A method to enhance the modal amplitude and temperature sensitivity of microresonators by using internal resonance

Abstract

The present invention relates to a method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance, and belongs to the field of micro-electromechanical system control technology, including measuring the fundamental mode and high-frequency mode of a thin film microresonator under a detection voltage; applying a pump voltage at the fundamental mode to enhance the amplitude of the high-frequency mode; while applying the pump voltage at the fundamental mode, using a laser to heat the thin film microresonator to complete the temperature detection. The present invention only requires a signal generator to output a low-frequency and low-voltage pump signal to modulate the thin film microresonator, so as to enhance the amplitude of the high-frequency mode of the thin film microresonator and improve the temperature sensitivity, and has a simple principle and is easy to operate.

Description

Technical Field

[0001] The present invention relates to a method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance, specifically a method for improving the high-frequency modal amplitude and temperature sensitivity of a thin film microresonator by utilizing a 1:3 internal resonance phenomenon, and belongs to the technical field of micro-electromechanical system control. Background Art

[0002] Micro-electro-mechanical system (MEMS) is a technology that integrates multiple functions into micro devices, covering multiple modules such as structure, sensing, execution, signal processing, control, communication and power supply. As a key component of MEMS, microresonators are designed in various structural forms due to their application requirements under different working conditions and performance requirements, such as single-ended cantilever beams, double-ended fixed beams, disks, and thin film resonators.

[0003] Microresonators have multiple resonant modes at the same time. Compared with low-frequency modes, high-frequency modes have the following advantages: 1. High quality factor. A higher quality factor means that the mode has lower energy loss and stronger stability. 2. High sensitivity. High-frequency modes usually have greater frequency shift and displacement response to external disturbances. 3. High resolution. The spectrum of high-frequency modes is narrower and they also respond well to weak disturbances. However, how to effectively excite high-frequency modes has always been a difficult problem to be solved. Since the amplitude of high-frequency modes is more complex, if high-frequency modes are directly excited, high-frequency voltages need to be applied, which not only poses a severe challenge to the stability of the device, but also significantly increases the power consumption of the system. In addition, the amplitude of high-frequency modes is usually low, which makes detection more difficult. Therefore, it is particularly important to develop a simple excitation method to enhance the amplitude of high-frequency modes of microresonators. At present, there are several ways to increase the amplitude of high-frequency modes of microresonators:

[0004] 1. Add a series resonant circuit

[0005] Adding an inductor L and a capacitor C to the outside of the microresonator forms a series LC resonant circuit. Taking advantage of the fact that the current of the resonant circuit is the largest when it resonates, the voltage applied to the resonator is amplified to achieve the amplification of the modal amplitude of the resonator. Md.N.Jaber et al. used this method to achieve amplitude amplification of a porous plate microresonator. However, the biggest disadvantage of this method is that the external LC series resonant circuit makes the entire system bloated, which goes against the original development direction of the microresonator and makes integrated miniaturization difficult.

[0006] 2. Use laser heating

[0007] Thermal effects can change the physical properties of materials and thus increase the amplitude of the microresonator mode. M. Zalalutdinov et al. used lasers to heat a disk microresonator, changing the effective spring constant of the microresonator and increasing the amplitude of the resonator mode. However, this method has the disadvantages of high energy consumption, complex operation and poor precision.

[0008] 3. Dual voltage excitation

[0009] Microresonators usually have multiple modes. Wen Zhao et al. amplified the amplitude of the low-amplitude mode by applying voltage to the two vibration modes of the microcantilever beam resonator at the same time. However, this method requires high voltage to drive the microresonator, and the simultaneous application of two high voltages can easily cause mechanical fatigue and damage to the microresonator.

[0010] Therefore, it is an urgent problem to realize the amplitude enhancement of the high-frequency modes of microresonators using a simple and easy method. Summary of the invention

[0011] In view of the shortcomings of the prior art, the present invention provides a method for enhancing the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance. Only a signal generator is required to output a low-frequency and low-voltage pump signal to modulate the thin film microresonator, thereby achieving the enhancement of the amplitude of the high-frequency mode of the thin film microresonator and the improvement of the temperature sensitivity. The principle is simple and the operation is easy.

[0012] The present invention adopts the following technical solution:

[0013] A method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance comprises the following steps:

[0014] S1: The fundamental mode and high-frequency mode of the thin film microresonator are measured under the detection voltage;

[0015] S2: Apply pump voltage to the fundamental mode to enhance the amplitude of the high-frequency mode;

[0016] S3: While applying a pump voltage at the fundamental mode, the thin film microresonator is heated using a laser to detect the temperature.

