CN-121978018-A - Gas component parameter calculation method and system based on single optical frequency comb photo-thermal spectrum

CN121978018ACN 121978018 ACN121978018 ACN 121978018ACN-121978018-A

Abstract

The application discloses a gas component parameter calculation method and system based on single optical frequency comb photo-thermal spectrum, and belongs to the technical field of laser spectrum gas sensing. The method comprises the steps of obtaining characteristic parameters of a Mach-Zehnder interference device and frequency domain electric information of signal light, wherein the signal light is generated by the Mach-Zehnder interference device, obtaining detection light frequency domain electric information which is periodically modulated after absorption and coupling of detection light and the signal light through gas to be detected, calculating down-conversion factors according to the characteristic parameters of the Mach-Zehnder interference device, carrying out inversion processing on the frequency domain electric information and the detection light frequency domain electric information of the signal light according to the down-conversion factors, and obtaining gas component parameters according to the gas light heat spectrum information. The application can directly utilize the moving speed of the movable arm reflecting mirror group in the Mach-Zehnder interference device to calculate the down conversion factor, so that the calculation process of the gas component parameters is simple, convenient and quick.

Inventors

WANG QIANG
LIAO YUKUN
HU MAI
Hu Mengpeng
SUN PANPAN
ZHANG DONGQING

Assignees

中国科学院合肥物质科学研究院

Dates

Publication Date: 20260505
Application Date: 20260210

Claims (10)

1. A gas component parameter calculation method based on single optical frequency comb photo-thermal spectrum is characterized by comprising the following steps: acquiring characteristic parameters of the Mach-Zehnder interference device and frequency domain electrical information of signal light, wherein the signal light is generated by the Mach-Zehnder interference device; acquiring detection light frequency domain electrical information of periodically modulated detection light and signal light after absorption coupling of the gas to be detected; calculating a down-conversion factor according to the characteristic parameters of the Mach-Zehnder interference device; Inversion processing is carried out on the frequency domain electrical information of the signal light and the frequency domain electrical information of the detection light according to the down-conversion factor, so that the gas photothermal spectrum information is obtained; and obtaining gas component parameters according to the gas photothermal spectrum information.
2. The method for calculating gas composition parameters based on single optical frequency comb photo-thermal spectrum according to claim 1, wherein the frequency domain electrical information and the detection light frequency domain electrical information of the signal light are obtained by performing fourier transform on the time domain electrical information obtained by detecting the two detectors with the same model And/or the characteristic parameters of the Mach-Zehnder interference device comprise the moving speed of a movable arm reflecting mirror group in the Mach-Zehnder interference device and the refractive index of the environment where the Mach-Zehnder interference device is located; And/or, the calculation formula is as follows: a 0 =2nu/c Where a 0 is a down-conversion factor, u is a moving speed of the movable arm mirror group in the mach-zehnder interferometer, n is a refractive index of an environment where the mach-zehnder interferometer is located, and c is a light velocity in vacuum.
3. The method for calculating the gas component parameters based on the single optical frequency comb photo-thermal spectrum according to claim 1, wherein the inversion processing is performed on the frequency domain electrical information of the signal light and the frequency domain electrical information of the probe light according to the down-conversion factor, and the gas photo-thermal spectrum information comprises: taking ratio information of frequency domain electric information of the signal light and frequency domain electric information of the detection light; and multiplying the abscissa of the obtained ratio information by the inverse of the down-conversion factor, and obtaining gas photothermal spectrum information.
4. A method for calculating gas composition parameters based on single optical frequency comb photothermal spectroscopy according to claim 3, wherein the expression of the gas photothermal spectroscopy information is as follows: Wherein K p is an intensity ratio correction coefficient, For the normalized absorption line function, a is the gas peak absorption coefficient, Is the frequency domain electrical information of the signal light, For the electrical information in the probe light frequency domain subjected to periodic modulation, v p is the respective longitudinal mode frequency of the optical frequency comb, and v 0 is the molecular absorption line center frequency.
5. The method for calculating gas composition parameters based on single optical frequency comb photo-thermal spectrum according to claim 1, wherein the frequency domain electrical information of the signal light The expression formula of (2) is as follows: Wherein, R s,p is the responsivity of the detector for detecting the signal light to the radio frequency longitudinal mode of the signal light sequence number P, and P p is the P-th optical frequency longitudinal mode power of the signal light.
6. The method for calculating gas composition parameters based on single optical frequency comb photo-thermal spectrum according to claim 1, wherein the probe light frequency domain electrical information The expression formula of (2) is as follows: Wherein R r,p is the responsivity of the detector for detecting the detection light to the radio frequency longitudinal mode with the periodical detection light sequence number P, P p is the P-th optical frequency longitudinal mode power of the signal light, For the normalized absorption line function, a is the gas peak absorption coefficient.
7. The method for calculating the gas component parameters based on the single optical frequency comb photothermal spectroscopy according to claim 1, wherein the obtaining the gas component parameters according to the gas photothermal spectroscopy information comprises: comparing the gas photothermal spectrum information with a gas molecular parameter database, and calibrating gas molecular parameters; and carrying out inversion of the gas molecular types and concentrations according to the gas photothermal spectrum information and the calibrated gas molecular parameters.
8. The method for calculating gas composition parameters based on single optical frequency comb photo-thermal spectrum according to claim 1, wherein when the signal light is generated by a mach-zehnder interferometer, a moving distance d max of a movable arm reflection lens group in the mach-zehnder interferometer satisfies the following formula requirement in a single pulse acquisition time: Where u is the moving speed of the movable arm mirror group, n is the refractive index of the environment where the mach-zehnder interferometer is located, T is the time interval between signal light pulses, c is the light velocity in vacuum, and f rep is the repetition frequency of the optical frequency comb.
9. The method for calculating the gas composition parameters based on the single optical frequency comb photothermal spectrum according to claim 1, wherein the effective bandwidths of the two detectors with the same model are The following expressions are satisfied: Wherein, the Representing the maximum frequency of the interference optical radio frequency component produced by the mach-zehnder interferometer, v c being the longitudinal mode frequency nearest to the center of the spectrum, v B being the profile function bandwidth, The maximum frequency of the optical frequency comb optical frequency longitudinal mode is represented, u is the moving speed of the movable arm reflector group, t is the moving time, n is the refractive index of an environment medium where the Mach-Zehnder interferometer is located, and c is the light velocity in vacuum.
10. A computing system for gas composition parameters based on single optical frequency comb photothermal spectroscopy, comprising: The system comprises a database module, a detection light source module and a detection light source module, wherein the database module is used for acquiring characteristic parameters of a Mach-Zehnder interference device and frequency domain electric information of signal light, wherein the signal light is generated by the Mach-Zehnder interference device; the computing module is used for computing a down-conversion factor according to the characteristic parameters of the Mach-Zehnder interference device, carrying out inversion processing on the frequency domain electric information of the signal light and the detection light frequency domain electric information according to the down-conversion factor, and obtaining gas component parameters according to the gas photothermal spectral information; The frequency domain electric information of the signal light and the frequency domain electric information of the detection light are detected by two detectors with the same model.

