Dual-laser gas isotope abundance measuring device and method

Abstract

The invention discloses a double-laser gas isotope abundance measuring device and method. In the scheme, two laser devices are used for providing two paths of light beams with different wavelengths, the two paths of light beams with different wavelengths are flexibly switched through a laser switching module, and a light beam with a specific frequency is selected to enter a cavity and is reflected for multiple times in the cavity to interact with gas to be detected; the photoelectric detection system converts optical signals corresponding to the light beams after interaction in the cavity into electric signals and sends the electric signals to the spectrum scanning and data acquisition system, and the spectrum scanning and data acquisition system records spectrum data of the electric signals and sends control signals to control the laser switching module. Different from the prior art in which one laser device needs to measure spectra of different isotopes of isotope molecules in a time-sharing manner for measuring isotope abundance, the pressure and temperature of sample gas need to be measured with enough high precision. Compared with the condition that the sample gas pressure precision is not high enough in the prior art, the method has obvious advantages.

Description

Technical Field

[0001] The present application relates to the field of laser measurement technology, and in particular to a dual-laser gas isotope abundance measurement device and method. Background Art

[0002] Isotopes refer to atoms of the same element with the same number of protons but different numbers of neutrons, and isotope molecules refer to molecules composed of isotope atoms of the same element. These molecules are the same in chemical structure, but due to the difference in the mass of the isotopes, their physical properties (such as vibration frequency, moment of inertia, etc.) are different. Different isotopes have different abundances in nature, and these differences can reflect the origin, history and environmental changes of the substance. Therefore, the analysis of isotope abundance has important applications in earth sciences (climate change, geological processes, etc.), environmental sciences (pollution tracing, carbon cycle, etc.), life sciences (biological metabolism, archaeology and paleoecology, etc.), industrial and energy applications (nuclear energy, oil and natural gas, etc.), and medical diagnosis (isotope tracing, etc.).

[0003] Laser absorption spectroscopy is an advanced method for isotope abundance detection. This method is based on the fact that molecules with different isotopic compositions have different absorption characteristics for lasers of specific wavelengths, and the ratio of isotopes in the target gas is determined by measuring these absorption differences. However, a laser to measure isotope abundance requires time-sharing measurements of the spectra of different isotopes of isotope molecules. The pressure and temperature of the sample gas must be measured with sufficiently high accuracy, which is extremely challenging for the experiment, especially the pressure of the sample, which is mainly reflected in the following aspects: 1) Any vacuum cavity has problems of adsorption and desorption, which will cause the purity of the gas sample to change over time and is difficult to evaluate; 2) The temperature of the cavity will also change over time, which will affect the intensity of spectral line transitions and the distribution of the number density of molecules in the cavity, causing measurement errors; 3) The most accurate thin-film pressure gauge currently available can only achieve a measurement accuracy of 0.025%, and requires frequent calibration, is expensive, and is difficult to popularize.

[0004] In summary, when the accuracy of the sample gas pressure is not high enough, how to improve the spectral measurement accuracy of different isotopes of isotope molecules is a technical problem that needs to be solved urgently. Summary of the invention

[0005] Based on the above problems, the present application provides a dual-laser gas isotope abundance measurement device and method, the purpose of which is to improve the spectral measurement accuracy of different isotopes of isotope molecules.

[0006] The embodiments of the present application disclose the following technical solutions: In a first aspect, the present application provides a dual-laser gas isotope abundance measurement device, the device comprising: a laser 1, a laser 2, a laser switching module, a cavity, a photoelectric detection system, and a spectrum scanning and data acquisition system; The laser 1 is connected to the laser switching module and is used to provide a light beam of a first wavelength; The second laser is connected to the laser switching module and is used to provide a light beam of a second wavelength; The laser switching module is connected to the laser 1 and the laser 2, and is also connected to the cavity and the spectrum scanning and data acquisition system, and is used to switch between the light beam of the first wavelength and the light beam of the second wavelength based on a control signal, and select one light beam for output; the control signal is sent multiple times by the spectrum scanning and data acquisition system according to a preset program; The cavity is connected to the laser switching module and the photoelectric detection system, and is used to receive the light beam output by the laser switching module. Through multiple reflections, the light beam interacts with the gas to be measured filled in the cavity, and outputs the light beam after interaction; The photoelectric detection system is connected to the cavity and the spectrum scanning and data acquisition system, and is used to receive the light beam after the interaction, convert the light signal corresponding to the light beam after the interaction into an electrical signal, and output the electrical signal; The spectrum scanning and data acquisition system is connected to the photoelectric detection system and the laser switching module, and is used to receive the electrical signal, scan the electrical signal, and measure the spectrum data corresponding to the electrical signal.

[0007] Optionally, the spectrum scanning and data acquisition system is also used for: Based on the spectral data corresponding to the electrical signal, the isotope abundance of the gas to be measured is calculated, and the calculation formula is as follows: ; In the above formula, Ratio is the isotopic abundance of the gas to be measured, X1 is the concentration of isotope one of the gas to be measured, X2 is the concentration of isotope two of the gas to be measured, Area1 is the area of ​​the absorption line of isotope one of the gas to be measured, and Area2 is the area of ​​the absorption line of isotope two of the gas to be measured; S1(T) is the transition intensity of the absorption line of isotope one of the gas to be measured, and S2(T) is the transition intensity of the absorption line of isotope two of the gas to be measured; the Area1 and the Area2 are obtained based on the spectral data of the gas to be measured; the S1(T) and the S2(T) are obtained based on the database.

