms on a single chip platform.

[0004] The development of silicon-based photonics and micro-opto-electro-mechanical systems (MOEMS) has made on-chip full integration of cavity optical accelerometers possible. Using silicon-based processes, functional units such as laser sources, waveguides, optical microcavities, mechanical sensing structures, and photodetectors can be monolithically integrated, significantly reducing optical loss and system size. However, previous integration schemes still have several technical bottlenecks: first, the coupling efficiency between waveguides and optical microcavities is low, affecting the strength of optomechanical coupling; second, the inherent resonant frequency of the mechanical sensing structure and the resonant characteristics of the optical microcavity are not well matched, limiting detection sensitivity and bandwidth; third, the bandwidth, responsivity, and other performance characteristics of on-chip photodetectors are insufficient to meet the requirements of high-speed optical signal detection; and fourth, the low integration of the power supply module and signal conditioning circuit leads to decreased system stability and practicality. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems and provide a ridge waveguide fully integrated cavity optical accelerometer with full integration, high sensitivity, anti-electromagnetic interference and low power consumption.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a ridge waveguide fully integrated cavity optical accelerometer, comprising a distributed feedback laser, an on-chip silicon waveguide structure, a mechanical sensing structure, an on-chip integrated microcavity, an on-chip germanium photodetector, a signal conditioning module, a DC stabilization module, and a DC... The system includes a power socket and a signal output interface. A distributed feedback laser is connected to an on-chip silicon waveguide structure. The on-chip silicon waveguide structure is connected to a mechanically sensitive structure and an on-chip integrated microcavity coupling structure. The mechanically sensitive structure and the on-chip integrated microcavity coupling structure are connected to an on-chip germanium photodetector. The on-chip germanium photodetector is connected to a signal conditioning module. The signal conditioning module is connected to a DC stabilization module and a signal output interface. The DC stabilization module is connected to the distributed feedback laser and a DC power socket. The distributed feedback laser provides a wavelength-stable, highly coherent single-longitudinal-mode laser source for the ridge waveguide fully integrated cavity optical accelerometer, ensuring efficient optomechanical coupling and serving as the core light source for high-sensitivity acceleration detection. The on-chip silicon waveguide structure includes a gradient waveguide and a ridge waveguide. The gradient waveguide has a lateral width that gradually transitions from 80-120 nm to 0.6-0.8 μm and a length of 15-30 μm. The ridge waveguide has a ridge width of 0.6-0.8 μm and an etching depth of 250-400 nm and is connected to the gradient waveguide. After guidance, the laser is directed to the on-chip integrated microcavity. The mechanically sensitive structure consists of four U-shaped folded beams supporting a rectangular mass block suspended on a fixed frame. It senses external acceleration, generates mechanical displacement under acceleration, and thus modulates the optomechanical coupling characteristics. The photonic crystal in the on-chip integrated microcavity is integrated into the silicon waveguide system to form a high-Q resonant cavity, which forms optomechanical coupling with the mechanically sensitive structure to realize the response of the optical signal to mechanical motion. The on-chip germanium photodetector is formed by epitaxial growth of germanium on the chip and is located at the optical output end to convert the optical signal after passing through the resonant cavity into an electrical signal. The signal conditioning module is connected to the on-chip germanium photodetector and is used to amplify, filter, and condition the electrical signal to extract characteristic signals related to acceleration. The DC stabilization module and DC power socket provide a stable DC power supply to the system to ensure the normal operation of each functional module. The signal output interface outputs the conditioned electrical signal to realize the detection and transmission of acceleration signals.

[0007] Preferably, the DC stabilization module and DC power socket provide stable DC power to the distributed feedback laser, signal conditioning module, and various functional modules, ensuring system startup and continuous operation. The laser emitted by the distributed feedback laser is guided by an on-chip silicon waveguide structure composed of a gradient waveguide and a ridge waveguide, and enters an on-chip integrated microcavity coupled to a mechanically sensitive structure. When external acceleration acts on the mechanically sensitive structure, it generates mechanical displacement, modulating the optomechanical coupling characteristics and changing the resonance characteristics of the on-chip integrated microcavity. The optical signal modulated by the resonant cavity is transmitted to the on-chip germanium photodetector and converted into an electrical signal. This electrical signal is amplified and filtered by the signal conditioning module to extract the characteristic frequency shift related to acceleration, and finally output through the signal output interface, thereby realizing the detection of acceleration.

[0008] Preferably, the operating wavelength of the distributed feedback laser is 1550 nm in the communication band. This wavelength is highly matched with the fundamental mode resonant wavelength of the on-chip integrated microcavity and is within the optical bandgap of the microcavity. This enables low-loss transmission and efficient coupling. At the same time, its narrow linewidth can avoid frequency interference to ensure the accuracy of optomechanical coupling and high stability, namely low wavelength temperature drift and stable output power, which can prevent wavelength shift and power fluctuation from affecting detection.

