Device and method for realizing modulated signal amplification based on stochastic resonance in nanomechanical resonator

Abstract

The present invention discloses a device and method for realizing modulated signal amplification based on random resonance in a nanomechanical resonator, which specifically relates to the field of signal amplification technology, including a laser beam, an optical path setting and a test component for transmitting the laser beam, and a detection method using optical interference, and amplifying the amplitude modulated signal by applying a certain broadband noise to the nanomechanical resonator to be tested based on atomic-level thickness in a nonlinear state. The present invention realizes a random conversion rate of up to 22.7 kHz in the nanomechanical resonator, and based on this high-frequency conversion, the signal-to-noise ratio of the amplitude modulated signal is increased by more than 2 times.

Description

Technical Field

[0001] The invention relates to a device and a method for realizing modulated signal amplification based on random resonance in a nanomechanical resonator, and belongs to the technical field of signal amplification. Background Art

[0002] Stochastic resonance is a technique that uses an appropriate amount of noise to amplify the periodic signal acting on a bistable nonlinear system. In 1981, Benzi et al. first proposed this concept to explain the periodicity of the ice age. Since then, stochastic resonance has been widely used in the fields of electricity, optics and superconductivity.

[0003] The mechanism of signal amplification by stochastic resonance is: when the external excitation gradually increases, the response of the system no longer follows Hooke's law, and presents the well-known Duffing bistable phenomenon. When the system is in the bistable region, its response becomes a multi-valued function with two states of low amplitude and high amplitude. At this time, random fluctuations in the outside world, such as white noise, will cause the system's response to randomly switch between the low amplitude state and the high amplitude state. This random conversion can be used to amplify amplitude modulated signals.

[0004] However, due to the large size of traditional microelectromechanical systems (MEMS) devices, their conversion rate is only tens of hertz, which is low and difficult to cover the human voice band (20 Hz ~ 20000 Hz). If the conversion frequency can be extended to thousands of hertz while reducing the energy dissipated in each conversion, it can open up new application scenarios for stochastic resonance in the audio field, such as audio amplifiers.

[0005] With the development of nanofabrication technology, the emergence of mechanical resonators based on atomically thick two-dimensional materials has made the above assumptions possible. They have extremely small mass, extremely low bending stiffness and large tensile stiffness. These characteristics make it easy to realize Duffing nonlinearity, and their random conversion rate can reach kHz level with extremely low energy consumption. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a device and method for amplifying a modulated signal based on stochastic resonance in a nanomechanical resonator. Stochastic resonance is used to apply a certain broadband noise to a nanomechanical resonator in a nonlinear state, thereby achieving a conversion rate of up to 22.7 kHz. Based on this high-frequency conversion, the signal-to-noise ratio of the modulated signal is increased by more than 2 times.

[0007] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0008] On the one hand, the present invention provides a device for realizing modulated signal amplification based on random resonance in a nanomechanical resonator, comprising a helium-neon laser, wherein the helium-neon laser is used to emit a laser beam toward an optical fiber coupling component, wherein the optical fiber coupling component is used to expand and collimate the laser beam, and transmit it to a half-wave plate, wherein the half-wave plate is used to adjust the energy proportion of the horizontal component p wave and the vertical component s wave in the beam, wherein the laser beam passes through the half-wave plate, is reflected by a reflection component, and is transmitted to a polarization beam splitter cube, wherein the polarization beam splitter cube is used to reflect the vertical component s wave out of the optical path, and allows the horizontal component p wave to pass through, wherein the horizontal component p wave is incident on an objective lens via a quarter-wave plate, wherein a vacuum cavity is provided on the other side of the objective lens, wherein the vacuum cavity is used to place a nanomechanical resonator to be measured, and wherein the objective lens is used to focus the laser beam and transmit the laser beam through the vacuum cavity to be incident on the nanomechanical resonator to be measured;

[0009] The polarization beam splitter cube is connected to a photodetector, which is connected to a spectrum analyzer. The photodetector is used to receive the optical signal of the polarization beam splitter cube, convert it into an electrical signal, and transmit it to the spectrum analyzer. The spectrum analyzer is used to receive the electrical signal and display it in the frequency domain.

[0010] The vacuum cavity is equipped with a radio frequency connector, which is connected to a microwave bias device. The microwave bias device includes a DC terminal and an RF terminal. The DC terminal is connected to a DC voltage source, and the RF terminal is connected to an arbitrary waveform signal generator and a sine wave signal generator. The arbitrary waveform signal generator is used to output wide-bandwidth noise voltages of different amplitudes, and the sine waveform signal generator is used to output a sine wave signal.

[0011] Furthermore, the fiber coupling assembly includes a polarization-maintaining single-mode optical fiber and two fiber couplers placed opposite to each other. The two fiber couplers are connected by a polarization-maintaining single-mode optical fiber. The polarization-maintaining single-mode optical fiber is used to transmit the laser beam focused by one fiber coupler to another fiber coupler for beam expansion and collimation.

[0012] Furthermore, the reflection component includes two reflection mirrors, which are symmetrically placed and are used to reflect the laser beam twice at 90 degrees and then make it incident on the polarization beam splitter cube in a direction opposite to the initial emission direction.

