Method and device for measuring displacement of micro-nano suspended mass by fiber laser interference

Abstract

This application belongs to the field of precision measurement technology, specifically disclosing a method and apparatus for measuring the displacement of a micro / nano levitation oscillator using fiber laser interferometry. The apparatus comprises: a laser for outputting laser light; an optical circulator for transmitting the laser light to the end face of an optical fiber, splitting it into a first beam and a second beam. The first beam is reflected at the end face of the optical fiber. When the micro / nano levitation oscillator undergoes lateral displacement, the scattering of the second beam changes, and it is reflected at the reflecting surface. The first beam reflected from the end face of the optical fiber and the second beam after scattering and reflection superimpose in the optical fiber to form an interference signal; the optical circulator is used to transmit the interference signal through a third port to a third photodetector; the photodetector is used to perform photoelectric conversion on the interference signal; and a signal processing module is used to extract the displacement signal of the micro / nano levitation oscillator from the photoelectrically converted interference signal. This application can improve the measurement accuracy and sensitivity of the lateral displacement of a micro / nano levitation oscillator.

Description

Technical Field

[0001] This application belongs to the field of precision measurement technology, and more specifically, relates to a method and apparatus for measuring the displacement of a micro / nano suspended oscillator using fiber laser interferometry. Background Technology

[0002] Micro-nano levitated oscillator systems, due to their extremely low mass and environmental isolation, exhibit advantages such as high quality factor and low dissipation, showing significant potential in the field of weak force sensing. Detecting the displacement of the micro-nano oscillator is a key problem that needs to be solved for the application of this system. Currently used methods include four-quadrant detectors (QPDs) to collect scattered light, camera-assisted observation, or optical cavities to enhance collection. However, for systems with small size and low levitation height, traditional spatial optical paths are difficult to construct and efficient collection of scattered light is challenging. Existing systems suffer from low integration and insufficient noise suppression, failing to meet the requirements for high-precision weak force sensing.

[0003] Therefore, there is an urgent need for a displacement measurement device and method that is compact, highly integrated, can effectively suppress laser power noise, and is suitable for micro / nano levitated oscillators with low suspension height. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this application is to provide a method and apparatus for measuring the displacement of micro / nano levitation oscillators using fiber laser interferometry, aiming to solve the problem of poor displacement detection accuracy and sensitivity of existing micro / nano levitation oscillators.

[0005] The first aspect of this application relates to an apparatus for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry, comprising: a laser, an optical circulator, an optical fiber, a reflective surface, a third photodetector, and a signal processing module; The first port of the optical circulator is connected to the output port of the laser, its second port is connected to the end face of the optical fiber through an optical fiber, and its third port is connected to the third photodetector; the end face of the optical fiber is directly opposite the reflective surface to form an interference cavity structure; the signal processing module is connected to the third photodetector; when the lateral position of the micro-nano levitating oscillator is measured, the micro-nano levitating oscillator is located inside the interference cavity. The laser is used to output laser light; the optical circulator is used to transmit the laser light to the end face of the optical fiber, splitting it into a first beam and a second beam. The first beam is reflected at the end face of the optical fiber. When the micro / nano levitating oscillator undergoes lateral displacement, the scattering of the second beam changes, and it is reflected at the reflecting surface. The first beam reflected from the end face of the optical fiber and the second beam after scattering and reflection are superimposed in the optical fiber to form an interference signal; the optical circulator is used to transmit the interference signal to a third photodetector through a third port; the third photodetector is used to perform photoelectric conversion on the interference signal; the signal processing module is used to extract the lateral displacement signal of the micro / nano levitating oscillator from the photoelectric converted interference signal.

[0006] In some implementations, constructive interference is selected. Under the given conditions, the lateral displacement signal of a micro / nano levitated oscillator is measured; the intensity of the interference signal satisfies: ; Sensitivity for measuring the lateral displacement of micro / nano levitated oscillators for: ; in, For the intensity of the interference signal light, This represents the power of the second beam reflected from the reflecting surface without scattering. The loss of optical power in the second beam is due to scattering by the micro-nano suspended oscillator. The optical power reflected from the end face of the optical fiber by the first beam; The wavelength of the laser; d This is the distance between the fiber end face and the reflecting surface; x This represents the lateral displacement of a micro / nano suspended oscillator. It is an integer.

