Compact integrated gas monitoring system based on terahertz waves as well as detection method and application of compact integrated gas monitoring system

Abstract

The invention discloses a compact integrated gas monitoring system based on terahertz waves, which relates to the technical field of gas detection and comprises a terahertz quantum cascade laser, an information acquisition device, a first parabolic mirror, a gas chamber, a second parabolic mirror, a reflection device, a communication module, a terahertz wave frequency adjusting device and a shell. According to the system, the terahertz wave technology is utilized, and the laser wavelength corresponding to the specific gas absorption spectrum is selected, so that high-selectivity detection of target gas is realized, and interference of other gases is avoided; according to the system, a self-mixing interference technology is adopted, a laser serves as a receiver, gas is detected by monitoring voltage changes at the two ends of a QCL terminal, and the system has high safety, rich spectral information, high sensitivity to low-concentration gas, strong anti-interference capability and real-time monitoring capability; reflection and transmission of terahertz waves are adjusted through temperature control, accurate recognition of gas types and components is achieved, and an effective means is provided for environment monitoring and safety early warning.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, and in particular to a compact integrated gas monitoring system based on terahertz waves and a detection method and application thereof. Background Art

[0002] Urban sewers and septic tanks are responsible for receiving and transporting domestic sewage and industrial wastewater. However, due to their relatively closed and special environment, the organic and inorganic substances in the sewage will decompose and produce a variety of toxic, harmful, flammable and explosive gases under the action of microorganisms in closed pipes under anaerobic conditions. If they are not managed properly, it is easy to cause gas accumulation. When it reaches a certain concentration, if it leaks, it will cause poisoning to people. If it encounters an open flame, it is very easy to explode, causing casualties and endangering the personal and property safety of the people.

[0003] In recent years, due to the high concentration of flammable gas in sewers and septic tanks, explosion accidents of flammable gas in municipal sewage pipes have become frequent events. At present, the urban sewer network has problems such as unreasonable settings, irregular maintenance and management of treatment facilities, too fast urbanization, large urban population density, and high usage load of pipe network facilities. However, for example, sewers are a kind of urban public facilities, which refer to the pipes for buildings to discharge sewage and rainwater, and also refer to the underground passages for cities, factories or villages to discharge sewage and rainwater. Therefore, the urban sewer system is not only used to collect and discharge domestic wastewater generated in cities and industrial wastewater generated in industrial production. Therefore, the gas in the sewer is not only one gas, but a mixture of various gases, such as hydrogen sulfide, ammonia, biogas, methane, ethane, carbon dioxide and other gases. Many of these gases are very harmful to the human body. Therefore, in addition to actively carrying out positive environmental awareness education and improving facility maintenance, it is more important to establish a set of flammable and harmful gas monitoring and early warning mechanisms to prevent problems before they occur.

[0004] Therefore, how to provide a monitoring system that can continuously detect the content of various gases in a space such as a sewer in real time without contact and efficiently and stably is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a compact integrated gas monitoring system based on terahertz waves. The system of the present invention utilizes terahertz wave technology to achieve highly selective detection of target gas by selecting a laser wavelength corresponding to a specific gas absorption spectrum, thereby avoiding interference from other gases. The system adopts self-mixing interference technology to make the laser itself a receiver, and detects gas by monitoring the voltage changes at both ends of the QCL terminal. The system has high security, rich spectral information, high sensitivity to low-concentration gas, strong anti-interference ability and real-time monitoring ability. The reflection and transmission of terahertz waves are adjusted by temperature control to achieve accurate identification of gas types and components, providing an effective means for environmental monitoring and safety warning.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A compact integrated gas monitoring system based on terahertz waves, comprising a terahertz quantum cascade laser, an information acquisition device, a first parabolic mirror, a gas chamber, a second parabolic mirror, a reflecting device, a communication module, a terahertz wave frequency adjustment device and a housing;

[0008] Wherein, the terahertz quantum cascade laser is used to generate a first laser beam;

[0009] The first parabolic mirror is used to change the path of the first laser beam so that the first laser beam is emitted to the gas chamber;

[0010] The gas chamber is used to irradiate the first laser beam on the gas to be detected to generate a second laser beam carrying the sample to be detected, and emit it to the second parabolic mirror;