[0013] Further, a beam calibration component and a neutral density filter are included;

[0014] The neutral density filter is disposed between the helium-neon laser and the optical fiber coupling assembly, and is used to partially attenuate the power of the laser beam;

[0015] The beam calibration assembly is used to calibrate the position of the laser beam incident on the nanomechanical resonator to be measured, and includes a flippable beam splitter, a beam splitter, a lens, a camera and a white light source;

[0016] The white light source is used to emit white light to a beam splitter, and the beam splitter is used to direct the white light into an objective lens after passing through a reversible beam splitter, and to direct the white light reflected by the nanomechanical resonator to be measured and part of the laser beam reflected through a lens to be incident on a camera. The reversible beam splitter is arranged between the objective lens and a quarter-wave plate, and is used to reflect the emitted white light into the objective lens, and at the same time reflect the white light reflected by the resonator and part of the laser beam to the camera.

[0017] On the other hand, the present invention provides a method for amplifying a modulated signal based on stochastic resonance in a nanomechanical resonator, which is implemented by the device for amplifying a modulated signal based on stochastic resonance in a nanomechanical resonator as described in any one of the above, and comprises:

[0018] The nanomechanical resonator to be tested is placed in a vacuum cavity and the helium-neon laser is turned on;

[0019] Start the DC voltage source and spectrum analyzer, set the output voltage of the DC voltage source to a fixed value, set the frequency range of the spectrum analyzer to 10 MHz, and the resolution bandwidth to 5 Hz;

[0020] Starting an arbitrary waveform signal generator, setting the arbitrary waveform signal generator to output wide-bandwidth noise voltage signals of different amplitudes, and measuring the response spectrum of the nanomechanical resonator to the wide-bandwidth noise voltages of different amplitudes within a set frequency range by a spectrum analyzer, wherein the set frequency range includes a frequency range extending by several MHz on both sides of the resonant frequency of the nanomechanical resonator to be measured as the center frequency;

[0021] The relationship between the effective temperature and the noise voltage of the nanomechanical resonator to be tested is obtained according to the response spectrum of the nanomechanical resonator to wide-bandwidth noise voltages of different amplitudes within a set frequency range;

[0022] Turn off the arbitrary waveform signal generator, and start the sine wave signal generator, change the output frequency of the sine wave signal generator, so that the output frequency of the sine wave signal generator is scanned from low frequency to high frequency with a fixed step length and from high frequency to low frequency with the same step length, record the maximum value of the spectrum at each output frequency, in which mode the spectrum analyzer displays the relationship between the amplitude at the center frequency and time, and obtain the frequency response curve of the nanomechanical resonator to be tested, wherein the frequency response curve of the nanomechanical resonator to be tested includes a hysteresis region;

[0023] The driving frequency at the middle position of the hysteresis region is taken as the output frequency of the sine wave signal generator, and the spectrum analyzer is set to 0 Hz frequency bandwidth mode. In this mode, the spectrum analyzer displays the relationship between the amplitude at the center frequency and time. The arbitrary waveform signal generator is started, and the noise voltage at the top curve of the spectrum under the wide bandwidth noise voltage of different amplitudes within the set frequency range is taken as the noise voltage output by the arbitrary waveform signal generator. The frequency response jump curve of the nanomechanical resonator to be tested over time is measured by the spectrum analyzer;

[0024] According to the jump curve of the frequency response of the nanomechanical resonator to be tested over time, a random conversion rate curve at different driving frequencies in the hysteresis region is obtained;

[0025] The driving frequency at the highest point of the random conversion rate curve at different driving frequencies in the hysteresis region is taken as the output frequency of the sine wave signal generator, and the arbitrary waveform signal generator is set to output wide-bandwidth noise voltages of different amplitudes to obtain random conversion rate curves under wide-bandwidth noise voltages of different amplitudes;

[0026] The output mode of the sine wave signal generator is set to amplitude modulation output, the carrier frequency is the driving frequency at which the highest point of the random conversion rate curve under different driving frequencies in the hysteresis region is located, the modulation frequency is set to about 1 / 2 of the conversion rate according to the random conversion rate curve under wide-bandwidth noise voltages of different amplitudes, the center frequency of the spectrum analyzer is set to the carrier frequency, the frequency range is set to several times of the modulation frequency, and the modulated signal spectrum under wide-bandwidth noise voltages of different amplitudes is obtained through the spectrum analyzer;

[0027] The signal-to-noise ratio of the modulation signal output by the nanomechanical resonator to be tested under the wide-bandwidth noise voltage of different amplitudes is calculated according to the modulation signal spectrum under the wide-bandwidth noise voltage of different amplitudes;

[0028] According to the signal-to-noise ratio of the modulated signal output by the nanomechanical resonator to be tested under wide-bandwidth noise voltages of different amplitudes and the relationship between the effective temperature of the nanomechanical resonator to be tested and the noise voltage, the relationship between the signal-to-noise ratio and the effective temperature of the nanomechanical resonator to be tested is obtained;

[0029] The effective temperature value when the signal-to-noise ratio is maximum is determined according to the relationship between the signal-to-noise ratio of the modulation signal output by the nanomechanical resonator to be measured and the effective temperature. At this time, the amplification of the modulation signal achieves the maximum value.

