阅读说明：本技术 基于回音壁模式光学微腔的有害气体检测装置及检测方法 (Harmful gas detection device and detection method based on whispering gallery mode optical microcavity ) 是由 钱玮 张磊 于 2021-08-16 设计创作，主要内容包括：本发明提供一种基于回音壁模式光学微腔的有害气体检测装置,包括激光器、第一连接头、锥形光纤、光学微腔、微腔封装盒、第二连接头、光电探测器和内置有气体检测软件的上位机,激光器通过第一连接头连接于锥形光纤的输入端,光电探测器通过第二连接头连接于锥形光纤的输出端,光电探测器通过数据线与上位机之间数据传输连接,微腔封装盒内设有光学微腔,微腔封装盒设于激光器和光电探测器之间且锥形光纤自光学微腔穿过,微腔封装盒的盒壁上设有进气口和排气口。本发明具有对NH-(3)、NO-(2)、CH-(4)等典型气体高灵敏度检测识别和高精度浓度测量的能力,并具有小型化、低功耗、便携式、可远程监测的特点。(The invention provides a harmful gas detection device based on a whispering gallery mode optical microcavity, which comprises a laser, a first connector, a tapered optical fiber, an optical microcavity, a microcavity packaging box, a second connector, a photoelectric detector and an upper computer with built-in gas detection software, wherein the laser is connected to the input end of the tapered optical fiber through the first connector, the photoelectric detector is connected to the output end of the tapered optical fiber through the second connector, the photoelectric detector is connected with the upper computer through a data line in a data transmission manner, the optical microcavity is arranged in the microcavity packaging box, the microcavity packaging box is arranged between the laser and the photoelectric detector, the tapered optical fiber penetrates through the optical microcavity, and an air inlet and an air outlet are formed in the box wall of the microcavity packaging box. The invention has the function of reacting on NH 3 、NO 2 、CH 4 The typical gas has the capabilities of high-sensitivity detection and identification and high-precision concentration measurement, and has the advantages of miniaturization, low power consumption, portability and remote capabilityAnd (5) monitoring characteristics.)

1. The utility model provides a harmful gas detection device based on whispering gallery mode optics microcavity which characterized in that, includes laser instrument, first connector, toper optic fibre, optics microcavity, microcavity packaging box, second connector, photoelectric detector and embeds there is the host computer that has gaseous detection software, the laser instrument passes through first connector to be connected in the input of toper optic fibre, photoelectric detector passes through the second connector to be connected in the output of toper optic fibre, photoelectric detector passes through data transmission between data line and the host computer and is connected, be equipped with the optics microcavity in the microcavity packaging box, microcavity packaging box is located between laser instrument and the photoelectric detector and toper optic fibre passes from the optics microcavity, be equipped with air inlet and gas vent on the box wall of microcavity packaging box.

2. The harmful gas detection device based on the whispering gallery mode optical microcavity as recited in claim 1, wherein the laser is a distributed feedback semiconductor laser with an output power of 5-10mW, and a wavelength of operation of the laser emitted by the laser is selected from absorption wavelengths of the harmful gas to be detected.

3. The apparatus of claim 1, wherein the first connector and the second connector are FC/APC connectors.

4. The apparatus of claim 1, wherein the tapered optical fiber is drawn from corning single mode fiber on a fiber taper machine.

5. The apparatus for detecting harmful gas based on whispering gallery mode optical microcavity of claim 1 or 4, wherein the tapered optical fiber is prepared by a process comprising the steps of:

(1-1) removing a cladding of the middle part of the optical fiber, and fixing the optical fiber by using an optical fiber clamp;

(1-2) enabling a flame head to be close to the position of a cladding of the optical fiber, preheating, then starting a stepping motor to pull the optical fiber to move backwards, enabling the middle part of the optical fiber to be continuously thinned in the stretching process, and turning off the stepping motor and the flame after the waist of the cone meets the condition;

and (1-3) fixing the stretched optical fiber on a customized quartz plate by using light-curing glue to finish the preparation of the tapered optical fiber.

6. The apparatus of claim 5, wherein the tapered optical fiber is fabricated by the following steps: the diameter is less than 2.2 μm, and the light transmittance of the waveguide is greater than 90%.

7. The apparatus of claim 1, wherein two identical optical micro-cavities are provided in the micro-cavity package box, one of the optical micro-cavities is used for measuring the change of the external environment and isolated from the harmful gas to be detected; and the other optical microcavity is contacted with the detected harmful gas, and the two optical microcavities form an environment compensation type measuring structure.