[0007] In some embodiments, the device for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry further includes: a second fiber coupler, a second intensity modulator, a second photodetector, and a differential signal amplification module; The input end of the second fiber coupler is located at the output end of the laser. Its first output end is connected to the second intensity modulator, and its second output end is connected to the optical circulator. The output end of the second intensity modulator is connected to the second photodetector. The second photodetector and the third photodetector are connected to the differential signal amplification module. The second fiber coupler is used to split the received beam into a third beam and a fourth beam. The third beam enters the second intensity modulator, and the fourth beam enters the optical circulator. The second intensity modulator is used to adjust the power of the third beam so that the power of the third beam is consistent with the average power of the interference signal. The second photodetector is used to perform photoelectric conversion on the power-adjusted third beam. The differential signal amplification module is used to differentially amplify the third beam signal and the interference signal after photoelectric conversion, and suppress common-mode noise.

[0008] In some embodiments, the apparatus for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry further includes: a first fiber coupler and a first photodetector; The input end of the first fiber coupler is connected to the laser, and its first output end is connected to the input end of the second fiber coupler. The second output end is connected to the first photodetector. The first fiber coupler is used to split the laser into a fifth beam and a sixth beam. The fifth beam is transmitted to the first photodetector, which is used to monitor the power change of the fifth beam. The sixth beam is transmitted to the second fiber coupler.

[0009] In some embodiments, the apparatus for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry further includes a first intensity modulator and an optical isolator. The first intensity modulator is located between the optical isolator and the first fiber coupler to stabilize the laser power and suppress noise caused by unstable laser power. The optical isolator is located between the laser and the first intensity modulator to prevent light reflected from the end face of the optical fiber from entering the laser.

[0010] In some implementations, the laser is a laser diode.

[0011] The second aspect of this application relates to a method for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry, comprising the following steps: When the laser is transmitted to the end face of the optical fiber, it is divided into a first beam and a second beam. The first beam is reflected at the end face of the optical fiber. When the micro-nano levitation oscillator undergoes lateral displacement, the scattering of the second beam changes and it is reflected on the reflective surface. The first beam reflected from the end face of the optical fiber and the second beam after scattering and reflection are superimposed in the optical fiber to form an interference signal. The interference signal is converted into photoelectric signal and the lateral displacement signal of the micro-nano levitated oscillator is extracted.

[0012] In some implementations, constructive interference is selected. Under the given conditions, the lateral displacement signal of a micro / nano levitated oscillator is measured; the intensity of the interference signal satisfies: ; Sensitivity for measuring the lateral displacement of micro / nano levitated oscillators for: ; in, For the intensity of the interference signal light, This represents the power of the second beam reflected from the reflecting surface without scattering. The loss of optical power in the second beam is due to scattering by the micro-nano suspended oscillator. The optical power reflected from the end face of the optical fiber by the first beam; The wavelength of the laser; d This is the distance between the fiber end face and the reflecting surface; x This represents the lateral displacement of a micro / nano suspended oscillator. It is an integer.

[0013] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: For high-sensitivity detection mechanisms in micro-spaces: Unlike traditional side-scattered light collection methods (which are difficult to deploy in micro-experimental spaces due to their extremely low collection efficiency), this application is based on the scattering loss mechanism of Gaussian beams by micro / nano oscillators within the interference cavity. By optimizing the interferometer's operating point (adjusting it to the maximum interference fringe point), extremely weak displacement changes are transformed into significant changes in interference intensity. This principle enables the system to achieve sub-nanometer-level displacement detection sensitivity without requiring a complex collection optical path, ultimately achieving a prediction measurement accuracy of [insert accuracy here]. .

[0014] Extremely strong applicability: This application is particularly suitable for micro-nano oscillator systems with low suspension height. When the suspension gap is only on the order of micrometers, traditional geometric optical equipment cannot be used due to size and working distance limitations. However, this application, with its compact fiber end face interference structure, can penetrate deep into the interior of the micro cavity to achieve non-contact, non-destructive, and precise capture of oscillator motion information within the micrometer-level gap, providing a key technical means for precision physical measurement.