[0011] The second parabolic mirror is used to change the path of the second laser beam so that the second laser beam is emitted into the reflecting device;

[0012] The reflecting device comprises at least four reflecting mirrors and one plane reflecting mirror, wherein the reflecting mirror is used to reflect and amplify the second laser beam for multiple times and finally project it onto the plane reflecting mirror, and the plane reflecting mirror is used to reflect the second laser beam and make it return along the same optical path;

[0013] The information collection device is used to collect and analyze the signal and determine the components of its main frequency, thereby obtaining the terahertz spectrum of the ambient gas and determining the gas content;

[0014] The terahertz wave frequency adjustment device is used to adjust the terahertz wave frequency band, enabling the device to achieve multi-band measurement;

[0015] The communication module transmits the collected data to the remote monitoring device;

[0016] The terahertz quantum cascade laser, the information collection device, the first parabolic mirror, the gas chamber, the second parabolic mirror, the reflecting device, the communication module, and the terahertz wave frequency adjustment device are all arranged in the housing.

[0017] Terahertz QCL can accurately select the laser wavelength corresponding to each gas absorption spectrum and detect only the gas that needs to be monitored without interference from other gases. For example, by adjusting the laser wavelength to the specific absorption line of the methane molecule (such as in the near-infrared band), highly selective detection can be achieved, and the methane concentration can be detected in situ and in real time in the dangerous environment of the sewer, without the need for complicated sample collection and pretreatment processes, and can effectively avoid harm to workers; at the same time, it can be installed at a suitable location at the sewer outlet to continuously monitor the concentration of hazardous gases and provide relevant information to sewer managers in a timely manner so that they can take appropriate measures; because laser detection is a non-contact detection method, it will not cause any physical damage to workers and will not affect the environment in the sewer, which can effectively avoid the generation of additional harmful gases.

[0018] In addition, terahertz waves have rich spectral information. Each gas molecule has a unique absorption spectrum in the terahertz band, which is as unique as a fingerprint. By measuring the absorption spectrum of the gas in the terahertz band, the type and composition of the gas can be accurately identified. Even for gases with very similar chemical properties, they can be distinguished by terahertz spectroscopy technology, which is very important for monitoring trace impurities in hazardous gases or different components in mixed gases. It is also sensitive to low-concentration gases. In the early stages of a hazardous gas leak, the leakage may be small and the concentration low, but terahertz wave monitoring technology can still effectively detect these trace gas leaks, issue early warnings, and buy precious time for taking emergency measures.

[0019] Preferably, the reflecting device includes a first reflector, a second reflector, a third reflector, a fourth reflector and a plane reflector, the first reflector is used to reflect the second laser beam to the second reflector, the second reflector is used to reflect the second laser beam to the third reflector, the third reflector is used to reflect the second laser beam to the fourth reflector, the fourth reflector is used to reflect the second laser beam to the plane reflector, and the plane reflector is used to reflect the second laser beam and return it along the same optical path.

[0020] Preferably, a first Brewster angle window and a second Brewster angle window are respectively provided on both sides of the gas chamber, and the first laser beam passes through the first Brewster angle window to reach the inner cavity of the gas chamber to be measured, and then passes through the second Brewster angle window to be emitted to the second parabolic mirror.

[0021] Preferably, the gas chamber is connected to the external environment through a gas duct.

[0022] Preferably, the first reflector, the second reflector, the third reflector and the fourth reflector are elliptical cross-section reflectors, and the plane reflector is a circular cross-section reflector.

[0023] Preferably, the upper portion of the shell adopts a conical design so that the liquid can flow down along the wall and will not stay on the top of the shell; the bottom of the shell adopts a concave design to prevent the liquid from flowing back into the interior of the shell;

[0024] A clamping structure is provided on the top of the shell.

[0025] Preferably, the housing is made of stainless steel to protect the system from corrosion.

[0026] Preferably, the terahertz quantum cascade laser has a gain bandwidth of 3.4-3.7 THz, and the structure is grown on a semi-insulating GaAs substrate using molecular beam epitaxy technology.