[0030] Furthermore, the relationship between the effective temperature and the noise voltage of the nanomechanical resonator to be measured is obtained according to the frequency spectrum within the set frequency under the wide bandwidth noise voltage of different amplitudes, including:

[0031] Calculate the response rate of the nanomechanical resonator to be measured, and its expression is as follows:

[0032]

[0033] in, represents the response rate of the nanomechanical resonator to be measured, G represents the conversion gain of the photodetector, P APD represents the laser power received by the photodetector, R represents the reflectivity of the nanomechanical resonator to be measured, |d R / d z | represents the optical response rate of the nanomechanical resonator to be measured. Its physical meaning is that the reflectivity changes with the resonator. z The absolute value of the rate of change of directional displacement;

[0034] The power spectrum density of the noise voltage is obtained by dividing the ordinate of the spectrum within the set frequency range under the wide bandwidth noise voltage of different amplitudes by the resolution bandwidth of the spectrum analyzer, and the power spectrum density of the voltage minus the measured background noise is divided by the response rate of the nanomechanical resonator to be measured to obtain the power spectrum density curve of the displacement of the nanomechanical resonator to be measured within the set frequency under the wide bandwidth noise voltage of different amplitudes, wherein the set frequency range includes a frequency range extending by several MHz on both sides of the resonance frequency of the nanomechanical resonator to be measured as the center frequency;

[0035] Calculate the area covered by the power spectral density of the displacement of the nanomechanical resonator to be measured within the set frequency range under wide-bandwidth noise voltages of different amplitudes, and obtain the time t The mean square value of the internal displacement is expressed as follows:

[0036]

[0037] in, represents the power spectral density of the noise voltage, represents the background noise, represents the power spectral density of the displacement of the nanomechanical resonator to be measured, Indicates time t The mean square value of the internal displacement;

[0038] Passing time t The relationship between the effective temperature and the noise voltage of the nanomechanical resonator to be measured is calculated by the mean square value of the internal displacement, and the expression is as follows:

[0039]

[0040] in, represents the effective temperature of the nanomechanical resonator to be measured, represents the effective mass of the nanomechanical resonator to be measured, represents the nth order resonance frequency of the nanomechanical resonator to be measured, represents the Boltzmann constant.

[0041] Furthermore, the background noise is obtained by measuring the average value of the frequency spectrum far away from the resonance peak.

[0042] Furthermore, the frequency random conversion rate curve at different driving frequencies in the hysteresis region is obtained by converting the jump curve of the frequency response of the nanomechanical resonator to be tested over time, including:

[0043] A jump from a high amplitude to a low amplitude in a time-dependent jump curve of the frequency response of the nanomechanical resonator to be measured is regarded as a conversion;

[0044] The number of conversions of the frequency response of the nanomechanical resonator under test over time within a certain measurement time is calculated as the conversion rate, and the random conversion rate curves under different driving frequencies in the hysteresis region are obtained.

[0045] Furthermore, calculating the signal-to-noise ratio according to the spectrum of the modulation signal includes: taking the signal voltage value of the highest point of the spectrum of the modulation signal and dividing it by the background noise to obtain the signal-to-noise ratio.

[0046] Furthermore, after starting the helium-neon laser, a beam calibration operation is also included before the test begins, and the beam calibration operation includes: flipping the flippable beam splitter, turning on the white light source and the camera, adjusting the distance between the objective lens and the resonator, observing through the camera so that the nanomechanical resonator to be tested is on its focal plane, and adjusting the relative position of the objective lens in a direction perpendicular to the horizontal plane so that the laser beam is at the center of the resonator. After the adjustment is completed, the white light source is turned off, and the flippable beam splitter is flipped to make it parallel to the horizontal plane. At this time, the laser beam will not pass through the beam splitter;

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention provides a device for realizing modulated signal amplification based on random resonance in a nanomechanical resonator. The laser beam is transmitted through a designed optical path and incident on the surface of the nanomechanical resonator. The random resonance in the nanomechanical resonator modulates the incident laser and reflects it. The light beam reflected by the nanomechanical resonator to be tested is tested by a photoelectric detector and a spectrum analyzer, thereby realizing modulated signal amplification of the nanomechanical resonator.

[0049] The present invention is based on a resonator of atomic-thick graphene film, uses an optical interference detection method, and achieves a conversion rate of up to 22.7 kHz by applying a certain broadband noise to the nanomechanical resonator to be tested in a nonlinear state. This high-frequency adjustable conversion rate can be used for random number generators in the computing field, and by controlling the amplitude of the applied noise voltage, the conversion rate can cover the frequency band of human voice, which is unattainable by traditional silicon-based micromechanical resonators. Based on this high-frequency random conversion, the signal-to-noise ratio of the modulated signal is increased by more than 2 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of the structure of a device for amplifying a modulated signal based on stochastic resonance in a nanomechanical resonator in one embodiment of the present invention;

[0051] Figure 2 A schematic diagram of a voltage power spectrum density curve of a nanomechanical resonator to be tested under wide-bandwidth noise voltages of different amplitudes within a set frequency in a method for realizing modulated signal amplification based on stochastic resonance in a nanomechanical resonator in one embodiment of the present invention;

[0052] Figure 3 A schematic diagram of the relationship between the effective temperature and the noise voltage of a nanomechanical resonator to be measured in a method for realizing modulated signal amplification based on stochastic resonance in a nanomechanical resonator in one embodiment of the present invention;