[0015] Stable signal transmission and significant noise suppression: By introducing an optical circulator, unidirectional transmission and efficient separation of the signal light are achieved. By constructing a laser power feedback control loop, the laser's inherent power noise is reduced to less than 1 / 20 of its original value. Balanced differential measurement further reduces laser power noise, suppressing common-mode noise from the reference and interference signals, thus significantly improving the system's signal-to-noise ratio.

[0016] High integration and strong environmental resistance: Except for the signal processing module and the differential signal amplification module, all other components in this application can adopt an all-fiber structure, avoiding the shortcomings of traditional spatial optical paths, such as large size, difficult alignment, and susceptibility to environmental mechanical vibration. The all-fiber design not only significantly improves the system integration and makes the device portable, but also ensures long-term working stability and measurement repeatability in complex and unsteady experimental environments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the device structure for measuring the displacement of a micro / nano suspended oscillator using fiber laser interferometry, provided in an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the differential measurement photoelectric sensor signal provided in the embodiments of this application.

[0019] Figure 3 This describes the change in the total scattered light power of the microspheres provided in this application embodiment as a function of lateral displacement.

[0020] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is a laser; 2 is an optical isolator; 3 is a first intensity modulator; 4 is a first... 2 is a fiber optic coupler; 5 is the first photodetector; 6 is the second... 2. Fiber optic coupler; 7. Second intensity modulator; 8. Second photodetector; 9. Optical circulator; 10. Third photodetector; 11. Fiber end face; 12. Micro / nano levitating oscillator; 13. Reflective surface; 14. Positive voltage source; 15. First resistor; 16. Second resistor; 17. First amplifier; 18. Third resistor; 19. Second amplifier; 20. Fourth resistor; 21. Capacitor; 22. Fifth resistor; 23. Sixth resistor; 24. Third amplifier; 25. Negative voltage source. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0023] In this application, the terms “first” and “second” are used to distinguish different objects, rather than to describe a specific order of objects.

[0024] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0025] In the description of the embodiments in this application, unless otherwise stated, "multiple" means two or more.

[0026] The method and apparatus for measuring the displacement of micro / nano suspended oscillators using fiber laser interferometry provided in this application are described below with reference to specific embodiments: Example 1 like Figure 1 As shown, this application provides a device for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry, including an optical system and a circuit system; The optical path system includes a laser 1, an optical isolator 2, a first intensity modulator 3, and a first... 2. Fiber optic coupler 4. Second 1 2. Fiber optic coupler 6, second intensity modulator 7, optical circulator 9, fiber end face 11, first photodetector 5, second photodetector 8, third photodetector 10, and reflective surface 13; The laser emitted by laser 1 first passes through optical isolator 2 to prevent reflected light from entering the laser and affecting its stability; then the laser enters the first intensity modulator 3, where the laser power is stabilized through a feedback loop; afterwards, the laser enters the first... Fiber optic coupler 4 splits the laser beam; one beam enters the first photodetector 5 to monitor changes in laser power; the other beam enters the second photodetector 1. 2. The fiber coupler 6 splits the beam again, one beam enters the second intensity modulator 7 and enters the second photodetector 8 to form a reference electrical signal, and the other beam enters the first port of the optical circulator 9.

[0027] The optical circulator 9 transmits light from the first port to the second port, causing the laser to be emitted from the fiber end face 11 and irradiate the reflective surface 13; an interference cavity structure is formed between the fiber end face 11 and the reflective surface 13.

[0028] Part of the light is reflected at the end face 11 of the optical fiber, and part is transmitted. When the transmitted laser shines on the reflective surface 13, part of the light is reflected at the reflective surface 13. The two reflected beams are superimposed in the optical fiber to form an interference signal, which is output through the third port of the optical circulator 9 and enters the third photodetector 10 for photoelectric conversion.

[0029] The circuit system includes a differential signal amplification module, a signal processing module, and a power stabilization feedback module. The differential signal amplification module includes a transimpedance amplifier circuit and a differential amplifier circuit. The second photodetector 8 and the third photodetector 10 are connected to the differential signal amplification module. This differential signal amplification module includes a transimpedance amplifier circuit and a differential amplifier circuit, used to differentially amplify the reference optical signal and the interference signal, thereby suppressing common-mode noise and improving the signal-to-noise ratio of the measurement signal.