[0027] Preferably, the structure is specifically as follows: after the initial 250-280 nm thick GaAs buffer layer, there is a 300-340 nm thick Al0.5Ga0.5As etch stop layer, a 700-800 nm thick n-GaAs contact layer, a 12.8-13.1 μm thick AR anti-reflection layer and a 50-54 nm thick n-GaAs top contact layer, and then a 150-153 μm wide gold plasma ridge waveguide structure is determined by photolithography technology;

[0028] Wherein, the Si doping density of the n-GaAs contact layer is ρ=3~3.2×10 18 cm -3 The Si doping density of the n-GaAs top contact layer is ρ=5~5.2×10 18 cm -3 .

[0029] Preferably, the internal structure of the terahertz wave frequency adjustment device is, from top to bottom, an incident window, an upper plate, a liquid crystal layer, a lower plate and an exit window, the upper plate and the lower plate are connected to a voltage controller, and the voltage controller is also connected to a frequency monitor.

[0030] Preferably, the liquid crystal layer uses cholesteric liquid crystal material, and the arrangement of liquid crystal molecules can be changed only by voltage control. The incident window and the exit window materials use high-resistivity silicon, and the voltage controller uses a high-precision digital power supply, which can output precise voltage values ​​according to user input or preset programs to change the reflection and transmission of terahertz waves.

[0031] According to the above-mentioned detection method of a compact integrated gas monitoring system based on terahertz waves, it is characterized by comprising the following steps:

[0032] The first laser beam emitted by the terahertz quantum cascade laser passes through a terahertz wave frequency adjustment device to adjust the terahertz wave frequency to a desired frequency band, and then is guided to the first Brewster angle window through a first parabolic mirror, passes through the window to reach the gas chamber to be measured to obtain a second laser beam, and then the second laser beam passes through the second Brewster angle window and is emitted to the second parabolic mirror, and the second laser beam is incident on the reflective mirror of the reflection device in a low-loss state, is amplified after multiple reflections, and finally is incident on a plane reflector to reflect the second laser beam, so that it returns to the terahertz quantum cascade laser along the same optical path, and finally uses an information collector to collect and analyze the signal and determine the component of its main frequency, thereby obtaining the terahertz spectrum of the ambient gas, and the terahertz absorption spectrum of the detected environment is compared with the terahertz database of the gas, thereby judging the gas content.

[0033] As described above, a compact integrated gas monitoring system based on terahertz waves is used in real-time monitoring of gas content.

[0034] Preferably, the gas is a flammable gas, such as methane.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) High safety: The terahertz wave photon energy of the system of the present invention is low and will not cause ionizing radiation damage to the human body. It is a relatively safe detection method and can be used for long-term monitoring in crowded places or areas with high safety requirements without worrying about adverse effects on the health of surrounding personnel;

[0037] (2) Rich spectral information: Since each gas molecule has a unique absorption spectrum in the terahertz band, which is as unique as a fingerprint, the system of the present invention can accurately identify the type and composition of the gas by measuring the absorption spectrum of the gas in the terahertz band. Even for gases with very similar chemical properties, they can be distinguished by terahertz spectroscopy technology, which is very important for monitoring trace impurities in dangerous gases or different components in mixed gases.

[0038] (3) Sensitive to low-concentration gases: In the early stage of a dangerous gas leak, the leak may be small and the concentration is low. The terahertz wave monitoring technology of the system of the present invention can still effectively detect these trace gas leaks and issue early warnings in time, thus buying precious time for taking emergency measures;

[0039] (4) Strong anti-interference ability: The terahertz wave used in the system of the present invention has a higher frequency, which is significantly different from the frequency of common electromagnetic interference signals (such as radio waves, microwaves, etc.). Therefore, it has a strong anti-interference ability in a complex electromagnetic environment and can accurately monitor hazardous gases in the presence of other electromagnetic signal interference, thereby ensuring the reliability of the monitoring results.

[0040] (5) Real-time monitoring: The terahertz wave detection system of the present invention can realize rapid spectral measurement and data collection, and can monitor dangerous gases online in real time, and promptly reflect the changes in gas concentration. Once the gas concentration exceeds the safety threshold, an alarm will be immediately issued so that relevant personnel can take timely measures to prevent the occurrence of dangerous accidents.

