A sensor based on multi-resonant cavity structure and sensing measurement method

Abstract

The present invention belongs to the field of sensor technology, and specifically relates to a multi-purpose sensor based on a multi-resonant cavity structure and a sensing detection method thereof. The present invention is encapsulated by multiple resonant cavities, resonant cavity connecting components, a movable mass block, and a coupling component. A narrow-spectrum laser is connected to the input end of the coupling component, and the input end outputs an optical signal modulated by the sensor, which is coupled with a single resonant cavity to excite the optomechanical vibration mode of all resonant cavities. The movable mass block changes its position after being affected by air pressure or magnetic field in the resonant cavity. The position change of the movable mass block will cause changes in multiple optomechanical resonant frequencies of the multi-resonant cavity. The change in resonant frequency is extracted from the output optical signal, thereby realizing the monitoring of the corresponding target physical quantity. The advantages of the present invention are that it can achieve high-sensitivity sensing detection; resist electromagnetic interference, reduce the impact of ambient temperature fluctuations; simple to manufacture, and low design cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a multi-purpose sensor based on a multi-resonance cavity structure and a sensing detection method thereof. Background Art

[0002] The optomechanical effect refers to a phenomenon in which the light field in an optical device drives the device itself to mechanical vibration. Sensors based on the optomechanical effect involve microcavity mechanical vibrations that are affected by many factors in the external environment (mass, air pressure, liquid viscosity / density, speed of sound, etc.), causing frequency shifts. By exploiting these relationships, sensors can be developed to monitor changes in a specific physical quantity. As a result, sensors based on the optomechanical effect often possess high resolution.

[0003] The optomechanical effect occurs when the optical field pressure within an optical microcavity increases the cavity length and causes a redshift in the resonant wavelength. This redshift in the resonant wavelength directly alters the original optical field distribution, increasing the detuning between the pump light and the cavity resonant wavelength. This weakens the intracavity optical field distribution, reduces the intracavity optical pressure, and causes the cavity length to relax. This cycle repeats, resulting in mechanical vibrations in the cavity. Ultimately, the frequency of the mechanical vibrations modulates the frequency of the emitted light, causing it to carry information about that vibration frequency.

[0004] Currently, microbubble sensors designed based on the optomechanical effect are based on a single optomechanical resonance peak generated by a single resonant cavity, and then perform sensing analysis based on the shift of this mechanical resonance peak. Such sensors have the following limitations: First, because there is only a single optomechanical resonance peak as a sensing indicator, fluctuations in ambient temperature can cause significant errors in the sensing results; second, because the microbubbles are made of quartz, changes in air pressure have a very small effect on the mechanical resonance frequency of the microbubbles, resulting in low sensitivity of air pressure sensors based on single microbubbles; finally, the mechanical damping of the liquid itself greatly increases the system damping of the microbubbles, making it difficult to implement optomechanical magnetic sensors that fill the microbubbles with magnetic fluid. These issues limit their application scenarios and scope. Summary of the Invention

[0005] At least one of the purposes of the present invention is to overcome the problems existing in the above-mentioned prior art and propose a multi-purpose sensor based on a multi-resonant cavity structure and a sensing detection method thereof, which can realize the measurement of multiple physical quantities including air pressure sensing and magnetic field sensing. The manufacturing process is simple, the cost is low, the sensitivity is high, and the influence of ambient temperature fluctuations on its measurement errors can be reduced.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a multi-purpose sensor based on a multi-resonant cavity structure. Its uniqueness lies in that it has multiple resonant cavities that can experience mechanical resonance. These resonant cavities are connected in series on the same resonant cavity connector and are close to each other; one of the resonant cavities is coupled to a coupling component; the two ends of the resonant cavity are connected to the environment to be detected; and a movable mass block is present between the resonant cavities, which can move between several resonant cavities.

[0008] Specifically, a multi-purpose sensor based on a multi-resonant cavity structure has two hollow resonant cavities that can experience mechanical resonance. The two hollow resonant cavities are connected in series on the same resonant cavity connector and are close to each other; one of the resonant cavities is coupled to a coupling component; both ends of the hollow resonant cavity have openings, which are used to connect to the environment to be detected; there is a movable mass block inside the two hollow resonant cavities, and the movable mass block can move inside the two hollow resonant cavities.

