Laser heterodyne atmospheric composition concentration detection device based on optoelectronic chip

Abstract

A kind of laser heterodyne atmospheric composition concentration detection device based on optoelectronic chip, including collimating module, sun tracker, optoelectronic chip module, signal processing module, data acquisition and analysis module.The present application adopts optoelectronic chip to carry optical path and constructs laser heterodyne atmospheric composition concentration detection device, adopts optoelectronic chip to carry system optical path, increases the stability and anti-interference ability of system, so that system can adapt to more use environment;At the same time, optoelectronic chip is easy to integrate, different local oscillator light source can be used to realize the simultaneous monitoring of various atmospheric composition column concentration;Using optoelectronic chip module can greatly reduce the volume of system, realize the miniaturization of system, has wide application prospect in the field of climate research, environmental monitoring and atmospheric chemistry research, and explores for subsequent further popularization and application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser radar, in particular to a laser heterodyne atmospheric composition concentration detection device based on an optoelectronic chip. BACKGROUND

[0002] Greenhouse gases in the atmosphere are an important barrier to life on Earth, and play an important role in climate change and regulating the temperature of the Earth's atmosphere. The increase in human production and social activities has led to an increase in the concentration of greenhouse gases such as CO2, CH4, NO2, etc. year by year, causing the global temperature to rise. The greenhouse effect is not only closely related to the concentration of greenhouse gases in the atmosphere, but also related to the vertical profile distribution. Therefore, long-term continuous high-precision monitoring of the concentration of greenhouse gases and long-term observation of the vertical profile of atmospheric greenhouse gases are of great significance for studying global carbon emissions, carbon trading, greenhouse gas concentration trends and responding to climate change.

[0003] Atmospheric composition detection is divided into active and passive detection methods. Active detection directly uses a laser radar to emit laser and receive reflected or scattered light absorbed by atmospheric composition to detect atmospheric composition, which can achieve continuous monitoring during the day and at night, but the active detection method has high requirements for the laser. Currently, instruments that can be used for passive atmospheric composition measurement mainly include microwave radiometers, spatial heterodyne spectrometers, Fourier transform spectrometers, etc. The precision of the solar radiometer is limited. The spatial heterodyne spectrometer can synchronously collect multiple channels with high spectral resolution and a large spectral detection range, but it is very dependent on precise gratings and CCDs, and the detection band is in the visible and near-infrared band. The Fourier transform spectrometer, which is widely used in passive detection, has high spectral resolution and wide spectral coverage, but the system is large in size, the detection precision is proportional to the size, and the construction and maintenance costs are high. The laser heterodyne spectrometer has high spectral resolution, high spatial resolution, and weak light signal detection due to its frequency coherent detection principle. However, like all passive observation methods, the conventional laser heterodyne spectrometer system is still relatively large in size, and the system stability and anti-interference ability are insufficient.

[0004] In recent years, silicon-based optoelectronic chips have developed well, and they have the advantages of facilitating miniaturized system structure and relatively more stable characteristics, providing a feasible path for the miniaturization of laser heterodyne detection instruments. Silicon-based optoelectronic chips have high bandwidth, high speed, high integration, strong anti-interference ability, and are compatible with CMOS technology. The optical electronic chip-mounted system optical path part can meet the needs of miniaturization and stability.

[0005] However, at present, the optoelectronic chip and the laser heterodyne spectrometer system have not been combined. On the one hand, the optoelectronic chip can be used to carry the system, which can utilize the advantage of easy integration, can be connected in parallel with multiple systems, can realize the simultaneous monitoring of multiple gases, and has high signal-to-noise ratio; on the other hand, the combination of the laser heterodyne spectrometer system has the advantages of high spectral resolution, high detection accuracy, and the advantages of the optoelectronic chip, such as good stability, strong anti-interference ability, and small volume, and thus a continuous monitoring micro high-precision concentration detection device of atmospheric components based on the laser heterodyne spectrometer system of the optoelectronic chip is developed.

