A highly sensitive micro gas volume gas detection device and method based on dual-enhanced photothermal spectroscopy

Abstract

The present invention provides a highly sensitive micro gas volume gas detection device and method based on dual-enhanced photo-thermal spectroscopy, which relates to the field of optical sensing and includes a pump light source, a probe light source, a micro-nano fiber loop resonance module, a filter, a photodetector, a signal processing unit, and a control module. By using the above-mentioned highly sensitive micro gas volume gas detection device and method based on dual-enhanced photo-thermal spectroscopy, through a micro-nano fiber ring resonator, dual enhancement of photo-thermal and resonance detection is achieved, enabling a nano-liter gas volume to be equivalent to an absorption optical path of dozens of meters, thereby realizing highly sensitive gas measurement under a micro gas volume.

Description

Technical Field

[0001] The present invention relates to the field of optical sensing, and in particular to a high-sensitivity micro gas volume gas detection device and method based on dual-enhanced photo-thermal spectroscopy. Background Art

[0002] Currently, in the field of gas measurement, for gas detection based on absorption spectroscopy technology, the system is relatively simple, the absorption optical path is short, there is a lack of signal amplification means, and a high gas volume is required. Along with absorption spectroscopy, photoacoustic effect and photo-thermal effect will also occur. Although the absorption optical path of the photoacoustic effect is short, the photoacoustic signal is amplified thousands of times through the resonance of the acoustic cavity, improving the gas measurement accuracy. However, the acoustic resonance frequency of the photoacoustic spectroscopy itself is unstable and is easily affected by acoustic noise. The mechanism of photo-thermal spectroscopy is that gas absorbs light to generate heat, which in turn causes a change in refractive index, and the change amount of refractive index can reflect the gas concentration. Photo-thermal spectroscopy not only has high measurement accuracy but also good stability, and is suitable for high-sensitivity gas detection requirements. However, in many application scenarios, the available gas volume is very limited, but the requirements for the accuracy and sensitivity of gas detection are very high. In the fields of respiratory analysis and disease diagnosis in medical and health, it is necessary to detect extremely trace target compounds, such as volatile organic compounds (VOCs), from the exhaled gas of patients for the diagnosis of diseases such as lung cancer and diabetes. At specific locations in environmental monitoring, such as near soil pores, groundwater wells or plant leaves, micro gas sampling is also required, for example, to monitor methane emissions in the soil or gas exchange between plants and the atmosphere. These places can only provide extremely small gas samples. In the case of very limited gas volume, it is of great significance to improve the detection sensitivity. In addition, in the chromatographic measurement of transformers, the content of various abnormal gases is very low, resulting in a small gas output volume, but the accuracy requirements for the gas are very high. Using micro gas volume to achieve high-precision measurement is of extremely important significance for the health status detection of transformers.

[0003] Aiming at the problems existing in the above application fields, a dual-enhanced photo-thermal spectroscopy gas detection method and device are proposed, which can achieve high-sensitivity gas measurement based on micro gas volume. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-sensitivity micro gas volume gas detection device and method based on dual-enhanced photo-thermal spectroscopy. Through a micro-nano fiber ring resonator, dual enhancement of the resonance method and signal detection is achieved, so that a micro-nano fiber ring with a diameter of hundreds of micrometers can be equivalent to an absorption optical path of dozens of meters, thereby realizing high-sensitivity gas measurement under micro gas volume.

[0005] To achieve the above purpose, the present invention provides a high-sensitivity micro gas volume gas detection device based on dual-enhanced photo-thermal spectroscopy, including

[0006] The laser current controller enables the pump laser to generate tunable pulsed light, causing the probe light to scan near the resonant wavelength of the micro-nano fiber loop;

[0007] The laser temperature controller is used to control the operating temperature of the pump laser and adjust the wavelength of the pump light to match the gas absorption wavelength;

[0008] The pump laser generates pump light. After the light energy is absorbed by the characteristic gas, photothermal energy is generated and heat energy is released;

[0009] The probe laser generates probe light. During the wavelength scanning process, the resonant wavelength of the micro-nano fiber loop can be found;

[0010] The wavelength division multiplexer couples the pump light and the probe light into the micro-nano fiber loop resonator;

[0011] The micro-nano fiber loop resonator enables the pump light to be repeatedly coupled and transmitted in the micro-nano fiber loop and interact with the gas, thereby generating an enhanced photothermal signal; for the probe light, the detection process of the photothermal signal is resonantly amplified, forming a double enhancement phenomenon;

