Anti-resonance hollow waveguide photo-thermal spectrum gas sensor

Abstract

The invention discloses an anti-resonance hollow-core waveguide photo-thermal spectrum gas sensor, and relates to an optical gas sensor. The laser comprises pump laser (1), detection laser (2), an input optical fiber (3), a hollow-core anti-resonance optical fiber (4), an output optical fiber (5) and a photoelectric detector (6), the pump laser (1) and the detection laser (2) are combined through a coupler and are coupled to an air core of the hollow-core anti-resonance optical fiber (4) through the input optical fiber (3); the input optical fiber (3), the hollow-core anti-resonance optical fiber (4), the output optical fiber (5) and the photoelectric detector (6) are connected in sequence; and the hollow-core anti-resonance optical fiber (4) comprises a waveguide gas chamber (4-0), a gas inlet (4-1) and a gas outlet (4-2). The optical phase demodulation is realized by utilizing an anti-resonance reflected light waveguide mechanism, an external interference phase demodulation structure is not needed, the system is simple, the cost is low, and the response speed is high.

Description

Technical Field

[0001] The invention relates to an optical gas sensor, in particular to an anti-resonance hollow core waveguide photothermal spectrum gas sensor. Background Art

[0002] Among various gas detection technologies, optical gas sensing technology is favored for its advantages such as high sensitivity, fast response and non-invasive detection. Optical gas sensing technology has broad application prospects in the fields of breath diagnosis, toxic gas leakage, environmental atmosphere monitoring and energy exploration. In optical gas sensing technology, laser spectroscopy technology includes: tunable diode laser absorption spectroscopy, Raman spectroscopy and photoacoustic / photothermal spectroscopy. Different types of gases can be effectively distinguished by the absorption spectrum of the gas to be tested in the molecular fingerprint. The physical process of photothermal spectroscopy in trace gas detection can be divided into several key parts: first, the pump laser is processed by intensity modulation or wavelength modulation to interact with gas molecules, so that the gas molecules absorb the photon energy of a specific wavelength, and their electrons transition from the ground state to a high-energy excited state; then, the high-energy excited state gas molecules release energy through the process of non-radiative thermal relaxation, generating local heat accumulation in space, and then modulating the optical refractive index distribution of the space; when the continuous detection laser passes through this position, its optical phase shifts due to the refractive index modulation. Based on different optical phase demodulation methods, the phase information can be converted into intensity changes, which change with the concentration of gas molecules, and finally obtain the linear change of the detection laser intensity signal, thereby achieving the purpose of indirect sensing. Since the active detection means of pump and detection lasers are used at the same time, zero-background trace gas detection can be achieved by using photothermal phase demodulation at the same time.

[0003] According to the photothermal phase demodulation method, photothermal spectroscopy can be divided into photothermal interference spectroscopy and heterodyne photothermal spectroscopy. After the pump light excites the gas molecules to be measured in the space to produce photothermal phase changes, the photothermal interference spectroscopy mainly converts the phase change of the detection light into the interference phase difference of the detection light by constructing an optical interferometer. When the phase difference changes, the phase conversion to the intensity change at the interference working point is the most obvious, thereby converting the phase change into an intensity signal output; heterodyne photothermal spectroscopy is achieved by adjusting the wavelength of the detection laser to move it toward the wavelength of the pump light. When the distance is close enough, the two light beams will beat, causing the optical frequency to be converted to radio frequency. At the same time, the photothermal phase change information is carried in the beat signal, and signal demodulation can be achieved through electrical demodulation. According to the location where the photothermal effect occurs, it can be roughly divided into free-space photothermal spectroscopy and hollow-core fiber photothermal spectroscopy. The former directly contacts the pump laser with the gas molecules to be measured distributed in free space. The outgoing beam is generally transmitted forward in a Gaussian beam state under uncollimated conditions, and excites the gas molecules to produce photothermal effects. The latter simultaneously couples the pump and detection lasers into a hollow core waveguide, such as a photonic crystal fiber or an antiresonant reflection optical waveguide. In particular, based on the principle of antiresonant reflection optical waveguide, the pump beam is confined in the hollow core during transmission, and the interaction ratio with the trace gas molecules diffused into the hollow core is significantly improved compared to free space. Therefore, antiresonant hollow core fiber photothermal spectroscopy can achieve gas concentration detection with a lower threshold.

