We present results on the comparison of different THz technologies for the detection and identification of a variety of
explosives from our laboratory tests that were carried out in the framework of NATO SET-193 “THz technology for
stand-off detection of explosives: from laboratory spectroscopy to detection in the field” under the same controlled
conditions. Several laser-pumped pulsed broadband THz time-domain spectroscopy (TDS) systems as well as one
electronic frequency-modulated continuous wave (FMCW) device recorded THz spectra in transmission and/or
Letter bombs are an increasing problem for public authorities, companies and public persons. Nowadays every big company uses in his headquarters inspection system to check the incoming correspondence. Generally x-ray systems are used to inspect complete baskets or bags of letters. This concept which works very fine in big company with a large postal center is not usable for small companies or private persons. For an office environment with a small number of letters x-ray systems are too expensive and oversized. X-ray systems visualize the wires and electric circuits inside the envelope. If a letter contains no metallic components but hazard materials or drugs, the dangerous content is invisible for the most low-cost x-ray systems. Millimeter wave imagining systems offer the potential to close this gap.