Gas sample cell and terahertz time-domain spectroscopy detection system

Abstract

This utility model discloses a gas sample cell and a terahertz time-domain spectroscopy detection system, relating to the technical field of trace gas detection. The gas sample cell includes: a cylindrical sealed cavity for gas sample storage, with polyethylene windows at both ends of the cavity; an inlet assembly and an outlet assembly arranged sequentially along the length of the cavity on the side wall; a connecting assembly including two fixing plates arranged sequentially along the length of the cavity, and multiple connecting screws and connecting nuts; the polyethylene windows correspond one-to-one with the fixing plates and are sealed and embedded in the fixing plates; the multiple connecting screws pass parallel through the two fixing plates, and the connecting nuts are threaded to the ends of the connecting screws; a bracket is connected to the connecting assembly to fix the gas sample cell in the terahertz optical path of the terahertz time-domain spectrometer. The gas sample cell of this utility model has a simple structure, small volume, and no significant absorption in the terahertz band.

Description

Technical Field

[0001] This utility model relates to the technical field of trace gas detection, and in particular to a gas sample cell and a terahertz time-domain spectroscopy detection system. Background Technology

[0002] In industrial production, especially in complex environments such as coking, steelmaking, ironmaking, and petrochemicals, real-time monitoring of gas concentrations not only improves production efficiency but also ensures personnel safety. Gas concentration detection is not only related to sustainable economic and social development but also closely linked to people's daily lives and health. Terahertz time-domain spectroscopy can simultaneously obtain the amplitude and phase information of the terahertz pulse signal of the sample under test, and it also has advantages such as high sensitivity, high signal-to-noise ratio, high resolution, and wide spectral range. Therefore, terahertz time-domain spectroscopy is widely used in the field of trace gas detection.

[0003] In terahertz time-domain spectroscopy experiments, the primary function of the sample cell is to hold and fix the sample under test. The sample cell provides a stable environment, ensuring the sample remains stationary during the test, thereby reducing the influence of external factors on the experimental results. Existing gas sample cells suffer from drawbacks such as complex structure, large size, and absorption characteristics in the terahertz band. Therefore, we need a gas sample cell that is compact, portable, and easy to install, while also being flexible enough to be applied to various types of terahertz time-domain spectroscopy systems to meet diverse experimental needs. Utility Model Content

[0004] This invention provides a gas sample cell and a terahertz time-domain spectroscopy detection system, which solves the problems of existing gas sample cells having complex structures, large volumes, and absorption characteristics in the terahertz band.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a gas sample cell, including a gas sample storage cell, an inlet component, an outlet component, a connecting component, and a support.

[0007] The gas sample storage cell is a cylindrical sealed cavity made of polyethylene material, and polyethylene windows are provided at both ends of the cavity.

[0008] The air inlet assembly and the air outlet assembly are sequentially arranged on the side wall of the cavity along the length of the cavity, and are used to control the injection and recovery of the gas to be tested, respectively.

[0009] The connecting assembly includes two fixing plates arranged sequentially along the length of the cavity, as well as a plurality of connecting screws and connecting nuts; the polyethylene window sheet corresponds one-to-one with the fixing plate, and the polyethylene window sheet is sealed and embedded on the fixing plate; the plurality of connecting screws pass through the two fixing plates in parallel, and the connecting nuts are threaded to the ends of the connecting screws;

[0010] The bracket is connected to the connecting assembly and is used to fix the gas sample cell in the terahertz optical path of the terahertz time-domain spectrometer.

[0011] In one possible implementation, there are three connecting screws, and the three connecting screws are evenly spaced around the outer periphery of the polyethylene window.

[0012] In one possible implementation, both the intake assembly and the exhaust assembly include a polyethylene pipe and a polyethylene piston;

[0013] The polyethylene pipe is connected to the side wall of the cavity, and the polyethylene piston passes through the polyethylene pipe. The polyethylene piston is provided with an air hole. Rotating the polyethylene piston can realize the connection and disconnection of the air hole and the polyethylene pipe.

[0014] In one possible implementation, the polyethylene pipe has a length of 3 to 3.5 cm and a diameter of 0.4 to 0.6 cm.