Description

Gas component parameter calculation method and system based on single optical frequency comb photo-thermal spectrum Technical Field The application belongs to the technical field of laser spectrum gas sensing, and particularly relates to a gas component parameter calculation method and system based on single optical frequency comb photo-thermal spectrum. Background With the continuous development of gas sensing technology, photothermal spectroscopy technology gradually becomes an important means for trace gas sensing by virtue of the advantages of high sensitivity, zero background, low gas consumption and the like. However, the traditional photothermal spectrum generally depends on a narrow-band laser light source, so that multi-component and wide-band gas measurement is difficult to realize, and the application range of the traditional photothermal spectrum is limited. Since the beginning of this century, rapid advances in mode-locked laser technology have driven widespread use of optical frequency combs. The optical frequency comb has the characteristics of wide spectrum coverage, high frequency precision, excellent stability and the like, and provides an ideal light source for high-resolution spectrum measurement of multi-component gas. The combination of the optical frequency comb and the photothermal spectrum technology opens up a new path for detecting the broadband and multi-component gas while retaining the original advantages of the photothermal spectrum, and becomes one of the high-sensitivity and zero-background gas detection technologies which are emerging in recent years. However, existing optical frequency comb photothermal spectroscopy gas sensing schemes still have limitations, which are rooted in the relatively slow relaxation process of the gas molecules. In order to match the modulation frequency of the photo-thermal signal with the molecular relaxation process, the optical frequency is usually converted into a suitable radio frequency range by means of multi-heterodyne interference between the local oscillation optical comb and the signal optical comb when the signal light excites the photo-thermal signal. In the down conversion process, two optical frequency combs with small difference in repetition frequency are required to work together, and the down conversion factor is defined as the ratio of the repetition frequency difference to the repetition frequency. However, to realize a stable down conversion factor, the phase noise of two optical combs must be highly correlated and controlled, which greatly increases the difficulty of realization. In addition, the participation of the double optical combs not only increases the complexity of the sensing system, but also obviously increases the construction cost of the system, which forms obvious restriction on the miniaturization and industrialization development of the system. Disclosure of Invention In order to solve the problems, the application provides a gas component parameter calculation method and a gas component parameter calculation system based on single optical frequency comb photo-thermal spectrum. The first object of the present application is to provide a method for calculating gas composition parameters based on single optical frequency comb photothermal spectroscopy, comprising: acquiring characteristic parameters of the Mach-Zehnder interference device and frequency domain electrical information of signal light, wherein the signal light is generated by the Mach-Zehnder interference device; acquiring detection light frequency domain electrical information of periodically modulated detection light and signal light after absorption coupling of the gas to be detected; calculating a down-conversion factor according to the characteristic parameters of the Mach-Zehnder interference device; Inversion processing is carried out on the frequency domain electrical information of the signal light and the frequency domain electrical information of the detection light according to the down-conversion factor, so that the gas photothermal spectrum information is obtained; and obtaining gas component parameters according to the gas photothermal spectrum information. In a specific embodiment of the present application, the frequency domain electrical information and the detection light frequency domain electrical information of the signal light are obtained by performing fourier transform on time domain point information obtained by detecting two detectors with the same model. In a specific embodiment of the present application, the characteristic parameters of the mach-zehnder interference device include a moving speed of the movable arm mirror group in the mach-zehnder interference device and a refractive index of an environment where the mach-zehnder interference device is located. In a specific embodiment of the present application, the calculation formula of the down-conversion factor a 0 is as follows: a0=2nu/c Where u is the moving sp