[0030] In the actual measurement process, by adjusting the distance between the fiber end face 11 and the reflective surface 13, the interference cavity is made to work at the working point with the maximum interference light intensity, thereby improving the sensitivity of lateral displacement measurement.

[0031] When the micro / nano levitating oscillator 12 undergoes lateral displacement, it causes a change in the scattering of incident light, thereby altering the power distribution of the returned light in the interference cavity and consequently changing the interference signal. By detecting the differentially amplified electrical signal and processing it using a signal processing module, the displacement information of the micro / nano levitating oscillator can be obtained.

[0032] Furthermore, by detecting changes in laser power using the first photodetector 5 and adjusting the first intensity modulator 3 via the power stabilization feedback module, stable laser power control can be achieved, thereby reducing the impact of laser power noise on the measurement system and improving the system's measurement accuracy. In some embodiments, when the interference cavity length is fixed, the reference optical signal power can be adjusted by changing the modulation depth of the second intensity modulator 7, making the reference optical signal consistent with the average power of the interference signal, thus ensuring that the differential detection system is in optimal operating condition.

[0033] In some implementations, the power stabilization feedback module is a PID controller, and the first photodetector 5 is used to detect the laser power; the PID controller is used to achieve stable laser power feedback.

[0034] In some implementations, the optimal operating point is determined by constructive interference, and the lateral displacement of the micro / nano levitating oscillator 12 is measured. At this point, the displacement sensitivity of the micro / nano levitating oscillator is the highest, and the cavity length d satisfies the constructive interference condition. The deviation is controlled within ±20 nm to maintain a sensitivity of over 95%.

[0035] In some implementations, the laser is a laser diode.

[0036] In some embodiments, the differential signal amplification module includes a first amplifier 17, a second amplifier 19, a third amplifier 24, a second resistor 16, a sixth resistor 23, a first resistor 15, a fourth resistor 20, a fifth resistor 22, a positive voltage source 14, and a negative voltage source 25; the second resistor 16 and the sixth resistor 23 are used to convert current changes into voltage changes; the first resistor 15, the fourth resistor 20, and the fifth resistor 22 are used to control the amplification factor; the positive voltage source 14 and the negative voltage source 25 provide bias voltages to the second photodetector 8 and the third photodetector 10, which are connected in the differential signal amplification module to form a differential measurement of the signal.

[0037] In some implementations, such as Figure 1 and Figure 2 As shown, this embodiment integrates the optical path system and the circuit system into one unit; the optical path section adopts an all-fiber endface structure (laser 1 to the third photodetector 10), and the circuit section includes a self-designed low-noise photodetector motherboard (such as...). Figure 2 The circuit includes a transimpedance amplifier circuit and a differential amplifier circuit, a switching power supply motherboard, an FPGA data acquisition module, and host computer software.

[0038] Example 2 This application provides a method for measuring the displacement of a micro / nano suspended oscillator using fiber laser interferometry, specifically including the following steps: Step S1: Turn on laser 1. The laser light passes sequentially through optical isolator 2, first intensity modulator 3, and first... 2. Fiber optic coupler 4 splits the laser beam; one beam enters the first photodetector 5 to monitor the laser power, and the other beam enters the second photodetector 1. 2. Fiber optic coupler 6 splits the beam again, one beam enters the second intensity modulator 7 and the second photodetector 8 to form a reference optical signal, and the other beam enters the optical circulator 9. Step S2: The laser emitted from the second port of the optical circulator illuminates the reflecting surface through the fiber end face, and an interference cavity is formed between the fiber end face and the reflecting surface; Step S3: When the micro-nano levitating oscillator is displaced, the oscillator scatters the light emitted from the fiber end face, thereby changing the light power reflected back to the fiber end face from the reflective surface, thus changing the interference signal; Step S4: The interference light signal is converted into an electrical signal by the third photodetector and differentially amplified with the reference signal output by the second photodetector to obtain an electrical signal corresponding to the displacement of the micro-nano levitating oscillator. Step S5: The differential signal is acquired and processed by the signal processing module to obtain the displacement information of the micro-nano levitation oscillator.

