Characteristics of photogenerated bipolar terahertz radiation in biased photoconductive switches

Abstract

The characteristics of the optically induced bipolar terahertz (THz) radiation from biased semi-insulating GaAs photoconductive switches were investigated using a free-space electrooptic sampling technique, The emitted radiation shows a nearly symmetrical waveform with a broad-band frequency spectrum spanning over 0.1-3 THz, which displays essentially no dependence on the optical excitation fluence or strength of biased field. However, it does slightly depend on the file emitter gap spacing. The dynamics of the emitted THz transient is in agreement with the optically induced ultrafast charge transport process driven by the biased field.