[0015] In one possible implementation, the distance between the polyethylene pipe and its nearest polyethylene window is 0.4 to 0.6 cm.

[0016] In one possible implementation, the diameter of the cavity is 3.5 to 4 cm, and the length of the cavity is 5 to 6 cm.

[0017] In one possible implementation, the thickness of the polyethylene window sheet is 0.15–0.2 mm.

[0018] Secondly, this utility model provides a terahertz time-domain spectroscopy detection system, including a femtosecond laser, a beam splitter, a first delay mirror unit, a gallium arsenide crystal, a parabolic mirror, a second delay mirror unit, a polarizing mirror, a zinc telluride crystal, a polarizing beam splitter, a differential detector, a lock-in amplifier, a computer, and a gas sample cell as described in any one of the above; the gas sample cell is filled with the gas to be measured;

[0019] The femtosecond laser is used to emit detection laser;

[0020] The beam splitter is disposed in the optical path of the detection laser and is used to split the detection laser into pump light and probe light that are perpendicular to each other.

[0021] The pump light is focused onto the gallium arsenide crystal by the first delay mirror unit, exciting a terahertz wave. The terahertz wave is focused onto the gas sample cell by the parabolic reflector, resulting in pump light carrying sample information.

[0022] The probe light passes sequentially through the second delay mirror unit and the polarizing mirror, and then converges with the pump light carrying sample information onto the zinc telluride crystal to form the test light;

[0023] The test light is sequentially processed by the polarization beam splitter, differential detector, and lock-in amplifier before being sent to the computer.

[0024] In one possible implementation, both the first delay mirror unit and the second delay mirror unit include a reflector and a lens.

[0025] In one possible implementation, an opaque encapsulation box is also included, in which the beam splitter, the first delay mirror unit, the gallium arsenide crystal, the parabolic mirror, the second delay mirror unit, the polarizing mirror, the zinc telluride crystal, the polarizing beam splitter prism, and the differential detector are all sealed together within the encapsulation box.

[0026] The encapsulation box is filled with nitrogen gas, and the humidity inside the encapsulation box is less than 5%.

[0027] The gas sample cell provided in this embodiment is mainly made of polyethylene material for storing the gas to be tested. This material not only has good chemical stability but also has extremely low manufacturing cost, making the production and popularization of gas sample cells very economical. The gas sample storage cell made of polyethylene material can also ensure no significant absorption in the terahertz band, making it suitable for application scenarios that use terahertz technology to detect the gas to be tested. The polyethylene window used not only has no significant absorption in the terahertz band but also has high transmittance and low cost. The gas sample cell of this invention consists of a gas sample storage cell, an inlet component, an outlet component, a connecting component, and a support. The structure is very simple, and it can be designed to be very compact, easy to carry and install, and can be flexibly applied to different types of terahertz time-domain spectroscopy systems to meet diverse experimental needs.

[0028] The terahertz time-domain spectroscopy detection system provided in this embodiment first injects the collected gas into a gas sample cell before detection. Compared to directly using discrete air samples, this terahertz time-domain spectroscopy detection system can obtain more amplitude and phase information through terahertz pulses, enabling the detection of lower concentrations of hazardous gases. This terahertz time-domain spectroscopy detection system, based on femtosecond laser and photoconductive antenna terahertz time-domain spectroscopy technology, achieves hazardous gas detection. Compared to conventional gas detection technologies and absorption spectroscopy detection technologies, this solution has significant advantages. Furthermore, the terahertz pulse width is on the picosecond scale, providing high time resolution, and coherent measurement can simultaneously obtain amplitude and phase information. Attached Figure Description

[0029] Figure 1 A front view of a gas sample cell provided for an embodiment of this utility model;

[0030] Figure 2 A left view of a gas sample cell provided for an embodiment of this utility model;

[0031] Figure 3 A top view of a gas sample cell provided for an embodiment of this utility model;

[0032] Figure 4 A three-dimensional structural schematic diagram of a gas sample cell provided for an embodiment of this utility model;

[0033] Figure 5 A schematic diagram of a terahertz time-domain spectroscopy detection system provided for an embodiment of this utility model.