[0008] Optionally, the device further comprises: an electronic automatic feedback control system; The electronic automatic feedback control system is connected to the photoelectric detection system, the laser one and the laser two, and is used to receive the electrical signal, generate an error signal by demodulating the electrical signal, and adjust the laser one and the laser two respectively based on the error signal so that the frequency of the first wavelength light beam and the frequency of the second wavelength light beam both match the longitudinal mode frequency of the cavity.

[0009] Optionally, the device further comprises: a beam combiner; The beam combiner is connected to the laser one and the laser two, and is also connected to the laser switching module, and is used to combine the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam, and emit the composite light beam to the laser switching module.

[0010] Optionally, the laser switching module is also used for: Based on the control signal, modulating the composite light beam; the modulation includes adjusting the phase or polarization state of the light beam; According to the beam characteristics of the modulated composite light beam, a light beam of a target wavelength is separated from the composite light beam as an output; the light beam of the target wavelength is one of the light beam of the first wavelength and the light beam of the second wavelength.

[0011] The second aspect of the present application provides a dual-laser gas isotope abundance measurement method, which is applied to the dual-laser gas isotope abundance measurement device provided in the first aspect, and the method comprises: The laser 1 provides a light beam of a first wavelength; The second laser provides a light beam of a second wavelength; The laser switching module switches between the light beam of the first wavelength and the light beam of the second wavelength based on the control signal, and selects one light beam for output; the control signal is sent multiple times by the spectrum scanning and data acquisition system according to a preset program; The cavity receives the light beam output by the laser switching module, and the light beam interacts with the gas to be measured filled in the cavity through multiple reflections, and outputs the light beam after the interaction; The photoelectric detection system receives the light beam output by the cavity, receives the light beam after interaction, converts the light signal corresponding to the light beam after interaction into an electrical signal, and outputs the electrical signal; The spectrum scanning and data acquisition system receives the electrical signal, scans the electrical signal, and measures the spectrum data corresponding to the electrical signal.

[0012] Optionally, after the spectrum scanning and data acquisition system receives the electrical signal, scans the electrical signal, and measures the spectrum data corresponding to the electrical signal, the method further includes: Based on the spectral data corresponding to the electrical signal, the isotope abundance of the gas to be measured is calculated, and the calculation formula is as follows: ; In the above formula, Ratio is the isotopic abundance of the gas to be measured, X1 is the concentration of isotope one of the gas to be measured, X2 is the concentration of isotope two of the gas to be measured, Area1 is the area of ​​the absorption line of isotope one of the gas to be measured, and Area2 is the area of ​​the absorption line of isotope two of the gas to be measured; S1(T) is the transition intensity of the absorption line of isotope one of the gas to be measured, and S2(T) is the transition intensity of the absorption line of isotope two of the gas to be measured; the Area1 and the Area2 are obtained based on the spectral data of the gas to be measured; the S1(T) and the S2(T) are obtained based on the database.

[0013] Optionally, after receiving the interacted light beam, converting the optical signal corresponding to the interacted light beam into an electrical signal, and outputting the electrical signal, the method further includes: An electronic automatic feedback control system receives the electrical signal, generates an error signal by demodulating the electrical signal, and adjusts the laser one and the laser two based on the error signal, so that the frequency of the first wavelength light beam and the frequency of the second wavelength light beam both match the longitudinal mode frequency of the cavity.

[0014] Optionally, before switching between the light beam of the first wavelength and the light beam of the second wavelength and selecting one light beam for output, the method further includes: The beam combiner combines the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam, and transmits the composite light beam to the laser switching module.

[0015] Optionally, after the beam combiner combines the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam and transmits the composite light beam to the laser switching module, the method further includes: The laser switching module modulates the composite light beam based on the control signal; the modulation includes adjusting the phase or polarization state of the light beam; According to the beam characteristics of the modulated composite light beam, a light beam of a target wavelength is separated from the composite light beam as an output; the light beam of the target wavelength is one of the light beam of the first wavelength and the light beam of the second wavelength.

[0016] Compared with the prior art, this application has the following beneficial effects: The dual-laser gas isotope abundance measurement device and method provided in the present application use two lasers to provide two light beams of different wavelengths, and flexibly switch between the two light beams of different wavelengths through a laser switching module, select a light beam of a specific frequency to enter the cavity and interact with the gas to be measured after multiple reflections in the cavity, and the photoelectric detection system converts the optical signal corresponding to the light beam after the interaction in the cavity into an electrical signal, and sends the electrical signal to the spectral scanning and data acquisition system, which is responsible for not only recording the spectral data of the electrical signal, but also controlling the laser switching module through a control signal to select a light beam of a specific frequency to enter the cavity.