[0006] The heterodyne detection system used in CN114544494A is connected by optical fibers. Changes in external temperature and stress and overlong optical fibers can affect the polarization state of light in the link, making the system measurement unstable and affecting the measurement accuracy and service life. SUMMARY

[0007] The present application aims to solve the problems of large volume, weak anti-interference ability and poor stability of the existing laser heterodyne spectrometer system. The present application proposes a laser heterodyne atmospheric component concentration detection device based on an optoelectronic chip. The device combines the advantages of optoelectronic chips and passive wide-spectrum detection, and meets the needs of high precision, miniaturization, multi-channel and continuous observation and detection of atmospheric components.

[0008] The basic principle of the present application is based on the principle of coherent detection. The signal light received by the sun tracker is frequency-mixed with the local oscillator laser with a narrow linewidth, so as to realize the frequency down-conversion from optical frequency to radio frequency. The spectral information containing atmospheric molecular absorption information is obtained by processing the radio frequency signal. The concentration of atmospheric components such as greenhouse gases or pollutant gases can be obtained by inverting the collected signal.

[0009] The technical solution of the present application is as follows:

[0010] A laser heterodyne atmospheric component concentration detection device based on an optoelectronic chip, characterized in that it comprises a collimation module, a sun tracker, an optoelectronic chip module, a signal processing module, and a data acquisition and processing module.

[0011] Sunlight enters the sun tracker through the collimation module, so as to receive the sunlight beam entering the system;

[0012] The sunlight received by the sun tracker is processed by the optoelectronic chip module to generate a heterodyne signal. The generated signal is modulated by the signal processing module and then enters the data acquisition and processing module. The signal is collected and analyzed to obtain information of atmospheric components.

[0013] The photoelectron chip module comprises directional coupler one, thermal-optical switch, 2*2 coupler, balanced detector, tunable laser module, directional coupler two, photoelectric detector two and photoelectric detector three connected in sequence.

[0014] The directional coupler one divides the sunlight received by the sun tracker into two paths: one path is connected with the input end of the data acquisition and processing module through the photoelectric detector two; the other path is output to the thermal-optical switch, and after modulation, is connected with the input end of the 2*2 coupler.

[0015] The tunable laser module can be adjusted in temperature or current to realize the tuning of laser frequency and control the sweep frequency, and the output laser enters the directional coupler two and is divided into two paths: one path is connected with the input end of the data acquisition and processing module through the photoelectric detector three; the other path is connected with the input end of the 2*2 coupler.

[0016] The two light beams output by the thermal-optical switch and the directional coupler two are coupled into the 2*2 coupler to realize beat frequency coherence, and beat frequency signals are output to the balanced detector.

[0017] The signal processing module comprises transimpedance amplifier, biasing device, radio frequency amplification module, band pass filter, square law detector and phase-locked amplifier connected in sequence.

[0018] The transimpedance amplifier receives the signal output by the balanced detector and amplifies the signal, and the biasing device separates the beat frequency signal, the radio frequency amplification module amplifies the radio frequency signal separated by the biasing device, and the band pass filter reduces the radio frequency noise and controls the spectral resolution, the filtered radio frequency signal is converted into low frequency voltage signal with modulation frequency as characteristic frequency by the square law detector, and the phase-locked amplifier demodulates the low frequency voltage signal, and the demodulated signal enters the data acquisition and processing module, acquires the signal and analyzes to obtain the information of atmospheric composition, the modulation frequency of the thermal-optical switch is the same as the demodulation frequency of the phase-locked amplifier, and the phase is fixed.

[0019] The thermal-optical switch is a switch or a device capable of low frequency optical switch modulation.

[0020] The tunable laser module is continuously tunable in wavelength, and the line width is narrow to MHz level, and according to the actual need of measuring atmospheric composition, one or more tunable laser modules are divided to detect one or more paths at the same time.

