Handheld THz-spectrometer for detection of explosive and hazardous liquids

Area of relevance: 
1 January 2008 - 31 December 2010
AG Experimentelle Halbleiterphyik, Philipps-Universität Marburg, Germany
Funded by: 
German Federal Ministry of Education and Research (BMBF), Germany


Attempts by terrorist making use of liquid explosives in the last years have urged authorities to a higher level of security in public transport. Besides uncovering weapons and other sharp metallic devices, the need for identifying possible dangerous liquids has become a high priority task. To avoid dangerous liquids passing the security check points in harmless looking bottles, so far any kind of liquids with volumes exceeding 100 ml are prohibited in the carry-on luggage. But this is by far not sufficient to meet passengers’ demands for security and comfort.

Terahertz time-domain spectroscopy is a promising technology which can potentially fill this gap. It enables authorities to distinguish between liquid explosives and non-hazardous liquids, like beverages and cosmetics, due to the characteristic THz spectra (0.1 – 1 THz). The interaction between the THz radiation and the liquid under test leads to a specific spectroscopic patterns, identifying possible threads. Our approach focuses on designing and building a portable scanner, measuring absorption and refractive index of liquids in reflection. Due to the transparency of most container materials in the THz frequency range, this can be performed without opening the bottles and within seconds. This will make airport security checks faster, safer and more reliable for both customers and authorities.