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Keywords = transmitted or reflected THz pulse with a few cycles

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17 pages, 3398 KB  
Article
Essential Limitations of the Standard THz TDS Method for Substance Detection and Identification and a Way of Overcoming Them
by Vyacheslav A. Trofimov and Svetlana A. Varentsova
Sensors 2016, 16(4), 502; https://doi.org/10.3390/s16040502 - 8 Apr 2016
Cited by 28 | Viewed by 6575
Abstract
Low efficiency of the standard THz TDS method of the detection and identification of substances based on a comparison of the spectrum for the signal under investigation with a standard signal spectrum is demonstrated using the physical experiments conducted under real conditions with [...] Read more.
Low efficiency of the standard THz TDS method of the detection and identification of substances based on a comparison of the spectrum for the signal under investigation with a standard signal spectrum is demonstrated using the physical experiments conducted under real conditions with a thick paper bag as well as with Si-based semiconductors under laboratory conditions. In fact, standard THz spectroscopy leads to false detection of hazardous substances in neutral samples, which do not contain them. This disadvantage of the THz TDS method can be overcome by using time-dependent THz pulse spectrum analysis. For a quality assessment of the standard substance spectral features presence in the signal under analysis, one may use time-dependent integral correlation criteria. Full article
(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)
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30 pages, 1472 KB  
Article
An Effective Method for Substance Detection Using the Broad Spectrum THz Signal: A "Terahertz Nose"
by Vyacheslav A. Trofimov and Svetlana A. Varentsova
Sensors 2015, 15(6), 12103-12132; https://doi.org/10.3390/s150612103 - 25 May 2015
Cited by 38 | Viewed by 6947
Abstract
We propose an effective method for the detection and identification of dangerous substances by using the broadband THz pulse. This pulse excites, for example, many vibrational or rotational energy levels of molecules simultaneously. By analyzing the time-dependent spectrum of the THz pulse transmitted [...] Read more.
We propose an effective method for the detection and identification of dangerous substances by using the broadband THz pulse. This pulse excites, for example, many vibrational or rotational energy levels of molecules simultaneously. By analyzing the time-dependent spectrum of the THz pulse transmitted through or reflected from a substance, we follow the average response spectrum dynamics. Comparing the absorption and emission spectrum dynamics of a substance under analysis with the corresponding data for a standard substance, one can detect and identify the substance under real conditions taking into account the influence of packing material, water vapor and substance surface. For quality assessment of the standard substance detection in the signal under analysis, we propose time-dependent integral correlation criteria. Restrictions of usually used detection and identification methods, based on a comparison between the absorption frequencies of a substance under analysis and a standard substance, are demonstrated using a physical experiment with paper napkins. Full article
(This article belongs to the Section Physical Sensors)
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