[0012] The narrowband filter converts the spectral change of the probe light into an intensity change;

[0013] The photodetector converts the resonated probe light signal into an electrical signal for the backend processing unit to demodulate the gas concentration information;

[0014] The lock-in amplifier lock-in amplifies the signal after the probe light is photodetected, and the second harmonic proportional to the gas concentration is obtained through demodulation;

[0015] The laser current controller is also used to superimpose a sine wave on the drive current. The drive current is used for wavelength scanning so that the pump wavelength corresponds to the gas absorption wavelength; the sine wave is used for wavelength modulation to improve the signal-to-noise ratio.

[0016] Preferably, the micro-nano fiber loop allows part of the pump light to propagate around the micro-nano fiber in the form of an evanescent field, bringing the pump light into contact with the gas and thus being absorbed by the gas; at the same time, the unabsorbed pump light can be recoupled back into the micro-nano fiber loop to participate in the next light-matter interaction; meanwhile, the micro-nano fiber loop also enables the probe light to resonate in the micro-nano fiber loop.

[0017] Preferably, the wavelength of the pump light corresponds to the absorption spectrum wavelength of the gas to be measured.

[0018] Preferably, the wavelength range of the probe light covers the resonant wavelength range of the micro-nano fiber loop.

[0019] Preferably, the resonant range of the micro-nano fiber loop is related to the diameter of the micro-nano fiber loop and the photothermal intensity.

[0020] Preferably, the diameter of the micro-nano optical fiber is used to determine the size of the evanescent field, the coupling loss and the transmission loss of the probe light.

[0021] Preferably, it further includes a processing unit to implement the functions of data acquisition, filtering and data processing, and obtain the corresponding gas concentration signal through operations on the optical signal.

[0022] Preferably, the micro-nano optical fiber ring resonator can also be alternatively arranged with a planar optical waveguide resonance structure or a micro-ring resonator.

[0023] Preferably, the driving current of the pump light can also be alternatively arranged without superimposing a sine wave.

[0024] A highly sensitive micro gas volume gas detection method based on dual-enhanced photo-thermal spectroscopy includes the following steps:

[0025] Through temperature control, the pump light is made to be near the absorption peak of acetylene gas; the current controller uses the driving current to perform wavelength scanning near the absorption peak, and at the same time superimposes a sine wave on the driving current;

[0026] Use a wavelength division multiplexer to couple the pump light and the probe light into the micro-nano optical fiber ring resonator;

[0027] Form a photo-thermal spectroscopy resonance of the pump light in the micro-nano optical fiber ring, and change the equivalent refractive index of the micro-nano optical fiber ring; the equivalent refractive index is amplified by the resonance of the probe light, and the spectrum of the probe light shifts;

[0028] Convert the spectral change of the probe light into an intensity change through a narrowband filter;

[0029] Lock-in amplify the signal of the probe light after photoelectric detection, and obtain the second harmonic proportional to the gas concentration through demodulation;

[0030] The processing unit obtains the corresponding gas concentration signal through operations on the optical signal of the second harmonic.

[0031] Therefore, the present invention adopts the above-mentioned highly sensitive micro gas volume gas detection device and method based on dual-enhanced photo-thermal spectroscopy, and the technical effects are as follows:

[0032] (1) In terms of enhancing the interaction between light and gas, it can utilize both the high energy density of the micro-nano optical fiber and the long equivalent optical path of the ring resonator; in terms of enhancing the detection of gas absorption signals, resonance amplification is introduced into the refractive index detection of photo-thermal for the first time. The double resonance is realized in the same micro-nano optical fiber ring, with novel theory and compact structure. After double resonance amplification, a micro-nano optical fiber ring with a diameter of hundreds of micrometers can be equivalent to an absorption optical path of dozens of meters, and it is expected to achieve an ultra-high measurement accuracy of ppt level under the condition of a nanoliter gas volume.

[0033] (2) The stability of the micro-nano fiber resonant structure is a key factor in the system, and there are two difficulties in this regard. First, the highly sensitive resonant ring is prone to the detuning problem of working point shift. To address this problem, a thermal equilibrium control method is proposed. Based on the closed-loop feedback control theory of the photo-thermal effect, the detuning direction is judged by wavelength scanning, and then the deviation direction of the temperature is judged. Subsequently, by dynamically adjusting the wavelength scanning frequency, the heat generation is kept constant, and the resonant point of the resonant ring is controlled to remain unchanged.