[0034] Figure labels and descriptions:

[0035] 1. Gas sample cell; 11. Gas sample storage cell; 111. Polyethylene window; 12. Gas inlet assembly; 121. Polyethylene tube; 122. Polyethylene piston; 13. Gas outlet assembly; 14. Connecting assembly; 141. Fixing plate; 142. Connecting screw; 143. Connecting nut; 15. Bracket; 2. Terahertz time-domain spectroscopy detection system; 21. Femtosecond laser; 22. Beam splitter; 23. First delay mirror unit; 24. Gallium arsenide crystal; 25. Parabolic mirror; 26. Second delay mirror unit; 27. Polarizing mirror; 28. Zinc telluride crystal; 29. ​​Polarizing beam splitter prism; 210. Differential detector; 211. Lock-in amplifier; 212. Computer. Detailed Implementation

[0036] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0037] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, the use of "based on" or "according to" implies openness and inclusiveness, because processes, steps, calculations, or other actions "based on" or "according to" one or more of the stated conditions or values ​​may in practice be based on additional conditions or beyond the stated values.

[0038] To address the problems of existing gas sample cells being complex in structure, large in volume, and having absorption characteristics in the terahertz band, this invention provides a gas sample cell and a terahertz time-domain spectroscopy detection system.

[0039] like Figures 1-4 As shown, this utility model embodiment provides a gas sample cell, including a gas sample storage cell 11, an inlet component 12, an outlet component 13, a connecting component 14, and a support 15.

[0040] The gas sample storage cell 11 is a cylindrical sealed cavity made of polyethylene material, and polyethylene windows 111 are provided at both ends of the cavity.

[0041] In other words, the gas sample storage cell 11 is made entirely of polyethylene material, which has no significant absorption in the terahertz band and is suitable for application scenarios that use terahertz technology to detect the gas to be tested.

[0042] The air intake assembly 12 and the air outlet assembly 13 are arranged sequentially along the length of the cavity on the side wall of the cavity, and are used to control the injection and recovery of the gas to be tested, respectively.

[0043] The connecting assembly 14 includes two fixing plates 141 arranged sequentially along the length of the cavity, as well as a plurality of connecting screws 142 and connecting nuts 143.

[0044] The polyethylene window slab 111 corresponds one-to-one with the fixing plate 141, and the polyethylene window slab 111 is sealed and embedded in the fixing plate 141. Multiple connecting screws 142 pass through the two fixing plates 141 in parallel, and the connecting nut 143 is threaded to the end of the connecting screw 142.

[0045] The bracket 15 is connected to the connecting assembly 14 to fix the gas sample cell 1 in the terahertz optical path of the terahertz time-domain spectrometer.

[0046] Specifically, the gas sample storage cell 11 is fixed in the terahertz optical path by a bracket 15 that works with the terahertz time-domain spectrometer, so that the terahertz light wave can pass through the gas sample storage cell 11.

[0047] The air inlet assembly 12 and the air outlet assembly 13 are respectively located on the left and right sides of the bracket 15, and are used to inject and empty the gas to be tested into the gas sample storage pool 11. The gas sample storage pool 11 is used to store the gas to be tested.

[0048] The gas sample storage cell 11 adopts a tight structural layout. Through the setting of the gas inlet component 12 and the gas outlet component 13, it is ensured that the gas to be tested can smoothly enter or flow out of the gas sample storage cell 11. It also enables the gas sample storage cell 11 to be reused multiple times, extending the service life of the gas sample cell 1.

[0049] The fixing plates 141 installed at both ends of the gas sample storage pool 11 can effectively ensure the stability and safety of the gas sample storage pool 11 during transportation and use, and can also greatly improve the sealing performance of the gas sample storage pool 11. This ensures that the gas sample storage pool 11 can be tightly sealed when the gas to be tested is being tested, preventing leakage of the gas to be tested, thereby ensuring the safety of the testing personnel and avoiding potential risks.

[0050] Furthermore, there are three connecting screws 142, and the three connecting screws 142 are evenly distributed on the outer periphery of the polyethylene window slab 111.

[0051] In other words, the fixing plates 141 located at both ends of the gas sample storage pool 11 are connected by three connecting screws 142, which are evenly distributed on the outer periphery of the polyethylene window 111.

