Piezoelectric ceramic driving-based high-precision cavity optical force micro gyroscope

Abstract

The invention discloses a piezoelectric ceramic driving-based high-precision cavity optical force micro gyroscope, which comprises fixed columns, a mechanical structure, optical structures, piezoelectric ceramics and a base, the fixed columns are located at four corners of the mechanical structure, the optical structures are located at two ends of the mechanical structure, and the piezoelectric ceramics and the base are located at the lower part of the mechanical structure. The optical structure comprises a cavity light power system and a waveguide structure, the cavity light power system is coupled with the waveguide structure, the cavity light power system is composed of a pair of optical microcavities, and the optical microcavities are a two-dimensional photonic crystal or echo wall mode microcavity, a Fabry-Perot optical microcavity and a one-dimensional nano cantilever beam. The mechanical structure comprises mass blocks and supporting beams, the mass blocks comprise a core mass block, a detection mass block and a driving mass block, the core mass block is located in the center of the gyroscope and is connected with the driving mass block and the detection mass block through cantilever arms, and the supporting beams comprise a driving supporting beam and a detection supporting beam.

Description

Technical Field

[0001] This invention belongs to the field of high-precision angular velocity measurement technology, specifically relating to a high-precision cavity optical micro-gyroscope driven by piezoelectric ceramics. Background Technology

[0002] In recent years, due to the rapid advancements in precision optical micro / nano fabrication technology, the fabrication difficulty of cavity optical-mechanical structures has decreased, leading to their rapid development. A cavity optical-mechanical structure is a micro / nano cavity structure that, due to optical-mechanical coupling, simultaneously exists in optical and mechanical modes and exchanges energy. The low power consumption and low noise characteristics of cavity optical-mechanical structures enable extremely high measurement accuracy for physical quantities such as minute displacements, masses, temperatures, accelerations, and angular velocities. High-precision micro-gyroscopes based on cavity optical-mechanical structures have broad application prospects in the field of inertial navigation.

[0003] Conventional cavity optical-mechanical micro-gyroscopes employ an electrostatically driven push-pull comb mechanism within an electrical structure to generate displacement. Based on the Coriolis effect, this displacement is then detected under an applied angular velocity. The driving voltage is generated via an external probe or gold wire bonding. In this design, the cavity optical-mechanical micro-gyroscope uses an optical structure for detection and an electrical structure for driving, resulting in overlapping structures and complex manufacturing processes. Furthermore, the cross-coupling between the optical and electrical structures in the cavity optical-mechanical micro-gyroscope significantly impacts the measurement accuracy and stability of the gyroscope.

[0004] By using piezoelectric ceramics (PZT) to drive the gyroscope instead of the traditional electrical structure of driving comb teeth, gold electrodes, and leads, and using a cavity optomechanical system and waveguide coupling to form an optical structure for detection, the cross-coupling between the optical and electrical structures can be largely suppressed, while simplifying the manufacturing process, thereby further improving the measurement accuracy and stability of the cavity optomechanical microgyroscope. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems and provide a high-precision cavity optical gyroscope based on piezoelectric ceramic drive that can solve the problems of complex manufacturing process and cross-coupling of optical and electrical structures in the driving mode of conventional cavity optical gyroscopes.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a high-precision cavity optical gyroscope driven by piezoelectric ceramics, comprising a fixed column, a mechanical structure, an optical structure, piezoelectric ceramics, and a base. The fixed column is located at the four corners of the mechanical structure, the optical structure is located at both ends of the mechanical structure, and the piezoelectric ceramics and the base are located at the lower part of the mechanical structure. The optical structure includes a cavity optical system and a waveguide structure, which are coupled. The cavity optical system consists of a pair of optical microcavities, wherein the optical microcavities are two-dimensional photonic crystals or whispering-gallery mode microcavities, Fabry-Perot optical microcavities, or one-dimensional nanocantilever beams. The mechanical structure includes a mass block and a support beam, wherein the mass block includes a core mass block, a detection mass block, and a driving mass block. The core mass block is located at the center of the gyroscope and is connected to the driving mass block and the detection mass block respectively through cantilever arms. The support beam includes a driving support beam and a detection support beam.

[0007] Preferably, the piezoelectric ceramic and the base are bonded together by a low-temperature adhesive bonding or annealing crystallization process, that is, the piezoelectric ceramic and the mechanical and optical structures are fixed together.

[0008] Preferably, the optical structure and the mechanical structure are active layers suspended on the base, and the two parts are directly connected.