[0021] By beating the signal light containing atmospheric composition absorption information with the local laser, frequency down conversion from optical frequency to radio frequency is realized, the local laser module is swept, and thus the spectral signal containing atmospheric composition absorption is obtained, and then the concentration of the atmospheric composition is inversely calculated.

[0022] The present application has the advantages that:

[0023] Compared with the system in the application CN114544494A, the present application utilizes the advantages of good stability and strong anti-interference capability of the optoelectronic chip, integrates the system, uniformly distributes the temperature and stress in the optical path, improves the stability of the system, and thus improves the measurement precision of the system, and also can realize observation in various environments and has high signal-to-noise ratio.

[0024] The present application utilizes the advantages of easy integration and extremely small volume of the optoelectronic chip, and more conveniently connects multiple local light sources corresponding to different atmospheric composition absorption peaks in one system, so that simultaneous monitoring of multiple gases can be realized.

[0025] The present application utilizes the principle of the laser heterodyne spectrometer system, has the advantages of high spectral resolution, high spectral resolution, high spatial resolution, weak light signal detection, high signal-to-noise ratio, and is suitable for development as a long-term miniaturized continuous observation device.

[0026] The present application combines the advantages of the optoelectronic chip and passive detection, and can realize high-precision measurement of multiple atmospheric compositions simultaneously. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a structural block diagram of the laser heterodyne atmospheric composition concentration detection device based on the optoelectronic chip of the present application.

[0028] Figure 2 It is a structural block diagram of the optoelectronic chip module of the present application.

[0029] Figure 3 It is a structural block diagram of the signal processing module of the present application.

[0030] In the figure: 1 - collimation module, 2 - solar tracker, 3 - optoelectronic chip module, 4 - signal processing module, 5 - data acquisition and analysis module, 3-1 - directional coupler one, 3-2 - thermal optical switch, 3-3 - 2x2 coupler, 3-4 - balanced detector, 3-5 - tunable laser module, 3-6 - directional coupler two, 3-7 - photodetector two, 3-8 - photodetector three, 4-1 - transimpedance amplifier, 4-2 - biasing device, 4-3 - radio frequency amplification module, 4-4 - band pass filter, 4-5 - square law detector, 4-6 - phase lock amplifier. DETAILED DESCRIPTION

[0031] The application will be further described in connection with examples and drawings, but the application should not be limited by the examples and drawings.

[0032] Referring to Figure 1 , Figure 1 is a structural block diagram of the photoelectronic chip-based laser heterodyne atmospheric composition concentration detection device of the application, and as shown in the diagram, the photoelectronic chip-based laser heterodyne atmospheric composition concentration detection device of the application comprises a collimation module 1, a sun tracker 2, a photoelectronic chip module 3, a signal processing module 4, and a data acquisition and processing module 5.

[0033] Sunlight enters the sun tracker 2 through the collimation module 1, thereby receiving a sunlight beam into the system.

[0034] The sunlight received by the sun tracker 2 is processed by the photoelectronic chip module 3 to generate a heterodyne signal, the generated signal is modulated by the signal processing module 4 and then enters the data acquisition and processing module 5, the signal is acquired and analyzed to obtain information of atmospheric composition.

[0035] Referring to Figure 2 , Figure 2 is a structural block diagram of the photoelectronic chip module of the application, and as shown in the diagram, the photoelectronic chip module 3 comprises a directional coupler 1 3-1, a thermo-optic switch 3-2, a 2×2 coupler 3-3, a balanced detector 3-4, a tunable laser module 3-5, a directional coupler 2 3-6, a photodetector 2 3-7, and a photodetector 3 3-8 connected in sequence.

[0036] The directional coupler 1 3-1 divides the sunlight received by the sun tracker 2 into two paths: one path is connected to the input end of the data acquisition and processing module 5 through the photodetector 2 3-7; the other path is output to the thermo-optic switch 3-2 and connected to the input end of the 2×2 coupler 3-3 after modulation.