[0004] In the above-mentioned gas detection scheme of photothermal interference spectroscopy, the specific interference demodulation technologies currently proposed include mature interference devices such as Mach-Zehnder interferometer, Michelson interferometer, Fabry-Perot interferometer, etc., which can be used for intensity demodulation of photothermal-induced phase. Among them, Fabry-Perot interference is widely used in the development of miniaturized photothermal spectroscopy gas detectors because of its simple structure and easy integration. However, when considering the influence of temperature on the interferometer phase difference in the actual environment, the scheme based on interferometer to achieve phase demodulation often needs to introduce a mechanism of negative feedback locking of the detection wavelength to lock the static orthogonal working point to improve the output intensity signal-to-noise ratio. Usually, the principle of bevel demodulation involves the working point locking, which requires the introduction of a PID negative feedback algorithm, involving a large number of feedback, calculation and amplification circuits, and the operation is complicated and difficult to implement.

[0005] In terms of the above two points, the photothermal spectrometer required for the purpose of trace gas detection requires high-efficiency pump light transmission excitation and a stable signal demodulation unit, and at the same time, the system structure must be simple and compact, and easy to integrate and package later. Therefore, it is necessary to design an all-fiber photothermal gas absorption chamber that can simultaneously realize pump light confinement and detection light phase demodulation. Therefore, a scheme based on anti-resonant hollow-core fiber as a gas absorption chamber and using the resonant roll-off band for bevel demodulation is proposed, which can omit the design of the fiber interferometer. At the same time, the temperature-insensitive characteristics of the resonant roll-off band are used to achieve crosstalk-free photothermal phase change conversion, forming a demodulator based on the properties of the waveguide itself. Secondly, by controlling the optical waveguide structure and material properties, an ultra-wide range of anti-resonance demodulation linear regions can be achieved, which will greatly improve the demodulation range compared to ordinary fiber interferometers, thereby achieving an ultra-large dynamic measurement range within the trace concentration range. Summary of the invention

[0006] The purpose of the present invention is to solve the problems and shortcomings of the prior art and to provide an anti-resonance hollow core waveguide photothermal spectroscopy gas sensor.

[0007] The object of the present invention is achieved in that:

[0008] The gas absorption chamber of the sensor is composed of a cascade of antiresonant hollow-core fiber and single-mode fiber. The pump and detection light are coupled into the hollow-core gas chamber at the same time. The antiresonant characteristics constrain the pump light and gas molecules to stimulate the photothermal effect aggregation in the full hollow-core circuit under extremely high light energy density conditions, forming a thermal field distribution in the cavity, which will further modulate the phase of the detection light field, and in the special resonance roll-off band of the antiresonant hollow-core fiber, the phase change is linearly converted into a photothermal intensity signal output, achieving the purpose of all-fiber photothermal trace gas detection from pump enhancement and large dynamic range precision demodulation. In the future, it may serve as a new system structure to guide the design and implementation of small precision gas analyzers with integrated core components.

[0009] Specifically

[0010] like Figure 1 , the sensor includes a pump laser, a detection laser, an input optical fiber, a hollow core anti-resonance optical fiber, an output optical fiber and a photodetector;

[0011] The pump laser and the detection laser are combined by a coupler and coupled into the air core of the hollow-core anti-resonance optical fiber through an input optical fiber;

[0012] The input optical fiber, the hollow core antiresonant optical fiber, the output optical fiber and the photodetector are connected in sequence.

[0013] Working mechanism:

[0014] The pump laser and the detection laser are coupled into the input optical fiber for transmission and delivered to the hollow core anti-resonance optical fiber. The output detection light is coupled into the output optical fiber and finally projected into the photodetector to output the gas concentration signal to be measured.

[0015] The center point of the antiresonant hollow core waveguide is aligned with the center point of the single-mode optical fiber core through a ceramic ferrule and a ceramic sleeve between the input optical fiber, the hollow core antiresonant optical fiber and the output optical fiber, and a passage for gas to enter the hollow core gas chamber is formed at a distance of several microns.

