Role of the pulse duration at measurements of spectral signatures of substances in THz range of frequencies

THz TDS is one of tools, which can be effective for the security problem solution. As a rule, the detection and identification of substance is based on the spectral fingerprints: absorption frequencies of substance. To detect the substance, it is necessary to compare its absorption frequencies with those from database which contains the absorption frequencies of various substance. Therefore, a role of this data is one of the keys for the problem solution. As follows from analysis of papers, the measurements of the absorption frequencies were provided by using broadband THz pulse. Due to essential non-stationary response of a medium as well as broadband spectrum of the THz pulse, in the spectrum of pulse, transmitted through a substance, many additional frequencies appear. Among them maybe appear “false” absorption frequencies, appearance of which is caused by frequency conversion processes, as well as the frequencies, corresponding to a substance emission because of a high energy levels excitation due to the cascade mechanism. Both these mechanisms of the spectrum transformation strongly depend on the incident pulse duration. Another additional factor resulting in observing of the false absorption frequencies is disordered (or ordered) packing for the substance. In THz range of frequencies, the most part of the packing is a disordered photonic structure and developing of the strategy to avoid its influence on the efficiency of detection and identification of substance is a key problem. We discuss once more approach for solving this problem in this paper.

[1]  Gintaras Valušis,et al.  Non-destructive inspection of food and technical oils by terahertz spectroscopy , 2018, Scientific Reports.

[2]  Michael Watkinson,et al.  Terahertz spectroscopy: a powerful new tool for the chemical sciences? , 2012, Chemical Society reviews.

[3]  H. Hübers,et al.  Surface roughness effects on the terahertz reflectance of pure explosive materials , 2008 .

[4]  Norbert Palka,et al.  Identification of concealed materials, including explosives, by terahertz reflection spectroscopy , 2013 .

[5]  Salih Ergün,et al.  Terahertz Technology For Military Applications , 2015 .

[6]  A. Davies,et al.  Terahertz spectroscopy of explosives and drugs , 2008 .

[7]  Arthur D. van Rheenen,et al.  Robust Identification of Concealed Dangerous Substances by Spectral Correlation of Terahertz Transmission Images , 2015, IEEE Transactions on Terahertz Science and Technology.

[8]  Edward P J Parrott,et al.  A study into the effect of subtle structural details and disorder on the terahertz spectrum of crystalline benzoic acid. , 2010, Physical chemistry chemical physics : PCCP.

[9]  Svetlana A. Varentsova,et al.  An Effective Method for Substance Detection Using the Broad Spectrum THz Signal: A “Terahertz Nose” , 2015, Sensors.

[10]  Chiko Otani,et al.  Non-invasive mail inspection system with terahertz radiation , 2009, Defense + Commercial Sensing.

[11]  Kazuhiko Fujiwara,et al.  Terahertz spectra of 1-cyanoadamantane in the orientationally ordered and disordered phases , 2014 .

[12]  G. Bastiaans,et al.  Absorption coefficients of selected explosives and related compounds in the range of 0.1-2.8 THz. , 2007, Optics express.

[13]  M. J. Fitch,et al.  Wideband terahertz spectroscopy of explosives , 2007 .

[14]  Yan Zhang,et al.  Detection and identification of illicit drugs using terahertz imaging , 2006 .

[15]  Irina G. Zakharova,et al.  High Energy Level Excitation of Molecules due to Cascade Mechanism of Broadband THz Pulse Energy Absorption , 2015 .

[16]  Norbert Palka,et al.  Quantitative Analysis of Hexahydro-1,3,5-trinitro-1,3,5, Triazine/Pentaerythritol Tetranitrate (RDX–PETN) Mixtures by Terahertz Time Domain Spectroscopy , 2015, Applied spectroscopy.

[17]  Soohyun Kim,et al.  Compound Explosives Detection and Component Analysis via Terahertz Time-Domain Spectroscopy , 2013 .