[0053] Figure 4 A schematic diagram of a frequency response curve of a nanomechanical resonator to be tested in a nonlinear state in a method for realizing modulation signal amplification based on stochastic resonance in a nanomechanical resonator in one embodiment of the present invention;

[0054] Figure 5 A schematic diagram of a jump curve of the frequency response of a nanomechanical resonator to be tested over time in a method for realizing modulated signal amplification based on stochastic resonance in a nanomechanical resonator in an embodiment of the present invention;

[0055] Figure 6 A schematic diagram of random conversion rate curves at different driving frequencies in the hysteresis region of a method for realizing modulation signal amplification based on stochastic resonance in a nanomechanical resonator in an embodiment of the present invention;

[0056] Figure 7 A schematic diagram of random conversion rate curves at different effective temperatures of a method for realizing modulation signal amplification based on random resonance in a nanomechanical resonator in an embodiment of the present invention;

[0057] Figure 8A schematic diagram of the relationship between the signal-to-noise ratio and the effective temperature of a nanomechanical resonator to be tested in a method for realizing modulated signal amplification based on stochastic resonance in a nanomechanical resonator in one embodiment of the present invention;

[0058] In the figure: 1- He-Ne laser, 2- Neutral density filter, 3- Fiber coupler, 4- Polarization-maintaining single-mode fiber, 5- Half-wave plate, 6- Reflector, 7- Polarization beam splitter cube, 8- Quarter-wave plate, 9- Reversible beam splitter, 10- Beam splitter, 11- White light source, 12- Lens, 13- Camera, 14- Objective lens, 15- Vacuum cavity, 16- Nanomechanical resonator to be tested, 17- Microwave bias device, 18- Arbitrary waveform signal generator, 19- Sine wave signal generator, 20- DC voltage source, 21- Photodetector, 22- Spectrum analyzer. DETAILED DESCRIPTION

[0059] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0060] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances. Example 1

[0061] like Figure 1 As shown, the device for implementing modulated signal amplification based on random resonance in a nanomechanical resonator provided by the embodiment of the present invention includes a helium-neon laser 1, which is used to emit a laser beam. The laser beam enters the optical fiber coupling component after power attenuation through a neutral density filter 2.

[0062] In this embodiment, the fiber coupling assembly includes a polarization-maintaining single-mode optical fiber 4 and two optical fiber couplers 3 placed opposite to each other. The two optical fiber couplers 3 are connected by the polarization-maintaining single-mode optical fiber 4. The polarization-maintaining single-mode optical fiber 4 is used to transmit the laser beam focused by one optical fiber coupler 3 to the other optical fiber coupler 3 for beam expansion and collimation.

[0063] The optical fiber coupling component transmits the laser beam to the half-wave plate 5, which is used to adjust the energy proportion of the horizontal component p-wave and the vertical component s-wave in the beam, and adjust the fast axis direction of the half-wave plate 5 to maximize the laser beam power.

[0064] After the laser beam passes through the half-wave plate 5, it is reflected by the reflection component and transmitted to the polarization beam splitter cube 7. In this embodiment, the reflection component includes two reflectors 6, which are symmetrically placed and are used to reflect the laser beam twice at 90° and then incident on the polarization beam splitter cube 7 in the direction opposite to the initial emission direction. The polarization beam splitter cube 7 is used to reflect the vertical component s wave out of the optical path and allow the horizontal component p wave to pass through. The horizontal component p wave is incident on the objective lens through the quarter-wave plate 8. In this embodiment, the fast axis direction of the quarter-wave plate 8 is 45° to the horizontal plane, so that the reflected laser energy can reach the maximum.

[0065] A vacuum cavity 15 is disposed on the other side of the objective lens 14 . The vacuum cavity 15 is used to place a nanomechanical resonator 16 to be measured. The objective lens 14 is used to focus the laser beam and transmit the laser beam through the vacuum cavity 15 to be incident on the nanomechanical resonator 16 to be measured.

[0066] The polarization beam splitter cube 7 is connected to a photodetector 21, which is connected to a spectrum analyzer 22. The photodetector 21 is used to receive the optical signal from the polarization beam splitter cube 7, convert it into an electrical signal, and transmit it to the spectrum analyzer 22. The spectrum analyzer 22 communicates with the computer via a GPIB interface, and is used to receive the electrical signal and display it in the frequency domain.

[0067] The vacuum cavity 15 is provided with a radio frequency connector, which is connected to a microwave bias device 17. The microwave bias device 17 includes a DC terminal and an RF terminal. The DC terminal is connected to a DC voltage source 20, and the RF terminal is connected to an arbitrary waveform signal generator 18 and a sine wave signal generator 19. The arbitrary waveform signal generator 18 is used to output wide-bandwidth noise voltages of different amplitudes, and the sine waveform signal generator 19 is used to output sine wave signals. Example 2

[0068] Based on Example 1, this embodiment also includes a beam calibration component, which is used to calibrate the position of the laser beam incident on the nanomechanical resonator 16 to be measured. The beam calibration component includes a flip-up beam splitter 9, a beam splitter 10, a lens 12, a camera 13 and a white light source 11. In this embodiment, the camera 13 is a CCD camera.