[0016] The present invention has the following advantages and positive effects:

[0017] ① This sensor is based on the anti-resonant reflective optical waveguide mechanism in the anti-resonant hollow core waveguide, and proposes a new photothermal phase demodulation principle to solve the additional structure required for interferometric optical phase demodulation and reduce the complexity of the sensor;

[0018] ② Design the anti-resonant hollow core waveguide geometry and material refractive index distribution to achieve a spectral distribution with an ultra-large resonant roll-off range. Based on this transmission characteristic, an ultra-large linear bevel region can be achieved to ensure a larger measurable gas concentration range;

[0019] ③ Based on the unique hollow core inner wall of the antiresonant hollow core waveguide, its curved surface has an equivalent high-fineness distribution, corresponding to the unit phase change in the roll-off area in the spectrum, which will realize linear optical phase modulation amplification, thereby compensating for the defect of insufficient photothermal effect excitation when detecting extremely low concentration gases and ensuring the lower limit of system detection;

[0020] ④ This sensor can achieve both ultra-low detection limit and ultra-large detection dynamic range by rationally designing the optical waveguide structure and controlling the transmission characteristics of pump light and detection light in the waveguide. It will be used to guide the design of new photothermal gas sensors.

[0021] In summary, the present invention realizes optical phase demodulation by using the anti-resonance reflection optical waveguide mechanism, does not require an external interference phase demodulation structure, and has a simple system, low cost and fast response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the sensor, in which:

[0023] 1—Pump laser;

[0024] 2—Detection laser;

[0025] 3—Input optical fiber;

[0026] 4—hollow core antiresonant optical fiber, 4-0—waveguide gas chamber, 4-1—gas inlet, 4-2—gas outlet;

[0027] 5—Output optical fiber;

[0028] 6—Photodetector.

[0029] Figure 2 is a cross-sectional view of the hollow-core antiresonant fiber 4.

[0030] Figure 3 The anti-resonance transmission spectrum is produced in the waveguide gas chambers of different lengths under the stimulation of wide-spectrum light, which appears as periodically spaced anti-resonance transmission bands in the spectrum, and the two sides of the bands are resonance roll-off bands. DETAILED DESCRIPTION

[0031] The following is a detailed description with reference to the accompanying drawings and embodiments.

[0032] 1. Anti-resonant hollow core waveguide photothermal spectroscopy gas sensor

[0033] 1. Overall

[0034] like Figure 1 , the sensor includes a pump laser 1, a detection laser 2, an input optical fiber 3, a hollow core anti-resonance optical fiber 4, an output optical fiber 5 and a photodetector 6;

[0035] The pump laser 1 and the detection laser 2 are combined by a coupler and coupled into the air core of the hollow-core antiresonant optical fiber 4 via the input optical fiber 3;

[0036] The input optical fiber 3, the hollow core anti-resonance optical fiber 4, the output optical fiber 5 and the photodetector 6 are connected in sequence.

[0037] 2. Functional components

[0038] 1) Pump laser 1

[0039] The pump laser 1 is a narrow line width continuous laser beam generated by a distributed feedback laser driven by a corresponding current driver.

[0040] Generally, a distributed feedback laser corresponds to an initial central wavelength, and by controlling the input drive current, continuous tuning of the central wavelength is achieved, thereby achieving complete scanning excitation of the absorption lines of the gas molecules to be measured, and generating subsequent photothermal phase changes.

[0041] Specifically, the pump laser 1 includes a DFB semiconductor laser chip and a DFB semiconductor laser chip current driver ORLD-1500 produced by Wuhan Optics Valley Interconnect Technology Co., Ltd.; by assembling the above device and connecting a DC power adapter, the drive generates a narrow linewidth continuous laser beam with a central wavelength of 1532.83 nanometers, and at the same time, a triangular control current signal is introduced into the driving current to modulate the laser wavelength for linear tuning near the central wavelength, thereby achieving a complete scan of the absorption lines of the gas molecules to be measured.

[0042] 2) Detection laser 2

[0043] The detection laser 2 is generated by an ultra-narrow linewidth laser whose linewidth is much smaller than that of the pump laser 1. It is used to undertake the local refractive index modulation caused by the photothermal effect and form a photothermal signal containing the concentration information of the gas molecules to be measured.

[0044] In addition, the central wavelengths of the detection laser 2 and the pump laser 1 need to be separated by a certain spectral distance to avoid the detection laser 2 from interfering with the absorption of gas molecules.

[0045] Specifically, the detection laser 2 is produced by NKT Photonics E15 ultra-narrow linewidth laser to generate a continuous laser beam with a central wavelength of 1550 nanometers and a linewidth less than 100 Hz. At the same time, the output light wavelength is feedback locked to the orthogonal working point of the resonance roll-off band through the internal frequency locking device of the laser, which is used to linearly convert the detection light phase drift caused by the photothermal phase change into the output light field intensity change.