[0009] Preferably, the surface of the input end of the gradient waveguide is clad with a material of a refractive index lower than that of silicon. This design can constrain the optical field at the input end, reduce light leakage to the surrounding air or substrate, and better match the characteristics of the input light spot, thereby improving the optical coupling efficiency of the laser from the light source to the gradient waveguide.

[0010] Preferably, the mechanically sensitive structure uses the silicon functional layer of an SOI wafer as the processing substrate, and the mass block and four "U"-shaped beams are integrally etched and formed. The structural parameters of the cantilever beams, including length and width, affect the inherent resonant frequency of the mechanically sensitive structure. The resonant frequency limits the highest frequency of AC acceleration that the sensor can respond to.

[0011] Preferably, the on-chip integrated microcavity is a two-dimensional photonic crystal structure, using a silicon-based air-hole triangular lattice arrangement. In its center, progressive displacement perturbation is applied to the air holes to disrupt the periodic formation of defect regions. This not only confines light within the cavity to achieve strong optical field localization, but also improves the responsiveness to mechanically sensitive structural displacements, thereby enhancing resonance sensitivity and providing a high-Q resonance basis for acceleration-induced micro-displacement detection.

[0012] Preferably, the on-chip germanium photodetector adopts a vertical PIN structure and is grown by selective epitaxy. Its 3-dB response bandwidth can reach the GHz level. Its structural design can reduce current dissipation and improve the signal-to-noise ratio. Furthermore, through a gradient coupling design, it is connected to the silicon waveguide with low loss. It is suitable for accurately detecting changes in output light intensity caused by microcavity resonant modulation and efficiently converting them into corresponding electrical signals, providing a stable input for subsequent signal conditioning.

[0013] Preferably, the signal conditioning module is electrically connected to the on-chip germanium photodetector and integrates a low-noise amplifier, a bandpass filter, and a spectrum analysis unit. The low-noise amplifier amplifies the weak electrical signal output by the detector, the bandpass filter matches the inherent resonant frequency of the mechanically sensitive structure and the acceleration signal bandwidth to filter out out-of-band noise, and the spectrum analysis unit extracts characteristic frequency shift information related to acceleration from the electrical signal. This module, through multi-unit collaboration, achieves efficient processing of GHz-level bandwidth electrical signals, ensuring a high signal-to-noise ratio while accurately extracting acceleration characteristic parameters. Finally, the conditioned signal is transmitted to the signal output interface to achieve quantitative detection of acceleration.

[0014] Preferably, the DC stabilization module and DC power socket are used to connect to an external DC power supply and perform voltage stabilization and filtering to provide a continuous and stable DC power supply for the distributed feedback laser, signal conditioning module, on-chip germanium photodetector, and all system functional modules. By ensuring the stability of the operating voltage of each module, laser wavelength drift, detector response distortion, or signal conditioning accuracy reduction caused by power supply fluctuations are avoided, thereby ensuring the consistency and reliability of the detection performance of the entire accelerometer system during long-term operation.

[0015] The beneficial effects of this invention are:

[0016] 1. The ridge waveguide fully integrated cavity optical accelerometer provided by the present invention has a high degree of integration: it adopts silicon-based monolithic integration technology to integrate the laser source, optical transmission waveguide, sensing microcavity, mechanical structure, detector and signal conditioning related modules into a single chip, without the need for external optical path or discrete optical components, which greatly reduces the system size and complexity and is suitable for miniaturized inertial navigation, implantable sensing and other scenarios.

[0017] 2. The mechanical structure and resonant frequency adaptability of this invention are excellent: using SOI wafer silicon functional layer as the processing substrate, the mass block and four "U" shaped beams are integrally etched and formed, which can precisely control the inherent resonant frequency of the mechanically sensitive structure; compared with the resonant frequency of about 70kHz of the traditional straight beam mechanical structure, the resonant frequency can be controlled below 30kHz, which is compatible with the calibration requirements of commercial accelerometers (up to 30kHz) on the market, ensuring the accuracy of the accelerometer testing process.

[0018] 3. The mechanical structure of this invention has excellent performance: This design has the advantages of stable stress release, small gravity sag, small anchor point loss, and impact resistance.

[0019] 4. The present invention has excellent detection sensitivity and resolution: by taking advantage of the high Q value of the microcavity and the strong optomechanical coupling effect, combined with the stable light source of the narrow linewidth DFB laser, it can achieve precise capture of weak acceleration.

[0020] 5. This invention has strong anti-electromagnetic interference capability: It adopts an optical sensing and transmission mechanism to avoid the problem of traditional capacitive and piezoresistive sensors being susceptible to electromagnetic interference; the silicon-based integrated structure itself has good electromagnetic shielding characteristics and can work stably in strong electromagnetic environments such as industrial automation sites and aerospace electronic systems.