[0041] (6) The terahertz band adjustment structure is simple: the system of the present invention does not require a complex electrode structure. Since the liquid crystal layer adopts cholesteric liquid crystal material, the arrangement of liquid crystal molecules can be changed only by voltage control. By using a high-precision digital power supply, it can output precise voltage values ​​according to user input or preset programs to change the reflection and transmission of terahertz waves, and can adjust the reflection and transmission band of terahertz waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings in this description are only embodiments of the present invention.

[0043] Figure 1 This is a structural diagram of a compact integrated gas monitoring system based on terahertz waves of the present invention;

[0044] Figure 2 This is a structural diagram of the terahertz wave frequency adjustment device of the present invention. DETAILED DESCRIPTION

[0045] Embodiments of the present invention are described below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but are not to be construed as limiting the present invention.

[0046] Example 1

[0047] like Figure 1 The present invention provides a compact integrated gas monitoring system based on terahertz waves, which is used for detecting the content of combustible gas in sewers and septic tanks, and specifically includes a terahertz quantum cascade laser 14, an information collection device 15, a first parabolic mirror 5, a glass gas chamber 3, a second parabolic mirror 6, a reflecting device, a wireless communication module 16, a terahertz wave frequency adjustment device 17 and a housing 7;

[0048] The terahertz quantum cascade laser 14 is used to generate the first laser beam. Furthermore, the QCL active region is designed to have a size set to a 3.4-3.7 THz gain bandwidth, and the structure is grown on a semi-insulating GaAs substrate using molecular beam epitaxy technology. The specific method is as follows: after the initial 280 nm thick GaAs buffer layer, there is a 340 nm thick Al0.5Ga0.5As etching stop layer and an 800 nm thick n-GaAs contact layer, and the Si doping density in the n-GaAs contact layer is ρ=3×1018cm -3 , then 120 cycles of AR (anti-reflection) layer were grown to a thickness of 12.8 μm, followed by 54 nm thick n-GaAs (Si doping density ρ = 5 × 1018 cm -3 ) top contact layer; using photolithography to determine a 153 μm wide gold plasma ridge waveguide structure and cut it into 1.9 mm long;

[0049] Further, the first parabolic mirror 5 is used to change the path of the first laser beam so that the first laser beam is emitted to the glass gas chamber 3;

[0050] Further, the glass gas chamber 3 is used to irradiate the first laser beam on the gas to be detected to generate a second laser beam carrying the sample to be detected, and emit it to the second parabolic mirror; further, a first Brewster angle window 4 and a second Brewster angle window 2 are respectively provided on both sides of the glass gas chamber 3, the first laser beam passes through the first Brewster angle window 4 to reach the inner cavity of the glass gas chamber 3 to be detected, and then passes through the second Brewster angle window 2 to be emitted to the second parabolic mirror 6; the glass gas chamber 3 is connected to the external environment through the gas guide duct 8, connecting the gas chamber 3 with the external environment, so that the system can measure the combustible gas content in the environment in real time;

[0051] Further, the second parabolic mirror 6 is used to change the path of the second laser beam so that the second laser beam is emitted into the reflection device;

[0052] Furthermore, the reflecting device comprises a first reflecting mirror 9 with an elliptical cross-section, a second reflecting mirror 10 with an elliptical cross-section, a third reflecting mirror 11 with an elliptical cross-section, a fourth reflecting mirror 12 with an elliptical cross-section and a plane reflecting mirror 13 with a circular cross-section, the first reflecting mirror 9 is used to reflect the second laser beam to the second reflecting mirror 10, the second reflecting mirror 10 is used to reflect the second laser beam to the third reflecting mirror 11, the third reflecting mirror 11 is used to reflect the second laser beam to the fourth reflecting mirror 12, the fourth reflecting mirror 12 is used to reflect the second laser beam to the plane reflecting mirror 13, the plane reflecting mirror 13 is used to reflect the second laser beam to return along the same optical path, the optical path is increased by reflecting and amplifying the second laser beam in three dimensions and multiple times in the reflecting device, and the plane reflecting mirror 13 with a circular cross-section is used to reflect the second laser beam to reflect it back to the terahertz quantum cascade laser 14 along the same optical path;

[0053] Furthermore, the information collection device 15 is a multifunctional multi-channel information collection instrument, which is used to collect and analyze signals and determine the components of their main frequencies, thereby obtaining the terahertz spectrum of the ambient gas and determining the real-time content of the gas;