[0017] By using two lasers, two transition spectral lines can be measured simultaneously, and the laser switching module can be controlled to select a light beam of a specific frequency to enter the cavity as needed. Compared with the current use of one laser to measure isotope abundance, which requires time-sharing measurement of the spectra of different isotopes of isotope molecules, and faces the problem that the accuracy of the gas pressure to be measured is not high enough, this method can eliminate the influence of system errors such as the gas pressure to be measured, temperature drift, and nonlinearity of the detector and acquisition card, thereby significantly improving the spectral measurement accuracy of different isotopes of the gas molecules to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 A schematic diagram of the structure of a dual-laser gas isotope abundance measurement device provided in an embodiment of the present application; Figure 2 A schematic diagram of the measurement results of CO molecules provided in an embodiment of the present application; Figure 3 Allan variance diagram of the CO molecule measurement results provided in the embodiment of the present application; Figure 4 A schematic structural diagram of another dual-laser gas isotope abundance measurement device provided in an embodiment of the present application; Figure 5 A flow chart of a dual-laser gas isotope abundance measurement method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] As described above, currently a laser that measures isotope abundance requires measuring the spectra of different isotopes of isotope molecules in time. The pressure and temperature of the sample gas must be measured with sufficiently high accuracy, which is extremely challenging for the experiment, especially the pressure of the sample, which is mainly reflected in the following aspects: 1) Any vacuum cavity has problems of adsorption and desorption, which will cause the purity of the gas sample to change over time and is difficult to evaluate; 2) The temperature of the cavity will also change over time, thereby affecting the intensity of spectral line transitions and the distribution of molecular number density in the cavity, causing measurement errors; 3) The most accurate thin-film pressure gauge currently available can only achieve a measurement accuracy of 0.025%, and requires frequent calibration, is expensive, and is difficult to popularize.

[0021] In summary, when the accuracy of the sample gas pressure is not high enough, how to improve the spectral measurement accuracy of different isotopes of isotope molecules is a technical problem that needs to be solved urgently.

[0022] In view of the above problems, the inventors have proposed a dual-laser gas isotope abundance measurement device and method after research. The device includes laser one, laser two, a laser switching module, a cavity, a photoelectric detection system and a spectral scanning and data acquisition system.

[0023] Laser 1 is connected to the laser switching module and is used to provide a light beam with a first wavelength.

[0024] Laser 2 is connected to the laser switching module and is used for providing a light beam with a second wavelength.

[0025] The laser switching module is connected to laser one and laser two, and is also connected to the cavity and the spectrum scanning and data acquisition system. It is used to switch between the light beam of the first wavelength and the light beam of the second wavelength based on the control signal, and select one light beam for output; the control signal is sent multiple times by the spectrum scanning and data acquisition system according to a preset program.

[0026] The cavity is connected to the laser switching module and the photoelectric detection system, and is used to receive the light beam output by the laser switching module. Through multiple reflections, the light beam interacts with the gas to be measured filled in the cavity, and the interacted light beam is output.

[0027] The photoelectric detection system is connected to the cavity and the spectrum scanning and data acquisition system, and is used to receive the light beam after interaction, convert the optical signal corresponding to the light beam after interaction into an electrical signal, and output the electrical signal.

[0028] The spectrum scanning and data acquisition system is connected to the photoelectric detection system and the laser switching module, and is used to receive the electrical signal, scan the electrical signal, and measure the spectrum data corresponding to the electrical signal.

[0029] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] See also Figure 1 , which is a schematic diagram of the structure of a dual-laser gas isotope abundance measurement device provided in an embodiment of the present application. Figure 1 As shown, the device includes: laser one, laser two, a laser switching module, a cavity, a photoelectric detection system and a spectrum scanning and data acquisition system.

[0031] Laser 1 is connected to the laser switching module and is used to provide a light beam with a first wavelength.

[0032] Laser 2 is connected to the laser switching module and is used for providing a light beam with a second wavelength.

[0033] The laser in this embodiment includes an external cavity semiconductor laser or a narrow linewidth fiber laser. By using two lasers with different wavelengths, the device allows the measurement of different isotopes in the same gas to be measured. The first wavelength and the second wavelength are selected based on the absorption characteristics of the specific isotope in the gas to be measured, and correspond to the transition spectral lines of different isotopes of the gas molecules to be measured. Different gas isotopes have different absorption rates for light of different wavelengths, so choosing the correct wavelength is also very important for accurate measurement.

[0034] The laser switching module is connected to laser one and laser two, and is also connected to the cavity and the spectrum scanning and data acquisition system. It is used to switch between the light beam of the first wavelength and the light beam of the second wavelength based on the control signal, and select one light beam for output; the control signal is sent multiple times by the spectrum scanning and data acquisition system according to a preset program.

[0035] When a specific measurement task needs to be performed, the spectrum scanning and data acquisition system sends a control signal to the laser switching module. This control signal is a continuous control signal that contains information about which wavelength should be used. If the control signal indicates the use of the first wavelength, the laser switching module selects the first wavelength beam provided by laser one and directs it to the cavity; if the control signal indicates the use of the second wavelength, the laser switching module selects the second wavelength beam provided by laser two and directs it to the cavity. The laser switching module can be implemented through a variety of technologies, such as an electro-optic modulator (EOM) or a fiber coupler and an optical switch.

[0036] The cavity is connected to the laser switching module and the photoelectric detection system, and is used to receive the light beam output by the laser switching module. Through multiple reflections, the light beam interacts with the gas to be measured filled in the cavity, and the interacted light beam is output.