[0021] 6. Low power consumption and long-term stability of the invention: Each functional module adopts a silicon-based low power consumption design (such as low power consumption of DFB laser and low current dissipation of detector), and the DC stabilization module ensures power supply efficiency. The overall system power consumption is significantly lower than that of traditional optical accelerometers. The accelerometer structure is based on SOI wafer integrated etching, and the on-chip integrated microcavity and waveguide coupling characteristics are stable over a long period of time.

[0022] 7. This invention has a wide range of applications: It combines miniaturization, high precision and anti-interference characteristics, and can be widely used in inertial navigation (UAVs, satellites), aerospace precision measurement (launch vehicle orbit detection, manned spaceflight rendezvous and docking), industrial automation control (robot motion control, equipment vibration monitoring), biomedical implantable sensing (human joint motion monitoring) and high-resolution inertial sensor arrays, and is especially suitable for scenarios with strict requirements for integration, sensitivity and environmental adaptability. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a ridge waveguide fully integrated cavity optical accelerometer according to the present invention;

[0024] Figure 2 This is a schematic diagram of the graded waveguide structure of the present invention;

[0025] Figure 3 This is an enlarged view of the mechanical sensing structure of the accelerometer of this invention;

[0026] Figure 4 This is a schematic diagram of the on-chip integrated microcavity structure of the present invention;

[0027] Figure 5 This is a schematic diagram of the optomechanical coupling part of the present invention;

[0028] Figure 6 This is a schematic diagram of the ridge waveguide of the present invention.

[0029] Figure labeling: 1. Distributed feedback laser; 2. On-chip silicon waveguide structure; 3. Mechanically sensitive structure; 4. On-chip integrated microcavity; 5. On-chip germanium photodetector; 6. Signal conditioning module; 7. DC stabilization module; 8. DC power socket; 9. Signal output interface; 21. Gradient waveguide; 22. Ridge waveguide. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0031] like Figures 1 to 6As shown, the present invention provides a ridge waveguide fully integrated cavity optical accelerometer, comprising a distributed feedback laser 1, an on-chip silicon waveguide structure 2, a mechanical sensing structure 3, an on-chip integrated microcavity 4, an on-chip germanium photodetector 5, a signal conditioning module 6, a DC stabilization module 7, a DC power socket 8, and a signal output interface 9. The distributed feedback laser 1 is connected to the on-chip silicon waveguide structure 2. The on-chip silicon waveguide structure 2 is coupled to the mechanical sensing structure 3 and the on-chip integrated microcavity 4. The coupled structure of the mechanical sensing structure 3 and the on-chip integrated microcavity 4 is connected to the on-chip germanium photodetector 5. The on-chip germanium photodetector 5 is connected to the signal conditioning module 6. The signal conditioning module 6 is connected to both the DC stabilization module 7 and the signal output interface 9. The DC stabilization module 7 is connected to both the distributed feedback laser 1 and the DC power socket 8. The distributed feedback laser 1 provides a wavelength-stable and highly coherent single-longitudinal-mode laser source for the ridge waveguide fully integrated cavity optical accelerometer, ensuring the efficient occurrence of the optomechanical coupling effect, and is the core light source for achieving high-sensitivity acceleration detection. The on-chip silicon waveguide structure 2 includes a gradient waveguide 21 and a ridge waveguide 22. The gradient waveguide 21 has a lateral width that gradually transitions from 80-120 nm to 0.6-0.8 μm and a length of 15-30 μm. The ridge waveguide 22 has a ridge width of 0.6-0.8 μm and an etching depth of 250-400 nm. It is connected to the gradient waveguide 21 and is used to guide the laser to the on-chip integrated microcavity 4. The mechanically sensitive structure 3 consists of four U-shaped folded beams supporting a rectangular mass block and suspended on a fixed frame. It is used to sense external acceleration, generate mechanical displacement under the action of acceleration, and thus regulate the optomechanical coupling characteristics. The photonic crystal in the on-chip integrated microcavity 4 is integrated into the silicon waveguide system to form a high-Q resonant cavity. It forms optomechanical coupling with the mechanically sensitive structure 3 to realize the response of the optical signal to mechanical motion. The on-chip germanium photodetector 5 is formed by epitaxial growth of germanium on the chip and is set at the optical output end to convert the optical signal after passing through the resonant cavity into an electrical signal. The signal conditioning module 6 is connected to the on-chip germanium photodetector 5 and is used to amplify, filter, and condition the electrical signal to extract characteristic signals related to acceleration. The DC stabilization module 7 and the DC power socket 8 are used to provide a stable DC power supply to the system, ensuring the normal operation of each functional module. The signal output interface 9 is used to output the conditioned electrical signal to realize the detection and transmission of acceleration signals.