8. The harmful gas detection device based on the whispering gallery mode optical microcavity as claimed in claim 1 or 7, wherein the optical microcavity is a quasi-cylindrical optical microcavity, the quasi-cylindrical optical microcavity is formed by arc discharge machining of a corning single-mode fiber through an optical fiber fusion splicer, and the machining process includes the following steps:

(2-1) cleaning the optical fiber with the coating layer removed, and putting the optical fiber into a V-shaped groove holder of an optical fiber fusion splicer;

and (2-2) locally softening the optical fiber by controlling the discharge of the electrode through the optical fiber fusion splicer, wherein the discharge time is about 1s, and discharging for multiple times to finally form the quasi-cylindrical optical microcavity.

9. The apparatus of claim 1, wherein the photodetector is in a grating + photosensor type structure;

the upper computer adopts a computer, and a data acquisition card is installed in the computer.

10. A method of detecting harmful gases using a whispering gallery mode optical microcavity based harmful gas detection apparatus as claimed in any one of claims 1-9, comprising the steps of:

s1, turning on a power switch of the detection device, and turning on the laser, the photoelectric detector and the upper computer;

s2, selecting the transmitting laser wavelength of the laser according to the type of the detected harmful gas;

s3, enabling laser emitted by a laser to enter a conical optical fiber and a microcavity packaging box in sequence through a first connector, and entering two quasi-cylindrical optical microcavities through evanescent wave action;

s4, after the laser entering the two quasi-cylindrical optical micro-cavities is transmitted in a whispering gallery mode, the laser is emitted from the second connector and is detected by the photoelectric detector;

s5, recording a laser spectrum A when no harmful gas exists through installing gas detection software in the upper computer;

s6, introducing the detected harmful gas into the microcavity packaging box through the gas inlet, and introducing the exhausted harmful gas into the gas recovery pool through the gas outlet and the guide pipe;

s7, the detected harmful gas entering the micro-cavity packaging box through the air inlet and the surface medium of one quasi-cylindrical optical micro-cavity are subjected to chemical reaction, the effective refractive index of the quasi-cylindrical optical micro-cavity is changed at the moment, and the refractive index change value is determined by the harmful gas to be detected and the external environment; the other quasi-cylindrical optical microcavity is isolated from the harmful gas to be detected, and the refractive index change value is determined by the external environment;

s8, repeating the steps S3-S5 to obtain a laser spectrum B after the harmful gas to be detected is introduced;

and S9, acquiring the type and concentration information of the detected harmful gas according to the spectrum wave band and the spectrum offset of the laser spectrum B relative to the laser spectrum A, wherein the spectrum peak height corresponds to the gas concentration, and the spectrum peak wavelength corresponds to the gas type.

Technical Field

The invention relates to the field of harmful gas detection, in particular to a harmful gas detection device and a detection method based on a whispering gallery mode optical microcavity.

Background

In modern industrialized society, the leakage and emission of various harmful gases occur all the time and place, and the detection and concentration control of the harmful gases have great significance to people working and living in the environment, so that the harmful gases must be effectively detected in real time.

The detection system for harmful gases generally requires that real-time detection can be efficiently and accurately realized in severe environment, and the gas types can be rapidly and accurately identified, so that the false alarm rate is effectively reduced. Therefore, the toxic source can be found quickly, the diffusion of toxic gas is prevented to reduce the damage, and the consumption of manpower, physics and financial resources caused by false alarm can be greatly reduced. Harmful gas detection is divided into contact detection and non-contact detection, and common contact detection methods comprise a Mass Spectrometry (MS), a Surface Acoustic Wave (SAW), an Ion Mobility Spectrometry (IMS), a surface enhanced Raman scattering spectroscopy (SERS) and the like; common non-contact detection methods include ultraviolet laser induced fluorescence detection (LIBS), THz laser spectroscopy and infrared spectroscopy telemetry. Although the contact method has high detection precision, the contact method has more limiting factors on application occasions, distances and sample preparation; the THz method is too costly to implement; the infrared spectrum detection can be used for remote detection and near-distance nondestructive detection, the detection precision is good, and the infrared spectrum technology becomes the first choice for the detection of chemical warfare agents in many occasions. The sensitivity and the resolution of the Fourier Transform Infrared (FTIR) spectrum technology are good, and particularly in the field remote telemetering application, the three advantages of high flux, multiple transmission and high precision of the Fourier transform infrared spectrometer are fully exerted. But because the instrument is expensive, bulky, heavy and so on, so it is not suitable for single person operation to measure harmful gas in real time.