[0009] Preferably, the piezoelectric ceramic is electrically connected to the signal generator as the source of acceleration in the driving direction. Through an external voltage, mechanical shearing motion is applied in the driving direction of the cavity optical micro gyroscope, causing the driving mass block and the core mass block to perform simple harmonic motion along the driving direction.

[0010] Preferably, the optical structure and the detection mass block constitute the detection structure of the cavity optical-mechanical micro-gyroscope, and the cavity optical-mechanical system of the optical structure is distributed on both sides of the gap between the detection mass block and the outer periphery of the structure.

[0011] Preferably, the piezoelectric ceramic applies mechanical shearing motion to the base of the cavity optical micro gyroscope, so that the core mass block in the mechanical structure vibrates with the base at the same frequency, with stable amplitude and slightly lagging phase. The frequency of the voltage applied to the piezoelectric ceramic, the frequency of the shearing vibration generated by the piezoelectric ceramic through the inverse piezoelectric effect, and the frequency of the mechanical oscillator of the gyroscope are consistent.

[0012] The beneficial effects of this invention are:

[0013] 1. The high-precision cavity optical gyroscope based on piezoelectric ceramic drive provided by this invention uses PZT drive. Compared with the traditional cavity optical gyroscope using electrostatic drive push-pull comb drive method, by eliminating the traditional electrical structure and retaining the optical and mechanical structure, the coupling between the electrical structure and the optical structure is greatly reduced, the detection accuracy of the cavity optical gyroscope is improved, and the manufacturing process is simplified.

[0014] 2. The piezoelectric constant of PZT selected in this invention is among the leading ceramic piezoelectric materials. It has high piezoelectric response, good temperature stability and controllability. Using PZT-5H, PZT-5A, PSN-PNN-PZT to drive commonly used models of wafer-level bonding gyroscopes has a more obvious driving effect than using other piezoelectric materials, and meets the requirements of cavity optical force gyroscopes for driving amplitude accuracy and phase fidelity.

[0015] 3. The PZT thin film selected in this invention is easy to bond with SOI wafers through processes such as low-temperature adhesive bonding or annealing crystallization. Compared with traditional cavity optical micro gyroscopes, it is smaller in size, more stable, and easier to integrate into inertial navigation systems.

[0016] 4. The present invention uses a cavity optical-mechanical system composed of optical microcavities, combined with waveguides and detection mass blocks to form a detection structure. The optical microcavities are fabricated using micro-nano-level technology, which has the advantages of high quality factor and small volume, and can achieve high-sensitivity optical detection.

[0017] 5. The present invention employs a multi-point anchoring and cavity optical force system design to enhance structural stability and anti-interference capability of signal processing, thereby achieving high-precision angular velocity measurement.

[0018] 6. Compared with traditional MEMS gyroscopes, the novel structure gyroscope of this invention has significant advantages in terms of sensitivity, stability, environmental adaptability, and integration, and is suitable for fields with extremely high accuracy requirements such as inertial navigation, attitude control, and motion measurement.

[0019] 7. This invention solves the problems of complex manufacturing processes and cross-coupling of optical and electrical structures in the driving methods of conventional cavity optical micro-gyroscopes. This invention can effectively improve the measurement accuracy of micro-gyroscopes, simplify the driving methods of cavity optical micro-gyroscopes, and make them more convenient and accurate in practical applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the high-precision cavity optical micro-gyroscope driven by piezoelectric ceramics according to the present invention;

[0021] Figure 2 This is a schematic diagram illustrating the working principle of the present invention.

[0022] Explanation of reference numerals in the attached diagram: 1. Fixed column; 2. Mechanical structure; 3. Optical structure; 4. Piezoelectric ceramic; 5. Base. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0024] like Figures 1 to 2As shown, the high-precision cavity optical-mechanical micro-gyroscope based on piezoelectric ceramic drive provided by the present invention includes a fixed column 1, a mechanical structure 2, an optical structure 3, a piezoelectric ceramic 4, and a base 5. The fixed column 1 is located at the four corners of the mechanical structure 2, the optical structure 3 is located at both ends of the mechanical structure 2, and the piezoelectric ceramic 4 and the base 5 are located at the lower part of the mechanical structure 2. The optical structure 3 includes a cavity optical-mechanical system and a waveguide structure, which are coupled. The cavity optical-mechanical system consists of a pair of optical microcavities, wherein the optical microcavities are two-dimensional photonic crystals or whispering-gallery mode microcavities, Fabry-Perot optical microcavities, or one-dimensional nanocantilever beams. The mechanical structure 2 includes a mass block and a support beam, wherein the mass block includes a core mass block, a detection mass block, and a driving mass block. The core mass block is located at the center of the gyroscope and is connected to the driving mass block and the detection mass block respectively through cantilever arms. The support beam includes a driving support beam and a detection support beam.

