A gas concentration sensor and a gas concentration detection device

Abstract

The application is suitable for the technical field of gas measuring sensor device, and provides a gas concentration sensor and a gas concentration detection device.The gas concentration sensor comprises an incident waveguide and a reflection element, the incident waveguide and the reflection element are connected to form a fiber-optic pporre interferometer, and the gap between the two opposite end faces of the incident waveguide and the reflection element is not higher than 500 mu m.After the to-be-measured gas is filled into the fiber-optic pporre interferometer, the probe light and the pump light are input into the fiber-optic pporre interferometer, the wavelength of the pump light is scanned through the absorption line of the to-be-measured gas, the photo-thermal phase modulation is generated, the phase information of the probe light is demodulated, and the concentration of the to-be-measured gas is obtained.The sensor has the advantages of small volume, simple structure, good stability, fast gas detection response speed, and can realize the detection lower limit of the gas concentration in the order of 10 billionth.

Description

Technical Field

[0001] The present invention relates to the technical field of gas measurement sensor devices, and in particular to a gas concentration sensor and a gas concentration detection device. Background Art

[0002] High-precision gas detection plays a vital role in many fields, including disease diagnosis, environmental pollutant monitoring, and industrial gas leak alarms. High-precision gas detection technologies based on gas absorption spectroscopy determine the concentration of the gas by detecting changes in the properties of the transmitted laser light after it passes through the gas through the laser's absorption line. Tunable diode laser absorption spectroscopy (TDLAS) measures gas concentration based on the intensity of incident light, but suffers from high background noise levels and low gas detection sensitivity. Gas detection technologies based on the laser photothermal effect, on the other hand, achieve high-sensitivity gas concentration detection by simultaneously transmitting probe light of a different wavelength through the gas through the gas's absorption line while simultaneously interacting with the pump light. Early photothermal interferometry methods were performed in free-space optical systems, which were large and complex. Their gas detection sensitivity was limited by inefficient photothermal phase shifts and high low-frequency noise. In recent years, with the advancement of fiber optic technology, gas detection based on fiber optic sensing systems has been widely researched. Among these, gas detection technologies based on micro- and nanostructured optical fibers fill the optical fiber with the gas to be detected and then introduce pump and probe light to achieve high-sensitivity gas detection. However, the high sensitivity of this type of method requires a sufficiently long optical fiber, ranging from a few centimeters to several meters, to achieve a high cumulative photothermal phase. However, this long distance increases the response time of the system. At the same time, the stability of long-distance optical fibers is poor, and a servo control system is required to stabilize the working point of the photothermal interferometry during use. The large probe size, long response time, and poor stability limit the application of this type of photothermal interferometry technology in specific scenarios. Therefore, there is an urgent need for a gas concentration sensor and gas concentration detection device that can achieve high-precision gas detection while having a short response time, a small probe size, and good stability, which can be used for real-time trace gas detection and small space detection. Summary of the Invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a gas concentration sensor, aiming to solve the technical problems of large probe volume, long response time and poor stability in traditional high-precision gas detection.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0005] A gas concentration sensor comprises an incident waveguide and a reflective element. The end face of the incident waveguide and the end face of the reflective element are arranged opposite to each other to form an optical fiber Fabry-Perot interferometer. The gap between the end faces of the incident waveguide and the reflective element is no greater than 500 μm.

[0006] The pump light within the incident waveguide is emitted from the end face of the incident waveguide and generates photothermal phase modulation with the gas to be measured within the gap. Optionally, the detection light within the incident waveguide is emitted from the end face of the incident waveguide, undergoes multiple reflections within the gap, and is transmitted back to the incident waveguide multiple times, so that the concentration of the gas to be measured can be determined based on the phase information of the transmitted detection light.

[0007] After the gas to be measured fills the gap of a fiber-optic Fabry-Perot interferometer (i.e., a microcavity or fiber resonant cavity), probe light and pump light are input into the interferometer. The wavelength of the pump light is scanned across the absorption lines of the gas to be measured, generating photothermal phase modulation. By demodulating the phase information of the probe light, the concentration of the gas to be measured is obtained. The end-face gaps of existing technologies range from several centimeters to several meters, which is not conducive to improving the photothermal efficiency of the interaction between the pump light and the gas. The present invention forms a fiber-optic Fabry-Perot interferometer and reduces the end-face gap to less than 500μm, effectively improving the photothermal efficiency and thus the detection accuracy, while also reducing the size of the sensor.