[0009] Furthermore, the hollow resonant cavity is two hollow quartz microbubbles, the resonant cavity connector is a quartz tube, the two quartz microbubbles are connected in series on the same quartz tube and are close to each other; the coupling component is a micro-nano optical fiber, one of the quartz microbubbles and the micro-nano optical fiber are coupled to each other; both ends of the quartz microbubble have openings, which are used to connect to the environment to be detected; the movable mass block is a magnetic fluid droplet, which exists inside the two hollow quartz microbubbles, and the droplet can move inside the two hollow quartz microbubbles.

[0010] Furthermore, a liquid droplet is housed inside the two hollow quartz microbubbles. This design allows the liquid droplet to move freely within the internal space of the two quartz microbubbles, thereby generating corresponding displacement according to changes in environmental conditions, which is then captured by the sensor and converted into a readable signal.

[0011] Furthermore, the diameter of the quartz microbubbles is controlled to be no more than 300 μm, while their wall thickness is also limited to no more than 22 μm. Furthermore, to ensure the consistency of performance between the two quartz microbubbles, the difference in their diameters is further limited to a tiny range of no more than 5 μm.

[0012] Furthermore, the micro-nano optical fiber needs to be coupled with a quartz microbubble. During the operation of the sensor, the micro-nano optical fiber needs to introduce laser light into the resonant cavity and excite the photomechanical vibration modes of the two quartz resonant cavities.

[0013] Furthermore, the droplet material is selected as a magnetic fluid, which makes the droplet controllable under the influence of a magnetic field. The droplet size is precisely controlled to no more than 120μm, ensuring its stable existence and easy manipulation within the quartz microbubble. In the absence of external interference, the position of the droplet can remain stable; however, when subjected to changes in air pressure or magnetic fields, the position of the droplet will change accordingly. This characteristic enables the sensor to sensitively respond to environmental changes and output accurate detection signals.

[0014] The sensing principle of the multi-purpose sensor with a multi-resonant cavity structure of the present invention is based on the change in resonant frequency caused by the multi-resonant cavity photomechanical effect. The resonant frequency of the multi-resonant cavity can be solved by the following equation:

[0015]

[0016] where Γ mi ,Ω mi and F i Represent the mechanical damping, mechanical frequency and Langevin force (i = b, d), respectively, representing the corresponding characteristics of the two resonant cavities. i , k i and m i represents the corresponding mechanical displacement, spring constant and effective mass. κ represents the mechanical coupling coefficient between the two mechanical modes. F0 is the optical gradient force.

[0017] The movement of the droplet inside the resonant cavity affects the effective mass of the two resonant cavities, so the resonant frequencies of the two resonant cavities can be solved from the displacement spectrum characteristics obtained from the above equation. The relationship between the droplet position and the spectrum change is obtained.

[0018] The present invention also provides a detection system for a multi-purpose sensor based on a multi-resonant cavity structure, which mainly includes the following key components: a tunable laser, a single-mode optical fiber, a multi-functional sensor with a multi-resonant cavity structure, a syringe, an injection pump, a photodetector, an oscilloscope and a spectrometer.

[0019] Furthermore, the tunable laser emits a high-quality laser beam, serving as the light source for the detection system. The single-mode optical fiber precisely transmits the laser output to the micro-nano optical fiber, effectively collecting the modulated optical signal from the sensor and transmitting it back to the subsequent processing unit. The core of the multifunctional sensor with a multi-resonant cavity structure lies in two quartz microbubbles connected in series on a single quartz tube. These microbubbles have openings at both ends and are connected to the outside world via Teflon hoses. One hose serves as a channel for the measured air pressure, while the other serves as a channel for the reference air pressure. The syringe, connected to one of the Teflon hoses, precisely controls the initial position of the droplet within the sensor. The syringe pump provides the necessary power to the syringe, ensuring it can adjust the droplet's position. The photodetector receives the modulated optical signal from the sensor and efficiently converts it into an electrical signal. The oscilloscope displays the optical signal collected by the photodetector as a spectrum. The spectrometer further performs spectral analysis on the optical signal collected by the photodetector to display the signal's frequency distribution and characteristics.

[0020] The detection system of the present invention is suitable for detecting various physical quantities including air pressure and magnetic field.