[0025] In this invention, the piezoelectric ceramic 4 is PZT. Commonly used piezoelectric ceramics 4, such as PZT-5H, PZT-5A, and PSN-PNN-PZT, can achieve wafer-level bonding. The cavity optical system and waveguide structure are existing structures, and the connection methods of the mass block and support beam are existing mature technologies.

[0026] The mass block of mechanical structure 2 consists of two parts: a driving mass block and a detection mass block. The two are rigidly connected by a U-shaped beam embedded inside the detection mass block. This nested structure can effectively isolate the motion coupling between the driving mode and the detection mode, prevent the vibration in the driving direction from being transmitted to the detection direction, and thus reduce the interference of orthogonal error on the detection signal.

[0027] The driving mass block, as the core carrier of vibration excitation, works in conjunction with the piezoelectric ceramic driving structure 4 to achieve precise vibration output. A two-dimensional photonic crystal microcavity, namely optical structure 3 in Figure 1, is symmetrically arranged on the upper and lower parts of the detection mass block to form a differential detection configuration, which can effectively cancel common-mode noise such as temperature drift and external vibration, and further improve the signal-to-noise ratio of the detection signal.

[0028] The piezoelectric ceramic 4 and the substrate 5 are bonded together using a low-temperature adhesive bonding or annealing crystallization process, thus fixing the piezoelectric ceramic 4 to the mechanical structure 2 and the optical structure 3. The substrate 5 is the supporting silicon layer in the SOI wafer.

[0029] The piezoelectric ceramic 4-drive structure uses a customized sandwich-type PZT as its drive core. It consists of three single, enlarged-area PZTs bonded together, and this special stacked structure allows it to drive a larger load, generating greater acceleration to meet the gyroscope's drive requirements and adapting to the vibration excitation needs of a single mass. The PZTs are bonded below the gyroscope's mechanical structure 2, with their shear motion direction precisely aligned with the gyroscope chip's drive direction, ensuring efficient transmission of driving force to the drive mass. The entire assembly is placed within a vacuum chamber to avoid the influence of air damping on the oscillator's vibration characteristics. Simultaneously, the power supply is connected to the external environment via a turntable pin, without interfering with the turntable's rotation.

[0030] The core mechanism by which the PZT drives the gyroscope to generate mechanical displacement signals is through the piezoelectric effect. It precisely converts the input voltage signal into controllable shear motion, thereby generating stable acceleration to drive the gyroscope oscillator to achieve target vibration. A voltage signal of specific frequency and amplitude is applied to the PZT by a signal generator. The PZT utilizes the piezoelectric effect to convert the voltage signal into controllable shear motion. The generated acceleration amplitude is directly proportional to the driving voltage amplitude and also directly proportional to the square of the driving voltage frequency. The acceleration frequency is completely consistent with the driving voltage frequency. The driving voltage parameters must be strictly matched to the resonant frequency of the gyroscope's driving mode. Through resonant driving, the oscillator achieves maximum driving displacement, laying the foundation for the subsequent generation and detection of Coriolis force.

[0031] Optical structure 3 and mechanical structure 2 are active layers suspended on base 5, and the two parts are directly connected.

[0032] Optical structure 3 employs a two-dimensional photonic crystal microcavity structure, which possesses advantages such as high Q value, narrow linewidth, and strong optical field confinement. For example... Figure 1 In the middle, the part pointed to by optical structure 3, where the parallelogram represents the microcavity and the line represents the waveguide.

[0033] Figure 1 The two-dimensional photonic crystal introduced in the optical structure 3 is a cavity-type two-dimensional photonic crystal with a triangular lattice. At the center of the structure, air holes are removed to load line defects, and then rectangular air grooves are introduced through etching to form the basic waveguide structure. Subsequently, the width is modulated by the minute displacement of the microcavity holes. Utilizing the change in refractive index distribution caused by the hole displacement, a high-Q-value microcavity is formed in a local region of the waveguide, while the positions of other holes remain unchanged, ensuring the periodicity of the structure and the optical field confinement effect. Its microcavity thickness is 250 nm, matching the device layer thickness in the SOI process, facilitating integrated fabrication. Operating in the communication C-band, near 1550 nm, through COMSOL finite element simulation and FDTD algorithm optimization, the final optical resonant wavelength is 1542.037 nm, with a quality factor (Q) as high as 102802. This high Q-value effectively reduces optical field loss and improves displacement detection sensitivity.