[0032] The ridge waveguide fully integrated cavity optical accelerometer described in this invention is integrated on an SOI (Silicon-On-Insulator) platform and includes a distributed feedback laser, a graded-ridge waveguide on-chip silicon waveguide structure, a high-Q photonic crystal microcavity, a mechanically sensitive structure supported by four straight beams, an on-chip germanium photodetector, a signal conditioning module, a DC stabilization module, and a signal output interface, among other functional modules. All devices are integrated onto the same chip using micro-nano fabrication technology, achieving high integration, miniaturization, and low-loss design.

[0033] The DC stabilization module 7 and DC power socket 8 provide stable DC power to the distributed feedback laser 1, signal conditioning module 6, and various functional modules, ensuring system startup and continuous operation. The laser emitted by the distributed feedback laser 1 is guided by the on-chip silicon waveguide structure 2, composed of a tapered waveguide 21 and a ridge waveguide 22, and enters the on-chip integrated microcavity 4 coupled to the mechanically sensitive structure 3. When external acceleration acts on the mechanically sensitive structure 3, it generates mechanical displacement, modulating the optomechanical coupling characteristics and changing the resonant characteristics of the on-chip integrated microcavity 4. The optical signal modulated by the resonant cavity is transmitted to the on-chip germanium photodetector 5 and converted into an electrical signal. This electrical signal is amplified and filtered by the signal conditioning module 6 to extract the characteristic frequency shift related to acceleration, and finally output through the signal output interface 9, thereby realizing the detection of acceleration. A schematic diagram of its working principle is shown below. Figure 1 As shown.

[0034] In this invention, the laser source is integrated with the on-chip waveguide:

[0035] The distributed feedback laser 1 operates at a wavelength of 1550 nm in the communication band. This wavelength is highly matched with the fundamental mode resonant wavelength of the on-chip integrated microcavity 4 and is within the optical bandgap of the microcavity. This enables low-loss transmission and efficient coupling. At the same time, its narrow linewidth can avoid frequency interference to ensure the accuracy of optomechanical coupling and high stability, namely low wavelength temperature drift and stable output power, which can prevent wavelength shift and power fluctuation from affecting detection.

[0036] The distributed feedback laser 1 (DFB LD) serves as the core light source of the system, with its center wavelength precisely designed for the 1550nm communication band, exhibiting high wavelength stability and strong coherence. To optimize the coupling efficiency between the laser and the on-chip waveguide, a gradient waveguide structure is designed in the waveguide input section. Its lateral width smoothly transitions from 80-120nm to 0.6-0.8μm, with a length of 15-30μm, forming a continuous mode conversion region. This effectively matches the laser source mode with the waveguide mode, reducing coupling loss and suppressing multimode interference. Following the gradient waveguide is a ridge waveguide structure, with a ridge width maintained at 0.6-0.8μm and an etching depth of 250-400nm. It employs a cross-sectional design of "partially etching the top silicon layer and retaining the bottom silicon shoulder," combining excellent lateral optical field confinement with low propagation loss. The ridge waveguide's end is precisely docked with the photonic crystal microcavity. By optimizing the interface structure between the waveguide and the microcavity, efficient laser coupling into the microcavity is ensured, providing a stable optical transmission path for the optomechanical coupling effect. Figure 2 As shown. Figure 2 (a) is an enlarged view of the graded waveguide from 100nm to 350nm, where the width of the etched groove is approximately 3µm; (b) is an enlarged view of the narrow straight waveguide at 350nm, where the width of the etched groove is approximately 1µm, and the white area represents the waveguide portion. Furthermore, the input end surface of the graded waveguide is clad with a material having a refractive index lower than silicon. By constraining the optical field at the input end and reducing light leakage to the surrounding air or substrate, the coupling efficiency of the laser from the light source to the graded waveguide is further improved, ensuring efficient injection of optical energy into the subsequent transmission link.

[0037] The input surface of the graded waveguide 21 is clad with a material whose refractive index is lower than that of silicon, most typically silicon dioxide (SiO2), but polymer materials (such as polymethyl methacrylate, PMMA) can also be used in low-cost scenarios. This design can improve the optical coupling efficiency of the laser from the light source to the graded waveguide by confining the optical field at the input end, reducing light leakage to the surrounding air or substrate, and better matching the characteristics of the input light spot.

[0038] In this embodiment, the mechanically sensitive structure 3 includes a U-shaped beam group and a mass block. The U-shaped beam group includes a first beam 31, a second beam 32, a third beam 33 and a fourth beam 34. The first beam 31 and the second beam 32 are connected to form a U-shaped beam. The third beam 33 and the fourth beam 34 are connected and arranged symmetrically with the first beam 31 and the second beam 32.

[0039] The mechanically sensitive structure 3 uses the silicon functional layer of the SOI wafer as the processing substrate, and integrally etches the mass block and four "U"-shaped beams. The structural parameters of the cantilever beams, including length and width, affect the inherent resonant frequency of the mechanically sensitive structure. The resonant frequency limits the highest frequency of AC acceleration that the sensor can respond to.