[0021] Specifically, the present invention relates to a method for sensing and measuring air pressure and magnetic field of a multi-purpose sensor based on a multi-resonant cavity structure, the method comprising the following steps: first, coupling a micro-nano optical fiber to a quartz microbubble, and inputting a narrow-wavelength laser to excite the optomechanical resonant mode of the two quartz microbubbles; then, using a syringe pump and a syringe to move a droplet to an initial position, and obtaining the optomechanical spectrum characteristics of the initial state of the sensor through a spectrometer to determine the initial frequency difference ΔF0; then, connecting one end of the quartz microbubble of the multi-purpose sensor with a multi-resonant cavity structure to the air pressure to be measured and the other end to the reference air pressure, causing the droplet to displace under the action of the pressure difference, and recording the optomechanical spectrum characteristics after the droplet stabilizes to obtain a frequency difference ΔF1; then, using a syringe pump and a syringe to restore the droplet to its initial position; thereafter, placing the sensor in a magnetic field with the direction of the magnetic field parallel to the direction of the quartz tube, causing the droplet to displace again under the action of the magnetic field, and recording the optomechanical spectrum characteristics after the droplet stabilizes to obtain a frequency difference ΔF2; finally, by calibrating the reference, converting ΔF1 and ΔF2 to obtain the precise values ​​of the air pressure and magnetic field strength to be measured.

[0022] The beneficial effects of the present invention are:

[0023] First, the present invention has obvious structural differences from general optomechanical single microbubble resonant cavity sensors. The present invention uses a multi-resonant cavity structure and excites two optomechanical vibration modes in the multi-resonant cavity. The droplet position is used to reflect the intensity index of the physical quantity to be measured. Secondly, the measurement characterization method based on the difference in the optomechanical resonant frequencies of the two resonant cavities can effectively reduce the impact of ambient temperature fluctuations on the measurement results and improve stability. Third, the position of the movable mass block is used as an indicator to reflect the air pressure intensity and magnetic field intensity, which increases the sensitivity of the sensor and improves the sensor sensing performance. Finally, the detection system and test method of a multi-purpose sensor based on a multi-resonant cavity structure provided by the present invention have low equipment requirements and are simple to operate, which is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification, are used to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort. In the drawings:

[0025] Figure 1 This is a structural diagram of the multi-purpose sensor based on the multi-resonance cavity structure of the present invention.

[0026] Figure 2 It is a diagram of an air pressure testing system of a multi-purpose sensor with a multi-resonance cavity structure based on an embodiment of the present invention.

[0027] Figure 3 It is a diagram of a magnetic field testing system of a multi-purpose sensor with a multi-resonant cavity structure according to an embodiment of the present invention.

[0028] Figure 4 This is the initial optomechanical spectrum diagram of the multi-purpose sensor based on the multi-resonant cavity structure of the present invention.

[0029] Figure 5 FIG. 1 is a diagram illustrating the spectrum change results of an air pressure sensing test of a multi-purpose sensor with a multi-resonance cavity structure according to an embodiment of the present invention.

[0030] Numbers in the figure: 1-first resonant cavity, 2-second resonant cavity, 3-resonant cavity connector, 4-movable mass block, 5-coupling component, 6-multi-purpose sensor with multi-resonant cavity structure, 7-tunable laser, 8-syringe pump, 9-syringe, 10-spectrometer, 11-oscilloscope, 12-photodetector, 13-air pump, 14-electromagnet. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the scope of protection of the present invention.

[0032] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention.

[0033] As used in the embodiments of the present invention and the appended claims, the singular forms "a", "an", "said" and "the" are intended to include the plural forms as well, and "a plurality" generally includes at least two, unless the context clearly indicates otherwise.

[0034] The present invention belongs to the technical field of sensors, and in particular relates to a multi-purpose sensor based on a multi-resonance cavity structure and a sensing detection method thereof.

[0035] Example 1:

[0036] In this embodiment, a multi-purpose sensor based on a multi-resonant cavity structure (see Figure 1 ), specifically including a first resonant cavity 1 and a second resonant cavity 2 that can produce mechanical resonance, the two hollow resonant cavities are connected in series on the same resonant cavity connector 3 and are close to each other; the first resonant cavity 1 and the coupling component 5 are coupled to each other; both ends of the hollow resonant cavity have openings, which are used to connect to the environment to be detected; there is a movable mass block 4 inside the two hollow resonant cavities, and the movable mass block can move inside the two hollow resonant cavities.