[0052] Furthermore, both the intake assembly 12 and the exhaust assembly 13 include a polyethylene pipe 121 and a polyethylene piston 122.

[0053] A polyethylene pipe 121 is connected to the side wall of the cavity, and a polyethylene piston 122 is inserted through the polyethylene pipe 121. The polyethylene piston 122 is provided with an air hole. Rotating the polyethylene piston 122 can realize the connection and disconnection between the air hole and the polyethylene pipe 121.

[0054] Specifically, the polyethylene piston 122 is tightly fitted with the polyethylene tube 121. When the polyethylene piston 122 rotates to a specific position, the vent connects with the interior of the polyethylene tube 121, allowing the gas to be tested to flow through the vent. Furthermore, the polyethylene material has excellent corrosion resistance and sealing properties, enabling it to withstand the erosion of hazardous gases and extending the service life of the gas sample cell 1.

[0055] Furthermore, the diameter of the cavity is 3.5–4 cm, and the length of the cavity is 5–6 cm;

[0056] The thickness of the polyethylene window pane 111 is 0.15–0.2 mm;

[0057] The length of polyethylene pipe 121 is 3 to 3.5 cm, and the diameter of polyethylene pipe 121 is 0.4 to 0.6 cm;

[0058] The distance between the polyethylene pipe 121 and its nearest polyethylene window 111 is 0.4 to 0.6 cm.

[0059] In this embodiment of the invention, the gas sample storage cell 11 is 5.5 cm long and 3.7 cm in diameter; the polyethylene window 111 is 0.2 mm thick; and the polyethylene tube 121 is 3 cm long and 0.5 cm in diameter. The entire gas sample cell 1 is 10 cm high, 20 cm long, and 5 cm wide, making it suitable for miniaturized terahertz optical paths.

[0060] The inlet assembly 12 includes an inlet polyethylene pipe and an inlet polyethylene piston, and the outlet assembly 13 includes an outlet polyethylene pipe and an outlet polyethylene piston. Both the inlet assembly 12 and the outlet assembly 13 are located at the top of the gas sample storage pool 11. The inlet polyethylene pipe and the outlet polyethylene pipe are respectively located 0.5 cm in front and 0.5 cm behind the end of the gas sample storage pool 11, and are used to inject and recover the gas to be tested, respectively.

[0061] The bracket 15 is positioned 2 mm to the left of the gas sample storage cell 11. One end is connected to the connecting assembly 14 or the gas sample storage cell 11 by a screw, and the other end is connected to the terahertz time-domain spectrometer. It is used to fix the gas sample cell 1 in the terahertz optical path of the terahertz time-domain spectrometer.

[0062] In the gas sample cell provided in this embodiment of the present invention, the gas sample storage cell 11 for storing the gas to be tested is mainly made of polyethylene material. This material not only has good chemical stability, but also has extremely low production cost, making the production and popularization of the gas sample cell 1 very economical.

[0063] The gas sample storage cell 11, made of polyethylene material, can also ensure no significant absorption in the terahertz band, making it suitable for application scenarios that use terahertz technology to detect the gas to be tested.

[0064] The polyethylene window 111 used not only has no significant absorption in the terahertz band, but also has high transmittance and low cost.

[0065] The gas sample cell of this invention consists of a gas sample storage cell 11, an inlet component 12, an outlet component 13, a connecting component 14, and a support 15. The structure is very simple and can be designed to be very compact, making it easy to carry and install. It can be flexibly applied to different types of terahertz time-domain spectroscopy systems to meet diverse experimental needs.

[0066] like Figure 5 As shown, this embodiment of the present invention also provides a terahertz time-domain spectroscopy detection system, including a femtosecond laser 21, a beam splitter 22, a first delay mirror unit 23, a gallium arsenide crystal 24, a parabolic mirror 25, a second delay mirror unit 26, a polarizing mirror 27, a zinc telluride crystal 28, a polarizing beam splitter prism 29, a differential detector 210, a lock-in amplifier 211, a computer 212, and a gas sample cell 1 of any one of the above; the gas sample cell 1 is filled with the gas to be measured.

[0067] The femtosecond laser 21 is used to emit detection laser;

[0068] Beam splitter 22 is disposed in the optical path of the detection laser and is used to split the detection laser into pump light and probe light that are perpendicular to each other.