[0034] (3) It can be applied to occasions where the gas volume is extremely small, such as respiratory gases and transformer oil chromatography, and the measurement accuracy requirements are very high. Description of the Drawings

[0035] Figure 1 Schematic diagram of a highly sensitive micro gas volume gas detection method based on dual-enhanced photo-thermal spectroscopy provided by this embodiment;

[0036] Figure 2 Schematic diagram of the frequency feedback control and locking of the resonant cavity based on thermal control provided by this embodiment;

[0037] Figure 3 It is the system principle block diagram. Specific Embodiments

[0038] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0039] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the present invention belongs.

[0040] Light source selection: The pump laser is selected with a wavelength corresponding to the gas to be measured, and the output power is greater than 10 milliwatts. The probe light can use a semiconductor laser with a wavelength of 1550 nanometers or 1310 nanometers as the light source, and the output power is greater than 1 milliwatt.

[0041] Construction of the micro-nano fiber ring: A ring-shaped resonant cavity is made of silica fiber with a diameter of 1 micrometer (μm), and the circumference of the ring is about 1 centimeter (cm).

[0042] Signal processing configuration: High-performance preamplifiers, band-pass filters, and demodulation circuits are equipped to ensure the integrity and reliability of the signals.

[0043] Control software development: Write a set of control software integrating functions such as light source control, data acquisition, and signal processing, and simplify the operation process through a graphical user interface.

[0044] Detector configuration: Use a high-sensitivity photodiode as the detector to ensure that weak photo-thermal effect signals can be captured.

[0045] Example 1

[0046] A highly sensitive micro gas volume gas detection method based on dual-enhanced photothermal spectroscopy, comprising the following steps:

[0047] Design and application of laser controller

[0048] The laser current controller enables the pump laser to generate tunable pulsed light, and makes the probe light scan near the resonant wavelength of the micro-nano fiber loop. Specifically:

[0049] Modulation frequency: The modulation frequency can be set to 1 kilohertz (kHz).

[0050] Modulation mode: An external modulation method is adopted, that is, the working state of the modulator is controlled by an external signal to realize the modulation of the light beam of the light source.

[0051] The thermal balance control method is specifically reflected in: The laser temperature controller is used to control the temperature of the pump laser to make the pump light near the absorption peak of acetylene gas; the current controller uses the drive current to perform wavelength scanning near the absorption peak, and at the same time superimposes a sine wave on the drive current, and the sine wave is used for wavelength modulation to improve the signal-to-noise ratio.

[0052] The pump light and the probe light are coupled into the micro-nano fiber loop resonator by a wavelength division multiplexer; a photothermal spectroscopy resonance of the pump light is formed in the micro-nano fiber loop, changing the equivalent refractive index of the micro-nano fiber loop; the equivalent refractive index is amplified by the resonance of the probe light, and the spectrum of the probe light shifts;

[0053] The micro-nano fiber loop enables part of the pump light to propagate around the micro-nano fiber in the form of an evanescent field, bringing the pump light into contact with the gas and then being absorbed by the gas; at the same time, it can also make the pump light that is not absorbed by the gas be coupled back into the micro-nano fiber loop again to participate in the next light-matter interaction; at the same time, the micro-nano fiber loop also enables the probe light to have a small transmission loss and a high coupling efficiency, ensuring its resonance in the micro-nano fiber loop.

[0054] There are three ways to determine the diameter of the micro-nano fiber: set according to the pump light wavelength and the probe light wavelength; set according to the excitation efficiency of the pump light and the gas; set according to the resonance efficiency of the probe light.

[0055] Structure and optimization of the micro-nano fiber loop resonance module

[0056] The micro-nano fiber loop resonance module is one of the core components of the present invention, and its function is to use the ring resonator to repeatedly oscillate and enhance the pump light in the cavity, thereby enhancing the interaction between light and gas. Specifically:

[0057] Material selection: Silicon dioxide (SiO2) is selected as the material of the micro-nano optical fiber because of its excellent optical transmission performance and chemical stability, with a refractive index of about 1.44 and a loss coefficient < 0.01 dB / cm.

