Terahertz active and passive imaging

We describe the results of bistatic scattering measurements covering 325-650 GHz on a series of well-characterized random rough test surfaces. These have implications for active THz imagers that use coherent sources for illumination. The mean scattered intensity is compared to theoretical predictions based on an integral equation method, and the fluctuations are examined in terms of the theory for fully developed speckle. We also present a preliminary, fully passive image made using a recently developed 650 GHz, InP HEMT low-noise amplifier, and compare it to a very similar passive image made using a cryogenic (4K) hotspot microbolometer.