[0037] The tunable laser module 3-5 can be adjusted in temperature or current to realize tuning of laser frequency and control of frequency sweeping, and output laser enters the directional coupler 2 3-6 and is divided into two paths: one path is connected to the input end of the data acquisition and processing module 5 through the photodetector 3 3-8; the other path is connected to the input end of the 2×2 coupler 3-3.

[0038] The two light beams output by the thermo-optic switch 3-2 and the directional coupler 2 3-6 are coupled into the 2×2 coupler 3-3 to perform beat frequency coherence, and beat frequency signals are output to the balanced detector 3-4.

[0039] Referring to Figure 3, Figure 3 The signal processing module 4 of the present application is a structural block diagram, as shown in the figure, the signal processing module 4 of the present application comprises a transimpedance amplifier 4-1, a biasing device 4-2, a radio frequency amplification module 4-3, a band-pass filter 4-4, a square law detector 4-5 and a phase-locked amplifier 4-6 connected in sequence;

[0040] The transimpedance amplifier 4-1 receives the signal output by the balanced detector 3-4 and amplifies it, and then separates the difference frequency signal through the biasing device 4-2, the radio frequency amplification module 4-3 amplifies the radio frequency signal separated by the biasing device 4-2, reduces the radio frequency noise and controls the spectral resolution through the band-pass filter 4-4, the filtered radio frequency signal is converted into a low frequency voltage signal with a modulation frequency as a characteristic frequency through the square law detector 4-5, and the phase-locked amplifier 4-6 demodulates the low frequency voltage signal, and the demodulated signal enters the data acquisition and processing module 5, acquires the signal and analyzes it to obtain the information of the atmospheric composition, the modulation frequency of the thermo-optic switch 3-2 is the same as the demodulation frequency of the phase-locked amplifier 4-6, and the phase is fixed.

[0041] The thermo-optic switch 3-2 is a switch or a device capable of low frequency optical switch modulation.

[0042] The tunable laser module 3-5 has a continuous wavelength and a narrow linewidth of the order of MHz, and according to the actual need of measuring atmospheric composition, one or more tunable laser modules are divided to detect simultaneously.

[0043] The signal light containing the absorption information of atmospheric composition is beat with the local laser to realize the frequency down-conversion from optical frequency to radio frequency, the local laser module is swept to obtain the spectrum signal containing the absorption of atmospheric composition, and then the concentration of atmospheric composition is inversely calculated.

[0044] The connection relationship of the above-mentioned components is as follows:

[0045] Sunlight enters the sun tracker 2 through the collimation module 1 to receive the sunlight beam into the system. The sunlight received by the sun tracker 2 is processed by the optoelectronic chip module 3 to generate a heterodyne signal. The generated signal is modulated by the signal processing module 4 and enters the data acquisition and processing module 5 to collect and analyze the signal to obtain information of atmospheric composition. The directional coupler 3-1 divides the sunlight received by the sun tracker 2 into two paths: one path passes through the photodetector 3-7 to monitor the energy jitter of the received sunlight signal in real time, and the other path is output to the thermal light switch 3-2 and modulated to be coupled into the 2x2 coupler 3-3 together with the main light beam output by the directional coupler 2 3-6. The tunable laser module 3-5 can be adjusted in temperature or current to realize the tuning of laser frequency and control the sweep frequency. The output laser enters the directional coupler 2 3-6 and is divided into two paths: one path enters the data acquisition and processing module 5 for control collection through the photodetector 3-8, and the other path is the main light beam coupled into the 2x2 coupler 3-3. The balanced detector 3-4 detects the beat frequency signal of the 2x2 coupler 3-3. The transimpedance amplifier 4-1 receives the signal output by the balanced detector 3-4 and amplifies it, and the bias tee 4-2 separates the difference frequency signal. The RF amplifier module 4-3 amplifies the RF signal and reduces the RF noise through the bandpass filter 4-4 to control the spectral resolution. The filtered RF signal is converted into a low-frequency voltage signal with a modulation frequency as the characteristic frequency by the square-law detector 4-5. The phase-locked amplifier 4-6 demodulates the low-frequency voltage signal, and the demodulated signal enters the data acquisition and processing module 5 to collect and analyze the signal to obtain information of atmospheric composition. The modulation frequency of the thermal light switch 3-2 is the same as the demodulation frequency of the phase-locked amplifier 4-6, and the phase is fixed. The signals generated by the photodetector 3-7 and the phase-locked amplifier 4-6 are synchronously collected by the data acquisition and processing module 5.

