Terahertz Imaging Based on Coherent Detection of the Fourier-Space Spectrum

A novel continuous-wave THz imaging system based on the coherent recording of the Fourier space spectrum (FSS) with heterodyne detection is described. The system consists of two 300-GHz electrical multiplier-chain sources with a slight frequency offset, and a single narrow-band TeraFET detector working in raster-scanning mode. The complex-valued FSS is recorded in either the focal-plane or in the free space of the optical system in focusing and non-focusing mode, respectively. Two- and three-dimensional (2D and 3D) images are reconstructed numerically with an inverse Fourier transform algorithm. With a 80 × 80-mm² detection area and 1-mm² sampling steps, 1-mm resolution and 76.2×76.2-mm² image area are achieved.