Optical fiber photo-thermal stimulated Raman spectrum detection method and system for trace gas

Abstract

The invention discloses an optical fiber photo-thermal stimulated Raman spectrum detection method and system for trace gas. A to-be-detected gas is loaded into the hollow-core optical fiber in a side surface drilling manner; pump light and the first detection light are modulated, and the light enters the hollow-core optical fiber through a coupling lens; the wavelength of the pump light is adjusted, so that the laser wavelength energy difference between the pump light and the first detection light is equal to the transition energy difference of the to-be-detected gas; the first detection light is used as stimulated Raman trigger laser, and the stimulated Raman trigger laser and periodically modulated pump light jointly excite gas to generate a stimulated Raman process, so that the phase of second detection light is influenced to change; and the second detection light forms multi-beam interference light in an FP cavity, phase signals of the interference light are demodulated through a demodulator, and the gas concentration is obtained. The phase change is detected by using an interferometry, the system has very high sensitivity, trace gas detection can be realized, the optical fiber is used for replacing limitations brought by a free space light path, a system size and the like, the application of the system is further promoted, and the development of a photo-thermal spectrum gas detection sensing technology is promoted.

Description

technical field [0001] The invention belongs to the technical field of gas detection, and relates to a detection method and system of micro-gas optical fiber photothermal stimulated Raman spectroscopy. Background technique [0002] Homonuclear diatomic molecules are diatomic molecules composed of atoms of the same nucleus, including nitrogen, oxygen, hydrogen and chlorine in the common air. Homonuclear diatomic molecules have great application potential in many fields, including metallurgy, chemistry, ceramics, fuel cells, high-temperature superconductivity and electronics industries, etc. Among them, hydrogen and chlorine are widely used, and exceeding a certain concentration will bring some disadvantages Impact. At present, some gas sensor methods, chromatography and mass spectrometry are mainly used for the detection of homonuclear diatomic molecules. Gas sensor methods are prone to aging and cross-sensitivity, and have poor stability. Chromatography and mass spectrometr...

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Problems solved by technology

At present, some gas sensor methods, chromatography and mass spectrometry are mainly used for the detection of homonuclear diatomic molecules. Gas sensor methods are prone to aging and cross-sensitivity, and have poor stability. Chromatography and mass spectrometry are relatively large and expensive. , while the chromatographic column is prone to aging, which is not conducive to long-term reliable analysis

The optical detection method based on the absorption effect is a non-destructive, high-sensitivity spectroscopic technique, but because the homonuclear diatomic molecule does not have a permanent dipole moment, the absorption effect is extremely weak, so it is impossible to realize the homonuclear diatomic molecule based on the absorption effect Molecular High Sensitivity Detection

Raman spectroscopy is a spectroscopic technique based on the Raman scattering effect, which can detect all gases except single-atom molecules, but due to the small gas scattering cross-section, the detection sensitivity is very low

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