[0069] The white light source 11 is used to emit white light to the beam splitter 10, and the beam splitter 10 is used to transmit the white light to the objective lens 14 after passing through the flippable beam splitter 9, and reflect the white light and part of the laser beam reflected by the nanomechanical resonator 16 to be tested to be incident on the camera 13 through the lens 12. The flippable beam splitter 9 is arranged between the objective lens 14 and the quarter-wave plate 8, and is used to reflect the emitted white light into the objective lens 14, and at the same time reflect the white light and part of the laser beam reflected by the nanomechanical resonator 16 to be tested to the camera 13.

[0070] After the beam calibration is completed, the flippable beam splitter 9 needs to be removed from the light path. Example 3

[0071] Based on Example 1, this embodiment provides a method for amplifying a modulated signal based on stochastic resonance in a nanomechanical resonator, which comprises the following steps:

[0072] The nanomechanical resonator 16 to be tested is placed in a vacuum cavity, and the He-Ne laser 1 is turned on.

[0073] The DC voltage source 20 and the spectrum analyzer 22 are started, the output voltage of the DC voltage source 20 is set to a fixed value, the frequency range of the spectrum analyzer 22 is set to 10 MHz, and the resolution bandwidth is set to 5 Hz.

[0074] The arbitrary waveform signal generator 18 is started and set to output wide-bandwidth noise voltages of different amplitudes. After the power of the HeNe laser 1 is stabilized, the spectrum of the wide-bandwidth noise voltages of different amplitudes within the set frequency range is measured by the spectrum analyzer 22.

[0075] It should be noted that the set frequency range includes a frequency range extending by several MHz on both sides of the resonance frequency of the nanomechanical resonator 16 to be tested as the center frequency.

[0076] Nanomechanical resonators of different sizes and structures respond differently to the same noise voltage, so the effective temperature is needed to measure the fluctuation level. Therefore, it is necessary to obtain the relationship between the effective temperature and the noise voltage of the nanomechanical resonator 16 to be tested based on the spectrum within the set frequency under the wide bandwidth noise voltage of different amplitudes, specifically including:

[0077] The response rate of the nanomechanical resonator 16 to be measured is calculated, and its expression is as follows:

[0078]

[0079] in, represents the response rate of the nanomechanical resonator 16 to be tested, G represents the conversion gain of the photodetector 21, P APD represents the laser power received by the photodetector 21, |d R / d z | represents the optical response rate of the nanomechanical resonator 16 to be measured, and its physical meaning is that the reflectivity changes with the resonator z The absolute value of the rate of change of directional displacement.

[0080] The power spectrum density of the noise voltage is obtained by dividing the vertical coordinate of the spectrum under the wide bandwidth noise voltage of different amplitudes within the set frequency range by the resolution bandwidth of the spectrum analyzer 22. The power spectrum density of the voltage is subtracted from the measured background noise and then divided by the response rate of the nanomechanical resonator 16 to be tested to obtain the voltage power spectrum density curve of the nanomechanical resonator 16 to be tested under the wide bandwidth noise voltage of different amplitudes within the set frequency range, as shown in FIG. Figure 2 shown.

[0081] Calculate the area covered by the power spectrum density of the displacement of the nanomechanical resonator 16 to be measured within a set frequency range under wide bandwidth noise voltages of different amplitudes, and obtain the time t The mean square value of the internal displacement is expressed as follows:

[0082]

[0083] in, represents the power spectral density of the noise voltage, represents the background noise, represents the power spectral density of the displacement of the nanomechanical resonator 16 to be measured, Indicates time t The mean square value of the internal displacement.

[0084] Passing time t The relationship between the effective temperature and the noise voltage of the nanomechanical resonator to be measured is calculated by the mean square value of the internal displacement, and the expression is as follows:

[0085]

[0086] in, represents the effective temperature of the nanomechanical resonator 16 to be measured, represents the effective mass of the nanomechanical resonator 16 to be measured, represents the nth order resonance frequency of the nanomechanical resonator 16 to be measured, represents the Boltzmann constant.

[0087] Through the above calculation steps, the effective temperature value corresponding to the nanomechanical resonator 16 to be tested under different amplitude wide bandwidth noise voltages can be obtained, such as Figure 3 shown.

[0088] Next, the arbitrary waveform signal generator 18 is turned off, and the sine wave signal generator 19 is turned on to change the output frequency of the sine wave signal generator 19 so that the output frequency of the sine wave signal generator 19 is scanned from a low frequency to a high frequency with a fixed frequency step length ( Figure 4 solid line) and sweeping from high frequency to low frequency with the same step size ( Figure 4The maximum value of the spectrum of each output frequency is recorded to obtain the frequency response curve of the nanomechanical resonator 16 to be tested, as shown in FIG. Figure 4 As shown, Figure 4 The y-axis is the voltage at the output end of the photodetector 21 , and the x-axis is the output frequency of the sine wave signal generator 19 , that is, the driving frequency of the nanomechanical resonator 16 to be measured.

[0089] from Figure 4 It can be seen that the frequency response curve of the nanomechanical resonator 16 to be tested includes a hysteresis region. There is a non-overlapping part in the response amplitude from low frequency to high frequency and from high frequency to low frequency. This part just encloses a closed area, namely the hysteresis region. This is because for the nanomechanical resonator, when the external excitation gradually increases, the deformation of the graphene film also increases. When it is greater than a certain critical value, its strain and applied stress can no longer be described by Hooke's law.

