THz Fourier Imaging Based on Sub-harmonic Heterodyne Detection

A high-resolution THz imaging system based on the coherent recording of the Fourier space spectrum by sub-har-monic heterodyne detection is described. The 600-GHz imaging wave and the 300-GHz reference wave, locked to each other with a slight frequency offset, are received by a broad-band Si CMOS TeraFET mixer. The complex-valued Fourier space spectrum is recorded in the focal plane of the imaging system in raster-scanning mode, after which the imaged scene is reconstructed by inverse Fourier transformation. This allows the system to work in the virtual imaging regime and brings the theoretical resolution limit of the system to the level of half the imaging wavelength.