[0040] In the accelerometer testing phase, to ensure accuracy, the acceleration signal generated by the sheared chip needs to be calibrated using a commercial accelerometer. Currently, the highest resonant frequency of commercial accelerometers on the market reaches only 30kHz. Compared to the resonant frequency of traditional straight-beam mechanical structures, which is close to 70kHz, this design can control the resonant frequency below 30kHz, allowing for direct calibration with a commercial accelerometer. Furthermore, this design offers advantages such as stable stress release, minimal gravity-induced sagging, low anchor point loss, and impact resistance.

[0041] The integration of the on-chip integrated microcavity 4 and the mechanically sensitive structure 3 in this invention is as follows:

[0042] On-chip integrated microcavity 4 and mechanically sensitive structure 3 are coplanarly arranged on the silicon functional layer of the SOI wafer, with a thickness of 250-500 nm, forming a strong optomechanical coupling region. The optomechanical coupling principle is as follows: Figure 4 As shown.

[0043] The on-chip integrated microcavity design and fabrication process involves the following steps: The microcavity employs a two-dimensional silicon-based triangular lattice arrangement of air holes, with a lattice constant of 505-510 nm and air hole radii of 153-187.5 nm. A progressive displacement perturbation is applied to the air holes in the center, displacing some holes by 5 nm, 10 nm, and 15 nm away from the center, disrupting the periodicity and forming defect regions to confine the optical field. This design achieves an optical Q-value of 2.6 × 10⁻⁶ for the microcavity. 5 Actual measurement exceeded 2×10 4 It can achieve strong light field localization, enhance the response sensitivity to mechanical displacement, and its fundamental mode resonant wavelength is highly matched with the output wavelength of DFB laser (1550nm) and is within the range of photonic crystal bandgap (1403.1-2217.9nm), minimizing optical transmission loss.

[0044] Design and fabrication process of mechanically sensitive structures: Mechanically sensitive structures such as Figure 3 The structure shown is formed using an integrated etching process, consisting of a mass block (120μm × 150μm) and four U-shaped beams (40μm long, 0.5μm wide) etched together. Both the mass block and the cantilever beams have periodic etched holes of 2μm × 6.6μm on their surfaces to release the silica layer during processing, allowing the mechanical oscillator to remain suspended and preventing adhesion to the substrate that could affect the vibration response. The inherent resonant frequency of this structure can be controlled below 30kHz, allowing for direct calibration using commercial accelerometers. This design offers advantages such as stable stress release, minimal gravitational sag, low anchor point loss, and impact resistance.

[0045] The on-chip integrated microcavity 4 is a two-dimensional photonic crystal structure, which adopts a silicon-based triangular lattice arrangement of air holes. In the middle, progressive displacement perturbation is applied to the air holes, such as some air holes being displaced 5-15nm away from the center, which disrupts the periodicity and forms a defect region. This can not only confine the light within the cavity to achieve strong light field localization, but also improve the responsiveness to mechanically sensitive structural displacements, thereby enhancing the resonance sensitivity and providing a high-Q resonance basis for acceleration-induced micro-displacement detection.

[0046] The optical signal acquisition and conversion process of this invention is as follows:

[0047] The output of the photonic crystal microcavity 4 is connected to a straight waveguide, at which an on-chip germanium photodetector is integrated. This detector is grown using selective epitaxy to form a vertical PIN structure (P+ and N+ junctions are located in the silicon and germanium regions, respectively, separated by a germanium absorption layer). The detector has a 3-dB response bandwidth reaching the GHz level. Through a graded coupling design, it is docked with the silicon waveguide at low loss, enabling precise capture of microcavity-modulated optical signals and efficient conversion into electrical signals. The amplitude of the converted electrical signal is linearly related to the change in light intensity, providing a stable, high signal-to-noise ratio input for subsequent signal conditioning.

[0048] The on-chip germanium photodetector 5 adopts a vertical PIN structure and is grown by selective epitaxy. Its 3-dB response bandwidth can reach the GHz level. Its structural design can reduce current dissipation and improve the signal-to-noise ratio. Furthermore, through a gradient coupling design, it is connected to a silicon waveguide with low loss. It is suitable for accurately detecting changes in output light intensity caused by microcavity resonant modulation and efficiently converting them into corresponding electrical signals, providing a stable input for subsequent signal conditioning.

[0049] The signal conditioning module 6 is electrically connected to the on-chip germanium photodetector 5 and integrates a low-noise amplifier, a bandpass filter, and a spectrum analysis unit. The low-noise amplifier amplifies the weak electrical signal output by the detector, the bandpass filter matches the inherent resonant frequency of the mechanically sensitive structure and the bandwidth of the acceleration signal to filter out out-of-band noise, and the spectrum analysis unit extracts characteristic frequency shift information related to acceleration from the electrical signal. Through multi-unit collaboration, this module achieves efficient processing of GHz-level bandwidth electrical signals, ensuring the signal-to-noise ratio while accurately extracting acceleration characteristic parameters. Finally, the conditioned signal is transmitted to the signal output interface to achieve quantitative detection of acceleration.

