Multicomponent Trace Gas Detecting and Identifying System Based on MEMS-FPI on-Chip Spectral Device

Infrared spectroscopy technology can be carried out to extract the characteristic absorption frequency of gas. However, the present gas spectrum detection technology, such as tunable laser absorption spectroscopy (TDLAS), makes it difficult to balance the wide band absorption and high precision. Therefore, developing multicomponent trace gas detection technology with high integration,speed and stability has always been a researching hotspot in scientific research. In order to broaden the range of infrared laser detection, this project developed a multi-channel distributed feedback (DFB) laser with tunable central wavelengths of 1 543, 1 579, 1 626, 1 653, 1 690 and 1 742 nm as the light source. It realized the synchronous detection with a multi-wavelength infrared laser, identification of multicomponent trace gas, a high efficient filtering of background gases by making use of the MEMS-FPI on-chip device's advantages, such as narrow detecting band width (5 nm), adjustable and addressable working wavelength and efficient filtering capability. This system innovatively adopts the multi-channel wavelength modulation (WMS) technology of an addressable MEMS-FPI spectrum chip and realizes the digital acquisition of the second harmonic (2f) signal through a single phase-locked amplifier loop. The fast trace level detection of seventrace gases (methane CH4, hydrogen sulfide H2S, ethylene C2H4) has been realized (less than 2 s), which also curtailed the lower limit of multi-component identification. Compared with the direct measuring method by the traditional wide-spectrum absorption, the lower limit of detection has been declined by about 700 times. The experimental results show that the lower limit of methane detection can reach 0.2 mu L center dot L-1, and the lower limit of other gases except carbon dioxide is 10 mu L center dot L-1, while the lower limit of other gases is 1 similar to 5 mu L center dot L-1. It fully meets the application requirements of a series of trace multi-component gas detection applications, including double carbon monitoring of greenhouse gases, exhaled gas detection and diagnosis of exhaled breath.