[0046] 3) Input fiber 3

[0047] The input optical fiber 1 is a general commercial near-infrared single-mode optical fiber, which is convenient for connecting the jumper at the laser output end to form a stable beam transmission medium.

[0048] The present invention uses the EasyBand series single-mode optical fiber provided by Changfei Company, which belongs to the TU-T G.657 standard optical fiber series; its fiber core is a 9.1-micron germanium-doped fiber core, and the outer cladding is a high-purity silicon dioxide layer with an outer diameter of 125 microns.

[0049] After the pump laser 1 and the detection laser 2 are generated, they are coupled into the input optical fiber 3.

[0050] At the same time, the input optical fiber 3 delivers the pump laser 1 and the detection laser 2 to the hollow-core antiresonant optical fiber 4 at the same time. At the delivery end, the ceramic ferrule and the ceramic sleeve are mechanically connected to form optical coupling, and a 1-2 micron slit is reserved in between to form a connecting gas path between the gas chamber and the external gas to be measured.

[0051] 4) Hollow core anti-resonant fiber 4

[0052] like Figure 1 , 2 ,

[0053] A. Structure

[0054] The hollow core antiresonant optical fiber 4 comprises a waveguide gas chamber 4-0, a gas inlet 4-1, and a gas outlet 4-2;

[0055] The core diameter is 32 microns, the outer cladding diameter is 125 microns, and a waveguide air chamber 4-0 with a length of 5-10 cm is formed by vertical cutting at both ends, on which a gas inlet 4-1 and a gas outlet 4-2 are arranged.

[0056] Its outer cladding is made of high-purity silica, and the refractive index of the material is 1.444 near a wavelength of 1550 nanometers.

[0057] B. Function

[0058] Light confinement in a hollow-core waveguide is achieved based on the antiresonant reflection optical waveguide effect.

[0059] The antiresonance spectrum formed based on this length has the characteristics of low loss and large contrast, and can effectively achieve high-efficiency pump light confinement and phase demodulation of the resonance roll-off band.

[0060] C. Specifically

[0061] Traditional optical fiber is made of a thin glass tube filled with optical medium. When light is transmitted through it, it will be reflected and refracted multiple times, resulting in energy loss and signal attenuation.

[0062] The hollow core anti-resonant optical fiber 4 is a new type of optical fiber, which is characterized by a hollow tube in the center of the optical fiber. This tube can prevent resonance from occurring when light is transmitted in the optical fiber, thereby improving the transmission efficiency and quality of the optical fiber.

[0063] When the pump beam 1 and the probe beam 2 are coupled through the input optical fiber 3 into the hollow core antiresonant optical fiber 4, the light field can be approximated as a Gaussian distribution. When the light of the waveguide air chamber 4-0 is transmitted to the interface between the air core and the outer cladding, the light will not be refracted and will completely leak out of the optical fiber. When the incident angle meets the grazing incidence condition, the multiple beams refracted into the outer cladding will strongly interfere with the multiple beams reflected in the air core when the phase matching condition is met, which plays a role in limiting the further leakage of the light field out of the cladding. At the same time, from the perspective of multi-beam interference combined with the optical fiber geometric parameters and refractive index distribution, it can be seen that the light field in the air core that is constrained to transmit forward will show periodic resonance. From the perspective of interference, it can be understood that the refracted light and the reflected light interfere with each other to cause the light field to leak, and the light beam that does not meet this condition will be strictly restricted to transmit in the fiber core. From the perspective of the spectrum, the two processes can be distinguished as periodically alternating resonant spectral bands and antiresonant spectral bands. Further, when the pump beam 1 excites the trace gas molecules in the air core to produce a photothermal effect, the periodic refractive index modulation in the core affects the phase change of the probe light field at that location. When the phase of the detection beam 2 changes, the wavelength of the detection beam 2 is pre-calibrated to the steep part of the roll-off region in the resonance spectrum band, that is, the orthogonal working point of the resonance roll-off band, so that the phase change of the detection beam 2 is sensitively converted into a change in the detection light intensity, thereby improving the sensitivity and detection limit of the gas sensor. In the actual sensor air chamber design, the two ends of the anti-resonance hollow-core optical fiber are vertically cut to form a fiber air chamber with a length of 5-10 cm. The anti-resonance spectrum formed based on the length has the characteristics of low loss and high contrast, which can effectively achieve high-efficiency pump light confinement and phase demodulation of the resonance roll-off band.