[0017] Preferably, the implementation process of step S1 is:

[0018] S11: Align the probe of the laser Doppler vibrometer to the center of the silicon nitride film of the thin film microresonator, emit a laser, and use the laser Doppler vibrometer to complete the frequency scanning and vibration signal collection of the thin film microresonator;

[0019] S12: The phase-locked amplifier is connected to the piezoelectric film through a wire, and the thin film microresonator is pasted on the piezoelectric film. The detection voltage generated by the phase-locked amplifier is applied to the thin film microresonator through the piezoelectric film to stimulate the vibration of the thin film microresonator. The displacement and velocity signals generated by the thin film microresonator during vibration are collected by the probe of the laser Doppler vibrometer and converted into electrical signals through the controller of the laser Doppler vibrometer. The electrical signals are input into the computer after noise reduction processing by the phase-locked amplifier. The frequency response curve of the thin film microresonator can be observed in the computer software. The first resonance peak in the frequency response curve is the fundamental mode f1 of the thin film microresonator, and the resonance peak at three times the fundamental mode frequency is the high-frequency mode f2.

[0020] Preferably, in step S11, the wavelength of the emitted laser is 633 nm;

[0021] In S12, the magnitude of the detection voltage is 3 mV, and the magnitude of the detection voltage can be controlled by computer software. The detection voltage of 3 mV can ensure that no nonlinear phenomenon occurs when the thin film microresonator is effectively excited.

[0022] Preferably, in step S12, the determined fundamental mode f1 is 268.878 kHz, the high frequency mode f2 is 806.688 kHz, and the frequency ratio is 1:3.

[0023] Preferably, the implementation process of step S2 is:

[0024] S21: Use the signal generator to output frequency f p The voltage signal is the pump voltage V p , pump voltage V p The frequency f p The pump voltage V is equal to the frequency f1 of the fundamental mode of the thin film microresonator. p The size of is gradually increased from 50mV to 500mV, and the pump voltage is applied to the thin film microresonator through the piezoelectric sheet;

[0025] S22: Use a lock-in amplifier to output a detection voltage of 3 mV. The displacement and velocity signals generated by the thin film microresonator during vibration are collected by the probe of the laser Doppler vibrometer and converted into electrical signals through the controller of the laser Doppler vibrometer. The electrical signals are input into the computer after noise reduction processing by the lock-in amplifier. The frequency response curve of the high-frequency mode f2 of the thin film microresonator can be observed in the computer software.

[0026] S23: By observing the frequency response curve of the high-frequency mode f2 of the thin film microresonator, the amplitude of the high-frequency mode f2 of the thin film microresonator increases from the initial A0 to A0', and the amplitude increases by ΔA = A0'-A0, thereby enhancing the amplitude of the high-frequency mode f2 of the thin film microresonator.

[0027] Preferably, in step S21, the pump voltage V p The process of gradually increasing from 50mV to 500mV is: 50mV, 100mV, 200mV, 300mV, 400mV, 500mV;

[0028] In step S23, A0 is 0.199 mV, A0' is 2.313 mV, and the amplitude is increased by 11.623 times, thereby achieving enhancement of the high-frequency modal amplitude of the thin film microresonator.

[0029] Preferably, the implementation process of step S3 is:

[0030] S31: Use the signal generator to output frequency f p , size is V p The voltage signal, pump voltage V p The frequency f p The pump voltage V is equal to the frequency f1 of the fundamental mode of the thin film microresonator. p The magnitude is 200mV, and the pump voltage is applied to the thin film microresonator through the piezoelectric sheet;

[0031] S32: irradiating the thin film microresonator with laser light emitted by the heating laser to heat the thin film microresonator, detecting the temperature of the thin film microresonator in real time through a temperature sensor, and gradually increasing the temperature of the thin film microresonator from 28° C. to 36° C.;

[0032] S33: Use a lock-in amplifier to output a detection voltage, the magnitude of the detection voltage is 3mV, the vibration signal of the thin film microresonator collected by the laser Doppler vibrometer is processed by the lock-in amplifier for noise reduction, and then transmitted to the computer, and analyzed by the frequency scanning module in the computer software, that is, the frequency response curves of the basic mode f1 and the high-frequency mode f2 are obtained;

[0033] S34: It can be seen from the frequency response curves of the fundamental mode f1 and the high-frequency mode f2 that the high-frequency mode amplitude of the thin film microresonator has been significantly amplified and its sensitivity to temperature has also been improved.