[0008] Optionally, the input waveguide is a single-mode fiber. By using a single-mode fiber, mode interference can be reduced and detection accuracy can be improved. At the same time, single-mode fiber is easy to obtain and inexpensive. The input waveguide can also be a photonic crystal fiber or an optical waveguide.

[0009] Optionally, the reflective element is an object with a certain reflectivity at its end face, the reflectivity being between 1-100%, and reflects a portion of the detection light to the incident waveguide, thereby forming interference with the detection light reflected by the end face of the incident waveguide.

[0010] Optionally, when the detection light emitted through the end face of the incident waveguide hits the end face of the reflective element, a portion of the detection light is reflected to the end face of the incident waveguide. The detection light reaching the end face of the incident waveguide will reflect a portion of the detection light and transmit another portion of the detection light. After multiple reflections and multiple transmissions, interference can be formed because the distance between the detection light transmitted each time and the detection light transmitted previously is constant.

[0011] Optionally, the reflectivity of the incident waveguide end face is between 1% and 100%, and matches the reflectivity of the end face of the reflective element, which can improve the contrast of the optical fiber Fabry-Perot interferometer and enhance detection accuracy.

[0012] Optionally, the incident waveguide end face is covered with a first metamaterial to adjust the beam collimation of the outgoing light, thereby enhancing the photothermal effect and improving the detection accuracy; or the outgoing light is adjusted to a Bessel beam, thereby enhancing the photothermal effect and improving the detection accuracy.

[0013] Optionally, the end face of the reflective element is covered with a second metamaterial to adjust the beam collimation of the reflected light, thereby improving the contrast of the fiber Fabry-Perot interferometer and improving the detection accuracy.

[0014] Furthermore, the incident waveguide and the reflective element are mechanically connected or welded, or the fiber Fabry-Perot interferometer is formed by machining microgrooves on a transmission optical fiber or an optical waveguide; the mechanical connection includes at least one of a sleeve, a capillary, a mechanical connector, and bonding; the welding includes at least one of laser welding and arc welding; the microgroove machining includes at least one of ultraviolet laser machining, femtosecond laser machining, infrared laser machining, ion beam etching, electron beam etching, and 3D printing.

[0015] The incident waveguide and the reflective element are connected by a sleeve connection, which has air holes or air gaps. This sleeve connection allows for better alignment of the end faces of the incident waveguide and the reflective element, improving the contrast of the fiber Fabry-Perot interferometer and enhancing detection accuracy. The air holes and air gaps also allow for the entry of the gas to be measured.

[0016] Furthermore, the gap between the end face of the incident waveguide and the end face of the reflective element is 90 to 200 μm. By further limiting the gap to this range, high photothermal efficiency and high contrast of the fiber Fabry-Perot interferometer can be maintained simultaneously, thereby improving detection accuracy.

[0017] In order to achieve the above-mentioned purpose of the invention, the present invention also provides a gas concentration detection device, including the gas concentration sensor as described above, a pump light source for generating pump light, a detection light source for generating detection light, a photodetector and a signal detection component for demodulating the output of the fiber Fabry-Perot interferometer, the pump light source and the detection light source are both connected to the input end of the incident waveguide, the photodetector receives the detection light interference signal returned from the fiber Fabry-Perot interferometer, the output end of the photodetector is connected to the input end of the signal detection component, and the signal detection component demodulates the phase information of the returned detection light to obtain the concentration of the gas to be measured.

[0018] Further, the gas concentration detection device further comprises a wavelength division multiplexer; the pump light source comprises a pump light laser, an optical power amplifier and a modulation assembly for modulating the pump light; an output end of the modulation assembly is connected with a modulation input end of the pump light laser; an output end of the pump light laser is connected with an input end of the optical power amplifier; an output end of the optical power amplifier is connected with one end of the wavelength division multiplexer; and the other end of the wavelength division multiplexer is connected with an input end of the incident waveguide; and the wavelength division multiplexer is used for beam combination of the pump light and the probe light, and the light-thermal effect can be enhanced by increasing the pump light power, so that the detection precision is improved.

