Propagation of terahertz waves in thin GaAs crystal plates

Terahertz wave propagation in thin semi-insulating GaAs plates is studied by means of timedomain terahertz spectroscopy. It is found that when terahertz radiation is focused on the edge of a crystal plate, a series of several additional pulses is detected ahead of the pulse transmitted through the plate. It is assumed the additional pulses correspond to the surface waves created by radiation reflected once or several times from the side surfaces of the plate. Additional illumination of the sample in the spectral range of impurity-related absorption weakens the terahertz radiation in the crystal, which is experimentally observed as the attenuation of additional pulses.