[0050] The signal conditioning circuit design of this invention is as follows:

[0051] The signal conditioning circuitry is integrated on the peripheral PCB board of the chip, including a low-noise amplifier (LNA), a bandpass filter, and a spectrum analysis unit, and is electrically connected to the on-chip germanium photodetector. The LNA amplifies the weak electrical signal output by the detector, suppressing circuit noise interference. The bandpass filter's passband range matches the operating bandwidth of the mechanically sensitive structure, filtering out out-of-band signals such as thermal noise and environmental interference. The spectrum analysis unit extracts characteristic frequency shifts in the electrical signal (such as mechanical resonant frequency offset) and, combined with a preset response curve, inversely obtains the amplitude and frequency parameters of the acceleration, effectively ensuring the accuracy of acceleration detection.

[0052] The DC stabilization module 7 and DC power socket 8 are used to connect to an external DC power supply and to regulate and filter it, providing a continuous and stable DC power supply for the distributed feedback laser 1, signal conditioning module 6, on-chip germanium photodetector 5, and all system functional modules. By ensuring the stability of the operating voltage of each module, the system avoids laser wavelength drift, detector response distortion, or signal conditioning accuracy degradation caused by power supply fluctuations, thereby ensuring the consistency and reliability of the detection performance of the entire accelerometer system during long-term operation.

[0053] The DC power supply system of this invention is designed as follows:

[0054] The DC stabilization module and DC power socket constitute the core of the system's DC power supply, used to connect to an external DC power source and perform voltage regulation and filtering. The power supply system provides continuous and stable DC power to all system functional modules, including the distributed feedback laser, on-chip germanium photodetector, and signal conditioning module. This design avoids laser wavelength drift, detector response distortion, or decreased signal conditioning accuracy caused by power supply fluctuations, ensuring the consistency and reliability of the system's detection performance during long-term operation, while optimizing power distribution to adapt to low-power application scenarios.

[0055] The signal output interface design of this invention is as follows:

[0056] The signal output interface connects directly to the signal conditioning module and adopts a standardized interface design, adaptable to the signal access requirements of external data acquisition devices, inertial navigation systems, and other terminal devices. The conditioned acceleration characteristic electrical signal (such as an amplified and filtered frequency shift signal) is output through this interface, enabling real-time transmission and subsequent processing of acceleration data, meeting the data interaction needs of different application scenarios.

[0057] Through the above technical solution, the present invention can achieve high sensitivity and high resolution detection of weak acceleration, and is applicable to inertial navigation, aerospace precision measurement, industrial automation control, biomedical implantable sensing and high resolution inertial sensor arrays and other application scenarios.

[0058] To understand the working process of this invention, the working principle of this invention is as follows:

[0059] The DC stabilization module 7 and DC power socket 8 provide a stable DC power supply for the entire system, ensuring the startup and continuous operation of each module. The 1550nm wavelength laser emitted by the distributed feedback laser 1 is transmitted with low loss through the on-chip silicon waveguide structure 2, composed of a tapered waveguide 21 and a ridge waveguide 22, and coupled to a high-Q microcavity strongly coupled to the mechanically sensitive structure 3. When external acceleration occurs, the mass block of the mechanically sensitive structure 3 is driven by inertial force to generate a micro-displacement. This displacement modulates the resonant characteristics of the microcavity through optomechanical coupling, including the resonant frequency and optical field distribution, causing corresponding modulation of the optical signal within the cavity. The modulated optical signal is transmitted to the on-chip germanium photodetector 5 and converted into an electrical signal. The electrical signal is amplified, filtered, and subjected to spectral analysis by the signal conditioning module to extract the characteristic frequency shift related to acceleration, and finally output through the signal output interface 9, achieving high-precision quantitative detection of acceleration.

[0060] This invention relates to a ridge waveguide fully integrated cavity optical accelerometer, belonging to the interdisciplinary field of micro-opto-electro-mechanical systems (MOMES) and inertial sensing technology, specifically an on-chip fully integrated high-precision accelerometer based on optical-mechanical coupling and inertial force driving mechanisms. The accelerometer employs the synergistic integration of a distributed feedback laser (DFB LD), a ridge waveguide integrated transmission structure, a high-Q photonic crystal microcavity, a novel mechanical sensing structure formed by a sensitive mass block suspended by an elastic beam, an on-chip germanium photodetector (GePD), and signal conditioning circuitry to construct a fully integrated optical-mechanical coupling resonant system without external optical paths. Under external acceleration, the sensitive mass block undergoes micro-displacement driven by inertial force. The optical-mechanical coupling effect modulates the resonant frequency and optical field distribution of the photonic crystal microcavity. After the laser is transmitted to the microcavity with low loss via the ridge waveguide, the resonant optical signal is converted into an electrical signal by the on-chip photodetector. The signal processing module then extracts the acceleration characteristic parameters (amplitude and frequency), achieving high sensitivity and high resolution detection of weak accelerations. The device of this invention has technical advantages such as fully integrated design (monolithic integration of ridge waveguide and functional unit, reducing optical loss and system size), high Q value photomechanical resonance characteristics, low power consumption, anti-electromagnetic interference, and strong long-term stability. It is suitable for applications such as inertial navigation, aerospace precision measurement, industrial automation control, biomedical implantable sensing, and high-resolution inertial sensor arrays.