[0037] The cavity is filled with the gas to be measured. In a feasible implementation, the cavity is an optical resonant cavity composed of a pair of high-reflectivity mirrors with a reflectivity greater than 99.99%. When the light beam is reflected multiple times in the cavity, it will interact with the gas molecules to be measured by absorption, scattering, etc. Different gas isotopes have different absorption characteristics for light of a specific wavelength, so information about the gas composition can be obtained by analyzing the changes in the light beam. This cavity-enhanced spectroscopy technology allows the light beam to be reflected multiple times and interact with the gas to be measured, significantly increasing the interaction time between the light beam and the gas molecules to be measured, enhancing the intensity of the absorption signal, and improving the detection sensitivity of the gas to be measured.

[0038] The photoelectric detection system is connected to the cavity and the spectrum scanning and data acquisition system, and is used to receive the light beam after interaction, convert the optical signal corresponding to the light beam after interaction into an electrical signal, and output the electrical signal.

[0039] In one achievable embodiment, the photoelectric detection system includes a high-sensitivity photodetector (such as a photodiode, a photomultiplier tube or a CCD / CMOS sensor) and a signal amplification and processing module; the signal amplification and processing module includes an amplifier and an analog-to-digital conversion.

[0040] The photodetector is connected to the cavity and the amplifier and is used to convert the received optical signal into an initial electrical signal.

[0041] The amplifier is connected to the photodetector and the analog-to-digital converter to amplify the initial electrical signal.

[0042] The analog-to-digital converter is connected to the amplifier and the spectrum scanning and data acquisition system, and is used to convert the amplified initial electrical signal into a digital signal for output.

[0043] The photoelectric detection system is an indispensable part of the dual laser gas isotope abundance measurement device. It lays the foundation for subsequent precise measurements by converting complex optical signals into easy-to-process electrical signals.

[0044] The spectrum scanning and data acquisition system is connected to the photoelectric detection system and the laser switching module, and is used to receive the electrical signal, scan the electrical signal, and measure the spectrum data corresponding to the electrical signal.

[0045] In one possible implementation: A preset program is set according to experimental requirements, and the spectrum scanning and data acquisition system sends a control signal to the laser switching module according to the preset program; the control signal is used to instruct the laser switching module to switch between the light beam of the first wavelength and the light beam of the second wavelength.

[0046] Receive the electrical signal sent by the photoelectric detection system, scan the electrical signal, and measure the spectral data of the gas to be tested; the spectral data includes wavelength, position and width of absorption peak, etc.

[0047] According to actual needs, the spectrum scanning and data acquisition system repeats the above-mentioned process of interaction within the cavity and conversion of the photoelectric detection system by continuously sending control signals to the laser switching module.

[0048] The spectral scanning and data acquisition system is not only connected to the photoelectric detection system to receive electrical signals, but also connected to the laser switching module to send control signals. It can dynamically adjust the light beam output by the laser switching module according to measurement requirements or preset programs, and collect spectral data multiple times in order to analyze the final spectral data.

[0049] Take the measurement of different isotopes of CO molecules at the same pressure and temperature as an example. The experimental conditions are gas pressure 100Pa and temperature 296K. Figure 2 and Figure 3 Shown are actual measurement results obtained through experiments. Figure 2 In the figure, the horizontal axis Spec represents the spectral points in the measured spectral data, each point corresponds to a specific wavelength or frequency, the vertical axis represents the absorption coefficient of the molecule to be measured at different frequency points, the unit is cm / molecule, S1 and S2 are the areas of the two transition spectral lines of the CO molecule in the V=3-0 vibration band measured over a long period of time, S-ratio (296K) is the result of the real-time area ratio of the two spectral lines, and the average value is 1.37612. Figure 3 Middle, horizontal axis is the time constant in seconds, the vertical axis The gray curve is recorded as “Allan Deviation of S1 / S1_avg”, which indicates the Allan Deviation of the area S1 of a spectrum line to the average value S1_avg of S1. The blue curve is recorded as “Allan Deviation of S2 / S2_avg”, which indicates the Allan Deviation of the area S2 of another spectrum line to the average value S2_avg of S2. The red curve is recorded as “Allan Deviation of S r / S r _avg", which means the area ratio of S1 to S2 r For S r Average valuer _avg Allan variance. Figure 2 and Figure 3 It can be seen that the area of ​​a single absorption peak drifts over time, but the ratio of the areas of the two spectral lines is stable.

[0050] The dual-laser gas isotope abundance measurement device provided in the embodiment of the present application uses two lasers to provide two light beams of different wavelengths, and flexibly switches between the two light beams of different wavelengths through a laser switching module, selects a light beam of a specific frequency to enter the cavity and interacts with the gas to be measured after multiple reflections in the cavity, and the photoelectric detection system converts the optical signal corresponding to the light beam after the interaction in the cavity into an electrical signal, and sends the electrical signal to the spectral scanning and data acquisition system, which is responsible for not only recording the spectral data of the electrical signal, but also controlling the laser switching module through a control signal to select a light beam of a specific frequency to enter the cavity.

[0051] By using two lasers, two transition spectral lines can be measured simultaneously, and the laser switching module can be controlled to select a light beam of a specific frequency to enter the cavity as needed. Compared with the current use of one laser to measure isotope abundance, which requires time-sharing measurement of the spectra of different isotopes of isotope molecules, and faces the problem that the accuracy of the gas pressure to be measured is not high enough, this method can eliminate the influence of system errors such as the gas pressure to be measured, temperature drift, and nonlinearity of the detector and acquisition card, and significantly improve the spectral measurement accuracy of different isotopes of the gas molecules to be measured.

