Time-domain terahertz spectroscopy and applications on drugs and explosives

W. H. Fan; W. Zhao; G. H. Cheng; A. D. Burnett; P. C. Upadhya; J. E. Cunningham; E. H. Linfield; A. G. Davies

doi:10.1117/12.785002

4 January 2008 Time-domain terahertz spectroscopy and applications on drugs and explosives

W. H. Fan, W. Zhao, G. H. Cheng, A. D. Burnett, P. C. Upadhya, J. E. Cunningham, E. H. Linfield, A. G. Davies

Proceedings Volume 6840, Terahertz Photonics; 68400T (2008) https://doi.org/10.1117/12.785002
Event: Photonics Asia 2007, 2007, Beijing, China

Abstract

Many materials of interest to the forensic and security services, such as explosives, drugs and biological agents, exhibit characteristic spectral features in the terahertz (THz) frequency range. These spectral features originate from inter-molecular interactions, involving collective motions of molecules. Broadband THz time-domain spectroscopy (THz-TDS) system have been used to analyze a number of drugs-of-abuse and explosives that are of interest to the forensic and security services. These samples ranged from crystalline powders, pressed into pellets, to thin sheets of plastic explosives, and all being measured in transmission geometry in the frequency range 0.1 - 8 THz. To well understand the nature of the observed spectral features and the effects of thermal broadening on these far-infrared signatures, temperature-dependent THz-TDS measurements have also been performed at temperatures as low as 4 K, especially for two types of cocaine. Well-resolved low-frequency absorption peaks were observed in the frequency range 0.1 - 3 THz with high resolution. Some of absorption peaks were found clearly to become more intense and shift to higher frequencies as the temperature was reduced. The results confirm that the low-frequency collective modes are highly sensitive to the structural and spatial arrangement of molecules. Furthermore, a number of common postal packaging materials made from paper, cardboard, even several types of plastic, have been tested with drug sample to assess the ability of THz-TDS in a hostile detection environment.

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W. H. Fan, W. Zhao, G. H. Cheng, A. D. Burnett, P. C. Upadhya, J. E. Cunningham, E. H. Linfield, and A. G. Davies "Time-domain terahertz spectroscopy and applications on drugs and explosives", Proc. SPIE 6840, Terahertz Photonics, 68400T (4 January 2008); https://doi.org/10.1117/12.785002

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