[0061] This invention proposes a ridge waveguide fully integrated cavity optical accelerometer based on cavity-optical-mechanical coupling effect. It integrates a distributed feedback laser, a gradient-ridge waveguide transmission structure, an on-chip integrated microcavity, a novel mechanical sensing structure, an on-chip germanium photodetector, a signal conditioning module, and a DC stable power supply module onto a silicon-based platform. Utilizing the ridge waveguide for low-loss optical transmission and the strong coupling effect between the on-chip integrated microcavity and the mechanical structure, while matching the performance parameters of each functional unit (such as laser wavelength and microcavity resonant wavelength, mechanical resonant frequency and optical response bandwidth, detector bandwidth and optical signal rate), it fundamentally solves problems such as low integration density, insufficient coupling efficiency, poor performance matching, and weak system stability. Ultimately, it achieves a fully integrated, high-sensitivity, and electromagnetic interference-resistant on-chip inertial sensing system, providing an innovative solution for the field of inertial measurement that combines miniaturization, high precision, and practicality.

[0062] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A ridge waveguide fully integrated cavity optical force accelerometer characterized by: The application relates to a ridge waveguide full-integrated cavity optical force accelerometer, which comprises a distributed feedback laser (1), a silicon waveguide structure (2), a mechanical sensitive structure (3), an integrated microcavity (4), a germanium photodetector (5), a signal conditioning module (6), a DC stabilizing module (7), a DC power socket (8) and a signal output interface (9). The distributed feedback laser (1) is connected with the silicon waveguide structure (2), the silicon waveguide structure (2) is connected with a mechanical sensitive structure (3) and a structure coupled with the integrated microcavity (4), the mechanical sensitive structure (3) and the structure coupled with the integrated microcavity (4) are connected with the germanium photodetector (5), the germanium photodetector (5) is connected with the signal conditioning module (6), the signal conditioning module (6) is connected with the DC stabilizing module (7) and the signal output interface (9), and the DC stabilizing module (7) is connected with the distributed feedback laser (1) and the DC power socket (8). The distributed feedback laser (1) provides a single longitudinal mode laser source with stable wavelength and strong coherence for the ridge waveguide full-integrated cavity optical force accelerometer, guarantees efficient occurrence of optical mechanical coupling effect, and is a core light source for realizing high-sensitivity acceleration detection. The silicon waveguide structure (2) comprises a tapered waveguide (21) and a ridge waveguide (22), the tapered waveguide (21) has a lateral width gradually changing from 80-120nm to 0.6-0.8um and a length of 15-30um, the ridge waveguide (22) has a ridge width of 0.6-0.8um and an etching depth of 250-400nm, is connected to the rear of the tapered waveguide (21) and is used for guiding laser to the integrated microcavity (4). The mechanical sensitive structure (3) supports a rectangular mass block by four "U"-shaped folded beams and is hung on a fixed frame, is used for sensing external acceleration, generates mechanical displacement under the action of acceleration and then regulates and controls optical mechanical coupling characteristics. The photonic crystal in the integrated microcavity (4) is integrated in a silicon waveguide system, is used for forming a high-Q value resonant cavity, forms optical mechanical coupling with the mechanical sensitive structure (3) and realizes response of optical signals to mechanical movement. The germanium photodetector (5) is formed by epitaxial growth of germanium on a chip, is arranged at an output end of an optical path and is used for converting optical signals after the resonant cavity into electrical signals. The signal conditioning module (6) is connected with the germanium photodetector (5), is used for amplifying, filtering and conditioning electrical signals and extracting characteristic signals related to acceleration. The DC stabilizing module (7) and the DC power socket (8) are used for providing stable DC power supply for the system and guaranteeing normal operation of various functional modules. The signal output interface (9) is used for outputting conditioned electrical signals, realizes detection and transmission of acceleration signals.