[0034] Preferably, in step S32, the process of gradually increasing the temperature of the thin film microresonator from 28°C to 36°C is: 28°C, 30°C, 32°C, 34°C, 36°C. After the laser heats the thin film microresonator to the specified temperature, the frequency measurement is completed without stopping the irradiation, and then the laser power is continuously increased to make the thin film microresonator reach the next temperature;

[0035] In step S34, the temperature sensitivity of f1 of the fundamental mode is 270.65 kHz / °C, and the temperature sensitivity of f2 of the high frequency mode is 859.45 kHz / °C, and the temperature sensitivity is increased by 3.18 times.

[0036] Preferably, the device is realized by utilizing internal resonance to enhance the modal amplitude and temperature sensitivity of the microresonator, the device comprising a thin film microresonator, a piezoelectric sheet, a heating laser, a laser Doppler vibrometer, a lock-in amplifier, a signal generator and a computer, the laser Doppler vibrometer comprising a probe and a controller, the probe is used to emit a laser, align the laser to the center of the thin film microresonator, and the controller is used to convert the displacement and velocity signals of the thin film microresonator detected by the probe into electrical signals;

[0037] The laser Doppler vibrometer, the phase-locked amplifier, and the piezoelectric sheet are connected in sequence, and the thin film micro-resonator is pasted on the piezoelectric sheet; the phase-locked amplifier is connected to a computer, the signal generator is connected to the piezoelectric sheet, and the thin film micro-resonator and the piezoelectric sheet are both placed in a vacuum chamber;

[0038] The laser light emitted by the heating laser is aimed at the thin film microresonator to heat the thin film microresonator.

[0039] Preferably, a displacement stage is provided at the bottom of the vacuum chamber to adjust the position of the vacuum chamber and thus adjust the position of the thin film microresonator; the vacuum degree of the vacuum chamber is 10-2 mbar;

[0040] The thin film microresonator comprises a single crystal silicon substrate and a silicon nitride film grown on the single crystal silicon substrate by chemical vapor deposition, wherein the size of the silicon nitride film is: 500 μm in length, 500 μm in width, and 100 nm in thickness;

[0041] The piezoelectric piece is a circular ceramic piece made of lead zirconate titanate with a piezoelectric coefficient d33 of 350 pmV. -1 The dimensions of the piezoelectric sheet are: 30 mm in diameter and 2 mm in thickness.

[0042] The lock-in amplifier is a 7265 model produced by Signal Recovey, with a frequency range of 0.001 Hz-250 kHz and a voltage sensitivity of 2 nV-1 V, which is used to output the detection voltage and process the vibration signal of the thin film microresonator collected by the laser Doppler vibrometer and display it on the computer through computer software;

[0043] The laser Doppler vibrometer is OFV-5000 produced by Polytec, which emits a laser spot of 10 μm and is used to detect the displacement and velocity changes of the thin film microresonator;

[0044] The heating laser is a DL-450 semiconductor laser produced by Shanghai Xilong Optoelectronics Company.

[0045] The signal generator is 33220A produced by Agilent, which is used to apply the pump voltage.

[0046] For any details not provided in the present invention, please refer to the prior art.

[0047] The beneficial effects of the present invention are:

[0048] 1. The present invention only needs a signal generator to output a low-frequency and low-voltage pump signal to modulate the thin film microresonator, so as to enhance the amplitude of the high-frequency mode of the thin film microresonator and improve the temperature sensitivity. The principle is simple and the operation is easy.

[0049] 2. The present invention utilizes the 1:3 internal resonance phenomenon for the first time and applies a pump voltage in the low-frequency mode to achieve amplitude enhancement of the high-frequency vibration mode. The high-frequency vibration mode of the microresonator has the advantages of high quality factor and high sensitivity. Increasing the amplitude of the high-frequency mode can improve the resolution of the mode, making the mode easier to detect, which is of great significance for subsequent practical applications.

[0050] 3. The present invention successfully completes temperature detection by amplifying the high-frequency mode amplitude. Compared with the basic mode, the temperature sensitivity of the high-frequency mode is significantly improved.

