Two-Dimensional Terahertz Imaging System Using Hot Electron Bolometer Technology

We present first results with a two-dimensional (2D) scanning terahertz passive heterodyne imaging system, currently under development. The imager is based on a phonon-cooled quasi-optically coupled hot electron bolometric (HEB) mixer integrated with an InP MMIC IF low-noise amplifier (LNA). A harmonic multiplier with an output power of about 250 piW is employed as the local oscillator (LO) source, resulting in a very compact setup. Terahertz images are obtained by scanning the target with a flat mirror mounted on a computer controlled elevation/azimuth translator. The receiver is designed to operate at 850 GHz, but can in principle operate at any terahertz frequency. We produced full 20 imagery of different objects. The demonstrated overall sensitivity of the imager in terms of a figure of merit NEAT is better than 0.5 K. We are working on extending the system into a multi pixel array configuration for faster scanning rates and improved spatial resolution.