Sensor based on multi-resonant-cavity structure and sensing measurement method

Abstract

The invention belongs to the technical field of sensors, and particularly relates to a multi-purpose sensor based on a multi-resonant-cavity structure and a sensing detection method of the multi-purpose sensor. The device is formed by packaging a plurality of resonant cavities, a resonant cavity connecting part, a movable mass block and a coupling part. Narrow-spectrum laser is connected into the input end of the coupling part, and the input end outputs an optical signal modulated by the sensor and is coupled with a single resonant cavity to excite the optical mechanical vibration mode of all the resonant cavities. The position of the movable mass block changes after the movable mass block is influenced by air pressure or a magnetic field in the resonant cavity. The position change of the movable mass block causes the change of various optical mechanical resonant frequencies of the multiple resonant cavities. And the change of the resonant frequency is extracted from the output optical signal, so that the corresponding target physical quantity is monitored. The method has the advantages that high-sensitivity sensing detection can be realized; electromagnetic interference is resisted, and the influence of environment temperature fluctuation is reduced; manufacturing is simple, and design cost is low.

Description

Technical Field

[0001] The 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 photomechanical effect refers to a phenomenon in which the light field in an optical device drives the device itself to vibrate mechanically. Sensors based on the photomechanical effect refer to microcavity mechanical vibration frequencies that are affected by many factors in the external environment (mass, air pressure, liquid viscosity / density / speed of sound, etc.), which will cause frequency shifts. Therefore, the relationship between them can be used to make corresponding sensors to monitor changes in a certain physical quantity. In this way, sensors based on the photomechanical effect often have the characteristics of high resolution.

[0003] The specific content of the photomechanical effect is that due to the existence of the light field pressure in the optical microcavity, the cavity length becomes longer and the resonant wavelength is redshifted. The redshift of the resonant cavity wavelength directly changes the original light field distribution, which increases the detuning between the pump light and the cavity resonant wavelength, weakens the light field distribution in the cavity, reduces the light pressure in the cavity, and relaxes the cavity length. This cycle repeats, realizing the mechanical vibration of the cavity. Ultimately, the frequency of the mechanical vibration modulates the frequency of the emitted light, so that it carries the information of the vibration frequency.

[0004] At present, the microbubble sensors designed based on the photomechanical effect are all based on a single photomechanical resonance peak generated by a single resonant cavity, and then the sensing analysis is performed through the offset of its mechanical resonance peak. Such sensors have the following limitations: first, since there is only one photomechanical resonance peak as a sensing indicator, fluctuations in ambient temperature will cause a large error in the sensing results; second, the material of the microbubble is quartz, and the change in air pressure has a very small effect on the mechanical resonance frequency of the microbubble, resulting in a low sensitivity of the air pressure sensor based on a single microbubble; finally, the mechanical damping of the liquid itself will greatly increase the system damping of the microbubble, making it difficult to realize a magnetic sensor based on the photomechanical effect that fills the microbubble with magnetic fluid. These problems 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, so as to 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 error can be reduced.

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

[0007] The present invention provides a multi-purpose sensor based on a multi-resonance cavity structure, which is unique in that it has multiple resonant cavities that will experience mechanical resonance, and 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; both ends of the resonant cavity are connected to an environment to be detected; there is a movable mass block between the resonant cavities, and the movable mass block can move between several resonant cavities.

[0008] Specifically, a multi-purpose sensor based on a multi-resonance cavity structure has two hollow resonant cavities that will experience mechanical resonance, and 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 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 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 contained inside two hollow quartz microbubbles together. This design enables the liquid droplet to move freely in 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 within a range of no more than 300 μm, and the wall thickness is also limited to a level of no more than 22 μm. In addition, in order to ensure the consistency of the performance of 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 material of the droplets is selected as magnetic fluid, which gives the droplets controllability under the action of a magnetic field. The size of the droplets is precisely controlled within a range of no more than 120 μm to ensure that they can exist stably and easily manipulated inside the quartz microbubble. Without external interference, the position of the droplets can remain stable; however, when affected by changes in air pressure or magnetic fields, the position of the droplets will change accordingly. This feature enables the sensor to respond sensitively to environmental changes and output accurate detection signals.

[0014] The sensing principle of the multi-purpose sensor of the multi-resonant cavity structure of the present invention is based on the change of the 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 They represent the mechanical damping, mechanical frequency and Langevin force (i=b, d), respectively, and represent 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 equations. The relationship between the droplet position and the spectrum change is obtained.

