1. Department of Optical Engineering, Beijing Institute of Technology, Beijing 100081,China 2. Department of Physics, Capital Normal University, Beijing 100037, China
Abstract：The authors present a time-resolved measurement in terahertz (THz) frequency region by means of the free-space electro-optic sampling (FSEOS). The transmission spectra and complex refractive index of four kinds of explosives were obtained. The authors found that DNT, RDX, HMX and TNT all have absorption peaks within the frequency range of 0.2 and 2.5 THz. It can be seen that DNT and HMX have obvious absorption peaks at 1.08 and 1.82 THz respectively. The authors can use the terahertz spectra as the fingerprint of the detected materials. Therefore, time-resolved terahertz spectroscopy can be applied to detect and identify explosives. The authors also detected a kind of carcinogen named azobenzene. The authors found that azobenzene bought both in China or from American all have the absorption peaks in the frequency range between 0.2 and 2.5 THz.
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