[0051] 4. The non-contact control method adopted by the present invention has high precision, and the entire device works at a low voltage, causing little damage to the resonator and extending its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0053] Figure 1 A schematic diagram of a device for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to the present invention;

[0054] Figure 2 An optical photograph of a thin film microresonator of the present invention;

[0055] Figure 3 is the frequency response diagram of the fundamental mode of the thin film microresonator under the detection voltage;

[0056] Figure 4 The frequency response diagram of the high-frequency mode of the thin film microresonator under the detection voltage;

[0057] Figure 5 Schematic diagram of the principle of achieving high-frequency modal amplitude enhancement of thin-film microresonators;

[0058] Figure 6The amplitude change of the high-frequency mode when the pump voltage is applied to the fundamental mode, where the curves from top to bottom are the cases where the pump voltage is 50mV, 100mV, 200mV, 300mV, 400mV, and 500mV;

[0059] Figure 7 A comparison chart of the temperature sensitivity of the fundamental mode and the high-frequency mode;

[0060] In the figure, 1- piezoelectric piece, 2-thin film microresonator, 3-laser, 4-probe, 5-vacuum chamber, 6-controller, 7-locked amplifier, 8-signal generator, 9-computer, 10-heating laser. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the implementation of this specification, but are not limited to this. Anything not fully described in the present invention shall be based on the conventional technology in the art.

[0062] Example 1

[0063] A method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance comprises the following steps:

[0064] S1: The fundamental mode and high-frequency mode of the thin film microresonator are measured under the detection voltage;

[0065] S2: Apply pump voltage to the fundamental mode to enhance the amplitude of the high-frequency mode;

[0066] S3: While applying a pump voltage at the fundamental mode, the thin film microresonator is heated using a laser to detect the temperature.

[0067] Example 2

[0068] A method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance is as described in Example 1, except that the implementation process of step S1 is as follows:

[0069] S11: Align the probe of the laser Doppler vibrometer to the center of the silicon nitride film of the thin film microresonator, and emit a laser with a wavelength of 633nm. After focusing the laser, align it to the center of the thin film microresonator. The effect of laser focusing can be observed through a CCD image sensor. The CCD image sensor is a semiconductor device built into the probe of the laser Doppler vibrometer. It can convert optical images into digital signals. Connecting it to a display can clearly display the position of the thin film microresonator and the laser focus point, so as to intuitively observe the focusing of the laser. Use the laser Doppler vibrometer to complete the frequency scanning of the thin film microresonator and the collection of vibration signals;

[0070] S12: The lock-in amplifier is connected to the piezoelectric sheet through a wire. The thin film micro-resonator is pasted on the piezoelectric sheet. The voltage output by the lock-in amplifier can be controlled by a computer connected to the lock-in amplifier. The detection voltage generated by the lock-in amplifier is applied to the thin film micro-resonator through the piezoelectric sheet to stimulate the thin film micro-resonator to vibrate. The detection voltage V probe The magnitude of is 3mV. The role of the detection voltage is to drive the thin film microresonator to vibrate. The displacement and velocity signals generated by the thin film microresonator during vibration are collected by the probe of the laser Doppler vibrometer and converted into electrical signals through the controller of the laser Doppler vibrometer. The electrical signals are input into the computer after noise reduction processing by the phase-locked amplifier. The frequency response curve of the thin film microresonator can be observed in the computer software. The first resonance peak in the frequency response curve is the fundamental mode f1 of the thin film microresonator. The resonance peak at three times the fundamental mode frequency is the high-frequency mode f2. Figure 3 is the frequency response curve of the fundamental mode of the thin film microresonator, Figure 4 This is the frequency response curve of the high-frequency mode of the thin film microresonator. The frequency f1 of the fundamental mode is 268.878 kHz, and the frequency f2 of the high-frequency mode is 806.688 kHz.

[0071] The laser Doppler vibrometer used in step S11 is a non-contact optical sensor, and the working principle of the instrument is the Doppler effect of laser. The laser emitted by the probe of the laser Doppler vibrometer irradiates the vibrating thin film microresonator, and the reflected laser will undergo frequency shift due to the Doppler effect. The displacement and velocity of the thin film microresonator can be calculated by the frequency difference and phase difference between the reflected light and the incident light. After being processed by the laser Doppler vibrometer controller, the electrical signal can be output to the lock-in amplifier.

[0072] The phase-locked amplifier used in step S12 is an analog Fourier transformer, which eliminates noise signals and improves the signal-to-noise ratio by performing Fourier transform on the electrical signal input by the Doppler vibrometer, and displays the result on the computer.