[0034] The piezoelectric ceramic 4 serves as the source of acceleration in the driving direction and is electrically connected to the signal generator. Through an external voltage, it applies mechanical shear motion in the driving direction of the cavity optical micro-gyroscope, causing the driving mass and core mass to undergo simple harmonic motion along the driving direction. The signal generator is a mature, existing technology product, model RIGOLD G4162.

[0035] The optical structure 3 and the detection mass block constitute the detection structure of the cavity optical force micro gyroscope. The cavity optical force system of the optical structure 3 is distributed on both sides of the gap between the detection mass block and the outer periphery of the structure.

[0036] The piezoelectric ceramic 4 applies mechanical shearing motion to the base of the cavity optical micro gyroscope, causing the core mass block in the mechanical structure 2 to vibrate with the same frequency, stable amplitude, and slightly lagging phase as the base. The frequency of the voltage applied to the piezoelectric ceramic 4, the frequency of the shearing vibration generated by the piezoelectric ceramic 4 through the inverse piezoelectric effect, and the frequency of the gyroscope's mechanical oscillator vibration are all the same.

[0037] See Figure 2 The detection principle of the high-precision cavity optical micro-gyroscope based on piezoelectric ceramic drive described in this invention is as follows:

[0038] First, under the influence of the Coriolis force, the coupling system of the microcavity optomechanical structure optical gyroscope proposed in this project will satisfy the following set of coupling equations:

[0039] (1-1)

[0040] (1-2)

[0041] Equation (1-1) describes the optical resonance mode in the microcavity optomechanical structure, and equation (1-2) describes the mechanical oscillation mode. This refers to the optical radiation pressure / optical gradient force generated in the microcavity. This refers to the thermal noise force of the system. The Coriolis force generated by the applied angular velocity... Under the influence of the microcavity optical-mechanical structure, the detection mass block and the connected cantilever have an additional displacement:

[0042] (1-3)

[0043] Therefore, the total displacement of the mass block under laser excitation, Coriolis force, and thermal noise contribution is measured. for:

[0044] (1-4)

[0045] Substituting this into equations (1-1) and (1-2), we can obtain the relationship between the mechanical oscillation frequency of the detection mass block and the laser parameters (amplitude, wavelength) and angular velocity in the microcavity photomechanical system:

[0046] (1-5)

[0047] in, To excite the laser's operating frequency, This is the resonant frequency of the optical mode in the optical microcavity. Optomechanical coupling rate, The photon energy within the cavity, This refers to the optical cavity attenuation rate. For a well-designed and manufactured microcavity optomechanical system, the mass of the detection mass block, the optical resonance characteristics of the microcavity, the mechanical resonance characteristics of the detection mass block, and the optomechanical coupling rate can be determined.

[0048] Therefore, under fixed excitation laser wavelength and amplitude, and with fixed drive conditions, the final oscillation frequency of the detection mass changes only with the magnitude and direction of the applied angular velocity. Thus, the magnitude and direction of the angular velocity can be characterized by measuring the offset of the detection mass's oscillation frequency. Furthermore, as shown in equation (1-5), the angular velocity detection sensitivity of the optical gyroscope in a microcavity optomechanical system can be improved by increasing the laser power, among other things. This effect is called the photoelastic effect in a cavity optomechanical system.

[0049] This invention discloses a high-precision cavity optical-mechanical micro-gyroscope driven by piezoelectric ceramic (PZT). It employs a mechanical structure design of "single mass block + decoupling frame," comprising a driving mass block, a detection mass block, and a core mass block. The mechanical oscillator is elastically supported and suspended from the base by a folded beam, reducing interference from base vibration. The driving structure uses a customized sandwich-type PZT (composed of three single-piece enlarged-area PZTs stacked together to meet the vibration excitation requirements of the single mass block), which is adhered to the bottom of the mechanical structure. Its shear motion direction is precisely aligned with the driving direction, and it is assembled within a vacuum cavity to avoid the influence of air damping. The optical detection structure uses a triangular lattice cavitation type two-dimensional photonic crystal micro-gyroscope. The cavity is constructed by removing specific air holes and loading line defects in the middle of the structure and etching rectangular air grooves to form waveguides. A high-Q microcavity is then formed by modulating the displacement of the holes in the central region. These microcavities are symmetrically arranged on the upper and lower parts of the detection mass block to form a differential configuration to cancel common-mode noise. In terms of manufacturing, a peel-off process is used, and PZT and SOI wafers are bonded together using low-temperature adhesive bonding or annealing crystallization processes to form a three-layer configuration of "PZT-base-optical / mechanical structure" for wafer-level integration. During detection, based on the Coriolis effect, an applied angular velocity causes additional displacement of the detection mass block. The high-Q characteristic of the microcavity is used to capture displacement changes, and the magnitude and direction of the angular velocity are characterized by measuring the frequency offset. Compared with cavity optical gyroscopes driven by electrostatic combs, the driving method proposed in this patent can largely suppress the cross-coupling between the optical and electrical structures, while simplifying the manufacturing process, thereby improving the detection accuracy and stability of the gyroscope.