[0069] In this embodiment of the invention, the beam splitter 22 includes a half-wave plate and a beam splitter mirror. The femtosecond laser 21 serves as the laser source, and the detection laser it generates passes through the half-wave plate and then through the beam splitter mirror, where it is split into pump light and probe light that are perpendicular to each other.

[0070] The pump light is focused onto the gallium arsenide crystal 24 by the first delay mirror unit 23, which excites a terahertz wave. The terahertz wave is focused onto the gas sample cell 1 by the parabolic reflector 25, and pump light carrying sample information is obtained.

[0071] After the probe light passes through the second delay mirror unit 26 and the polarizing mirror 27 in sequence, it converges with the pump light carrying sample information on the zinc telluride crystal 28 to form the test light;

[0072] The test light is sequentially analyzed by a polarizing beam splitter 29, a differential detector 210, and a lock-in amplifier 211 before being sent to a computer 212.

[0073] In this embodiment of the invention, the polarization properties of the probe light change under the action of the pump light carrying sample information. After passing through a quarter-wave plate and a reflecting mirror M10, the light converges onto a polarizing beam splitter prism 29 and is decomposed into two polarization components with mutually perpendicular polarization directions. The intensity difference between these two polarization components is closely related to the intensity of the pump light carrying sample information, showing a direct proportional relationship. Simultaneously, this intensity difference is measured by a differential detector 210 and then sent to a lock-in amplifier 211 for signal amplification and analysis. Finally, the analyzed terahertz pulse instantaneous electric field intensity data of the gas under test is transmitted to a computer 212, which processes the data to obtain the terahertz time-domain spectral data of the gas under test.

[0074] Furthermore, both the first time-delay mirror unit 23 and the second time-delay mirror unit 26 include a reflector and a lens.

[0075] In this embodiment, the first time delay mirror unit 23 is composed of reflectors M1 and M2, and the second time delay mirror unit 26 is composed of reflectors M3, M4, M5, M6, M7, M8, and lens P.

[0076] Furthermore, the terahertz time-domain spectroscopy detection system 2 of this utility model also includes an opaque encapsulation box, in which the beam splitter 22, the first delay mirror unit 23, the gallium arsenide crystal 24, the parabolic mirror 25, the second delay mirror unit 26, the polarizer 27, the zinc telluride crystal 28, the polarizing beam splitter prism 29, and the differential detector 210 are all sealed together.

[0077] The encapsulation box is filled with nitrogen gas, and the humidity inside the encapsulation box is less than 5%.

[0078] Specifically, because water has a strong absorption capacity for terahertz waves, the presence of water vapor in the air will affect the actual detection effect of terahertz time-domain spectroscopy. To ensure the reliability and stability of the detection results, all components in the terahertz time-domain spectroscopy detection system 2, except for the computer 212, lock-in amplifier 211, and femtosecond laser 21 (which are not easily interfered with), are encapsulated in a black enclosure. Dry nitrogen is then purged to maintain the humidity inside the enclosure below 5% during the detection process.

[0079] Maintain the temperature of the testing environment at around 20℃ to minimize the impact of external interference factors on the test results.

[0080] The terahertz time-domain spectroscopy detection system provided in this embodiment first injects the collected gas into the gas sample cell 1 before detection. Compared to directly using discrete air samples, this terahertz time-domain spectroscopy detection system can obtain more amplitude and phase information through terahertz pulses, enabling the detection of lower concentrations of hazardous gases. In other words, this solution uses an air collection device to collect gases from the environment into the gas sample cell 1, and then uses the terahertz time-domain spectroscopy detection system 2 to perform terahertz spectroscopy detection on the collected gas to determine whether there are excessive levels of hazardous gases in the environment and to determine the content of various gases in the environment.

[0081] This utility model's terahertz time-domain spectroscopy detection system uses femtosecond lasers and photoconductive antennas to detect hazardous gases. Compared with conventional gas detection technologies and absorption spectroscopy detection technologies, this solution has significant advantages. Furthermore, the terahertz pulse width is on the picosecond scale, providing high time resolution, and coherent measurements can simultaneously obtain amplitude and phase information.