[0054] Furthermore, the wireless communication module 16 uses a WiFi module to allow the device to access the local wireless network and send its own data to the cloud server;

[0055] Furthermore, the terahertz wave frequency adjustment device 17 is as follows Figure 2 As shown, there is a cholesteric liquid crystal layer 20 inside, and a terahertz wave incident window 18 and an exit window 22 are respectively arranged on both sides of the liquid crystal layer 20. The upper and lower parts of the liquid crystal layer 20 are respectively an upper plate 19 and a lower plate 21. A voltage controller 23 is connected to the upper plate 19 and the lower plate 21. The voltage controller 23 uses a high-precision digital power supply and is also equipped with a frequency monitor 24. The terahertz wave frequency adjustment device 17 has a liquid crystal layer 20 made of cholesteric liquid crystal material. The arrangement of liquid crystal molecules can be changed under the action of an external electric field. The thickness of the liquid crystal layer 20 is 120 μm. The liquid crystal layer 20 is placed between the two The liquid crystal layer 20 is provided with a transparent conductive electrode plate, the electrode plate is connected to an external voltage regulating source, and an incident window 18 and an exit window 22 for the terahertz wave are respectively arranged on both sides of the liquid crystal layer 20, and the window material uses high-resistivity silicon to ensure the high transmittance of the terahertz wave; a voltage controller 23 is connected to the electrode plate of the liquid crystal layer 20, and the voltage controller 23 uses a high-precision digital power supply, which can output an accurate voltage value according to user input or a preset program; at the same time, a frequency monitor 24 is equipped to monitor the output frequency of the terahertz wave in real time, so as to feedback and adjust the voltage to achieve more accurate frequency control;

[0056] The terahertz quantum cascade laser 14, the information collection device 25, the first parabolic mirror 5, the gas chamber 3, the second parabolic mirror 6, the reflection device, the wireless communication module 16, and the terahertz wave frequency adjustment device 17 are all arranged in the housing 7;

[0057] Furthermore, the shell 7 is a 5 mm thick stainless steel shell, which can prevent the device from being corroded by wastewater. A bolt clamping clip 1 is designed on the upper part of the shell 7, and a layer of rubber anti-skid is added around the clip 1, so that the entire monitoring system can be firmly suspended on the inside of the sewer. The upper part of the shell 7 adopts a conical design, so that liquids such as rainwater can flow down the wall and will not be retained on the top of the device; the bottom of the shell 7 adopts a concave design to prevent water from flowing back into the device; in the internal space of the shell 7, the terahertz radiation emitted from the QCL is collimated by a silver-plated 90° off-axis first parabolic mirror 5 with a diameter of 10 mm and an effective focal length of 50 mm, and is guided through a 4 cm long glass gas chamber 3, and two 3 mm thick polymethylpentene first Brewster angle windows are set on both sides of the glass gas chamber 3. The opening 4 and the second Brewster angle window 2 allow the flat-band terahertz to be transmitted with a loss of less than 0.5%. After passing through the second Brewster angle window 2, the light wave is guided to the designed reflection device through the second parabolic mirror 6. The four 10mm diameter elliptical cross-section silver-plated mirrors are reflected multiple times and continuously amplified. At the final end of this system, a final circular cross-section plane reflector 13 is used to reflect the terahertz beam along the same optical path and return to the QCL cavity, repeatedly reflecting the light back to the active area, thereby increasing the gain length of the light in the active area; finally, the data is processed by a multifunctional multi-channel information acquisition instrument 15 (DAQ), and the collected data is transmitted to the remote monitoring device through the equipped wireless communication module 16, which is convenient for users to view;