[0037] The first resonant cavity and the second resonant cavity are two hollow quartz microbubbles, the resonant cavity connector is a quartz tube, and the two quartz microbubbles are connected in series on the same quartz tube and are close to each other; the coupling component is a micro-nano optical fiber, and one quartz microbubble is coupled to the micro-nano optical fiber; both ends of the quartz microbubble have openings, which are used to connect to the environment to be detected; the movable mass block is a droplet, which exists inside the two hollow quartz microbubbles and can move inside the two hollow quartz microbubbles.

[0038] The quartz microbubbles are all made of quartz with a refractive index of 1.45. Their diameter is controlled to no more than 300 μm, and their wall thickness is limited to no more than 22 μm. Furthermore, to ensure consistent performance between the two quartz microbubbles, the difference in their diameters is further limited to a tiny 5 μm.

[0039] In this sensor, the optical microcavity is provided by the quartz microbubble 1. The optical fiber generated by the tunable laser 7 is introduced into the optical microcavity through the micro-nano optical fiber, causing the mechanical resonance of the quartz microbubble 1 and the quartz microbubble 2. Therefore, the optical signal output can be analyzed by the spectrum analyzer 10 to obtain the optical mechanical spectrum consisting of two resonance peaks (see Figure 4 ), the optomechanical spectrum can be solved by the following equations:

[0040]

[0041] where Γ mi ,Ω mi and F i Represent the mechanical damping, mechanical frequency and Langevin force (i = b, d), respectively, representing the corresponding characteristics of the two resonant cavities. i , k i and m i represents the corresponding mechanical displacement, spring constant, and effective mass. κ represents the mechanical coupling coefficient between the two mechanical modes. F0 is the optical gradient force. [1] The movement of the droplet inside the resonant cavity affects the effective masses of the two resonant cavities, so the resonant frequencies of the two resonant cavities can be solved from the displacement spectrum characteristics obtained from the above equation. The relationship between the droplet position and the spectrum change is obtained.

[0042] Example 2:

[0043] In this embodiment, based on the parameters of Example 1 and the air pressure test system (see Figure 2 ), using a multi-purpose sensor with a multi-resonant cavity structure for air pressure sensing, the specific test method steps are as follows:

[0044] First, a micro-nano optical fiber 5 is coupled to a quartz microbubble 1, and a tunable laser 7 is turned on and a narrow-wavelength laser is input to excite the optomechanical resonance mode of quartz microbubbles 1 and quartz microbubbles 2. Subsequently, a syringe pump 8 and a syringe 9 are used to move the droplet 4 to its initial position, and the optomechanical spectrum characteristics of the initial state of the sensor are obtained by a spectrometer 10 to determine the initial frequency difference ΔF0. Third, one end of the quartz microbubble of the multi-purpose sensor 6 with a multi-resonant cavity structure is connected to an air pump 13, and the other end is connected to a reference air pressure, which is atmospheric pressure in this case. Fourth, the air pressure of the air pump is changed, and the droplet 4 is displaced under the action of the pressure difference. After the droplet stabilizes, the optomechanical spectrum characteristics are recorded to obtain the frequency difference ΔF1. Finally, the experiment is repeated to obtain the spectrum changes under different air pressure conditions (see Figure 5 ), so far, the air pressure sensing experiment is completed.

[0045] Example 3:

[0046] In this embodiment, based on the parameters of Example 1 and the magnetic field testing system (see Figure 3 ), a multi-purpose sensor with a multi-resonant cavity structure is used to sense the magnetic field strength. The specific test method steps are as follows:

[0047] First, a micro-nano optical fiber 5 is coupled to a quartz microbubble 1, and a tunable laser 7 is turned on and a narrow-wavelength laser is input to excite the optomechanical resonance mode of quartz microbubbles 1 and quartz microbubbles 2. Subsequently, a syringe pump 8 and a syringe 9 are used to move the droplet 4 to its initial position, and the optomechanical spectrum characteristics of the initial state of the sensor are obtained through a spectrometer 10 to determine the initial frequency difference ΔF0. Third, a multi-purpose sensor 6 with a multi-resonant cavity structure is placed in a magnetic field formed by an electromagnet 14. Fourth, the magnetic field strength generated by the electromagnet is changed, and the magnetic fluid droplet 4 is displaced under the action of magnetic traction. After the droplet stabilizes, the optomechanical spectrum characteristics are recorded to obtain the frequency difference ΔF2. Finally, the experiment is repeated to obtain the spectrum changes under different magnetic field strength conditions. At this point, the magnetic field strength sensing experiment is completed.