[0046] The present application combines the optoelectronic chip module 3 with the laser heterodyne spectrometer, utilizes the small size, strong anti-interference ability, high stability and easy integration of the optoelectronic chip technology, can improve the integration of the heterodyne detection system, and realize the simultaneous monitoring of multiple atmospheric composition concentrations with high signal-to-noise ratio. At the same time, the laser heterodyne spectrometer system has high spectral resolution and high signal-to-noise ratio, which can be developed into a long-term miniaturized continuous observation device, and can realize the advantages of simultaneous high-precision monitoring of multiple gases. The system has broad application prospects in the fields of climate research, environmental monitoring and atmospheric environment research, and can be further explored for multi-scene popularization and application.

[0047] In the embodiment,

[0048] The sunlight is collimated by the collimating module 1 and then enters the sun tracker 2 to prevent dispersion and other phenomena.

[0049] The thermo-optic switch 3-2 can realize low-frequency modulation.

[0050] The laser in the tunable laser module 3-5 is a DFB distributed feedback semiconductor laser with a center wavelength of 1572 nm, covering the absorption line of CO2.

[0051] The photoelectric detector two 3-7 and the photoelectric detector three 3-8 are InGaAs PIN photoelectric detectors with an electronic bandwidth of 1.2 GHz. The electronic bandwidth of the balanced detector 3-4 is 1 GHz. The bandwidth of the bandpass filter 4-4 is tens of MHz to hundreds of MHz.

[0052] The process of CO2 detection using the above devices and structures is as follows:

[0053] The sunlight enters the sun tracker 2 through the collimating module 1 to receive the sunlight beam entering the system. The directional coupler one 3-1 divides the sunlight received by the sun tracker 2 into two paths: one path passes through the photoelectric detector two 3-7 to monitor the energy jitter of the received sunlight signal in real time, and the other path is output to the thermo-optic switch 3-2 after modulation and coupled into the 2×2 coupler 3-3 together with the main beam output by the directional coupler two 3-6. The tunable laser module 3-5 can adjust the temperature or current to realize the tuning of the laser frequency and control the sweep, and the output laser enters the directional coupler two 3-6 and is divided into two paths: one path enters the data acquisition and processing module 5 for control and acquisition through the photoelectric detector three 3-8, and the other path is coupled into the 2×2 coupler 3-3 as the main beam. The balanced detector 3-4 detects the beat frequency signal of the coupler 3-3. The transimpedance amplifier 4-1 receives the signal output by the balanced detector 3-4 and amplifies it, and the bias tee 4-2 separates the difference frequency signal, the RF amplifier module 4-3 amplifies the RF signal and reduces the RF noise through the bandpass filter 4-4 to control the spectral resolution, and the filtered RF signal is converted into a low-frequency voltage signal with a modulation frequency as the characteristic frequency by the square-law detector 4-5. The low-frequency voltage signal is demodulated by the lock-in amplifier 4-6, and the demodulated signal enters the data acquisition and processing module 5, which acquires the signal and analyzes it to obtain information about the atmospheric composition. The tunable laser module 3-5 controls the distributed feedback semiconductor laser to sweep, and the spectral information of the CO2 absorption in the sweep range can be obtained, and the column concentration information of CO2 can be obtained after data processing.