2. The ridge waveguide fully integrated cavity optomechanical accelerometer according to claim 1, wherein: The DC stabilization module (7) and the DC power socket (8) provide stable DC power supply for the distributed feedback laser (1), the signal conditioning module (6) and each functional module, guaranteeing the system to start and continuously run; the laser emitted by the distributed feedback laser (1) is guided by the on-chip silicon waveguide structure (2) composed of a tapered waveguide (21) and a ridge waveguide (22), and enters the on-chip integrated microcavity (4) coupled with the mechanical sensitive structure (3); when the external acceleration acts on the mechanical sensitive structure (3), it generates mechanical displacement, regulates and controls the optomechanical coupling characteristics, and changes the resonance characteristics of the on-chip integrated microcavity (4); The light signal modulated by the resonant cavity is transmitted to the on-chip germanium photodetector (5) and converted into an electrical signal; the electrical signal is amplified, filtered and conditioned by the signal conditioning module (6), and the characteristic frequency shift related to acceleration is extracted, and finally output through the signal output interface (9), thereby realizing the detection of acceleration.

3. The ridge waveguide fully integrated cavity optomechanical accelerometer of claim 1, wherein: The working wavelength of the distributed feedback laser (1) is 1550 nm communication band, which is highly matched with the fundamental mode resonance wavelength of the on-chip integrated microcavity (4) and is within the microcavity optical bandgap range, which can realize low-loss transmission and high-efficiency coupling, and its narrow linewidth can avoid frequency interference to guarantee the accuracy of optomechanical coupling, high stability, i.e. low wavelength temperature drift and stable output power, which can prevent the influence of wavelength shift and power fluctuation on detection.

4. The ridge waveguide fully integrated cavity optomechanical accelerometer of claim 1, wherein: The input end surface of the tapered waveguide (21) is provided with a cladding layer of other material with a lower refractive index than silicon, which can constrain the input end light field, reduce light leakage to the surrounding air or substrate, better match the input light spot characteristics, and thereby improve the light coupling efficiency from the light source to the tapered waveguide.

5. The ridge waveguide fully integrated cavity optomechanical accelerometer of claim 1, wherein: The mechanical sensitive structure (3) takes the silicon functional layer of the SOI wafer as the processing substrate, and etches the mass block and the four "U" shaped beams into one body, wherein the structural parameters of the cantilever beam, including length and width, affect the natural resonance frequency of the mechanical sensitive structure, and the resonance frequency limits the highest frequency of alternating acceleration that the sensor can respond to.

6. The ridge waveguide fully integrated cavity optomechanical accelerometer of claim 1, wherein: The on-chip integrated microcavity (4) is a two-dimensional photonic crystal structure, which adopts a silicon-based air hole triangular lattice arrangement, and a progressive displacement perturbation is applied to the air hole in the middle to form a defect region by destroying the periodicity, which can confine the light in the cavity to realize strong light field localization, and can also improve the response to the displacement of the mechanical sensitive structure, thereby enhancing the resonance sensitivity and providing a high-Q resonance basis for micro-displacement detection caused by acceleration.

7. The ridge waveguide fully integrated cavity optomechanical accelerometer of claim 1, wherein: The on-chip germanium photodetector (5) adopts a longitudinal PIN structure and is grown by selective epitaxy process, and the 3-dB response bandwidth can reach GHz level. Its structural design can reduce current dissipation and improve signal-to-noise ratio, and through the design of gradual coupling and low-loss docking with the silicon waveguide, it is suitable for accurately detecting the output light intensity change caused by microcavity resonance modulation and efficiently converting it into corresponding electrical signals, providing stable input for subsequent signal conditioning.

8. The ridge waveguide fully integrated cavity optomechanical accelerometer of claim 1, wherein: The signal conditioning module (6) is electrically connected with the on-chip germanium photodetector (5), and is integrated with a low-noise amplifier, a band-pass filter and a spectrum analysis unit; the low-noise amplifier is used for gain amplification of a weak electric signal output by the photodetector, the band-pass filter has a passband range matched with an inherent resonant frequency of the mechanical sensitive structure and an acceleration signal bandwidth to filter out out-of-band noise, and the spectrum analysis unit is used for extracting characteristic frequency shift information related to acceleration in the electric signal; through cooperation of multiple units, the module realizes efficient processing of GHz-level bandwidth electric signals, guarantees signal-to-noise ratio of the signals, accurately extracts acceleration characteristic parameters, finally transmits the conditioned signals to a signal output interface, and realizes quantitative detection of acceleration.

9. The ridge waveguide fully integrated cavity optomechanical accelerometer of claim 1, wherein: The DC stabilization module (7) and the DC power socket (8) are used for connecting an external DC power supply and performing voltage stabilization and filtering processing on the external DC power supply, thereby providing continuous and stable DC power supply for the distributed feedback laser (1), the signal conditioning module (6), the on-chip germanium photodetector (5) and the whole system functional module; through guaranteeing stability of working voltages of the modules, laser wavelength drift, photodetector response distortion or signal conditioning precision reduction caused by power supply fluctuation are avoided, thereby ensuring consistency and reliability of detection performance of the whole accelerometer system during long-term operation.

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