[0052] See also Figure 4 , which is a schematic diagram of the structure of another dual-laser gas isotope abundance measurement device provided in the embodiment of the present application. In order to further improve the structure of the dual-laser gas isotope abundance measurement device, an electronic automatic feedback control system and a beam combiner are added. Figure 4 As shown, the device includes: laser one, laser two, a beam combiner, a laser switching module, a cavity, a photoelectric detection system, an electronic automatic feedback control system, and a spectrum scanning and data acquisition system.

[0053] Laser 1 is connected to the laser switching module and the electronic automatic feedback control system, and is used for providing a light beam of a first wavelength.

[0054] Laser 2 is connected to the laser switching module and the electronic automatic feedback control system, and is used for providing a light beam of a second wavelength.

[0055] The beam combiner is connected to the laser one, the laser two and the laser switching module, and is used to combine the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam, and emit the composite light beam to the laser switching module.

[0056] Common beam combiners include polarization beam combiners and fiber beam combiners. By using a beam combiner, beams of different wavelengths can be easily managed, which is particularly important in a research environment where experimental conditions need to be frequently adjusted.

[0057] The laser switching module is connected to the beam combiner, the cavity and the spectrum scanning and data acquisition system, and is used to modulate the composite light beam based on the control signal; the modulation includes adjusting the phase or polarization state of the light beam; and according to the beam characteristics of the modulated composite light beam, a light beam of a target wavelength is separated from the composite light beam as an output.

[0058] The control signal is sent multiple times by the spectrum scanning and data acquisition system according to a preset program; the light beam of the target wavelength is one of the light beam of the first wavelength and the light beam of the second wavelength.

[0059] In one feasible implementation, the composite light beam is modulated based on a control signal, for example, using an EOM or an acousto-optic modulator (AOM) to change the phase of the light beam, and using a polarization controller or a polarization modulator to change the polarization direction of the light beam; according to the beam characteristics of the modulated composite light beam, a light beam of a target wavelength is separated from the composite light beam as an output, for example, by using a polarizing beam splitter (PBS) or a tunable filter to perform beam separation, wherein the PBS can separate light beams of different wavelengths according to the polarization state of the light beam, and the tunable filter can selectively transmit a light beam of a specific wavelength according to the phase or other characteristics after modulation.

[0060] In this design, the laser switching module is not just a simple switch device, but a complex system that integrates modulation and splitting functions. By precisely controlling the phase or polarization state of the light beam and combining appropriate splitting elements, the target wavelength light beam can be separated from the composite light beam for output.

[0061] The cavity is connected to the laser switching module and the photoelectric detection system, and is used to receive the light beam output by the laser switching module. Through multiple reflections, the light beam interacts with the gas to be measured filled in the cavity, and the interacted light beam is output.

[0062] In a feasible implementation, the cavity receives a light beam of a specific wavelength that has been modulated and selected. The light beam that enters the cavity is reflected back and forth between high-reflectivity mirrors. During each reflection, the light beam interacts with the gas molecules to be measured filled in the cavity. After multiple reflections and sufficient interaction with the gas molecules, the light beam is finally output from an exit of the cavity. At this point, the light beam already contains a lot of information about the gas to be measured. After multiple reflections and interaction with the gas to be measured, the interaction time between the light beam and the gas molecules is significantly increased, the intensity of the absorption signal is enhanced, and the detection sensitivity of the gas to be measured is improved.

[0063] The photoelectric detection system is connected to the cavity and the spectrum scanning and data acquisition system, and is used to receive the light beam after interaction, convert the optical signal corresponding to the light beam after interaction into an electrical signal, and output the electrical signal.

[0064] The photoelectric detection system converts the optical signal corresponding to the interacting light beam into an electrical signal. The photoelectric detection system is also used to amplify, filter and perform analog-to-digital conversion on the electrical signal to facilitate subsequent analysis.

[0065] The electronic automatic feedback control system is connected to the photoelectric detection system, laser one and laser two, and is used to receive electrical signals, generate error signals by demodulating the electrical signals, and adjust laser one and laser two respectively based on the error signals so that the frequencies of the light beams of the first wavelength and the second wavelength match the longitudinal mode frequencies of the cavity.

[0066] In one achievable implementation, the electronic automatic feedback control system demodulates the received electrical signal, extracts information about the difference between the beam frequency and the cavity longitudinal mode frequency, and generates an error signal based on this information, indicating the deviation of the current beam frequency from the ideal frequency (i.e., the cavity longitudinal mode frequency), wherein the cavity longitudinal mode frequency is preset. According to the generated error signal, the output frequencies of laser 1 and laser 2 are adjusted in real time to ensure that their frequencies match the cavity longitudinal mode frequency, and this adjustment is usually achieved by changing the operating current or temperature of the laser.

[0067] The electronic automatic feedback control system receives the electrical signal from the photoelectric detection system, demodulates and generates an error signal, and then adjusts the output frequency of Laser 1 and Laser 2 in real time based on this signal to ensure that its frequency matches the longitudinal mode frequency of the cavity. This method not only improves the precision and accuracy of the measurement, but also enhances the robustness and adaptability of the system.

[0068] The spectrum scanning and data acquisition system is connected to the photoelectric detection system and the laser switching module, and is used to receive the electrical signal, scan the electrical signal, and measure the spectrum data of the gas to be tested.

