Advancements in Photomixing and Photoconductive Switching for THz Spectroscopy and Imaging

This paper reviews the design methodology and some of the applications space of standard photomixers and photoconductive switches. The methodology falls into three categories: (1) photoelectrostatics, (2) terahertz (THz) electromagnetics, and (3) laser coupling and thermal management. The applications space of ultrafast photoconductive devices, as for any device technology, is the best measure of their utility. At present photomixers are being used worldwide in at least these two instruments: (1) broadly tunable sweep oscillators for THz diagnostics, and (2) broadly tunable coherent transceivers for high-resolution THz spectroscopy. Photoconductive switches are being used in at least these two systems applications: (1) time-domain spectrometers, and (2) illuminators for THz impulse radars. Each of these applications will be addressed in turn, and some commercialization challenges facing ultrafast photoconductive devices will be addressed.