[0050] This invention discloses a high-precision cavity optical gyroscope driven by piezoelectric ceramic (PZT), primarily applied to novel high-precision micro-gyroscopes based on cavity optical systems. Based on the inverse piezoelectric effect of PZT, mechanical shearing motion is applied in the driving direction of the cavity optical gyroscope through an external voltage, thereby achieving actuation. An optical structure composed of a cavity optical system and a waveguide is used for angular velocity detection, utilizing its high sensitivity and anti-electromagnetic interference characteristics to achieve micro-nano-level displacement detection. The overall structure of the cavity optical gyroscope is simplified. By eliminating traditional electrical structures and retaining optical and mechanical structures, the coupling between electrical and optical structures is greatly reduced, improving the detection accuracy of the cavity optical gyroscope. The ease of monolithic integration of PZT simplifies the fabrication and integration process of the cavity optical gyroscope. Compared with the traditional cavity optical gyroscope's electrostatically driven push-pull comb method, the cavity optical gyroscope structure of this invention has significant advantages in stability, environmental adaptability, and integration, making it suitable for fields with extremely high precision requirements such as inertial navigation, attitude control, and motion measurement.

[0051] 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 high-precision cavity optical force micro-gyroscope based on piezoelectric ceramic driving, characterized in that: It includes fixed column (1), mechanical structure (2), optical structure (3), piezoelectric ceramic (4) and base (5), fixed column (1) is located in the four corner position of mechanical structure (2), optical structure (3) is located in the both ends of mechanical structure (2), piezoelectric ceramic (4) and base (5) are located in the lower part position of mechanical structure (2);The optical structure (3) includes cavity optical force system and waveguide structure, and the cavity optical force system and the waveguide structure are coupled, the cavity optical force system is formed by a pair of optical microcavity, wherein the optical microcavity is two-dimensional photonic crystal or echo wall mode microcavity, Fabry-Perot optical microcavity, one-dimensional nanometer suspension wall beam;The mechanical structure (2) includes mass block and support beam, wherein the mass block includes core mass block, detection mass block and driving mass block, the core mass block is located in the center part of the gyroscope, and is connected with the driving mass block and the detection mass block through the suspension beam arm respectively, the support beam includes driving support beam and detection support beam.

2. The high-precision cavity optical force micro-gyroscope based on piezoelectric ceramic driving according to claim 1, characterized in that: The piezoelectric ceramic (4) and the base (5) are bonded by low temperature glue or annealing crystallization process, that is, the piezoelectric ceramic (4) and the mechanical structure (2) and the optical structure (3) are fixed.

3. The high-precision cavity optical force micro- gyroscope based on piezoelectric ceramic driving according to claim 1, characterized in that: The optical structure (3) and the mechanical structure (2) belong to the active layer suspended on the base (5), and the two parts are directly connected.

4. The piezoelectric ceramic driving based high-precision cavity optical force micro- gyroscope according to claim 1, characterized in that: The piezoelectric ceramic (4) is electrically connected as the source of driving direction acceleration and signal generator, and through the external voltage, mechanical shear motion is applied in the driving direction of the cavity optical force microgyroscope, so that the driving mass block and the core mass block do simple harmonic vibration along the driving direction.

5. The piezoelectric ceramic driving based high-precision cavity optical force micro- gyroscope according to claim 1, characterized in that: The optical structure (3) and the detection mass block constitute the detection structure of the cavity optical force microgyroscope, and the cavity optical force system of the optical structure (3) is distributed on both sides of the gap between the detection mass block and the structure periphery.

6. The piezoelectric ceramic driving based high-precision cavity optical force micro- gyroscope according to claim 1, characterized in that: The piezoelectric ceramic (4) applies mechanical shear motion on the base of the cavity optical force microgyroscope, so that the core mass block in the mechanical structure (2) and the base do vibration with consistent vibration frequency, stable amplitude and slightly lagging phase, the frequency of the voltage applied on the piezoelectric ceramic (4) is consistent with the frequency of the shear vibration generated by the piezoelectric ceramic (4) through the inverse piezoelectric effect and the frequency of the mechanical vibrator vibration of the gyroscope.

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