High-precision detection systems for harmful gases generally require the ability to efficiently and accurately detect gases in real time under severe environments and to quickly and accurately identify the types of gases. The existing system can ensure the detection precision, but has the defects of high price, large volume, heavy weight and the like, and is not suitable for being operated by a single person in a portable way.

As can be seen from the above analysis, development of a small and highly sensitive device for measuring a trace amount of harmful gas is urgently required. The optical microcavity in the whispering gallery mode has extremely high quality factors and extremely small mode volume, so that the optical microcavity is applied to detection of trace harmful gases, can accurately and quickly identify the category of the detected harmful gases, and can calculate corresponding concentration. Compared with other types of harmful gas detection systems, the system has the obvious advantages of small volume, light weight, low cost and high precision, and can realize real-time monitoring of mixed harmful gas.

Disclosure of Invention

The invention aims to provide a harmful gas detection device and a detection method based on a whispering gallery mode optical microcavity, which can improve the performance of a gas sensor and form a pair of NH₃、NO₂、CH₄And the capability of high-sensitivity detection and identification and high-precision concentration measurement of harmful gases provides a miniaturized, low-power-consumption and portable high-sensitivity harmful gas sensor for users.

In order to solve the technical problems, an embodiment of the invention provides a harmful gas detection device based on a whispering gallery mode optical microcavity, which comprises a laser, a first connector, a tapered optical fiber, an optical microcavity, a microcavity packaging box, a second connector, a photoelectric detector and an upper computer with gas detection software arranged inside, wherein the laser is connected to the input end of the tapered optical fiber through the first connector, the photoelectric detector is connected to the output end of the tapered optical fiber through the second connector, the photoelectric detector is connected with the upper computer through a data line in a data transmission manner, the microcavity packaging box is internally provided with the optical microcavity, the microcavity packaging box is arranged between the laser and the photoelectric detector, the tapered optical fiber penetrates through the optical microcavity, and the box wall of the microcavity packaging box is provided with an air inlet and an air outlet.

The laser adopts a distributed feedback semiconductor laser (DFB laser), the emergent power of the DFB laser is 5-10mW, and the working wavelength of the laser emitted by the DFB laser is selected from the absorption wavelength of the harmful gas to be detected.

Preferably, the first connector and the second connector are both FC/APC connectors.

The tapered optical fiber is formed by drawing a corning single-mode optical fiber on an optical fiber tapering machine.

The preparation process of the tapered optical fiber comprises the following steps:

(1-1) removing a cladding of the middle part of the optical fiber, and fixing the optical fiber by using an optical fiber clamp;

(1-2) enabling a flame head to be close to the position of a cladding of the optical fiber, preheating, then starting a stepping motor to pull the optical fiber to move backwards, enabling the middle part of the optical fiber to be continuously thinned in the stretching process, and turning off the stepping motor and the flame after the waist of the cone meets the condition;

and (1-3) fixing the stretched optical fiber on a customized quartz plate by using light-curing glue to finish the preparation of the tapered optical fiber.

Further, the manufacturing requirements of the tapered optical fiber are as follows: the diameter is less than 2.2 μm, and the light transmittance of the waveguide is greater than 90%.

Two equal optical micro-cavities are arranged in the micro-cavity packaging box, wherein one optical micro-cavity is used for measuring the change of the external environment and is isolated from the detected harmful gas; and the other optical microcavity is contacted with the detected harmful gas, and the two optical microcavities form an environment compensation type measuring structure.

The optical microcavity is a quasi-cylindrical optical microcavity which is formed by arc discharge machining of a corning single-mode fiber through an optical fiber fusion splicer, and the machining process comprises the following steps:

(2-1) cleaning the optical fiber with the coating layer removed, and putting the optical fiber into a V-shaped groove holder of an optical fiber fusion splicer;

and (2-2) locally softening the optical fiber by controlling the discharge of the electrode through the optical fiber fusion splicer, wherein the discharge time is about 1s, and discharging for multiple times to finally form the quasi-cylindrical optical microcavity.

Preferably, the photoelectric detector adopts a grating and photoelectric sensor type structure;

the upper computer adopts a computer, and a data acquisition card is installed in the computer.

