We have shown recently that unique optical signatures can be observed with the measurement of ultrashort middle infrared laser pulses that have been transmitted through molecular vapors. Here, we report on an increased signal-to-noise ratio of the pulse measurements by using a cross-correlation technique with a lockin amplifier. Carbon tetrafluoride and dimethyl methylphosphonate (DMMP) cross-correlation signatures are highly discriminated using principal component analysis. A squared exponential Gaussian process regression model is used to quantitatively predict the concentration of DMMP.
William Conner Thomas, Craig A. Zuhlke, and Dennis R. Alexander, "A new modality for the detection of chemical vapors using middle infrared femtosecond pulse propagation effects," Proc. SPIE 11010, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XX, 110100X (Presented at SPIE Defense + Commercial Sensing: April 16, 2019; Published: 17 May 2019); https://doi.org/10.1117/12.2520793.
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