[0073] Example 3

[0074] A method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance is as described in Example 2, except that the implementation process of step S2 is as follows:

[0075] S21: Use the signal generator to output frequency f p The voltage signal is the pump voltage V p , pump voltage V p The frequency f p The pump voltage V is equal to the frequency f1 of the fundamental mode of the thin film microresonator. pThe size of increases in sequence, the increasing process is: 50mV, 100mV, 200mV, 300mV, 400mV, 500mV, the pump voltage is applied to the thin film microresonator through the piezoelectric sheet;

[0076] S22: Use a lock-in amplifier to output a detection voltage of 3 mV. The displacement and velocity signals generated by the thin film microresonator during vibration are collected by the probe of the laser Doppler vibrometer and converted into electrical signals through the controller of the laser Doppler vibrometer. The electrical signals are input into the computer after noise reduction processing by the lock-in amplifier. The frequency response curve of the high-frequency mode f2 of the thin film microresonator can be observed in the computer software. The frequency range is set to 805 kHz to 809 kHz. Figure 6 That is, it is the frequency response curve of the high-frequency mode f2 of the thin film microresonator when the pump voltage is continuously increased in the fundamental mode;

[0077] S23: By observing the frequency response curve of the high-frequency mode f2 of the thin film microresonator, the amplitude of the high-frequency mode f2 of the thin film microresonator increases from the initial A0 to A0', and the amplitude increases by ΔA = A0'-A0, thereby enhancing the amplitude of the high-frequency mode f2 of the thin film microresonator.

[0078] from Figure 4 It can be seen that the initial amplitude A0 is 0.199mV. Figure 6 It can be seen that the amplitude increase is the largest under the pump voltage of 200mV, A0' is 2.313mV, and the amplitude increases by 11.623 times, achieving the enhancement of the high-frequency mode amplitude of the thin film microresonator.

[0079] The process of implementing this method can be understood from spectroscopy. When a particle absorbs photons of the corresponding frequency and resonates, a characteristic peak will be generated in the spectrum. In experiments, the behavior of a group of particles is usually observed, and then there will be two different situations: uniform broadening and non-uniform broadening:

[0080] 1. Uniform broadening: In a group of particles, it is assumed that the spectral lines of each particle are the same. When a particle resonates, other particles also contribute to the spectral line of the particle in the same way, and the final spectral line presents a typical Lorentz peak shape.

[0081] 2. Non-uniform broadening: In a group of particles, the spectral line shape of each particle will be different due to the different physical environment of each particle. When a particle resonates, other particles will contribute to the spectral line of the particle according to a certain probability distribution, and the final spectral line will present a Gaussian peak shape. The broadening caused by the Doppler effect is a typical non-uniform broadening. The Doppler effect refers to the change in the wavelength of the radiation of an object due to the relative motion between the wave source and the observer. Therefore, when the movement speeds of each particle are inconsistent, Doppler broadening may occur.

[0082] In the present invention, the two modes of the thin film microresonator can be analogized to two particles. When no pump voltage is applied and only a low detection voltage is applied, the two modes can be regarded as independent of each other. At this time, the frequency response of each mode presents a typical Lorentz peak shape, which is consistent with the theory of uniform broadening. When the pump voltage is applied, the independence between the modes is broken, and the response of a single mode is no longer independent. It will be affected by other modes. This process can be analogized to Doppler broadening. The whole process is like Figure 5 shown.

[0083] Specifically, when a pump voltage is applied to the fundamental mode f1, as the pump voltage continues to increase, the frequency of the high-frequency mode f2 will move, that is, frequency pulling. This phenomenon has been reported in many papers. The reason for the frequency pulling is that the applied pump voltage causes a large deformation of the thin film microresonator, resulting in an increase in the internal tension of the thin film microresonator and the natural frequency of the thin film microresonator. It is expressed by the following formula:

[0084] ;

[0085] in F is the internal tension of the thin film microresonator, ρ is the density of silicon nitride film, h is the thickness of the silicon nitride film, a , b are the length and width of the silicon nitride film, i , j is a positive integer, representing the different resonant modes of the thin film microresonator.

[0086] When a pump voltage is applied to the fundamental mode, the fundamental mode will vibrate at a large amplitude. The tension inside the thin film microresonator increases under large deformation, and the modal frequency of the thin film microresonator is proportional to the internal tension, which leads to the frequency shift of the high-frequency mode. In addition, the increasing pump voltage will also cause the fundamental mode to produce a third harmonic, that is, a new mode is generated at three times the fundamental mode frequency. As the high-frequency mode continues to move toward the third harmonic, the detected high-frequency mode frequency response curve will no longer be a single Lorentz peak shape, but a Gaussian peak shape of the third harmonic and the high-frequency mode under the action of Doppler broadening.