Claims

1. A photoelectron chip-based laser heterodyne atmospheric composition concentration detection device, comprising a collimation module (1), a sun tracker (2) and a data acquisition and processing module (5), characterized in that, It also includes optoelectronic chip module (3) and signal processing module (4); Sunlight enters the solar tracker (2) through the collimation module (1), the sunlight received by the solar tracker (2) is processed by the optoelectronic chip module (3) to generate a heterodyne signal, which is modulated by the signal processing module (4), and the signal is collected and analyzed by the data acquisition and processing module (5) to obtain information of atmospheric composition; The optoelectronic chip module (3) mixes the received sunlight with a narrow linewidth local laser to realize frequency down-conversion from optical frequency to radio frequency, and outputs a current signal to the signal processing module (4); The signal processing module (4) converts the received current signal into a voltage signal, and then outputs it to the data acquisition and processing module (5) after isolation, amplification, filtering and phase-locked amplification; The optoelectronic chip module (3) includes directional coupler one (3-1), thermal optical switch (3-2), 2×2 coupler (3-3), balanced detector (3-4), tunable laser module (3-5), directional coupler two (3-6), photodetector two (3-7), photodetector three (3-8) connected in sequence; The directional coupler one (3-1) divides the sunlight received by the solar tracker (2) into two paths: one path is connected to the input end of the data acquisition and processing module (5) through the photodetector two (3-7); the other path is output to the thermal optical switch (3-2) and connected to the input end of the 2×2 coupler (3-3) after modulation; The tunable laser module (3-5) realizes laser frequency tuning and controls frequency sweeping by adjusting temperature or current, and outputs laser into the directional coupler two (3-6) and divides it into two paths: one path is connected to the input end of the data acquisition and processing module (5) through the photodetector three (3-8); the other path is connected to the input end of the 2×2 coupler (3-3); The thermal optical switch (3-2) and the two light beams output by the directional coupler two (3-6) are coupled into the 2×2 coupler (3-3) to realize frequency mixing and coherence, and output the frequency mixing signal to the balanced detector (3-4).

2. The optoelectronic chip-based laser heterodyne atmospheric composition concentration sounding apparatus according to claim 1, characterized in that, The signal processing module (4) includes transimpedance amplifier (4-1), biasing device (4-2), radio frequency amplification module (4-3), band-pass filter (4-4), square-law detector (4-5), phase-locked amplifier (4-6) connected in sequence; The transimpedance amplifier (4-1) receives the signal output by the balanced detector (3-4) and amplifies it, and then separates the difference frequency signal through the biasing device (4-2), the radio frequency amplification module (4-3) amplifies the radio frequency signal separated by the biasing device (4-2), and then reduces the radio frequency noise and controls the spectral resolution through the band-pass filter (4-4), the filtered radio frequency signal is converted into a low-frequency voltage signal with a modulation frequency as the characteristic frequency through the square-law detector (4-5), the low-frequency voltage signal is demodulated by the lock-in amplifier (4-6), and the demodulated signal enters the data acquisition and processing module (5), acquires the signal and analyzes it to obtain the information of the atmospheric composition, the modulation frequency of the thermo-optic switch (3-2) is the same as the demodulation frequency of the lock-in amplifier (4-6), and the phase is fixed. 3.The optoelectronic chip-based laser heterodyne atmospheric composition concentration sounding device according to claim 1, characterized in that, The thermo-optic switch (3-2) is a device capable of low-frequency optical switch modulation. 4.The optoelectronic chip-based laser heterodyne atmospheric composition concentration sounding device according to claim 1, wherein, The tunable laser module (3-5) is continuously tunable in wavelength and has a narrow linewidth of the order of MHz, and according to the actual need of measuring atmospheric composition, one or more tunable laser modules are divided, and one or more paths are simultaneously detected.

5. The optoelectronic chip-based laser heterodyne atmospheric composition concentration sounding apparatus according to any one of claims 1-4, characterized in that, By beating the signal light containing the absorption information of the atmospheric composition with the local oscillator laser, the local oscillator laser module is swept, so that the spectral signal containing the absorption of the atmospheric composition is obtained, and then the concentration of the atmospheric composition is inverted.

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