[0064] 5) Output fiber 5

[0065] The output optical fiber 5 is of the same type as the input optical fiber 3 and is used to transmit the detection light beam that passes through the hollow-core antiresonant optical fiber 4 and transmits out. The photothermal intensity signal carried therein is filtered and enters the photodetector 6, which is convenient for subsequent signal processing to extract the concentration information of the trace gas to be measured.

[0066] 6) Photodetector 6

[0067] The photodetector 6 is a general commercial product.

[0068] In the present invention, it is necessary to convert the interference intensity change of the output detection light field into a voltage signal for further inversion of trace gas concentration information. A Newport 1623 photodetector is used to receive the light signal, and based on its own 10 kilo-ohm impedance, the photocurrent is converted into a voltage signal, which is output through a BNC signal line for subsequent electrical signal processing.

[0069] It can be seen that the above-mentioned components each play an important role in the photothermal spectroscopy system, and work together to achieve high-sensitivity and high-resolution photothermal measurement and analysis.

[0070] 3. Technology

[0071] The hollow-core anti-resonant optical fiber 4 uses femtosecond laser side-punching technology to guide the gas to be tested into the interior of the hollow-core gas chamber through the microholes, and quickly come into contact with the pump laser, which will effectively improve the photothermal spectroscopy gas detection rate; secondly, at the input optical fiber 3 and the output optical fiber 5, the optical path connection is realized based on the mechanical connection coupling method of the ceramic ferrule and the ceramic sleeve. It is necessary to use a three-dimensional micro-rotation adjustment frame to ensure that the single-mode optical fiber end face is correctly coupled with the hollow-core anti-resonant optical fiber 4 to avoid oblique incidence to excite high-order core modes and reduce the proportion of light energy in the fundamental mode.

[0072] 4. Working mechanism

[0073] Place the sensor in the gas to be tested:

[0074] ① Based on the antiresonance spectrum in the hollow-core antiresonance fiber 4, the central wavelength of the pump beam 1 is adjusted to the antiresonance band of the antiresonance spectrum to ensure that the pump beam 1 is efficiently transmitted in the gas chamber to excite the gas molecules to be measured;

[0075] ② Based on the resonance roll-off band in the hollow-core antiresonant fiber 4, the detection laser is adjusted to the point with the maximum slope in the resonance roll-off band and the optical frequency is locked using a negative feedback loop. The photothermal phase change is demodulated based on the bevel edge to obtain the detection light intensity change signal;

[0076] ③ The photoelectric detector 6 receives the detection light intensity change signal, converts it into an electrical signal output, and obtains the photothermal signal corresponding to the gas molecules to be detected.

[0077] In the photothermal spectroscopy system, the modulated excitation light is incident on the central axis inside the hollow-core antiresonant optical fiber 4 through the input optical fiber 3, interacts with the gas to be measured, and produces a photothermal phase change through the photothermal effect; the excited photothermal effect is converted into an amplitude-amplified photothermal intensity signal through the resonance roll-off band in the hollow-core antiresonant optical fiber 4, and then the photothermal intensity signal is directly output through the output optical fiber 5 and filtered, and the signal is post-processed after passing through the photodetector 6.

[0078] In this system, the efficient excitation of the photothermal effect in the hollow-core antiresonant optical fiber 4 and the amplification of the photothermal signal amplitude in the resonance roll-off band determine the system's comprehensive indicators such as the minimum detection limit, sensitivity, and signal-to-noise ratio. The present invention improves the signal conversion efficiency by adopting an antiresonant hollow-core waveguide chamber 5 with excellent roll-off characteristics, thereby making the system's performance better.

[0079] 5. Application Examples

[0080] 1) Detect a gas

[0081] In this embodiment, an antiresonant hollow core waveguide photothermal spectroscopic gas sensor is used to detect acetylene (C2H2) gas. Specifically, a pump laser with a central wavelength of 1532.83nm is used to excite acetylene gas molecules to transition from the ground state to a high energy level; when these excited molecules return to a lower energy level through a non-radiative relaxation process, heat is released, resulting in a local temperature rise, forming a photothermal effect; this local temperature change causes the phase of the detection laser 2 to change. Since the antiresonant hollow core waveguide has the characteristic of being highly sensitive to thermal phase changes, especially its resonant roll-off band has a linear response to thermal phase changes, the concentration of acetylene gas can be inverted by measuring the change in the phase of the detection laser 2.