[0039] In some embodiments, this application utilizes an interference cavity formed by the fiber end face and the reflecting surface for interferometric measurement. Part of the light is reflected at the fiber end face, and part is transmitted through it. When the transmitted laser beam exits from the fiber end face and illuminates the reflecting surface, part of the light is reflected, and some light is lost due to scattering by the levitating oscillator. The two reflected beams superimpose in the fiber to form an interference signal; the interference light intensity satisfies: ; in, For the intensity of the interference signal light, The power of light reflected from the reflective surface without scattering. The loss of optical power is due to the scattering of light by micro-nano suspended oscillators. The reflected light power from the fiber end face. d This is the distance between the fiber end face and the reflecting surface, i.e., the length of the interference cavity; Sensitivity for measuring the lateral displacement of micro / nano levitated oscillators for: ; in, For interference light intensity; To measure the lateral displacement of the micro / nano levitating oscillator 12 x Sensitivity.

[0040] When a micro / nano levitating oscillator is displaced, it changes the scattered light power and causes a change in the returned light power in the interference cavity, thus altering the interference signal. The displacement information of the oscillator can be obtained by detecting this change in the interference signal. Figure 3 As shown.

[0041] In summary, this application has the following advantages compared with the prior art: For high-sensitivity detection mechanisms in micro-spaces: Unlike traditional side-scattered light collection methods (which are difficult to deploy in micro-experimental spaces due to their extremely low collection efficiency), this application is based on the scattering loss mechanism of Gaussian beams by micro / nano oscillators within the interference cavity. By optimizing the interferometer's operating point (adjusting it to the maximum interference fringe point), extremely weak displacement changes are transformed into significant changes in interference intensity. This principle enables the system to achieve sub-nanometer-level displacement detection sensitivity without requiring a complex collection optical path, ultimately achieving a prediction measurement accuracy of [insert accuracy here]. .

[0042] Excellent application applicability: This application is particularly suitable for micro / nano oscillator systems with low suspension heights. In situations where the suspension gap is only on the order of micrometers, traditional geometric optics equipment cannot be used due to size and working distance limitations. However, this application, with its compact fiber end-face interference structure, can penetrate deep into the interior of a tiny cavity to achieve non-contact, non-destructive, and precise capture of oscillator motion information within a micrometer-level gap, providing a key technical means for precision physical measurement.

[0043] Stable signal transmission and significant noise suppression: By introducing an optical circulator, unidirectional transmission and efficient separation of the signal light are achieved. By constructing a laser power feedback control loop, the laser's inherent power noise is reduced to less than 1 / 20 of its original value. Balanced differential measurement further reduces laser power noise, suppressing common-mode noise from the reference and interference signals, thus significantly improving the system's signal-to-noise ratio.

[0044] High integration and strong environmental resistance: Except for the signal processing module and the differential signal amplification module, all other components in this application can adopt an all-fiber structure, avoiding the shortcomings of traditional spatial optical paths, such as large size, difficult alignment, and susceptibility to environmental mechanical vibration. The all-fiber design not only significantly improves the system integration and makes the device portable, but also ensures long-term working stability and measurement repeatability in complex and unsteady experimental environments.

[0045] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0046] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0047] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0048] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are all limitations relative to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are allowed, and approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable.

[0049] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A device for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry, characterized in that, include: Laser, optical circulator, optical fiber, reflective surface, third photodetector, and signal processing module; The first port of the optical circulator is connected to the laser output port, its second port is connected to the fiber end face through an optical fiber, and its third port is connected to the third photodetector; the fiber end face is directly opposite the reflective surface to form an interference cavity structure; the signal processing module is connected to the third photodetector; when the lateral position of the micro-nano levitating oscillator is measured, the micro-nano levitating oscillator is located inside the interference cavity. The laser is used to output laser light; the optical circulator is used to transmit the laser light to the end face of the optical fiber, splitting it into a first beam and a second beam. The first beam is reflected at the end face of the optical fiber. When the micro / nano levitating oscillator undergoes lateral displacement, the amount of scattered light from the second beam changes and is reflected at the reflective surface. The first beam reflected from the end face of the optical fiber and the second beam after scattering and reflection are superimposed in the optical fiber to form an interference signal; the optical circulator is used to transmit the interference signal to a third photodetector through a third port; the third photodetector is used to perform photoelectric conversion on the interference signal; the signal processing module is used to extract the lateral displacement signal of the micro / nano levitating oscillator from the photoelectric converted interference signal.