[18]  Elizabeth J. Slingerland,et al.  Atmospheric absorption of terahertz radiation and water vapor continuum effects , 2013 .

[19]  Seiji Kojima,et al.  Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials , 2014 .

[20]  Arthur D. van Rheenen,et al.  Detection and identification of explosives hidden under barrier materials: what are the THz-technology challenges? , 2011, Defense + Commercial Sensing.

[21]  Kodo Kawase,et al.  Terahertz Imaging System for Medical Applications and Related High Efficiency Terahertz Devices , 2014 .

[22]  Svetlana A. Varentsova,et al.  Essential Limitations of the Standard THz TDS Method for Substance Detection and Identification and a Way of Overcoming Them , 2016, Sensors.

[23]  Hua Zhong,et al.  Terahertz Spectroscopy and Imaging for Defense and Security Applications , 2007, Proceedings of the IEEE.

[24]  Scott Schecklman,et al.  Terahertz material detection from diffuse surface scattering , 2011 .

[25]  K. Kawase,et al.  Non-destructive drug inspection in covering materials using a terahertz spectral imaging system with injection-seeded terahertz parametric generation and detection. , 2016, Optics express.

[26]  Vyacheslav A. Trofimov,et al.  False detection of dangerous and neutral substances in commonly used materials by means of the standard THz Time Domain Spectroscopy , 2016 .

[27]  P. Sun,et al.  Numerical method based on transfer function for eliminating water vapor noise from terahertz spectra. , 2017, Applied optics.

[28]  Yan Zhang,et al.  Terahertz absorbance spectrum fitting method for quantitative detection of concealed contraband , 2007 .

[29]  Svetlana A. Varentsova,et al.  Substance identification by pulsed THz spectroscopy in the presence of disordered structure , 2017, Optical Engineering + Applications.

[30]  H. Wu,et al.  THz spectroscopy: An emerging technology for pharmaceutical development and pharmaceutical Process Analytical Technology (PAT) applications , 2012 .

[31]  R. Kosloff,et al.  Direct MD Simulations of Terahertz Absorption and 2D Spectroscopy Applied to Explosive Crystals. , 2014, The journal of physical chemistry letters.

[32]  Gintaras Valušis,et al.  Terahertz spectroscopic identification of explosive and drug simulants concealed by various hiding techniques. , 2015, Applied optics.

[33]  K. Kawase,et al.  THz imaging techniques for nondestructive inspections , 2010 .

[34]  Kyung Ik Sim,et al.  Reflection terahertz time-domain spectroscopy of RDX and HMX explosives , 2014 .

[35]  D. Zimdars,et al.  Terahertz imaging: Revealing hidden defects , 2009 .

[36]  Vyacheslav A. Trofimov,et al.  Spectral properties of optical pulse, containing a few cycles, reflected from or passed through disordered layered structure , 2016, SPIE Photonics Europe.

[37]  Svetlana A. Varentsova,et al.  New Possibilities of Substance Identification Based on THz Time Domain Spectroscopy Using a Cascade Mechanism of High Energy Level Excitation , 2017, Sensors.

[38]  Irina G. Zakharova,et al.  New Possibilities of Substance Identification Based on THz TDS Using Cascade Mechanism of High Energy Level Excitation , 2017 .

[39]  M. C. Kemp,et al.  Explosives Detection by Terahertz Spectroscopy—A Bridge Too Far? , 2011, IEEE Transactions on Terahertz Science and Technology.

[40]  William Jones,et al.  Testing the Sensitivity of Terahertz Spectroscopy to Changes in Molecular and Supramolecular Structure: A Study of Structurally Similar Cocrystals , 2009 .

[41]  C. Otani,et al.  Noninvasive Mail Inspection System with Terahertz Radiation , 2009, Applied spectroscopy.

[42]  Chiko Otani,et al.  THz-Wave Spectroscopy Applied to the Detection of Illicit Drugs in Mail , 2007, Proceedings of the IEEE.