[0058] Dimension design: The diameter of the micro-nano optical fiber loop is designed to be 1 micrometer (μm), and the total length of the ring resonator is 1 centimeter (cm), with an optical path gain of about 10 4 , to provide a long enough optical path and enhance the interaction between light and gas.

[0059] To achieve the double resonance effect, the length of the micro-nano optical fiber L should satisfy: mλ pump =n pump L and nλ prob =n prob L , where, λ pump and λ prob are the wavelengths of the pump light and the probe light respectively, n pump and n prob are the equivalent refractive indices of the pump light and the probe light respectively, m and n are positive integers. By adjusting the length L and the core diameter of the micro-nano optical fiber, the pump light and the probe light can simultaneously satisfy the resonance conditions.

[0060] (1);

[0061] where, Δ n eff represents the refractive index change caused by the combined effects of the photo-thermal effect and the thermal expansion effect, represents the central wavelength of the probe light. represents the change in the resonance wavelength relative to the central wavelength of the probe light, Δ L represents the change in the length of the micro-nano optical fiber due to photo-thermal generation.

[0062] Coupling efficiency control: The coupling coefficient R prob →0.9999. Through the matching optimization of the core and cladding diameters, a reflectivity of nearly 99.99% is achieved.

[0063] Resonator quality factor Q: The target Q > 10 6 , ensuring high light energy accumulation.

[0064] Free Spectral Range (FSR): FSR = c / (2 n eff L ), by adjusting L to ensure the balance between the measurement range and resolution.

[0065] Enhancement mechanism: By optimizing the geometric parameters of the ring resonator, such as the radius of curvature, core size, etc., to achieve the best light energy accumulation effect.

[0066] Second amplification: Introduce a resonance amplification mechanism in the resonance module to achieve secondary amplification of the photothermal effect by enhancing the detection of the gas absorption signal.

[0067] Photothermal enhancement and second amplification mechanism: By solving the heat conduction equation, the temperature distribution of the micro-nano fiber and the surrounding gas can be obtained. When the pump light propagates in the fiber, due to the photothermal effect, it will cause a local temperature increase, which in turn changes the refractive index of the fiber and the surrounding gas. The refractive index change caused by the temperature increase will cause a change in the optical path of the fiber, thus affecting the propagation characteristics of light. These changes not only enhance the interaction between light and gas, but also increase the amplification of the optical signal through the resonance effect. The combined action of the optical path change caused by temperature and the nonlinear effect in the fiber can achieve the enhancement and amplification of the optical signal. In addition, controlling factors such as the pump light power, geometric parameters and reflectivity of the fiber helps to further optimize the gain effect and achieve more efficient optical signal amplification.

[0068] Solution of the heat conduction equation: The temperature distribution around and within the micro-nano fiber is described by the following equations:

[0069] (2);

[0070] (3);

[0071] Where, represents the density of air, represents the specific heat capacity of air, represents the thermal conductivity of air, represents the temperature gradient, which represents the rate of change of temperature in space, represents the convection term, α c represents the gas absorption coefficient, P pump represents the pump light power, represents the radial distance from the light source, θ represents the angular component in polar coordinates, I nom-evaa ( r , θ ) represents polar coordinates ( r ,θ The light intensity distribution radiated in the unit space under Represents a time - related function, used to represent the modulation of laser power over time or other time - varying effects, Represents the density of materials such as micro - nano optical fibers, Represents the specific heat capacity of the optical fiber, Represents the thermal conductivity of the optical fiber.

[0072] By solving equations (2) and (3), the temperature distributions in the micro - nano waveguide and the surrounding air can be obtained, and then the refractive index changes in the air and the micro - nano waveguide can be obtained. n eff . Both the thermo - optic effect and the thermal expansion effect can cause refractive index changes. Therefore, the refractive index changes here are divided into the refractive index change of the air around the micro - nano optical fiber, the refractive index change of the micro - nano optical fiber itself, and the change in the length of the micro - nano optical fiber caused by the refractive index change. For the convenience of analysis, the three are represented by an equivalent refractive index n eff .

[0073] The equivalent optical path after resonance enhancement L eff , magnification Are:

[0074] (4);

[0075] (5);

[0076] Among them, λ Represents the pump light wavelength, η Represents the coupling coefficient, that is, the coupling efficiency of light transmission in the micro - nano optical fiber, the equivalent reflectivity of the pump light and the probe light R pump = R probe = 99.99%, the signal amplification factor β Can reach 2×10 8 . Further improving the equivalent reflectivity of the pump light and the probe light, then β Will be correspondingly improved.