[0087] In addition, since the frequencies of the high-frequency mode and the fundamental mode meet the integer ratio of 1:3, internal resonance occurs between the two modes. The internal resonance phenomenon refers to the situation in which the frequencies of two different vibration modes in the microresonator meet a certain proportional relationship and are coupled through nonlinear interactions, so that the vibration of one mode can affect the vibration of other modes. Under the condition of internal resonance, the energy transfer between the fundamental mode and the high-frequency mode becomes very efficient. The vibration of the fundamental mode excites the high-frequency mode through the coupling effect, that is, applying a pump voltage, resulting in a significant increase in the amplitude of the high-frequency mode.

[0088] Example 4

[0089] A method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance is as described in Example 3, except that the implementation process of step S3 is as follows:

[0090] S31: Use the signal generator to output frequency f p , size is V p The voltage signal, pump voltage V p The frequency f p The pump voltage V is equal to the frequency f1 of the fundamental mode of the thin film microresonator. p The magnitude is 200 mV (200 mV is the pump voltage determined in step S2 that can achieve maximum amplitude amplification), and the pump voltage is applied to the thin film microresonator through the piezoelectric sheet;

[0091] S32: irradiate the thin film microresonator with the laser emitted by the heating laser to heat the thin film microresonator, and detect the temperature of the thin film microresonator in real time through the temperature sensor, so that the temperature of the thin film microresonator is gradually increased, and the process is 28°C, 30°C, 32°C, 34°C, and 36°C. After the laser heats the thin film microresonator to the specified temperature, the frequency measurement is completed without stopping the irradiation, and then the laser power is continuously increased to make the thin film microresonator reach the next temperature;

[0092] S33: A phase-locked amplifier is used to output a detection voltage of 3 mV. The vibration signal of the thin film microresonator collected by the laser Doppler vibrometer is processed by the phase-locked amplifier for noise reduction and then transmitted to the computer. The frequency scanning module in the computer software is used for analysis to obtain the frequency response curves of the basic mode f1 and the high-frequency mode f2. Figure 7 Comparison curve of temperature sensitivity of basic mode f1 and high frequency mode f2;

[0093] S34: From Figure 7 It can be seen that the temperature sensitivity of the fundamental mode f1 is 270.65kHz / ℃, and the temperature sensitivity of the high-frequency mode f2 is 859.45kHz / ℃, and the temperature sensitivity is increased by 3.18 times.

[0094] The frequency of thin film microresonators is affected by temperature changes, which is mainly attributed to the temperature dependence of material properties, and the Young's modulus ( E ) and the coefficient of thermal expansion ( α ) two factors. When the laser irradiates the thin film microresonator, the thermal effect will reduce the Young's modulus of the material and thus reduce the resonant frequency of the thin film microresonator. In addition, thermal expansion will change the size of the thin film microresonator. Since the thermal expansion coefficient of the lower substrate silicon is larger than that of the upper silicon nitride film, the silicon deformation is larger, thereby stretching the upper silicon nitride film. Moreover, the Young's modulus of silicon nitride is larger than that of silicon and more difficult to deform. Therefore, thermal expansion will increase the internal tensile stress of the upper silicon nitride film, thereby increasing the resonant frequency of the thin film microresonator.

[0095] Combined with the experimental results, the effect of Young's modulus should be smaller than the increase in internal stress caused by thermal expansion between 28°C and 36°C, so the resonant frequency of the thin film microresonator shows an upward trend. F The relationship with temperature can be expressed as:

[0096] ;

[0097] in is the initial stress, is the thermal stress caused by thermal effect, , is the Young's modulus of silicon nitride, is the thermal expansion coefficient of silicon nitride, is the temperature change.

[0098] It can be concluded that when the temperature change is When , the resonant frequency of each mode of the thin film microresonator becomes:

[0099] ;

[0100] The temperature sensitivity of the thin film microresonator can be expressed as express:

[0101] ;

[0102] It can be seen that the temperature sensitivity of the thin film microresonator to temperature depends first on the parameters of the material itself, such as Young's modulus, thermal expansion coefficient and initial internal stress, and secondly strongly on the order of the mode, that is, , which means that the high frequency modes have the same temperature change In this case, a larger frequency shift will occur, that is, a higher temperature sensitivity.

[0103] Example 5

[0104] A method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance, as described in Example 4, except that the method is implemented by using a device for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance, as described in Example 4. Figure 1 As shown, the device includes a thin film microresonator 2, a piezoelectric sheet 1, a heating laser 10, a laser Doppler vibrometer, a phase-locked amplifier 7, a signal generator 8 and a computer 9. The laser Doppler vibrometer includes a probe 4 and a controller 6. The probe 4 is used to emit a laser 3 and align the laser 3 with the center of the thin film microresonator 2. The controller 6 is used to convert the displacement and velocity signals of the thin film microresonator 2 detected by the probe 4 into electrical signals.