[0069] The spectral scanning and data acquisition system scans the electrical signal according to the preset scanning parameters, such as the starting wavelength, ending wavelength, scanning step and speed, and records the spectral data corresponding to the electrical signal. By continuously sending control signals to the laser switching module, the two light beams are switched back and forth, and the spectral data is continuously collected and recorded. During measurement, in order to avoid the influence of laser power drift, fluctuations in the transmittance of optical media, etc., it is usually necessary to scan the wavelength, and by recording the laser spectrum within a certain wavelength range, the complete envelope of an isolated spectral line of the target gas molecule is obtained, and the integration method is used to eliminate The influence of the linear function, thus obtaining the area of ​​the absorption line Area and the gas concentration X gas The relationship between is as follows: ; In the above formula, k v is the absorption rate, which is the concentration X of the gas molecules being measured under pressure P gas , the transition intensity S(T) and line shape function of the absorption line The function of , and the linear function satisfies . From this we can see that ; The spectrum scanning and data acquisition system can automatically control the laser switching module to switch between the two beams according to the preset scanning parameters, and continuously collect and record spectrum data. This method not only improves the accuracy and efficiency of measurement, but also provides reliable data support for in-depth analysis of gas composition.

[0070] Spectral scanning and data acquisition systems are also used for: Based on the spectral data corresponding to the electrical signal, the isotope abundance of the gas to be tested is calculated. The specific formula is as follows: ; In the above formula, Ratio is the isotopic abundance of the gas to be measured, X1 is the concentration of isotope one of the gas to be measured, X2 is the concentration of isotope two of the gas to be measured, Area1 is the area of ​​the absorption line of isotope one of the gas to be measured, and Area2 is the area of ​​the absorption line of isotope two of the gas to be measured; S1(T) is the transition intensity of the absorption line of isotope one of the gas to be measured, and S2(T) is the transition intensity of the absorption line of isotope two of the gas to be measured; the Area1 and the Area2 are obtained based on the spectral data of the gas to be measured; the S1(T) and the S2(T) are obtained based on the database.

[0071] Among them, there are many public physical and chemical databases that contain a large amount of transition intensity data of known substances. These data usually come from high-level experimental research and theoretical calculations. For example, the database HITRAN discloses the absorption line parameters (including spectral line centers, S(T), etc.) of dozens of major atmospheric molecules and their isotopes.

[0072] Another dual-laser gas isotope abundance measurement device provided in an embodiment of the present application uses two lasers to simultaneously measure different isotopes of the gas molecules to be measured, and simultaneously obtains the absorption spectra of the different isotopes, and respectively fits the areas of the absorption spectra. According to the areas of the two absorption spectra, the isotope abundance value is calculated, thereby eliminating the influence of system errors such as the pressure and temperature drift of the gas to be measured, and the nonlinearity of the detector and the acquisition card, and significantly improving the measurement accuracy and stability of the gas isotope abundance.

[0073] Based on the dual-laser gas isotope abundance measurement device introduced in the previous embodiment, the present application also provides a dual-laser gas isotope abundance measurement method. Figure 5 The flowchart of this method is shown in Figure 2. Figure 5 As shown, the method comprises the following steps: S501, laser 1 provides a light beam with a first wavelength, and laser 2 provides a light beam with a second wavelength.

[0074] The laser in this embodiment includes an external cavity semiconductor laser or a narrow linewidth fiber laser. By using two lasers with different wavelengths, the device allows the measurement of different isotopes in the same gas to be measured or different states of the same isotope. The wavelength is selected based on the absorption characteristics of the specific isotope in the gas to be measured. Different gas isotopes have different absorption rates for light of different wavelengths, so choosing the correct wavelength is also very important for accurate measurement.

[0075] S502: The laser switching module switches between the light beam of the first wavelength and the light beam of the second wavelength based on the control signal, and selects one light beam for output.

[0076] Among them, the control signal is sent multiple times by the spectrum scanning and data acquisition system according to a preset program.

[0077] When a specific measurement task needs to be performed, the spectrum scanning and data acquisition system sends a control signal to the laser switching module. This control signal contains information about which wavelength should be used. If the control signal indicates the use of the first wavelength, the laser switching module selects the first wavelength beam provided by laser one and directs it to the cavity; if the control signal indicates the use of the second wavelength, the laser switching module selects the second wavelength beam provided by laser two and directs it to the cavity. The laser switching module can be implemented through a variety of technologies, such as EOM, optical switch, etc.

[0078] S503, the cavity receives the light beam output by the laser switching module, and after multiple reflections, the light beam interacts with the gas to be measured filled in the cavity, and outputs the light beam after the interaction.

[0079] The cavity is filled with the gas to be measured. In a feasible implementation, the cavity is an optical resonant cavity composed of a pair of high-reflection mirrors with a reflectivity greater than 99.99%. When the light beam is reflected multiple times in the cavity, it will interact with the gas molecules to be measured by absorption, scattering, etc. Different gas isotopes have different absorption characteristics for light of a specific wavelength, so information about the gas composition can be obtained by analyzing the changes in the light beam. After multiple reflections and interactions with the gas to be measured, the interaction time between the light beam and the gas molecules is significantly increased, the intensity of the absorption signal is enhanced, and the detection sensitivity of the gas to be measured is improved.