The invention also provides a detection method of the harmful gas detection device based on the whispering gallery mode optical microcavity, which comprises the following steps:

s1, turning on a power switch of the detection device, and turning on the laser, the photoelectric detector and the upper computer;

s2, selecting the transmitting laser wavelength of the laser according to the type of the detected harmful gas;

s3, enabling laser emitted by a laser to enter a conical optical fiber and a microcavity packaging box in sequence through a first connector, and entering two quasi-cylindrical optical microcavities through evanescent wave action;

s4, after the laser entering the two quasi-cylindrical optical micro-cavities is transmitted in a whispering gallery mode, the laser is emitted from the second connector and is detected by the photoelectric detector;

s5, recording a laser spectrum A when no harmful gas exists through installing gas detection software in the upper computer;

s6, introducing the detected harmful gas into the microcavity packaging box through the gas inlet, and introducing the exhausted harmful gas into the gas recovery pool through the gas outlet and the guide pipe;

s7, the detected harmful gas entering the micro-cavity packaging box through the air inlet and the surface medium of one quasi-cylindrical optical micro-cavity are subjected to chemical reaction, the effective refractive index of the quasi-cylindrical optical micro-cavity is changed at the moment, and the refractive index change value is determined by the harmful gas to be detected and the external environment; the other quasi-cylindrical optical microcavity is isolated from the harmful gas to be detected, and the refractive index change value is determined by the external environment;

s8, repeating the steps S3-S5 to obtain a laser spectrum B after the harmful gas to be detected is introduced;

and S9, acquiring the type and concentration information of the detected harmful gas according to the spectrum wave band and the spectrum offset of the laser spectrum B relative to the laser spectrum A, wherein the spectrum peak height corresponds to the gas concentration, and the spectrum peak wavelength corresponds to the gas type.

The technical scheme of the invention has the following beneficial effects:

1. the harmful gas detection device based on the whispering gallery mode optical microcavity provided by the invention is a gas sensor utilizing the whispering gallery mode optical microcavity, and can realize miniaturization and light weight.

2. By improving the quality factor and the microcavity diameter of the optical microcavity and optimizing the optical coupling method, the performance of the gas sensor can be greatly improved, and the pair of NH is formed₃、NO₂、CH₄And the capability of high-sensitivity detection and identification and high-precision concentration measurement of harmful gases provides a miniaturized, low-power-consumption and portable high-sensitivity harmful gas sensor for users.

Drawings

FIG. 1 is a schematic diagram of the present invention;

FIG. 2 is a schematic diagram of the resonance spectrum of the optical microcavity and the spectrum shift caused by harmful gas in the present invention;

FIG. 3 is a schematic diagram of a processing apparatus for quasi-cylindrical optical microcavity in accordance with the present invention.

Description of reference numerals:

1. a laser; 2. a first connector; 3. a tapered optical fiber; 4. a first quasi-cylindrical optical microcavity; 5. a second quasi-cylindrical optical microcavity; 6. a microcavity package box; 7. an air inlet; 8. an exhaust port; 9. a second connector; 10. a photodetector; 11. a data line; 12. and (4) an upper computer.

Detailed Description

In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the invention provides a harmful gas detection device based on a whispering gallery mode optical microcavity, which comprises a laser 1, a first connector 2, a tapered optical fiber 3, an optical microcavity, a microcavity packaging box 6, a second connector 9, a photoelectric detector 10 and an upper computer 12 with gas detection software, wherein the laser 1 is connected to the input end of the tapered optical fiber 3 through the first connector 2, the photoelectric detector 10 is connected to the output end of the tapered optical fiber 3 through the second connector 9, the first connector 2 and the second connector 9 both adopt FC/APC connectors, are packaged in a butterfly shape, and the laser wavelength is modulated by adopting a triangular wave voltage signal of a signal generator.

The photoelectric detector 10 is connected with an upper computer 12 through a data line 11 in a data transmission manner, two optical micro-cavities are arranged in the micro-cavity packaging box 6, and the two optical micro-cavities are respectively a first quasi-cylindrical optical micro-cavity 4 and a second quasi-cylindrical optical micro-cavity 5.

The microcavity packaging box 6 is arranged between the laser 1 and the photoelectric detector 10, the tapered optical fiber 3 penetrates through the optical microcavity, and an air inlet 7 and an air outlet 8 are formed in the box wall of the microcavity packaging box 6.

The laser 1 adopts a distributed feedback semiconductor laser (DFB laser) with the emergent power of 5-10mW, and the working wavelength of the laser emitted by the laser is selected from the absorption wavelength (such as CH) of the harmful gas to be detected₄1653.7nm, NH₃Is 1512nm, H₂S is 1578nm), and single-mode fiber output.