[0105] The laser Doppler vibrometer, the phase-locked amplifier 7, and the piezoelectric sheet 1 are connected in sequence, and the thin film microresonator 2 is pasted on the piezoelectric sheet 1; the phase-locked amplifier 7 is connected to the computer 9, the signal generator 8 is connected to the piezoelectric sheet 1, and the thin film microresonator 2 and the piezoelectric sheet 1 are both placed in the vacuum chamber 5;

[0106] The laser light 3 emitted by the heating laser 10 is directed toward the thin film microresonator 2 to heat the thin film microresonator 2 .

[0107] A displacement stage is provided at the bottom of the vacuum chamber 5 for adjusting the position of the vacuum chamber 5 and thus adjusting the position of the thin film microresonator 2; the vacuum degree of the vacuum chamber 5 is 10-2 mbar;

[0108] like Figure 2 As shown, the thin film microresonator 2 includes a single crystal silicon substrate and a silicon nitride film grown on the single crystal silicon substrate by chemical vapor deposition. The size of the central window of the thin film microresonator (the same as the size of the silicon nitride film) is: 500 μm in length, 500 μm in width, and 100 nm in thickness;

[0109] The piezoelectric piece 1 is a circular ceramic piece made of lead zirconate titanate, and its piezoelectric coefficient d33 is 350 pmV. -1The dimensions of the piezoelectric sheet 1 are: 30 mm in diameter and 2 mm in thickness.

[0110] The lock-in amplifier 7 is a 7265 model produced by Signal Recovey, with a frequency range of 0.001 Hz-250 kHz and a voltage sensitivity of 2 nV-1 V, and is used to output a detection voltage and process the vibration signal of the thin film microresonator collected by the laser Doppler vibrometer and display it on the computer through computer software;

[0111] The laser Doppler vibrometer is OFV-5000 produced by Polytec, which emits a laser spot of 10 μm and is used to detect the displacement and velocity changes of the thin film microresonator;

[0112] The heating laser 10 is a DL-450 semiconductor laser produced by Shanghai Xilong Optoelectronics Company.

[0113] The signal generator 8 is 33220A produced by Agilent, which is used to apply the pump voltage.

[0114] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance, characterized in that: The steps include: S1: The fundamental mode and high-frequency mode of the thin film microresonator are measured under the detection voltage; S2: Apply pump voltage to the fundamental mode to enhance the amplitude of the high-frequency mode; S3: While applying a pump voltage at the fundamental mode, the thin film microresonator is heated by laser to complete the temperature detection; The implementation process of step S2 is: S21: Use the signal generator to output frequency f p The voltage signal is the pump voltage V p , pump voltage V p The frequency f p The pump voltage V is equal to the frequency f1 of the fundamental mode of the thin film microresonator. p The size of is gradually increased from 50mV to 500mV, and the pump voltage is applied to the thin film microresonator through the piezoelectric sheet; S22: Use a lock-in amplifier to output a detection voltage of 3 mV. The displacement and velocity signals generated by the thin film microresonator during vibration are collected by the probe of the laser Doppler vibrometer and converted into electrical signals through the controller of the laser Doppler vibrometer. The electrical signals are input into the computer after noise reduction processing by the lock-in amplifier. The frequency response curve of the high-frequency mode f2 of the thin film microresonator can be observed in the computer software. S23: By observing the frequency response curve of the high-frequency mode f2 of the thin film microresonator, the amplitude of the high-frequency mode f2 of the thin film microresonator increases from the initial A0 to A0', and the amplitude increases by ΔA = A0'-A0, thereby achieving the enhancement of the amplitude of the high-frequency mode f2 of the thin film microresonator; The implementation process of step S3 is: S31: Use the signal generator to output frequency f p , size is V p The voltage signal, pump voltage V p The frequency f p The pump voltage V is equal to the frequency f1 of the fundamental mode of the thin film microresonator. p The magnitude is 200mV, and the pump voltage is applied to the thin film microresonator through the piezoelectric sheet; S32: irradiating the thin film microresonator with laser light emitted by the heating laser to heat the thin film microresonator, detecting the temperature of the thin film microresonator in real time through a temperature sensor, and gradually increasing the temperature of the thin film microresonator from 28° C. to 36° C.; S33: Use a lock-in amplifier to output a detection voltage, the magnitude of the detection voltage is 3mV, the vibration signal of the thin film microresonator collected by the laser Doppler vibrometer is processed by the lock-in amplifier for noise reduction, and then transmitted to the computer, and analyzed by the frequency scanning module in the computer software, that is, the frequency response curves of the basic mode f1 and the high-frequency mode f2 are obtained; S34: It can be seen from the frequency response curves of the fundamental mode f1 and the high-frequency mode f2 that the high-frequency mode amplitude of the thin film microresonator is amplified and the sensitivity to temperature is improved.