[0019] Optionally, the gas concentration detection device further comprises an optical circulator; and the optical circulator inputs the reflected probe light into the photodetector; a 1 port of the optical circulator is connected with an output end of the probe light source; a 2 port of the optical circulator is connected with one end of the wavelength division multiplexer; and a 3 port of the optical circulator is connected with the photodetector.

[0020] The gas concentration sensor has the advantages that: the effective light-thermal length of the sensing probe is within 500 microns, the light-thermal efficiency is high, the sensor has a small volume and a simple structure, and can be used for small space detection; the response time of the sensor is low, the gas detection response speed is fast, and the sensor can be used for real-time detection; the gas concentration detection lower limit of the sensor can reach the order of magnitude of 10 billionth, the dynamic range is as high as 10 to the power of 7, and the detection linearity covers 100%; the sensor can be transmitted by an optical fiber, can be used for remote gas detection, is resistant to electromagnetic interference, and can be used for gas detection in extreme environments. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0022] Figure 1 is a schematic diagram of a gas concentration sensor according to an embodiment of the present application;

[0023] Figure 2 is a schematic diagram of a gas concentration sensor package according to an embodiment of the present application;

[0024] Figure 3 is a gas filling schematic diagram of a gas concentration sensor according to an embodiment of the present application;

[0025] Figure 4 is a schematic diagram of a gas concentration detection device according to an embodiment of the present application;

[0026] Figure 5 is a graph showing gas concentration detection results of a gas concentration detection device according to an embodiment of the present invention;

[0027] Figure 6 is a graph of gas detection response time of a gas concentration detection device according to an embodiment of the present invention;

[0028] Figure 7 FIG. 4 is a schematic diagram of the principle of a gas concentration sensor according to another embodiment of the present invention.

[0029] The reference numerals used in the above drawings are as follows:

[0030] 1-gas concentration sensor; 10-incident waveguide; 12-reflection element; 101-end face of incident waveguide; 121-end face of reflective element; 20-gas to be measured; 64-casing; 641-casing opening; 801-pump light source; 803-detection light source; 804-fiber circulator; 805-wavelength division multiplexer; 806-photodetector; 807-signal detection component. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0032] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly or indirectly located on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The directions or positions indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are only for the convenience of description and cannot be understood as limitations on this technical solution. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0033] In order to illustrate the technical solution described in this application, the following is a detailed description with reference to specific drawings and embodiments.

[0034] See also Figure 1 、 Figure 3 and Figure 7An embodiment of the present invention provides a gas concentration sensor 1, comprising an incident waveguide 10 and a reflective element 12, wherein an end face 101 of the incident waveguide 10 and an end face 121 of the reflective element 12 are arranged relative to each other to form a fiber Fabry-Perot interferometer, and a gap between the end face 101 of the incident waveguide 10 and the end face 121 of the reflective element 12 is not greater than 500 μm.

[0035] The pump light within the incident waveguide 10 is emitted from the end face 101 of the incident waveguide 10 and generates photothermal phase modulation with the gas to be measured 20 within the gap. Optionally, the detection light within the incident waveguide 10 is emitted from the end face 101 of the incident waveguide 10, reflected within the gap, and transmitted back into the incident waveguide 10, so that the concentration of the gas to be measured 20 can be determined based on the phase information of the transmitted detection light. It will be understood that the detection light within the gap can return to the incident waveguide 10 after a single reflection and a single transmission. Of course, after multiple reflections and multiple projections, multiple beams of detection light will return to the incident waveguide 10.

[0036] The end face 101 of the incident waveguide 10 is the output end of the incident waveguide 10. The pump light and the probe light propagating in the incident waveguide 10 are both emitted from the end face 101 of the incident waveguide 10. After the pump light enters the gap, part of the light energy is absorbed by the gas to be measured 20 and transitions from a low-energy state to an excited state. The excited gas to be measured 20 releases the absorbed energy in a non-radiative relaxation manner and converts all or part of it into thermal energy, resulting in changes in the temperature in the gap and changes in the density and pressure of the gas to be measured 20, and finally causing changes in the refractive index, thereby resulting in photothermal phase modulation of the probe light.