[0082] 2) Detection method

[0083] In order to accurately measure the concentration of acetylene, the sensor is placed in a closed air cavity so that the gas to be measured is evenly distributed around the sensor; then, a continuously tuned near-infrared laser with a central wavelength of 1532.83nm is used as a pump laser 1 to stimulate the absorption transition of acetylene molecules. At the same time, another probe laser 2 is introduced, and its wavelength is selected on the resonant roll-off band of the anti-resonant hollow core waveguide. This embodiment uses a probe laser 2 with a central wavelength of 1550nm to monitor the phase change caused by the photothermal effect; by recording and analyzing the linear conversion of the phase of the probe laser 2 to the change in the output light intensity of the probe laser 2, the temperature change caused by the absorption of the laser by the acetylene molecules can be indirectly reflected, and then the concentration of acetylene can be calculated.

[0084] 3) Test results (gas concentration).

[0085] In the specific experiment, by testing acetylene gas samples of different concentrations, the relationship between the peak-to-peak value of the sensor output signal and the concentration of the gas to be measured can be fitted. This embodiment finally measured that when the volume fraction of the acetylene concentration gradually increased from 1ppm to 10000ppm, the sensor output detection light intensity signal changed linearly, that is, the gas concentration and the sensor output signal satisfied a linear relationship. After data processing, it was found that the sensor responded correctly within the range of 99.96%, and the measured signals in the process were significantly higher than the background noise level, meeting the signal-to-noise ratio confidence specification in the field of gas sensing, and the phase-locked circuit output waveform showed a clear harmonic peak structure. This result proves the effective detection ability of the sensor for acetylene gas. Further data processing and calibration work show that the sensor can accurately measure acetylene concentrations as low as ppm level, with high sensitivity and reliability.

[0086] 4) Yes Figure 3 Provide explanation.

[0087] Figure 3A typical schematic diagram of the transmission spectrum of an antiresonant hollow-core fiber is shown. In this chart, the horizontal axis represents the wavelength of light (nm), and the vertical axis represents the corresponding light intensity (dB). It can be seen that within a series of periodic antiresonant transmission bands, there is a very prominent peak located at about 1550nm. This peak is the optical signal distribution output by the ultra-narrow linewidth probe light after passing through the antiresonant hollow-core fiber; the pump laser excites the acetylene molecules to produce a photothermal effect, and the phase of the probe laser 2 changes due to local heating when passing through the hollow-core waveguide. Since the resonant roll-off band of the antiresonant hollow-core waveguide has a linear response to thermal phase changes, the concentration of acetylene gas can be inverted by measuring the change in the phase of the probe laser 2.

[0088] This method not only improves the detection sensitivity, but also enhances the resistance to interference from complex background gases.

Claims

1. An anti-resonant hollow core waveguide photothermal spectroscopy gas sensor, characterized in that: It includes a pump laser (1), a detection laser (2), an input optical fiber (3), a hollow core anti-resonance optical fiber (4), an output optical fiber (5) and a photodetector (6); The pump laser (1) and the detection laser (2) are combined by a coupler and coupled into the air core of the hollow core anti-resonance optical fiber (4) via an input optical fiber (3); The input optical fiber (3), the hollow core anti-resonance optical fiber (4), the output optical fiber (5) and the photoelectric detector (6) are connected in sequence.

2. The anti-resonant hollow core waveguide photothermal spectroscopy gas sensor according to claim 1, characterized in that: The pump laser (1) is a narrow line width continuous laser beam generated by a distributed feedback laser driven by a corresponding current driver.

3. The anti-resonant hollow core waveguide photothermal spectroscopy gas sensor according to claim 1, characterized in that: The detection laser (2) is generated by an ultra-narrow linewidth laser whose linewidth is much smaller than that of the pump laser 1, and is used to receive the local refractive index modulation caused by the photothermal effect to form a photothermal signal containing the concentration information of the gas molecules to be measured.

4. The anti-resonant hollow core waveguide photothermal spectroscopy gas sensor according to claim 1, characterized in that: The hollow core antiresonant optical fiber (4) comprises a waveguide air chamber (4-0), a gas inlet (4-1) and a gas outlet (4-2); the hollow core has a diameter of 32 microns and an outer cladding has a diameter of 125 microns. A waveguide air chamber (4-0) with a length of 5-10 centimeters is formed by vertically cutting at both ends, and a gas inlet (4-1) and a gas outlet (4-2) are arranged on the upper side.

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