2. The method of improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to claim 1, characterized in that: The implementation process of step S1 is: S11: Align the probe of the laser Doppler vibrometer to the center of the silicon nitride film of the thin film microresonator, emit a laser, and use the laser Doppler vibrometer to complete the frequency scanning and vibration signal collection of the thin film microresonator; S12: The phase-locked amplifier is connected to the piezoelectric film through a wire, and the thin film microresonator is pasted on the piezoelectric film. The detection voltage generated by the phase-locked amplifier is applied to the thin film microresonator through the piezoelectric film to stimulate the vibration of the thin film microresonator. The displacement and velocity signals generated by the thin film microresonator during vibration are collected by the probe of the laser Doppler vibrometer and converted into electrical signals through the controller of the laser Doppler vibrometer. The electrical signals are input into the computer after noise reduction processing by the phase-locked amplifier. The frequency response curve of the thin film microresonator can be observed in the computer software. The first resonance peak in the frequency response curve is the fundamental mode f1 of the thin film microresonator, and the resonance peak at three times the fundamental mode frequency is the high-frequency mode f2.

3. The method of improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to claim 2, characterized in that: In step S11, the wavelength of the emitted laser is 633nm; In S12, the magnitude of the detection voltage is 3 mV.

4. The method of improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to claim 3, characterized in that: In step S12, the fundamental mode f1 is determined to be 268.878 kHz, the high frequency mode f2 is determined to be 806.688 kHz, and the frequency ratio is 1:

3.

5. The method of improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to claim 4, characterized in that: In step S21, the pump voltage V p The process of gradually increasing from 50mV to 500mV is: 50mV, 100mV, 200mV, 300mV, 400mV, 500mV; In step S23, A0 is 0.199 mV, A0' is 2.313 mV, and the amplitude is increased by 11.623 times, thereby achieving enhancement of the high-frequency modal amplitude of the thin film microresonator.

6. The method of improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to claim 1, characterized in that: In step S32, the process of gradually increasing the temperature of the thin film microresonator from 28°C to 36°C is: 28°C, 30°C, 32°C, 34°C, 36°C; In step S34, the temperature sensitivity of f1 of the fundamental mode is 270.65 kHz / °C, and the temperature sensitivity of f2 of the high frequency mode is 859.45 kHz / °C, and the temperature sensitivity is increased by 3.18 times.

7. The method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to claim 6, characterized in that: The device is realized by using internal resonance to enhance the modal amplitude and temperature sensitivity of the microresonator. The device includes a thin film microresonator, a piezoelectric sheet, a heating laser, a laser Doppler vibrometer, a lock-in amplifier, a signal generator and a computer. The laser Doppler vibrometer includes a probe and a controller. The probe is used to emit a laser and align the laser to the center of the thin film microresonator. The controller is used to convert the displacement and velocity signals of the thin film microresonator detected by the probe into electrical signals. The laser Doppler vibrometer, the phase-locked amplifier, and the piezoelectric sheet are connected in sequence, and the thin film micro-resonator is pasted on the piezoelectric sheet; the phase-locked amplifier is connected to a computer, the signal generator is connected to the piezoelectric sheet, and the thin film micro-resonator and the piezoelectric sheet are both placed in a vacuum chamber; The laser light emitted by the heating laser is aimed at the thin film microresonator to heat the thin film microresonator.

8. The method for improving the modal amplitude and temperature sensitivity of a microresonator by utilizing internal resonance according to claim 7, characterized in that: A displacement stage is provided at the bottom of the vacuum chamber to adjust the position of the vacuum chamber and thus adjust the position of the thin film microresonator; the vacuum degree of the vacuum chamber is 10-2 mbar; The thin film microresonator comprises a single crystal silicon substrate and a silicon nitride film grown on the single crystal silicon substrate by chemical vapor deposition, wherein the size of the silicon nitride film is: 500 μm in length, 500 μm in width, and 100 nm in thickness; The piezoelectric piece is a circular ceramic piece made of lead zirconate titanate with a piezoelectric coefficient d33 of 350 pmV. -1 The dimensions of the piezoelectric sheet are: 30 mm in diameter and 2 mm in thickness.

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