[0037] Optionally, the end face 101 of the incident waveguide 10 and the end face 121 of the reflective element 12 are parallel to each other. After the detection light enters the gap, it will be continuously reflected between the end face 101 of the incident waveguide 10 and the end face 121 of the reflective element 12. Part of the detection light is transmitted back to the incident waveguide 10 from the end face 101 of the incident waveguide 10. Due to the photothermal phase modulation caused by the change in refractive index, the phase of the transmitted detection light will change. The concentration of the gas 20 to be measured can be obtained through the phase information.

[0038] The gas concentration sensor 1 can detect any type of gas, including but not limited to acetylene, hydrogen, oxygen, and methane. After the gas 20 to be measured is filled into the gap of the fiber-optic Fabry-Perot interferometer, probe light and pump light are input into the input waveguide 10 of the fiber-optic Fabry-Perot interferometer. The wavelength of the pump light is scanned across the absorption line of the gas 20 to be measured, generating photothermal phase modulation. By demodulating the phase information of the probe light, the concentration of the gas 20 to be measured is obtained.

[0039] For example, when detecting acetylene, the wavelength of the pump light is scanned through the P(9) absorption line of acetylene near 1530.37 nm, generating photothermal phase modulation. The phase change after the probe light passes through is detected, and the acetylene concentration is demodulated. The probe light wavelength is any wavelength that is not on the gas absorption line.

[0040] Preferably, the gap between the end face 101 of the incident waveguide 10 and the end face 121 of the reflective element 12 is 90-200 μm. By further limiting the gap to this range, high photothermal phase modulation and high contrast of the fiber Fabry-Perot interferometer can be maintained simultaneously, thereby improving detection accuracy.

[0041] Optionally, the input waveguide 10 is a single-mode fiber. By using a single-mode fiber, mode interference can be reduced and detection accuracy can be improved. At the same time, single-mode fiber is easy to obtain and inexpensive. The input waveguide 10 can also be a photonic crystal fiber or an optical waveguide.

[0042] Optionally, the reflective element 12 is an object with a certain reflectivity at its end face, which is between 1-100%. It reflects a portion of the detection light into the incident waveguide, thereby interfering with the detection light reflected by the end face of the incident waveguide.

[0043] Optionally, when the detection light emitted through the end face 101 of the incident waveguide 10 is irradiated on the end face 121 of the reflecting element 12, a part of the detection light is reflected to the end face 101 of the incident waveguide 10. The detection light reaching the end face 101 of the incident waveguide 10 will reflect a part of the detection light and transmit another part of the detection light. After multiple reflections and multiple transmissions, interference can be formed because the distance between the detection light transmitted each time and the detection light transmitted previously is constant.

[0044] Preferably, the reflective element 12 has a reflectivity of more than 50% at the detection light wavelength and the pump light wavelength. The increase in the light intensity of the reflected detection light wavelength can improve the high contrast of the fiber Fabry-Perot interferometer, and the high reflection of the pump light can improve the photothermal effect, thereby improving the detection accuracy.

[0045] Optionally, the reflective element 12 has a reflectivity of more than 90% at the detection light wavelength, and the detection light wavelength corresponds to the resonance wavelength of the fiber resonant cavity of the fiber Fabry-Perot interferometer, thereby improving detection accuracy through the resonance of the fiber Fabry-Perot interferometer.

[0046] Optionally, the reflectivity of the end face 101 of the incident waveguide 10 is in the range of 1-100%, and matches the reflectivity of the end face 121 of the reflective element 12, which can improve the contrast of the fiber Fabry-Perot interferometer and enhance detection accuracy.

[0047] Optionally, the end face 101 of the incident waveguide 10 is covered with a first metamaterial, which regulates the beam collimation of the outgoing light, enhances the photothermal effect, and improves the detection accuracy; or regulates the outgoing light into a Bessel beam, which enhances the photothermal effect and improves the detection accuracy. The metamaterial can be a planar or three-dimensional structure composed of sub-micron-sized units arranged in a certain pattern, which regulates the phase of the incident light in space to improve the beam collimation of the incident light or regulate it into a Bessel beam. The shape and size of the sub-micron-sized units can be set as needed.