[0082] The terahertz time-domain spectroscopy detection system of this invention can also create a vacuum environment by introducing nitrogen gas, and extract reliable spectral features to establish a reliable database that fully considers environmental factors such as temperature, humidity, and light.

[0083] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any changes or substitutions within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A gas sample cell, characterized in that, It includes a gas sample storage tank, an inlet assembly, an outlet assembly, a connecting assembly, and a support frame; The gas sample storage cell is a cylindrical sealed cavity made of polyethylene material, and polyethylene windows are provided at both ends of the cavity. The air inlet assembly and the air outlet assembly are sequentially arranged on the side wall of the cavity along the length of the cavity, and are used to control the injection and recovery of the gas to be tested, respectively. The connecting assembly includes two fixing plates arranged sequentially along the length of the cavity, as well as a plurality of connecting screws and connecting nuts; the polyethylene window sheet corresponds one-to-one with the fixing plate, and the polyethylene window sheet is sealed and embedded on the fixing plate; the plurality of connecting screws pass through the two fixing plates in parallel, and the connecting nuts are threaded to the ends of the connecting screws; The bracket is connected to the connecting assembly and is used to fix the gas sample cell in the terahertz optical path of the terahertz time-domain spectrometer.

2. The gas sample cell according to claim 1, characterized in that, There are three connecting screws, and the three connecting screws are evenly distributed around the outer periphery of the polyethylene window.

3. The gas sample cell according to claim 1, characterized in that, Both the air intake assembly and the air outlet assembly include a polyethylene pipe and a polyethylene piston. The polyethylene pipe is connected to the side wall of the cavity, and the polyethylene piston passes through the polyethylene pipe. The polyethylene piston is provided with an air hole. Rotating the polyethylene piston can realize the connection and disconnection of the air hole and the polyethylene pipe.

4. The gas sample cell according to claim 3, characterized in that, The polyethylene pipe has a length of 3 to 3.5 cm and a diameter of 0.4 to 0.6 cm.

5. The gas sample cell according to claim 3, characterized in that, The distance between the polyethylene pipe and the nearest polyethylene window is 0.4 to 0.6 cm.

6. The gas sample cell according to claim 1, characterized in that, The diameter of the cavity is 3.5 to 4 cm, and the length of the cavity is 5 to 6 cm.

7. The gas sample cell according to claim 1, characterized in that, The thickness of the polyethylene window sheet is 0.15 to 0.2 mm.

8. A terahertz time-domain spectroscopy detection system, characterized in that, The system includes a femtosecond laser, a beam splitter, a first delay mirror unit, a gallium arsenide crystal, a parabolic mirror, a second delay mirror unit, a polarizing mirror, a zinc telluride crystal, a polarizing beam splitter, a differential detector, a lock-in amplifier, a computer, and a gas sample cell according to any one of claims 1 to 7; the gas sample cell is filled with the gas to be tested. The femtosecond laser is used to emit detection laser; The beam splitter is disposed in the optical path of the detection laser and is used to split the detection laser into pump light and probe light that are perpendicular to each other. The pump light is focused onto the gallium arsenide crystal by the first delay mirror unit, exciting a terahertz wave. The terahertz wave is focused onto the gas sample cell by the parabolic reflector, resulting in pump light carrying sample information. The probe light passes sequentially through the second delay mirror unit and the polarizing mirror, and then converges with the pump light carrying sample information onto the zinc telluride crystal to form the test light; The test light is sequentially analyzed by the polarization beam splitter, differential detector, and lock-in amplifier before being sent to the computer.

9. The terahertz time-domain spectroscopy detection system according to claim 8, characterized in that, Both the first delay mirror unit and the second delay mirror unit include a reflector and a lens.

10. The terahertz time-domain spectroscopy detection system according to claim 8, characterized in that, It also includes an opaque encapsulation box, in which the beam splitter, the first delay mirror unit, the gallium arsenide crystal, the parabolic mirror, the second delay mirror unit, the polarizing mirror, the zinc telluride crystal, the polarizing beam splitter prism, and the differential detector are all sealed together. The encapsulation box is filled with nitrogen gas, and the humidity inside the encapsulation box is less than 5%.

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