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

[0019] Furthermore, the tunable laser is responsible for emitting a high-quality laser beam as the light source of the detection system. The single-mode optical fiber accurately transmits the laser output by the laser to the micro-nano optical fiber, effectively collects the optical signal modulated by the sensor, and then transmits it back to the subsequent processing unit. The core of the multifunctional sensor with a multi-resonant cavity structure is two quartz microbubbles connected in series on the same quartz tube. Both ends of the two microbubbles are provided with openings and are connected to the outside world through Teflon hoses. One of the hoses serves as an introduction channel for the air pressure to be measured, and the other serves as a channel for the reference air pressure. The syringe achieves precise control of the initial position of the droplet inside the sensor by connecting one of the Teflon hoses. At the same time, the injection pump provides the necessary power support for the syringe to ensure that it can complete the adjustment of the droplet position. The photodetector is responsible for receiving the optical signal modulated by the sensor and efficiently converting it into an electrical signal. The oscilloscope is mainly used to display the optical signal collected by the photodetector in the form of a spectrum. The spectrum analyzer further performs spectrum analysis on the optical signal collected by the photodetector to display the frequency distribution and characteristics of the signal.

[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 pressure and magnetic field sensing and measuring method of a multi-purpose sensor based on a multi-resonance cavity structure, the method comprising the following steps: first, coupling a micro-nano optical fiber to a quartz microbubble, and inputting a narrow-wave laser to excite the optomechanical resonance mode of two quartz microbubbles; then, using an injection 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 spectrum analyzer to determine the initial frequency difference ΔF0; then, connecting one end of the quartz microbubble of the multi-purpose sensor with a multi-resonance cavity structure to the pressure to be measured and the other end to the reference pressure, the droplet is displaced under the action of the pressure difference, and the optomechanical spectrum characteristics are recorded after the droplet is stabilized to obtain the frequency difference ΔF1; then, using the injection pump and the syringe to restore the droplet to the initial position; thereafter, placing the sensor in a magnetic field, the direction of the magnetic field being parallel to the direction of the quartz tube, the droplet is displaced again under the action of the magnetic field, and the optomechanical spectrum characteristics are recorded after the droplet is stabilized to obtain the frequency difference ΔF2; finally, by calibrating the reference, ΔF1 and ΔF2 are converted to obtain the precise values ​​of the pressure to be measured and the magnetic field strength.

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

[0023] First of all, 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. And 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. Thirdly, the position of the movable mass block is used as an indicator to reflect the air pressure intensity and the 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 do not have high equipment requirements, are simple to operate, and are conducive to popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings herein are incorporated into and constitute a part of the specification, showing 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 for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0025] Figure 1 It is a structural view 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-resonance 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-resonance cavity structure of the present invention.

[0029] Figure 5 It is a diagram of the spectrum change results of the air pressure sensing test of the 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 scheme and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The preferred embodiments of the present invention are described in detail below in conjunction with 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 definite definition of the protection scope 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 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] Embodiment 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 is coupled to a coupling component 5; 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, 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 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 the droplet can move inside the two hollow quartz microbubbles.

[0038] The quartz microbubbles are all made of quartz with a refractive index of 1.45. The diameter of the quartz microbubbles is controlled within a range of no more than 300 μm, and the wall thickness is also limited to no more than 22 μm. In addition, in order to ensure the consistency of the performance of the two quartz microbubbles, the difference in their diameters is further limited to a tiny range of no more than 5 μm.

[0039] In the present sensor, the optical microcavity is provided by the quartz microbubble 1, and 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 mechanical spectrum consisting of two resonance peaks can be obtained on the output optical signal after analysis by the spectrum analyzer 10 (see Figure 4 ), the optomechanical spectrum can be solved by the following equations:

[0040]

[0041] where Γ mi ,Ω mi and F i They represent the mechanical damping, mechanical frequency and Langevin force (i=b, d), respectively, and represent 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 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.

[0042] Embodiment 2:

[0043] In this embodiment, based on the parameters of Example 1 and the air pressure test system (see Figure 2 ), use 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, a tunable laser 7 is turned on and a narrow-wave laser is input to excite the optomechanical resonance mode of the quartz microbubble 1 and the quartz microbubble 2; then, the droplet 4 is moved to the initial position by using the injection pump 8 and the syringe 9, and the optomechanical spectrum characteristics of the initial state of the sensor are obtained by the spectrum analyzer 10 to determine the initial frequency difference ΔF0; third, one end of the quartz microbubble of the multi-purpose sensor 6 with a multi-resonance cavity structure is connected to the air pump 13, and the other end is connected to the reference air pressure, which is atmospheric pressure here; 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 is stable, 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] Embodiment 3:

[0046] In this embodiment, based on the parameters of embodiment 1 and the magnetic field testing system (see Figure 3 ), use a multi-purpose sensor with a multi-resonant cavity structure 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, a tunable laser 7 is turned on and a narrow-wave laser is input to excite the optomechanical resonance mode of the quartz microbubble 1 and the quartz microbubble 2; then, the droplet 4 is moved to the initial position by using the injection pump 8 and the syringe 9, and the optomechanical spectrum characteristics of the initial state of the sensor are obtained by the spectrometer 10 to determine the initial frequency difference ΔF0; in the third step, a multi-purpose sensor 6 with a multi-resonance cavity structure is placed in a magnetic field formed by an electromagnet 14; in the fourth step, the magnetic field intensity generated by the electromagnet is changed, and the magnetic fluid droplet 4 is displaced under the action of magnetic traction. After the droplet is stable, 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 intensity conditions. At this point, the magnetic field intensity sensing experiment is completed.

[0048] The present invention realizes the sensing capability of a multi-purpose sensor based on a multi-resonant cavity structure and a sensing detection method thereof for at least two purposes of air pressure and magnetic field strength through Examples 2 and 3. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-purpose sensor based on a multi-resonant cavity structure, characterized in that: The invention has a plurality of resonant cavities that will have mechanical resonance, and 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; both ends of the resonant cavity are connected to the environment to be detected; there is a movable mass block between the resonant cavities, and the movable mass block can move between several resonant cavities.

2. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 1, characterized in that: The invention has two resonant cavities that will have mechanical resonance, the two 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; there is a movable mass block between the two resonant cavities, and the movable mass block can move between the two resonant cavities.

3. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 1, characterized in that: The resonant cavity is a microbubble, microdisk, or microring structure; the resonant cavity connector is a tubular or columnar structure; the coupling component is a side-thrown optical fiber, a micro-nano optical fiber, or a waveguide; the movable mass block is in a droplet or solid state, and the material is water, magnetic fluid, paraffin, quartz, and silicon dioxide.

4. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 1, characterized in that: The resonant cavity is two hollow quartz microbubbles, and the resonant cavity connecting part 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, and one of the quartz microbubbles 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 magnetic fluid droplet, which exists inside the two hollow quartz microbubbles, and the droplet can move inside the two hollow quartz microbubbles.

5. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 4, characterized in that: The diameter of the quartz microbubbles does not exceed 300 μm, and the wall thickness does not exceed 22 μm; the diameter difference between two quartz microbubbles does not exceed 5 μm.

6. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 3, characterized in that: The droplet material is magnetic fluid; the droplet size does not exceed 120 μm; the droplet maintains a stable position when not disturbed, but changes position when affected by air pressure and magnetic field.

7. The multi-purpose sensor based on a multi-resonant cavity structure according to claim 3, characterized in that: During the movement of the droplet, the micro-nano optical fiber and the quartz microbubble remain mutually coupled; the input end of the micro-nano optical fiber receives the narrow-wavelength laser, and the input end outputs the optical signal modulated by the sensor.

8. A detection system based on the multi-purpose sensor based on the multi-resonant cavity structure according to any one of claims 1 to 5, 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 comprises a plurality of resonant cavities connected in series on the same resonant cavity connector, both ends of which are connected to Teflon hoses, one of which is an inlet channel for the environment to be measured, and the other is a 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 photoelectric detector 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.

9. A sensing measurement method based on the multi-purpose sensor based on the multi-resonance cavity structure according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Couple the coupling component to a resonant cavity, input narrow-wavelength laser, and excite the optomechanical resonant mode of the two coupled cavities; Step 2: Use a syringe pump and a syringe to move the movable mass block to the initial position, and obtain the optomechanical spectrum characteristics of the sensor's initial state through a spectrum analyzer to obtain the initial frequency difference ΔF0; Step 3: Set a reference environment based on the physical quantity to be measured. The physical quantity to be measured can be air pressure intensity, magnetic field intensity, temperature, vibration, light intensity, and the reference environment is an environment where the corresponding physical quantity is known; Step 4: Connect one end of the coupling cavity connector of the multi-purpose sensor with a multi-resonant cavity structure to the environment to be measured, and the other end to the reference environment. The movable mass block is displaced under the effect of the difference between the two environments, wherein the environmental difference can be a pressure difference, a magnetic field force, a temperature difference, or a mechanical resistance difference. After the movable mass block is stable, the optical mechanical spectrum characteristics are recorded to obtain the frequency difference ΔF1 at this time; Step 5: By calibrating the reference, convert ΔF1 to obtain the intensity of the physical quantity to be measured at this time; Step 6: Use the syringe pump and syringe to move the movable mass back to its initial position.

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