Fig. 1.

Experimental characterization of gelatin-embedded human brain gliomas: (a) a reflection-mode THz spectroscopy unit, based on off-axis gold-coated parabolic mirrors and a reference window, on the top of which the tissue sample is handled; (b), (c) reference $E_{\mathrm{r}}$ and sample $E_{\mathrm{s}}$ signals of the THz-pulsed spectrometer, represented in the frequency and time domains, respectively. In (a), the angle of THz wave incidence on the quartz window–tissue (or free space) interface is $\theta \simeq 17\mathrm{deg}$.