Gas Sensing Based On Wavelength Modulated Diode Laser Absorption Spectroscopy In Highly Scattering Xerogel

Sensing technology based on laser spectroscopy has valuable applications and potential research value both in traditional and rising industry. This thesis combines tunable diode laser absorption spectroscopy (TDLAS) and many photoelectric information processing technology including Wavelength Modulated Spectroscopy (WMS), Lock-in amplification, etc., to study gas absorption spectroscopy in a series of novel function materials represented by xerogel, and achieves significative results.First, on the basis of above theories and technology, this thesis integrates and builds up a quantitative measurement system which oriented by absorption spectroscopy of gas embedded in scattering media. Through utilizing it, a series of porous materials, i.e., foam, ceramic, aerogel, and xerogel, have been studied. Regarding atmosphere as the reference, the scattering ability of those materials have also been compared.Secondly, via amounts of experiments, studies in this thesis destroy the highly scattering potential of metallic oxide with distinctive micro-structure. In particular, focusing on alumina hollow-spheric xerogel, the interrelation between optical path length enhancement and physical property such as micro-structure, porosity, pore size, crystal phase, has also been discussed.Finally, applying the principle of GAs in Scattering Media Absorption Spectroscopy (GASMAS) and the multiple-pass cell, i.e., highly scattering xerogel, an in-situ compact probe has been designed and optimized, and the initial gas exchange dynamics has been tested. The SNR, resolution, sensitivity, and selectivity of sensing system may be improved owing this research.