[0058] In order to achieve the purpose of small size and compactness, the present invention adopts self-mixing interference technology, which can well avoid the problem of excessive receiver volume, so that the laser itself is used as a receiver. The light wave emitted by the laser increases the optical path through a series of reflections and finally returns to the laser cavity. The light wave will have corresponding effects when passing through different gases. The voltage at both ends of the QCL terminal can be well monitored through the AC coupling data acquisition board. It is only necessary to record the perturbation caused by the SM that changes with time, and use a constant DC current to bias the QCL; the resulting terahertz feedback phase shift causes a periodic SM interference effect in the QCL, and the corresponding voltage disturbance v SM(t) is recorded as a function of the round-trip delay time. Finally, the frequency spectrum of the interference pattern measured in real time can be obtained by fast Fourier transform, and the regression Gaussian function is used to analyze the signal and determine the component of its main frequency. The terahertz absorption spectrum of the detected environment is compared with the terahertz database of dangerous gases such as methane to finally determine whether its content is within the normal controllable range. At the same time, a terahertz wave frequency adjustment device is set up, and the liquid crystal layer inside the adjustment device adopts cholesteric liquid crystal material, and two electrode plates are distributed above and below the liquid crystal layer, so that we can change the arrangement of liquid crystal molecules only by voltage control. Finally, a high-precision digital power supply can output precise voltage values ​​according to user input or preset programs to change the reflection and transmission of terahertz waves, so as to achieve the purpose of changing the terahertz frequency.

[0059] Application Examples

[0060] With the advancement of smart city construction, smart underground pipe networks and smart integrated pipe corridors have become an important part of smart city services. By integrating underground gas, power supply, water supply and sewer pipe networks, using sensor technology and mobile communication technology, real-time dynamic detection of the status of underground pipe networks can be achieved.

[0061] In this context, by deploying the compact integrated gas monitoring system of Example 1 of the present invention, toxic, harmful and combustible gas components in the underground pipe network are analyzed online 24 hours a day, and real-time alarm, ventilation and emergency response are performed through the monitoring system. One of the core components of the gas monitoring system is the internal liquid crystal layer, which adopts cholesteric liquid crystal material. Two electrode plates are distributed above and below the liquid crystal layer. The arrangement of liquid crystal molecules can be changed only by voltage control. The system can monitor the gas concentration in the sewer in real time to ensure timely discovery of potential safety hazards.

[0062] When methane gas enters the gas chamber through the gas duct, the system can measure the methane gas content in the environment in real time; a laser beam is emitted from the QCL into the terahertz wave frequency adjustment device, the terahertz wave frequency is adjusted to the frequency band for measuring methane, and then the outgoing laser beam is irradiated on the gas to be detected to generate a second laser beam carrying the sample to be detected, and then emitted to the second parabolic mirror; further, a first Brewster angle window and a second Brewster angle window are respectively provided on both sides of the glass gas chamber, the first laser beam passes through the first Brewster angle window to reach the inner cavity of the glass gas chamber to be tested, and then passes through the second The light is emitted from the Brewster angle window to the second parabolic mirror, and finally the laser beam is emitted into the reflection area. The signal is continuously amplified after multiple reflections, and finally the terminal of this system is completed by a final circular cross-section plane reflector, which is used to reflect the terahertz light beam along the same optical path and return to the QCL cavity, repeatedly reflecting the light back to the active area, thereby increasing the gain length of the light in the active area; finally, the data is processed by a multi-functional multi-channel information acquisition instrument, and the collected methane real-time concentration data is transmitted to the remote monitoring equipment through the equipped wireless communication module for user viewing.

[0063] When the methane gas concentration exceeds the preset safety threshold, the system will trigger the alarm mechanism and remind relevant personnel to take treatment measures by sending alarm information, etc.; when the methane gas concentration does not exceed the preset safety threshold, the system will not send an alarm message.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact integrated gas monitoring system based on terahertz waves, characterized in that: It includes a terahertz quantum cascade laser, an information collection device, a first parabolic mirror, a gas chamber, a second parabolic mirror, a reflecting device, a communication module, a terahertz wave frequency adjustment device and a housing; Wherein, the terahertz quantum cascade laser is used to generate a first laser beam; The first parabolic mirror is used to change the path of the first laser beam so that the first laser beam is emitted to the gas chamber; The gas chamber is used to irradiate the first laser beam on the gas to be detected to generate a second laser beam carrying the sample to be detected, and emit it to the second parabolic mirror; The second parabolic mirror is used to change the path of the second laser beam so that the second laser beam is emitted into the reflecting device; The reflecting device comprises at least four reflecting mirrors and one plane reflecting mirror, wherein the reflecting mirror is used to reflect and amplify the second laser beam for multiple times and finally project it onto the plane reflecting mirror, and the plane reflecting mirror is used to reflect the second laser beam and make it return along the same optical path; The information collection device is used to collect and analyze the signal and determine the components of its main frequency, thereby obtaining the terahertz spectrum of the ambient gas and determining the gas content; The terahertz wave frequency adjustment device is used to adjust the terahertz wave frequency band, enabling the device to achieve multi-band measurement; The communication module transmits the collected data to the remote monitoring device; The terahertz quantum cascade laser, the information collection device, the first parabolic mirror, the gas chamber, the second parabolic mirror, the reflecting device, the communication module, and the terahertz wave frequency adjustment device are all arranged in the housing.