[0048] Through Examples 2 and 3, the present invention implements a multi-purpose sensor based on a multi-resonant cavity structure and its sensing detection method, capable of sensing at least two purposes: air pressure and magnetic field intensity. The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A multi-purpose sensor based on a multi-resonant cavity structure, characterized by: The resonant cavity consists of two hollow quartz microbubbles connected in series by a quartz tube. The two quartz microbubbles are close to each other and are connected in series by a micro-nano optical fiber. The coupling component is a micro-nano optical fiber, with one quartz microbubble coupled to the micro-nano optical fiber. The quartz microbubbles have openings at both ends for connecting to the environment to be detected. The movable mass is a magnetic fluid droplet that exists inside the two hollow quartz microbubbles and can move within the two hollow quartz microbubbles. During the movement of the droplet, the micro-nano optical fiber and the quartz microbubble maintain mutual coupling; the input end of the micro-nano optical fiber receives the narrowwave laser, and the output end outputs the optical signal modulated by the sensor.

2. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 1, characterized in that: The diameter of the quartz microbubbles does not exceed 300 μm, and the wall thickness does not exceed 22 μm; the difference in diameter between two quartz microbubbles does not exceed 5 μm.

3. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 2, characterized in that: The droplet size does not exceed 120μm; the position of the droplet remains stable when not disturbed, but will change when affected by air pressure and magnetic field.

4. A detection system based on the multi-purpose sensor based on the multi-resonant cavity structure according to any one of claims 1 to 3, characterized in that: include: Tunable laser, single-mode optical fiber, multi-purpose sensor based on multi-resonant cavity structure, syringe, syringe pump, photodetector, oscilloscope, spectrum analyzer; among them: The tunable laser is used to emit an outgoing laser; The single-mode optical fiber is used to transmit the laser light emitted by the laser to the micro-nano optical fiber, and collect and transmit the optical signal modulated by the sensor back; The multi-purpose sensor with a multi-resonant cavity structure includes two resonant cavities connected in series on the same resonant cavity connector, with Teflon hoses connected at both ends, one of which is the entrance channel for the environment to be measured, and the other Teflon hose is the reference environment channel; The syringe is connected to a Teflon hose to control the initial position of the movable mass block; The injection pump is used to provide extraction power for the syringe; The photodetector is used to receive the optical signal modulated by the sensor and convert it into an electrical signal; The oscilloscope is used to display the light signal collected by the photodetector as a spectrum; The spectrum analyzer is used to display the optical signal collected by the photoelectric detector as a spectrum.

5. A sensing measurement method based on the multi-purpose sensor detection system based on the multi-resonant cavity structure according to claim 4, characterized in that: The following steps are involved: First, a micro-nano optical fiber is coupled to a quartz microbubble, and a narrow-wavelength laser is input to excite the optomechanical resonant modes of the two quartz microbubbles. Subsequently, a syringe pump and syringe are used to move the droplet to its initial position, and the optomechanical spectrum characteristics of the sensor's initial state are obtained using a spectrometer to determine the initial frequency difference ΔF0. Next, one end of the quartz microbubble of the multi-purpose sensor with a multi-resonant cavity structure is connected to the air pressure to be measured, and the other end is connected to the reference air pressure. The droplet displaces under the action of the pressure difference, and the optomechanical spectrum characteristics are recorded after the droplet stabilizes to obtain the frequency difference ΔF1. Then, a syringe pump and syringe are used to restore the droplet to its initial position. After that, the sensor is placed in a magnetic field with the direction of the magnetic field parallel to the direction of the quartz tube. The droplet displaces again under the action of the magnetic field, and the optomechanical spectrum characteristics are recorded after the droplet stabilizes to obtain the frequency difference ΔF2. Finally, through calibration reference, ΔF1 and ΔF2 are converted to obtain the precise values ​​of the air pressure to be measured and the magnetic field strength.

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