Imaging with THz quantum cascade lasers using a Schottky diode mixer.

An imaging system in reflection geometry based on a multimode 2.9 THz quantum cascade laser as radiation source is reported. The beating between neighbouring longitudinal modes is detected using a room temperature point-contact Schottky diode as mixing element. We show that the technique can, in principle, give a dynamic range of 60 dB with a time constant of ~ 10 mus.