[0048] Optionally, the end face 121 of the reflecting element 12 is covered with a second metamaterial, which regulates the beam collimation of the reflected light, improves the contrast of the fiber-optic Fabry-Perot interferometer, and improves the detection accuracy.

[0049] Further, the incident waveguide 10 and the reflecting element 12 are connected by mechanical connection or welding, or the fiber-optic Fabry-Perot interferometer is formed by machining micro-slots on the transmission fiber or optical waveguide; the mechanical connection includes at least one of the following: using a sleeve 64, a capillary tube, a mechanical connector, and adhesion; the welding includes at least one of the following: laser welding and electric arc welding; the micro-slot machining includes at least one of the following: ultraviolet laser machining, femtosecond laser machining, infrared laser machining, ion beam etching, electron beam etching, and 3D printing.

[0050] Please refer to Figure 2 , a packaging schematic diagram of a gas concentration sensor 1 according to an embodiment of the present application, the incident waveguide 10 and the reflecting element 12 are connected by a sleeve 64, and the sleeve 64 has a sleeve opening 641. Optionally, the sleeve opening 641 is a gas hole or a gas slit.

[0051] Please refer to Figure 3 , a gas filling schematic diagram of a gas concentration sensor 1 according to an embodiment of the present application, the test gas 20 enters the cavity between the incident waveguide 10 and the reflecting element 12 through the sleeve opening 641.

[0052] Based on the gas concentration sensor according to any one of the above embodiments, the present application further provides a gas concentration detection method. The gas concentration detection method comprises:

[0053] S100, filling the test gas into the gap of the fiber-optic Fabry-Perot interferometer.

[0054] S200, inputting the probe light and the pump light into the incident waveguide of the fiber-optic Fabry-Perot interferometer, scanning the wavelength of the pump light through the absorption line of the test gas to generate photothermal phase modulation.

[0055] S300, obtaining the concentration of the test gas by demodulating the phase information of the transmitted probe light.

[0056] Specifically, after the gas to be measured is filled into the gap, the probe light in the incident waveguide undergoes multiple reflections and transmissions through the gap before returning to the incident waveguide, allowing the original phase information of the probe light to be obtained. Optionally, multiple reflections of the pump light within the gap improve the utilization of the pump light, enhance the efficiency of photothermal phase modulation, and improve detection accuracy.

[0057] By scanning the wavelength of the pump light, we can find a wavelength sufficient to induce photothermal phase modulation in the probe light. Specifically, when the gas under test absorbs pump light of this wavelength, it absorbs some of the pump light's energy, causing a change in the gas's refractive index, resulting in photothermal phase modulation. The concentration of the gas under test can be determined by combining the phase information of the probe light with the original phase information. The greater the concentration of the gas under test, the more light energy is absorbed, the greater the change in refractive index, and the greater the change in phase information. By establishing a relationship between the concentration of the gas under test and its phase information, the concentration of the gas under test can be detected.

[0058] Please refer to Figure 4 One embodiment of the present invention further provides a gas concentration detection device, comprising: the gas concentration sensor 1 described in any of the above embodiments, a pump light source 801, a probe light source 803, a photodetector 806, and a signal detection component 807. The pump light source 801 provides pump light, and the probe light source 803 provides probe light. Both the pump light source 801 and the probe light source 803 are connected to the input end of the incident waveguide. The photodetector 806 receives the probe light interference signal returned from the fiber Fabry-Perot interferometer. The output end of the photodetector 806 is connected to the input end of the signal detection component 807. The signal detection component demodulates the phase information of the returned probe light to obtain the concentration of the gas 20 to be measured.

[0059] The gas concentration detection device further includes: an optical fiber circulator 804 and a wavelength division multiplexer 805 .