The tapered optical fiber 3 is formed by drawing a corning single-mode optical fiber on an optical fiber tapering machine. Because the optical fiber tapered waveguide needs to meet adiabatic approximate conditions and the waveguide taper is required to be small enough, the optical fiber drawing platform needs to control the drawing speed, the drawing time and the flame size well in the preparation process, and the preparation process of the tapered optical fiber comprises the following steps:

(1-1) removing a cladding of the middle part of the optical fiber, and fixing the optical fiber by using an optical fiber clamp;

(1-2) enabling a flame head to be close to the position of a cladding of the optical fiber, preheating, then starting a stepping motor to pull the optical fiber to move backwards, enabling the middle part of the optical fiber to be continuously thinned in the stretching process, and turning off the stepping motor and the flame after the waist of the cone meets the condition;

(1-3) because the waveguide is very thin at the cone waist after drawing, the waveguide is inconvenient to take and place, and the drawn optical fiber is fixed on a customized quartz plate by using the light-curing adhesive to finish the preparation of the tapered optical fiber.

In this embodiment, the manufacturing requirements of the tapered optical fiber are as follows: the diameter is less than 2.2 μm, and the light transmittance of the waveguide is greater than 90%.

In order to eliminate the influence of external environment such as water vapor/temperature drift on the resonant state of the microcavity in the measurement process, two equal optical microcavities are arranged in the microcavity packaging box, wherein one optical microcavity is used for measuring the change of the external environment and is isolated from the detected harmful gas; the other optical microcavity is contacted with the detected harmful gas, and the two optical microcavities form an environment compensation type measuring structure, so that the influence of the external environment on the gas measuring precision is eliminated.

As described above, the two optical micro-cavities are the first quasi-cylindrical optical micro-cavity 4 and the second quasi-cylindrical optical micro-cavity 5, and the structures and materials of the first quasi-cylindrical optical micro-cavity 4 and the second quasi-cylindrical optical micro-cavity 5 are completely identical, and the optical micro-cavity is formed by using corning single-mode fiber through arc discharge processing of an optical fiber fusion splicer, the schematic diagram of the processing device is shown in fig. 3, and the processing process includes the following steps:

(2-1) cleaning the optical fiber with the coating layer removed, and putting the optical fiber into a V-shaped groove holder of an optical fiber fusion splicer;

and (2-2) locally softening the optical fiber by controlling the discharge of the electrode through the optical fiber fusion splicer, wherein the discharge time is about 1s, and discharging for multiple times to finally form the quasi-cylindrical optical microcavity.

The surface of the optical microcavity is coated with a dielectric layer, the dielectric layer is selected according to the type of the detected harmful gas, and the refractive index of the dielectric layer is very sensitive to the detected harmful gas.

The photoelectric detector 10 adopts a grating and photoelectric sensor type structure, and the index requirements are as follows: the optical fiber can measure 1300nm-1700nm laser spectrum, the spectral resolution is better than 0.1nm, and the tail end optical fiber is connected with the outlet of the tapered optical fiber through the FC/APC connector. The detector is used for acquiring the change of the microcavity resonance wavelength caused by harmful gas.

The upper computer 12 is a common commercial computer, and a USB-6009 data acquisition card of the American NI company is installed on the computer, and gas detection software is installed on the computer, and the software is written for LABVIEW program.

The invention also provides a detection method of the harmful gas detection device based on the whispering gallery mode optical microcavity, which comprises the following steps:

s1, turning on a power switch of the detection device, and turning on the laser, the photoelectric detector and the upper computer;

s2, selecting the transmitting laser wavelength of the laser according to the type of the detected harmful gas;

s3, enabling laser emitted by a laser to enter a conical optical fiber and a microcavity packaging box in sequence through a first connector, and entering two quasi-cylindrical optical microcavities through evanescent wave action;

s4, after the laser entering the two quasi-cylindrical optical micro-cavities is transmitted in a whispering gallery mode, the laser is emitted from the second connector and is detected by the photoelectric detector;

s5, recording a laser spectrum A when no harmful gas exists through installing gas detection software in the upper computer;

s6, introducing the detected harmful gas into the microcavity packaging box through the gas inlet, and introducing the exhausted harmful gas into the gas recovery pool through the gas outlet and the guide pipe;