[0090] The driving frequency at the middle position of the hysteresis region is taken as the output frequency of the sine wave signal generator 19, and the spectrum analyzer 22 is set to the 0 Hz frequency bandwidth (zero span) mode. In this mode, the spectrum analyzer displays the relationship between the amplitude at the center frequency and time. In this embodiment, the bandwidth resolution of the spectrum analyzer 22 is set to 10 kHz, and the measurement time is 10 ms. In the 0 Hz frequency bandwidth mode, the horizontal axis of the spectrum measured by the spectrum analyzer 22 is the measurement time.

[0091] The noise voltage at the top curve of the spectrum under the wide bandwidth noise voltage with different amplitudes within the set frequency range is taken as the noise voltage output by the arbitrary waveform signal generator 18, and the frequency response jump curve of the nanomechanical resonator 16 to be tested over time is measured by the spectrum analyzer 22, as shown in Figure 5 shown.

[0092] like Figure 5 As shown, the hopping frequency at 44.2 MHz is up to 22.7 kHz, and within the 1 MHz range, the hopping frequency can be adjusted from several Hz to 22.7 kHz.

[0093] The random conversion rate curves at different driving frequencies in the hysteresis region are obtained by converting the frequency response jump curve of the nanomechanical resonator 16 to be tested over time, specifically including:

[0094] The jump from high amplitude to low amplitude in the time-dependent jump curve of the frequency response of the nanomechanical resonance 16 to be measured is regarded as a conversion.

[0095] The number of conversions of the frequency response of the nanomechanical resonator 16 to be measured over time within a certain measurement time is calculated as the conversion rate, and a random conversion rate curve under different driving frequencies in the hysteresis region is obtained, such as Figure 6 shown.

[0096] The driving frequency at the highest point of the random conversion rate curve at different driving frequencies in the hysteresis region is taken as the output frequency of the sine wave signal generator 19. In this embodiment, the driving frequency at the highest point of the random conversion rate curve at different driving frequencies in the hysteresis region is 44.2 MHz. The arbitrary waveform signal generator 18 is set to output wide-bandwidth noise voltages of different amplitudes to obtain random conversion rate curves at different effective temperatures, such as Figure 7 shown.

[0097] The output mode of the sinusoidal wave signal generator 19 is set to amplitude modulation output, the carrier frequency is the driving frequency at which the highest point of the random conversion rate curve under different driving frequencies in the hysteresis region is located, the modulation frequency is set to about 1 / 2 of the conversion rate according to the random conversion rate curve under wide-bandwidth noise voltages of different amplitudes, the center frequency of the spectrum analyzer 22 is set to the carrier frequency, the frequency range is set to several times of the modulation frequency, the arbitrary waveform signal generator 18 is set to output wide-bandwidth noise voltages of different amplitudes, and the modulated signal spectrum under wide-bandwidth noise voltages of different amplitudes is obtained through the spectrum analyzer 22.

[0098] The signal-to-noise ratio of the modulated signal output by the nanomechanical resonator 16 to be tested under wide-bandwidth noise voltages of different amplitudes is calculated based on the modulation signal spectrum under wide-bandwidth noise voltages of different amplitudes. The specific calculation method is to take the signal voltage value at the highest point of the modulation signal spectrum and divide it by the background noise to obtain the signal-to-noise ratio of the modulation signal.

[0099] According to the signal-to-noise ratio of the nanomechanical resonator 16 to be tested under wide-bandwidth noise voltages of different amplitudes and the relationship between the effective temperature of the nanomechanical resonator 16 to be tested and the noise voltage, the relationship between the signal-to-noise ratio and the effective temperature of the nanomechanical resonator 16 to be tested is obtained, such as Figure 8 shown.

[0100] The effective temperature value when the signal-to-noise ratio is maximum is determined according to the relationship between the signal-to-noise ratio of the modulation signal output by the nanomechanical resonator 16 to be tested and the effective temperature. At this time, the amplification of the modulation signal achieves the maximum value. Example 4

[0101] On the basis of Example 3, this embodiment further includes a beam calibration operation after starting the He-Ne laser 1 and before the test begins, which includes:

[0102] Flip the flippable beam splitter 9 to make it parallel to the beam splitter.

[0103] Turn on the white light source 11 and the camera 13, observe and adjust the distance between the objective lens 14 and the resonator through the camera, so that the nanomechanical resonator 16 to be measured is on its focal plane, and adjust the relative position of the objective lens 14 in the direction perpendicular to the horizontal plane so that the laser beam is at the center of the resonator 16.

[0104] After the adjustment is completed, the white light source 11 is turned off, and the flippable beam splitter 9 is flipped to make it parallel to the horizontal plane. At this time, the laser beam will not pass through the beam splitter 9, so as to facilitate subsequent operations.