2. A compact integrated gas monitoring system based on terahertz waves according to claim 1, characterized in that: A first Brewster's angle window and a second Brewster's angle window are respectively provided on both sides of the gas chamber. The first laser beam passes through the first Brewster's angle window to reach the inner cavity of the gas chamber to be measured, and then passes through the second Brewster's angle window to be emitted to the second parabolic mirror.

3. A compact integrated gas monitoring system based on terahertz waves according to claim 1, characterized in that: The gas chamber is connected to the external environment through a gas-conducting pipeline.

4. A compact integrated gas monitoring system based on terahertz waves according to claim 1, characterized in that: The four reflectors are reflectors with elliptical cross sections, and the plane reflector is a reflector with circular cross sections.

5. The compact integrated gas monitoring system based on terahertz waves according to claim 1, characterized in that: The upper part of the shell adopts a conical design so that the liquid can flow down along the wall and will not stay on the top of the shell; the bottom of the shell adopts a concave design to prevent the liquid from flowing back into the interior of the shell; A clamping structure is provided on the top of the shell.

6. The compact integrated gas monitoring system based on terahertz waves according to claim 1, characterized in that: The terahertz quantum cascade laser has a gain bandwidth of 3.4-3.7 THz, and the structure is grown on a semi-insulating GaAs substrate using a molecular beam epitaxy technique.

7. A compact integrated gas monitoring system based on terahertz waves according to claim 6, characterized in that: The structure is specifically as follows: after the initial 250-280nm thick GaAs buffer layer, there is a 300-340nm thick Al0.5Ga0.5As etch stop layer, a 700-800nm ​​thick n-GaAs contact layer, a 12.8-13.1μm thick AR anti-reflection layer and a 50-54nm thick n-GaAs top contact layer, and then a 150-153μm wide gold plasma ridge waveguide structure is determined by photolithography technology; Wherein, the Si doping density of the n-GaAs contact layer is ρ=3~3.2×10 18 cm -3 The Si doping density of the n-GaAs top contact layer is ρ=5~5.2×10 18 cm -3 .

8. The compact integrated gas monitoring system based on terahertz waves according to claim 1, characterized in that: The internal structure of the terahertz wave frequency adjustment device is, from top to bottom, an incident window, an upper plate, a liquid crystal layer, a lower plate and an exit window. The upper plate and the lower plate are connected to a voltage controller, and the voltage controller is also connected to a frequency monitor.

9. A detection method for a compact integrated gas monitoring system based on terahertz waves according to any one of claims 1 to 9, characterized in that: The following steps are involved: The first laser beam emitted by the terahertz quantum cascade laser first passes through a terahertz wave frequency adjustment device to adjust the frequency of the terahertz wave to a required frequency band and then is emitted. The first laser beam is guided to the first Brewster angle window through a first parabolic mirror, and then passes through the window to reach the gas chamber to be measured to obtain a second laser beam. The second laser beam then passes through the second Brewster angle window and is emitted to the second parabolic mirror. The second laser beam is incident on the reflective mirror of the reflection device in a low-loss state, amplified after multiple reflections, and finally incident on a plane reflector to reflect the second laser beam, so that it returns to the terahertz quantum cascade laser along the same optical path. Finally, an information collector is used to collect and analyze the signal and determine the component of its main frequency, thereby obtaining the terahertz spectrum of the ambient gas, and the terahertz absorption spectrum of the detected environment is compared with the terahertz database of the gas to determine the gas content.

10. Application of a compact integrated gas monitoring system based on terahertz waves as claimed in any one of claims 1 to 8 in real-time monitoring of gas content.

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