[0080] S504. The photoelectric detection system receives the light beam after the interaction, converts the optical signal corresponding to the light beam after the interaction into an electrical signal, and outputs the electrical signal.

[0081] In one achievable embodiment, the photoelectric detection system includes a high-sensitivity photodetector (such as a photodiode, a photomultiplier tube or a CCD / CMOS sensor) and a signal amplification and processing module; the signal amplification and processing module includes an amplifier and an analog-to-digital conversion.

[0082] The photodetector is connected to the cavity and the amplifier and is used to convert the received optical signal into an initial electrical signal.

[0083] The amplifier is connected to the photodetector and the analog-to-digital converter to amplify the initial electrical signal.

[0084] The analog-to-digital converter is connected to the amplifier and the spectrum scanning and data acquisition system, and is used to convert the amplified initial electrical signal into a digital signal for output.

[0085] The photoelectric detection system is an indispensable part of the dual laser gas isotope abundance measurement device. It lays the foundation for subsequent precise measurements by converting complex optical signals into easy-to-process electrical signals.

[0086] S505 , the spectrum scanning and data acquisition system receives the electrical signal, scans the electrical signal, and measures the spectrum data corresponding to the electrical signal.

[0087] Optionally, after the spectrum scanning and data acquisition system receives the electrical signal, scans the electrical signal, and measures the spectrum data corresponding to the electrical signal, the method further includes: Based on the spectral data corresponding to the electrical signal, the isotope abundance of the gas to be measured is calculated using the following formula: ; In the above formula, Ratio is the isotopic abundance of the gas to be measured, X1 is the concentration of isotope one of the gas to be measured, X2 is the concentration of isotope two of the gas to be measured, Area1 is the area of ​​the absorption line of isotope one of the gas to be measured, and Area2 is the area of ​​the absorption line of isotope two of the gas to be measured; S1(T) is the transition intensity of the absorption line of isotope one of the gas to be measured, and S2(T) is the transition intensity of the absorption line of isotope two of the gas to be measured; the Area1 and the Area2 are obtained based on the spectral data of the gas to be measured; the S1(T) and the S2(T) are obtained based on the database.

[0088] Optionally, after receiving the light beam after the interaction, converting the optical signal corresponding to the light beam after the interaction into an electrical signal, and outputting the electrical signal, the method further includes: The electronic automatic feedback control system receives the electrical signal, generates an error signal by demodulating the electrical signal, and adjusts the laser one and the laser two based on the error signal, so that the frequency of the light beam of the first wavelength and the frequency of the light beam of the second wavelength both match the longitudinal mode frequency of the cavity.

[0089] Optionally, before switching between the light beam of the first wavelength and the light beam of the second wavelength based on the control signal and selecting one light beam for output, the method further includes: The beam combiner combines the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam, and transmits the composite light beam to the laser switching module.

[0090] Optionally, after the beam combiner combines the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam and transmits the composite light beam to the laser switching module, the method further includes: The laser switching module modulates the composite light beam based on the control signal; the modulation includes adjusting the phase or polarization state of the light beam.

[0091] According to the beam characteristics of the modulated composite light beam, a light beam with a target wavelength is separated from the composite light beam as an output; the light beam with the target wavelength is one of the light beam with the first wavelength and the light beam with the second wavelength.

[0092] The dual-laser gas isotope abundance measurement method provided in the embodiment of the present application uses two lasers to achieve simultaneous measurement of two transition spectral lines, and can control the laser switching module to select a light beam of a specific frequency to enter the cavity as needed. Compared with the current method of using one laser to measure isotope abundance, which requires time-sharing measurement of spectra of different isotopes of isotope molecules and faces the problem that the accuracy of the pressure of the gas to be measured is not high enough, this method can eliminate the influence of system errors such as the pressure and temperature drift of the gas to be measured, and the nonlinearity of the detector and acquisition card, thereby significantly improving the spectral measurement accuracy of different isotopes of the gas molecules to be measured.

[0093] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same and similar parts between the various embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the method embodiment, since it is basically similar to the device embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the device embodiment. The device embodiment described above is only schematic, in which the unit described as a separate component may or may not be physically separated, and the component prompted as a unit may or may not be a physical unit, that is, it may be located in one place, or it may be distributed on multiple network units. Select some or all of the modules according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative work.

[0094] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A dual-laser gas isotope abundance measurement device, characterized in that: The device comprises a first laser, a second laser, a laser switching module, a cavity, a photoelectric detection system and a spectrum scanning and data acquisition system; The laser 1 is connected to the laser switching module and is used to provide a light beam of a first wavelength; The second laser is connected to the laser switching module and is used to provide a light beam of a second wavelength; The laser switching module is connected to the laser 1 and the laser 2, and is also connected to the cavity and the spectrum scanning and data acquisition system, and is used to switch between the light beam of the first wavelength and the light beam of the second wavelength based on a control signal, and select one light beam for output; the control signal is sent multiple times by the spectrum scanning and data acquisition system according to a preset program; The cavity is connected to the laser switching module and the photoelectric detection system, and is used to receive the light beam output by the laser switching module. Through multiple reflections, the light beam interacts with the gas to be measured filled in the cavity, and outputs the light beam after interaction; The photoelectric detection system is connected to the cavity and the spectrum scanning and data acquisition system, and is used to receive the light beam after the interaction, convert the light signal corresponding to the light beam after the interaction into an electrical signal, and output the electrical signal; The spectrum scanning and data acquisition system is connected to the photoelectric detection system and the laser switching module, and is used to receive the electrical signal, scan the electrical signal, and measure the spectrum data corresponding to the electrical signal.

