Computational terahertz imaging via spatio-temporal emissivity modulation

Spatial and temporal control of thermally emitted terahertz (THz) radiation could pave the way for a new family of devices in imaging, spectroscopy and communication systems. We demonstrate a computational THz imaging method enabled by a structured illumination provided by a spatio-temporal emissivity modulation. We apply a surface passivation stack composed of ZnO and Al₂O₃ layers to a high-resistivity silicon wafer to increase the effective carrier lifetime of the electron-hole pairs by a factor of 16. The emitted power is further boosted by increasing the temperature of the modulator to 390 K. Using a low power LED and a digital micromirror device we optically control the local THz emission from the modulator and use it to produce structured THz beams in a single-pixel imaging setup. We employ a ghost imaging procedure with a single-pixel detector and sequential illumination with patterns from a Hadamard basis set to allow for computational reconstruction of the object from the temporal signal. We evaluate the performance of the technique and its potential trade-offs with respect to resolution and acquisition time and apply a simple compressed sensing protocol to speed up the imaging process.