[0105] The above is only 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 technical 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 device for amplifying modulated signals based on stochastic resonance in a nanomechanical resonator, characterized in that: It comprises a helium-neon laser, which is used to emit a laser beam toward a fiber coupling component, which is used to expand and collimate the laser beam and transmit it to a half-wave plate, which is used to adjust the energy proportion of the horizontal component p wave and the vertical component s wave in the beam, and after the laser beam passes through the half-wave plate, it is reflected by a reflection component and transmitted to a polarization beam splitter cube, which is used to reflect the vertical component s wave out of the optical path and allow the horizontal component p wave to pass through, and the horizontal component p wave is incident on an objective lens through a quarter-wave plate, and a vacuum cavity is provided on the other side of the objective lens, which is used to place a nanomechanical resonator to be measured, and the objective lens is used to focus the laser beam and transmit it through the vacuum cavity to the nanomechanical resonator to be measured; The polarization beam splitter cube is connected to a photodetector, which is connected to a spectrum analyzer. The photodetector is used to receive the optical signal of the polarization beam splitter cube, convert it into an electrical signal, and transmit it to the spectrum analyzer. The spectrum analyzer is used to receive the electrical signal and display it in the frequency domain. The vacuum cavity is equipped with a radio frequency connector, the radio frequency connector is connected to a microwave bias device, the microwave bias device includes a DC terminal and an RF terminal, the DC terminal is connected to a direct current voltage source, the RF terminal is connected to an arbitrary waveform signal generator and a sine wave signal generator, the arbitrary waveform signal generator is used to output a wide bandwidth noise voltage with different amplitudes, and the sine wave signal generator is used to output a sine wave signal; The method for realizing modulated signal amplification based on stochastic resonance in a nanomechanical resonator comprises: The nanomechanical resonator to be tested is placed in a vacuum cavity and the helium-neon laser is turned on; Start the DC voltage source and spectrum analyzer, set the output voltage of the DC voltage source to a fixed value, set the frequency range of the spectrum analyzer to 10 MHz, and the resolution bandwidth to 5 Hz; Starting an arbitrary waveform signal generator, setting the arbitrary waveform signal generator to output wide-bandwidth noise voltage signals of different amplitudes, and measuring the response spectrum of the nanomechanical resonator to the wide-bandwidth noise voltages of different amplitudes within a set frequency range by a spectrum analyzer, wherein the set frequency range includes a frequency range extending by several MHz on both sides of the resonant frequency of the nanomechanical resonator to be measured as the center frequency; The relationship between the effective temperature and the noise voltage of the nanomechanical resonator to be tested is obtained according to the response spectrum of the nanomechanical resonator to wide-bandwidth noise voltages of different amplitudes within a set frequency range; Turning off the arbitrary waveform signal generator and starting the sine wave signal generator, changing the output frequency of the sine wave signal generator so that the output frequency of the sine wave signal generator is scanned from a low frequency to a high frequency with a fixed frequency step length and from a high frequency to a low frequency with the same step length, recording the maximum value of the spectrum at each output frequency, and obtaining a frequency response curve of the nanomechanical resonator to be tested, wherein the frequency response curve of the nanomechanical resonator to be tested includes a hysteresis region; The driving frequency at the middle position of the hysteresis region is taken as the output frequency of the sine wave signal generator, and the spectrum analyzer is set to a 0 Hz frequency bandwidth mode. In this mode, the spectrum analyzer displays the relationship between the amplitude at the center frequency and time. The arbitrary waveform signal generator is started, and the noise voltage at the top curve of the spectrum under the wide bandwidth noise voltage of different amplitudes within the set frequency range is taken as the noise voltage output by the arbitrary waveform signal generator. The frequency response jump curve of the nanomechanical resonator to be tested over time is measured by the spectrum analyzer; According to the jump curve of the frequency response of the nanomechanical resonator to be tested over time, a random conversion rate curve at different driving frequencies in the hysteresis region is obtained; The driving frequency at the highest point of the random conversion rate curve at different driving frequencies in the hysteresis region is taken as the output frequency of the sine wave signal generator, and the arbitrary waveform signal generator is set to output wide-bandwidth noise voltages of different amplitudes to obtain random conversion rate curves under wide-bandwidth noise voltages of different amplitudes; The output mode of the sine wave signal generator is set to amplitude modulation output, the carrier frequency is the driving frequency at which the highest point of the random conversion rate curve under different driving frequencies in the hysteresis region is located, the modulation frequency is set to 1 / 2 of the conversion rate according to the random conversion rate curve under wide-bandwidth noise voltages of different amplitudes, the center frequency of the spectrum analyzer is set to the carrier frequency, the frequency range is set to several times of the modulation frequency, and the modulation signal spectrum under wide-bandwidth noise voltages of different amplitudes is obtained through the spectrum analyzer; The signal-to-noise ratio of the modulation signal output by the nanomechanical resonator to be tested under the corresponding noise voltage is calculated according to the modulation signal spectrum under the wide-bandwidth noise voltage with different amplitudes; According to the signal-to-noise ratio of the modulated signal output by the nanomechanical resonator to be tested under wide-bandwidth noise voltages of different amplitudes and the relationship between the effective temperature of the nanomechanical resonator to be tested and the noise voltage, the relationship between the signal-to-noise ratio and the effective temperature of the nanomechanical resonator to be tested is obtained; The effective temperature value when the signal-to-noise ratio is maximum is determined according to the relationship between the signal-to-noise ratio of the modulation signal output by the nanomechanical resonator to be tested and the effective temperature. At this time, the amplification of the modulation signal achieves the maximum value.

2. The device for amplifying modulated signals based on stochastic resonance in a nanomechanical resonator according to claim 1, characterized in that: The optical fiber coupling assembly includes a polarization-maintaining single-mode optical fiber and two optical fiber couplers placed opposite to each other. The two optical fiber couplers are connected by a polarization-maintaining single-mode optical fiber. The polarization-maintaining single-mode optical fiber is used to transmit the laser beam focused by one optical fiber coupler to the other optical fiber coupler for beam expansion and collimation.