[0077] Convert the spectral change of the probe light into an intensity change through a narrow - band filter;

[0078] Lock - in amplify the signal of the probe light after photoelectric detection, and obtain the second - harmonic wave proportional to the gas concentration through demodulation;

[0079] The processing unit operates on the optical signal of the second - harmonic wave to obtain the corresponding gas concentration signal.

[0080] Design and implementation of the signal processing unit

[0081] The signal processing unit is used to amplify, filter, and demodulate the weak electrical signals received by the detector to obtain clear detection signals and demodulate the gas concentration. Specifically:

[0082] Amplification circuit: A high-gain low-noise amplifier is adopted to ensure that weak signals can be effectively amplified without introducing additional noise.

[0083] Filter circuit: A band-pass filter is used to filter out the noise in irrelevant frequency bands and retain the useful signals.

[0084] Demodulation circuit: The modulation signal is restored to the original signal through the demodulation circuit for subsequent analysis.

[0085] Functions and implementation of the control module

[0086] The control module is responsible for coordinating the operation process of the entire system, including the modulation of the light source, data acquisition, and signal processing, etc. Specifically:

[0087] Software platform: The LabVIEW development platform is adopted to write control software to implement functions such as light source modulation and data acquisition.

[0088] Coordination mechanism: By writing control logic, ensure the coordinated operation among the light source, modulator, and signal processing unit.

[0089] User interface: Design a friendly user interface to facilitate operators to set system parameters and view measurement results.

[0090] Figure 3 is the schematic diagram of the system structure for light intensity detection. A sine wave is superimposed on the driving current of the wavelength scan to suppress system noise, and then a lock-in amplifier is used to extract the second harmonic in the light intensity signal to demodulate the gas concentration.

[0091] To verify the effect of the present invention, an actual measurement experiment was carried out:

[0092] Experiment preparation: Place a small amount of gas to be measured in a sealed container, and keep the internal temperature of the container constant to avoid the influence of temperature changes on the measurement results.

[0093] System setup: Set up the experimental system according to the above design scheme to ensure that all components are correctly connected.

[0094] Experiment operation: Turn on the light source, convert the light beam into a modulation signal through the modulator, then enter the micro-nano fiber loop resonance module, and finally the signal is captured by the detector and transmitted to the signal processing unit.

[0095] Data analysis: Use the signal processing unit to process the collected data and analyze the change of gas concentration.

[0096] Result verification: By comparing the changes in signal intensity before and after the experiment and the results with traditional detection methods, the superior performance of the present invention in trace gas detection is confirmed.

[0097] Through the detailed description of the above specific embodiments, the present invention provides a method and device for realizing highly sensitive measurement of tiny gas volume based on double-enhanced photo-thermal spectroscopy of micro-nano fiber loop, which not only improves the detection sensitivity, but also simplifies the operation process and has broad application prospects.

[0098] As Figure 1 shown, as a preferred embodiment of the specific embodiment of the present invention, this embodiment provides a highly sensitive tiny gas volume gas detection device based on double-enhanced photo-thermal spectroscopy, including a pump light source, a probe light source, a micro-nano fiber loop resonance module, a signal processing unit, a control module, etc.;

[0099] Figure 2 Using the modulation method of photo-thermal spectroscopy, the thermal equilibrium of the micro-nano fiber loop is controlled, and then the resonance frequency of the micro-nano fiber loop is stabilized within a certain range. Then, the swept frequency of the pump light is used to correspond to the cavity frequency within this range. The specific method is as follows: Periodically control the wavelength of the pump light to scan near the gas absorption peak through the driving current. By scanning the wavelength near the gas absorption peak, judge the wavelength change direction of the resonance ring detuning. The temperature can be estimated from the direction of the wavelength detuning change. When the temperature is low, increase the scanning period, and when the temperature is high, decrease the scanning period, so that the temperature is stabilized within a small range to ensure that the scanning of the absorption peak by the pump light can be within the resonance range.

