Broadband terahertz time-domain spectroscopy and fast FMCW imaging: principle and applications

Abstract: We report a broadband terahertz time-domain spectroscopy (THz-TDS) which enables twenty vibrational modes of adenosine nucleoside to be resolved in a wide frequency range of 1-20 THz. The observed spectroscopic features of adenosine are in good agreement with the published spectra obtained using Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. This much-extended bandwidth leads to enhanced material characterization capability as it provides spectroscopic information on both intra-molecular and inter-molecular vibrations. In addition, we also report a low-cost Frequency Modulation Continuous Wave (FMCW) imaging system which has a fast measurement speed of 40,000 waveforms per second. Cross-sectional imaging capability through cardboard has also been demonstrated using its excellent penetration capability at a frequency range of 76-81 GHz. We anticipate that the integration of these two complementary imaging technologies would be highly desirable for many real-world applications because it provides both spectroscopic discrimination and penetration capabilities in a single instrument.