[0060] The probe light source 803 provides probe light, which enters the fiber circulator 804. The probe light from the fiber circulator 804 and the pump light from the pump light source 801 enter the wavelength division multiplexer 805. The laser light, after being recombined by the wavelength division multiplexer 805, enters the input end of the incident waveguide of the gas concentration sensor 1. The pump light generates photothermal phase modulation with the gas 20 to be measured within the gas concentration sensor 1. The probe light passes through the fiber Fabry-Perot interferometer of the gas concentration sensor 1, where it interferes with the probe light reflected from the end face 101 of the incident waveguide 10 and the end face 121 of the reflective element 12. The probe light then passes through the wavelength division multiplexer 805 and the fiber circulator 804 and enters the photodetector 806. The photodetector 806 inputs an electrical signal into the signal detection component 807, which demodulates the phase of the probe light to obtain concentration information of the gas 20 to be measured. Furthermore, the signal detection component 807 demodulates the first harmonic signal or the second harmonic signal to obtain concentration information of the gas 20 to be measured. In another embodiment of the present invention, a wavelength stabilization device is used during the detection process to stabilize wavelength variations and improve detection accuracy. Optionally, the pump light and probe light are pulsed light or continuous light.

[0061] The signal detection component 807 inputs an electrical modulation signal to the pump light source 801. The signal detection component 807 may be a lock-in amplifier. The electrical modulation signal of the signal detection component 807 may change the wavelength of the pump light of the pump light source 801.

[0062] Figure 5 A graph showing the gas concentration detection results of the above embodiment is provided. The linear fitting of the experimental results shows that the detection linearity covers up to 100%. Compared with the noise level, the dynamic range is as high as 10 to the seventh power, which can reach the lower limit of gas concentration detection of one billionth of the order of one billionth.

[0063] Figure 6 The graph showing the gas detection response time of the gas concentration detection device of the above embodiment shows that the time required to reach 90% of the concentration of the gas to be measured is 1 second. The response time is very short and can be used for real-time detection of trace gas concentration.

[0064] Based on the gas concentration detection device of any of the above embodiments, the present invention further provides a method for controlling the gas concentration detection device, comprising:

[0065] A100. When the gas to be measured is filled into the gap of the fiber Fabry-Perot interferometer, the detection light source and the pump light source are controlled to input the detection light and the pump light into the incident waveguide of the fiber Fabry-Perot interferometer, and the wavelength of the pump light is scanned to pass through the absorption line of the gas to be measured, thereby generating photothermal phase modulation.

[0066] A200, detecting the transmitted probe light by the photoelectric detector, and demodulating the phase information of the transmitted probe light by the signal detection component to obtain the concentration of the to-be-detected gas.

[0067] Optionally, when the to-be-detected gas fills into the gap of the fiber-optic Fabry-Perot interferometer, the probe light source can be controlled to provide the probe light and enter into the gap. After multiple reflections and multiple transmissions in the gap, the probe light returns to the incident waveguide, and the original phase information of the probe light can be obtained. Then, the wavelength of the pump light is scanned to pass through the absorption line of the to-be-detected gas to generate photothermal phase modulation, and the phase information of the probe light, i.e., the phase information of the probe light after photothermal phase modulation, is obtained. The transmitted probe light is collected by the photoelectric detector, and the phase information of the transmitted probe light is demodulated to obtain the concentration of the to-be-detected gas.

[0068] Specifically, the step A100 comprises:

[0069] The wavelength of the pump light is scanned to pass through the absorption line of the to-be-detected gas by the signal detection component to generate photothermal phase modulation.

[0070] Specifically, the signal detection component can determine whether the transmitted probe light has photothermal phase modulation, so as to change the wavelength of the pump light.

[0071] The above only describes optional embodiments of the present application and does not limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A gas concentration sensor, characterized in that: include: An incident waveguide and a reflective element, wherein the end face of the incident waveguide and the end face of the reflective element are arranged relative to each other to form a fiber Fabry-Perot interferometer, and the gap between the end face of the incident waveguide and the end face of the reflective element is no greater than 500 μm; a gas to be measured exists in the gap, and after the pump light enters the gap, part of the light energy is absorbed by the gas to be measured and transitions from a low-energy state to an excited state. The excited gas to be measured releases the absorbed energy by non-radiative relaxation and converts it into heat energy, resulting in changes in the temperature in the gap and changes in the density and pressure of the gas to be measured, and finally causing a change in the refractive index, thereby causing photothermal phase modulation of the probe light; the end face of the incident waveguide and the end face of the reflective element are parallel to each other, the pump light and the probe light are reflected and transmitted multiple times between the end face of the incident waveguide and the end face of the reflective element, the distance between the transmitted probe light and the previously transmitted probe light is constant, and interference is formed.

