Q-switched fiber laser intra-cavity photoacoustic spectrometry gas detection system

Abstract

The invention provides a Q-switched fiber laser intra-cavity photoacoustic spectrometry gas detection system, and belongs to the technical field of fiber gas detection. The Q-switched fiber laser intra-cavity photoacoustic spectrometry gas detection system comprises a pump light source, a rare earth doped fiber, a Q switch and the like, wherein a ring cavity of a pulse fiber laser is composed of a wavelength division multiplexer, the rare earth doped fiber, an optical isolator, a gas chamber, the Q switch and an optical fiber coupler, and an input coupling mirror and an output coupling mirror are placed in the gas chamber; a quartz tuning fork is placed in the gas chamber and used for detecting sound wave signals, and pulse laser light in the cavity of the fiber laser excites gas to produce the sound wave signals; the signals detected by the quartz tuning fork is extracted by a phase locking amplifier further, and then is obtained and transmitted to a computer through a data acquisition card, and gas concentration information is obtained after gas concentration inversion is conducted. By combining the fiber laser technology and the photoacoustic spectrometry gas detection technology, the Q-switched fiber laser intra-cavity photoacoustic spectrometry gas detection system has the advantages of having high sensitivity, higher cost performance, low cost and the like.

Description

technical field [0001] The invention relates to an intracavity photoacoustic gas detection system of a Q-switched fiber laser, in particular to an inner cavity gas detection system based on photoacoustic gas detection technology, which belongs to the technical field of optical fiber gas detection. technical background [0002] In the process of industrial production, qualitative or even quantitative analysis of certain gases is often required to ensure production safety. For some trace gases, high-sensitivity gas detection devices are required. At present, the commonly used gas detection methods mainly include electrochemical methods, infrared spectroscopy, and gas chromatography. Among them, infrared spectroscopy has always attracted much attention, and its key technologies include direct Spectral absorption technology, differential absorption technology, differential absorption technology based on wavelength scanning, harmonic detection technology, intracavity spectral abs...

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Problems solved by technology

The traditional absorption technology has a limited detection sensitivity due to the limited effective absorption path of gas; the intracavity spectral absorption technology places the gas chamber in the resonant cavity of the fiber laser, and uses the laser to and fro to greatly increase the effective absorption path of the gas. However, this technology still relies on wavelength scanning technology, which needs to extract extremely weak effective signals in strong background noise, which limits the improvement of detection sensitivity; photoacoustic spectroscopy detection technology directly measures the light energy absorbed by gas, which can detect extremely weak absorption , has high sensitivity, but the existing research is based on the laser coupled out of the finished laser as the excitation light source, and a large part of the light energy is lost in the coupling process

[0003] "China Laser", 2009, Volume 36, Issue 9, Pages 2384-2387, the authors are Jia Dagong, Liu Kun, Jing Wencai, Wang Yan, Zhang Hongxia, Zhang Yimo, entitled "Gas Detection Method Based on Ring Cavity Fiber Laser" This article proposes a gas detection system based on the design of the fiber laser cavity. The system uses wavelength scanning technology to make the output wavelength of the fiber laser cover multiple gas absorption peaks. Compared with the use of a single absorption peak, this method has improved detection sensitivity and accuracy. However, direct spectral absorption based on wavelength scanning technology itself has the defect of low sensitivity, and the traditional gas chamber is not able to increase the effective absorption of light. Generally, its size will not be too small, which will cause the disadvantage of large volume when forming products in the future

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