s7, the detected harmful gas entering the microcavity package box through the air inlet and the surface medium of one of the quasi-cylindrical optical micro-cavities are subjected to chemical reaction, the effective refractive index of the quasi-cylindrical optical micro-cavity is changed at the moment, and the change value of the refractive index is determined by the harmful gas to be detected and the external environment (temperature, humidity and the like); the other quasi-cylindrical optical microcavity is isolated from the harmful gas to be detected, and the refractive index change value is determined by the external environment (temperature, humidity and other changes);

s8, repeating the steps S3-S5 to obtain a laser spectrum B after the harmful gas to be detected is introduced;

and S9, acquiring the type and concentration information of the detected harmful gas according to the spectrum wave band and the spectrum offset of the laser spectrum B relative to the laser spectrum A, wherein the spectrum peak height corresponds to the gas concentration, and the spectrum peak wavelength corresponds to the gas type. As shown in fig. 2, fig. 2(a) is a resonance spectrum, and fig. 2(b) is a spectrum shift diagram.

The theoretical basis of the invention is as follows:

the WGM microcavity has some advantages common to other optical sensors, such as safety, reliability, simple structure, fast response speed, etc. Meanwhile, the WGM microcavity with a high Q value has a very strong frequency-selecting effect, namely, a transmission spectrum resonance peak has a very narrow spectral line width, each whispering gallery mode corresponds to one resonance peak, light circularly propagates along the inner wall of the microcavity under the condition of total reflection, and finally a stable electromagnetic field, namely a stable mode field, is formed. Observing the mode field distribution, one part of the electric field is in the cavity, and the other part of the electric field is distributed outside the cavity in the form of evanescent waves and reacts with external substances. The geometrical dimensions of the microcavity and the refractive index of the material determine the resonant wavelength corresponding to each mode, and the material herein includes all materials of the microcavity system and the external environment. Therefore, when parameters such as the size of the microcavity or the refractive index of the material are changed, the resonance wavelength of the system is also shifted, and the shift of the resonance peak is observed to detect various parameters.

The sensing principle of the WGM microcavity refractive index is as follows: when the light wave forms a whispering gallery mode in the microcavity, the periodic resonance condition is satisfied, i.e. the resonance wavelength and the effective optical path of the light wave propagating in the microcavity are in integral multiple.

Wherein n is_effIs the effective refractive index of the microcavity system, R is the radius of the optical microcavity, f_res，λ_resRespectively the resonance frequency and the resonance wavelength, c₀Is the speed of light in vacuum and l is the angular mode number. The effective refractive index is a function n of the refractive index coefficient of the materials of which it is composed and the geometry of the resonant cavity_eff＝n_eff(n_core,n_upper,n_lower) (ii) a Wherein n is_core,n_upper,n_lowerRespectively, the refractive indices of the center, surface, and bottom of the microcavity. Any change in any one parameter will result in a change in the effective refractive index, so the refractive index sensing, i.e. the change in effective refractive index Δ n due to the change in refractive index of the out-of-cavity gas_effWhich in turn causes a corresponding change in the resonance wavelength, so that:

the change value of the microcavity resonance wavelength caused by the change of the refractive index of the gas to be detected is as follows:

therefore, the concentration of the harmful gas can be detected by detecting the change amount of the microcavity resonance wavelength.

The working principle of the invention is as follows:

firstly, the microcavity sensor is placed in a harmful gas environment, and the working wavelength of the laser in the optical microcavity is selected according to the type of the detected harmful gas. Then, the laser emits laser into the inlet end of the tapered optical fiber; the laser in the tapered optical fiber is overlapped with an evanescent field of the optical microcavity at a taper waist and enters the optical microcavity under the action of near-field coupling; the laser entering the optical microcavity continuously rotates in a whispering gallery mode in the optical microcavity and continuously acts on the microcavity wall material. At this time, the refractive index of the material of the optical microcavity surface changes due to the harmful gas, which causes the change of the effective refractive index of the optical microcavity, and further causes the change of the resonant wavelength of the laser in the optical microcavity. And then a photoelectric detector is used at the outlet end to measure the change of the microcavity resonance wavelength caused by the harmful gas, so that the concentration information of the harmful gas is obtained.

Aiming at the public safety detection requirement, the invention designs a novel harmful gas detection system by utilizing the amplification effect of the whispering gallery mode optical microcavity on the change of the refractive index of a medium caused by gas, and the invention can be used for detecting NH₃、NO₂、CH₄And the like, and has the characteristics of miniaturization, low power consumption, portability and remote monitoring.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.