Fig. 1.

(a),(b) Schematic and photograph of the optical components inside the PHASR Scanner housing. (c) Boehler star covered by a diffusive scattering cloak with a fixed thickness of about 4.63 mm. Example incident (black) and reflected (blue) THz-TDS waveforms through the scattering layer are shown. (d) Image of the target formed using the extinction coefficients, $\epsilon (f)$ , at 0.53 THz without a scattering layer in the beam path (the ground truth). The radius of the red circle in the center is 2.1 mm, corresponding to an 1.11-mm spatial resolution. (e) Wavelength-normalized transport mean free path, $l_{\text{tr}}$ , of the scattering layers of 0.3 and 0.5 ${\mathrm{g/cm}}^3$ volume density. The black and magenta lines show the wavelength-normalized propagation distance of one-way (toward the target) and round-trip (back to the detector) travels through the scattering layer, respectively.