2. The device according to claim 1, characterized in that The spectrum scanning and data acquisition system is also used for: Based on the spectral data corresponding to the electrical signal, the isotopic abundance of the gas to be measured is calculated: ； In the above formula, Ratio is the isotopic abundance of the gas to be measured, X1 is the concentration of isotope one of the gas to be measured, X2 is the concentration of isotope two of the gas to be measured, Area1 is the area of ​​the absorption line of isotope one of the gas to be measured, and Area2 is the area of ​​the absorption line of isotope two of the gas to be measured; S1(T) is the transition intensity of the absorption line of isotope one of the gas to be measured, and S2(T) is the transition intensity of the absorption line of isotope two of the gas to be measured; the Area1 and the Area2 are obtained based on the spectral data of the gas to be measured; the S1(T) and the S2(T) are obtained based on the database.

3. The device according to claim 1, characterized in that The device also includes: an electronic automatic feedback control system; The electronic automatic feedback control system is connected to the photoelectric detection system, the laser one and the laser two, and is used to receive the electrical signal, generate an error signal by demodulating the electrical signal, and adjust the laser one and the laser two based on the error signal, so that the frequency of the first wavelength light beam and the frequency of the second wavelength light beam both match the longitudinal mode frequency of the cavity.

4. The device according to claim 1, characterized in that The device also includes: a beam combiner; The beam combiner is connected to the laser 1 and the laser 2, and is also connected to the laser switching module, and is used to combine the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam, and emit the composite light beam to the laser switching module.

5. The device according to claim 4, characterized in that The laser switching module is also used for: Based on the control signal, modulating the composite light beam; the modulation includes adjusting the phase or polarization state of the light beam; According to the beam characteristics of the modulated composite light beam, a light beam of a target wavelength is separated from the composite light beam as an output; the light beam of the target wavelength is one of the light beam of the first wavelength and the light beam of the second wavelength.

6. A dual-laser gas isotope abundance measurement method, characterized in that: The method is applied to the dual-laser gas isotope abundance measurement device according to claim 1, and the method comprises: The laser 1 provides a light beam of a first wavelength; The second laser provides a light beam of a second wavelength; The laser switching module switches between the light beam of the first wavelength and the light beam of the second wavelength based on the control signal, and selects one light beam for output; the control signal is sent by the spectrum scanning and data acquisition system according to a preset program; The cavity receives the light beam output by the laser switching module, and the light beam interacts with the gas to be measured filled in the cavity through multiple reflections, and outputs the light beam after the interaction; The photoelectric detection system receives the light beam output by the cavity, receives the light beam after interaction, converts the light signal corresponding to the light beam after interaction into an electrical signal, and outputs the electrical signal; The spectrum scanning and data acquisition system receives the electrical signal, scans the electrical signal, and measures the spectrum data corresponding to the electrical signal.

7. The method according to claim 6, characterized in that After the spectrum scanning and data acquisition system receives the electrical signal, scans the electrical signal, and measures the spectrum data corresponding to the electrical signal, the method further includes: Based on the spectral data corresponding to the electrical signal, the isotopic abundance of the gas to be measured is calculated: ； In the above formula, Ratio is the isotopic abundance of the gas to be measured, X1 is the concentration of isotope one of the gas to be measured, X2 is the concentration of isotope two of the gas to be measured, Area1 is the area of ​​the absorption line of isotope one of the gas to be measured, and Area2 is the area of ​​the absorption line of isotope two of the gas to be measured; S1(T) is the transition intensity of the absorption line of isotope one of the gas to be measured, and S2(T) is the transition intensity of the absorption line of isotope two of the gas to be measured; the Area1 and the Area2 are obtained based on the spectral data of the gas to be measured; the S1(T) and the S2(T) are obtained based on the database.

8. The method according to claim 6, characterized in that After receiving the light beam after the interaction, converting the light signal corresponding to the light beam after the interaction into an electrical signal, and outputting the electrical signal, the method further includes: An electronic automatic feedback control system receives the electrical signal, generates an error signal by demodulating the electrical signal, and adjusts the laser one and the laser two based on the error signal, so that the frequency of the first wavelength light beam and the frequency of the second wavelength light beam both match the longitudinal mode frequency of the cavity.

9. The method according to claim 6, characterized in that Before switching between the light beam of the first wavelength and the light beam of the second wavelength based on the control signal and selecting one light beam for output, the method further includes: The beam combiner combines the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam, and transmits the composite light beam to the laser switching module.

10. The method according to claim 9, characterized in that After the beam combiner combines the light beam of the first wavelength and the light beam of the second wavelength into a composite light beam and transmits the composite light beam to the laser switching module, the method further includes: The laser switching module modulates the composite light beam based on the control signal; the modulation includes adjusting the phase or polarization state of the light beam; According to the beam characteristics of the modulated composite light beam, a light beam of a target wavelength is separated from the composite light beam as an output; the light beam of the target wavelength is one of the light beam of the first wavelength and the light beam of the second wavelength.

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