Fig. 1. The structure and photograph of THz instrument

Fig. 2. The optical path and photograph of the transmission module

Fig. 3. The optical path and photograph of the reflective module

Fig. 4. Terahertz time-domain and frequency-domain spectra

Fig. 5. Terahertz absorption spectrum of RDX in transmission mode

Fig. 6. Terahertz frequency-domain spectra of bottled gasoline and water