2. The device for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry according to claim 1, characterized in that, Selected in the context of constructive interference Under the given conditions, the lateral displacement signal of a micro / nano levitated oscillator is measured; the intensity of the interference signal satisfies: ； Sensitivity for measuring the lateral displacement of micro / nano levitated oscillators for: ； in, For the intensity of the interference signal light, This represents the power of the second beam reflected from the reflecting surface without scattering. The loss of optical power in the second beam is due to scattering by the micro-nano suspended oscillator. The optical power reflected from the end face of the optical fiber by the first beam; The wavelength of the laser; d This is the distance between the fiber end face and the reflecting surface; x This represents the lateral displacement of a micro / nano suspended oscillator. It is an integer.

3. The device for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry according to claim 1, characterized in that, Also includes: The second fiber optic coupler, the second intensity modulator, the second photodetector, and the differential signal amplification module; The input end of the second fiber coupler is located at the output end of the laser. Its first output end is connected to the second intensity modulator, and its second output end is connected to the optical circulator. The output end of the second intensity modulator is connected to the second photodetector. The second and third photodetectors are connected to the differential signal amplification module; The second fiber coupler is used to split the received beam into a third beam and a fourth beam. The third beam enters the second intensity modulator, and the fourth beam enters the optical circulator. The second intensity modulator is used to adjust the power of the third beam so that the power of the third beam is consistent with the average power of the interference signal. The second photodetector is used to perform photoelectric conversion on the power-adjusted third beam. The differential signal amplification module is used to differentially amplify the third beam signal and the interference signal after photoelectric conversion, and suppress common-mode noise.

4. The device for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry according to claim 3, characterized in that, It also includes a first fiber optic coupler and a first photodetector; The input end of the first fiber coupler is connected to the laser, and its first output end is connected to the input end of the second fiber coupler. The second output end is connected to the first photodetector. The first fiber coupler is used to split the laser into a fifth beam and a sixth beam. The fifth beam is transmitted to the first photodetector, which is used to monitor the power change of the fifth beam. The sixth beam is transmitted to the second fiber coupler.

5. The device for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry according to claim 4, characterized in that, It also includes a first intensity modulator and an optical isolator. The first intensity modulator is located between the optical isolator and the first fiber coupler and is used to stabilize the laser power and suppress noise caused by the instability of the laser power. The optical isolator is located between the laser and the first intensity modulator and is used to prevent light reflected from the end face of the optical fiber from entering the laser.

6. The apparatus for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry according to any one of claims 1 to 5, characterized in that, The laser is a laser diode.

7. A method for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry based on the apparatus according to any one of claims 1 to 6, characterized in that, Specifically, the following steps are included: When the laser is transmitted to the end face of the optical fiber, it is divided into a first beam and a second beam. The first beam is reflected at the end face of the optical fiber. When the micro-nano levitation oscillator undergoes lateral displacement, the scattering of the second beam changes and it is reflected on the reflective surface. The first beam reflected from the end face of the optical fiber and the second beam after scattering and reflection are superimposed in the optical fiber to form an interference signal. The interference signal is converted into photoelectric signal and the lateral displacement signal of the micro-nano levitated oscillator is extracted.

8. The method for measuring the displacement of a micro / nano levitated oscillator using fiber laser interferometry according to claim 7, characterized in that, Selected in the context of constructive interference Under the given conditions, the lateral displacement signal of a micro / nano levitated oscillator is measured; the intensity of the interference signal satisfies: ； Sensitivity for measuring the lateral displacement of micro / nano levitated oscillators for: ； in, For the intensity of the interference signal light, This represents the power of the second beam reflected from the reflecting surface without scattering. The loss of optical power in the second beam is due to scattering by the micro-nano suspended oscillator. The optical power reflected from the end face of the optical fiber by the first beam; The wavelength of the laser; d This is the distance between the fiber end face and the reflecting surface; x This represents the lateral displacement of a micro / nano suspended oscillator. It is an integer.

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