2. The gas concentration sensor according to claim 1, wherein The incident waveguide is one of a single-mode optical fiber, a photonic crystal optical fiber, and an optical waveguide.

3. The gas concentration sensor according to claim 1, wherein The reflectivity of the end face of the incident waveguide matches the reflectivity of the end face of the reflective element.

4. The gas concentration sensor according to claim 1, wherein The end face of the incident waveguide is covered with a first metamaterial, and the first metamaterial is used to adjust the beam collimation of the detection light emitted from the end face of the incident waveguide and / or adjust the detection light emitted from the end face of the incident waveguide to a Bessel beam; and / or The end face of the reflective element is covered with a second metamaterial, and the first metamaterial is used to adjust the beam collimation of the detection light reflected by the end face of the reflective element.

5. The gas concentration sensor according to claim 1, wherein The incident waveguide and the reflective element are mechanically connected or welded, or the fiber Fabry-Perot interferometer is formed by machining microgrooves on a transmission optical fiber or an optical waveguide; the mechanical connection includes at least one of a sleeve, a capillary, a mechanical connector, and bonding; the welding includes at least one of laser welding and arc welding; the microgroove machining includes at least one of ultraviolet laser machining, femtosecond laser machining, infrared laser machining, ion beam etching, electron beam etching, and 3D printing.

6. The gas concentration sensor according to claim 1, wherein The gap between the end face of the incident waveguide and the end face of the reflective element is 90-200 μm.

7. A gas concentration detection method, characterized in that: Using the gas concentration sensor according to any one of claims 1 to 6, the gas concentration detection method includes: The gas to be measured is filled into the gap of the fiber Fabry-Perot interferometer; The probe light and pump light are input into the incident waveguide of the fiber Fabry-Perot interferometer, and the wavelength of the pump light is scanned to pass through the absorption line of the gas to be measured, generating photothermal phase modulation; The concentration of the gas to be measured is obtained by demodulating the phase information of the transmitted detection light.

8. A gas concentration detection device, characterized in that: include: The gas concentration sensor according to any one of claims 1 to 6, a pump light source for generating pump light, a detection light source for generating detection light, a photodetector, and a signal detection component for demodulating the output of the fiber Fabry-Perot interferometer; The pump light source and the detection light source are both connected to the input end of the incident waveguide, the photodetector receives the detection light interference signal returned from the fiber Fabry-Perot interferometer, the output end of the photodetector is connected to the input end of the signal detection component, and the signal detection component demodulates the phase information of the returned detection light to obtain the concentration of the gas to be measured.

9. The gas concentration detection device according to claim 8, characterized in that: The gas concentration detection device further includes: a wavelength division multiplexer and an optical circulator; The pump light source includes: a pump light laser, an optical power amplifier and a modulation component for modulating the pump light; The output end of the modulation component is connected to the modulation input end of the pump light laser, the output end of the pump light laser is connected to the input end of the optical power amplifier, the output end of the optical power amplifier is connected to one end of the wavelength division multiplexer, and the other end of the wavelength division multiplexer is connected to the input end of the incident waveguide; port 1 of the optical circulator is connected to the output end of the detection light source; port 2 of the optical circulator is connected to one end of the wavelength division multiplexer; and port 3 of the optical circulator is connected to the photodetector.

10. A method for controlling a gas concentration detection device, characterized in that: Using the gas concentration detection device according to any one of claims 8 to 9, the control method includes: When the gas to be measured is filled into the gap of the fiber Fabry-Perot interferometer, the detection light source and the pump light source are controlled to input the detection light and the pump light into the incident waveguide of the fiber Fabry-Perot interferometer, and the wavelength of the pump light is scanned to pass through the absorption line of the gas to be measured, thereby generating photothermal phase modulation; The transmitted detection light is detected by a photodetector, and the phase information of the transmitted detection light is demodulated by a signal detection component to obtain the concentration of the gas to be measured.

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