3. The device for amplifying modulated signals based on stochastic resonance in a nanomechanical resonator according to claim 1, characterized in that: The reflection component includes two reflection mirrors, which are symmetrically placed and used to reflect the laser beam twice at 90 degrees and then make it incident into the polarization beam splitter cube in the direction opposite to the initial emission direction.

4. The device for amplifying modulated signals based on stochastic resonance in a nanomechanical resonator according to claim 1, characterized in that: Also included are beam collimation components and neutral density filters; The neutral density filter is disposed between the helium-neon laser and the optical fiber coupling assembly, and is used to partially attenuate the power of the laser beam; The beam calibration assembly is used to calibrate the position of the laser beam incident on the nanomechanical resonator to be measured, and includes a flippable beam splitter, a beam splitter, a lens, a camera and a white light source; The white light source is used to emit white light to a beam splitter, and the beam splitter is used to direct the white light into an objective lens after passing through a reversible beam splitter, and to direct the white light reflected by the nanomechanical resonator to be measured and part of the laser beam reflected through a lens to be incident on a camera. The reversible beam splitter is arranged between the objective lens and a quarter-wave plate, and is used to reflect the emitted white light into the objective lens, and at the same time reflect the white light reflected by the resonator and part of the laser beam to the camera.

5. The device for amplifying modulated signals based on stochastic resonance in a nanomechanical resonator according to claim 1, characterized in that: The method of obtaining the relationship between the effective temperature and the noise voltage of the nanomechanical resonator to be measured according to the frequency spectrum within the set frequency under the wide bandwidth noise voltage of different amplitudes includes: Calculate the response rate of the nanomechanical resonator to be measured, and its expression is as follows: ； in, represents the response rate of the nanomechanical resonator to be measured, G represents the conversion gain of the photodetector, R represents the reflectivity of the nanomechanical resonator to be measured, represents the laser power received by the photodetector, It represents the optical response rate of the nanomechanical resonator to be measured. Its physical meaning is that the reflectivity changes with the resonator z The absolute value of the rate of change of directional displacement; The power spectrum density of the noise voltage is obtained by dividing the ordinate of the spectrum under the wide-bandwidth noise voltage of different amplitudes within the set frequency range by the resolution bandwidth of the spectrum analyzer, and the power spectrum density of the voltage minus the measured background noise is divided by the response rate of the nanomechanical resonator to be measured to obtain the power spectrum density curve of the displacement of the nanomechanical resonator to be measured within the set frequency under the wide-bandwidth noise voltage of different amplitudes; Calculate the area covered by the power spectral density of the displacement of the nanomechanical resonator to be measured within the set frequency range under wide-bandwidth noise voltages of different amplitudes, and obtain the time t The mean square value of the internal displacement is expressed as follows: ； ； in, represents the power spectral density of the noise voltage, represents the background noise, represents the power spectral density of the displacement of the nanomechanical resonator to be measured, Indicates time t The mean square value of the internal displacement; Passing time t The relationship between the effective temperature and the noise voltage of the nanomechanical resonator to be measured is calculated by the mean square value of the internal displacement, and the expression is as follows: ； in, represents the effective temperature of the nanomechanical resonator to be measured, represents the effective mass of the nanomechanical resonator to be measured, ω n represents the nth order resonance frequency of the nanomechanical resonator to be measured, represents the Boltzmann constant.

6. The device for amplifying modulated signals based on stochastic resonance in a nanomechanical resonator according to claim 5, characterized in that: The background noise is obtained by measuring the average value of the spectrum far away from the resonance peak.

7. The device for realizing modulation signal amplification based on stochastic resonance in a nanomechanical resonator according to claim 1, characterized in that: The method of converting the frequency response jump curve of the nanomechanical resonator to be tested over time to obtain the frequency random conversion rate curve at different driving frequencies in the hysteresis region includes: The jump from high amplitude to low amplitude in the time-dependent jump curve of the frequency response of the nanomechanical resonator to be measured is regarded as a conversion; The number of conversions of the frequency response of the nanomechanical resonator under test over time within a certain measurement time is calculated as the conversion rate, and the random conversion rate curves under different driving frequencies in the hysteresis region are obtained.

8. The device for realizing modulated signal amplification based on stochastic resonance in a nanomechanical resonator according to claim 1, characterized in that: The signal-to-noise ratio is calculated based on the output modulated signal spectrum, including: taking the signal voltage value of the highest point of the modulated signal spectrum and dividing it by the background noise to obtain the signal-to-noise ratio.

9. The device for amplifying modulated signals based on stochastic resonance in a nanomechanical resonator according to claim 1, characterized in that: After starting the HeNe laser, the test also includes a beam calibration operation before starting, which includes: Flipping can flip the beam splitter to make it parallel to the beam splitter; Turn on the white light source and the camera, observe and adjust the distance between the objective lens and the resonator through the camera so that the nanomechanical resonator to be measured is on its focal plane, and adjust the relative position of the objective lens in the direction perpendicular to the horizontal plane so that the laser beam is at the center of the resonator; After the adjustment is completed, turn off the white light source and flip the beam splitter to make it parallel to the horizontal plane. At this time, the laser beam will not pass through the beam splitter.

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