[0100] Therefore, the present invention adopts the above-mentioned highly sensitive tiny gas volume gas detection device and method based on double-enhanced photo-thermal spectroscopy. Through a micro-nano fiber ring resonator, the resonance method and signal detection are both enhanced, so that a micro-nano fiber loop with a diameter of hundreds of micrometers can be equivalent to an absorption optical path of dozens of meters, thereby realizing highly sensitive gas measurement under tiny gas volume.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A highly sensitive and small amount of gas detection device based on dual enhanced photothermal spectroscopy, characterized in that: include The laser current controller enables the pump light laser to generate tunable pulse light, so that the detection light is scanned near the resonance wavelength of the micro-nano optical fiber ring; The laser temperature controller is used to control the operating temperature of the pump light laser and adjust the wavelength of the pump light to match the gas absorption wavelength; The pump light laser generates pump light, and the light energy is absorbed by the characteristic gas to generate photothermal energy, releasing heat energy; The detection light laser generates detection light, and the resonant wavelength of the micro-nano optical fiber ring can be found during the wavelength scanning process; The wavelength division multiplexer couples the pump light and the probe light into the micro-nano fiber ring resonator; The micro-nano fiber ring resonator allows the pump light to be repeatedly coupled and transmitted in the micro-nano fiber ring and interact with the gas, thereby generating an enhanced photothermal signal; for the detection light, the detection process of the photothermal signal is resonantly amplified, forming a double enhancement phenomenon; The narrowband filter converts the spectral changes of the probe light into changes in light intensity; The photoelectric detector converts the resonant detection light signal into an electrical signal for the back-end processing unit to demodulate the gas concentration information; The phase-locked amplifier amplifies the signal of the detection light after photoelectric detection, and obtains the second harmonic proportional to the gas concentration through demodulation; The laser current controller is also used to superimpose a sine wave on the drive current. The drive current is used for wavelength scanning so that the pump wavelength corresponds to the gas absorption wavelength. The sine wave is used for wavelength modulation to improve the signal-to-noise ratio. By adjusting the length of micro-nano optical fiber L and the core diameter, so that the pump light and the probe light meet the resonance conditions at the same time （1）； in, It represents the refractive index change caused by the photothermal effect and thermal expansion effect. represents the central wavelength of the detection light, It represents the change of the resonant wavelength relative to the central wavelength of the probe light. Indicates the change in length of the micro-nano optical fiber caused by photothermal generation; Equivalent optical path after resonance enhancement , magnification for: （2）； （3）； in, represents the wavelength of pump light, is the coupling coefficient, represents the equivalent reflectivity of the pump light, represents the equivalent reflectivity of the detection light, represents the transmittance of the resonant cavity; The wavelength of the pump light is periodically controlled by driving current to scan near the gas absorption peak. By scanning the wavelength near the gas absorption peak, the direction of wavelength change of the resonant ring detuning is determined. The direction of detuning is determined by wavelength scanning, and then the direction of temperature deviation is determined. Then, by dynamically adjusting the wavelength scanning frequency, the heat generation is kept constant and the resonance point of the resonant ring is controlled to remain unchanged.

2. According to claim 1, a highly sensitive and small amount of gas detection device based on dual enhanced photothermal spectroscopy is characterized in that: The wavelength range of the detection light covers the resonance wavelength range of the micro-nano optical fiber ring.

3. According to claim 1, a highly sensitive and small amount of gas detection device based on dual enhanced photothermal spectroscopy is characterized in that: It also includes a processing unit to realize the functions of data collection, filtering and data processing, and obtains the corresponding gas concentration signal through calculation of the optical signal.

4. A highly sensitive and small amount of gas detection method based on dual enhanced photothermal spectroscopy, characterized in that: The highly sensitive small amount of gas detection device based on double enhanced photothermal spectroscopy as described in any one of claims 1 to 3 is implemented, comprising the following steps: By controlling the temperature, the pump light is placed near the absorption peak of acetylene gas; the current controller uses the driving current to scan the wavelength near the absorption peak, and at the same time superimposes a sine wave on the driving current; A wavelength division multiplexer is used to couple the pump light and the probe light into the micro-nano fiber ring resonator; The photothermal spectrum resonance of the pump light is formed in the micro-nano optical fiber ring, which changes the equivalent refractive index of the micro-nano optical fiber ring; the equivalent refractive index is amplified by the resonance of the detection light, and the spectrum of the detection light is shifted; The spectrum changes of the detection light are converted into light intensity changes through a narrow-band filter; The signal of the detection light after photoelectric detection is phase-locked and amplified, and the second harmonic proportional to the gas concentration is obtained by demodulation; The processing unit calculates the second harmonic optical signal to obtain a corresponding gas concentration signal.

Images